JP2001039281A - Vehicular braking system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid unstable behavior of vehicles having regenerative braking means and frictional braking means, by ensuring gripping force. SOLUTION: Required braking force is set in accordance with the operation of a brake pedal. Maximal regenerative praking force Grm is computed from the current vehicle speed and corrected depending on the running states. A correction value K1 is set in S22, which is a smaller value from 0 to 1 as the steering angle gets larger. A second correction value K2 is calculated in S23, which is a smaller value from 0 to 1 as the coefficient of friction μ of the road surface gets smaller. The maximal regenerative braking force Grm is corrected with both correction values K1 and K2 in S24. Regenerative braking is effected with the maximal regenerative braking force Grm, and frictional braking is effected with the required braking force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle braking device provided with both regenerative braking means and friction braking means.

[0002]

2. Description of the Related Art In electric vehicles and hybrid cars, regenerative braking is generally performed in which the driving energy is converted into electric energy during deceleration and a braking force is obtained by the resistance at that time. In JP-A-10-264793, when the required braking force set according to the operation state of the brake pedal is small, only the regenerative braking is performed.
When the braking force is insufficient with only the regenerative braking force, a method has been proposed in which friction braking that generates a friction braking force on the vehicle is also performed.

In Japanese Patent Application Laid-Open No. Hei 10-229608, braking is performed by both regenerative braking and frictional braking during sudden braking.

[0004]

However, in the above-mentioned conventional braking system for a vehicle, regenerative braking is mainly performed from the viewpoint of improvement of energy efficiency such as improvement of fuel efficiency, and the insufficient braking force is compensated by friction braking. It is configured.
Therefore, there are the following inconveniences, for example.

[0005] That is, for example, the grip force of the tire of the steered wheel that is being steered such as during a turn is high for steering and low for braking. In such a case, if the vehicle is configured so that regenerative braking is performed on the steered wheels, the regenerative braking is mainly used to apply a braking force to the steered wheels. It is not possible to obtain a necessary grip force and unstable behavior such as side slip may occur.

Further, for example, when the coefficient of friction (μ) of the road surface is small, the friction circle becomes small, so that the grip force of the tire becomes small. For this reason, the regenerative braking is not limited to a vehicle configured to perform the regenerative braking on the steered wheels, but may be a vehicle in which regenerative braking is provided on a power transmission path for a specific wheel such as a front wheel or a rear wheel. When the braking is performed mainly with the braking, there is a possibility that a sufficient grip force of the tire is not secured and the behavior becomes unstable.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a vehicle equipped with both regenerative braking means and friction braking means, which secures a gripping force and is unstable. Is to avoid undesired behavior.

[0008]

In order to achieve the above-mentioned object, the present inventor does not always perform regenerative braking as the main braking, but performs regenerative braking at the required total braking force according to the running state. The present invention has been completed by paying attention to changing the ratio between friction braking and friction braking.

More specifically, the present invention provides a regenerative braking means interposed on a power transmission path for a wheel to generate regenerative braking force, and a friction for generating a frictional braking force to the wheel. Braking means, running state detecting means for detecting a value relating to the grip force of the tire, and a regenerative braking means and a friction brake for determining a required braking force required for braking the vehicle so that the required braking force is achieved. And braking control means for controlling the means. The braking control means may control the braking so that the smaller the grip force of the tire used for braking based on the detection result of the traveling state detection means, the lower the regenerative braking ratio in the required braking force becomes. Controlling the means is a particular matter.

Here, the "required braking force" is provided with, for example, a brake operation detecting means for detecting a value relating to the operation of the brake pedal, for example, the amount of depression of the brake pedal, and is determined based on the detection result of this detecting means. What should I do? Also, for example, an obstacle detection means for detecting an obstacle in front of the own vehicle and the own vehicle is provided, and based on a distance between the own vehicle and the obstacle and a relative speed between the own vehicle and the obstacle, or based on the own vehicle. The required braking force may be determined based on only the distance between the vehicle and the obstacle ahead.

In this case, the gripping force of the tire used for braking is secured by lowering the ratio of regenerative braking and increasing the ratio of frictional braking in accordance with the running condition, leading to unstable behavior. Is avoided.

The running state in which the regenerative braking ratio is to be changed, that is, the state in which the grip force of the tire used for braking is small is, for example, when a vehicle in which regenerative braking is performed on at least the steered wheels is turned. Can be
As described above, at the time of turning, the ratio of the grip force of the steered wheels used for steering is high, and the grip force of the tire used for braking is small. At this time,
If a braking force is applied to the steered wheels mainly by regenerative braking, it is not possible to secure a grip force necessary for braking and steering, which may lead to unstable behavior.

Therefore, the regenerative braking means is interposed at least on the power transmission path for the steered wheels, and the traveling state detecting means detects the steering angle or the steering speed. The braking control means may control the regenerative braking means and the friction braking means such that the larger the steering angle or the steering speed, the smaller the ratio of the regenerative braking in the required braking force. Here, the "regenerative braking means" may be provided not only on the steered wheels but also on the power transmission paths of all the wheels, for example.

[0014] In this case, when the ratio used for steering in the grip force of the tire of the steered wheel increases, such as when the steering angle or the steering speed is large, the regenerative braking ratio is reduced and the friction braking ratio is reduced. , The grip force used for braking with the tires of the wheels other than the steered wheels is sufficiently ensured. As a result, a grip force necessary for both braking and steering is ensured, and unstable behavior such as sideslip is avoided.

According to a third aspect of the present invention, as in the second aspect of the invention, in a vehicle in which regenerative braking is performed on at least the steered wheels, regenerative braking means for not only turning but also a required braking force is provided. The present invention relates to control with friction braking means, and specifically, regenerative braking means is interposed at least on a power transmission path for a steered wheel, and running state detection means detects a steering angle or a steering speed to perform braking. The control means performs only the regenerative braking when the required braking force is smaller than the predetermined braking force, and performs both the regenerative braking and the friction braking when the required braking force is equal to or more than the predetermined braking force. The braking means and the friction braking means are controlled. Then, the predetermined braking force is set to be smaller as the ratio of the grip force of the steered wheels used for turning is larger based on the steering angle or the steering speed.

Here, the "braking control means", for example, first determines the maximum regenerative braking force (maximum regenerative braking force) obtained by regenerative braking according to the vehicle speed, and this maximum regenerative braking force is determined by the required braking force. When the maximum regenerative braking force is smaller than the required braking force, the regenerative braking unit and the friction braking unit are controlled so as to perform both the regenerative braking and the friction braking. You may do so. The maximum regenerative braking force may be corrected to be smaller based on the steering angle or the steering speed as the ratio of the grip force of the steered wheels used for steering is increased. That is, the “predetermined braking force” in the third aspect of the present invention may be controlled as the maximum regenerative braking force determined according to the vehicle speed and corrected according to the turning state.

Further, the braking control means inhibits the regenerative braking and performs only the friction braking when the ratio used for steering in the grip force of the steered wheels is larger than a predetermined value. Alternatively, both braking means may be controlled. Here, “when the ratio used for turning is larger than a predetermined value” may be, for example, when the steering angle is larger than a predetermined value.

In this case, when the vehicle is not turning, braking is performed mainly by regenerative braking so that power is actively generated, and braking force that is not sufficient with the regenerative braking force alone is compensated by friction braking. . In the case of a turn, the ratio used for steering increases in the grip force of the steered wheels, and the ratio used for braking decreases,
By increasing the rate of friction braking, unstable behavior is avoided. Furthermore, when there is a high possibility that the unstable behavior such that the ratio used for steering in the grip force is larger than a predetermined value is high, regenerative braking is prohibited, and only friction braking is performed. The above-mentioned unstable behavior is avoided by ensuring the grip force used for steering while ensuring the grip force used for braking by the tires of the wheels other than the steering wheel.

As described above, by controlling the braking means in which the ratio between the regenerative braking and the friction braking is changed in accordance with the traveling state, both the improvement of the energy efficiency of the vehicle and the stable traveling can be achieved.

The invention according to claim 5 focuses on the steering angle or the steering speed as the traveling state.
Unlike the invention according to claim 4, the invention focuses on the friction coefficient of the road surface. Specifically, the traveling state detecting means detects the friction coefficient of the road surface, and the braking control means uses the friction coefficient. Is smaller, the regenerative braking means and the friction braking means are controlled such that the ratio of the regenerative braking in the required braking force becomes smaller.

Here, the "running state detecting means" includes:
For example, what is called road-to-vehicle communication information may be input from the infrastructure such as information that the road surface is wet and the friction coefficient of the road surface is small.

When the coefficient of friction of the road surface is small, the friction circle becomes small, and the grip force used for braking becomes small. Therefore, the grip force required for braking is ensured by reducing the regenerative braking ratio and sufficiently performing friction braking.

In this case, the regenerative braking means may be provided on a power transmission path for the steered wheels, or may be provided for other wheels.

[0024]

As described above, according to the vehicle braking device of the present invention, it is possible to secure the grip force of the tire and avoid unstable behavior.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. <First Embodiment> FIG. 1 shows a drive system of a hybrid car according to a first embodiment of the present invention, wherein 1 is a traveling drive engine, and 2 is a traveling drive motor (electric motor) as regenerative braking means. ). The engine 1 is an internal combustion engine and is a multi-cylinder engine.

The output (generated torque) of the engine 1 is input to an automatic transmission 5 that is composed of a torque converter 3, an electromagnetic clutch 4, and a multi-stage transmission gear mechanism and has four forward stages and one reverse stage. It has become. The output from the automatic transmission 5 is transmitted to differential gears 10 for left and right front wheels 9FL and 9FR as driving wheels and steering wheels via gears 6, 7, and 8 as interlocking mechanisms. ing.

On the other hand, the output of the motor 2 is transmitted to the gear 6 via gears 11 and 12 as an interlocking mechanism, and finally transmitted to the left and right front wheels 9FL and 9FR. The motor 2 is provided with a battery (including a capacitor and a capacitor) 13 as a voltage source, and the battery is charged by a generator 14 as an electric motor mechanically driven by the engine 1. It has become.

An electromagnetic clutch is incorporated in the interlocking mechanism 15 between the engine 1 and the generator 14, so that the connection between the engine 1 and the generator 14 can be appropriately disconnected. The generator 14 is also used as a starter for the engine 1. The generator 14 is used as a starter for the engine 1 in order to quickly start the engine 1, compared with a generator mounted on a normal automobile. Although it is sufficiently large, it is sufficiently small as compared with the traveling drive motor 12.

FIG. 2 shows a brake (friction braking) circuit. In FIG. 2, reference numeral 21 denotes a master cylinder as a first hydraulic pressure generating source for generating a brake hydraulic pressure in accordance with the operation amount of a brake pedal 22. is there.

A pump 23 as a second hydraulic pressure source is provided separately from the master cylinder 21. The pump 23 has two pumps 24, 2
4 and one motor 25 for driving each pump 24. Each of the pumps 24 is connected to the master cylinder 2
The brake fluid is sucked from one reservoir tank 21a via a check valve 26, and the high-pressure brake fluid is discharged to an accumulator 28 via a check valve 27.
The brake fluid stored in the accumulator 28 is supplied to the reservoir 30 after being adjusted to a desired pressure by the linear solenoid valve LSV. Excess brake fluid discharged from each pump 24 is supplied to the reservoir tank 2 via a check valve 29.
1a.

Reference numerals 31FL to 31RR denote braking devices provided on each wheel, that is, friction braking devices for performing braking by frictional force, all of which are disk brakes. And 31FL is a brake device for the left front wheel, 3
1FR is a brake device for the right front wheel, 31RL is a brake device for the left rear wheel, and 31RR is a brake device for the right rear wheel. And, each of the brake devices 31FL to 31RR
The ABS (Antilock Brake System) control circuit 32
The brake fluid pressure is supplied via the.
That is, the ABS control circuit 23 includes the first and second
Are provided, and the first connection portion 33, 34 is provided.
An MCV composed of an electromagnetic on-off valve is
1 and the brake fluid from the reservoir 30 via the VLV1 composed of an electromagnetic on-off valve are selectively supplied. Similarly, the brake fluid from the master cylinder 21 via the MCV2 composed of an electromagnetic on-off valve and the brake fluid from the reservoir 30 via the VLV2 composed of an electromagnetic on-off valve are connected to the second connection portion 34. And the liquid is selectively supplied. Also, the ABS circuit 23
Are supply valves 35FL to 35RR and discharge valves 36FL, each of which is an electromagnetic on-off valve for each of the brake devices 31FL to 31RR.
To 36 RR.

Then, each brake device 3 under ABS control is controlled.
The supply of the brake fluid to 1FL to 31RL is as follows. That is, the supply valve 35F
The brake fluid is supplied to the left front wheel brake device 31FL via L, while the brake fluid is supplied to the right rear wheel brake device 31RR via the supply valve 35RR. Similarly, from the connection portion 34, the supply valve 35FR
, The brake fluid is supplied to the right front wheel brake device 31FR, and the brake fluid is supplied to the left rear wheel brake device 31RL via the supply valve 35RL. On the other hand, each brake device 3 during ABS control
The discharge of brake fluid from 1FL to 31RL is performed by the discharge valve 3
The processing is performed independently through 6FL to 36RR. Note that, in FIG.
RR is a check valve provided in each brake device so as to bypass the supply valves 35FL to 35RR and for quickly discharging the brake fluid.

In the brake passage from the master cylinder 21 to the on-off valve MCV1, a brake stroke sensor 38 as a brake operation detecting means for detecting an operation amount of the brake pedal 22 is displaced according to the pressure of the brake fluid. Is provided.

Note that, in FIG.
It is a pressure sensor.

FIG. 3 shows a control system, and 4 is a CPU constituted by using a microcomputer. The CPU 4 serves as a braking control unit that performs driving control for traveling using the engine 1 and the motor 2 and also performs braking control.

The CPU 4 receives signals from various sensors or switches (detection means) in addition to the signal from the stroke sensor 38. Specifically, 51 is a brake switch that is turned on when the brake pedal 22 is depressed,
52 is a wheel speed sensor that detects the vehicle speed, 53 is an accumulator sensor that detects the accumulated pressure of the accumulator 28,
54 is an accelerator operation amount sensor that detects an operation amount of an accelerator pedal, 56 is a steering angle sensor that detects a steering angle, and 57 is road surface information (road-vehicle distance) that detects a friction coefficient (μ) of a road surface using infrastructure information or the like. Communication information).

The CPU 4 outputs control signals to the various valves MCV1 to VLV2, LSV and the motor 2 described above.

Next, of the control contents of the CPU 4, the braking control will be described with reference to the flowchart of FIG. 4 or FIG.

Incidentally, in the first embodiment, the friction braking force is usually applied to the pump device 2 as a second hydraulic pressure generating source.
The brake fluid pressure from the master cylinder 22 as the first fluid pressure source is used in an emergency.

First, in step S11, it is determined whether or not the brake switch has been turned on. If NO, in step S12 each brake device 31FL
Valves MCV1 and MCV2 are opened so that .about.31RR can communicate with the master cylinder 21, and the on-off valves VLV1 and VL
V2 is closed. On the other hand, in step S11, Y
In the case of ES, the process proceeds to step S13.

In step S13, it is determined whether there is an abnormality in the brake fluid pressure sensor or the like. If the determination is YES, the process proceeds to step S12. on the other hand,
If the determination is NO, the process proceeds to step S14, where the on-off valves MCV1 and MCV2 are closed. That is, the use of the generated brake fluid pressure in the master cylinder 21 is prohibited.

In step S15, the vehicle speed detected by the wheel speed sensor 52 and the brake operation amount detected by the brake stroke sensor 38 are input.

Next, at step S16, a required braking force Gt is obtained based on the brake operation amount. The required braking force Gt may be set to a larger value as the brake operation amount increases, and such a required braking force Gt may be set using a map.

Thereafter, in step S17, it is determined whether or not the accelerator pedal is depressed. If NO, the process proceeds to step S19, while if YES, the required braking force Gt is set to Gt in step S18.
+ Α → Gt is set. Here, α is a positive value, and the required braking force Gt is set to a large value. This is because the driver may be in a panic state because the accelerator pedal is depressed during braking, and in such a case, the required braking force Gt is increased to ensure safety. In addition, as will be described later, the proportion of friction braking is increased to ensure braking responsiveness. Then, the process proceeds to step S19.

In step S19, the maximum regenerative braking force Grm obtained by the motor 2 is determined from the vehicle speed. The maximum regenerative braking force Grm may be determined based on, for example, a map shown in FIG. In this map, the horizontal axis represents the vehicle speed, that is, the rotational speed rpm of the wheels.
The vertical axis is the regenerative torque kg · m, and the higher the vehicle speed, the lower the regenerative torque, that is, the lower the maximum regenerative braking force Grm.

Then, the process proceeds to step S21 shown in FIG. 6 to correct the maximum regenerative braking force Grm (see FIG. 4 or FIG. 6A).

In step S21, it is determined whether the steering angle is equal to or larger than a predetermined value. In this case, it is determined that the vehicle is turning when the steering angle is equal to or larger than a predetermined value. In the case of YES, the process proceeds to step S22, while in the case of NO, the process proceeds to step S110 shown in FIG. 4 without correcting the maximum regenerative braking force Grm (FIG. 4).
Or see FIG. 5B).

In step S22, a first correction value K1 for correcting the maximum regenerative braking force is calculated according to the turning state. The first correction value K1 is a value from 0 to 1. When the steering angle is small, K1 = 1, and as the steering angle increases, K1 approaches 0. Then, when the steering angle is equal to or more than the predetermined steering angle, K1 is set to 0 and regenerative braking is prohibited. The determination of the first correction value K1 may be performed using a map. Since the required grip force increases as the vehicle speed increases, the first correction value K1 may be decreased as the vehicle speed increases. further,
Since the change in grip force increases as the steering angular speed increases, the first correction value K1 may decrease as the steering angular speed increases.

As described above, when the ratio used for steering in the grip force of the left and right front wheels 9FL and 9FR becomes high, such as when the steering angle is large, the first correction value K1 can be reduced to reduce the request control. The ratio of the regenerative braking force in the power Gt decreases. As a result, a grip force necessary for braking and steering is ensured, and unstable behavior such as sideslip can be avoided.

Then, in step S23, according to the road surface friction coefficient μ input from the road surface information 57,
The second correction value K2 is calculated. The second correction value K2 is a value of 0 to 1. For example, as the value of the road surface friction coefficient is smaller, the second correction value K2 may be set closer to 0. The calculation may be performed using a map.

As described above, when the friction coefficient (μ) of the road surface is small, it is difficult to secure the grip force of the tire used for braking because the friction circle is small. Therefore, when μ on the road surface is small, the second
By reducing the correction value K2, the regenerative braking ratio is reduced and the friction braking ratio is increased, so that a necessary grip force can be secured.

In step S24, the maximum regenerative braking force G is calculated using the first and second correction values K1 and K2.
rm is corrected. That is, Grm × K1 × K2 → Grm. Then, the process proceeds to step S110 (see FIG. 4 or FIG. 6B).

In step S110, it is determined whether the required braking force Gt is smaller than the maximum regenerative braking force Grm. The case of NO is when all of the required braking force Gt can be covered by the regenerative braking force Grm. At this time, in step S111, the regenerative braking gain Grg (Gr) is set so that the regenerative braking force satisfies the required braking force Gt.
g <0) is determined. That is, the value obtained by multiplying the gain Grg by the maximum regenerative braking force Grm is the required deceleration Gt.
The gain Grg is determined so that

Then, in step S112, the regenerative braking force of the motor 2 is changed to the maximum regenerative braking force Gr by the gain Grg.
It is executed with the value multiplied by m.

Next, in step S113, the control of the linear solenoid valve LSV is turned off and the VLV valve is closed so that the hydraulic braking force, that is, the friction braking force, becomes zero. Thereby, the supply brake fluid pressure based on the linear solenoid valve LSV is set to zero.

On the other hand, in step S110, YE
In the case of S, the required deceleration Gt cannot be realized only by the regenerative braking force. In this case, control is performed to satisfy the required deceleration Gt by using the friction braking force. That is, in step S114, the regenerative braking gain Grg is set based on the brake pedal operation speed. The brake pedal operation speed is determined by differentiating the brake operation amount detected by the sensor 38. Further, the gain Grg may be a value of 0 to 1. Such a gain Grg may be set using a map. For example, when the operation speed of the brake pedal is lower than a predetermined value, it is determined that sudden braking is not requested, Grg is set to 1, and the brake pedal operation is performed. When the speed is a predetermined value, Grg is set to 0.9, and when the speed exceeds the predetermined value, the value is set to a small value as the operation speed is large, indicating that the degree of sudden braking is large, and the friction braking with good response is high. What is necessary is just to make it perform at a ratio.

In step S115, a value obtained by subtracting a value obtained by multiplying the regenerative braking gain Grg by the maximum regenerative braking force Grm (regenerative braking force) from the required braking force Gt is a hydraulic braking force, that is, a friction braking force Gtu. Is set as

Thereafter, in step S116, Gr
Control for realizing a regenerative braking force of a value obtained by multiplying g by Grm is performed. In step S117, control of the linear solenoid valve LSV and control for opening the VLV valve are performed so as to realize the friction braking force of the value of Gtu. Done.

As described above, the required braking force G is obtained only by the regenerative braking.
When t can be satisfied, only regenerative braking is performed. When regenerative braking alone cannot provide the required braking force Gt, regenerative braking is usually performed mainly by regenerative braking so that the insufficient braking force is compensated for by friction braking. , Energy efficiency can be improved.

On the other hand, when the regenerative braking for the left and right front wheels (steering wheels) is mainly performed, such as when turning or when the coefficient of friction of the road surface is small, it is necessary to secure a grip force enough to be used for braking and steering. If it is difficult, the ratio of the regenerative braking force Grm at the required deceleration Gt is reduced, so that the friction braking is sufficiently performed on the left and right rear wheels. As a result, it is possible to secure a grip force used for braking and steering. <Second Embodiment> The second embodiment of the present invention is different from the first embodiment in that when the automatic braking is performed to avoid danger, the required braking force is related to the driving environment, particularly to the obstacle in front. Is determined. More specifically, the required braking force Gt is determined based on the distance to the front obstacle and the relative speed to the front obstacle.

FIG. 7 shows a control system according to the second embodiment of the present invention. There are two points different from the first embodiment. One point is that the brake stroke sensor 38 for detecting the amount of depression of the brake pedal is not provided. Another point is that an obstacle detection radar 58 for detecting an obstacle in front of the own vehicle is provided, and the obstacle detection sensor 58 may be, for example, a laser radar, a millimeter wave radar, or an ultrasonic radar. Good.

Since the other components of the control system, and the configurations of the drive system and the braking circuit are the same as those of the first embodiment, the same members are denoted by the same reference numerals and the description thereof will be omitted. I do.

Next, the CP according to the second embodiment of the present invention will be described.
The braking control by U4 will be described with reference to the flowchart shown in FIG.

First, steps S31 to S in FIG.
34 is the same as step S11 to step S14 in FIG. 4, but step S31 in FIG.
11, when the driver operates the brake pedal (in the case of YES), the process proceeds to step S32 in order to use the brake fluid pressure from the master cylinder 22 as the first fluid pressure source, and proceeds to step S32. Open valve and VL
The V valve is closed.

In step S35, traveling environment information such as the vehicle speed, the distance to the obstacle based on the detection result of the obstacle detection radar 58, and the relative speed are input. The relative speed with respect to the obstacle may be obtained, for example, by differentiating the distance to the obstacle ahead.

Next, in step S36, a required braking force Gt is obtained based on the traveling environment information. The required braking force Gt is determined based on, for example, a relative speed and a distance to an obstacle. That is, the required braking force Gt increases as the relative speed increases and the distance decreases.

Thereafter, steps S37 and S3
8 is performed, which is performed in step S in FIG.
This is the same as 17 and step S18. Further, in the processing after step S38, the processing after step S18 in FIG. 4 is performed.
4 is different from step S114 only.

That is, in step S314,
The gain Grg of the regenerative braking is determined based on the required braking force Gt. The gain Grg may be set to a value of 0 to 1, for example, as the required deceleration Gt increases, the gain Gr
What is necessary is just to determine so that g may be made small. This may be determined using, for example, a map. In this way, as the required braking force Gt for the automatic braking set for avoiding the danger with the obstacle in front of the vehicle is larger, it is assumed that the required degree of the rapid braking is higher, and the ratio of the regenerative braking is reduced. The gain Grg is reduced. <Third Embodiment> A third embodiment of the present invention employs a method similar to the method in the second embodiment described above, based on a traveling environment (distance and relative speed with respect to a forward obstacle).
Is determined, and the second temporary required braking force Gtm is determined based on the brake pedal operation amount by the same method as the method in the first embodiment.

The gain Grg of the regenerative braking is determined according to the operation speed of the brake pedal. When the first temporary required braking force Gta is larger than a predetermined value, it is determined that the urgency is high. The gain Grg is forcibly set to 0 irrespective of the brake pedal operation speed so that regenerative braking is not performed.

FIG. 9 shows a control system according to a third embodiment of the present invention. The difference from the first embodiment is that an obstacle detection radar 58 for detecting an obstacle in front of the own vehicle is provided. Is additionally provided.

The remaining structure of the control system, and the structures of the drive system and the braking circuit are the same as those of the first embodiment. Therefore, the same members are denoted by the same reference numerals and description thereof will be omitted. .

Next, the CP according to the third embodiment of the present invention will be described.
10A or 10B regarding the braking control by U4.
This will be described according to the flowchart shown in FIG.

First, in step S41, a traveling environment such as a distance to a forward obstacle and a brake pedal operation amount are detected. Then, in step S42, the first provisional required deceleration Gta for compensating for the braking force that is insufficient for the deceleration due to the resistance of the engine 1 and the automatic transmission 5 is determined based on the traveling environment.

In step S43, it is determined whether or not the first provisional request deceleration Gta is greater than zero. That is, it is determined whether or not the automatic braking based on the traveling environment is required. If the determination in step S43 is NO, step S4
Proceeding to 6, it is determined whether the brake switch is on. If the determination in step S46 is NO, the process proceeds to step S48.

Step S48 corresponds to step S12 in FIG. Step S4
If YES in the determination of 3 or YES in the determination of step S46, it is determined in step S44 whether or not the pressure sensor is abnormal. If the determination in step S44 is YES, step S4
Proceed to 8.

If the determination in step S44 is NO, in step S45, the on-off valves MCV1, MCV2
Is closed, in step S47, the second provisional required braking force Gtm is determined based on the brake pedal operation amount.

Thereafter, in step S49, it is determined whether the first required braking force Gta is larger than a predetermined value. If the determination in step S49 is YES, the emergency flag is set to 1 in step S410, and N
In the case of O, the emergency flag is reset to 0 in step S411.

Step S410 or step S410
After 411, in step S412, the larger of the two provisional required braking forces Gta and Gtm is determined as the final required braking force Gt.

After step S 412, the processes after step S 19 in FIG. 4 are performed. However, as described above, in the process of step S114 in FIG. 4, the gain Grg of the regenerative braking is basically determined based on the brake operation speed. However, in step S419 shown in FIG. At this time, the gain Grg is set to 0 regardless of the brake operation speed. As a result, only friction braking is performed in an emergency, so that braking responsiveness can be ensured. <Other Embodiments> Note that the present invention is not limited to the above-described embodiments, but includes various other embodiments. That is, the required deceleration Gt can be determined by various methods, and may be determined based on, for example, only the distance from the obstacle ahead.

The motor 2 for performing the regenerative braking is not limited to the motor for traveling, but may be a large generator, for example, which transmits traveling energy to the generator via an engine. Further, the present invention may be applied to a so-called electric vehicle in which the traveling drive is performed only by the motor 2 without the engine 1.

Further, when the accelerator is operated during braking, the regenerative braking ratio may be set to be small. For example, when the gain Grg determined in step S111 of FIG. 4 is being operated by an accelerator, correction may be made to reduce the gain by a predetermined ratio.

In addition, the drive wheels may be rear wheels or all wheels.

Furthermore, in the above embodiment, the maximum regenerative braking force is corrected based on both the turning time and the road surface μ. However, the present invention is not limited to this. The correction of the maximum regenerative braking force may be performed based on either of them.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an example of a power train according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a brake system for friction braking.

FIG. 3 is a block diagram illustrating an example of a control system according to the first embodiment.

FIG. 4 is a flowchart illustrating a control example according to the first embodiment.

FIG. 5 is a diagram showing a map of a maximum regenerative braking force obtained according to a vehicle speed.

FIG. 6 is a flowchart for correcting a maximum regenerative braking force.

FIG. 7 is a diagram corresponding to FIG. 3, illustrating an example of a control system according to a second embodiment.

FIG. 8 is a flowchart illustrating a control example according to the second embodiment.

FIG. 9 is a diagram corresponding to FIG. 3, illustrating an example of a control system according to a third embodiment.

FIG. 10A is a part of a flowchart illustrating a control example according to the third embodiment;

FIG. 10B is a part of a flowchart showing a control example according to the third embodiment.

[Explanation of symbols]

2 Motor (regenerative braking means) 4 CPU (braking control means) 38 Brake stroke sensor 56 Steering angle sensor (running state detecting means) 57 Road surface information (running state detecting means) 58 Obstacle detection radar 9FL, 9FR Front wheel (steering wheel) 31FL-31RR brake device (friction braking means)

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Claims (5)

[Claims] 1. A regenerative braking means interposed on a power transmission path for a wheel to generate a regenerative braking force; a friction braking means to generate a friction braking force on the wheel; A driving state detecting means, and a braking control means for determining a required braking force required for braking the vehicle and controlling the regenerative braking means and the friction braking means so as to achieve the required braking force. The control unit controls the two braking units based on the detection result of the traveling state detection unit such that the smaller the grip force of the tire used for braking is, the lower the regenerative braking ratio in the required braking force becomes. A braking device for a vehicle, comprising: 2. The regenerative braking device according to claim 1, wherein the regenerative braking device is interposed at least on a power transmission path for a steered wheel, the traveling state detecting device detects a steering angle or a steering speed, and the braking control device includes the steering control device. A braking device for a vehicle, wherein the regenerative braking means and the friction braking means are controlled such that the larger the angle or the steering speed, the smaller the ratio of the regenerative braking in the required braking force. 3. The regenerative braking means according to claim 1, wherein the regenerative braking means is provided at least on a power transmission path for the steered wheels, the running state detecting means detects a steering angle or a steering speed, and the braking control means comprises a demand control means. When the power is smaller than the predetermined braking force, only the regenerative braking is performed, while when the required braking force is equal to or more than the predetermined braking force, both the regenerative braking and the friction braking are performed. And the predetermined braking force is set to be smaller as the ratio of the grip force of the steered wheels used for turning is larger based on the steering angle or the steering speed. 4. The braking control means according to claim 3, wherein the braking control means inhibits regenerative braking and performs only frictional braking when a ratio used for steering in the grip force of the steered wheels is larger than a predetermined value. A vehicle braking device for controlling a braking means. 5. The running state detecting means according to claim 1, wherein the running state detecting means detects a friction coefficient of the road surface, and the braking control means determines that the smaller the friction coefficient is, the more the regenerative braking ratio in the required braking force is. A braking device for a vehicle, wherein a regenerative braking unit and a friction braking unit are controlled so as to be small.