Fuel injection valve

The present invention relates to a fuel injection valve mounted on an internal combustion engine and injecting fuel for combustion from an injection hole.

In order to accurately control the output torque and emission state of the internal combustion engine, it is important to accurately control the injection state such as the injection start timing and injection amount of the fuel injected from the fuel injection valve. Therefore, conventionally, a technique for detecting an actual injection state by detecting a fuel pressure that fluctuates with injection has been proposed. For example, the actual injection start time can be detected by detecting the time when the fuel pressure starts to decrease with the start of injection, or the actual injection end time can be detected by detecting the time when the fuel pressure stops rising with the end of injection. It is detected (see Patent Document 1).

In detecting such fluctuations in fuel pressure, the fuel pressure sensor (rail pressure sensor) installed directly on the common rail (accumulation container) buffers the fuel pressure fluctuations caused by injection in the common rail, so that the fuel pressure is accurate. Fluctuations cannot be detected. Therefore, in the invention described in Patent Document 1, by mounting a fuel pressure sensor on the fuel injection valve, it is attempted to detect the fuel pressure fluctuation before the fuel pressure fluctuation generated by the injection is buffered in the common rail.

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2008-144749</text></patcit></p>

<p> The fuel injection valve is generally configured by accommodating a needle for opening and closing the injection hole, an actuator for driving the needle, and the like in a body having a high-pressure passage for flowing high-pressure fuel to the injection hole. Is. Then, the present inventors examined attaching a fuel pressure sensor having the following configuration to the body. That is, a strain-causing body that is attached to the body and elastically deforms under the pressure of high-pressure fuel, a sensor element that converts the magnitude of strain generated by the strain-causing body into an electric signal, and a detection signal of the sensor element. On the other hand, a fuel pressure sensor is configured from a signal processing circuit that performs amplification processing and the like.</p><p> By the way, before shipping the injector to the market, it is necessary to carry out various tests and inspections on the fuel pressure sensor. Hereinafter, specific examples of the test and inspection will be described.</p><p> The higher the fuel temperature, the larger the thermal expansion deformation of the strain-causing body, so the output value of the fuel pressure sensor (that is, the sensor output value output from the signal processing circuit) drifts. Therefore, it is necessary to calculate the fuel pressure from the sensor output value in consideration of this temperature drift amount. Since the temperature drift amount is an eigenvalue different for each strain-causing body, it is necessary to test (temperature characteristic test) the temperature drift amount before shipping the fuel injection valve to the market.</p><p> Therefore, with the strain generating body, the sensor element, and the signal processing circuit assembled to the body, fuel having a known test temperature and test pressure is supplied to the high pressure passage of the body, and the fuel pressure is applied to the strain generating body. Then, the temperature drift amount for each test temperature is acquired based on the sensor output value, the test pressure, and the test temperature at that time. In addition, an abnormality inspection of the fuel pressure sensor is carried out by checking whether the sensor output value with respect to the test pressure is out of the normal range.</p><p> However, when the strain-causing body is assembled to the body, it is necessary to stabilize the temperature of the body as well as the strain-causing body to the test temperature. However, since the body has a large temperature mass, the temperature is adjusted so as to stabilize at the test temperature. It takes time to do. Further, if an abnormality is detected by the above-mentioned abnormality inspection with the fuel pressure sensor assembled on the body, the fuel injection valve must be treated as an abnormal product, which causes a decrease in the manufacturing yield of the fuel injection valve.</p><p> The present invention has been made to solve the above problems, and an object of the present invention is to improve the workability of various test inspections on a sensor in a fuel injection valve provided with a sensor for detecting the fuel pressure, and to improve the workability of the fuel injection valve. The purpose of the present invention is to provide a fuel injection valve that suppresses a decrease in manufacturing yield.</p>

<p> Hereinafter, means for solving the above problems and their actions and effects will be described.</p><p> The invention according to claim 1 is a fuel injection valve mounted on an internal combustion engine that injects fuel from a injection hole, and is attached to the body and a body that internally forms a high-pressure passage for flowing high-pressure fuel to the injection hole. A strain-causing body that elastically deforms under the pressure of the high-pressure fuel, a sensor element that is attached to the strain-causing body and converts the magnitude of strain generated by the strain-causing body into an electric signal, and the sensor element. It is provided with a signal processing circuit that performs at least amplification processing on the detected signal of. Then, the strain-causing body, the sensor element, and the signal processing circuit form a unitized fuel pressure detection unit that is integrally assembled, and a screw portion formed on the strain-causing body is screwed to the body. As a result, the fuel pressure detection unit is attached to the body.</p><p> For example, contrary to the present invention, if the strain generator and the signal processing circuit are separately attached to the body, the sensor output value output from the signal processing circuit unless the strain generator and the signal processing circuit are attached to the body. Therefore, various tests and inspections such as the above-mentioned temperature characteristic test and abnormality inspection cannot be performed. On the other hand, according to the present invention, the strain-causing body, the sensor element, and the signal processing circuit are integrally assembled to form a unit, and the fuel pressure detection unit is attached to the body by screwing the strain-causing body to the body. Various tests and inspections can be carried out with the fuel pressure detection unit alone before attaching to the body.</p><p> In particular, when carrying out the above-mentioned temperature characteristic test, according to the present invention, it is not necessary to adjust the body having a large temperature mass to the test temperature together with the strain-causing body, and only the strain-causing body is stable at the test temperature. Since the temperature may be adjusted so that the temperature is adjusted, the time required for the temperature adjustment can be shortened. Therefore, the workability of the temperature characteristic test can be improved.</p><p> Further, when the above-mentioned abnormality inspection is carried out, according to the present invention, the abnormality inspection can be carried out by the fuel pressure detection unit alone, so that the abnormality of the sensor output value can be detected before the fuel pressure detection unit is attached to the body. Therefore, it is possible to suppress a decrease in the manufacturing yield of the fuel injection valve.</p><p> In the invention according to claim 2, the strain-causing body has a sensor-side sealing surface that metal-touch seals between the body and the body by being pressed against the body and brought into close contact with the body, and the fastening force of the screw portion. Therefore, the sensor-side sealing surface is pressed against the body.</p><p> According to this, the screw part for assembling the fuel pressure detection unit to the body and the screw part for generating the axial force for generating the force (axial force) for pressing the sensor side seal surface against the body are shared. Be made. Therefore, the physique of the fuel injection valve can be reduced as compared with the case where both screw portions are formed separately, the number of operations for fastening the screws can be reduced, and the productivity of the fuel injection valve can be improved.</p><p> In the invention according to claim 3, the strain-causing body is formed in a bottomed cylindrical shape in which an inflow port for flowing the high-pressure fuel into the inside is formed, and the strain-generating body is a cylinder located around the inflow port. The sensor side sealing surface is formed at the end portion. According to this, since the cylindrical end portion forming the inflow port is used as the sensor-side sealing surface, the strain-causing body can be miniaturized.</p><p> The invention according to claim 4 is characterized in that the fuel pressure detection unit has a holding member that is assembled to the strain generating body and holds the signal processing circuit.</p><p> For example, contrary to the above invention, if the strain generating body is to hold the signal processing circuit, a holding portion for installing the signal processing circuit must be formed in the strain generating body, which increases the size of the strain generating body. Invite. The strain-causing body is required to have a material having a small coefficient of thermal expansion and a high-strength material capable of withstanding high-pressure fuel in order to improve the detection accuracy of the fuel pressure. Therefore, the material cost of the strain-causing body is high, and if the holding portion is formed on such a strain-causing body to increase the size, a large cost increase will occur.</p><p> According to the above invention in view of this point, since a holding member different from the strain generating body is assembled to the strain generating body and the holding member holds the signal processing circuit, the cost is increased due to the increase in size of the strain generating body. Can be avoided.</p><p> In the invention according to claim 5, the holding member is assembled to the strain-causing body in a non-rotatable state, and the holding member is formed with a tool engaging portion for engaging a rotary tightening tool. It is characterized by.</p><p> When screwing a strain-causing body to a body using a rotary tightening tool, the larger the radius of gyration of the tool engaging portion with which the tool is engaged, the smaller the force required for tightening and the better the workability of tightening. However, contrary to the above invention, when a tool engaging portion for tool engagement is formed on the strain generating body, if an attempt is made to increase the radius of gyration, the strain generating and straining body having an expensive material cost becomes large as described above. , Invites cost increase.</p><p> According to the above invention in view of this point, since the tool engaging portion for engaging the tool is formed on the holding member different from the strain generating body, it is possible to avoid an increase in cost due to the increase in size of the strain generating body. Further, since the holding member also serves as the holding of the signal processing circuit and the tool engagement, the fuel pressure detection unit can be miniaturized.</p><p> In the invention according to claim 6, an insertion hole into which the strain-causing body is inserted is formed in the holding member, and the strain-causing body is press-fitted into the insertion hole so that the holding member is the strain-causing body. It is characterized in that it is assembled in a non-rotatable state. Therefore, it is possible to easily assemble the holding member with respect to the strain-causing body in a non-rotatable state with a simple configuration.</p><p> In the invention according to claim 7, the strain-causing body is formed in a bottomed cylindrical shape in which an inflow port for flowing the high-pressure fuel into the inside is formed, and the sensor element is attached to the cylindrical bottom portion of the strain-causing body. The holding member is configured to have an accommodating portion for accommodating the signal processing circuit, and the cylindrical portion of the strain-causing body is inserted into an insertion hole formed in the accommodating portion. , The diaphragm is arranged inside the accommodating portion.</p><p> As a result, the accommodating portion accommodating the signal processing circuit also serves as the accommodating portion accommodating the sensor element, so that the fuel pressure detection unit can be miniaturized as compared with the case where the accommodating portion is provided separately.</p><p> In the invention according to claim 8, the strain-causing body is formed in a bottomed cylindrical shape in which an inflow port for flowing the high-pressure fuel into the inside is formed, and the sensor element is attached to the cylindrical bottom portion of the strain-causing body. It functions as a diaphragm portion to be formed, and is characterized in that the screw portion is formed on the outer peripheral surface of the cylindrical portion of the strain-causing body. According to this, since the cylindrical portion for guiding the high-pressure fuel from the inflow port to the diaphragm portion is used as a portion forming the screw portion, the strain-causing body can be miniaturized.</p>

<figref num="1">The schematic cross-sectional view which shows the schematic internal structure of the injector which concerns on 1st Embodiment of this invention.</figref><figref num="2">Enlarged view of the fuel pressure sensor part of the injector in Fig. 1.</figref><figref num="3">Sectional view of the fuel pressure detection unit removed from the injector of FIG.</figref><figref num="4">In the first embodiment, an exploded perspective view showing a housing unit and a stem unit.</figref><figref num="5">It is a figure which shows the state which the housing is attached to the stem, (a) is the figure which shows the 1st Embodiment, (b) (c) is the figure which shows the 2nd Embodiment.</figref><figref num="6">In the third embodiment of the present invention, a state in which the housing is welded and fixed to the stem is shown.</figref>

Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. In each of the following embodiments, parts that are the same or equal to each other are designated by the same reference numerals in the drawings, and the description thereof will be incorporated for the parts having the same reference numerals.

(First Embodiment) The first embodiment of the present invention will be described with reference to FIGS. 1 to 4 and 5 (a). FIG. 1 is a schematic cross-sectional view showing a schematic internal configuration of an injector (fuel injection valve) according to the present embodiment. First, the basic configuration and operation of the injector will be described based on FIG.

The injector injects high-pressure fuel stored in a common rail (accumulation container) (not shown) into the combustion chamber E1 formed in the cylinder of a diesel internal combustion engine. Nozzle 1 for injecting fuel when the valve is opened, electric power It includes an electric actuator 2 (driving means) that is supplied and driven, and a back pressure control mechanism 3 that is driven by the electric actuator 2 to control the back pressure of the nozzle 1.

The nozzle 1 includes a nozzle body 12 on which the nozzle hole 11 is formed, a needle 13 that is brought into contact with and separated from the valve seat of the nozzle body 12 to open and close the nozzle hole 11, and a spring 14 that urges the needle 13 in a valve closing direction.

The electric actuator 2 employs a piezo actuator composed of a laminated body (piezo stack) in which a large number of piezo elements are laminated, and by switching between charging and discharging the piezo elements, the expansion state and the reduction state can be obtained. Is switched. As a result, the piezo stack functions as an actuator for operating the needle 13. Instead of the piezo actuator, an electromagnetic actuator composed of a stator and an armature may be adopted.

Inside the valve body 31 of the back pressure control mechanism 3, a piston 32 that moves following the expansion and contraction of the piezo actuator 2, a disc spring 33 that urges the piston 32 toward the piezo actuator 2, and a piston 32 drive the piston 32. The spherical valve body 34 is housed.

The substantially cylindrical injector body 4 is formed with a stepped columnar storage hole 41 extending in the direction of the injector axis (vertical direction in FIG. 1) at the center in the radial direction, and the piezo actuator 2 is formed in this storage hole 41. And the back pressure control mechanism 3 are housed. Further, the nozzle 1 is held at the end of the injector body 4 by screwing the substantially cylindrical retainer 5 into the injector body 4.

The nozzle body 12, the injector body 4, and the valve body 31 are formed with a high-pressure passage 6 in which high-pressure fuel is always supplied from the common rail, and a low-pressure passage 7 connected to a fuel tank (not shown). In addition, these bodies 12, 4, and 31 are made of metal and are strengthened by quenching, and the surface is hardened by carburizing (or carburizing and nitriding). There is.

These bodies 12, 4, and 31 are inserted and arranged in the insertion holes E3 formed in the cylinder head E2 of the internal combustion engine. The injector body 4 is formed with an engaging portion 42 that engages with one end of the clamp K, and by bolting the other end of the clamp K to the cylinder head E2, one end of the clamp K inserts the engaging portion 42. It will be pressed toward hole E3. As a result, the injector is fixed in the state of being pressed into the insertion hole E3.

A high-pressure chamber 15 that is a part of the high-pressure passage 6 is formed between the outer peripheral surface of the needle 13 on the injection hole 11 side and the inner peripheral surface of the nozzle body 12. The high pressure chamber 15 communicates with the injection hole 11 when the needle 13 is displaced in the valve opening direction. A back pressure chamber 16 is formed on the anti-injection hole side of the needle 13. The above-mentioned spring 14 is arranged in the back pressure chamber 16.

In the valve body 31, a high-pressure seat surface 35 is formed in the path for communicating the high-pressure passage 6 in the valve body 31 and the back pressure chamber 16 of the nozzle 1, and the low-pressure passage 7 in the valve body 31 and the back of the nozzle 1 are formed. A low-pressure seat surface 36 is formed in the path communicating with the pressure chamber 16. The valve body 34 described above is arranged between the high-pressure seat surface 35 and the low-pressure seat surface 36.

The injector body 4 is formed with a high-pressure port 43 (high-pressure pipe connection portion) connected to a high-pressure pipe (not shown) and a low-pressure port 44 (low-pressure pipe connection portion) connected to a low-pressure pipe (not shown). The fuel supplied from the common rail to the high-pressure port 43 through the high-pressure pipe is supplied from the outer peripheral surface side of the cylindrical injector body 4. The fuel supplied to the injector flows into the high pressure chamber 15 and the back pressure chamber 16 through the high pressure passage 6.

The high-pressure passage 6 is formed with a branch passage 6a that branches to the anti-injection hole side of the injector body 4. Through this branch passage 6a, the fuel in the high pressure passage 6 is introduced into the fuel pressure sensor 50, which will be described later.

A connector 60 is attached to the upper part of the injector body 4 on the anti-injection hole side. The electric power supplied from the outside to the terminal of the connector 60 (drive connector terminal 62) is supplied to the piezo actuator 2 via the lead wire 21, whereby the piezo actuator 2 expands and contracts when the power supply is stopped.

In the above configuration, when the piezo actuator 2 is reduced, the valve body 34 is in contact with the low pressure seat surface 36, the back pressure chamber 16 is connected to the high pressure aisle 6, and the back pressure chamber 16 has a high pressure. Fuel pressure is introduced. Then, the needle 13 is urged in the valve closing direction by the fuel pressure in the back pressure chamber 16 and the spring 14, and the injection hole 11 is closed.

On the other hand, when a voltage is applied to the piezo actuator 2 and the piezo actuator 2 is extended, the valve body 34 is in contact with the high pressure seat surface 35, the back pressure chamber 16 is connected to the low pressure passage 7, and the pressure inside the back pressure chamber 16 is low. become. Then, the needle 13 is urged toward valve opening by the fuel pressure in the high-pressure chamber 15 to open the injection hole 11, and fuel is injected from the injection hole 11 into the combustion chamber E1.

Here, the pressure of the high-pressure fuel in the high-pressure passage 6 fluctuates as the fuel is injected from the injection hole 11. A fuel pressure sensor 50 that detects this pressure fluctuation is attached to the injector body 4. In the pressure fluctuation waveform detected by the fuel pressure sensor 50, the actual injection start time can be detected by detecting the time when the fuel pressure starts to decrease with the start of injection from the injection hole 11. Further, the actual injection end time can be detected by detecting the time when the fuel pressure starts to rise with the end of the injection. Further, the injection amount can be detected by detecting the maximum value of the fuel pressure drop amount generated by the injection in addition to the injection start timing and the injection end timing.

Next, the single structure of the fuel pressure sensor 50 and the mounting structure of the fuel pressure sensor 50 to the injector body 4 will be described with reference to FIGS. 2 and 3 and the like. Note that FIG. 2 is an enlarged view of FIG. 1, and FIG. 3 is a cross-sectional view showing a portion of the fuel pressure detection unit in FIG.

The fuel pressure sensor 50 converts the magnitude of strain generated in the stem 51 (distortion body) elastically deformed by receiving the pressure of the high-pressure fuel in the branch passage 6a into an electric signal and uses it as a pressure detection value. It is configured to include a strain gauge (sensor element) 52 for output.

The stem 51 includes a cylindrical cylindrical portion 51b having an inflow port 51a for introducing high-pressure fuel inside at one end, and a disk-shaped diaphragm portion 51c that closes the other end of the cylindrical portion 51b. ing. The pressure of the high-pressure fuel flowing into the cylindrical portion 51b from the inflow port 51a is received by the inner surface of the cylindrical portion 51b and the diaphragm portion 51c, whereby the entire stem 51 is elastically deformed.

The stem 51 is made of metal, and the metal material has high strength and high hardness due to being subjected to ultra-high pressure, and there is little deformation due to thermal expansion and the influence on the strain gauge 52 is small (that is, a low coefficient of thermal expansion). Specifically, Fe, Ni, Co or Fe, Ni is the main component, and Ti, Nb, Al or Ti, Nb is added as the precipitation strengthening material, and the material is pressed. , Can be formed by cutting or cold forging. Further, a material to which C, Si, Mn, P, S and the like are added may be selected.

A recess 45 into which the cylindrical portion 51b of the stem 51 is inserted is formed on the end surface of the cylindrical injector body 4 on the anti-injection hole side. A female screw portion 45a (body side screw portion) is formed on the inner peripheral surface of the recess 45, and a male screw portion 51d (sensor side screw portion) is formed on the outer peripheral surface of the cylindrical portion 51b. Then, the fuel pressure sensor 50 is attached to the injector body 4 by screwing the male screw portion 51d of the stem 51 to the female screw portion 45a of the injector body 4.

A sensor-side sealing surface 51e is formed on the cylindrical end surface located around the inflow port 51a of the cylindrical portion 51b, and a body-side sealing surface 45b is formed on the bottom surface of the recess 45. Both sealing surfaces 51e and 45b are surfaces that extend perpendicularly to the axial direction of the stem 51 (vertical direction in FIG. 2), and have a shape extending in an annular shape around the inflow port 51a.

Then, by pressing the sensor-side sealing surface 51e against the body-side sealing surface 45b to bring them into close contact with each other, the injector body 4 and the stem 51 are configured to be metal-touch-sealed. The force (axial force) that presses both sealing surfaces 51e and 45b is generated by screwing the stem 51 to the injector body 4. That is, the stem 51 is attached to the injector body 4 and the axial force is generated at the same time.

The strain gauge 52 is attached to the diaphragm portion 51c. More specifically, the strain gauge 52 is sealed (baked) by the glass member 52b in a state of being arranged on the diaphragm portion 51c and fixed. Therefore, when the stem 51 is elastically deformed so as to expand due to the pressure of the high-pressure fuel flowing into the cylindrical portion 51b, the strain gauge 52 detects the magnitude of the strain (elastic deformation amount) generated in the diaphragm portion 51c. ..

A metal housing 53 (holding member) is attached to the stem 51. The housing 53 includes an IC holding portion 53a (accommodating portion), a press-fitting portion 53c, and a tool engaging portion 53d (accommodating portion) described below. The IC holding portion 53a has a disk shape and is supported by the cylindrical portion 51b of the stem 51.

The outer diameter of the portion of the cylindrical portion 51b of the stem 51 where the male screw portion 51d is formed is larger than the outer diameter dimension of the portion where the diaphragm portion 51c is formed. That is, a step 51f is formed on the outer peripheral surface of the cylindrical portion 51b due to the difference in diameter, and the IC holding portion 53a is placed and supported on the step 51f. Further, the outer diameter of the IC holding portion 53a is larger than the outer diameter of the cylindrical portion 51b of the stem 51.

The IC holding portion 53a is formed with an insertion hole 53b into which the cylindrical portion 51b of the stem 51 is inserted. By inserting the cylindrical portion 51b into the insertion hole 53b from the side of the body 4, the strain gauge 52 is exposed and accommodated in the housing 53.

FIG. 4 is a perspective view showing the housing 53 and the stem 51 alone, and FIG. 5 (a) is a top view of the housing 53 as viewed from the opposite side of the stem 51 when the housing 53 is assembled to the stem 51. ..

As shown in these figures, a plate-shaped press-fitting portion 53c formed by bending so as to extend into the housing 53 is formed from the end surface of the insertion hole 53b. The press-fitting portion 53c in the present embodiment is formed in the shape of two opposing plates. On the other hand, a pair of chamfered portions 51g to be press-fitted into the press-fitting portion 53c are formed in a portion of the cylindrical portion 51b of the stem 51 adjacent to the diaphragm portion 51c. By press-fitting the press-fitting portion 53c into these chamfered portions 51g, the housing 53 is assembled to the stem 51 in a non-rotatable state.

A tool engaging portion 53d for engaging a rotary tightening tool (for example, a spanner) (not shown) is provided at the outer peripheral end portion of the IC holding portion 53a. Specifically, the tool engaging portion 53d is composed of a plurality of chamfered portions bent so as to extend from the outer peripheral end portion of the IC holding portion 53a to the opposite side of the body 4. In the examples of FIGS. 3 and 4, the tool engaging portion 53d is composed of a hexahedral chamfered portion, and the distance between the pair of facing chamfered portions is larger than the outer diameter dimension of the cylindrical portion 51b of the stem 51.

As described above, since the housing 53 is assembled in a non-rotatable state with respect to the stem 51, when the tool is engaged with the tool engaging portion 53d to rotate the housing 53, the stem 51 is integrated with the housing 53. It rotates and the male screw 51d of the stem 51 is screwed to the injector body 4.

A mold IC 54 (signal processing circuit) is supported on the IC holding portion 53a via a spacer 57. The mold IC 54 is electrically connected to the strain gauge 52 by a wire bond W, and is configured by sealing the electronic component 54a and the sensor terminal 54b with a mold resin 54m.

The spacer 57 adjusts the height of the mold IC 54 so that the wire bonding portion of the mold IC 54 and the wire bonding portion of the strain gauge 52 are located on the same plane. Further, by making the spacer 57 made of resin, the spacer 57 functions as a heat insulating material, and the heat transferred from the body 4 to the housing 53 via the stem 51 is suppressed from being propagated to the mold IC 54, so that the mold IC 54 can be used. Suppress thermal damage.

The electronic component 54a constitutes an amplifier circuit that amplifies the detection signal output from the strain gauge 52, a filtering circuit that removes noise superimposed on the detection signal, a circuit that applies a voltage to the strain gauge 52, and the like.

The strain gauge 52 to which a voltage is applied from the voltage application circuit constitutes a bridge circuit in which the resistance value changes according to the magnitude of the strain generated in the diaphragm portion 51c. As a result, the output voltage of the bridge circuit changes according to the distortion of the diaphragm portion 51c, and the output voltage is output to the amplifier circuit of the mold IC 54 as the pressure detection value of the high-pressure fuel. The amplifier circuit amplifies the pressure detection value output from the strain gauge 52 (bridge circuit), and outputs the amplified signal from the sensor terminal 54b.

The mold resin 54m is formed in a cylindrical shape extending in an annular shape along the outer peripheral surface of the cylindrical portion 51b of the stem 51. A plurality of sensor terminals 54b extend from the mold resin 54m. These sensor terminals 54b are electrically connected to the electronic component 54a inside the mold IC 54, and function as terminals for outputting the detection signal of the fuel pressure sensor, terminals for supplying power, terminals for grounding, and the like.

A case 56 is attached to the tool engaging portion 53d of the housing 53. The portion of the cylindrical portion 51b of the stem 51 excluding the male screw portion 51d, the strain gauge 52, and the mold IC 54 are housed inside the case 56 and the housing 53. As a result, the metal case 56 and housing 53 block external noise to protect the strain gauge 52 and the mold IC 54. An opening 56a is formed in the case 56, and the sensor terminal 54b extends from the inside to the outside of the case 56 through the opening 56a.

Returning to the description of FIG. 2, the housing 61 of the connector 60 described above holds the connector terminal 63 for the sensor together with the connector terminal 62 for driving. The sensor connector terminal 63 and the sensor terminal 54b are electrically connected via laser welding or the like via electrodes 71, 72, 73, 74, which will be described later. An external harness connector that connects to an external device such as an engine ECU (not shown) is connected to the connector 60. As a result, the pressure detection signal output from the mold IC 54 is input to the engine ECU via the external harness.

Here, when the stem 51 is rotated and the stem 51 is screwed to the injector body 4, the rotational position of the stem 51 is not fixed at a specific position when the screw fastening is completed. This means that the rotation positions of the sensor terminals 54b to 54e of the mold IC are also unspecified when the screw fastening of the stem 51 is completed.

Therefore, each of the electrodes 72, 73, 74 connected to each of the sensor terminals 54b and rotating together with the stem 51 has an annular connection portion 72a, 73a, 74a having a shape extending in an annular shape around the rotation center of the stem 51. Is formed. The annular connection portions 72a, 73a, 74a are electrically connected to each of the plurality of connector terminals 63 after the screw fastening of the stem 51 is completed. As a result, the sensor terminal 54b whose rotation position is unspecified and the connector terminal 63 arranged at a predetermined position of the injector body 4 can be easily electrically connected.

Since the connection portion 71a of the electrodes 71 that is electrically connected to the connector terminal 63 is located at the center of rotation of the stem 51, the rotation position of the connection portion 71a is specified regardless of the rotation position of the stem 51. Further, the plurality of electrodes 71 to 74 are molded and integrated with the molding resin 70 m, and are attached to the upper surface of the case 56 in such a molded state. Further, the connector terminal 63 is formed with a welded portion 63a protruding toward the connecting portions 71a, 72a, 73a, 74a, and the laser energy at the time of laser welding is concentrated on the welded portion 63a.

The fuel pressure sensor 50, the housing 53, the mold IC 54, the case 56, the spacer 57, and the electrode 71, which are composed of the stem 51 and the strain gauge 52, are integrally assembled and unitized. FIG. 3 is a cross-sectional view showing the fuel pressure detection unit U unitized in this way. By screwing the stem 51 to the injector body 4, the fuel pressure detection unit U is detachably attached to the injector body 4. Has been done.

Next, the procedure for assembling the fuel pressure detection unit U will be described with reference to FIG.

First, the housing 53 is press-fitted into the stem 51 to which the strain gauge 52 is attached and assembled. Specifically, the chamfered portion 51 g of the stem 51 is press-fitted into the press-fitted portion 53c of the housing 53. After that, the spacer 57 and the mold IC 54 are fixed to the housing 53. After that, the mold IC 54 and the strain gauge 52 are connected by a wire bond W using a bonding machine. Then, the case 56 is attached to the housing 53.

Further, a plurality of electrodes 71 to 74 are molded with 70 m of mold resin, the molded body is placed at a predetermined position on the upper surface of the case 56, and the electrodes 71 to 74 and the sensor terminal 54b are electrically connected by laser welding or the like. This completes the assembly of the fuel pressure detection unit U.

Next, the procedure for attaching the fuel pressure detection unit U to the injector body 4 will be described.

First, the fuel pressure detection unit U is attached to the injector body 4. Specifically, the rotary tightening tool is engaged with the tool engaging portion 53d of the housing 53 to rotate the housing 53 (that is, rotate the fuel pressure detection unit U). As a result, the male screw portion 51d of the stem 51 is fastened to the female screw portion 45a formed in the recess 45 of the injector body 4. By this screw fastening, the fuel pressure detection unit U is attached to the injector body 4, and at the same time, the sensor side sealing surface 51e is pressed against the body side sealing surface 45b, and the axial force of both sealing surfaces 51e and 45b is generated to generate the metal touch seal. Let me.

Prior to fastening the screws, the injector body 4 is subjected to quenching treatment and carburizing treatment to increase the hardness of the body surface. However, in the carburizing treatment, the body side sealing surface 45b and the female screw portion 45a The part is carburized so that it will not be carburized. For example, when carburizing and quenching, the portion of the body-side sealing surface 45b and the portion of the female screw portion 45a are masked so as not to increase the hardness of these portions.

Next, the drive connector terminal 62 and the lead wire 21 are electrically connected, and the sensor connector terminal 63 and the electrodes 71 to 74 are electrically connected by laser welding or the like.

After that, the connector terminals 62 and 63 and the fuel pressure detection unit U are molded with the molding resin while being attached to the injector body 4. This mold resin becomes the connector housing 61 described above. This completes the attachment of the fuel pressure detection unit U to the injector body 4 and the internal electrical connection.

Next, the contents of the temperature characteristic test and the abnormality inspection for the fuel pressure detection unit U, which are carried out by the fuel pressure detection unit U alone before the fuel pressure detection unit U is attached to the injector body 4, will be described.

As the fuel temperature rises, the thermal expansion deformation of the stem 51 increases, so that the output value of the fuel pressure detection unit U (that is, the sensor output value output from the mold IC 54) drifts. Therefore, it is necessary to calculate the fuel pressure from the sensor output value in consideration of this temperature drift amount. Since the temperature drift amount is an eigenvalue of the stem 51, strain gauge 52, etc., it is necessary to test and obtain the temperature drift amount before shipping the injector to the market.

Therefore, fuel at a known test temperature and test pressure is supplied into the stem 51 from the inflow port 51a, and the fuel pressure is applied to the diaphragm portion 51c. Then, the temperature drift amount with respect to the test temperature is acquired based on the sensor output value, the test pressure, and the test temperature at that time (temperature characteristic test). Then, the compensation value for the sensor output value is acquired based on the temperature drift amount. Alternatively, when the injector is mounted on the internal combustion engine and operated, the sensor output value is corrected using the acquired temperature drift amount.

In addition, before shipping the injector to the market, by checking whether the sensor output value with respect to the test pressure is out of the normal range, for example, a single abnormality of the strain gauge 52 and the mold IC 54, or an electrically welded part of the sensor terminal 54b. Inspect the fuel pressure detection unit U for abnormalities such as defective electrical connection in wire bond W and wire bond W.

According to the present embodiment described in detail above, the following effects can be obtained.

(1) A fuel pressure sensor 50 composed of a stem 51 and a strain gauge 52, a housing 53, a mold IC 54, a case 56, a spacer 57, and an electrode 71 are integrally assembled to form a unit to form a fuel pressure detection unit U, and the stem 51 is formed. Is screwed to the injector body 4 to attach the fuel pressure detection unit U to the body 4. As a result, the above-mentioned temperature characteristic test and abnormality inspection can be performed on the fuel pressure detection unit U alone before the stem 51 is attached to the body 4.

Therefore, when carrying out the above test, it is only necessary to adjust the temperature so that only the stem 51 is stabilized at the test temperature. Therefore, it is not necessary to adjust the body 4 as well as the stem 51 to the test temperature, and the time required for temperature adjustment is shortened. It is possible to improve the workability of the test. Further, since the above inspection can be performed by the fuel pressure detection unit U alone, it is possible to detect an abnormality in the sensor output value before attaching the fuel pressure detection unit U to the body 4, and it is possible to avoid a decrease in the manufacturing yield of the injector.

(2) By screwing the stem 51 to the injector body 4, the fuel pressure detection unit U is assembled to the body 4, and at the same time, an axial force that presses the sensor side seal surface 51e and the body side seal surface 45b is also generated. , The screw parts 45a and 51d for assembling the fuel pressure detection unit U to the body 4 and the screw part for generating the axial force are shared. Therefore, the physique of the injector can be reduced as compared with the case where these screw portions are formed separately, the number of operations for fastening the screws can be reduced, and the productivity of the injector can be improved.

(3) Since the stem 51 is directly metal-touch-sealed to the injector body 4, the metal touch-seal can be made in one place, and the injector can be miniaturized.

(4) Since the housing 53 that holds the mold IC 54 is assembled to the stem 51, the stem 51 can be made smaller than the case where the stem 51 holds the mold IC 54. Therefore, the cost can be reduced by downsizing the stem 51, which has a high material cost.

(5) Since the tool engaging portion 53d is formed in the housing 53, which is a separate member from the stem 51, the stem 51 can be miniaturized as compared with the case where the tool engaging portion is formed in the stem 51. Therefore, the cost can be reduced by downsizing the stem 51, which has a high material cost. Further, since the housing 53 is used to hold the mold IC 54 and engage the rotary tightening tool, the fuel pressure detection unit U can be downsized.

(6) Since the chamfered portion 51g of the stem 51 is press-fitted into the press-fitting portion 53c formed in the insertion hole 53b of the housing 53, it is possible to easily assemble the housing 53 with respect to the stem 51 in a non-rotatable state.

(7) When the injector body 4 is made harder by carburizing, the part of the body side sealing surface 45b is charcoal-proofed. Therefore, when the sensor side sealing surface 51e is pressed against the body side sealing surface 45b to perform metal touch sealing, the body is used. The plastic deformation of the side sealing surface 45b can be promoted. Therefore, the adhesion between the two sealing surfaces 45b and 51e can be improved, and the sealing property of the metal touch seal can be improved. The sealing performance is improved by increasing the screw fastening force to increase the pressing force (axial force) of the stem 51 against the body side sealing surface 45b, and by increasing the processing accuracy of both sealing surfaces 45b and 51e. If you try to do this, the processing cost will increase. On the other hand, according to the present embodiment, the sealing property of the metal touch seal can be improved without increasing the axial force and improving the processing accuracy.

(8) When the injector body 4 is made harder by carburizing, the female screw portion 45a is also charcoal-proofed, so that the possibility of delayed fracture at the female screw portion 45a can be suppressed. Then, by masking the entire recess 45, the masking work for the body side sealing surface 45b and the masking work for the female screw portion 45a can be made the same, so that the workability can be improved as compared with the case where the masking work is performed separately. ..

(9) A sensor-side sealing surface 51e is formed at the end of the cylinder located around the inflow port 51a of the stem 51. That is, since the cylindrical end portion forming the inflow port 51a is used as the sensor-side sealing surface 51e, the stem 51 can be miniaturized.

(10) A male screw portion 51d is formed on the outer peripheral surface of the cylindrical portion 51b of the stem 51. That is, since the cylindrical portion 51b for guiding the high-pressure fuel from the inflow port 51a to the diaphragm portion 51c is used as a portion forming the male screw portion 51d, the stem 51 can be miniaturized.

(11) Since the stem 51 is configured separately from the body 4, when the internal stress of the body 4 generated by thermal expansion and contraction is propagated to the stem 51, the propagation loss can be increased. That is, by configuring the stem 51 separately from the body 4, the influence of the distortion of the body 4 on the stem 51 is reduced. Therefore, according to the present embodiment in which the strain gauge 52 (sensor element) is attached to the stem 51 which is configured separately from the body 4, the strain gauge 52 is attached to the body 4 as compared with the case where the strain gauge 52 is directly attached to the body 4. It is possible to suppress the influence of the generated strain on the strain gauge 52.

(12) Since a material having a coefficient of thermal expansion smaller than that of the body 4 is used as the material of the stem 51, it is possible to prevent the stem 51 itself from being thermally expanded and contracted to cause distortion. Further, as compared with the case where the entire body 4 is made of a material having a small coefficient of thermal expansion, only the stem 51 needs to be made of an expensive material having a small coefficient of thermal expansion, so that the material cost can be reduced.

(13) By holding the drive connector terminal 62 and the sensor connector terminal 63 in the same connector housing 61, both terminals 62 and 63 are configured as a common connector 60. Therefore, the fuel pressure sensor 50 can be mounted on the injector without increasing the number of connectors, and the harness for connecting the external device such as the engine ECU and the connector can be integrated from one connector 60 provided on the injector body 4. It will be postponed. Therefore, the handling of the harness can be simplified. In addition, it is possible to avoid an increase in the time and effort required for connecting the connector.

(Second Embodiment) In the first embodiment, a pair of chamfered portions 51 g are formed on the cylindrical portion 51b of the stem 51, a pair of press-fitted portions 53c are also formed on the housing 53, and the chamfered portions 51 g are press-fitted into the press-fitted portion 53c. The housing 53 is assembled so that it cannot rotate with respect to the stem 51.

On the other hand, in the present embodiment, as shown in FIG. 5B, a knurled groove 510 g is formed on the outer peripheral surface of the cylindrical portion 51b of the stem 51, and the knurled groove is also formed on the inner peripheral surface of the insertion hole 53b of the housing 53. Form 530b. Then, by press-fitting the knurled groove 530b of the housing 53 into the knurled groove 510 g of the stem 51, the housing 53 is assembled in a non-rotatable state with respect to the stem 51.

Alternatively, as shown in FIG. 5 (c), the housing 53 can be attached to the stem 51 by press-fitting the fixing pin P into the gap between the inner peripheral surface of the insertion hole 531b of the housing 53 and the outer peripheral surface of the cylindrical portion 51b of the stem 51. On the other hand, it is assembled in a non-rotatable state. As described above, the same effect as that of the first embodiment is exhibited by this embodiment as well.

(Third Embodiment) In the first and second embodiments, the stem 51 is press-fitted into the housing 53 so that the housing 53 is assembled in a non-rotatable state with respect to the stem 51. On the other hand, in the present embodiment, as shown in FIG. 6, the housing 53 is assembled to the stem 51 in a non-rotatable state by welding the stem 51 and the housing 53.

More specifically, the stem 51 is formed with a disk-shaped welded portion 51h extending radially outward from the outer peripheral surface of the cylindrical portion 51b in a flange shape. Then, in the example shown in FIG. 6A, the bottom surface of the IC holding portion 53a of the housing 53 and the outer peripheral surface of the welded portion 51h are welded at the locations indicated by the mesh wire hatch in the drawing. Further, as shown by the arrow Y1 in the drawing, the stem 51 is welded in a direction inclined by a predetermined angle with respect to the axial direction (vertical direction in FIG. 6). Further, the entire outer peripheral surface of the welded portion 51h may be welded in an annular shape, or the outer peripheral surface may be spot-welded at a predetermined interval pitch.

Further, in the example shown in FIG. 6B, the housing 53 is formed with an annular welded portion 53e protruding from the bottom surface of the IC holding portion 53a and extending in an annular shape. Then, the outer peripheral surface of the welded portion 53e of the housing 53 and the outer peripheral surface of the welded portion 51h of the stem 51 are welded at the locations indicated by the mesh wire hatch in the drawing. Further, as shown by the arrow Y2 in the figure, the stem 51 is welded in a direction perpendicular to the axial direction. Further, the entire outer peripheral surfaces of the welded portions 53e and 51h may be welded in an annular shape, or the outer peripheral surfaces may be spot-welded at a predetermined interval pitch. As described above, the same effect as that of the first embodiment is exhibited by this embodiment as well.

(Other embodiments) The present invention is not limited to the contents described in the above-described embodiment, and may be modified as follows. Further, the characteristic configurations of the respective embodiments may be arbitrarily combined.

-In the first embodiment, a plurality of electrodes 71 to 74 integrated with a mold resin 70 m are provided in the fuel pressure detection unit U to form a unit, but the electrodes 71 to 74 are separate from the fuel pressure detection unit U. It may be composed on the body. In this case, when the above-mentioned various tests and inspections are performed, the electrodes 71 to 74 are not assembled to the fuel pressure detection unit U.

-In the first embodiment, the housing 53 assembled to the stem 51 supports the mold IC 54, but the housing 53 may be abolished so that the stem 51 supports the mold IC 54. For example, in the same manner as the welded portion 51h shown in FIG. 6, a portion extending radially outward from the outer peripheral surface of the cylindrical portion 51b in a flange shape is formed on the stem 51, and the mold IC 54 is supported on the flange-shaped extending portion. Let me do it. In this case, it is desirable to adjust the height of the mold IC 54 using the spacer 57.

-In each of the above embodiments, the strain gauge 52 is used as the sensor element for detecting the amount of strain of the stem 51, but other sensor elements such as a piezoelectric element may be used.

-In the first embodiment, the connection portions 72a to 74a of the electrodes 72 to 74 with the connector terminal 63 are formed in an annular shape, but may be formed in an arc shape. Further, although a plurality of annular connecting portions 72a to 74a are arranged side by side in the radial direction, they may be arranged side by side in the axial direction.

-In each of the above embodiments, the present invention is applied to an injector configured such that a high-pressure port 43 is formed on the outer peripheral surface side of the injector body 4 and high-pressure fuel is supplied from the outer peripheral surface side. A high-pressure port 43 may be formed on the anti-injection hole side in the axial direction of the above, and may be applied to an injector configured to supply high-pressure fuel from the anti-injection hole side.

-In each of the above embodiments, the present invention is applied to the injector of a diesel engine, but the present invention may be applied to a gasoline engine, particularly a direct injection type gasoline engine that directly injects fuel into the combustion chamber E1.

4 ... Injector body (body), 6 ... High pressure passage, 51 ... Stem (distortion body), 51a ... Inlet, 51b ... Cylindrical part, 51c ... Diaphragm part, 51d ... male screw part (screw part on the sensor side), 51e ... seal surface on the sensor side, 52 ... strain gauge (sensor element), 53 ... housing (holding member), 53a ... IC holding part (Accommodation part), 53b ... Insert hole, 53d ... Tool engagement part (Accommodation part), 54 ... Mold IC (Signal processing circuit), U ... Fuel pressure detection unit.