Liquid fuel injection pump

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid fuel injection pump for supplying an internal combustion engine comprising a housing, a rotary manifold mounted in a housing, a drive shaft coupled to a manifold provided with transverse bore. which are located at the outer end of the plungers and engage a cam surface formed on a cam ring surrounding the distributor, from the stops to limit the movement of the pump plungers outwards and from the fuel supply and discharge channels from the bore when the distributor is rotating.

For a pump of the above type, it is necessary to be able to vary the amount of fuel delivered to control the amount of fuel delivered to the associated engine. This can be achieved by using a throttle valve through which fuel flows into the bore from a pressurized fuel source. However, the amount of fuel entering the bore at a given throttle setting varies with engine speed. For example, as the engine speed increases, the amount of fuel delivered to the engine decreases each time the plunger moves inwardly. Conversely, if the engine speed decreases, the amount of fuel delivered to the engine increases each time the plunger moves inwards and can be actuated to determine the maximum amount of fuel that can be delivered. To ensure that the amount of fuel delivered each time the plunger moves inwardly, the throttle must be readjusted at each speed change or the pressure of the fuel passing through the throttle must be changed. Therefore, it is not easy to provide the pump with a control that, when set to the appropriate position, ensures that the set amount of fuel is delivered, whatever the engine speed.

Another way to vary the amount of fuel delivered to the engine is to measure the amount of fuel in the variable volume chamber in the pump body and deliver this measured amount of fuel to the borehole. This measurement can be carried out using a shuttle whose stroke in the chamber can be directly adjusted, for example by means of an adjustable stop. This arrangement theoretically represents a direct change in the amount of fuel delivered as the plunger moves inwards according to the adjustable stop setting. A drawback of this embodiment is the difficulty of transferring fuel from the chamber to the bore, and it has been shown in practice that the amount of fuel delivered at a given adjustable stop setting can vary substantially with varying engine speed.

It is also known to control the amount of fuel delivered as the plunger moves inwardly by adjusting the stops so that the plunger actually acts as a shuttle, but without the problem of moving the fuel to the bore.

Such a pump is described in British Patent No. 1,171,226. The pump of this disclosure is provided with an inclined fork that interacts with a supplementary follower surface and is coupled or forms part of a receptacle fitted with axial displacement on the drive shaft. which is rotatable with the distributor. The drawback of this arrangement is that the sleeve rotates with the shaft and must be attached to the adjustable part firmly fixed in the pump housing for adjustment. Any play between the sleeve and the adjustable part can impair the pump calibration, since friction between the sleeve and the shaft will require more effort to move the sleeve.

The drawbacks of the known injection pump technique of the above-mentioned type are overcome by the fact that the manifold is housed in a housing which further comprises means for changing the axial position of the manifold within the housing and the drive shaft is provided with a mist-shaped extended part disposed in a cylindrical. a chamber delimited by two body parts. The means for changing the axial position of the manifold is an electromagnetic valve connected to a chamber formed at the end of the bore in the closing portion of the body. In another embodiment, the means for changing the axial position of the manifold in one direction comprises a coil pressure spring housed in a cylindrical bore of the drive shaft and a button that engages a lever for changing the axial position of the manifold in a direction opposite to the direction of action of the coil pressure spring. In another embodiment, the means for changing the axial position of the distributor comprises a spring supported by one end thereof on a thrust washer which is one side in contact with the distributor, the other side with the adjusting member, the other end of the distributor engaged with the piston mounted in the cavity a shaft connected by a duct to a low pressure fuel feed pump.

The extended part of the drive shaft surrounds the manifold, the inner surface of which is conical and has grooves which are connected to the pump plungers and which accommodate the rollers supported by the cam followers, the plungers being connected to the rollers and the cam followers by radial pins. The cam follower is provided with projections with conical surfaces corresponding to the conical part of the extended part of the drive shaft. In another embodiment, the widened portion of the drive shaft has an inner cylindrical surface in which a pair of opposing grooves is formed, each containing a pair of stops formed by the arms of the U-shaped part and connected by a connecting portion provided with a coil spring opening. . The bore for the coil compression spring is provided with a. a circumference of the carriers in which one end of a weak coil spring is received, the opposite end of which is supported on an adjacent side plate.

An advantage of the injection pump according to the invention is that the amount of fuel delivered to control the amount of fuel delivered to the engine can be varied in a simple arrangement. The pump according to the invention is further provided with a device for its safe operation.

Examples of devices according to the invention are further p. 1 shows a sectional side view of the pump according to the invention, FIG. 2 shows a section of the pump according to FIG. 1 in a sectional view through another radial plane, FIGS. Fig. 1, 2, Fig. 5 is a cross-sectional view of a portion of the pump of Fig. 1; Fig. 6 is a cross-sectional view of a modified portion of the pump of Fig. 1; Fig. 7; 1, FIG. 8 Fig. 9 is a cross-sectional view of another exemplary embodiment of the pump according to Figs. 1 and 8, similar to Figs. 3 and 4; and 12 are cross-sectional planes AA and BB of FIG. 10, FIG. 13 is a perspective view of a portion of the pump shown in FIG. 10.

According to FIG. 1, the pump according to the invention consists of a housing 10 which is formed by a sand-colored part 11, the open end of which is closed by a closing part 12. The housing 10 is provided with feet 13 with openings through which the housing 10 can be connected. with which it is affiliated.

In the cup-shaped part 11 of the body 10 there is a rotatable drive shaft 14, which is in operation connected to the drive member of the coupled motor, so that it rotates synchronously with the motor. The drive shaft 14 extends into a substantially cylindrical chamber 15 delimited by two parts of the body 10, consisting of two parts and is provided with a dish-shaped extended portion 14a disposed in the cylindrical chamber 15. The widened portion 14a of the drive shaft 14 is hollow with a smooth inner surface and has the shape of a straight cylinder, the lower end of which is smaller in diameter and has a centering ring 17 abutting the closure portion 12 of the body 10. the drive shaft 14 is tapered for the purpose which will be explained below. The drive shaft 14 is not provided with a cylindrical bore 18. The outer end of the body 10 is provided with an oil seal adjacent the drive shaft 14, which is mounted. The drive shaft 14 is secured against axial displacement by the bearing surfaces on which the peripheral surfaces of the enlarged part of the drive shaft 14 abut. In one embodiment, the abutment surface forms a portion 12 of the body 10, in another embodiment the annular disc 21, which surrounds the drive shaft 14, and which further forms the end cap, serves as the abutment surface. the low pressure fuel feed pump 22. The low pressure fuel rotor 22 of the brazing pump 22 is mounted on the drive shaft 14 and the rotor 22a is provided with vanes that interact with an eccentrically disposed area on the stator ring 22b that is located in the body portion 11. The low pressure fuel feed pump · 22 has a fuel inlet 23 connected and a fuel inlet in the body mounted in the reader.⁵ 11 of the housing 10 (not shown) and the fuel spout 24. The low pressure fuel feed pump 22 is provided with a safety valve 25 ensuring that the outlet pressure of said pump 22 is maintained within the required limits, and the safety valve 25 is connected between the inlet 23 and drain 24.

A cylindrical bore 26 is formed in the body portion 12 in which the sleeve is fastened

27 Mar: An angular and axially displaceable distributor 28 is received in the sleeve, extending into the chamber 15 and having an expanded head located within the chamber 15. A transverse bore 29 is formed in the distributor head 28 in which a pair of pump plungers 30 is received. with a blind channel 31 formed in the manifold 28 and closed at the end located within the head portion by a plug. As can be seen more clearly from FIG. 2, 3 and 4, the channel 31 communicates with a pair of diametrically spaced longitudinal grooves 32 formed on the periphery of the manifold 28 and connected to the channel 31 by one or more connecting channels. The channel 31 is also connected to another longitudinal groove 33 formed around the periphery of the manifold 28, and this groove 33 is successively connected to a plurality of outlet channels 34 formed in the sleeve 27. As can be seen from Figure 2, the outlet channels 34 'are connected to the outlets. 35 in part 12 of the body 10. Each outlet 35 has a^ýPressure valve 36 of conventional type. The groove 32 coincides with the inlet openings 37 formed in the sleeve 27 and connected to the peripheral groove 38 formed on the periphery of the sleeve 27. As shown in FIG. 1, the groove 38 communicates with the outlet 24 of the low pressure fuel feed pump 22 via a two-position valve 39. According to need, the single groove 32 may be provided with a plurality of supply channels equal to the number of outlets.

The head of the distributor 28 is surrounded by a cam ring 41 on the inner surface of which a pair of opposed cam thumbs is formed. In the exemplary embodiment, the pump is provided with three pairs of inches as it is intended to supply fuel to a six-cylinder engine. The cam ring 41 is rotatable about the axis of rotation of the distributor 28 by means of a hydraulic device 42 connected to the cam ring 41 by a radial pin 43. The hydraulic device 42 comprises a resiliently loaded piston housed in a cylinder, one end of which is supplied with a pressurized fluid acting on the piston so as to pressurize it against the action of a resilient load.

On the outer edges of the pump plungers 30 are located two cam followers, each consisting of a roller 44 supported by the caliper 45. The cam followers are held in axial position relative to the distributor 28 by means of side plates 46, 47 which are attached to the side surface of the distributor head 28 As shown in FIG. 5, the side plates 46, 47 are preferably annular in shape and have a pair of outwardly projecting tongues 48 that engage grooves 16 formed in the enlarged portion 14a of the drive shaft 14. The plates 46, 47 shown in FIG. 5, They transmit the rotational movement from the drive shaft 14 to the distributor 28. The yokes 45 are also located in the grooves 16 and the rotary movement is transmitted directly to the yokes 45 by the drive shaft 14. The circumferential face of the yokes 45 is provided with circumferential outlets 49 (FIG. 8) whose outer surfaces in the radial direction are tapered to abut a tapered surface formed on the outer surface of the widened portion 14a of the drive shaft 14.

While the fuel is conveyed to the transverse bore 29 when the longitudinal groove 32 is in alignment with the inlet port 37, the pumping plungers 30 are moved outward by the fuel pressure, causing the yokes 45 and the rollers 44 to move outwards. This outward movement is limited by the abutment of the conical surfaces on the yokes 45 and the drive shaft 14 and the extent of the outward movement can be varied by the axial displacement of the distributor 28. Thus, it is possible to control the amount of fuel supplied to the transverse bore 29, and this in turn determines the amount of fuel passing through the outlet as the pumping plungers 30 move outward by the cam thumbs.

The axial position of the distributor 28 can be changed mechanically or hydraulically. In the described arrangement, this change is achieved by varying the pressure within the chamber 50 formed at the end of the bore 26 in the body portion 12. The bore 26 is closed by the shut-off member and the pressurized fuel is conveyed into the chamber 50 through the constricted orifice 51 in sleeve 27. is connected to the low pressure fuel feed pump outlet 24. Fuel can escape from chamber 50 so that it can be controlled in chamber 50 by solenoid valve 52. In addition, the manifold 28 is subjected to a pressure coil spring 53 mounted in a cylindrical bore 18 formed in the drive shaft 14. Said spring 53 acts between the drive shaft 14 and and pushes the manifold 28 in a direction opposite to the direction of pressure of the fuel in the chamber 50 that acts on the manifold 28.

By varying the pressure in the chamber 50 by the solenoid valve 52, the axial position of the manifold 28 can be changed and the amount of fuel conveyed by each inward movement of the pumping plungers can also be varied.

At a given setting of the manifold 28, in the absence of leakage, the amount of fuel delivered by the pump plungers 30 remains constant over the entire speed range of the coupled engine. The axial position of the manifold 28 is indicated by a position sensor 54, which is located on the borehole closure 26 and can be mounted thereon for adjustment. Preferably, the position sensor 54 comprises a portion that is disposed on the manifold

28. WITH^;The signal from the position sensor 54 can be used to signal the rotational speed of the distributor 28 as well as a signal indicating its axial position and thus the amount of fuel conveyed by the pump. During operation, these signals are fed to an electronic control system, which is also supplied with signals indicating the various operating parameters of the motor and the desired motor speed. This control system controls the operation of the solenoid valve 52 thereby ensuring that the correct amount of fuel is supplied to the coupled engine.

Alternatively, the axial adjustment of the manifold 28 * may be accomplished by mechanical means comprising, for example, a button 28a engaging the opposite end of the distributor 28 than the coil spring 53, the button 28a being engaged by the lever 28b as shown in FIG. in this case, the solenoid valve 52 and the tapered neck 51 are omitted.

In any case, the effort required to move the manifold 28 will be largely equal to the force exerted by the coil compression spring 53, since any friction between the manifold 28 and the sleeve 27 will be minimal relative to the relative rotation of the two parts.

In the arrangement shown in FIG. 1, in the event of a pressure drop in the chamber 50, the manifold 28 will for some reason be moved by the coil spring 53 to the position where the pump of the invention delivers the maximum amount of fuel. This may cause damage to the coupled engine. To prevent this, as shown in FIG. 7, at the opposite ends of the manifold 28, a spring 61 is positioned to push the manifold 28 into a position corresponding to the minimum amount of fuel. One end of the spring 61 is supported by an adjusting member 62 for adjusting the force exerted by the spring 61, and the other end of the spring 61 is supported by a thrust pad 63 which applies pressure to the manifold 28. The thrust pad 63 may be fabricated of synthetic resin impregnated fabric. or it may be formed of metal and separated from the manifold 28 by a thin layer of fuel supplied from a channel 64 connected as a resistive member to the output of the low pressure fuel feed pump 22 '.

The opposite end of the manifold 28 engages the piston 65, which is disposed in a cavity formed in the drive shaft 14. The piston is pressurized from a low-pressure fuel feed pump 22 and controlled by a valve similar to a solenoid valve 52. Increase the pressure applied to the piston 65 to increase the amount of paFva supplied to the engine. The pressure fuel supply to the piston cylinder 65 is preferably provided by a conduit in the manifold 28 which terminates at the manifold surface 28 and extends to the peripheral groove 66 defined by adjacent edges of the sleeves forming the tubular bearing 20. Over-wear of the sleeves results in fuel leakage and pressure fuel acting on the piston 65, thereby reducing the amount of fuel supplied to the coupled engine. The only drawback of this arrangement is that the piston 65 can seize. In operation, however, the drive shaft 14 will be subjected to torsional vibrations and also to speed changes, which tends to cause angular displacement of the pistons 65 and the drive shaft 14.

Giant. 8 shows an arrangement according to which the axial position of the manifold 28 is changed so that the yoke rollers 44 maintain a relative position relative to the manifold 28.

The outer edges of the pump plungers 30 are provided with blind bores in which the pins 60 facing away from the cam followers are received. These pins 60 are stepped in shape. The wider ends of the pins 60 are embedded in blind bores in the pump plungers 30, while the narrower ends pass through the openings in the yokes 45 and terminate in the peripheral groove formed in the cam followers 44^:waiting. The brackets 45 engage the walls of the grooves 16 formed in the extended portion 14a of the drive shaft 14 as in the previous embodiment, and rotational movement is transmitted to the distributor 28 via pins 60 and pumping plungers 30. Pins 60 also secure the rollers 44 against axial movement of the cam followers.

Figure 8 also shows a modification in which a radial channel 61, which extends to the periphery of the manifold 23, is connected to the channel 31 and which is normally covered by the sleeve 27 except when the manifold 28 is moved to the extreme left position. The rollers 44 can not only contact the cam follower but also engage with the cam follower, which can occur in the case of a special cam follower for controlling fuel delivery when the feed is stopped. Any inward displacement causing the displacement of fuel from the transverse bore 29 in which the pumping plungers 30 are located means that the fuel flows through the channel 61 into the chamber 15 and not into the associated engine.

This duct 61 can be used to bleed the pump according to the invention after installation or maintenance, or when air has entered the different ducts of the pump. If necessary, the channel connecting the grooves 32 to the channel 31 will have to be connected to the channel 31 in close proximity to the transverse bore 29. In this case, the fuel coming from the low pressure fuel feed pump 22 reaches the channels 31 in close proximity to the transverse bore 29 and any air bubbles that have entered the fuel pass through the channel 31 and then through the channel 61.

The venting can advantageously be carried out when excess fuel is delivered to the engine to start the machine. In this case, and as shown in FIG. 9 showing the fuel supply portion to the four-cylinder engine, the sleeve 27 is provided with several channels 62a whose angular position corresponds to the position of the exit channels 34. The conduits 62a are of limited size and are in such an axial position that, when the distributor 28 is moved to the excess fuel supply position, the longitudinal groove 33 may coincide with them. The inner ends of the conduits 62a are connected to the longitudinal conduit 31 and move. a portion of the fuel flows through one of the channels 62a inwardly, but under normal conditions the fuel will also be conveyed to the respective outlet. If air enters the passages 62a, the fuel pressure induced by the inward movement of the pumping plungers 30 may not be sufficient to lift the discharge valve and the fuel and air then gradually flow through the passages 62a until the passages in the manifold 28 are vented.

If it is necessary to ensure that no fuel flows through the outlet passages 34 when the distributor 28 is set to a position corresponding to zero fuel, it will nevertheless be necessary to create channels 61.

1 and 8, the widened portion 15a of the drive shaft 14 surrounding the distributor 28 in which the grooves 16 are formed has a tapered inner surface. This conical surface is difficult to manufacture. In order to facilitate the manufacture of the drive shaft 14, the structure shown in Figures 10 to 13 is designed. In this solution, the extended portion 14a of the drive shaft 14 has an inner surface in the form of a straight cylinder 65 in which a pair of opposing grooves 66 are formed. In each groove 66 there is a double bore. These U-shaped parts 67 are part of the sheet metal blank shown in the perspective view of FIG. 13. The two U-shaped parts 67 are interconnected by a connecting part 68, which is a whole circular shape and is supported by cylinder wall 65. A coil spring 53 extends through an aperture 69 in the connector 68 and from the inner surface of the connector 68 protrudes circumferentially three tabs 71 which receive one end of a weak coil spring 72, the opposite end of which is supported on an adjacent side plate 46. As 1, the side plates 46 are provided with tongues 48 disposed between the arms of the U-shaped parts 67 and transmitting rotational movement to the distributor 28. As can be seen in FIG. 13, the radial inner edges 73 of the arms of the U-shaped portion taper outwardly from the coupling portion 68, and these edges 71 interact with the inclined surfaces of the yokes 45 supporting the rollers 44 to limit the outward movement of the pump plungers 30. A weak coil compression spring 72 presses the coupling portion 68 against the base of the direct cylinder 65 of the drive shaft 14 while assisting the coil compression spring 53. The surfaces of the tapered edges 73 of the arms of the U-shaped connector 68 lie in the same plane, as well as the inclined surfaces on the brackets 45. This also facilitates the construction of the inclined surfaces in the brackets 45, since these are flat - without needing to be curved an inner surface of the extended portion 14a of the drive shaft 14.

As an alternative to the use of a separate U-shaped member 67, the widened portion 14a of the drive shaft 14, which in the described cup-shaped examples, can be provided