JP2010012841A - Electronic control hydraulic braking device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate generation of hunting of control at reduction of an operation amount of braking so as to be passed through a point of inflection on action characteristic for indicating a relationship of a control current of a differential pressure control valve and a differential pressure. <P>SOLUTION: When it is determined as during returning operation of a brake pedal at S14, it is determined as during differential pressure control near the point of inflection at S15 and it is determined that a master cylinder liquid pressure Pmc is during rising at S16, namely, during differential pressure control near the point of inflection, the master cylinder liquid pressure Pmc is rising during returning of a brake pedal, it is regarded as when it arrives at the timing that hunting of control is generated. A pump, i.e., a pressure source of differential pressure control is turned OFF by stopping of a brake actuator 6 at S17. Thereby, hunting of control can be prevented, upper and lower variation of the master cylinder liquid pressure are not also generated, and a driver cannot feel vibration with incompatible sense caused by the variation of the liquid pressure. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electronically controlled hydraulic brake device, and more particularly, to a general brake hydraulic system that guides hydraulic pressure from a braking operation unit such as a master cylinder to a brake operating unit such as a wheel cylinder. The present invention relates to an electronically controlled hydraulic brake device to which a brake actuator capable of increasing pressure control by separating pressure from hydraulic pressure from a braking operation unit is added.

As this type of electronically controlled hydraulic brake device, for example, one as described in Patent Document 1 has been known.
This electronically controlled hydraulic brake device
A differential pressure control valve inserted in a brake pipe that guides hydraulic pressure from a braking operation unit such as a master cylinder to a brake operation unit such as a wheel;
The brake actuator is configured with a pump that sucks brake fluid from the upstream side of the differential pressure control valve and discharges the brake fluid to the downstream side of the differential pressure control valve.
The differential pressure control valve and the pump cooperate to control the differential pressure between the upstream side and the downstream side of the differential pressure control valve so that the braking force by the brake operation unit can be determined.

In the above differential pressure control, the target deceleration (target braking force) is obtained from the operation state of the brake operation unit (the brake pedal depression amount and the output hydraulic pressure of the brake operation unit),
If the target braking force cannot be covered by the sum of the braking force and the regenerative braking force that should be obtained by the output hydraulic pressure of the braking operation unit, the braking force shortage can be reduced by the brake actuator (cooperation between the differential pressure control valve and the pump). Supplemented by the above differential pressure control (downstream hydraulic pressure increase control),
As a result, the target deceleration (target braking force) can be achieved.
JP 2006-096218 A

By the way, the differential pressure control valve is different so that the change rate of the target deceleration (target braking force) during the braking operation is different between the small braking operation region and the large braking operation region, and nevertheless linear control is possible. The differential pressure change ratio with respect to the control input (control current) change is made different between the small braking operation region and the large braking operation region.
Therefore, the differential pressure control valve characteristic that expresses the relationship between the control input and the differential pressure of the differential pressure control valve changes the differential pressure change rate with respect to the control input change at the boundary between the small braking operation region and the large braking operation region. It has an inflection point.

Because of the presence of such an inflection point, when the target differential pressure that decreases along with the reduction of the braking operation amount passes through the inflection point, the control input (control current) of the differential pressure control valve is When the target differential pressure drops to the above inflection point equivalent value, the control input (control current) of the differential pressure control valve hunts across the inflection point. Arise.
Such control hunting causes the upstream hydraulic pressure to fluctuate repeatedly, but the upstream hydraulic pressure fluctuation is kicked back to the braking operation unit, causing vibrations on the feet of the driver who operates the unit. This causes a problem that the driver feels uncomfortable.

The present invention prevents the above control hunting from occurring, prevents the upstream hydraulic pressure from repeatedly fluctuating up and down,
Accordingly, it is an object of the present invention to provide an electronically controlled hydraulic brake device that can eliminate the above-mentioned uncomfortable feeling that vibration is transmitted to a driver's foot or the like who operates a braking operation unit.

For this purpose, an electronically controlled hydraulic brake device according to the invention is constructed as described in claim 1.
First of all, the electronic control hydraulic brake device will be explained.
A differential pressure control valve is inserted in the brake piping that guides the hydraulic pressure from the brake operation unit to the brake operation unit.
Brake fluid is sucked from an upstream brake piping portion closer to the braking operation unit than the differential pressure control valve, and this brake fluid is discharged to a downstream brake piping portion closer to the brake operation unit than the differential pressure control valve. With a pump to play,
The differential pressure control valve and the pump cooperate to control the differential pressure between the upstream brake piping portion and the downstream brake piping portion so that the braking force by the brake operating unit can be determined. is there.

The present invention is directed to such an electronically controlled hydraulic brake device.
An inflection point vicinity differential pressure control detection means for detecting that the differential pressure control is in the vicinity of the inflection point where the differential pressure change ratio with respect to the control input change of the differential pressure control valve changes;
Braking operation amount decrease detection means for detecting that the braking operation amount of the braking operation unit is decreased;
Upstream fluid pressure increase detection means for detecting an increase in upstream fluid pressure from the braking operation unit to the upstream brake piping portion;
In response to signals from these three means, during the differential pressure control near the inflection point, the differential pressure control is performed at the start of hunting in which the upstream hydraulic pressure rises even though the braking operation amount is reduced. It is characterized by a configuration provided with a differential pressure control prohibiting means for prohibiting the pressure.

According to such an electronically controlled hydraulic brake device of the present invention,
During the differential pressure control near the inflection point where the differential pressure change ratio changes with respect to the control input change of the differential pressure control valve, the braking operation amount of the braking operation unit has decreased, but the upstream brake piping from the braking operation unit At the start of hunting when the upstream hydraulic pressure to the part rises, differential pressure control by the cooperation of the differential pressure control valve and the pump is prohibited.
This differential pressure control is forced to avoid hunting of the control input of the differential pressure control valve across the inflection point, and it is also possible to avoid repeated vertical fluctuations in the upstream hydraulic pressure accompanying this hunting. .
Therefore, it is possible to eliminate the uncomfortable feeling that the up-and-down fluctuation of the upstream hydraulic pressure is kicked back as vibration on the driver's foot or the like who operates the braking operation unit.

Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.
FIG. 1 is a system diagram of an electronically controlled hydraulic brake device according to an embodiment of the present invention.
In this embodiment, although not shown, the regenerative energy is efficiently controlled by electronically controlling the brake fluid pressure so as to achieve the target deceleration (target braking force) in combination with the regenerative brake using the AC synchronous motor. It is configured as an electronically controlled hydraulic brake device that is advantageous for application to a “regenerative cooperative brake control system” that is to be recovered.

In FIG. 1, 1 is a brake pedal that is depressed according to the target deceleration (target braking force) of the vehicle desired by the driver.
The pedal force of the brake pedal 1 is boosted by the vacuum booster 2, and the master cylinder 3 is driven by the boosted force to push the unillustrated piston cup of the master cylinder 3. The hydraulic pressure Pmc is output to one brake pipe 4a and the other brake pipe 4b in the X pipe.
Therefore, the vacuum booster 2 and the master cylinder 3 correspond to the braking operation unit in the present invention.

One brake pipe 4a constitutes a brake hydraulic system for the right front wheel wheel cylinder 5FR and the left rear wheel wheel cylinder 5RL which are brake operation units,
The other brake pipe 4b constitutes a brake hydraulic system for the left front wheel wheel cylinder 5FL and the right rear wheel wheel cylinder 5RR which are brake operation units.
Therefore, one brake pipe 4a and the other brake pipe 4b are respectively connected to the right front wheel wheel cylinder 5FR and the left rear wheel wheel cylinder 5RL, the left front wheel wheel cylinder 5FL and the right rear through the brake actuator 6 as described below. Connect to wheel wheel cylinder 5RR.

The brake actuator 6 includes a differential pressure control valve 11a, 11b, a pressure increasing valve 12FR, 12RL, 12FL, 12RR, a pressure reducing valve 13FR, 13RL, 13FL, 13RR, a reservoir 14a, 14b, and a pump 15a, 15b. It consists of valves 16a and 16b.
The differential pressure control valves 11a and 11b are normally open proportional solenoid valves, which will be described in detail later. As the control current to the solenoid increases, the opening degree is reduced from the fully open state.
The booster valves 12FR, 12RL, 12FL, 12RR are normally open solenoid valves, and are closed by energizing the solenoid.
The pressure reducing valves 13FR, 13RL, 13FL, 13RR are normally closed solenoid valves, which are opened by energizing the solenoid.

One brake pipe 4a extending from the master cylinder 3 is connected to the input port of the differential pressure control valve 11a.
The pipe 17a extending from the output port of the differential pressure control valve 11a is connected to the input port of the pressure booster valve 12FR by the pipe 18FR, and is connected to the input port of the pressure booster valve 12RL by the pipe 18RL.
The output port of the booster valve 12FR is connected to the right front wheel wheel cylinder 5FR via a pipe 19FR, and the output port of the booster valve 12RL is connected to the left rear wheel wheel cylinder 5RL via a pipe 19RL.

The pipes 19FR and 19RL are connected to a common pipe 20a via pressure reducing valves 13FR and 13RL, respectively, and the pipe 20a is connected to a pipe 21a between the output port of the reservoir 14a and the suction port of the pump 15a.
The input port of the reservoir 14a is connected to one master cylinder hydraulic pipe 4a via the pipe 22a.
The discharge port of the pump 15a is connected to the pipe 17a by the pipe 23a, and the check valve 16a is inserted into the pipe 23a.
The check valve 16a is arranged in a direction that allows liquid flow from the discharge port of the pump 15a to the pipe 17a and prevents reverse liquid flow.

The other brake pipe 4b extending from the master cylinder 3 is connected to the input port of the differential pressure control valve 11b.
The pipe 17b extending from the output port of the differential pressure control valve 11b is connected to the input port of the pressure booster valve 12FL by the pipe 18FL, and is connected to the input port of the pressure booster valve 12RR by the pipe 18RR.
The output port of the pressure booster valve 12FL is connected to the left front wheel wheel cylinder 5FL via a pipe 19FL, and the output port of the pressure booster valve 12RR is connected to the right rear wheel wheel cylinder 5RR via a pipe 19RR.

The pipes 19FL and 19RR are connected to a common pipe 20b via pressure reducing valves 13FL and 13RR, respectively, and the pipe 20b is connected to a pipe 21b between the output port of the reservoir 14b and the suction port of the pump 15b.
The input port of the reservoir 14b is connected to one master cylinder hydraulic pipe 4b through the pipe 22b.
The discharge port of the pump 15b is connected to the pipe 17b by the pipe 23b, and the check valve 16b is inserted into the pipe 23b.
The check valve 16b is arranged in a direction that allows liquid flow from the discharge port of the pump 15b to the pipe 17b and prevents reverse liquid flow.

The hydraulic brake system described above with reference to FIG. 1 is controlled by a brake controller 31 shown in a block diagram in FIG.
The brake controller 31 includes a target deceleration calculation unit 32 and a regenerative cooperative brake control unit 33.
Signals from a pedal stroke sensor 34 and a pressure sensor 35, which are provided as shown in FIG. 1 and detect the depression stroke amount St of the brake pedal 1 and the master cylinder hydraulic pressure Pmc, respectively, are input to the target deceleration calculation unit 32.
The target deceleration calculation unit 32 estimates the braking operation force (brake pedal depression force) F by the driver from the depression stroke amount St of the brake pedal 1 detected by the sensors 34 and 35 and the master cylinder hydraulic pressure Pmc, and applies this braking A target deceleration of the vehicle desired by the driver is calculated from the operating force F, and a target braking force Tbo for realizing the target deceleration is obtained.

In calculating the target deceleration, the reason for using both the stroke amount St of the brake pedal 1 and the master cylinder hydraulic pressure Pmc is as follows:
In the initial stage of the braking operation, the change in the master cylinder hydraulic pressure Pmc is small, and it is necessary to estimate the braking operation force F with an emphasis on the pedal stroke amount St.
This is because in the latter half of the braking operation, the change in the pedal stroke amount St is small, and it is necessary to estimate the braking operation force F with an emphasis on the master cylinder hydraulic pressure Pmc.

The regenerative cooperative brake control unit 33 includes the target braking force Tbo obtained by the target deceleration calculating unit 32, the master cylinder hydraulic pressure Pmc detected by the sensor 35, a signal from the vehicle speed sensor 36 that detects the vehicle speed VSP, A signal such as the effective regenerative braking force from the hybrid vehicle is input.
The regenerative cooperative brake control unit 33 obtains the maximum possible regenerative braking force based on the input information, and the braking force Tmc that can be generated by the master cylinder hydraulic pressure Pmc (if Tmc is zero, the maximum possible When the target braking force Tbo can be provided (only by the regenerative braking force), the hybrid vehicle is commanded as a regenerative braking force command value Tmg, which is a difference value obtained by subtracting the braking force Tmc by the master cylinder hydraulic pressure Pmc from the target braking force Tbo.

In this case, the differential pressure control by the cooperation of the pumps 15a, 15b and the differential pressure control valves 11a, 11b, that is, the pressure increase control of the downstream brake pipe portion from the differential pressure control valves 11a, 11b to the corresponding wheel cylinder is performed. Because it is unnecessary,
The regenerative cooperative brake control unit 33 sets the pump ON / OFF command to the pumps 15a, 15b to “OFF” and sets the differential pressure control valve control current I to the differential pressure control valves 11a, 11b to zero.

The operation of the hydraulic brake system in FIG. 1 at this time is as follows.
Since the braking action by the master cylinder hydraulic pressure Pmc from the master cylinder hydraulic pipes 4a and 4b is the same, only the braking action by the master cylinder hydraulic pressure Pmc from one master cylinder hydraulic pipe 4a is representative here. Explained.

Since the differential pressure control valve control current I to the differential pressure control valve 11a is zero as described above, the differential pressure control valve 11a is kept fully open.
Therefore, the master cylinder hydraulic pressure Pmc from the pipe 4a reaches the pipes 18FR and 18RL via the differential pressure control valve 11a and the pipe 17a.
The master cylinder hydraulic pressure Pmc to the pipe 18FR flows through the normally open pressure increasing valve 12FR and the pipe 19FR, and is supplied to the right front wheel cylinder 5FR as the wheel cylinder hydraulic pressure Pwc, so that the right front wheel can be braked.
The master cylinder hydraulic pressure Pmc to the pipe 18RL flows through the normally open pressure increasing valve 12RL and the pipe 19RL, and is supplied to the left rear wheel wheel cylinder 5RL as the wheel cylinder hydraulic pressure Pwc, so that the left rear wheel can be braked.

Incidentally, the braking operation unit consisting of the vacuum booster 2 and the master cylinder 3 generates a master cylinder hydraulic pressure Pmc that generates a braking force as illustrated by Tmc in FIG. 3 with respect to the braking operation force F estimated as described above. The configuration is as follows.
Thus, as described above, the braking force Tmc when the master cylinder hydraulic pressure Pmc is supplied to the right front wheel cylinder 5FR and the left rear wheel cylinder 5RL as it is as the wheel cylinder hydraulic pressure Pwc corresponds to the braking operation force F. Energy recovery efficiency is increased by making the regenerative braking force as small as possible so as to be smaller than the target braking force (target deceleration).

  During the above braking, when the right front wheel braked by the wheel cylinder 5FR and / or the left rear wheel braked by the wheel cylinder 5RL tend to lock, the corresponding pressure increase valve 12FR and / or 12RL is turned ON. The above-mentioned locking tendency of the corresponding wheel is eliminated by closing and holding the wheel cylinder hydraulic pressure Pwc, or opening the corresponding pressure reducing valve 13FR and / or 13RL by turning ON to reduce the wheel cylinder hydraulic pressure Pwc.

When the rotation of the corresponding wheel is restored due to the elimination of this locking tendency, the corresponding pressure reducing valve 13FR and / or 13RL is closed by turning OFF, and the corresponding pressure increasing valve 12FR and / or 12RL is opened by turning OFF to increase the wheel cylinder hydraulic pressure Pwc. Press.
By repeating this anti-skid cycle, the slip ratio of the right front wheel and / or the left rear wheel is kept at the ideal slip ratio (slip ratio of about 15% at which the friction coefficient with the road surface is maximum), and the braking distance is minimized. Perform anti-skid control.

  Incidentally, the right front wheel wheel cylinder 5FR and the left rear wheel wheel cylinder 5RL are individually controlled by the wheel cylinder hydraulic pressure Pwc, so the wheel cylinder hydraulic pressure Pwc of the right front wheel wheel cylinder 5FR and the wheel cylinder of the left rear wheel wheel cylinder 5RL Although the hydraulic pressures Pwc are different from each other, in FIG. 1, the wheel cylinder hydraulic pressures Pwc of both wheels are indicated by the same reference numerals for convenience.

The regenerative cooperative brake control unit 33 in FIG. 2 uses the maximum possible regenerative braking force and the braking force Tmc that can be generated by the master cylinder hydraulic pressure Pmc (if Tmc is zero, only the maximum possible regenerative braking force). When the power Tbo cannot be provided, the hybrid vehicle is commanded with the maximum possible regenerative braking force as the regenerative braking force command value Tmg.
Further, as illustrated in FIG. 3 for scenes 1 and 2, the regenerative cooperative brake control unit 33 obtains the braking force Tmc based on the master cylinder hydraulic pressure Pmc and the above regenerative braking force command value Tmg from the target braking force Tbo. Find the braking force shortage Tup obtained by subtracting,
This braking force shortage Tup is controlled by differential pressure control by the cooperation of the differential pressure control valve 11a and the pump 15a, that is, pressure increase control of the downstream brake piping part from the differential pressure control valves 11a, 11b to the corresponding wheel cylinder. To supplement, the pump ON / OFF command to the pumps 15a and 15b is turned “ON”, and the differential pressure control valve control current I to the differential pressure control valves 11a and 11b is determined as follows.

When determining the differential pressure control valve control current I, the regenerative cooperative brake control unit 33 increases the wheel cylinder hydraulic pressure Pwc necessary to compensate for the insufficient braking force Tup, that is, the master cylinder that is the upstream hydraulic pressure. The target differential pressure ΔP between the hydraulic pressure Pmc and the wheel cylinder hydraulic pressure Pwc which is the downstream hydraulic pressure is obtained,
Based on the operating characteristics of the differential pressure control valves 11a and 11b illustrated in FIG. 4, the control current I necessary to generate the target differential pressure ΔP is retrieved, and this is used as a command value to control the differential pressure control valves 11a and 11b. To supply.

The differential pressure control valve characteristics of FIG. 4 are the control current I supplied to the differential pressure control valves 11a and 11b, and when this current I is supplied, the differential pressure control valves 11a and 11b transfer the wheel cylinder hydraulic pressure Pwc to the master cylinder. It shows what kind of pressure difference ΔP is used to increase the hydraulic pressure Pmc.
By the way, the differential pressure control valve 11a is different so that the change rate of the target deceleration (target braking force Tbo) during the braking operation is different between the small braking operation region and the large braking operation region, and nevertheless linear control is possible. , 11b are configured such that the change rate of the differential pressure ΔP with respect to the change of the control current I is different between a small braking operation region and a large braking operation region as illustrated in FIG.
Therefore, the differential pressure control valve characteristic representing the relationship between the control current I of the differential pressure control valves 11a and 11b and the differential pressure ΔP is as shown in FIG. 4 at the boundary between the small braking operation region and the large braking operation region. It has an inflection point Z at which the differential pressure change rate with respect to the control current change changes.

Hereinafter, the differential pressure control operation performed in the hydraulic brake system of FIG. 1 will be described in detail.
Since the differential pressure control action of the brake hydraulic pressure system related to the master cylinder hydraulic pressure pipe 4a and the differential pressure control action of the brake hydraulic pressure system related to the master cylinder hydraulic pressure pipe 4b are the same,
Here, only the differential pressure control action of the brake hydraulic pressure system related to one master cylinder hydraulic pressure pipe 4a will be representatively described.

The pump 15a is operated by the above “ON” command. The pump 15a sucks in brake fluid from the pipelines 4a and 22a through the reservoir 14a and the pipe 21a, and the check valve 16a is inserted into the brake fluid. The brake fluid discharged to the pipe 17a through the pipe 23a reaches the pipes 18FR and 18RL.
The brake fluid to the pipe 18FR is supplied to the right front wheel cylinder 5FR via the normally open pressure increasing valve 12FR and the pipe 19FR, and the wheel cylinder hydraulic pressure Pwc to this can be increased.
The brake fluid to the pipe 18RL is supplied to the left rear wheel wheel cylinder 5RL via the normally open pressure increasing valve 12RL and the pipe 19RL, and the wheel cylinder hydraulic pressure Pwc to this can be increased.

The degree of pressure increase of the right front wheel and left rear wheel wheel cylinder hydraulic pressure Pwc is determined by the opening of the differential pressure control valve 11a that responds to the control current I,
Accordingly, the wheel cylinder hydraulic pressure Pwc can be increased by the target differential pressure ΔP with respect to the master cylinder hydraulic pressure Pmc.
As a result, the braking force of the right front wheel and the left rear wheel is increased by the braking force deficiency Tpu shown in FIG. 3, and the target braking force Tbo (target deceleration) can be realized in combination with the regenerative cooperative brake control described above.

  Incidentally, as described above with reference to FIG. 4, there is an inflection point Z in the differential pressure control valve characteristic representing the relationship between the control current I of the differential pressure control valves 11a and 11b and the differential pressure ΔP. Since the change rate of the differential pressure ΔP with respect to the change of the control current I is different before and after the crossing, there is a concern that the following problems may occur.

While the brake pedal stroke amount St is reduced as shown in FIG. 5, the target differential pressure ΔP, which decreases along with this, starts from the instant t0 in FIG. The control current I of 11a and 11b rapidly decreases as shown in FIG.
The sudden decrease in the control current I increases the opening of the differential pressure control valves 11a and 11b to reduce the differential pressure, so that the downstream side (wheel cylinder side) and the upstream side (master cylinder) of the differential pressure control valves 11a and 11b. As a result, the master cylinder hydraulic pressure Pm, which is the upstream hydraulic pressure, is increased as shown in FIG. 5 after the instant t1.
The increase in the master cylinder hydraulic pressure Pmc increases the target deceleration (target braking force Tbo) obtained from the master cylinder hydraulic pressure Pmc, even though the brake pedal stroke amount St is decreasing. In response to the increase in the target differential pressure ΔP, the control current I of the differential pressure control valves 11a and 11b is increased for valve closing as after the instant t2 in FIG.

In the closing operation of the differential pressure control valves 11a and 11b due to the increase of the control current I, the pump cylinders 15a and 15b suck in the brake fluid from the upstream side of the differential pressure control valves 11a and 11b, and the master cylinder fluid which is the upstream hydraulic pressure The pressure Pmc is decreased as shown after the instant t3 in FIG.
The decrease in the master cylinder hydraulic pressure Pmc decreases the target deceleration (target braking force Tbo) obtained from the master cylinder hydraulic pressure Pmc, and the differential pressure control valve in response to the decrease in the target differential pressure ΔP. The control current I of 11a and 11b is decreased for valve opening as after the instant t4 in FIG.

The decrease in the control current I increases the opening of the differential pressure control valves 11a and 11b to reduce the differential pressure, so that the downstream side (wheel cylinder side) and the upstream side (master cylinder side) of the differential pressure control valves 11a and 11b. As a result, the master cylinder hydraulic pressure Pm, which is the upstream hydraulic pressure, is increased as shown in FIG. 5 after the instant t5.
The increase in the master cylinder hydraulic pressure Pm increases the target deceleration (target braking force Tbo) obtained from the master cylinder hydraulic pressure Pm, even though the brake pedal stroke amount St is decreasing. In response to the increase in the target differential pressure ΔP, the control current I of the differential pressure control valves 11a and 11b is increased for valve closing as after the instant t6 in FIG.

In the closing operation of the differential pressure control valves 11a and 11b due to the increase of the control current I, the pump cylinders 15a and 15b suck in the brake fluid from the upstream side of the differential pressure control valves 11a and 11b, and the master cylinder fluid which is the upstream hydraulic pressure The pressure Pmc is decreased as shown after the instant t7 in FIG.
The decrease in the master cylinder hydraulic pressure Pmc decreases the target deceleration (target braking force Tbo) obtained from the master cylinder hydraulic pressure Pmc, and the differential pressure control valve in response to the decrease in the target differential pressure ΔP. The control current I of 11a and 11b is reduced for valve opening as after the instant t8 in FIG.

By repeating the above operation, the differential pressure control valves 11a and 11b are reduced after the instant t0 in FIG. 5 when the target differential pressure ΔP has decreased to a value corresponding to the inflection point Z in FIG. 4 due to the decrease in the brake pedal stroke amount St. The control current I hunts as shown in the figure across the inflection point Z, and accordingly, the master cylinder hydraulic pressure Pmc, which is the upstream hydraulic pressure, repeats vertical fluctuations as shown in FIG.
By the way, the vertical fluctuation of the master cylinder Pmc is kicked back to the brake pedal 1 through the master cylinder 3, and is transmitted as vibration to the driver's foot or the like who operates the brake pedal 1, causing the driver to feel uncomfortable.

In this embodiment, the above control hunting is not caused to occur, and the master cylinder hydraulic pressure Pmc is not repeatedly changed up and down, so that the master cylinder hydraulic pressure Pmc is repeatedly changed up and down. To eliminate the uncomfortable feeling that fluctuations are transmitted to the driver as vibration,
The brake controller 31 in FIG. 2 executes the control program shown in FIG. 6 to perform the following differential pressure control.

First, in step S11, the master cylinder hydraulic pressure Pmc and the depression stroke amount St of the brake pedal 1 are read.
In step S12, the target deceleration of the vehicle is calculated from the master cylinder hydraulic pressure Pmc and the brake pedal depression stroke amount St, and the target braking force Tbo of the vehicle necessary to achieve this is obtained.

In step S13, the control current I of the differential pressure control valves 11a and 11b is obtained by the same calculation as described above, and commanded to the differential pressure control valves 11a and 11b.
That is, the increase in the wheel cylinder hydraulic pressure Pwc necessary to compensate for the braking force deficiency Tup described above with reference to FIG. 3, that is, the upstream hydraulic pressure, the master cylinder hydraulic pressure Pmc, and the downstream hydraulic pressure. Find the target differential pressure ΔP between the wheel cylinder hydraulic pressure Pwc,
Based on the operating characteristics of the differential pressure control valves 11a and 11b illustrated in FIG. 4, the control current I necessary to generate the target differential pressure ΔP is retrieved, and this is used as a command value to control the differential pressure control valves 11a and 11b. To supply.

Steps S11 to S13 are the above-described normal differential pressure control, but the control proceeds to step S14 and subsequent steps for preventing the above-described hunting.
In step S14 corresponding to the brake operation amount decrease detection means, the brake pedal stroke amount St is compared with St (previous value), and the brake pedal 1 is returned depending on whether St-St (previous value) <0 or not. Check if it is in the middle.
If the brake pedal 1 is not being returned, the above-described hunting problem does not occur and the control is terminated as it is.

When it is determined in step S14 that the brake pedal 1 is being returned, the differential pressure control current I obtained in step S13 is the inflection point Z in FIG. Check if it has dropped to a nearby value.
If the differential pressure control current I has not decreased to a value in the vicinity of the inflection point Z, the above-described hunting problem does not occur, and the control is terminated as it is.

If it is determined in step S15 that the differential pressure control current I has decreased to a value near the inflection point Z, the master cylinder hydraulic pressures Pmc and Pmc (previous values) are determined in step S16 corresponding to the upstream hydraulic pressure increase detection means. To check whether or not the master cylinder hydraulic pressure Pmc is increasing depending on whether or not Pmc−Pmc (previous value)> 0.
If the master cylinder hydraulic pressure Pmc is not increasing, the timing for generating the above-described hunting has not yet been reached, and the control is terminated as it is.

When it is determined in step S16 that the master cylinder hydraulic pressure Pmc is increasing, the timing at which the above hunting occurs is reached in combination with the brake pedal return determination in step S14 and the inflection point vicinity determination in step S15. From what can be considered
Control is advanced to step S17, the brake actuator 6 in FIG. 1 is stopped, and the pump ON / OFF command in FIG. 2 is set to “OFF”.
Accordingly, step S17 corresponds to the differential pressure control prohibiting means in the present invention.

According to the differential pressure control in steps S14 to S17 in the present embodiment, the following operational effects can be obtained.
Explaining based on FIG. 7, while reducing the brake pedal stroke amount St as shown in the figure, it is determined that the differential pressure control near the inflection point Z is made at the instant t1 (step S15). During the differential pressure control near Z, it is determined that the master cylinder hydraulic pressure Pmc has increased even though the brake pedal stroke amount St has decreased (step S14) (step S16).
After this time, the brake actuator 6 is stopped and the pump ON / OFF command is set to “OFF” (step S17).

Therefore, after the hunting start determination time t2, the differential pressure control valve control current I does not hunt as indicated by the solid line, and the master cylinder hydraulic pressure Pmc does not fluctuate up and down as indicated by the solid line.
When normal differential pressure control is forced after t2 at the time of hunting start determination, as described above with reference to FIG. 5 and as indicated by a broken line in FIG. 7, the differential pressure control valve control current I hunts across the inflection point. With this hunting, the master cylinder hydraulic pressure Pmc repeatedly fluctuates up and down, and this hydraulic pressure fluctuation causes the driver to feel kicked back as vibration.
However, according to this embodiment, after the hunting start determination time t2, the brake actuator 6 is stopped and the pumps 15a and 15b are turned off, so that there is no fluctuation in the master cylinder hydraulic pressure Pmc. However, it is possible to avoid the uncomfortable feeling that the driver kicks back as vibration.

In this embodiment, when determining that the differential pressure is being controlled near the inflection point Z,
The differential pressure control valve characteristics shown in FIG. 4 showing the relationship between the braking operation amount (brake pedal stroke amount St, master cylinder hydraulic pressure Pmc) and the control current I of the differential pressure control valves 11a and 11b and the differential pressure ΔP. Use
The target differential pressure ΔP is obtained from the braking operation amount (brake pedal stroke amount St, master cylinder hydraulic pressure Pmc), and the control current I of the differential pressure control valves 11a, 11b that realizes the target differential pressure ΔP is shown in FIG. In order to determine that the differential pressure control current I is in the vicinity of the inflection point Z in FIG.
This determination can be made only from signals and stored data used in normal differential pressure control, which is very advantageous in terms of cost.

Also, when obtaining the target differential pressure ΔP from the braking operation amount (brake pedal stroke amount St, master cylinder hydraulic pressure Pmc), as described above with reference to FIG. 3, the braking operation amount (brake pedal stroke amount St, master cylinder hydraulic pressure Pmc). The wheel cylinder hydraulic pressure required to supplement the braking force deficiency Tpu obtained by subtracting the braking force Tmc obtained by the master cylinder hydraulic pressure Pmc and the regenerative braking force Tmg from the target braking force Tbo desired by the driver In order to set the amount of increase in Pwc as the target differential pressure ΔP,
The target differential pressure ΔP can be obtained only from the signal and stored data used for normal differential pressure control, which is very advantageous in terms of cost.

The above differential pressure control continues until the brake pedal 1 is depressed again. When the brake pedal 1 is depressed again, this is detected in step S18 in FIG. Proceed to the return loop.
In step S19, a re-determination determination as to whether or not the driver has actually re-depressed the brake pedal 1 in response to whether or not the re-depression speed of the brake pedal 1 is equal to or higher than the set speed α is erroneous. Perform with high accuracy without judgment.
Before the re-depression determination is made, the driver does not actually depress the brake pedal 1 again because he / she really wants to re-brake, and the above-described differential pressure control needs to be continued.

After it is determined in step S19 that the brake pedal 1 is depressed again, in step S20, the brake actuator 6 is operated to turn ON / OFF the pumps 15a and 15b, and the differential pressure control valve. The control current I to 11a and 11b is set to the maximum control value.
Thus, the reason why the control current I to the differential pressure control valves 11a and 11b is maximized is that the wheel cylinder hydraulic pressure Pwc that has been suppressed by the differential pressure control for preventing hunting is quickly controlled to the normal control value. This is for increasing the normal control return response.

The actual deceleration (negative value) of the vehicle was obtained in step S12 by the operation of the brake actuator 6 (pumps 15a and 15b being turned on) and the wheel cylinder hydraulic pressure Pwc increased by the maximum value command of the differential pressure control current I. Head towards the target deceleration.
In step S21, it is checked whether or not the actual deceleration (negative value) of the vehicle has reached the target deceleration. Control is returned to step S20 until the actual deceleration (negative value) reaches the target deceleration. The wheel cylinder hydraulic pressure Pwc is further increased toward the normal control value.

When the actual deceleration (negative value) of the vehicle reaches the target deceleration due to the increase of the wheel cylinder hydraulic pressure Pwc to the normal control value, step S21 determines this and advances the control to step S22, where the differential pressure is determined. The control current I to the control valves 11a and 11b is returned to the normal differential pressure control using the normal control value.
Therefore, the return to the normal differential pressure control can be smoothly performed at a timing when there is no braking force step.

  Therefore, steps S18 to S22 also constitute the differential pressure control prohibiting means in the present invention, as in step S17.

1 is a system diagram of an electronically controlled hydraulic brake device according to an embodiment of the present invention. It is a block diagram according to a function of a brake controller in the electronically controlled hydraulic brake device. FIG. 2 is a braking force change characteristic diagram of the hydraulic brake system shown in FIG. FIG. 2 is an operation characteristic diagram of a differential pressure control valve in the hydraulic brake system shown in FIG. 5 is a time chart showing a control hunting phenomenon that occurs due to the differential pressure control valve operating characteristics shown in FIG. 6 is a flowchart showing a differential pressure control program for eliminating the hunting phenomenon shown in FIG. FIG. 7 is a time chart showing a suppression state of a hunting phenomenon by differential pressure control shown in FIG. 6. FIG.

Explanation of symbols

1 Brake pedal 2 Vacuum booster (braking operation unit)
3 Master cylinder (braking operation unit)
4a One master cylinder hydraulic piping
4b Hydraulic piping of the other master cylinder
5FL, 5FR Left and right front wheel wheel cylinder
5RL, 5RR Left and right rear wheel wheel cylinder 6 Brake actuator
11a, 11b Differential pressure control valve
12FL, 12FR Booster valve for left and right front wheel wheel cylinders
12RL, 12RR Booster valve for left and right wheel cylinders
13FL, 13FR Pressure reducing valve for left and right front wheel cylinders
13RL, 13RR Left and right rear wheel wheel cylinder pressure reducing valve
14a, 14b Reservoir
15a, 15b pump
16a, 16b Check valve
31 Brake controller
32 Target deceleration calculation unit
33 Regenerative cooperative brake control unit
34 Pedal stroke sensor
35 Pressure sensor
36 Vehicle speed sensor

Claims (8)

A differential pressure control valve is inserted in the brake piping that guides the hydraulic pressure from the brake operation unit to the brake operation unit.
Brake fluid is sucked from an upstream brake piping portion closer to the braking operation unit than the differential pressure control valve, and this brake fluid is discharged to a downstream brake piping portion closer to the brake operation unit than the differential pressure control valve. With a pump to play,
Electronic control that determines the braking force by the brake operation unit by controlling the differential pressure between the upstream brake piping portion and the downstream brake piping portion by the cooperation of the differential pressure control valve and the pump. In the hydraulic brake device,
An inflection point vicinity differential pressure control detection means for detecting that the differential pressure control is in the vicinity of the inflection point where the differential pressure change ratio with respect to the control input change of the differential pressure control valve changes;
Braking operation amount decrease detection means for detecting that the braking operation amount of the braking operation unit is decreased;
Upstream fluid pressure increase detection means for detecting an increase in upstream fluid pressure from the braking operation unit to the upstream brake piping portion;
In response to signals from these three means, during the differential pressure control near the inflection point, the differential pressure control is performed at the start of hunting in which the upstream hydraulic pressure rises even though the braking operation amount is reduced. An electronically controlled hydraulic brake device, characterized by comprising differential pressure control prohibiting means for prohibiting pressure. In the electronically controlled hydraulic brake device according to claim 1,
The inflection point vicinity differential pressure control detection means is based on the braking operation amount and the differential pressure control valve characteristic representing the relationship between the control input of the differential pressure control valve and the differential pressure. An electronically controlled hydraulic brake device that detects that a differential pressure is being controlled. In the electronically controlled hydraulic brake device according to claim 2,
The inflection point vicinity differential pressure control detection means obtains a target value of the differential pressure from the braking operation amount, and obtains a control input of the differential pressure control valve that realizes the target differential pressure from the differential pressure control valve characteristic. The electronically controlled hydraulic brake device is characterized in that when the control input of the differential pressure control valve is in the vicinity of the inflection point, it is determined that the differential pressure is being controlled in the vicinity of the inflection point. In the electronically controlled hydraulic brake device according to claim 3,
The inflection point vicinity differential pressure control detection means is a downstream necessary for compensating for an insufficient braking force obtained by subtracting the braking force to be obtained by the upstream hydraulic pressure from the target braking force corresponding to the braking operation amount. An electronically controlled hydraulic brake device characterized in that a side hydraulic pressure increase amount is set as the target differential pressure. The electronically controlled hydraulic brake device according to claim 3, wherein the target braking force corresponding to the braking operation amount is realized by cooperation with a regenerative braking force.
The inflection point vicinity differential pressure control detecting means is a downstream necessary for compensating for a shortage of braking force obtained by subtracting the braking force to be obtained by the upstream hydraulic pressure and the regenerative braking force from the target braking force. An electronically controlled hydraulic brake device characterized in that a side hydraulic pressure increase amount is set as the target differential pressure. In the electronically controlled hydraulic brake device according to any one of claims 1 to 5,
The differential pressure control prohibiting means temporarily closes the differential pressure control valve to release the prohibition of the differential pressure control in response to the braking operation amount changing from a decrease to an increase. An electronically controlled hydraulic brake device characterized by rapidly increasing the downstream hydraulic pressure. In the electronically controlled hydraulic brake device according to claim 6,
The differential pressure control prohibiting unit determines that the braking operation amount has changed from a decrease to an increase when the increasing speed of the braking operation amount is equal to or higher than a set value, and cancels the prohibition of the differential pressure control. An electronically controlled hydraulic brake device. In the electronically controlled hydraulic brake device according to claim 6 or 7,
The differential pressure control prohibiting means continues the temporary full closing of the differential pressure control valve until the vehicle braking force reaches a target braking force corresponding to the braking operation amount, and thereafter controls the differential pressure control valve normally. An electronically controlled hydraulic brake device characterized by that

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