JPH07250402A - Brake controller for electric automobile - Google Patents

Abstract

PURPOSE:To make smooth the increase of liquid pressure, functioning as the hydraulic brake power, by forming a liquid pressure transmission channel detouring a differential pressure regulating valve when predetermined conditions are satisfied thereby controlling the liquid pressure, functioning as the hydraulic brake power, to increase gradually to a level corresponding to a required brake power. CONSTITUTION:A master cylinder M/C 26 generates a hydraulic pressure depending on the stepping amount of a brake pedal 24 and the hydraulic pressure is transmitted to wheel cylinders W/C 28FL-28RR. Hydraulic switching valves 32F, 32R are disposed in parallel with differential pressure regulating valves 30F, 30R, respectively, between the M/C 26 and the W/C 28FR-28RR. An antilock brake ABS 36 is interposed between the W/C and M/C' in order to control an ABSECU 38. A regenerative ECU 34 receives inputs from a brake switch 48 and the ABSECU 38, an M/C pressure 40 and a W/C pressure 42, and when conditions of regenerative brake are satisfied, the valves 32F, 32R are turned ON and the time required for the W/C pressure to reach the M/C pressure 15 prolonged by controlling the ON/OFF time ratio thus improving the brake feeling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric vehicle that is braked by hydraulic braking force (generally hydraulic braking force) and regenerative braking force, and more particularly to a braking control device for controlling the hydraulic braking force and the regenerative braking force.

[0002]

2. Description of the Related Art Hydraulic braking is generally used as a means for braking a vehicle. When hydraulic braking is performed, a master cylinder (M / C) that generates hydraulic pressure in response to the depression of the brake pedal by the vehicle operator is provided, and
A wheel cylinder (W / C) is provided to apply hydraulic braking force to each wheel. If necessary, the master cylinder and the wheel cylinder are connected via a valve or the like. When the vehicle operator depresses the brake pedal, the hydraulic pressure generated in the master cylinder is transmitted to the wheel cylinder in response to the depression, and the hydraulic braking is applied. Furthermore, the hydraulic braking force can be controlled by providing a suitable valve in the hydraulic transmission path.

When the vehicle to be braked is an electric vehicle, regenerative braking can be executed in addition to hydraulic braking. That is, it is possible to regenerate electric power from the vehicle traveling motor to the battery, thereby applying braking to the vehicle. Since regenerative braking is braking performed by collecting braking energy in a battery, in order to improve the energy efficiency of an electric vehicle and extend the travelable distance, regenerative braking should be used in preference to hydraulic braking. Is preferred. Regenerative braking can also be controlled by controlling the power conversion operation between the battery and the motor.

As described above, it is possible to control both the braking function that can be mounted on the electric vehicle, that is, the hydraulic braking and the regenerative braking. Also, when the required braking force (the depression of the brake pedal, and eventually the braking force corresponding to the master cylinder pressure) is realized by using both braking means together, if possible,
Prioritizing regenerative braking is preferable in terms of energy efficiency and extension of the travelable distance. From such a viewpoint, various proposals have conventionally been made regarding distribution of regenerative braking force and hydraulic braking force.

FIG. 7 shows an example of distribution of the regenerative braking force and the hydraulic braking force. In the distribution shown in this figure, the required braking force (master cylinder pressure: M / C pressure) is P _0.
When the required braking force is smaller than the equivalent value, the required braking force is realized only by the regenerative braking force, and in the region where the required braking force is larger than the P ₀ equivalent value, the regenerative braking force is the predetermined value (maximum value) T.
^The hydraulic braking mechanism is controlled such that the hydraulic braking force is constantly controlled to ^* and a hydraulic braking force corresponding to the difference between the regenerative braking force T ^* and the required braking force is generated. By realizing such a braking force distribution, it is possible to preferably realize energy recovery by regenerative braking, thereby extending the travelable distance and suitably realizing the required braking force. Further, such hydraulic control can be realized by providing a differential pressure valve on the hydraulic pressure transmission path from the master cylinder to the wheel cylinder and generating a differential pressure before and after the differential pressure valve. The differential pressure generated by this differential pressure valve is a predetermined value (valve opening value of the differential pressure valve) P ₀ shown in FIG. 7.

By the way, when the braking force of the electric vehicle is obtained by the braking force distribution as shown in FIG. 7, if the differential pressure by the differential pressure valve is generated as it is when the regenerative braking fails, the required braking force is required. Therefore, the braking force cannot be obtained in a small area. As a technique for avoiding such a problem, for example, a technique disclosed in Japanese Patent Laid-Open No. 5-161212 is known. In this publication, a solenoid valve for coping with a regenerative failure is provided in parallel with a differential pressure valve (solenoid valve) that generates a differential pressure P ₀ corresponding to T ^* . This solenoid valve is normally closed, but when a control signal is generated due to a regenerative fail, it opens according to this control signal, and the master cylinder pressure is transmitted to the wheel cylinder side as it is. In this state, the relationship between the required braking force and the total braking force of regenerative pressure and hydraulic pressure is as shown in FIG.
That is, the regenerative braking force becomes 0, and the master cylinder pressure remains in a state of functioning as a hydraulic braking force.

Further, when the driving wheels slip during regenerative braking, the braking force on the driving wheels decreases, and it is effective to increase the hydraulic braking force on the non-driving wheels in order to compensate for it. The solenoid valve provided in parallel with the differential pressure valve provided in the hydraulic system of the non-driving wheels is opened to transmit the master cylinder pressure as it is to the wheel cylinder of the non-driving wheels.

[0008]

However, in a configuration in which a solenoid valve or the like is used to bypass the differential pressure valve and a braking state in which only hydraulic braking force is used is shifted, the wheel cylinder pressure is reduced when the differential pressure valve is bypassed. Since the master cylinder pressure rises sharply, the pedal depression suddenly becomes deep. This gives the vehicle operator a feeling of strangeness in the brake feeling.

The same applies to a configuration in which a solenoid valve or the like is used to bypass the differential pressure valve of the hydraulic system of the non-driving wheels and shift to a braking state in which the master cylinder pressure is directly transmitted to the wheel cylinders of the non-driving wheels. It will give a feeling of strangeness in the brake feeling.

The present invention has been made to solve the above problems, and shifts to a state in which regenerative braking force is controlled to 0 and braking is performed only by hydraulic braking force (eg, hydraulic braking force). The hydraulic braking force is reduced by reducing the increase in the hydraulic pressure (wheel cylinder pressure) that functions as the hydraulic braking force when the master cylinder pressure is directly transmitted to the wheel cylinders of the non-driving wheels. The purpose is to improve the brake feeling when increasing the.

[0011]

In order to achieve such an object, a braking control device mounted on an electric vehicle according to claim 1 of the present invention provides a hydraulic pressure corresponding to a required braking force via a differential pressure valve. By transmitting to the wheel side, hydraulic braking control means for generating a hydraulic braking force smaller than the required braking force, regenerative braking control means for generating a regenerative braking force corresponding to the difference between the required braking force and the hydraulic braking force, If the predetermined conditions are met,
Switching means for switching to braking with increased hydraulic braking force by forming a hydraulic pressure transmission path that bypasses the differential pressure valve, and the switching means forms a hydraulic pressure transmission path that bypasses the differential pressure valve. In this case, the hydraulic pressure acting as the hydraulic braking force is gradually increased to the hydraulic pressure corresponding to the required braking force.

Further, the braking control device mounted on the electric vehicle according to the second aspect of the present invention transmits the hydraulic pressure corresponding to the required braking force to the wheel side through the differential pressure valve so that the hydraulic pressure smaller than the required braking force is transmitted. Hydraulic braking control means for generating a hydraulic braking force, regenerative braking control means for generating a regenerative braking force corresponding to the difference between the required braking force and the hydraulic braking force, and the regenerative braking force when the first predetermined condition is satisfied. And a switching means for switching to braking by only the hydraulic braking force by forming a hydraulic pressure transmission path that bypasses the differential pressure valve and the hydraulic pressure bypassing the differential pressure valve. When the transmission path is formed, the hydraulic pressure acting as the hydraulic braking force when the second predetermined condition is satisfied is gradually increased to the hydraulic pressure corresponding to the required braking force.

Further, in the braking control device according to a third aspect of the present invention, the hydraulic braking control means has a switching valve for forming a hydraulic pressure transmission path that bypasses the differential pressure valve according to a control signal, and the switching means. However, when gradually increasing the hydraulic pressure acting as the hydraulic braking force to the hydraulic pressure equivalent to the required braking force, the control signal is generated while being intermittently interrupted in a time unit shorter than the response time of the hydraulic pressure to the control signal. And

A braking control device according to a fourth aspect of the present invention is
The switching unit changes and controls the time unit for interrupting the control signal so that the formation time and / or the cutoff time of the hydraulic pressure transmission path that bypasses the differential pressure valve becomes longer as the hydraulic pressure gradually increases. It is characterized by

A braking control device according to claim 5 of the present invention is
Alternatively, the hydraulic braking control means has a switching valve that forms a hydraulic pressure transmission path that bypasses the differential pressure valve while generating a differential pressure having a value according to the control signal, and the switching means acts as a hydraulic braking force. When gradually increasing the hydraulic pressure to the hydraulic pressure corresponding to the required braking force, the value of the control signal is changed with a gentler time gradient than the time gradient of the response of the hydraulic pressure to the control signal.

Further, in the braking control device according to claim 6 of the present invention, when the switching means satisfies the first predetermined condition and the second predetermined condition is not satisfied, the hydraulic braking force is set as the hydraulic braking force. The feature is that the acting hydraulic pressure is rapidly increased to a hydraulic pressure equivalent to the required braking force.

[0017]

In the braking control device according to the first aspect of the present invention, the vehicle is normally braked by the hydraulic braking means and the regenerative braking means by the braking force distribution giving priority to the regenerative braking force. When the predetermined condition is satisfied, a hydraulic pressure transmission path that bypasses the differential pressure valve is formed, and the hydraulic braking force increases. At that time, the hydraulic pressure transmission path that bypasses the differential pressure valve is gradually formed. That is, the hydraulic pressure acting as the hydraulic braking force is gradually increased until the hydraulic pressure corresponding to the required braking force is reached. If such a gradual increase control is performed when switching to braking that increases the hydraulic braking force, the problem that the pedal depression suddenly becomes deep does not occur.

In the braking control device according to the second aspect of the present invention, the vehicle is normally braked by the hydraulic braking control means and the regenerative braking control means by the braking force distribution giving priority to the regenerative braking force. When the first predetermined condition is satisfied,
The regenerative braking force is cut off, and at the same time, a hydraulic pressure transmission path that bypasses the differential pressure valve is formed. In this state, braking is performed only by the hydraulic braking force. In the second aspect, when the second predetermined condition is satisfied in addition to the first predetermined condition, the hydraulic pressure transmission path that bypasses the differential pressure valve is further gradually formed. That is, the hydraulic pressure acting as the hydraulic braking force is
Gradual increase control is performed until a hydraulic pressure equivalent to the required braking force is reached. If such a gradual increase control is performed when switching to braking by only the hydraulic braking force, the problem that the pedal depression suddenly becomes deep does not occur. Therefore, an electric vehicle with improved brake feeling can be obtained.

In the third aspect of the present invention, a switching valve for forming the hydraulic pressure transmission path in response to the control signal is further provided as means for forming the hydraulic pressure transmission path that bypasses the differential pressure valve. When performing the above-mentioned gradual increase control, the switching means performs intermittent control of the control signal given to the switching valve. That is, the control signal given to the switching valve is intermittently made in a time unit shorter than the response time of the hydraulic pressure to the control signal, and the formation and interruption of the above-mentioned path are repeated (duty control of the switching valve). When such control is performed, the hydraulic pressure on the wheel side does not change in the state where the control signal is temporarily cut off.Therefore, the request control is started after the control related to switching to braking by only the hydraulic braking force is started. It takes a long time until the hydraulic pressure equivalent to power is obtained on the wheel side. Therefore, by performing duty control using such a switching valve, the above-described gradual increase control is preferably realized. At that time, analog control is not required.

Further, according to the fourth aspect, when such duty control is performed, the duty ratio of the control signal is appropriately changed and controlled. That is, the duty control may be performed so that the formation time of the hydraulic pressure transmission path that bypasses the differential pressure valve becomes longer or the cutoff time becomes shorter. When such control is performed, the gradient of increase in hydraulic pressure can be further suppressed, and the effect of improving the brake feeling becomes more remarkable.

In the gradual increase control according to the fifth aspect of the present invention, instead of the switching valve that forms / shuts off the hydraulic pressure transmission path according to the control signal, the differential pressure valve is bypassed while generating a differential pressure having a value according to the control signal. It is realized by a switching valve that forms a hydraulic pressure transmission path. When such a switching valve is used, the switching means performs continuous change control of the control signal value, not duty control. That is, the value of the control signal is changed with a gentler time gradient than the time gradient of the response of the hydraulic pressure to the control signal, and the control signal is supplied to the switching valve. Then, since the hydraulic pressure on the wheel side gradually increases as compared with the conventional case, the gradual increase control described above is also suitably realized.

In the sixth aspect of the present invention, when the first predetermined condition is satisfied and the second predetermined condition is not satisfied, the hydraulic pressure acting as the hydraulic braking force is the required control. Sudden increase control up to hydraulic pressure equivalent to power. That is, when a sudden increase in the hydraulic braking force is required, the hydraulic pressure is increased as rapidly as in the conventional case.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment 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 an embodiment of the present invention. In this figure, the hydraulic pressure transmission path from the master cylinder to each wheel cylinder is shown by solid lines, and the flow of control signals and detection signals related to hydraulic pressure and regenerative braking is shown by broken lines. The flow of electric power for driving the motor is indicated by a thick line.

The electric vehicle shown in this figure includes a three-phase AC motor 10 as a traveling motor. The output shaft of the three-phase AC motor 10 is connected to the drive wheels W _FL and W _FR via the speed reducer 12, the drive shaft 13, and the like. The subscript F is the front wheel, L is the left wheel, R is the right wheel,
Each means. Therefore, the drive wheels W _FL and W _FR are rotated by the rotational driving of the motor 10.

A battery 14 is mounted as an energy source of the motor 10. The battery 14 is connected to the inverter 18 and the motor 10 via the main relay 16. When the main relay 16 is on, the discharge power of the battery 14 is supplied to the inverter 18. Under the control of the motor ECU 20, the inverter 18 converts the DC power supplied from the battery 14 into three-phase AC power and supplies the three-phase AC power to the motor 10. Motor ECU 20
Is information on the accelerator pedal depression by the vehicle operator and the motor 1 when controlling the inverter 18.
Information such as the motor rotation speed N obtained by the rotation speed sensor 22 attached to 0 is input, and switching of each switching element forming the inverter 18 is controlled by a PWM (pulse width modulation) signal. By performing the control in such a procedure, the output torque of the motor 10 becomes a torque corresponding to the depression of the accelerator pedal by the vehicle operator.

The electric vehicle shown in this figure has both a hydraulic braking function and a regenerative braking function as a braking function.

First, as a mechanism for hydraulic braking, a master cylinder (M / C) 26 is provided which generates hydraulic pressure in response to depression of the brake pedal 24. Each chamber of the master cylinder 26 is connected to each wheel cylinder 28FL, 28FR, 28 via a hydraulic pressure transmission path indicated by a solid line in the figure.
It is connected to RL and 28RR. The subscript R following 28 means the rear wheel. 28FL and 28FR of these wheel cylinder is driven wheels _{W FL} and _{W FR}
Is provided corresponding to, 28RL and 28RR are provided so as to correspond to the non-driven wheels _{W RL} and _{W RR.}

Master cylinder 26 and wheel cylinder 28
A differential pressure valve 30F is provided between FL and 28FR. Similarly, the master cylinder 26 and the wheel cylinder 2
A differential pressure valve 30R is provided between 8RL and 28RR. The differential pressure valves 30F and 30R are the master cylinder 26
It is a valve for generating a differential pressure between the hydraulic pressure (master cylinder pressure) in (1) and the corresponding hydraulic pressure (wheel cylinder pressure) in the wheel cylinder. That is, the master cylinder pressure takes a state until the P ₀ which closed differential pressure valve 30F and 30R shown in FIG. 7, the differential pressure P ₀ exceeds P ₀
While maintaining, transmit the master cylinder pressure to the wheel cylinder side. As a result, as shown in FIG.
A hydraulic braking force that changes as shown in FIG.

Further, switching hydraulic valves 32F and 32R are provided in parallel with the differential pressure valves 30F and 30R. These switching hydraulic valves 32F and 32R are opened and closed according to a control signal from a regenerative ECU 34 described later. The switching hydraulic valves 32F and 32R are
It constitutes the feature of this embodiment. However, the switching hydraulic valve 32
Instead of F and 32R, a differential pressure valve (solenoid valve or the like) whose valve opening value can be controlled may be used.

Wheel cylinders 28FL, 28FR, 28
An ABS control device 36 is further provided on the master cylinder 26 side when viewed from the RL and 28RR. Although not shown in detail in this figure, the ABS controller 36
Is composed of a predetermined number of valves and pumps. AB
The SECU 38 controls the ABS control device 36.

The regenerative ECU 34 normally controls the braking force E so that the distribution shown in FIG. 7 is realized.
CU. The regenerative ECU 34 detects the braking force required by the vehicle operator as the master cylinder pressure by the hydraulic pressure sensor 40 attached to the master cylinder 26. Further, the regenerative ECU 34 detects the wheel cylinder pressure using the hydraulic pressure sensor 42 attached to the wheel cylinders 28FL and 28FR, and uses this wheel cylinder pressure together with the master cylinder pressure so that the differential pressure regulating valves 30F and 30R are controlled by the master cylinder. The hysteresis characteristic possessed by the cylinder pressure is dealt with. The regenerative ECU 34 performs necessary communication with the motor ECU 20 and the ABS ECU 38 in controlling the braking force. The regenerative ECU 34 detects the voltage of the battery 14 by the voltage sensor 44 and the current by the current sensor 46, respectively. Then, the regenerative ECU 34 inputs whether or not the vehicle operator depresses the brake pedal 24 as a state of the brake switch 48 attached to the brake pedal 24.

FIG. 2 shows a regenerative ECU in this embodiment.
The flow of the operation of is shown. As shown in this figure, the regenerative ECU 34 first initializes various parameters used in the control described later (100), and then shifts to the repeating operation after step 102.

In step 102, the regenerative ECU 3
Reference numeral 4 performs an initial check such as the presence or absence of disconnection of connection with various solenoids (not shown) and other ECUs (for example, motor ECU 20, ABS ECU 38, etc.). When the necessary conditions are not satisfied in the initial check, the regenerative ECU 34 executes steps 104 and 106.
That is, an instruction is given to the motor ECU 20 so that the regenerative torque of the motor 10 becomes zero, and the relays and solenoids forming the switching hydraulic valves 32F and 32R are controlled to be off, and the master cylinder pressure becomes the wheel cylinder pressure as it is. Cause such a situation. This state continues until the initial check is established.

After the initial check is established, regenerative E
The CU 34 determines whether the vehicle can be started (108). That is, the shift position given by the operation of the vehicle operator is one of P (parking), N (neutral) and B (back), and the motor E
It is determined whether the regeneration inhibition signal FREG is not supplied from the CU 20 and the predetermined fail-safe condition is not satisfied. If this determination is not established, steps 104 and 106 described above are executed. When the condition is satisfied, the operations after step 110 are executed.

In step 110, the switching hydraulic valve 3
The relays forming 2F and 32R are turned on. This relay is a relay for coping with an abnormality in the drive circuit of the solenoid that constitutes the switching hydraulic valves 32F and 32R.
After executing step 110, the regenerative ECU 34 determines the motor rotation speed N based on the output of the rotation speed sensor 22, and further determines the slip state based on the calculated motor rotation speed N and the time change rate thereof (114). After step 114, the regenerative ECU 34 determines the shift position (116).
That is, the regenerative ECU 34 determines which position the shift position is, and also detects an abnormality such as a detection result indicating that the shift position is not present or an abnormality such as a plurality of shift positions. When is detected, predetermined processing is executed.

The regenerative ECU 34 subsequently determines whether or not the regenerative inhibit signal FREG is present (118). The regeneration inhibition signal FREG is a signal generated by the motor ECU 20, and for example, when the inverter 18 is abnormal, when the main relay 16 is abnormal, or when the communication between the motor ECU 20 and the regeneration ECU 34 is abnormal. And so on. In addition to this, the regeneration prohibition signal FREG may be generated when the voltage of the battery 14 is abnormal or when the shift position is any one of P, N, and B. If the regeneration inhibition signal FREG is generated, the regeneration ECU 34 executes steps 104 and 106, and if not generated, the following step 120 is executed. In step 120, the regenerative ECU 34 determines whether or not the ABS control device 36 is operating based on the ABS operation signal ABSA supplied from the ABS ECU 38. If it is determined that the ABS control device 36 is operating, the regenerative ECU 3 is uneasy because the gradual increase control described later is uneasy.
4 also performs steps 104 and 106.

When the regenerative ECU 34 determines that the ABS control device 36 is not operating, the brake switch 48 is activated.
It is determined whether or not is on (122). As a result, when it is determined that the vehicle is on, it can be considered that the vehicle operator has stepped on the brake pedal 24 and therefore braking is requested.
A required regenerative torque is calculated according to this depression and according to a predetermined braking force distribution (124). Regenerative ECU 34
Adjusts the calculated regenerative torque based on the temperature of each component of the electric vehicle, the voltage of the battery 14, and the like, and gives a command to the motor ECU 20 to output the adjusted regenerative torque from the motor 10. (126).

On the other hand, when it is determined that the brake switch 48 is off, if there is no difference between the master cylinder pressure and the wheel cylinder pressure (128),
A command is given to the motor ECU 20 so that the regenerative torque output from the motor 10 becomes zero (130). If there is a difference between the master cylinder pressure and the wheel cylinder pressure (128), step 1 in this embodiment.
24 and 126 are executed. That is, although the signal indicating that the brake switch 48 is off is input to the regenerative ECU 34, when the brake pedal 24 is actually stepped on and braking is requested, regenerative braking is performed. Done.

After executing step 126 or 130, steps 132 to 138 are executed. In step 132, the regenerative ECU 34 determines whether or not the voltage of the battery 10 is abnormal. When it is determined that there is no abnormality, the regenerative ECU 34 uses the response value from the motor ECU 20 that indicates how much regenerative torque is actually output with respect to the regenerative torque commanded to the motor ECU 24.
It is determined whether there is an abnormality (134). That is, it is determined whether or not the difference between the previous command value and the reply value is large. As a result, if it is determined that there is no large difference, the regenerative E
The CU 34 determines whether the shift position is any one of P, N, and B (136). If the shift position is not in P, N or B, step 14
Go to 0.

If any of the conditions of steps 132, 134 and 136 is satisfied, step 138 is executed. In step 138, the control of the switching hydraulic valves 32F and 32R is performed so that the wheel cylinder pressure gradually increases to the master cylinder pressure. This control is started, for example, by setting a flag indicating control execution on the regenerative ECU 34 side, and a drive circuit built in or attached to the switching hydraulic valves 32F and 32R detects this flag.

Next, in step 140, step 11
It is determined whether the drive wheels W _FL and W _FR are in the slip state based on the slip determination state in No. 4, and if the drive wheels W _FL and W _FR are in the slip state, step 142 is executed. In step 142, the non-driving wheels W _RL
By controlling the switching valve 32R on the W and W _RR sides, control is performed so that the wheel cylinder pressures of the non-driving wheels W _RL and W _RR gradually increase to the master cylinder pressure. In this control, for example, a flag indicating control execution is set on the regenerative ECU 34 side,
The drive circuit built in or attached to the switching hydraulic valves 32R on the non-drive wheels W _RL and W _RR side starts by detecting this flag.

FIG. 3 shows step 1 in this embodiment.
An example of the wheel cylinder pressure gradual increase control at 38 is shown. In this figure, the control signals (flags) given from the regenerative ECU 34 to the switching hydraulic valves 32F and 32R have an on value, and therefore these valves 32F and 32R are on.
The control starts from the state where is closed. After the control is started, ON / OFF of the control signal supplied to the switching hydraulic valves 32F and 32R is controlled with a constant duty (for example, 50%). The wheel cylinder pressure is the switching hydraulic valves 32F and 3
Since 2R starts rising as soon as 2R is opened, and has a constant value while closed, the time until the wheel cylinder pressure reaches the master cylinder pressure is controlled by performing such constant duty ON / OFF control. It will be longer. That is, as shown in FIG. 4, the switching hydraulic valves 32F and 3F.
Compared to the case where 2R is opened immediately in response to the flag generation, the time required for the wheel cylinder pressure to reach the master cylinder pressure becomes longer. Therefore, the brake pedal 24 is suddenly depressed when switching to braking by only the hydraulic braking force. Problems such as deepening are prevented. This improves the brake feeling. In addition, the circuit used for this control may be small in scale, which is advantageous in terms of cost. Further, it is not necessary to provide an orifice or the like, and it can be used together with the ABS control device 36 and the like.

FIG. 5 shows another example of the wheel cylinder pressure gradual increase control that can be executed in this embodiment. In this control, after the switching hydraulic valves 32F and 32R are opened, the valves 32F and 32R are turned on / off (open / closed).
Is PWM controlled. That is, as the wheel cylinder pressure gradually increases, the switching hydraulic valves 32F and 32R are changed.
The control signals supplied to the switching hydraulic valves 32F and 32R are PWM-modulated so that the open period of the switch is gradually increased and the close period thereof is gradually decreased. When such control is performed, as is apparent from comparison with FIG. 3, the switching hydraulic valve 32
Immediately after the F and 32R are opened, the increasing gradient of the wheel cylinder pressure becomes gentle, and the trouble that the depression of the brake pedal 24 suddenly becomes deeper is alleviated.

FIG. 6 shows another example of the wheel cylinder pressure gradual increase control that can be adopted in this embodiment.
In this embodiment, instead of the switching hydraulic valves 32F and 32R, a differential pressure valve capable of continuously changing the generated differential pressure is used. When such a valve is used, the wheel cylinder pressure can be gradually increased by gradually and continuously changing the value of the control signal supplied from the regenerative ECU 34. The effect is still obtained.

The wheel cylinder pressure gradual increase control executed in step 138 has been described above.
Similarly, the wheel cylinder pressure gradual increase control of the non-driving wheels WRL and WRR executed in FIG.
The gradual increase control indicated by is performed.

Although hydraulic pressure is used for hydraulic braking in the above embodiments, other liquids or incompressible liquids may be used as the pressure transmission medium. further,
The process of shifting to the hydraulic pressure gradual increase control may be performed as an interrupt process. Further, the migration processing is not limited to the above.

[0048]

As described above, according to the present invention as set forth in claim 1, the hydraulic pressure acting as the hydraulic braking force is gradually increased to the hydraulic pressure corresponding to the required braking force when the predetermined condition is satisfied. Therefore, when switching to the braking state in which the hydraulic braking force is increased, the pedal depression depth does not change and the brake feeling does not deteriorate, and an electric vehicle capable of braking without a feeling of discomfort can be obtained.

According to the second aspect of the present invention, when the second predetermined condition is satisfied in addition to the first predetermined condition, the hydraulic pressure acting as the hydraulic braking force is gradually increased to the hydraulic pressure corresponding to the required braking force. Therefore, when switching to the braking state only by the hydraulic braking force, the change in the depth of depression of the pedal does not occur and the brake feeling is not deteriorated, and an electric vehicle capable of braking without discomfort is obtained.

Further, according to the third aspect of the present invention, since the switching valve which forms the hydraulic pressure transmission path bypassing the differential pressure valve according to the control signal is used and the duty control of the switching valve is performed, the hydraulic pressure is controlled. It is possible to preferably realize the gradual increase control of. In addition, the switching valve used at that time is a relatively inexpensive on / off
Since the off valve is sufficient, the device cost is low and the electric vehicle is easier to realize.

Further, according to the fourth aspect of the present invention, the duty ratio related to the duty control is changed as the hydraulic pressure gradually increases. Therefore, the hydraulic pressure (wheel cylinder pressure) is changed.
It becomes possible to suppress the gradient related to the gradual increase in the electric vehicle, and the electric vehicle has improved brake feeling.

Further, according to the fifth aspect of the present invention, the switching valve for generating the differential pressure according to the control signal is used to form the hydraulic pressure transmission path that bypasses the differential pressure valve. By changing the value of the control signal with a gentle gradient, it becomes possible to preferably realize the above-described gradual increase control.

According to claim 6 of the present invention, the first
When the second predetermined condition is satisfied and the second predetermined condition is not satisfied, the hydraulic pressure is increased rapidly without performing the gradual increase control. Therefore, the hydraulic braking force is rapidly increased while suppressing the deterioration of the brake feeling. Appropriate when necessary.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing a flow of operations of a regenerative ECU in this embodiment.

FIG. 3 is a time chart showing an example of wheel cylinder pressure gradual increase control in this embodiment.

FIG. 4 is a time chart showing a change in wheel cylinder pressure that has been caused by conventional control of a switching hydraulic valve.

FIG. 5 is a time chart showing another example of the wheel cylinder pressure gradual increase control in the present embodiment.

FIG. 6 is a time chart showing another example of the wheel cylinder pressure gradual increase control in the present embodiment.

FIG. 7 is a diagram showing an example of distribution of regenerative braking force and hydraulic braking force.

FIG. 8 is a diagram showing a braking force distribution when bypassing the differential pressure valve and applying only hydraulic braking force to perform braking.

[Explanation of symbols]

10 Motor 14 Battery 16 Main Relay 18 Inverter 20 Motor ECU (Electronic Control Unit) 22 Rotation Speed Sensor 24 Brake Pedal 26 Master Cylinder (M / C) 28FL, 28FR, 28RL, 28RR Wheel Cylinder (W / C) 30F, 30R Difference Pressure valve 32F, 32R Switching hydraulic valve 34 Regenerative ECU 36 ABS (anti-lock brake system) control device 38 ABS ECU 40, 42 Hydraulic pressure sensor 44 Voltage sensor 46 Current sensor 48 Brake switch

Claims (6)

[Claims] 1. A hydraulic braking control means for generating a hydraulic braking force smaller than the required braking force by transmitting a hydraulic pressure equivalent to the required braking force to the wheels via a differential pressure valve, and the required braking force and the hydraulic braking force. And a regenerative braking control means for generating a regenerative braking force corresponding to the difference between the two, and when a predetermined condition is satisfied, switching to switch to braking with increased hydraulic braking force by forming a hydraulic pressure transmission path that bypasses the differential pressure valve. In a braking control device mounted on an electric vehicle, the switching means forms a hydraulic pressure transmission path that bypasses the differential pressure valve, and a hydraulic pressure acting as a hydraulic braking force is equivalent to a required braking force. A braking control device characterized in that the hydraulic pressure is gradually increased to the hydraulic pressure. 2. A hydraulic braking control means for generating a hydraulic braking force smaller than the required braking force by transmitting a hydraulic pressure equivalent to the required braking force to the wheel side via a differential pressure valve, and the required braking force and the hydraulic braking force. The regenerative braking control means for generating a regenerative braking force corresponding to the difference between
By forming a hydraulic pressure transmission path that bypasses the regenerative braking force and bypasses the differential pressure valve, there is provided switching means for switching to braking only by hydraulic braking force, and in a braking control device mounted on an electric vehicle, The switching means gradually increases the hydraulic pressure acting as the hydraulic braking force to the hydraulic pressure corresponding to the required braking force when the second predetermined condition is satisfied when forming the hydraulic pressure transmission path that bypasses the differential pressure valve. A characteristic braking control device. 3. The braking control device according to claim 1 or 2, wherein the hydraulic braking control means has a switching valve that forms a hydraulic pressure transmission path that bypasses the differential pressure valve according to a control signal, and the switching means When gradually increasing the hydraulic pressure acting as the hydraulic braking force to the hydraulic pressure equivalent to the required braking force, the control signal is generated while being intermittently interrupted in a time unit shorter than the response time of the hydraulic pressure to the control signal. Braking control device. 4. The braking control device according to claim 3, wherein the switching unit lengthens the formation time and / or shortens the cutoff time of the hydraulic pressure transmission path that bypasses the differential pressure valve as the hydraulic pressure gradually increases. The braking control device is characterized by changing and controlling a time unit in which the control signal is interrupted. 5. The braking control device according to claim 1 or 2, wherein the hydraulic braking control means forms a hydraulic pressure transmission path that bypasses the differential pressure valve while generating a differential pressure having a value according to the control signal. A switching valve is provided, and when the switching means gradually increases the hydraulic pressure acting as the hydraulic braking force to the hydraulic pressure corresponding to the required braking force, the above-mentioned slower time gradient than the time gradient of the hydraulic pressure response to the control signal is used. A braking control device characterized by changing the value of a control signal. 6. The braking control device according to claim 1, wherein the switching means acts as hydraulic braking force when the first predetermined condition is satisfied and the second predetermined condition is not satisfied. A braking control device characterized in that the pressure is rapidly increased to a hydraulic pressure equivalent to a required braking force.