JP3319659B2 - Braking device for electric vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking device which can be used, for example, in an electric vehicle.

[0002]

2. Description of the Related Art For example, in the case of a general electric vehicle, the only energy that can be used for traveling is the electric power charged to the battery, and the electric power that can be charged to the battery is limited. In order to extend the traveling distance, it is necessary to effectively use the energy of the vehicle.
Therefore, the use of regenerative braking in an electric vehicle is a very effective means. In other words, when braking, the electric motor connected to the wheels is driven by the kinetic energy of the vehicle, and the electric power generated by the electric motor is returned to the battery, so that wasteful consumption of energy is reduced. be able to.

However, since there is a limit in regenerative braking, if the regenerative braking is exceeded, the hydraulic brake is used to supplement the brake, and the hydraulic brake is used in combination with the regenerative braking.

[0004] In a conventional automobile braking system, the distribution of the front-wheel braking force and the rear-wheel braking force is determined so that the characteristic curve called ideal braking force distribution is as close as possible. However, in the case of an electric vehicle, if the distribution of the hydraulic brake of the driven wheel is large, the energy due to the regenerative braking is reduced.
Recovery efficiency is reduced.

To improve the efficiency of energy recovery by regenerative braking, a special regenerative priority mode is provided.
It has been proposed to set the distribution of the front wheel braking force and the rear wheel braking force to a characteristic different from the ideal braking force distribution.

For example, in the technique disclosed in Japanese Patent Application Laid-Open No. 5-161210, a regenerative priority mode is provided in which, in a region where a required braking force is relatively small, all hydraulic brakes are shut off and only regenerative braking is performed. It is. Japanese Patent Laid-Open No. 5-16121
In the technology disclosed in Japanese Patent Publication No. 2 (2003), normally a regeneration priority mode is implemented,
When the road surface friction coefficient is small and wheel lock is detected, automatic control for shifting to the normal mode according to the ideal braking force distribution is performed. Further, in the technique disclosed in Japanese Patent Application Laid-Open No. 5-161213, switching between the regeneration priority mode and the normal mode is performed based on the depression force of the brake pedal or the rate of increase thereof.
Automatically implemented.

[0007]

When the hydraulic braking force is cut off in the regenerative priority mode, a master cylinder for generating a hydraulic pressure in accordance with the stroke of the brake pedal and a master cylinder are provided. The on / off valve inserted in the oil flow passage between the wheel cylinder and the wheel cylinder disposed near the wheel closes. If the brake pedal is depressed to some extent with the on / off valve closed, the hydraulic pressure of the master cylinder increases in accordance with the depressing stroke, but the hydraulic pressure of the wheel cylinder is maintained at a low level. Causes a large differential pressure. In such a state, when the on / off valve is opened in order to switch from the regeneration priority mode to the normal mode, when the wheel cylinder oil pressure approaches the master cylinder oil pressure, the on / off valve is used. Oil flows into the wheel cylinder at once. For this reason, a sudden depression of the brake pedal, the generation of a violent oil sound, and
Shock occurs. Therefore, braking feeling is poor and unstable behavior is likely to occur in the vehicle.

Therefore, when the mode is switched from the regeneration priority mode to the normal mode, it is necessary to use some means to moderate the increase in the oil pressure of the wheel cylinder. However, if the speed of increasing the hydraulic pressure of the wheel cylinders of the front wheels or the rear wheels is too slow, the braking force applied to the entire vehicle does not increase rapidly even if the brake pedal is strongly depressed when the rear wheels or the front wheels are locked. Delay and braking distance (running distance until the vehicle stops) increase.

Therefore, the present invention provides a master cylinder and a wheel.
When the on / off valve interposed in the oil flow path between the oil cylinder and the closed cylinder is switched from the closed state to the open state, the brake pedal suddenly sinks, violent oil noise is generated, and step-like sudden deceleration occurs. It is an object of the present invention to suppress the occurrence of a shock or the like and to prevent the braking distance of the vehicle from being lengthened thereby.

[0010]

According to the present invention, there is provided an on-vehicle battery (1) for storing electric energy; an electric drive means (2) for driving wheels by electric power from the on-vehicle battery. Regenerative braking means (D1 to D6) for returning the electric power generated by the electric drive means to the on-vehicle battery with the rotation of the wheels; hydraulic pressure generation for generating a hydraulic pressure according to the operation amount of the brake pedal Means (4); hydraulic braking means (5 (Fr), 5 (Rr)) for applying a braking force to wheels according to the hydraulic pressure generated by the hydraulic pressure generating means;
And a valve means (6, 56) for restricting transmission of hydraulic pressure from the hydraulic pressure generation means to the hydraulic pressure braking means, wherein the valve is provided when a predetermined condition is satisfied. Releasing the restriction of the means and supplying the hydraulic pressure of the hydraulic pressure generating means to the hydraulic braking means: braking state detecting means (46) for detecting a braking state of a wheel; and the valve satisfying the predetermined condition Switching control means (47, 48) for determining a transition speed of the switching according to the braking state of the wheel detected by the braking state detecting means when the means is switched from the restricted state to the open state.

According to the second aspect of the present invention, when the driving wheel is turned on, the switching control means opens and closes the valve means of the driven wheel in accordance with a duty ratio determined according to the rotation deceleration of the driving wheel. Is repeated.

According to the third aspect of the present invention, the drive wheels connecting the electric drive means are front wheels (FR), and the rear wheels (RR) are driven wheels.

According to a fourth aspect of the present invention, the switching control means includes:
When the predetermined condition is satisfied and the valve means is switched from the restricted state to the open state, the transition speed of the switching is determined according to the degree of decrease in the regenerative braking force (3J.3K,
3L, 3G).

The symbols shown in the parentheses indicate the reference numerals of the corresponding elements in the embodiments described later for reference. However, each component of the present invention is a specific element in the embodiments. It is not limited to only.

[0015]

According to the present invention, when the braking mode is switched,
That is, when the valve means is switched from the restricted state to the open state, the transition speed of the switching is determined according to the braking state of the wheel detected by the braking state detecting means.

For example, when the valve means is an on / off valve means (53) such as a differential pressure valve, when the on / off valve means is switched from the closed state to the open state in order to switch the braking mode, The operation of alternately switching the on / off valve means between the open state and the closed state is repeated. Further, the opening / closing duty ratio of the on / off valve means at this time is automatically determined according to the rotation deceleration of the wheel detected by the deceleration detecting means (46).

If there is a difference between the hydraulic pressure of the hydraulic pressure generating means and the hydraulic pressure of the hydraulic braking means, the hydraulic pressure of the hydraulic braking means is gradually increased by opening and closing the on / off valve means in a short time. It becomes the same as the hydraulic pressure of the pressure generating means. In this case, the hydraulic pressure changing speed of the hydraulic braking means changes according to the opening / closing duty ratio of the on / off valve means. That is, when the opening / closing duty ratio is small (the ratio of the opening time is small), the hydraulic pressure of the hydraulic braking means slowly increases, and when the opening / closing duty ratio is large (the ratio of the opening time is large). Then, the hydraulic pressure of the hydraulic braking means rises in a short time.

When a linear valve is used as the valve means, when the linear valve is switched from the fully closed state to the fully open state in order to switch the braking mode, the opening of the linear valve is gradually increased, for example, stepwise. To be larger. At this time, the inclination of the opening change (opening change speed) is automatically determined according to the rotation deceleration of the wheel detected by the deceleration detecting means (46).

That is, the open / close duty ratio of the on / off valve means or the inclination of the change in the opening degree of the linear valve is automatically determined according to the detected deceleration of the wheel. Preferred braking can be achieved.

For example, in a front-wheel drive vehicle, the front wheels are the drive wheels, and regenerative braking can be performed only on the front wheels. Therefore, during braking, there may be a case where the front wheel is regeneratively braked and the rear wheel is hydraulically braked, or a case where the front wheel is regeneratively braked and the rear wheel is not braked. Here, when the rear wheels are hydraulically braked, the regenerative efficiency is reduced. Therefore, in order to increase the regenerative efficiency, it is conceivable that the rear wheels are not braked. However, if the rear wheels are not braked, the front wheels are likely to be locked on the low μ road. Therefore, for example, when the leading lock of the front wheel occurs, it is necessary to increase the braking force of the rear wheel by applying hydraulic braking to the rear wheel.

According to the first aspect of the present invention, "predetermined conditions"
For example, "when the front wheels are locked", the valve means is opened when the front wheels are locked, and the hydraulic pressure generated by the hydraulic pressure generating means can be directly applied to the hydraulic braking means. Therefore, it is possible to improve the regeneration efficiency and prevent the front wheel leading lock.
In the case where regenerative braking cannot be performed suddenly even on the front wheels that are the driving wheels, open the valve means and apply the generated hydraulic pressure of the hydraulic pressure generating means to the hydraulic braking means as it is, and increase the braking force by hydraulic braking. Can be.

Thus, in the first aspect of the present invention,
By providing a valve means (for example, a differential pressure valve or a linear valve) that opens when a "predetermined condition" is satisfied, regenerative braking efficiency can be increased, and hydraulic braking can be applied under "predetermined condition". .

Here, when the valve means is changed from the closed state to the open state, a shock may be generated in the vehicle because the braking force by the hydraulic braking sharply increases, but in the invention of claim 1, the switching is performed according to the braking state. By changing the transition speed of
This shock can be relieved. The braking state may be estimated from, for example, the rotation deceleration of the wheel, or may be estimated from the locked state or the slip state of the wheel. If the rotation deceleration of the wheel is high, it is easy to lock the front wheel ahead or want to stop the wheel quickly, so at this time or when the wheel is likely to lock, the slip ratio Is higher, the duty ratio for opening and closing the valve means may be increased to increase the braking force quickly.

In the second aspect, the valve means is normally closed for the driving wheel and the driven wheel so that only the hydraulic braking force obtained by subtracting the regenerative braking force from the braking force required by the driver is applied. I have. Therefore, the regeneration efficiency increases. Here, since the driven wheel has a weaker braking force than the driving wheel, the driving wheel is more likely to be locked in advance. Here, for example, the slip ratio of the drive wheel is determined from the wheel speed of the drive wheel and the vehicle body speed by the slip ratio detection means. When the slip ratio exceeds a predetermined value, the lock of the drive wheel starts, and the rotation of the drive wheel decreases. Speed increases rapidly. Since the duty ratio of the valve means is determined according to the rotation deceleration of the driving wheel, the correspondence of the driven wheel can be determined according to the locking condition. For example, if the rotation deceleration of the drive wheel is high, the hydraulic braking force of the driven wheel is quickly increased to prevent the locking of the drive wheel, and if the rotation deceleration of the drive wheel is low, the hydraulic braking force of the driven wheel is slowly increased. And the braking force of the driven wheels can be increased while reducing the shock generated in the vehicle. Therefore, when the preceding lock of the drive wheel occurs, the urgency of the recovery of the preceding lock and the occurrence of the shock of the vehicle are balanced, and a preferable response according to the state of the vehicle can be performed.

An ideal braking force distribution line indicating an ideal distribution of the braking force on the front wheel (Fr) side and the braking force on the rear wheel (Rr) side is as follows:
Generally, this is shown by a virtual line in FIG. As the actual braking force distribution approaches the ideal braking force distribution line, more preferable braking is performed. However, in a region above the ideal braking force distribution line, a behavior such as spinning is likely to occur in the vehicle. Therefore, the actual braking force distribution is generally indicated by a dotted line in FIG. 7 so as not to exceed the ideal braking force distribution line. It is set as follows. In the case of an electric vehicle, the hydraulic braking system is depressurized to increase the efficiency of recovering energy by regenerative braking, and a braking force distribution (regeneration priority mode) as shown by a solid line in FIG. It is desirable. However, when the slip ratio of the front wheels is large, there is a high possibility that the front wheels are locked, and when the front wheels are locked, the braking force of the front wheels does not increase any more. Therefore, when the slip ratio of the front wheels is large, the braking force of the rear wheels is increased to bring the braking force distribution closer to the ideal braking force distribution line (the distribution indicated by the dotted line in FIG. 7).

According to the third aspect of the present invention, since the drive wheels connecting the electric drive means are the front wheels (FR) and the rear wheels (RR) are the driven wheels, if the braking force distribution is determined, for example, as shown by a solid line in FIG. As a result, the kinetic energy of the vehicle is consumed at a higher rate by the front wheels that are the driving wheels than at the rear wheels that are the driven wheels, and the energy can be recovered with high efficiency by regenerative braking of the driving wheels.

According to a fourth aspect of the present invention, when the predetermined condition is satisfied and the valve means is switched from the restricted state to the open state, the switching transition speed is determined according to the degree of decrease in the regenerative braking force.

For example, when an abnormality appears in the voltage, current, temperature, etc. of the motor which is the driving source of the electric vehicle and the inverter for supplying electric power during regenerative braking, the regenerative braking is performed. In this case, it is necessary to stop the braking and switch to the hydraulic braking. In such a case, the switching is required immediately (when the regenerative braking is impossible), and when the switching is performed slowly, no problem occurs. There is. In the latter case,
By slowly increasing the hydraulic braking force, the shock generated in the vehicle can be reduced. But,
If the reduction curve of the regenerative braking force is different from the increase curve of the hydraulic braking force at the time of this switching, the braking force (hydraulic force) is maintained at the time of the switching even if the brake pedal is constantly depressed. (Pressure braking force + regenerative braking force) temporarily fluctuates. According to the fourth aspect, the curve for increasing the hydraulic braking force is determined according to the degree of decrease in the regenerative braking force. Therefore, when switching, the hydraulic braking force is increased so as to compensate for the decrease in the regenerative braking force. It is possible to increase and suppress the fluctuation of the braking force.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the structure of a driving system and a braking system of an electric vehicle according to an embodiment. Referring to FIG. 1, in this embodiment, a front wheel Fr is a driving wheel, and a rear wheel Rr is a driven wheel. A drive shaft of the electric motor 2 as a drive source is connected to an axle of the front wheels Fr via a transmission (T / M) 25. In FIG. 1, one of the front wheels Fr and one of the rear wheels Rr are omitted, but the automobile of the embodiment is a four-wheeled vehicle. A wheel cylinder (W / C) 5 for hydraulic braking is mounted near each wheel. Since the front wheels Fr are drive wheels, regenerative braking by the electric motor 2 is also possible.

First, the hydraulic system shown in FIG. 1 will be described. A hydraulic pressure corresponding to the stroke of depression of the brake pedal 21 is generated at the output of the brake master cylinder (M / C) 4 and is supplied to a pipe 61 on the front wheel side and a pipe 62 on the rear wheel side. A relief valve 6, a check valve 29, a bypass valve 7, and an initial pressure cut valve 51 are inserted in parallel in a flow path connecting the pipe 61 and the pipe 63 of the wheel cylinder 5 (Fr) on the front wheel side. ing. The pressure sensor 11 is installed in the pipe 61, and the pressure sensor 12 is installed in the pipe 63.

Piping 62 and rear wheel-side wheel cylinder 5
A flow path connecting the (Rr) side pipe 64 is provided with a relief valve 5.
6, a check valve 54, a bypass valve 53, an initial pressure cut valve 55, and a bypass valve 52 are inserted in parallel. The bypass valve 52 has a role of releasing the pressure reduction of Rr in the event of a Fr failure. Also, the pipe 64 and the wheel cylinder 5 (R
r), a proportioning valve 23 is interposed.

The relief valve 6 is arranged so that the hydraulic pressure of the pipe 61 is
3. Open when the oil pressure is higher than the hydraulic pressure of
1 and the pressure difference between the pipe 63 are controlled to be constant. Check valve 29
Is usually closed, but the piping 61
When the oil pressure of the pipe 63 becomes higher than the oil pressure of
The hydraulic pressure of 3 is released to the pipe 61. The bypass valve 7 is an electromagnetic valve, which is normally closed. However, when a failure occurs mainly in the electric system, the bypass valve 7 is controlled to open so that the hydraulic pressure of the pipe 61 and the hydraulic pressure of the pipe 63 are equalized. The initial pressure cut valve 51 is opened when the hydraulic pressure of the pipe 61 is extremely low, and is closed when the hydraulic pressure becomes a predetermined value or more (when the initial pressure application to the wheel cylinder 5 (Fr) is completed).

Similarly, the relief valve 56 opens when the oil pressure of the pipe 62 is higher than the oil pressure of the pipe 64 by a predetermined amount or more, and mechanically controls the pressure difference between the pipe 62 and the pipe 64 to be constant. The check valve 54 is normally closed, but opens when the oil pressure of the pipe 64 becomes higher than the oil pressure of the pipe 62 for some reason, and releases the oil pressure of the pipe 64 to the pipe 62. Bypass valve 5
Reference numeral 3 denotes an electromagnetic valve which is normally closed, but is controlled to be opened mainly when a failure occurs in the electric system, so that the piping 62
And the oil pressure of the pipe 64 are made the same. The initial pressure cut valve 55 is opened when the hydraulic pressure of the pipe 61 is extremely small, and is closed when the hydraulic pressure becomes a predetermined value or more (when the initial pressure application to the wheel cylinder 5 (Rr) is completed). The bypass valve 52 is
It is normally closed, but is opened when the oil pressure of the pipe 62 becomes higher than the pipe 61 by a predetermined value or more. Usually, the hydraulic pressure of the pipe 61 and the hydraulic pressure of the pipe 62 are the same.

When the input hydraulic pressure on the master cylinder 4 side is lower than a predetermined pressure, the proportioning valve 23
The output hydraulic pressure on the cylinder 5 (Rr) side is made the same as the input hydraulic pressure, and when the input hydraulic pressure exceeds the predetermined pressure, the input and output sides are separated so that the output hydraulic pressure with respect to the change in the input hydraulic pressure. It operates so as to suppress the rate of change of. By providing the proportioning valve 23, the braking force distribution of the front and rear wheels by hydraulic braking can be made to have a broken line characteristic as shown by a dotted line and a solid line in FIG.

A brake switch 22 for detecting whether or not the brake pedal 21 is depressed is provided near the brake pedal 21. The potentiometer 28 is connected to an accelerator pedal (not shown) and detects a depression stroke of the accelerator pedal. In the vicinity of each wheel, a wheel speed sensor 57, 5 for detecting each wheel speed is provided.
8 are installed.

Next, the electric system will be described. The electric motor 2 used in this embodiment is an induction motor, and the rotor has magnetic poles formed by permanent magnets.
Three-phase windings are installed on the stator. By applying AC power to the three-phase windings of the stator, a rotating magnetic field is generated and the rotor can be driven to rotate. Further, when the rotor of the electric motor 2 is rotating due to the rotation of the wheels, a braking magnetic field can be applied by generating a magnetic field in a direction of stopping the rotation in the winding of the stator. The electromotive force generated in the child winding can be recovered by the power supply (regenerative braking). Inside the electric motor 2, a detector 2a for detecting the position of the magnetic pole of the rotor is provided.

As an electric circuit for controlling the electric motor 2, a motor ECU 27 and a brake ECU 26 are provided. Each of the motor ECU 27 and the brake ECU 26 includes a microcomputer therein. The former mainly controls the driving of the electric motor 2, and the latter mainly controls the hydraulic braking and the regenerative braking. carry out. The two microcomputers are connected to each other so that information can be exchanged with each other.

FIG. 2 shows the structure of the main part of the motor ECU 27. Referring to FIG. 2, the motor ECU 27 is provided with an inverter INV, and three output lines L1, L2 and L3 of the inverter INV are connected to respective windings of the electric motor 2. . Power line LP of inverter INV
And LM are connected to the plus and minus terminals of the on-vehicle battery-1, respectively. For example, a lead-acid battery may be used as the vehicle battery-1, but a large-capacity capacitor or a sub-battery may be connected in parallel with the lead-acid battery.

This inverter INV has six switching output transistors Q1, Q2, Q3, Q4, Q
5 and Q6, and the upper transistor Q1,
By turning on at least one of Q3 and Q5 and at least one of the lower transistors Q2, Q4 and Q6, current can flow from the battery-1 to each winding of the electric motor 2. However, transistors Q1, Q2, Q
3 and Q4, and Q5 and Q6 are not turned on at the same time.

Transistors Q1, Q2, Q3, Q4, Q
5 and Q6 have control terminals of drivers DV1 and DV1, respectively.
The outputs of DV2, DV3, DV4, DV5 and DV6 are connected, and the input terminals of these drivers DV1 to DV6 are respectively connected to the output ports of the microcomputer CPU. That is, a microcomputer CPU
Are transistors Q1, Q2, Q3, Q4, Q5 and Q6.
By controlling ON / OFF of the motor, the energization of each winding of the electric motor 2 is controlled.

In order to continuously rotate the electric motor 2, the positions of the magnetic poles formed by the stator windings are sequentially adjusted in the direction of driving the rotor in accordance with the position of the magnetic poles of the rotor. Need to be moved to the
The PU determines the timing of the control signal applied to the drivers DV1 to DV6 based on the signal from the detector 2a built in the electric motor 2.

By adjusting the timing of control signals applied to the drivers DV1 to DV6, the electric motor can be controlled.
The rotation of the motor 2 can be braked. At the time of this braking, the electric motor 2 functions as a generator, so that electric power is induced in its stator winding, but this electric power is recovered by the battery-1.

That is, when the voltage of the output line L1 becomes higher than that of the power supply line LP due to the back electromotive force generated by the stator winding, a current flows from the output line L1 to the power supply line LP via the diode D1, When the voltage of the output line L1 becomes lower than the power supply line LM, the output line L1
From the power supply line LM via the diode D2, and the battery-1 is charged. Similarly, the output line L
2 becomes higher than the power supply line LP, a current flows from the output line L2 to the power supply line LP via the diode D3, and the voltage of the output line L2 becomes higher than the power supply line LM.
Lower than the output line L2 to the diode D4.
, A current flows to the power supply line LM, and the battery-1 is charged. Further, when the voltage of the output line L3 becomes higher than the power supply line LP, a current flows from the output line L3 to the power supply line LP via the diode D5, and when the voltage of the output line L3 becomes lower than the power supply line LM, Power line L from output line L3 via diode D6
A current flows through M, and battery-1 is charged.

The description will be continued with reference to FIG. The motor ECU 27 detects the depression amount of the accelerator pedal based on the signal output from the potentiometer 28, and controls the driving amount (rotation speed) of the electric motor 2 according to the depression amount. The regenerative braking is executed by the brake ECU 26.
, The braking amount of the electric motor 2 is controlled in accordance with the instruction. By adjusting the pulse width of the signal applied to the control terminals of the transistors Q1, Q2, Q3, Q4, Q5 and Q6 of the inverter INV, the driving torque and the braking amount of the electric motor 2 are adjusted. .

The brake ECU 26 includes a pressure sensor 11
, A signal from the pressure sensor 12, a signal from the brake switch 22, a signal from the transmission 25, and a signal from the electric motor 2. Brake ECU 26
Performs braking control based on these input signals, outputs information for regenerative braking to the motor ECU, and activates the bypass valves 7 and 53 as necessary for hydraulic braking. On / off control.

The main part of the operation of the microcomputer provided in the brake ECU 26 is shown in FIGS. First, a description will be given with reference to FIG. When the power is turned on, initialization is first performed in step 31, and the process proceeds to step 32.

In step 32, the state of the ignition switch (IG_SW) is referred to, and the process waits while the switch is off. When the switch is turned on, the process proceeds to the next step 33. At step 33, the flag FA is referred to, and at step 34, the flag FB is referred to. When the flags FA and FB are both 0, the process proceeds to step 35. When the FA is 0 and the FB is not 0, the process proceeds to step 36. When the FA is not 0, the process proceeds to step 37.
Proceed to.

In step 35, the bypass valve 53 is closed (energization ON), and in the next step 36, the bypass valve 7 is closed (energization ON). By closing the bypass valve 53, the oil pressure at the output of the master cylinder 4 becomes equal to or higher than a predetermined value (ΔPr:
Until the pressure is determined by the relief valve 56), no oil pressure other than the initial pressure is applied to the wheel cylinder 5 (Rr). Further, by closing the bypass valve 7, the hydraulic pressure of the output of the master cylinder 4 becomes higher than a predetermined value (ΔPr: the relief valve 6).
Until the wheel cylinder 5 (F
No oil pressure other than the initial pressure is applied to r).

In step 37, the state of the electric motor 2 is detected. Specifically, the presence or absence of a failure of the electric motor 2, the current rotational speed (rpm) of the electric motor 2, the temperature of the electric motor 2, the voltage and current of the motor, and the Enter information. In the next step 38, the state of battery-1 is detected. Specifically, information on the presence or absence of a failure in the battery 1, the depth of discharge of the battery 1, and the temperature of the battery 1 are input. In the next step 39, the state of the transmission 25 (shift position) is detected.

In step 3A, steps 37 and 3
Based on the information input at 8, 39, etc., it is determined whether or not the condition for performing the regenerative braking is satisfied. In this embodiment, when all of the following conditions are satisfied,
"Regenerative braking is possible".

A. Both motor and inverter are not out of order, b. Within a predetermined range where the motor and inverter voltages operate normally, c. Within a predetermined range where the motor and inverter currents operate normally, d. Within a predetermined range where both motor and inverter temperatures operate normally, e. The motor speed is within the range that the shaft, bearings and gears can withstand, f. The voltage of the battery is within a predetermined range (a voltage sufficient for operating the motor and the inverter normally, and a voltage not causing electrolysis), g. The battery current is within its allowable current range, h. The depth of discharge of the battery is within a chargeable range, i. The temperature of the battery is within its normal operating range, and j. The shift position of the transmission is other than reverse or neutral.

In the next step 3D, first, the pressure sensor 1
1 inputs information on the master cylinder pressure Pm detected, and then inputs information on the wheel cylinder pressure Pw detected by the pressure sensor 12, and compares Pm with Pw. If Pm = Pw, the process returns to the step 32 through the step 3B; otherwise, the process proceeds to the step 3E.

In step 3B, it is determined whether or not the regeneration is in the prohibited state with reference to the identification result in step 3A. In step 3C, the flag FB is cleared, the bypass valve 53 is opened (energization off), the bypass valve 7 is opened (energization off), the flag FA is set to 1, and the process returns to step 32. By opening the bypass valves 53 and 7, the hydraulic pressure output from the master cylinder 4 is directly applied to the wheel cylinder 5 (Fr) and the pipe 64.

In step 3E, the identification result in step 3A is referred to. If the result of step 3A is not "regenerative braking possible", that is, if the regenerative braking operation satisfies the condition that the regenerative operation should be prohibited due to a failure or the like, it is regarded as "regeneration stop required" and the process proceeds to step 3F. When the result of step 3A is "regenerative braking possible", the process proceeds to step 41 in FIG.

At step 3F, a command to stop regenerative braking is output to the motor ECU, and the routine proceeds to the next step 3G. At this time, a differential pressure (ΔPr) is generated between the pipe 61 and the pipe 63 by the relief valve 6 and the relief valve 56
This causes a pressure difference (ΔPr) between the pipe 62 and the pipe 64.

In step 3G, the bypass valves 53 and 7
And wait until the differential pressure disappears, then wait for the next step 3H
Proceed to. Here, since the regenerative braking force is lost, 8 msec in the map of FIG.
The hydraulic pressure is increased at a constant control time duty ratio with the steepest slope of c open and 30 msec closed. That is, as shown in FIG. 9, the bypass valve 53 is opened and closed within a short time period, and the operation is repeated. On the other hand, in step 48 of FIG. 4 described later, the increase in the hydraulic pressure of the pipes 63 and 64 is controlled in accordance with the rotation deceleration.

In step 41 of FIG.
A and FB are cleared to 0, information on the master cylinder pressure Pm detected by the pressure sensor 11 is input, and information on the wheel cylinder pressure Pw detected by the pressure sensor 12 is input. Further, a differential pressure ΔP between Pm and Pw is calculated, and a predetermined function f
The calculation is performed by substituting the differential pressure ΔP as a parameter in (), and the result of the calculation is defined as the regenerative braking amount M. Then, the regenerative braking amount M and the regenerative braking command are given to the motor ECU 27,
Perform regenerative braking.

In the next step 42, first, the running speed Vo of the vehicle body is detected based on the current rotational speed of the electric motor 2, and then the wheel speed of the front wheels is determined by referring to the output of the wheel speed sensor 57. Vw, and based on Vo and Vw,
The slip ratio S of the front wheels is calculated. S = (Vo−Vw) /
Vo.

In step 43, the slip ratio S obtained in step 42 is compared with a threshold value Sref. Sref> S
In this case, the process returns to step 32 in FIG. Otherwise, proceed to step 45.

At step 45, 1 is set to the flag FB. In the next step 46, the rotational speed deceleration G is obtained by differentiating the front wheel speed with reference to the signal output from the wheel speed sensor 57. In the following step 47, the bypass valve 53
The pressure increase characteristic when increasing the oil pressure of the rear wheel cylinder is determined by the above control. Specifically, an open time and a close time are selected based on the rotation deceleration G obtained in step 46 using a control time map (see FIG. 9) stored in advance in the memory. For example, when the deceleration G is smaller than the threshold value α, the open time is set to 3 msec, and the close time is set to 80 ms.
ec (opening / closing cycle is 83 msec). When the deceleration G is smaller than the threshold value β, the opening time is set to 8 msec,
The closing time is 30 msec (opening / closing cycle is 38 msec) (α
<Β). That is, the duty ratio of the opening time to the opening / closing cycle becomes larger when the rotation deceleration G (absolute value) is larger than when it is small.

In step 48, after the bypass valve 53 is opened for the opening time obtained in step 47, the bypass valve 53 is closed for the closing time obtained in step 47. This opening and closing operation is repeated. In the next step 49, the master cylinder pressure Pm detected by the pressure sensor 11 is input, and in the following step 4A, the wheel cylinder pressure Pwr on the rear wheel side is obtained by estimation. In step 4B, the master cylinder pressure Pm
And the wheel cylinder pressure Pwr of the rear wheel. If they do not match, the process returns to step 48 to repeat the above-mentioned processing. If they match, the process returns to step 32 in FIG.

A process for estimating the wheel cylinder pressure Pwr on the rear wheel will be described. Step 4 of FIG.
FIG. 11 shows the processing of the portions 8, 49, 4A and 4B in more detail. Further, there is generally a correlation between the wheel cylinder pressure Pw and the flow rate C as shown in FIG. Based on these characteristics, C is obtained from Pw or Pw is obtained from C. However, since the characteristics vary from device to device, the results measured in advance are registered as a table in the memory of the computer. Yes, use the contents of this table.

In order to estimate the wheel cylinder pressure Pwr at any time during opening and closing of the bypass valve 53, first, an initial value Pwheel of the wheel cylinder pressure is obtained. Lily
Assuming that the pressure difference between the two ends of the valve when it opens is Pth (in this example, 20 kg / cm ² ), when the opening and closing of the bypass valve 53 is started, if the master cylinder pressure Pm is greater than Pth, the relief valve will In the open state, the wheel cylinder pressure becomes Pm-Pth. If Pm is equal to or lower than Pth, the relief valve is closed and the wheel cylinder pressure is zero.

Therefore, when N = 0, step 105
To 106 to compare Pm and Pth and find that Pm> P
If th, Pm−Pth is set to the initial value Pwo in step 107
If Pm ≦ Pth, the initial value Pw
Set o to 0.

In step 109, the flow rate C0 at that time is obtained from the initial value Pwo of the wheel cylinder pressure with reference to the contents of the table storing the relationship of FIG. This flow rate C0 is defined as Cx. The change in the flow rate of the oil flowing through the wheel cylinder is expressed by the following equation.

[0066]

(Equation 1)

Then, the flow rate Cx at an arbitrary time point is obtained by sequentially calculating this equation, and from this flow rate Cx,
The wheel cylinder pressure Pwr is obtained based on the table showing the relationship shown in FIG. In practice, C in step 10C
After obtaining Pwr from x, the next time at step 10A, Cx
Is stored in Cp, and Pwr is stored in Pp. In step 10B, Cp is set to the previous flow rate value, Pp is regarded as the latest wheel cylinder pressure, and the square root of (Pm-Pp) is multiplied by a coefficient β. The current flow rate Cx is obtained by adding the integral value to Cp. From the flow rate Cx, Pwr is determined in the next step 10C based on the table.

FIG. 5 shows the relationship between the master cylinder (M / C) pressure and the wheel cylinder (W / C) pressure of the rear wheels during braking in this embodiment, and shows the relationship between the vehicle speed and the wheel speed. 6, the distribution of the braking force on the front wheel (Fr) side and the braking force on the rear wheel (Rr) side is shown in FIG. 7, and the relationship between the master cylinder pressure and the braking force is shown in FIG.

First, a description will be given with reference to FIG. In this embodiment, when the slip ratio S is small, the braking force distribution line
The characteristic B2 is shifted considerably downward from the ideal braking force distribution line B1. That is, in a region where the braking force of the front wheel is smaller than Ba, the hydraulic brake force is 0 for both the front and rear wheels because the bypass valve 7 for the front wheel and the bypass valve 53 for the rear wheel are closed. Only braking force occurs.

In a region where the braking force of the front wheels is larger than Ba, the wheel cylinders 5 of the front wheels are passed through the relief valve 6.
(Fr), and hydraulic pressure is applied to the wheel cylinder 5 (Rr) of the rear wheel via the relief valve 56, so that the front wheel is driven by both the regenerative brake and the hydraulic brake. In addition, a braking force is generated on the rear wheels by hydraulic braking.
The broken line of the braking force distribution line B2 is due to the effect of the proportioning valve 23.

When the slip ratio S is large, the braking force distribution line has a characteristic B3 closer to the ideal braking force distribution line B1. That is, since the bypass valve 53 of the rear wheel opens, the piping 6
2 becomes equal to the oil pressure of the pipe 64, and the oil pressure of the wheel cylinder 5 (Rr) of the rear wheel is increased as compared with the normal case, so that the braking force increases and the braking force distribution line rises. Shift to By bringing the braking force distribution line closer to the ideal braking force distribution line B1, more effective braking is performed, and the vehicle can be stopped at the shortest distance.

When the braking force is distributed in accordance with the braking force distribution line B2, the ratio of the use of the regenerative braking is higher than that of the hydraulic braking, so that the energy can be efficiently recovered by the regenerative braking. However, in that case, the front wheels are more likely to lock than the rear wheels during braking. When the front wheels are locked, the braking force of the front wheels does not increase any more. Therefore, it is necessary to increase the braking force of the rear wheels in order to increase the braking force of the entire vehicle. Therefore, in this embodiment, when the front wheels are locked, the distribution of the braking force is switched from the braking force distribution line B2 to the braking force distribution line B3. For example, in FIG. 7, A on the braking force distribution line B2
In this case, by opening the bypass valve 53, the braking force on the rear wheel side increases, and the braking force on the braking force distribution line B3 is increased.
Move to the point. As a result, the braking force acts on both the front and rear wheels,
The braking force of the total increases.

However, if the braking force distribution line B2 is switched from the braking force distribution line B2 to the braking force distribution line B3 at once, inconveniences such as sudden depression of the brake pedal, generation of a violent sound, generation of a G shock, and unstable behavior of the vehicle are caused. Occurs. In order to solve such a problem, in this embodiment, when the braking mode is switched from the braking force distribution line B2 to the braking force distribution line B3, the bypass valve 53 is switched in the same manner as in the case of failure in regenerative braking. By repeating the opening / closing operation in a short time, the change in hydraulic pressure is moderated (step 48). In this case, the bypass valve 5
The opening time and closing time of No. 3 are determined based on the detected deceleration G of the front wheel speed and the map shown in FIG. 9 (step 47).

As shown in FIG. 6, when the deceleration of the wheel speed is small, the wheel locks (the wheel speed becomes 0).
The time until the wheel is locked is short when the deceleration of the wheel speed is large. In the former case, even if the oil pressure is changed over a relatively long time, it takes time for the wheels to lock. This is effective for avoiding inconveniences such as sinking, generation of an intense oil noise, occurrence of a G shock, and unstable behavior of the vehicle. However, in the latter case, if the change in the oil pressure is too slow, the braking force when the wheels are locked may be insufficient, and the braking may be delayed.

According to the detected deceleration G (absolute value) of the front wheel speed, the hydraulic pressure is changed over a long time when G is small, and the hydraulic pressure is changed in a relatively short time when G is large. No braking delay and no brake
Inconveniences such as sudden depression of the key pedal, generation of an intense oil noise, occurrence of a G shock, and unstable behavior of the vehicle can be minimized.

In the above embodiment, the rotation deceleration of the wheel is obtained, and the duty ratio of opening and closing the bypass valve is changed according to the magnitude of the rotation deceleration. Detect the locked state of the wheel,
The duty ratio of opening and closing the bypass valve may be changed according to the locked state of the wheels. For example, the hydraulic pressure may be changed promptly when the lock of the wheel occurs or at the stage when the lock is likely to occur. Alternatively, the slip state of the wheel may be detected instead of the rotation deceleration of the wheel, and the duty ratio of opening and closing the bypass valve may be changed according to the slip state of the wheel. For example, when the slip amount of the wheel is large, the oil pressure may be changed quickly.
Further, the brake pedal force may be detected instead of the rotation deceleration of the wheel, and the hydraulic pressure may be quickly changed when the brake pedal force is large or the rate of change of the brake pedal force is high. .

FIG. 12 shows the configuration of one modified embodiment.
In this embodiment, linear valves 81 and 82 are used instead of the relief valve of the above embodiment. The degree of opening of these linear valves 81 and 82 changes in proportion to the amount of current. In this example, the valve is fully opened when the current is 0, and the opening decreases as the current increases. In this embodiment, FIG.
The amount of current supplied to the linear valve is controlled as shown in FIG. That is, when performing the regenerative braking, the differential pressure (Pm−Pw) at both ends of the linear valve is controlled so as to be constant and Pw ≧ 0. And gradually increase the opening over time. As a result, the same effect as in the above embodiment can be obtained.

FIG. 15 shows a modification of the control shown in FIG.
In FIG. 15, the same processes as those in FIG. 3 are denoted by the same step numbers. Referring to FIG. 15, processing corresponding to step 3F in FIG. 3 is performed in steps 3J, 3K, and 3L.
Has been changed to The changed process will be described below.

In step 3J, a regeneration operation stop mode is determined. In this embodiment, four modes A, B, C and D are provided as the regenerative operation stop modes. The conditions for mode determination are as follows.

A. Mode D, b1 if the motor or inverter is out of order. Modes A and b2 when the motor and inverter voltages are in the first abnormal range. Modes B and b3 when the motor and inverter voltages are in the second abnormal range. When the voltages of the motor and the inverter are in the third abnormal range, the modes C and c1. Mode A, c2 when the motor and inverter currents are in the first abnormal range. Mode B, c3 when the motor and inverter currents are in the second abnormal range. When the currents of the motor and the inverter are in the third abnormal range, the modes C and d1. Mode A, d2. When the motor and inverter temperatures are in the first abnormal range. Mode B, d3. When the motor and inverter temperatures are in the second abnormal range. Modes C and e1 when the motor and inverter temperatures are in the third abnormal range. Mode A, e2. When the rotation speed of the motor is in the first abnormal range. Mode B, e3. When the motor speed is in the second abnormal range. When the rotation speed of the motor is in the third abnormal range, mode C, f1. Mode A, f2. When the battery voltage is in the first abnormal range. Mode B, f3. When the battery voltage is in the second abnormal range. Mode C, g1. When battery voltage is in the third abnormal range. Mode A, g2, when the battery current is in the first abnormal range. Mode B, g3 when the battery current is in the second abnormal range. Mode C, h1. When the battery current is in the third abnormal range. Mode A, h2. When the depth of discharge of the battery is in the first abnormal range. Mode B, h3. When the depth of discharge of the battery is in the second abnormal range. Mode C, i1 when the depth of discharge of the battery is in the third abnormal range. Mode A, i2 when the battery temperature is in the first abnormal range. Mode B, i.3 when battery temperature is in second abnormal range. Mode C when the temperature of the battery is in the third abnormal range; and j. Mode D when the shift position of the transmission is in reverse or neutral.

At step 3K, the motor ECU 27 is instructed to stop the regenerative braking operation. Actually, the code of the current mode (any of the above A to D) indicating the regenerative operation stop mode is sent from the brake ECU 26 to the motor ECU 27. In that case, the motor EC
U27 reduces the regenerative braking force little by little at a predetermined decreasing speed according to the received code (see FIG. 16).
Actually, as shown in a map shown in FIG. 14, each mode is associated with a decreasing speed (dM / dt) of the regenerative braking force, and the dM / dt is the most at the time of the mode A. Small, mo
At time D, the regenerative braking force immediately becomes 0 (the decreasing speed is the fastest).

In step 3L, the bypass valve opening / closing time (opening time, closing time, opening / closing cycle) corresponding to the regenerative operation stop mode (any of the above A to D) determined in step 3J.
Is read from a map (see FIG. 14) held in advance on the brake ECU 26 and determined. Then, in the next step 3G, the opening and closing of the bypass valve 53 and the opening and closing of the bypass valve 7 are repeated according to the bypass valve opening / closing time determined in step 3L until Pm = Pw.

The increasing speed of the hydraulic braking force changes in accordance with the opening / closing time of the bypass valves 53 and 7. FIG.
As is clear from the map shown in FIG. 4, in this example, the decreasing speed (dM / dt) of the regenerative braking force and the bypass valves 53 and 7
Therefore, there is a correlation between the decreasing speed of the regenerative braking force (dM / dt) and the increasing speed of the hydraulic braking force. Actually, as shown in FIG. 16, the decrease in the regenerative braking force always coincides with the increase in the hydraulic braking force, and even when the regenerative operation is stopped, the total braking force (the regenerative braking force + The dM / dt is related to the increasing speed of the hydraulic braking force so that the hydraulic braking force does not fluctuate.

In the above embodiment, the actual regenerative braking force decrease speed (dM / dt) coincides with the regenerative braking force decrease speed previously associated with the regenerative operation stop mode selected at that time. Motor EC
If U27 cannot precisely control the regenerative braking force, the error between the decrease in the regenerative braking force and the increase in the hydraulic braking force may increase. In such a case, for example, the regenerative current value and the voltage value are measured using a sensor or the like, the actual regenerative braking force is obtained by calculation, and the hydraulic braking force is increased so as to compensate for the change in the obtained regenerative braking force. The speed (opening / closing time of the bypass valves 53 and 7) may be determined.

[0085]

As described above, according to the present invention, the switching of the valve means from the restricted state to the open state in accordance with the detected braking state, for example, the rotation deceleration of the wheel.
Since the speed is automatically changed, favorable braking according to the driving situation can be realized. For example, when the braking force of the front wheel is more greatly distributed than the rear wheel, the front wheel is more likely to lock than the rear wheel, but when the front wheel locks, the braking force does not increase any more, so in such a case, It is necessary to release the restriction on the valve means and increase the braking force on the rear wheels.
When the rotational deceleration of the wheel is large, the front wheel locks quickly, so by increasing the braking force of the rear wheel in a short time, it is possible to quickly compensate for the lack of braking force and avoid a delay in braking. In addition, when the rotation deceleration of the wheel is small, there is enough time before the front wheel is locked, so that opening / closing of the on / off valve means is avoided in order to avoid inconvenience due to a sudden increase in pressure of the hydraulic braking means. It is desirable to reduce the duty ratio or the inclination of the change in the opening of the linear valve to increase the braking force of the rear wheels over time. That is, there is no braking delay, no generation of heavy oil noise, and no unstable vehicle behavior.

According to the second aspect, when slippage of the driving wheel is detected, the opening and closing operation of the valve means of the driven wheel is repeated according to the duty ratio determined according to the rotation deceleration of the driving wheel. Since the braking force of the hydraulic braking system of the driving wheel can be increased to bring the braking force distribution closer to the ideal braking force distribution line, it is possible to minimize the braking distance.

According to the third aspect of the present invention, since the drive wheels connecting the electric drive means are the front wheels (FR) and the rear wheels (RR) are the driven wheels, if the braking force distribution is determined as shown by a solid line in FIG. As a result, the kinetic energy of the vehicle is consumed at a higher rate by the front wheels that are the driving wheels than at the rear wheels that are the driven wheels, and the energy can be recovered with high efficiency by regenerative braking of the driving wheels.

According to the fourth aspect, when the valve means is switched from the restricted state to the open state, the transition speed of the switching is determined according to the degree of decrease in the regenerative braking force, so that the hydraulic braking force increases. The curve is determined in accordance with the degree of decrease in the regenerative braking force, so that the hydraulic braking force is increased so as to compensate for the decrease in the regenerative braking force, and fluctuations in the braking force can be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating main parts of a drive system and a brake system of an electric vehicle according to an embodiment.

FIG. 2 is a block diagram showing a main part configuration of a motor ECU of FIG. 1;

FIG. 3 is a flowchart showing the operation of the brake ECU shown in FIG. 1;

FIG. 4 is a flowchart showing the operation of the brake ECU shown in FIG. 1;

FIG. 5 is a time chart showing an example of a change in oil pressure of the apparatus of FIG. 1;

FIG. 6 is a time chart showing changes in the speed of a vehicle wheel and a vehicle body during braking.

FIG. 7 is a graph showing the distribution of braking force between front wheels and rear wheels.

FIG. 8 is a graph showing a relationship between a master cylinder oil pressure and a braking force.

FIG. 9 is a map showing a part of a memory content on the brake ECU of FIG. 1;

FIG. 10 is a graph showing a relationship between a W / C pressure and a flow rate.

FIG. 11 is a flowchart showing details of a part of FIG. 4;

FIG. 12 is a block diagram illustrating a configuration of a modified example.

FIG. 13 is a time chart showing the operation of the apparatus of FIG.

FIG. 14 shows data on a memory used in the embodiment of FIG.
6 is a map showing a part of the data.

FIG. 15 is a flowchart showing the operation of a brake ECU according to one modified embodiment.

FIG. 16 is a time chart showing a change in braking force.

[Explanation of symbols]

1: Battery 2: Electric motor 4: Master cylinder (M / C) 5 (Fr), 5 (Rr): Wheel cylinder (W / C) 6, 56: Relief valve 7, 52, 53 : Bypass valve 11, 12: Pressure sensor 21: Brake pedal 22: Brake switch 23: Proportioning valve 25: Transmission 26: Brake EC
U 27: Motor ECU 28: Potentiometer 29, 54: Check valve 51, 55: Initial pressure cut valve 57, 58: Wheel speed sensor 61, 62, 63,
64: Piping 81, 82: Linear valve Fr: Front wheel Rr: Rear wheel D1 to D6: Diode

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiyuki Sakai 2-1-1 Asahicho, Kariya City, Aichi Prefecture Aisin Seiki Co., Ltd. Examiner Nozomu Nagama (56) References JP-A-5-161209 (JP) JP-A-6-153313 (JP, A) JP-A-6-153316 (JP, A) JP-A-7-336806 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) B60L 7/24 B60L 7/14

Claims (4)

(57) [Claims] An on-vehicle battery for storing electric energy; an electric drive means for driving wheels by electric power from the on-vehicle battery; and an electric power generated by the electric drive means with rotation of the wheels. Regenerative braking means; hydraulic pressure generating means for generating a hydraulic pressure in accordance with the operation amount of a brake pedal; hydraulic braking means for applying a braking force to wheels according to the hydraulic pressure generated by the hydraulic pressure generating means; Valve means for restricting the transmission of hydraulic pressure from the hydraulic pressure generating means to the hydraulic braking means; and a braking device for an electric vehicle, wherein when a predetermined condition is satisfied, the restriction of the valve means is released. And supplying the hydraulic pressure of the hydraulic pressure generating means to the hydraulic braking means: a braking state detecting means for detecting a braking state of a wheel; and the valve means is switched from a restricted state to an open state satisfying the predetermined condition. Sometimes, the migration rate of switching, the braking state detecting means for determining in accordance with the braking state of the wheel has been detected, the switching control means; characterized in that a braking device for an electric vehicle. 2. The switching control means according to claim 1, wherein when the driving wheel slips, the switching control means determines the duty according to the rotation deceleration of the driving wheel.
The braking device for an electric vehicle according to claim 1, wherein the opening / closing operation of the valve means of the driven wheel is repeated according to the tee ratio. 3. The braking device for an electric vehicle according to claim 2, wherein the driving wheels connecting the electric driving means are front wheels, and the rear wheels are driven wheels. 4. The switching control means, when the predetermined condition is satisfied and the valve means is switched from a restricted state to an open state, determines a transition speed of switching according to a degree of reduction of regenerative braking power. The braking device for an electric vehicle according to claim 1.