JPH0951603A - Electric vehicle braking system - Google Patents

Abstract

(57) [Abstract] [Problem] To eliminate the intrusion and hardness of the brake pedal. A flow rate at a regenerative hydraulic valve is estimated based on a master cylinder pressure and a wheel cylinder pressure, and when the estimated flow rate reaches a predetermined value s0, introduction of an initial hydraulic pressure to a wheel cylinder is terminated (G). After that, the valve opening value of the regenerative hydraulic valve is gradually increased to control the stroke smoothly (GF). It is possible to obtain stroke-to-pedal force characteristics similar to the characteristics of the hydraulic brake alone by using regeneration in combination. At that time, a stroke simulator is not necessary,
In addition, good regeneration can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking device for an electric vehicle that brakes a vehicle by using both fluid pressure braking and regenerative braking.

[0002]

2. Description of the Related Art In an electric vehicle, it is possible to use both fluid pressure braking and regenerative braking, and the energy efficiency of the vehicle can be kept good by preferentially using regenerative braking over fluid pressure braking. It is possible. In order to preferentially use regenerative braking over fluid pressure braking, it is necessary to interrupt the transmission of fluid pressure to the drive wheels while the braking force required by the vehicle operator is small, for example, when the brake pedal is shallowly depressed. There is. To this end, as disclosed in, for example, Japanese Patent Application Laid-Open No. 5-176407, braking is performed between a master cylinder that generates hydraulic pressure according to the depression of a brake pedal and a wheel cylinder that applies hydraulic braking force to driving wheels. A valve that shuts off the introduction of oil may be provided. This valve is closed in the area where the regenerative braking force is preferentially used. Also, if a stroke simulator is installed on the master cylinder side when viewed from this valve, the brake pedal strokes even if the brake fluid introduction is blocked by the valve at the beginning of the brake pedal, so-called "hardness". I don't feel.

[0003]

At present, vehicles having only fluid pressure braking (for example, hydraulic braking) are widely used. Therefore, it is desirable to realize a stroke characteristic close to the stroke characteristic in the case of only fluid pressure braking. Although the stroke simulator described in the above publication is useful for achieving this purpose, it has some drawbacks. First, the provision of the stroke simulator causes complication and enlargement of the device configuration. Second,
Immediately after the valve is opened, a non-compressible fluid for braking (for example, braking oil) is rapidly introduced to the wheel cylinder side, and as a result, the feeling of the brake pedal is deteriorated and the regenerative braking force is reduced. Rapid incompressible fluid for braking (eg braking oil) to the wheel cylinder side when shifting from the used area to the area exclusively used for fluid pressure braking force
However, the stroke simulator cannot solve the problem that the feeling is deteriorated by the introduction of the brake pedal.

The present invention has been made to solve the above problems, and the stroke is achieved by executing the initial introduction control for introducing the incompressible fluid for braking into the wheel cylinder at the initial stage of braking. It is an object of the present invention to prevent problems such as so-called "ped-in" without using a simulator, and to realize more comfortable braking with a simpler configuration. The present invention further comprises
By executing the initial introduction control adapted to the estimated flow rate, while securing the braking energy recovery amount by regeneration,
An object of the present invention is to suitably prevent "pushing of the pedal when shifting from regenerative braking to fluid pressure braking" and to realize fluid pressure braking force control that does not vary depending on how the brake pedal is depressed. An object of the present invention is to prevent the so-called "brake hardness" by eliminating the region where the valve is completely closed, and to realize a feeling closer to that of the fluid pressure braking mechanism alone. An object of the present invention is to realize deceleration without discomfort by changing the termination condition of the initial introduction control according to the vehicle speed in the initial stage of braking. An object of the present invention is to further reduce the hardness of the brake by smoothing the gradient of the stroke characteristic. The present invention introduces an additional mechanism,
It is an object of the present invention to realize the above object with a simpler control logic.

[0005]

A braking device for an electric vehicle, which is a premise of the present invention, has means for exerting a fluid pressure braking force on a drive wheel according to a wheel cylinder pressure, and its valve opening value can be controlled from the outside. A valve that shuts off the introduction of the incompressible fluid for braking from the master cylinder to the wheel cylinder until the differential pressure between the master cylinder pressure and the wheel cylinder pressure exceeds the valve opening value, and the regenerative braking force according to the differential pressure. And means for acting on the drive wheels.

In the braking system for an electric vehicle according to the first aspect of the present invention, in the above-mentioned prerequisite configuration, the flow rate of the incompressible fluid for braking from the master cylinder to the wheel cylinder is based on the master cylinder pressure and the wheel cylinder pressure. And a valve forcibly opening the valve by controlling the valve opening value to a value smaller than the differential pressure until the estimated flow rate after the braking is requested reaches the initial introduction end value. And means for initially introducing the braking incompressible fluid from the master cylinder to the wheel cylinders.
In this configuration, as a result of the initial introduction of the incompressible fluid for braking being performed, a certain amount of flow rate is generated even in the initial stage of braking, and so-called "entry" at the initial stage of braking is no longer felt. Also, when switching the braking force to be used from regenerative braking force to fluid pressure braking force, a certain amount of incompressible fluid for braking has already been introduced into the wheel cylinders. Is unlikely to occur. Furthermore, since the initial introduction end determination is executed based on the flow rate that has a property that does not easily depend on how the brake pedal is depressed, the initial introduction is completed at an appropriate timing and does not vary depending on how the brake pedal is depressed. Fluid pressure braking force control is realized. As a result, for example, an operation of preventing "entering" while securing a sufficient amount of braking energy to be recovered by regeneration is achieved. Since the above-described operation is realized without using the stroke simulator, the device configuration becomes simpler.

In the braking system for an electric vehicle according to the second aspect of the present invention, in the above-described premise, the valve opening value is smaller than the differential pressure until a predetermined condition is satisfied after braking is requested. Control means to forcefully open the valve, and thereby to initially introduce the braking incompressible fluid from the master cylinder to the wheel cylinders, and after the initial introduction is completed, the master cylinder to the wheel cylinders are not braked. Means for gradually increasing the valve opening value so that the compressive fluid is gradually introduced. Also in this configuration, at least the action associated with the execution of the initial introduction occurs among the actions that occur in the first configuration. In addition, since the valve does not close completely during the valve opening value gradual increase control after the initial introduction,
The gradient of the stroke characteristic is a smooth gradient that does not cause "hardness of the brake", and the feeling is closer to that of the fluid pressure braking mechanism alone.

In the braking system for an electric vehicle according to the third configuration of the present invention, in the first configuration, the braking incompressible fluid is gradually introduced from the master cylinder to the wheel cylinder after the initial introduction is completed. As described above, a means for gradually increasing the valve opening value is provided. In this configuration, since the actions of both the first and second configurations occur, the feeling is closer to that of the case of using only the fluid pressure braking mechanism.

In the braking system for an electric vehicle according to a fourth configuration of the present invention, in the first or third configuration, the initial introduction end value is changed and set according to the speed of the driving wheels at the time when braking is requested. It is characterized by comprising means. In this configuration, the termination condition of initial introduction changes according to the vehicle speed at the initial stage of braking, so that deceleration that does not cause discomfort when the brake pedal is depressed is realized.

A braking device for an electric vehicle according to a fifth configuration of the present invention is the braking device for an electric vehicle according to the second or third configuration, which includes means for sequentially changing the increasing gradient of the valve opening value according to the flow rate after the completion of initial introduction. It is characterized by being provided. In this configuration, since the stroke is gentle after the initial introduction,
The hardness of the brake is further reduced.

A braking device for an electric vehicle according to a sixth structure of the present invention is, in the first, second, third or fifth structure, provided between the above-mentioned flow path valve and the wheel cylinder, and responds to a command. A wheel cylinder pressure reducing mechanism for reducing the wheel cylinder pressure is provided. In this configuration,
Since the wheel cylinder pressure reducing mechanism can reduce the wheel cylinder pressure, it is not necessary to consider the wheel cylinder pressure when determining the target value of the regenerative braking force, and the control logic becomes simpler. Further, since the control for changing the initial introduction termination condition according to the speed as in the fourth configuration is unnecessary, the control logic becomes simpler in this respect as well.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the system configuration of an electric vehicle according to the first embodiment of the present invention. This embodiment is an example of a front-wheel drive vehicle. Further, driving power is supplied from an on-vehicle battery 14 to the AC motor 12 that is a vehicle traveling motor. At that time, in order to convert the DC power discharged from the battery 14 into AC power, the inverter 1
3 is used. The electric power conversion by the inverter 13 is controlled by a motor ECU (electronic control unit) 15. The motor ECU 15 starts / ends this control according to the key switch operation of the vehicle operator. Motor ECU
Reference numeral 15 denotes a torque corresponding to a torque command determined based on the result of detecting the rotation speed of the motor 12 and the speed of the front wheel, which is a driving wheel, while referring to the operation of the accelerator pedal or the shift lever by the vehicle operator. Is controlled to be output from the motor 12.

The vehicle shown in this figure has both hydraulic braking and regenerative braking as braking means. First, as hydraulic braking means, there is a hydraulic transmission system from the brake pedal 1 to the front brake disc 7 and the rear brake disc 9. That is, when the brake pedal 1 is depressed, the hydraulic pressure (master cylinder pressure) Pm corresponding to the depression of the brake pedal 1 is generated.
c is generated in the master cylinder 2, and the generated master cylinder pressure Pmc is applied to the front regenerative hydraulic valve 1 described later.
0 or the rear regenerative hydraulic valve 11 is open, the front wheel cylinder 6 or the rear wheel cylinder 8
Is transmitted to When hydraulic pressure (wheel cylinder pressure) Pwc is generated in the front wheel cylinder 6, hydraulic braking force acts on the front brake disc 7, and when wheel cylinder pressure Pwc is generated in the rear wheel cylinder 8, hydraulic braking force acts on the rear brake disc 9. .

Next, the regenerative braking is controlled by the regenerative ECU 16, the motor ECU 15, the inverter 13 and the motor 12.
Is executed by That is, when the command relating to the regenerative braking force Treg is given from the regenerative ECU 16, the motor EC
U15 controls the power conversion operation by the inverter 13 so that the regenerative braking force is realized as the output torque of the motor 12. In this state, the battery 14 is charged with the braking energy recovered via the motor 12 as electric power. Therefore, when the regenerative braking force is preferentially used over the hydraulic braking force, the braking energy can be reused, and thus the energy efficiency of the vehicle is generally increased. Since the regenerative braking force is actually realized as the regenerative torque Treg as described above, the regenerative braking force is called regenerative torque in the following description, and the hydraulic braking force is also called hydraulic torque. I will decide.

When the brake switch (not shown) attached to the brake pedal 1 is turned on, or when the master cylinder pressure Pmc detected by the hydraulic pressure sensor 3 exceeds a predetermined value P0, the regenerative ECU 16 is operated by the vehicle operator. Assuming that the brake pedal 1 is depressed, control of braking torque distribution between regeneration and hydraulic pressure and torque distribution between front and rear is started. That is, when the regenerative torque is used preferentially over the hydraulic torque, the regenerative ECU 16 closes the front regenerative hydraulic valve 10 by setting the opening value of the front regenerative hydraulic valve 10 to a sufficiently high value. The hydraulic pressure transmission from 2 to the front wheel cylinder 6 is cut off. At the same time, the regenerative ECU 16 obtains the difference between the master cylinder pressure Pmc detected by the hydraulic pressure sensor 3 and the front wheel cylinder pressure Pwc detected by the hydraulic pressure sensor 4, and the regenerative torque corresponding to this differential pressure Pmc-Pwc. Generate Treg. When the hydraulic torque is used with priority over the regenerative torque, the regenerative E
The CU 16 introduces the braking oil from the master cylinder 2 to the front wheel cylinder 6 by setting the valve opening value of the front regenerative hydraulic valve 10 to a sufficiently low value. Further, the regenerative ECU 16 uses the front regenerative hydraulic valve 10
Rear regenerative hydraulic valve 11 having the same configuration as described above, and a hydraulic sensor 5 for detecting the rear wheel cylinder pressure Pwc.
Is used to control the torque distribution between the front and rear.

As shown in FIG. 2, the front regenerative hydraulic valve 10 and the rear regenerative hydraulic valve 11 have a plunger 18 and a solenoid 17 for driving the plunger 18 in the left-right direction in the drawing. Regenerative ECU 16
Changes the valve opening values of the front regenerative hydraulic valve 10 and the rear regenerative hydraulic valve 11 by changing the current (valve command current) passed through the solenoid 17. The front regenerative hydraulic valve 10 and the rear regenerative hydraulic valve 11 are
It is closed while the differential pressure Pmc-Pwc before and after that is below the valve opening value, and opens when it exceeds the valve opening value. While the front regenerative hydraulic valve 10 and the rear regenerative hydraulic valve 11 are open, the differential pressure before and after the front regenerative hydraulic valve 10 or the rear regenerative hydraulic valve 11 is maintained.

A problem when designing such a system is the characteristic of the stroke s of the hydraulic braking system versus the pedal effort (or the braking oil flow rate q versus the master cylinder pressure Pmc).
Characteristic) of a normal hydraulic braking system. That is, when the hydraulic pressure transmission is cut off by the front regenerative hydraulic valve 10 as described above and the braking force distribution control with the regeneration priority is executed, the curve ABCE in FIG.
As represented by F, the characteristic is different from the characteristic represented by the curve ADF when the hydraulic pressure is used alone. This is because it is necessary to preferentially generate the regenerative torque, so that the front regenerative hydraulic valve 10 is closed (point B) in the initial stage of braking, and the braking oil is applied to the front wheel cylinder 6 from the time when the front regenerative hydraulic valve 10 is opened (point C). By introducing the control. Like the curve ABCEF, the area where the brake feels hard (BC) and the area where "brake-in" occurs (CE) are unnatural to the operator who is accustomed to the characteristics represented by the curve ADF. To be

Further, regarding the regenerative torque, its upper limit value is often severely limited in a low speed region in order to prevent torque hunting and suppress power consumption (due to field current and the like). Therefore, when the vehicle speed (the number of rotations of the motor 12) decreases as the braking progresses as shown in FIG. 4, the "required braking torque" (master cylinder pressure P shown in FIG.
A change from the regenerative use region to the hydraulic pressure use region occurs with the change of (corresponding to mc). That is, as shown in FIGS. 5 and 6, only the regenerative torque is used in a region where the required braking torque is smaller than the regenerative torque upper limit value, and the hydraulic torque starts to be used when the required braking torque starts to exceed the regenerative torque upper limit value. (Point H), when the regenerative torque upper limit value reaches 0 (Point I), there is only hydraulic torque. When switching from such regeneration to hydraulic pressure, the braking oil is rapidly introduced into the front wheel cylinder 6, so that the brake pedal 1 is inserted.

Among these problems, in order to prevent "entry" at the initial stage of braking and "entry" at the time of switching from regeneration to hydraulic pressure, the initial introduction of braking oil into the front wheel cylinder 6 may be performed. That is, as represented by the curve ADEF in FIG. 3, the front regenerative hydraulic valve 10 has a sufficiently low opening value until the stroke s1 at the beginning of hydraulic torque effect at the beginning of braking (point D). Brake oil is introduced into the cylinder 6 (initial introduction), and then the valve opening value of the front regenerative hydraulic valve 10 is made sufficiently high to perform regenerative priority braking force distribution control, and thus, to recover braking energy, and to regenerate the front regenerative hydraulic valve. After opening 10, the brake pedal 1 starts to stroke again (between EF). As a result, the "entrance" region such as between CEs does not occur, and the "entrance" accompanying switching from regeneration to hydraulic pressure can be prevented.

However, nonetheless, there remains a "hard" region, such as between BEs. Further, the hydraulic pressure sensor 4 needs to be provided in the vicinity of the front regenerative hydraulic valve 10, that is, at a position away from the front wheel cylinder 6 for the convenience of wiring wiring, and therefore pressure transmission is delayed due to resistance of the pipe. Therefore, if the initial hydraulic pressure introduction end determination is performed based on the output Pmc of the hydraulic pressure sensor 4, a control error occurs as shown in FIG. 7. Since this control error depends on the depression speed of the brake pedal 1 and the like, its variation cannot be ignored.

In order to solve these remaining problems, in this embodiment, the front regenerative hydraulic valve 10 is controlled so that the stroke-to-pedal force characteristic shown by AGF in FIG. 8 is realized. The ADE in which the characteristic indicated by AGF in FIG. 8 is described as “valve fully closed control” in FIG.
The characteristic that can be different from the characteristic of F, that is, the characteristic indicated by “with initial hydraulic pressure introduction” in FIG. 3, is that the initial hydraulic pressure introduction is completed at point G instead of point D, and after the initial hydraulic pressure introduction is completed. The slope of is not steep like DE but is gentle like GF.

The characteristic AGF having such characteristics is realized by the configuration of FIG. 9 incorporated in the regenerative ECU 16.

As shown in FIG. 9, the regenerative ECU 16
Includes a target stroke characteristic calculator 19. The target stroke characteristic calculator 19 calculates the target stroke characteristic, that is, AGF in FIG. 8, based on the master cylinder pressure Pmc and the wheel cylinder pressure Pwc detected by the hydraulic pressure sensors 3 and 4, and the result is calculated as a pseudo elasticity control unit. 21. In addition, the stroke estimator 20 uses the master cylinder pressure P obtained from the hydraulic pressure sensors 3 and 4 in the same manner.
Based on mc and the wheel cylinder pressure Pwc, the estimated value of the current stroke, that is, the estimated stroke s, is obtained and supplied to the pseudo elasticity control unit 21. Here, since the braking oil can be regarded as an incompressible fluid, the flow rate of the braking oil flowing through the front regenerative hydraulic valve 10 can be regarded as constant regardless of how the brake pedal 1 is depressed, and the flow rate q is It corresponds to the stroke s. Therefore, when obtaining the estimated stroke s,

[Equation 1] According to the procedure, the flow rate q is estimated, and the estimated flow rate q is converted into the estimated stroke s. The calculation of the square root included in the equation (1) is performed by the regenerative ECU 16
If it is difficult to implement as an arithmetic expression in
The SQRT map as shown by 0 may be installed in the regenerative ECU 16. The pseudo-elasticity control unit 21 uses the target stroke obtained by the target stroke characteristic calculator 19 and the estimated stroke obtained by the stroke estimator 20 to determine the valve command current, that is, the spool of the plunger 18 in the front regenerative hydraulic valve 10. The current for controlling the position y is determined and output. For example, the value of the estimated stroke s obtained by the stroke estimator 20 is the stroke s of the point G constituting the target stroke characteristic obtained by the target stroke characteristic calculator 19.
When it is equal to 0, the pseudo elasticity control unit 21 gives a command to the front regenerative hydraulic valve 10 to end the initial introduction.

By executing such control, at a proper timing, that is, at a timing at which regeneration can be sufficiently performed and "entry" of the brake pedal 1 can be preferably prevented. , The initial introduction can be finished. Furthermore, since the front regenerative hydraulic valve 10 is controlled based on the flow rate q that is an amount that does not depend on how the brake pedal 1 is stepped, a control error due to the resistance of the pipe between the hydraulic sensor 4 and the front wheel cylinder 6 and its fluctuations. Is not affected by. In addition, the pseudo elasticity control unit 21 generates the valve command current by referring to the estimated stroke s with the target stroke characteristic. That is, control is performed to gradually increase the valve opening value of the front regenerative hydraulic valve 10 so that the GF among the target stroke characteristics AGF in FIG. 8 has a smooth gradient. Since such control is performed, in the present embodiment, unlike the characteristic represented by ADEF, the region DE where the "hardness" of the brake pedal 1 is felt does not occur.

Further, up to the vehicle speed (rotational speed of the motor 12) at the time when the brake pedal 1 is started, as shown in FIG. 11, a situation occurs in which the required braking torque exceeds the regenerative torque upper limit value at the initial stage of braking. obtain. When such a situation occurs, it is necessary to realize the braking torque equivalent to the required braking torque minus the upper limit value of the regenerative braking torque as the hydraulic torque. In this case, in this embodiment,
As shown in FIG. 12, control is performed such that the G point is moved to, for example, the G ′ point, and thus the stroke for ending the initial introduction is moved from s0 to s ′. In order to execute such control, in the present embodiment, the target stroke characteristic calculator 19 changes the value of the stroke s0 according to the vehicle speed at the start of stepping according to the s0 determination map shown in FIG. In this way, by changing the value of the stroke s0 that ends the initial introduction in accordance with the vehicle speed at the start of stepping,
As shown in FIG. 11, it becomes possible to suitably cope with the situation in which the hydraulic torque must be used in the initial stage of braking.
Furthermore, by appropriately setting the s0 determination map, it is possible to obtain a deceleration that does not cause a sense of discomfort.

Further, the spool position estimator 22 (see FIG. 9) built in the regenerative ECU 16 has a master cylinder pressure P.
wc, the wheel cylinder pressure Pwc on the front side, and the valve command current obtained by the pseudo elasticity control unit 21 based on the plunger 1 of the front regenerative hydraulic valve 10.
The position y of 8 is estimated. If the stroke estimator 20 estimates the stroke s based on the estimated spool position y obtained in this way, as shown in FIG. A smooth gradient can always be achieved despite the movement of points. When the spool position estimator 22 is used, in the stroke estimator 20, the following formula is used instead of the formula (1).

[Equation 2] To use. FIG. 15 shows the regeneration E in this embodiment.
The flow of operation of the CU 16 is shown. As shown in this figure, the regenerative ECU 16 first executes a predetermined initialization process (101), inputs its output signals from various sensors shown in FIG. 1 (102), and performs noise removal and the like. Therefore, after low-pass filtering the input result, (10
3), the operation after step 104 is executed. In step 104, the regenerative ECU 16 determines that the motor ECU 1
Information about the shift position is input via 5, and it is determined whether or not the current shift position is D, that is, a position intended for the vehicle to travel. As a result, when it is determined that the shift position is not D, the regenerative ECU 16 sets the value of the regenerative torque to be output to 0 and the value of the valve command current to 0 (105), and determines the determined regenerative torque. And valve command currents are output (106, 107), respectively.
The regenerative ECU 16 repeatedly executes the operations of steps 102 to 107 until the keyboard switch is turned off by the vehicle operator, and when it is turned off, executes a predetermined ending process (109).

When it is determined in step 104 that the shift position is D, the regenerative ECU 16 determines whether the brake switch is on and whether the master cylinder pressure Pmc exceeds the predetermined value P0. (1
10). When the brake switch is not turned on and the master cylinder pressure Pmc does not exceed the predetermined value P0, it can be considered that the vehicle operator is not stepping on the brake pedal 1, so the regenerative ECU 16 outputs the regenerative torque. After 0, the valve command current is 0, and s0Flag is turned off (122), steps 106 and 107 are executed. Therefore, in this state, no regenerative torque is output and the front regenerative hydraulic valve 10 is also kept closed.

If it is determined in step 110 that the brake switch is on or the master cylinder pressure Pmc exceeds the predetermined value P0, the regenerative ECU.
16 determines that the brake pedal 1 is depressed by the vehicle operator, and determines whether s0Flag is off (111). When s0Flag is off, it can be considered that the brake switch has not been turned on and the master cylinder pressure Pmc has not exceeded the predetermined value P0 until then, so the regenerative EC
U16 turns on s0Flag first, and then
The stroke s0 is calculated using the s0 decision map shown in (112). In step 111, s0Fla
When it is determined that g is not off, this step 112 is omitted. After execution of step 112 or after it is determined in step 111 that s0Flag is not off, steps 113 and 114 are executed. In step 113, the spool position estimator 2
2, the estimated spool position y is calculated according to the above-mentioned principle.
The estimated stroke s is determined by the above-mentioned principle. After the execution of steps 113 and 114, the regenerative ECU 16 performs s>
It is determined whether it is s0 (115). When s> s0 is not established, it can be considered that the brake pedal 1 is shallowly depressed and its stroke has not yet reached the point G. Therefore, the regenerative ECU 16 sets the valve command current to 0 (118). . On the contrary, when s> s0 is satisfied, the target stroke characteristic calculator 19 calculates the target stroke characteristic (116), and further the valve command current is calculated by the pseudo elasticity control unit 21 (1
17). After executing step 117 or 118, regenerative EC
U16 calculates the regenerative torque upper limit value Tmax based on the motor rating, the voltage of the battery 14, etc. (119), and then the following equation

(Equation 3) The command value of the regenerative torque Treg is calculated based on (12
0). The regenerative ECU 16 then calculates the regenerative torque T
After adjusting the command value of reg based on the constraint conditions such as the voltage of the battery 14 (121), steps 106 and 107
To execute. With such a procedure, the above-described operational effects are realized.

FIG. 16 shows the system configuration of an electric vehicle according to the second embodiment of the present invention. In this system, a wheel pressure reducing mechanism 23 is provided between the front regenerative hydraulic valve 10 and the front wheel cylinder 6. As shown in FIG. 17, the wheel pressure reducing mechanism 23 has a configuration in which the volume of the variable volume chamber 24 can be changed by the piston 25. The variable volume chamber 24 communicates with the hydraulic pipe between the front regenerative hydraulic valve 10 and the front wheel cylinder 6, and therefore the volume of the variable volume chamber 24 is increased to drain the braking oil from the front wheel cylinder 6. You can The piston 25 is driven by a ball screw 26, and the ball screw 26 is rotationally driven by a wheel pressure control motor 27. The wheel pressure control motor 27 is controlled by the regenerative ECU 16.

FIG. 18 shows the regeneration E in this embodiment.
The flow of operation of the CU 16 is shown. In this embodiment, in step 120, the regenerative torque Treg is set.
When calculating the command value of, not the above equation (3) but the following equation

(Equation 4) Is used. Further, the regenerative ECU after step 120 is executed
16 is the following formula

(Equation 5) Based on the calculated target value Pwcs of the wheel cylinder pressure Pwc (123), the following equation is calculated based on the calculated target value Pwcs.

(Equation 6) Is used to calculate the torque Twc commanded to the wheel pressure control motor (124). As described above, in step 120, the regenerative torque Treg is calculated by the equation (4), that is, without using the wheel cylinder pressure Pwc.
The command value of can be calculated in step 124.
This is because the braking oil can be drained from the front wheel cylinder 6 by driving the wheel pressure control motor 27 of the wheel pressure reducing mechanism 23 in accordance with the torque Twc calculated in (3). Further, the reason why it is not necessary to perform the adjustment in step 121 after calculating the command value of the regenerative torque Treg is that the constraint condition such as the voltage of the battery 14 can be reflected when executing step 124.
Further, it is not necessary to execute steps 111 and 112 before executing step 113, and the change of the initial introduction timing due to the change of the vehicle speed can be realized by the pressure reduction using the wheel pressure reducing mechanism 23 in step 124. This is because. In step 125,
In order to enable such pressure reduction, the volume of the variable volume chamber 24 is initially set to 0 by driving the wheel pressure control motor 27.

Therefore, according to this embodiment, the above-mentioned first
Similar control effects can be obtained with a simpler control logic than the embodiment. Further, in the above-described first embodiment,
If the differential pressure torque is introduced in the initial stage of braking under the situation as shown in FIG. 11, even if the regenerative torque upper limit value becomes sufficiently large and the required braking torque is exceeded,
The regenerative torque cannot be increased (see FIG. 19). On the other hand, when the wheel pressure reducing mechanism 23 is provided as in this embodiment, as shown in FIG.
The hydraulic torque can be reduced before the brake pedal 1 is stepped back, and therefore the regenerative torque can be increased up to the regenerative torque upper limit value. As a result, it is possible to realize an electric vehicle with higher energy efficiency than that of the first embodiment.

In the above description, the electric vehicle of the front-wheel drive vehicle is applied to the present invention, but the application target of the present invention is not limited to the front-wheel drive vehicle. Further, the specific configuration of the wheel pressure reducing mechanism 23 may be different from the configuration illustrated above.

[0034]

As described above, according to the first configuration of the present invention, since the initial introduction of the incompressible fluid for braking is executed, the "entry" at the initial stage of braking and the braking force to be used can be reduced. When the regenerative braking force is switched to the fluid pressure braking force, "entry" is unlikely to occur, and therefore a better brake feeling or stroke characteristics can be obtained. At that time, since the stroke simulator is not necessary, the device configuration becomes simpler. Furthermore, because the initial introduction end determination is executed based on the flow rate that has a property that does not easily depend on how the brake pedal is depressed, it is possible to secure a sufficient amount of braking energy recovery by regeneration at the appropriate timing, such as "entry". It is possible to end the initial introduction at a timing that can also prevent the above, and to realize fluid pressure braking force control that does not vary depending on how the brake pedal is depressed.

According to the second configuration of the present invention, since the initial introduction of the braking incompressible fluid is executed, at least the effect associated with the execution of the initial introduction is obtained among the effects obtained by the first configuration. be able to. Furthermore, since the valve opening value is gradually increased so that the braking incompressible fluid is gradually introduced from the master cylinder to the wheel cylinder after the initial introduction is completed, the valve is not completely closed after the initial introduction is completed. As a result of the smooth stroke characteristic, the problem of "brake hardness" is eliminated, and the feeling is closer to that of the fluid pressure braking mechanism alone.

According to the third structure of the present invention, it is possible to obtain the effects of both the first and second structures, and it is possible to realize a feeling even closer to that of the case where only the fluid pressure braking mechanism is used.

According to the fourth aspect of the present invention, the initial introduction end value is changed and set according to the speed of the driving wheels at the time when braking is requested, so that there is no discomfort when the brake pedal is depressed. Can achieve deceleration.

According to the fifth configuration of the present invention, after the initial introduction is completed, the increasing gradient of the valve opening value is sequentially changed according to the flow rate, so that the stroke is gradually made after the initial introduction is completed. The hardness of the brake can be further reduced.

According to the sixth aspect of the present invention, since the wheel cylinder pressure reducing mechanism for reducing the wheel cylinder pressure according to the command is provided between the on-flow valve and the wheel cylinder, the wheel cylinder pressure reducing mechanism is used. Since the wheel cylinder pressure can be reduced, it is not necessary to consider the wheel cylinder pressure when determining the target value of the regenerative braking force, and the control logic becomes simpler. Also, the fourth
Since the control for changing the initial introduction end condition according to the speed as in the configuration of No. 1 is not necessary, the control logic becomes simpler also in this aspect.

[0040]

[Addendum] The present invention can be further understood as the following configurations.

(1) In the braking control method according to the seventh aspect of the present invention, a means for exerting a fluid pressure braking force on the drive wheels according to the wheel cylinder pressure and the valve opening value can be controlled from the outside, A valve that shuts off the introduction of the braking incompressible fluid from the master cylinder to the wheel cylinder until the differential pressure between the cylinder pressure and the wheel cylinder pressure exceeds the valve opening value.
A braking force of the master cylinder to the wheel cylinder based on the master cylinder pressure and the wheel cylinder pressure. The step of estimating the flow rate of the fluid and forcibly opening the valve by controlling the valve opening value to a value smaller than the above differential pressure until the estimated flow rate reaches the initial introduction end value after braking is requested. In this way, the step of initially introducing the braking incompressible fluid from the master cylinder to the wheel cylinders is included. According to this configuration, the same operational effect as the first configuration can be obtained.

(2) In the braking control method according to the eighth configuration of the present invention, a means for exerting a fluid pressure braking force on the drive wheels according to the wheel cylinder pressure and the valve opening value thereof can be controlled from the outside, A valve that shuts off the introduction of the braking incompressible fluid from the master cylinder to the wheel cylinder until the differential pressure between the cylinder pressure and the wheel cylinder pressure exceeds the valve opening value.
And a means for applying a regenerative braking force corresponding to the differential pressure to the driving wheels, the valve opening value being set to the differential pressure until a predetermined condition is satisfied after braking is requested. By controlling to a smaller value, the valve is forcibly opened, so that the incompressible fluid for braking is initially introduced from the master cylinder to the wheel cylinder, and after the initial introduction is completed, the master cylinder is changed to the wheel cylinder. Gradually increasing the valve opening value so that the braking incompressible fluid is gradually introduced.
According to this structure, the same effect as the second structure can be obtained.

(3) In the braking control method according to the ninth configuration of the present invention, in the seventh configuration, after the initial introduction, the incompressible fluid for braking is gradually introduced from the master cylinder to the wheel cylinders. So that the valve opening value is gradually increased. According to this configuration, the same operational effect as the third configuration can be obtained.

(4) In the braking control method according to the tenth configuration of the present invention, in the seventh or ninth configuration, the initial introduction end value is changed and set according to the speed of the driving wheels at the time when braking is requested. It has a step of performing. According to this structure, the same effect as the fourth structure can be obtained.

(5) In the braking control method according to the eleventh configuration of the present invention, in the eighth or ninth configuration, after the initial introduction is completed, the step of sequentially changing the increasing gradient of the valve opening value according to the flow rate. It is characterized by having. According to this configuration,
The same effect as the fifth structure can be obtained.

(6) A braking control method according to a twelfth structure of the present invention is the wheel cylinder provided between the above-mentioned flow path valve and the wheel cylinder in the seventh, eighth, ninth and eleventh structures. It is characterized by including a step of reducing the wheel cylinder pressure so that the regenerative braking force becomes closer to its upper limit value by using a pressure reducing mechanism. According to this configuration, it is possible to achieve energy efficiency improvement by regenerative braking using the sixth configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing a system configuration of an electric vehicle according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing the configuration of a regenerative hydraulic valve.

FIG. 3 is a diagram comparing the characteristics of stroke versus pedaling force when a hydraulic brake is used alone and when it is used in combination with regeneration.

FIG. 4 is a timing chart showing a change in vehicle speed due to braking.

FIG. 5 is a diagram showing a change in required braking torque and a change in braking force distribution due to braking.

FIG. 6 is a timing chart showing a change in braking force distribution due to braking.

FIG. 7 is a timing chart showing a control error due to a delay in output transmission and its variation.

FIG. 8 is a diagram showing an example of target stroke characteristics.

FIG. 9 is a block diagram showing an internal configuration of a regenerative ECU.

FIG. 10 is a diagram showing an example of an SQRT map.

FIG. 11 is a diagram showing a change in required braking torque and a change in braking force distribution due to braking.

FIG. 12 is a diagram showing an example of application control of a target stroke characteristic to a pedaling start vehicle speed.

FIG. 13 is a diagram showing an example of an s0 determination map.

FIG. 14 is a diagram showing another example of application control of target stroke characteristics to a pedaling start vehicle speed.

FIG. 15 is a regenerative ECU according to the first embodiment of the present invention.
5 is a flowchart showing a flow of the operation of FIG.

FIG. 16 is a block diagram showing a system configuration of an electric vehicle according to a second embodiment of the present invention.

FIG. 17 is a schematic sectional view showing the structure of a wheel pressure reducing mechanism.

FIG. 18 is a regeneration ECU according to a second embodiment of the invention.
5 is a flowchart showing a flow of the operation of FIG.

FIG. 19 is a timing chart showing limitation of regenerative torque due to introduction of hydraulic pressure.

FIG. 20 is a timing chart showing the effect of wheel pressure reduction.

[Explanation of symbols]

1 brake pedal, 2 master cylinder, 3-5 hydraulic pressure sensor, 6 front wheel cylinder, 7 front brake disc, 8 rear wheel cylinder, 9
Rear brake disc, 10 Front regenerative hydraulic valve, 11 Rear regenerative hydraulic valve, 12 Motor, 13
Inverter, 14 battery, 15 motor ECU, 16
Regenerative ECU, 17 solenoids, 18 plungers, 1
9 target stroke characteristic calculator, 20 stroke estimator, 21 pseudo elasticity control unit, 22 spool position estimator,
23 wheel pressure reducing mechanism, 24 variable volume chamber, 25
Piston, 26 ball screw, 27 wheel pressure control motor, Pmc master cylinder pressure, Pwc wheel cylinder pressure, s1 stroke at which hydraulic torque starts to be generated, s0, s0 'stroke for ending initial introduction, s
Estimated stroke, q Estimated flow rate, y Estimated spool position.

Claims (6)

[Claims] 1. A means for exerting a fluid pressure braking force on a drive wheel according to a wheel cylinder pressure, and a valve opening value thereof can be controlled externally, and a differential pressure between a master cylinder pressure and a wheel cylinder pressure determines a valve opening value. A braking device for an electric vehicle, comprising: a valve that blocks introduction of a braking incompressible fluid from a master cylinder to a wheel cylinder until it exceeds a value; and a unit that causes a regenerative braking force corresponding to the differential pressure to act on a drive wheel. , Means for estimating the flow rate of the incompressible fluid for braking from the master cylinder to the wheel cylinder based on the master cylinder pressure and the wheel cylinder pressure, and until the estimated flow rate after the braking is requested reaches the initial introduction end value, The valve is forcibly opened by controlling the valve opening value to a value that is smaller than the above differential pressure, thus initiating the incompressible fluid for braking from the master cylinder to the wheel cylinders. Braking apparatus for an electric vehicle, characterized in that it comprises a means for entering a. 2. A means for exerting a fluid pressure braking force on a drive wheel according to a wheel cylinder pressure and a valve opening value thereof can be controlled from the outside, and a differential pressure between a master cylinder pressure and a wheel cylinder pressure determines a valve opening value. A braking device for an electric vehicle, comprising: a valve that blocks introduction of a braking incompressible fluid from a master cylinder to a wheel cylinder until it exceeds a value; and a unit that causes a regenerative braking force corresponding to the differential pressure to act on a drive wheel. , The valve is forcibly opened by controlling the valve opening value to a value smaller than the above differential pressure until a predetermined condition is satisfied after braking is requested. Means for initially introducing the compressive fluid, and means for gradually increasing the valve opening value so that the braking incompressible fluid is gradually introduced from the master cylinder to the wheel cylinders after the initial introduction. A braking device for an electric vehicle, comprising: 3. The braking system for an electric vehicle according to claim 1, wherein after the initial introduction, the valve opening value is gradually increased so that the braking incompressible fluid is gradually introduced from the master cylinder to the wheel cylinders. A braking device for an electric vehicle, comprising: 4. The braking device for an electric vehicle according to claim 1 or 3, further comprising means for changing and setting an initial introduction end value according to a speed of driving wheels at a time when braking is requested. Vehicle braking system. 5. The braking system for an electric vehicle according to claim 2 or 3, further comprising means for sequentially changing an increasing gradient of the valve opening value according to the flow rate after completion of initial introduction. Braking device. 6. The braking system for an electric vehicle according to claim 1, 2, 3 or 5, further comprising: a wheel cylinder pressure reducing mechanism that is provided between the flow path valve and the wheel cylinder and that reduces the wheel cylinder pressure according to a command. A braking device for an electric vehicle, comprising: