Brake control device for vehicle

The present invention relates to a vehicle braking control technique, and more particularly to a vehicle braking control device having a solenoid valve that adjusts the control hydraulic pressure so as to reach a target hydraulic pressure.

Conventionally, as a braking control device for vehicles such as automobiles, an oil pump driven by a motor is provided in the middle of a hydraulic conduit, and the hydraulic fluid on the discharge side of the oil pump is accumulated in an accumulator to keep the accumulator pressure at a high pressure. Are known. This high-pressure hydraulic fluid is introduced into the wheel cylinder via the booster valve and the hydraulic fluid passage of the electromagnetic flow control valves provided on each wheel in response to the driver's brake pedal operation, and exerts the desired braking force. Will be done.

In the braking control device for vehicles as described above, the amount of liquid consumed increases in the low pressure region. In the region where the amount of liquid consumed is large, the step-up and step-down widths per unit amount of liquid are small, so the rise and fall of the hydraulic pressure become gentle, and the time until the actual pressure reaches the target pressure becomes longer, and the low-pressure region It was the cause of the decrease in control response in.

Therefore, in Patent Document 1, when a pressure region having a large amount of liquid consumption exists within the control hydraulic pressure range in the control of the load hydraulic pressure, the pressure region is arbitrary for an arbitrary time with respect to the target pressure. A technique for improving the pressure responsiveness by performing overshoot control for adding the pressure of the above is disclosed.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 11-154024</text></patcit>

<p> However, in the above-mentioned Patent Document 1, there is a problem that the pressure suddenly rises in the portion transitioning from the region where the amount of liquid consumed is large to the region where the amount of liquid consumed is small, and abnormal noise and vibration are generated accordingly. .. Especially with drum brakes, it is difficult to know the change point of the hydraulic pressure, it is difficult to match the timing to stop the overshoot control, and there is an abnormal noise when changing from a region with a large amount of liquid consumption to a region with a small amount of liquid consumption. And vibration are likely to occur.</p><p> The present invention has been made in view of such a situation, and an object of the present invention is to provide a technique for improving pressure responsiveness while suppressing generation of abnormal noise and vibration.</p>

<p> In one aspect of the present invention, a wheel cylinder to which hydraulic oil is supplied to drive a brake, a solenoid valve for adjusting the amount of liquid supplied to the wheel cylinder, and control of the solenoid valve so as to reach a target hydraulic pressure. In a vehicle braking control device including a feedback control means for calculating a current, a fast that increases a control current more than a value calculated by the feedback control means in a region where the hydraulic gradient of the wheel cylinder is low rigidity. It is a vehicle braking control device further provided with a fast fill control means for executing fill control.</p><p> Here, the "hydraulic gradient" refers to the gradient of the graph when a graph is drawn with the wheel cylinder hydraulic pressure on the horizontal axis and the amount of liquid supplied to the wheel cylinder on the vertical axis. Further, in this graph, a state in which the amount of liquid consumed is large but the change in the hydraulic pressure of the wheel cylinder is small is called "low rigidity". The large state is called "high rigidity". According to this aspect, since the amount of liquid supplied to the wheel cylinder is increased by executing the fast fill control, the pressure responsiveness of the brake in the low rigidity region of the hydraulic pressure gradient can be improved.</p><p> The fast fill control means starts the fast fill control when the hydraulic pressure of the wheel cylinder reaches a threshold value, and when the increment from the threshold value exceeds a predetermined value, the fast fill control means. The control may be terminated. According to this, by stopping the fast fill control when the hydraulic pressure gradient changes from low rigidity to high rigidity, the amount of liquid supplied to the wheel cylinder is reduced, which is different from the improvement of the pressure response of the brake. It is possible to suppress both sound and vibration.</p><p> The hydraulic pressure generated in the wheel cylinder when the hydraulic pressure gradient of the wheel cylinder becomes lower than a predetermined value may be set as the threshold value. The hydraulic pressure generated in the wheel cylinder when a liquid amount determined according to the capacity of the space formed by the wheel cylinder is supplied may be set as the threshold value. According to this, it becomes possible to determine the end time of the fast fill control by learning the time point when the rigidity becomes low. This is because the hydraulic pressure at the start of low rigidity varies from wheel cylinder to wheel cylinder, but the pressure that increases when shifting from low rigidity to high rigidity varies little depending on the wheel cylinder.</p><p> The control current is stopped when the hydraulic pressure gradient of the wheel cylinder becomes lower than a predetermined value, and the hydraulic pressure of the wheel cylinder when a predetermined time elapses is set as the threshold value. You may. Alternatively, after supplying a liquid amount determined according to the capacity of the space formed by the wheel cylinder, the control current is stopped, and the threshold value of the liquid pressure of the wheel cylinder when a predetermined time elapses. It may be set as a value. According to this, even if pulsation occurs in the initial stage of supplying the amount of liquid to the wheel cylinder, the control current is turned off and the product waits until the liquid pressure stabilizes. The hydraulic pressure for initiating fill control can be learned.</p><p> Instead of stopping the control current immediately, it may be stopped after gradually decreasing. Since the hydraulic pressure sensor that detects the hydraulic pressure detects the hydraulic pressure upstream of the wheel cylinder, there is a time lag before the wheel cylinder reaches that pressure, so it may be possible to reduce the current by fast fill control to zero at once. It is possible to improve the accuracy of control by gradually decreasing the amount.</p><p> The solenoid valve may be a linear valve having linear operating characteristics with respect to the control current.</p>

<p> According to the vehicle braking control device according to the present invention, it is possible to improve the pressure response in the low-rigidity region of the hydraulic pressure gradient while suppressing the generation of abnormal noise and vibration.</p>

First, the overall configuration of the hydraulic system 100 and the electronic control unit 200 to which the embodiment is applied will be described, then the problems recognized by the present inventor will be described, and then the control according to the embodiment will be described. In the following description, the electronic control unit 200 may be regarded as a braking control device alone, or a combination of the hydraulic system 100 or a part thereof and the electronic control unit 200 may be regarded as a braking control device.

FIG. 1 shows the overall configuration of the hydraulic system 100 and the electronic control unit 200. The hydraulic system 100 mainly includes an actuator 80 and a master cylinder 14 other than the actuator 80.

The brake pedal 12 is provided with a stroke sensor 46 that detects the stepping stroke. The master cylinder 14 pumps brake oil, which is a working fluid, in response to a driver's depression of the brake pedal 12. A dry stroke simulator 13 is provided between the brake pedal 12 and the master cylinder 14.

One end of the brake hydraulic control conduit 16 for the right front wheel and the brake hydraulic control conduit 18 for the left front wheel is connected to the master cylinder 14, and these brake hydraulic control conduits exert the braking force of the right front wheel and the left front wheel, respectively. It is connected to the wheel cylinders 20FR and 20FL for the right front wheel and the left front wheel. The right electromagnetic on-off valve 22FR and the left electromagnetic on-off valve 22FL, which are normally open (hereinafter referred to as "normally open type"), are inserted in the middle of the brake hydraulic control conduits 16 and 18 for the right front wheel and the left front wheel, respectively. In addition, right master and left master pressure sensors 48FR and 48FL are provided to measure the master cylinder hydraulic pressure on the right front wheel side and the left front wheel side, respectively. When the driver depresses the brake pedal 12, the stroke sensor 46 detects the depressing, but assuming a failure of the stroke sensor 46, the right master and left master pressure sensors 48FR and 48FL measure the master cylinder hydraulic pressure. Also, the depression of the brake pedal 12 is detected. Monitoring the hydraulic pressure of the master cylinder with two pressure sensors is from a fail-safe point of view.

A reservoir tank 26 is connected to the master cylinder 14, a wet stroke simulator 24 is connected via an on-off valve 23, and one end of a hydraulic supply / exhaust conduit 28 is connected to the reservoir tank 26. The oil pump 34 driven by the motor 32 is provided in the hydraulic supply / discharge conduit 28. The discharge side of the oil pump 34 is a high-pressure conduit 30, which is provided with an accumulator 50 and a relief valve 53. The accumulator 50 accumulates brake oil that has been made high pressure in the range of, for example, 16 to 21.5 MPa (hereinafter referred to as "control range") by the oil pump 34. The relief valve 53 opens when the accumulator pressure is abnormally high, for example, 30 MPa, and allows high-pressure brake oil to escape to the hydraulic supply / discharge conduit 28.

The high-pressure conduit 30 is provided with an accumulator pressure sensor 51 that measures the accumulator pressure. The electronic control unit 200, which will be described later, inputs the accumulator pressure, which is the output of the accumulator pressure sensor 51, and controls the motor 32 so that the accumulator pressure falls within the control range.

Each of the high-pressure conduits 30 is normally closed (this is called a "normally closed type"), and an electromagnetic flow control valve used for boosting the pressure of the wheel cylinder when necessary, that is, a pressure boosting valve 40FR, which is a linear valve. , 40FL, 40RR, 40RL, right front wheel wheel cylinder 20FR, left front wheel wheel cylinder 20FL, right rear wheel wheel cylinder 20RR, left rear wheel wheel cylinder 20RL (hereinafter collectively referred to as "wheels" It is connected to (called cylinder 20). Hereinafter, reference numeral 40 is used when the pressure boosting valves 40FR, 40FL, 40RR, and 40RL are collectively referred to.

Drum brakes 60FR, 60FL, 60RR, 60RL are provided on the right front wheel, left front wheel, right rear wheel, and left rear wheel of a vehicle (not shown), and the brake shoes are driven by the wheel cylinders 20FR, 20FL, 20RR, and 20RL, respectively. Is designed to exert braking force by pressing the wheel against the drum. The structure and operation of the drum brake 60 will be described later with reference to FIG.

The wheel cylinder 20FR on the right front wheel and the wheel cylinder 20FL on the left front wheel are hydraulically supplied and discharged via electromagnetic flow control valves used for decompression when necessary, that is, normally closed pressure reducing valves 42FR and 42FL, which are linear valves. It is connected to conduit 28. Further, the wheel cylinder 20RR for the right rear wheel and the wheel cylinder 20RL for the left rear wheel are connected to the hydraulic supply / exhaust conduit 28 via the normally open pressure reducing valves 42RR and 42RL, respectively.

Right front wheel, left front wheel, right rear wheel, left rear wheel wheel cylinder 20FR, 20FL, 20RR, 20RL, for right front wheel, left front wheel, right rear wheel, which measure the hydraulic pressure in the wheel cylinder, respectively, Pressure sensors 44FR, 44FL, 44RR, 44RL for the left rear wheel are provided.

The electronic control unit 200 controls an electromagnetic on-off valve 22FR, 22FL, a motor 32, four booster valves 40FR, 40FL, 40RR, 40RL, and four pressure reducing valves 42FR, 42FL, 42RR, 42RL. Reference numeral 42 is used when the pressure reducing valves 42FR, 42FL, 42RR, and 42RL are collectively referred to. The electronic control unit 200 includes a calculation unit 202 by a microcomputer, a ROM 204 for storing various control programs, and a RAM 206 used as a work area for data storage and program execution.

Although details are not shown, the calculation unit 202 has pressure sensors for the right front wheel, left front wheel, right rear wheel, and left rear wheel from the pressure sensors 44FR, 44FL, 44RR, and 44RL, respectively, inside the wheel cylinder 20FR of the right front wheel. Pressure signal, pressure signal in the left front wheel wheel cylinder 20FL, pressure signal in the right rear wheel wheel cylinder 20RR, pressure signal in the left rear wheel wheel cylinder 20RL (hereinafter, overall wheel cylinder hydraulic pressure) (Called a signal) is input. Further, the calculation unit 202 has a signal indicating the depression stroke of the brake pedal 12 from the stroke sensor 46 (hereinafter referred to as a stroke signal) and a signal indicating the master cylinder hydraulic pressure from the right master and left master pressure sensors 48FR and 48FL (hereinafter referred to as the master). A cylinder hydraulic pressure signal) and a signal indicating the accumulator pressure (hereinafter referred to as an accumulator pressure signal) are input from the accumulator pressure sensor 51.

ROM 204 of the electronic control unit 200 stores a predetermined braking control flow. The calculation unit 202 calculates the target deceleration of the vehicle based on the stroke signal and the master cylinder hydraulic pressure signal, and based on the calculated target deceleration, the target wheel cylinder hydraulic pressure of each wheel (hereinafter referred to as the target hydraulic pressure P)._refCalculates the wheel cylinder hydraulic pressure of each wheel (hereinafter, also referred to as control hydraulic pressure P)._wcAlso called) is the target hydraulic pressure P_refControl to be.

FIG. 2 is a functional block diagram related to hydraulic pressure control by the arithmetic unit 202. The arithmetic unit 202 has a fast fill control unit 220 and a feedback control unit 222, and has a target hydraulic pressure P._refThe control current I to be supplied to the booster valve 40 and the pressure reducing valve 42 (hereinafter, these are also simply referred to as linear valves 40 and 42) is calculated in response to the input of. Control hydraulic pressure P obtained by the operation of linear valves 40 and 42 driven by control current I_wcIs fed back to the arithmetic unit 202.

The fast fill control unit 220 has a target hydraulic pressure P._refBased on the physical characteristics of the linear valves 40 and 42 and the load model, the fast fill current I is obtained from the slope of the target hydraulic pressure, valve opening current, etc. by a known method._FIs calculated under a predetermined gain and output. However, the fast fill control unit 220 uses the fast fill current I._FIn calculating, the properties of the wheel cylinder system with respect to hydraulic pressure are reflected. The wheel cylinder system refers to a space filled with high-pressure brake oil from the pressure boosting valve 40 to the wheel cylinder in the pressure boosting mode during braking.

Specifically, 1) If the capacity of the wheel cylinder system is larger than the predetermined reference capacity, the fast fill current is corrected based on the capacity ΔI.₁2) If the initial rigidity of the wheel cylinder system with respect to the hydraulic pressure is lower than the predetermined reference rigidity, the rigidity-based correction amount ΔI is added to the fast-fill current.₂Put on. A rubber member in a pipe that expands with hydraulic pressure, a clearance that allows brake oil to enter the inside through structural holes and gaps when hydraulic pressure is applied, and a pipe or tank shape that increases in diameter when hydraulic pressure is applied. If there is a member of the above, the initial rigidity with respect to the hydraulic pressure becomes low. The two corrections may be performed at the same time, and the fast fill control unit 220 internally executes the following calculation. I_F I_F+ ΔI₁+ ΔI₂

Here, as the "predetermined reference capacitance" and the "predetermined reference rigidity", those obtained in the past experiments may be used, and the correction amount may be determined by the difference from those reference values. The amount of correction may be variable depending on the magnitude of the difference. However, as a matter of course, in addition to finding the correction amount from the reference value, the optimum fast-fill current I in the experiment from the beginning_FYou may derive the value of. It should be noted that the shape of a member whose rigidity is a problem does not change when a high hydraulic pressure is applied to some extent, and is balanced by stress or the like. Therefore, the rigidity becomes a problem when the hydraulic pressure is relatively low. Therefore, it is useful to consider the initial rigidity of the wheel cylinder system in the fast fill control performed in the initial stage of the pressure boosting mode as in the present embodiment. Good responsiveness to braking requirements can be obtained even when the capacity of the wheel cylinder system is large or the initial rigidity is low.

Subtraction unit 234 is the target hydraulic pressure P_refFrom control hydraulic pressure P_wcReduce the hydraulic pressure difference P_errorIs output. The feedback control unit 222 has a hydraulic pressure difference P from the subtraction unit 234._errorBy receiving the input of, PID control, etc., the hydraulic pressure difference P_errorFeedback current I to bring_BIs calculated and output under a predetermined gain. Adder 230 is fast fill current I_FAnd feedback current I_BIs added to calculate and output the control current I to be supplied to the linear valves 40 and 42.

The outline of the braking control in the above configuration will be described. First, before the driver turns on the ignition switch, that is, before energizing each solenoid valve, each solenoid valve is in the state shown in FIG. 1 due to the urging force of the built-in spring. At this time, the atmospheric pressure brake oil from the master cylinder 14 reaches the wheel cylinders 20FR and 20FL of the right front wheel and the left front wheel, respectively, via the right and left electromagnetic on-off valves 22FR and 22FL. On the other hand, the right rear wheel and left rear wheel wheel cylinders 20RR and 20RL are also braked at the same atmospheric pressure as the hydraulic pressure in the reservoir tank 26 via the hydraulic supply / exhaust conduit 28 and the normally open pressure reducing valves 42RR and 42RL. The oil has arrived. At this point, the hydraulic pressure of all four wheel cylinders is atmospheric pressure, and no braking force is generated. However, even before the power is turned on, if the driver depresses the brake pedal 12, the braking force corresponding to the depressing force acts directly on the wheel cylinders 20FR and 20FL of the right front wheel and the left front wheel, and these right front wheel and the left front wheel. A braking force is generated in.

When the driver turns on the ignition switch, the motor 32 is activated as needed, and the accumulator pressure becomes an appropriate high pressure. After that, each solenoid valve is in the state shown in FIG. 1 even when normal driving is started. Subsequently, when the driver steps on the brake pedal 12, the master cylinder 14 is first pushed in, and the communication between the master cylinder 14 and the reservoir tank 26 is cut off. In addition, the right and left electromagnetic on-off valves 22FR and 22FL are closed, the on-off valve 23 is opened, and the communication of atmospheric pressure brake oil from the master cylinder 14 to the wheel cylinders 20FR and 20FL of the right front wheel and the left front wheel is cut off. .. In addition, the pressure reducing valves 42RR and 42RL for the right rear wheel and the left rear wheel are closed, and the four pressure boosting valves 40FR, 40FL, 40RR and 40RL are opened. The opening degree of each solenoid valve is controlled based on the target wheel cylinder hydraulic pressure of each wheel calculated through various calculations described later.

FIG. 3 shows a schematic structure of the drum brake 60, which is the control target of the present embodiment. The drum 62 is rotating with the wheels of the vehicle. When brake oil is supplied from the hydraulic system 100 to the wheel cylinder 20, the piston protrudes and presses the brake shoe 66 with a friction material called a lining against the inner peripheral surface of the drum 62. Braking force is generated by this friction effect. The return spring 68 urges the brake shoes 66 in a direction of attracting each other, and plays a role of pulling the brake shoes 66 away from the inner peripheral surface of the drum 62 at the time of decompression. The distance between the brake shoe 66 and the inner peripheral surface of the drum 62 during decompression is called the shoe clearance 70.

Figure 4 shows the relationship between the wheel cylinder hydraulic pressure and the amount of fluid consumed when the drum brake is activated. In the graph of hydraulic pressure-consumed liquid amount in Fig. 4, the state where the hydraulic pressure change of the wheel cylinder is small although the liquid consumption amount is large is called "low rigidity", and conversely, the liquid consumption amount is small. Regardless of this, the state in which the hydraulic pressure of the wheel cylinder changes significantly is called "high rigidity". In other words, as shown in the graph of FIG. 4, when the inclination is small, it becomes high rigidity, and when the inclination is large, it becomes low rigidity.

Due to the structure of the drum brake 60, it is necessary to overcome the urging force of the return spring 68 before the brake oil is supplied to the wheel cylinder 20 and the brake shoe 66 starts to move. Therefore, the relationship between the wheel cylinder hydraulic pressure and the amount of liquid consumed is drawn as shown in Fig. 4. That is, in the region "A" in the figure, the amount of liquid does not increase because the piston of the wheel cylinder 20 hardly moves until the hydraulic pressure in the wheel cylinder overcomes the set load of the return spring 68, and the graph becomes highly rigid. .. In region "B", until the hydraulic pressure in the wheel cylinder 20 overcomes the urging force of the return spring 68 and the cylinder operates to push the brake shoe 66 to the inner surface of the drum 62 and the shoe clearance 70 is clogged, the wheel cylinder 20 As the amount of liquid consumed increases, the graph becomes less rigid. In region "C", when the shoe clearance 70 is clogged and the brake shoe 66 comes into contact with the inner peripheral surface of the drum 62, the piston of the wheel cylinder 20 hardly moves again, so the amount of liquid does not increase, and the graph becomes highly rigid. Become. That is, the liquid consumption characteristic of the wheel cylinder 20 changes from high rigidity to low rigidity and then to high rigidity again as the hydraulic pressure increases.

As described above, if the rigidity of the hydraulic pressure gradient changes before the drum brake generates the braking force, the control cannot catch up and causes vibration and abnormal noise. In particular, in the portion where the low rigidity region where the shoe clearance is closed changes to the high rigidity region where the braking force is actually generated, the rigidity changes while the amount of liquid is increasing, so that the liquid pressure rises rapidly. However, it may cause vibration and abnormal noise.

Conventionally, in hydraulic brakes, there has been no technique capable of satisfactorily absorbing such changes in rigidity. That is, even if the same control current is applied to the control valve, the brake shoe 66 comes into contact with the inner peripheral surface of the drum 62 due to variations in the spring constant and shoe clearance of the return spring of the drum brake 60, and a braking force is generated. Since the hydraulic pressure at the start of the spring varies, it is difficult to determine the timing to stop the fast fill control current that should be applied while the braking force is not being generated.

Therefore, in this embodiment, by learning the hydraulic pressure at the timing at which the fast-fill control current starts to flow, the timing at which the fast-fill current is stopped can be obtained. Hereinafter, the control method in the embodiment will be described.

FIG. 5 is a flowchart showing the flow of braking control processing according to the present embodiment. This flow is continuously executed at predetermined time intervals. Prior to braking control, when the driver depresses the brake pedal 12, the right and left electromagnetic on-off valves 22FR and 22FL are first closed, the on-off valve 23 is opened, and the master cylinder 14 to the right front wheel and left front wheel wheel cylinder 20FR. , The communication of atmospheric brake fluid to 20FL, and the communication between the master cylinder 14 and the reservoir tank 26 are cut off. In this state, the stroke signal is first read (S10), the master cylinder hydraulic pressure signal is read (S12), and the target deceleration is calculated from these signals by the calculation unit 202 by a known method (S14).

Subsequently, the calculation unit 202 has a target hydraulic pressure P of each wheel with respect to the target deceleration._ref(S16), the hydraulic pressure P in the wheel cylinders 20FR, 20FL, 20RR, 20RL of each wheel_wcIs read from the pressure sensors 44FR, 44FL, 44RR, 44RL (S18). The feedback control unit 222 has a target hydraulic pressure P._refAnd the control hydraulic pressure P, which is the actual wheel cylinder hydraulic pressure_wcFeedback current I from the difference between_BIs calculated (S20).

Next, the fast fill control unit 220 sets the shoe clearance hydraulic pressure P._sIs determined whether or not has already been learned, in other words, whether or not the learned flag set in S28 is "1" (S22). Here, the "shoe clearance hydraulic pressure" is the wheel cylinder hydraulic pressure when it is at the limit of whether or not it is in equilibrium with the urging force of the return spring 68. The flag is "0" and the fast fill control unit 220 is still shoe clearance hydraulic pressure P_sIf you have not learned (NO in S22), apply an amount of brake fluid to the wheel cylinder 20 that will be approximately in equilibrium with the urging force of the return spring 68 (S24). This amount of liquid is determined according to the capacity of the space formed by the wheel cylinder, and is a substantially constant flow rate for drum brakes of the same type, and can be obtained by experiments or the like. Then, the fast fill control unit 220 applies the pressure of the wheel cylinder 20 when this amount of liquid is passed to the shoe clearance hydraulic pressure P._sObtain as (S26). Even if the amount of liquid is the same, the shoe clearance hydraulic pressure P is due to variations in the spring constant of the return spring 68._sTakes a different value for each wheel cylinder. For example, when the spring constant of the return spring 68 is large, the wheel cylinder hydraulic pressure is higher even if the liquid volume is the same. Therefore, if the four wheels of the vehicle are equipped with drum brakes, the fast fill control unit 220 will use the shoe clearance hydraulic pressure P for each wheel._sTo get. The fast fill control unit 220 has a shoe clearance hydraulic pressure P._sMay acquire the hydraulic pressure generated in the wheel cylinder 20 when the hydraulic pressure gradient becomes lower than a predetermined value.

Then, shoe clearance hydraulic pressure P_sSet the learned flag to indicate that has been learned (S28). In the next and subsequent calculations, the shoe clearance hydraulic pressure P that has already been learned_sIs sufficient, so YES is set in the judgment of S22, and the processing of S24 to S28 is skipped.

The fast fill control unit 220 has the target hydraulic pressure P obtained in S16._refBased on the above method, the fast fill current I that reflects the initial rigidity of the wheel cylinder system, etc._FIs calculated (S30). And fast fill current I_FAnd feedback current I_BThe control current I to which is added is supplied to the linear valves 40 and 42 (S32).

Then, the arithmetic unit 202 has the shoe clearance hydraulic pressure P acquired in S26._sPredetermined pressure from P_thOnly determines whether the wheel cylinder hydraulic pressure has risen (S34). This pressure P_thSince there is not much variation in, the same value can be used for drum brakes of the same type, and this value can be obtained by experiments or the like. Pressure P_thIf it has not risen by the amount (NO in S34), control of linear valves 40 and 42 is continued (S32). Pressure P_thWhen it rises by the amount (YES in S34), it comes to the point where the wheel cylinder hydraulic pressure changes from low rigidity to high rigidity, that is, the point where it shifts from "B" to "C" in the graph of Fig. 4, so it is fast. Fill control unit 220 has a fast fill current I_F(S36). That is, after that, the feedback current I_BOnly will flow.

As described above, at the point where the wheel cylinder hydraulic pressure changes from low rigidity to high rigidity, the fast fill current I_FBy stopping, the unnecessary current is eliminated and the brake oil flow rate is reduced, so that the wheel cylinder hydraulic pressure does not rise sharply, and abnormal noise and vibration generated by this can be suppressed.

FIG. 6 is a diagram showing an example of time changes in the wheel cylinder hydraulic pressure and the control current when controlled according to the flowchart of FIG.

First, in the area "A", the time t₁A predetermined amount of liquid is poured from, and the time when this liquid amount is finished flowing t₂Wheel cylinder hydraulic pressure to shoe clearance hydraulic pressure P_sGet as. As mentioned above, this state is whether or not the brake shoe 66 starts to move.

Next, in the region "B", the feedback current I according to the brake stroke_BAnd the fast fill current I that closes the shoe clearance_FThe control current I, which is the sum of the above, is passed. This fast fill current needs to be stopped at an appropriate time. The fast fill control unit 220 has a pressure P._thIncremented minutes (time t₃) To fast fill current I_FTurn off. Shoe clearance hydraulic pressure P_sTime of acquisition t₃After that, as shown in the region "C", the normal feedback current I_BOnly shed.

As described above, according to the present embodiment, in the vehicle braking control device having an electromagnetic valve that controls the hydraulic pressure in response to the braking request, fast fill control is performed in a region where the amount of liquid consumed is large, and the control is started. As a point, the hydraulic pressure when the hydraulic pressure gradient in the relationship between the hydraulic pressure and the consumed liquid amount becomes low rigidity is learned, and the control stop point is set when the hydraulic pressure change from the learned value exceeds a predetermined amount. Set. As a result, the fast-fill current can be appropriately passed, and it is possible to secure responsiveness and suppress abnormal noise and vibration at the same time.

The present invention has been described above based on the embodiments. It is understood by those skilled in the art that these embodiments are examples, and that various modifications are possible for the combination of each component, and that such modifications are also within the scope of the present invention. Hereinafter, such a modification will be described.

In the low pressure region, when the control current for supplying the amount of oil to the wheel cylinder is large, hydraulic pulsation may occur. Shoe clearance hydraulic pressure P when in such a pulsating state_sIf you learn, the time when the fast fill current should be stopped may shift. Therefore, after flowing a predetermined amount of liquid through the wheel cylinder, the control current is stopped for a predetermined time, and when the liquid pressure stabilizes, the shoe clearance hydraulic pressure P_sYou may try to learn.

This is shown in FIG. First, in the area "A", the time t₁From time t₂After flowing a predetermined amount of liquid until, the control current I is once set to 0. That is, the control current is turned off after a predetermined time has elapsed by executing S24 in the flowchart of FIG. 5 (see the area indicated by OFF in the lower figure of FIG. 7). This predetermined time varies depending on the brake type and the characteristics of the brake oil passage, and can be obtained in advance by an experiment or the like. During this period, as shown in the upper figure of FIG. 7, the wheel cylinder hydraulic pressure pulsates, but by waiting for a predetermined time, the wheel cylinder hydraulic pressure becomes almost constant (time t).₃See). Then, the fast fill control unit 220 is set at this time t.₃Wheel cylinder hydraulic pressure in shoe clearance hydraulic pressure P_sGet as. This shoe clearance hydraulic pressure P_sIs the boundary between whether or not the brake shoe 66 starts to move, as described above.

Next, in the region "B", the feedback current I according to the brake pedal effort_BAnd fast fill current I to close the shoe clearance_FThe control current I, which is the sum of the above, is passed. This fast fill current needs to be turned off at an appropriate time. In order to judge this, the fast fill control unit 220 presses the pressure P._thIncremented minutes (time t₄) To fast fill current I_FTurn off. Shoe clearance Time when hydraulic pressure was acquired t₄After that, as shown in the region "C", the normal feedback current I_BOnly shed.

In the embodiment, the fast fill current is suddenly turned off, but it may be gradually reduced. The fast fill current may be gradually decreased linearly, or the rate of the gradual decrease may be increased.

In the embodiment, the leading / trailing type drum brake has been described, but the same applies to other types of drum brakes such as the two-leading type. The present invention can also be applied to a floating type disc brake in which a caliper is operated by a cylinder to pinch a disc rotor to generate a braking force. For example, it is effective when the sliding resistance of the caliper is large and a certain amount of liquid is required before the braking force is generated. For example, when a wheel cylinder system has a large volume such as an opposed caliper, the improvement effect by applying the present invention is large.

<figref num="1">It is an overall block diagram of the vehicle braking control device which concerns on embodiment.</figref><figref num="2">It is an internal block diagram of the arithmetic unit of FIG.</figref><figref num="3">It is a figure which shows the schematic structure of a drum brake.</figref><figref num="4">It is a graph which shows the relationship between the wheel cylinder hydraulic pressure and the consumption liquid amount.</figref><figref num="5">It is a flowchart which carries out the braking control which concerns on embodiment.</figref><figref num="6">It is a graph which shows the relationship between a control current and a wheel cylinder hydraulic pressure.</figref><figref num="7">It is a graph explaining the modification which temporarily turns off a control current.</figref>

Code description

12 Brake pedal, 14 Master cylinder, 20FR, 20FL, 20RR, 20RL Wheel cylinder, 22FR Right electromagnetic on-off valve, 22FL Left electromagnetic on-off valve, 26 Reservoir tank, 32 motor, 34 Oil pump, 40FR, 40FL, 40RR, 40RL Boost valve , 42FR, 42FL, 42RR, 42RL Pressure reducing valve, 44FR, 44FL, 44RR, 44RL Pressure sensor for each wheel, 48FR Right master pressure sensor, 48FL Left master pressure sensor, 50 accumulator, 51 Accumulator pressure sensor, 60 drum brake, 62 drum , 66 Brake shoes, 68 Return springs, 70 shoe clearances, 80 actuators, 100 hydraulic systems, 200 electronic control units, 202 arithmetic units, 204 ROM, 206 RAM, 220 fast fill controls, 222 feedback controls.