JP2002096721A - Brake device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric drum brake, eliminating a difference between service braking forces during advance and during reverse and a difference between parking braking forces during parking at a downward slope and during parking at an upward slope. SOLUTION: A pair of brake shoes 202a, 202b are enlarged by the driving force of an electric motor 41 and brake linings 219a, 219b are pushed against a drum 206 being integrally rotated with a wheel to grant braking force to the wheel. A microcomputer 100 discriminates the advance and reverse of the vehicle in accordance with a vehicle speed detected by a speed sensor 51 to make a current flow in the electric motor 41 during reverse larger than a current flow in the electric motor 41 during advance when a brake pedal 11 is operated at the same depression force. The current in the motor during parking brake at a downward slope detected by a slope sensor 52 is differentiated from that during parking braking at an upward slope detected thereby.

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 an electric drum brake for applying a braking force to wheels by the driving force of an electric motor.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Unexamined Patent Application Publication No.
As disclosed in Japanese Patent Application Publication No. 4 (JP-A) No. 4 (1994), a vehicle braking device provided with an electric drum brake is known. In this electric drum brake, a motor current corresponding to a driver's brake operation is supplied to the electric motor, and a pair of arc-shaped brake shoes facing each other are expanded with the anchor as a fulcrum by the driving force of the motor. Thus, the brake lining fixed to each pair of brake shoes is pressed against a drum that rotates integrally with the wheel to apply a braking force to the wheel.

[0003]

However, in the above-mentioned conventional electric drum brake, that is, a drum type brake, the surface pressure of the brake lining and the drum during braking of the wheels during forward and backward movement of the vehicle is reduced. The high part is different. Specifically, in the case of a duo-servo type (DS type) drum brake, the surface pressure of the portions X1 and X2 in FIG. 9A is high during forward movement, and the portions Y1 and Y2 in FIG. Surface pressure is high. In addition, leading trailing type (L
In the case of the drum brake of (T type), FIG.
The surface pressure in the portion X3 of FIG.
Area pressure is high.

[0004] On the other hand, the friction coefficient between the brake lining and the drum is small at first, and has a property of increasing as it is used until a certain limit time is reached. Since the frequency of stopping the vehicle moving forward is extremely higher than the frequency of stopping the vehicle moving backward, the portions X1 to X3 of the high surface pressure mainly used for braking the wheels when the vehicle moves forward are used. The friction coefficient between the brake lining and the drum is higher than the friction coefficient between the brake lining and the drum of the high surface pressure portions Y1 to Y3 mainly used for braking the wheels when the vehicle moves backward. Become. Therefore, in the electric drum brake, if the current flowing to the electric motor is the same, the braking force for braking the rotation of the wheel in the direction in which the vehicle moves backward is the braking force for braking the rotation of the wheel in the direction in which the vehicle moves forward. Will be smaller than This means that when the driver performs the same brake operation and passes a motor current corresponding to the operation to the electric motor, a difference occurs in the braking force on the vehicle when the vehicle moves forward and when the vehicle moves backward. means.

[0005] In addition, even when the driver operates the parking brake operator to stop the vehicle on a slope, in the case of forward and backward travel in terms of braking the rotation of the wheels that are going to travel in one direction. In this case as well, there is a difference in the braking force on the vehicle when the vehicle is on an uphill slope and when the vehicle is on a downhill slope. Note that a downhill refers to a slope where the road surface becomes lower toward the front of the vehicle, and an uphill slope refers to a slope where the road surface becomes higher toward the front of the vehicle. For these reasons, according to the above-described conventional apparatus, the driver feels a sense of discomfort and is not preferable in controlling the braking force.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to improve a braking device for a vehicle provided with an electric drum brake. An object of the present invention is to prevent the state from being different depending on various situations such as a running state, a road state, and an environmental state.

In order to achieve the above object, a feature of the present invention is to determine whether the vehicle is moving forward or reverse, and to determine the motor current when the vehicle is moving backward, and to determine whether the vehicle is moving forward. This is to make the motor current larger than a certain motor current. According to this, it is possible to correct such that the difference in the braking force between when the vehicle is moving forward and when the vehicle is moving backward due to the partial difference in the friction coefficient between the brake lining and the drum is eliminated or reduced.

Another feature of the present invention is that it is determined whether the vehicle is stopped on an uphill or a downhill, and the motor current when the vehicle is stopped on an uphill is determined by the vehicle. This is to make it larger than the motor current when the vehicle is stopped on a downhill. According to this, the difference in the braking force caused by the partial difference in the friction coefficient between the brake lining and the drum between when the vehicle is stopped on an uphill and when the vehicle is stopped on a downhill is eliminated or reduced. Can be modified to

Another feature of the present invention resides in that a road surface condition where the vehicle is located is detected, and a current flowing through the electric motor is controlled and corrected in accordance with the detected road condition.
In this case, as the road surface condition, a condition such as a road surface friction coefficient, a bad road or a good road may be detected. According to this, even if the traveling state of the vehicle or the state of the stopped road surface changes, it can be corrected so as to eliminate or reduce the difference in the braking force due to the brake operation.

Another feature of the present invention resides in that the environmental temperature of the electric brake is detected, and the current flowing through the electric motor is corrected and controlled according to the detected environmental temperature.
In this case, as the environmental temperature, the outside air temperature, the temperature of the electric brake, or the like may be detected. According to this, even if the environmental temperature of the electric brake changes, the correction can be made so as to eliminate or reduce the difference in the braking force due to the brake operation.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a vehicle braking device according to an embodiment of the present invention.
Schematically shows the entire braking device of the vehicle.

The braking device of this vehicle includes a service brake pedal device 10, a parking brake operator 20, electric disc brakes 30, 30 provided on front wheels FL, FR, and electric drums provided on rear wheels RL, RR, respectively. The vehicle includes brakes 40 and 40 and an electric control device 50.

The service brake pedal device 10 has a brake pedal 11 as a brake operation member which is depressed by a driver. Brake pedal 11
Are assembled to the stroke simulator 12. The stroke simulator 12 includes the brake pedal 1
1, a moving member 12a, a guide member 12b for guiding the moving member 12a, and a spring 12c as an elastic member accommodated in the guiding member 12b and expanded and contracted by the movement of the moving member 12a to increase or decrease the elastic force.
Consists of The spring 12c keeps the brake pedal 11 at a predetermined position when the driver does not step on the brake pedal.

The brake pedal 11 and the stroke simulator 12 are also assembled with a brake pedal switch 13 and an operating force sensor 14, which constitute a part of the electric control device 50. The brake pedal switch 13
It is off when the brake pedal 11 is not depressed, and is turned on when depressed. The operation force sensor 14 detects a depression operation force F of the brake pedal 11. The depressing operation force F is
The operation force sensor 14 is equal to the force resisting the elastic force of the spring 12c and equal to the stepping amount (stepping stroke), and the operation force sensor 14 can be constituted by a stroke sensor that detects the stepping amount of the brake pedal 11.

The parking brake operator 20 is provided in the passenger compartment near the driver's seat and is manually operated by the driver. The parking brake operator 20 is a two-position switch type switch for instructing activation and release of the parking brake. ing. The parking brake operator 20 constitutes an operating member for operating a parking brake device.

The electric disc brakes 30, 30 include electric motors 31, 31, brake pads 32, 32, and discs 33, 33 which rotate integrally with the front wheels FL, FR, respectively. The brake pads 32, 32 are driven by the electric motors 31, 31, and the discs 33, 33
To apply a braking force to the front wheels FL, FR by a frictional force with the disks 33, 33. In the present embodiment, the electric motors 31 are constituted by DC motors, but other motors such as AC motors and ultrasonic motors may be employed.

The electric drum brakes 40, 40 are each constituted by a duo-servo type drum brake as shown in FIG. Each of the electric drum brakes 40 includes a substantially disk-shaped backing plate 200, a pair of substantially arc-shaped brake shoes 202a and 202b provided on the backing plate 200, and a friction surface 204 on an inner peripheral surface. It includes a rotating drum 206 and an electric actuator 207 for expanding one ends of a pair of shoes 202a and 202b. Backing plate 20
Reference numeral 0 is non-rotatably attached to a vehicle body side member (not shown).

A pair of brake shoes 202a, 202b
Are engaged with anchor pins 208 fixed to the backing plate 200 at one end portions facing each other, and thus are rotatably held in a state where they are prevented from rotating with the drum 206. The other ends are connected by struts 210. The force acting on one shoe is transmitted to the other shoe by the strut 210. Note that the pair of brake shoes 202a, 202b can be moved along the surface of the backing plate 200 by the shoe hold-down devices 212a, 212b.

A pair of brake shoes 202a, 202b
As shown in the figure, the other ends are biased toward each other by a spring 214, and one end is biased toward the anchor pin 208 by each of the shoe return springs 215a and 215b. Also, a strut 216 and a return spring 218 are provided at one end.
Is also provided.

A brake lining 219a, 219b as a frictional engagement member is held on the outer peripheral surface of each brake shoe 202a, 202b, and the pair of brake linings 219a, 219b are
The frictional force is generated between the brake linings 219 a and 219 b and the drum 206 by frictionally engaging the inner peripheral surface 204 of the drum 206. In the present embodiment, the strut 210 is provided with an adjusting mechanism, and the brake linings 219a and 219b and the drum inner peripheral surface 20 are changed according to wear of the brake linings 219a and 219b.
Adjust the gap with 4.

Each of the brake shoes 202a and 202b is
Rim 224a, 224b and web 222a, 2 respectively
22b, one end of a lever 230a is attached to a pin 232 on a web 222a of one brake shoe 202a.
It is provided to be rotatable via a. Lever 230a
Notches are provided in portions of the web and the webs 222a and 222b that face each other.
The strut 216 is provided with both ends engaged with the lever 230a and the webs 222a and 222b.

An electric actuator 207 including the electric motor 41 is connected to the other end of the lever 230a. More specifically, the electric actuator 207 includes a speed reducer and a motion conversion mechanism in addition to the electric motor 41. The rotation of the output shaft of the electric motor 41 is reduced by the speed reducer, and the rotational motion is converted into linear motion by the ball screw mechanism, and the other end of the lever 230a is connected to the output member of the ball screw mechanism. . Then, the lever 230a is rotated by the driving of the electric motor 41 (electric actuator 207), and the strut 216 causes the pair of brake shoes 202a and 202b to expand. Note that, in the present embodiment, the electric motor 41 is configured by a DC motor, but another motor such as an AC motor or an ultrasonic motor may be employed.

The electric control unit 50 includes a vehicle speed sensor 51 and an inclination sensor 52 in addition to the brake pedal switch 13 and the operation force sensor 14. Vehicle speed sensor 51
The vehicle speed V is detected by measuring the rotation of the output shaft of the transmission. The vehicle speed V is represented by a positive value when traveling forward, and a negative value when traveling backward. The inclination sensor 52 detects the vehicle body inclination angle θ in the front-rear direction.
That is, the inclination angle θ of the road surface on which the vehicle is located in the vehicle longitudinal direction.
Is to be detected. The switch 13 and the sensors 14, 51, 52 are connected to the parking brake operator 20.
Are connected to the controller 53.

The controller 53 is mainly composed of a microcomputer 100 including a CPU, a ROM and a RAM. The microcomputer 100 repeatedly executes a program (not shown) every predetermined short time to execute the electric disc brakes 30, 3 for the front wheels FL, FR.
In addition to controlling the action of
Are repeatedly executed to control the operation of the electric drum brakes 40, 40 for the rear wheels RL, RR. In addition,
The ROM of the microcomputer 100 includes, in addition to the program of FIG.
Various control values of the characteristics shown in FIG. 6 are also stored in the form of a table or the like.

A driver 55 connected to a battery 54 is connected to the output side of the controller 53. The driver 55 is controlled by the controller 50 (microcomputer 100), and supplies a current of a magnitude specified by the microcomputer 100 from the battery 54 to the electric motors 31, 41. In the present embodiment, a command signal indicating the duty ratio is output to the driver 55,
Electric currents are supplied to the electric motors 31 and 41 in accordance with the duty ratio.

The operation of the embodiment configured as described above will be described. In a state where the brake pedal 11 is not depressed and the parking brake operation element 20 does not request the parking brake to be actuated, the microcomputer 100 executes a front wheel program (not shown) to execute an electric disc brake for the front wheels FL and FR. 30,3
A signal representing a duty ratio “0” for controlling 0 is output to the driver 55. Thereby, the driver 55
The electric current from the battery 54 is supplied to the electric disc brake 30,
Since the electric motors 31, 31 do not operate without being supplied to the electric motors 31, 31, the brakes 30, 30 do not apply a braking force to the front wheels FL, FR in this case.

The microcomputer 100 repeatedly executes the rear wheel program shown in FIG. 3 every predetermined short time in parallel with the front wheel program (not shown). The execution of this program is started in step S10, and in step S12, the brake pedal switch 13
And whether the brake pedal 11 is being depressed is determined based on the signal. In this case, since the brake pedal 11 has not been depressed as described above, "NO" is determined in the step S12, and the parking brake operator 2 is determined in the step S14.
A signal from 0 is input, and it is determined whether or not a parking brake activation request has been made by the operator 20. Also in this case, since the parking brake operation request has not been made by the parking brake operator 20 as described above, "NO" is determined in the step S14, and the electric drum brakes for the rear wheels RL and RR are determined in a step S32. The duty ratio DR for controlling 40, 40 is set to "0", and the program proceeds to step S34.

In step S34, a control signal representing the duty ratio DR set to "0" is output to the driver 55. As a result, the driver 55 does not supply the electric current from the battery 54 to the electric motors 41 of the electric drum brakes 40,
In this case, the brakes 40, 40 do not apply a braking force to the rear wheels RL, RR. After the processing in step S34, the execution of this program is temporarily terminated in step S36.

Next, a case where the brake pedal 11 is depressed will be described. Also in this case, the front wheel program (not shown) is executed and the operation force sensor 14
Is a control signal indicating a duty ratio corresponding to a target current value corresponding to the operating force F detected by the front wheels FL,
A control signal for controlling the FR electric disc brakes 30, 30 is output from the controller 53 to the driver 55. The driver 55 supplies a current having a magnitude corresponding to the control signal from the battery 54 to the electric disc brake 3.
It flows to the 0, 30 electric motors 31, 31. Therefore,
The electric disc brakes 30, 30 apply a braking force corresponding to the operation force F to the front wheels FL, FR. However, since the control of the braking force on the front wheels FL and FR is not directly related to the present invention, a detailed description is omitted.

On the other hand, in the program for the rear wheels in FIG. 3, it is determined in step S12 described above that "YES", that is, the brake pedal 11 is depressed, and the program proceeds to step S16. Step S
In step 16, the detected vehicle speed V is input from the vehicle speed sensor 51, and it is determined whether the vehicle is moving forward or stopped based on the detected vehicle speed V. In the present embodiment, the vehicle speed V represents forward by a positive value and represents reverse by a negative value. Therefore, if the vehicle speed V is “0” or positive, it is determined that the vehicle is moving forward or stopped, and the vehicle speed V becomes If negative, it is determined that the vehicle is moving backward.

If the vehicle is moving forward or stopped, "YES" is determined in step S16, and the detected operating force F is input from the operating force sensor 14 in step S18, and the detected operating force F The determined target pressure P * is determined. In determining the target pressing force P *, the operating force-pressing force characteristic shown by the solid line in FIG. Is determined, and the pressure P1a is set as the target pressure P *. The pressing force P1a increases as the operating force F increases.

If the vehicle is traveling in reverse, step S
At 16, “NO” is determined, and at step S 20, the detected operating force F is input from the operating force sensor 14, and the target pressing force P * corresponding to the detected operating force F is determined. In determining the target pressing force P *, the pressing force corresponding to the detected operating force F while obeying the operating force-pressure characteristic shown by the broken line in FIG. P2a is determined, and the same pressure P2a is set as the target pressure P *. The pressing force P2a also increases as the operating force F increases, but is set to a value larger than the pressing force P1a for the same operating force F.

After the processing in step S18 or step S20, in step S28, the microcomputer 1
Referring to a target pressing force-target current table provided in the ROM of FIG. 00 and having the characteristics shown in FIG.
Convert to *. Next, in step S30, the program is provided in the ROM of the
The target current I * thus determined is converted into a duty ratio DR according to the characteristic with reference to a target current-duty ratio table having the characteristic shown in FIG. Note that the target current I * and the duty ratio DR are the target pressure P * and the target current I
It increases with each increase in *.

After the processing in step S30, step S
At 34, a control signal indicating the duty ratio DR is output to the driver 55 as in the case described above, and the process proceeds to step S3.
At 6, the execution of this program is temporarily terminated. The driver 55 allows a current having a magnitude corresponding to the duty ratio DR to flow from the battery 54 to the electric motors 41 of the electric drum brakes 40 based on the duty ratio DR.

Thus, each electric motor 41 starts operating and generates a driving force substantially proportional to the magnitude of the current. That is, the depressing operation force F of the brake pedal 11
(Or a target force P * and a target current I *). By the operation of the electric motor 41, the electric actuator 207 rotates the lever 230a with a force corresponding to the driving force. Strut 216
As a result, the pair of shoes 202 a and 202 b are expanded, and the brake linings 219 a and 219 b (friction engagement members) are pressed against the inner peripheral surface 204 of the drum 206. The friction engagement member is frictionally engaged with the drum inner peripheral surface 204, and a frictional force is generated therebetween. As a result, the rear wheels RL, RR receive the operating force F (or the target pressing force P
* And the target current I *).

In this case, the twisting force based on the frictional force generated in one shoe 202b and the driving force by the electric actuator 207 are applied to the strut 21 from the other end.
0 to the other end of the other shoe 202a. The other shoe 202a is pressed against the drum inner peripheral surface 204 by the sum of the twisting force and the expanding force, and a larger friction force is generated than the one shoe 202b. Thus, the output of one shoe 202b is
2a, and a double servo effect can be obtained.
In, a large braking torque can be obtained.

Next, the difference between the operation of the electric drum brake 40 of the duo-servo type operating as described above when the vehicle is moving forward and when it is moving backward will be described. FIG. 9 (A) (B)
FIG. 4 is a schematic diagram of the electric drum brake 40 for explaining the operation of the electric drum brake 40 when the vehicle is moving forward and when moving backward.

When the vehicle is traveling forward, the surface pressure between the brake linings 219a and 219b and the drum 206 increases at a position before the anchor pin 208 and the strut 210 in the rotation direction of the drum (wheel). Therefore, when the vehicle is moving forward, X1, X1 in FIG.
The surface pressure at the portion X2 is higher than the surface pressure at the other portions, and when the vehicle is moving backward, the surface pressure at the portions Y1 and Y2 in FIG. 9B becomes higher than the surface pressure at the other portions.

On the other hand, brake linings 219a, 219
The coefficient of friction between 9b and drum 206 is initially small,
Until a certain limit time is reached, it has the property of becoming larger as it is used. Since the frequency of stopping the vehicle moving forward is much higher than the frequency of stopping the vehicle moving backward, the portions X1 and X2 of the high surface pressure mainly used for braking the wheels when the vehicle advances are used. The coefficient of friction between the brake linings 219a and 219b and the drum 206 is such that the brake linings 219a and 219b and the drum 206 of the high surface pressure portions Y1 and Y2 mainly used for braking the wheels when the vehicle is moving backward. Is higher than the coefficient of friction. Therefore, the electric motors 41, 41
If the current flowing through the vehicle is the same, the braking force for braking the rotation of the rear wheels RL and RR in the direction in which the vehicle moves backward is smaller than the braking force for braking the rotation of the rear wheels RL and RR in the direction in which the vehicle moves forward. Will also be smaller.

However, as described above, according to the present embodiment, the target pressing force P * (=) at the time when the vehicle is moving backward is obtained for the same depressing operation force F of the brake pedal 11 by the processing of steps S16 to S20. P1b) is set to a larger value than the target pressure P * (= P1a) when the vehicle is moving forward or stopped. Thus, for the same depressing operation force F, the current flowing through the electric motors 41, 41 when the vehicle is moving backward is larger than when the vehicle is moving forward, and the driving force by the motors 41 is increased. Is controlled.

As a result, the difference in the braking force on the rear wheels RL, RR due to the difference in the friction coefficient between the brake linings 219a, 219b and the drum 206 when the vehicle moves forward and when the vehicle moves backward is corrected, and the same operating force is applied. The vehicle can be braked with substantially the same braking force with respect to F. Therefore, the control of the electric drum brakes 40, 40 when the vehicle is moving forward and when the vehicle is moving backward is appropriate, and the driver does not feel uncomfortable.

Next, a case will be described in which the parking brake operator 20 is operated by the driver while the vehicle is stopped and a request for the parking brake is made. In this case, “YES” is determined in step S14 of FIG. 3, and the program proceeds to step S22. Step S22
, The inclination angle θ of the road surface detected by the inclination sensor 52 is input, and it is determined whether the vehicle is stopped on a flat road or a downhill based on the detected inclination angle θ. In addition, the downhill refers to a slope where the road surface becomes lower toward the front of the vehicle.

If the vehicle is stopped on a flat road or a downhill, "YES" is determined in the step S22, and in a step S24, the target pressure P * is set to a predetermined value P2a.
(See FIG. 4). If the vehicle is stopping on an uphill, it is determined "NO" in step S22, and in step S26, the target pressure P * is set to a predetermined value P2b (see FIG. 4). In addition, the uphill refers to a slope where the road surface becomes higher toward the front of the vehicle.

After the processing in step S24 or step S26, the processing in steps S28 to S34 is executed, and a current having a magnitude corresponding to the target pressure P * is supplied to the electric motors 41. Thereby, the electric motor 4
1, 41 generate a driving force of a magnitude corresponding to the target pressure P *, and generate brake linings 219a, 219b.
Is pressed against the drum 206 by the driving force.

Even when the parking brake is applied to the vehicle as described above, if the vehicle is stopped on a downhill, the forward movement of the vehicle is prohibited. In addition, the surface pressure at the portions X1 and X2 in FIG. 9A becomes higher than the surface pressure at the other portions. Also, when the vehicle is stopped on an uphill, the vehicle is prohibited from moving backward, and therefore, as in the case of the vehicle moving backward, the Y1 and Y2 portions in FIG. The surface pressure becomes higher than the surface pressure of other parts.

However, according to the present embodiment, the target pressure P * (= P2b) when the vehicle is stopped on an uphill is obtained by the processes of steps S22 to S26.
The value is set to a value larger than the target pressure P * (= P2a) when the vehicle is stopped on a downhill or a flat road.
Therefore, when the vehicle is stopped on an uphill, the current flowing through the electric motors 41 is larger than when the vehicle is stopped on a downhill or a flat road. Driving force is greatly controlled.

As a result, the brake linings 219a and 219b and the drum 206 when the vehicle is stopped on an uphill and when the vehicle is stopped on a downhill.
The difference in the braking force applied to the rear wheels RL and RR due to the difference in the friction coefficient between the vehicle and the vehicle is corrected, so that the vehicle can always be braked with substantially the same braking force. Therefore, the control of the electric drum brakes 40 and 40 when the vehicle is stopped on the uphill and when the vehicle is stopped on the downhill is appropriate, and the driver does not feel uncomfortable.

Next, the electric motors 41, 41 are set according to the road surface condition where the vehicle is located and the environment where the electric brake is placed.
A modification of the above-described embodiment in which the driving force is corrected will be described. ,

In this modification, the electronic control unit 50
1 also includes a road surface friction coefficient sensor 56 and a temperature sensor 57 connected to the controller 53, as shown by the broken lines in FIG. The road surface friction coefficient sensor 56 detects a friction coefficient μ between the tire and the road surface. As the road surface friction coefficient sensor 56, a sensor that detects a tire slip state or the like can be used. However, information such as weather information and traffic information is obtained from the outside, and road surface conditions (freezing road, wet road, Various methods such as a method of estimating from a dry road can be adopted. The temperature sensor 57 detects the outside air temperature Tp. Further, the temperature sensor 57 may be a sensor that is assembled to the electric drum brakes 40 and 40 and detects the temperatures of the brakes 40 and 40 instead of the outside air temperature Tp.

In this modified example, the microcomputer 100 is a program for the rear wheels as shown in FIG.
Steps S18, S20, S24, S2 of the program
The program added with the processing of steps S40 to S48 shown in FIG. 7 between the processing of step S6 and the processing of step S28 is repeatedly executed at predetermined short intervals.

The microcomputer 100 inputs the road friction coefficient μ from the road friction coefficient sensor 56 in step S40 after the processing in steps S10 to 26 described above, and in step S42, the road friction built in the computer 100 With reference to the coefficient table, a correction coefficient K1 corresponding to the road friction coefficient μ is determined. As shown in FIG. 8A, the correction coefficient K1 decreases as the road surface friction coefficient μ increases.

After the processing in step S42, step S
At 44, the detected temperature Tp is input from the temperature sensor 57, and at step S46, a correction coefficient K2 corresponding to the detected temperature Tp is determined with reference to a temperature table built in the computer 100. The correction coefficient K2 increases as the temperature Tp increases, as shown in FIG.

Next, at step S48, the target pressurizing force P * set by the processing at steps S18, S20, S24 and S26 is multiplied by the correction coefficients K1 and K2 to obtain the corrected target pressurizing force P * ( = K1, K2, P *). Then, the processes of steps S28, S30, and S34 using the corrected target pressing force P * are executed, and
The current flowing through the electric motors 41 is controlled. As a result, according to this modification, the brake linings 219a and 219b by the electric motors 41 and 41 are
6 is corrected according to the correction coefficients K1 and K2.

According to this correction, the pressing force by the electric motors 41, 41 is corrected to decrease as the road surface friction coefficient μ increases. This is because a larger braking force is required as the road surface friction coefficient μ decreases, and the correction eliminates the difference in the braking force due to the braking operation even when the vehicle travels or the condition of the stopped road surface changes. Can be modified to be smaller.

It should be noted that increasing the braking force when the road surface friction coefficient μ becomes small as described above may cause the tire to slip. When this slip occurs, the tire is controlled by an anti-lock control (not shown). Slip is avoided.

According to the correction, the pressing force by the electric motors 41 is corrected to increase as the detected temperature Tp such as the outside air temperature or the temperature of the electric drum brakes 40, 40 increases. This is because when the outside air temperature, the temperature of the electric drum brakes 40, 40, etc. rise,
Brake linings 219a, 219b and drum 206
This is because a large braking force is required as the temperature increases because the coefficient of friction between the two decreases. Therefore, the correction can be made to eliminate or reduce the difference in the braking force due to the brake operation even if the environmental temperature of the electric brake changes.

In the above-described embodiment and the modified example, in the determination process of step S16, the stop of the vehicle is included in the forward side (the side in which the target pressure P * is set small). This is because a large braking force is not required when the vehicle is stopped or almost stopped. In consideration of this point, in addition to the processing of the above-described embodiment and the modified example, even when the vehicle moves forward or when the vehicle moves backward, the target pressing force P increases as the absolute speed of the vehicle decreases.
It is preferable to add a control process for reducing *.

In the process of step S16, the forward or backward movement of the vehicle is detected based on the vehicle speed V detected by the vehicle speed sensor 51. When a sensor is provided, forward and backward may be determined according to the rotation direction of the wheel by the wheel speed sensor.

In the above-described embodiment and the modified example, the flat road is included on the downhill (the side where the target pressure P * is set small) in the determination processing of step S22. This is because a large braking force is not required when the vehicle is stopped on a flat road. In consideration of this point, in addition to the processing of the above-described embodiment and the modified example, even when the vehicle is stopping on the uphill or the vehicle is stopping on the downhill, the target is set as the absolute inclination angle of the road surface decreases. It is preferable to add a control process for reducing the pressure P *.

Further, in the above-described embodiment and the modified example, in order to make the electric current flowing through the electric motors 41, 41 in accordance with the depressing operation force F of the brake pedal 11 larger when the vehicle is moving backward than when moving forward, steps S18 and S18 are executed. In S20, the value of the operating force-pressure table is made different between when the vehicle is moving forward and when the vehicle is moving backward. However, after determining one of the target pressures P * when the vehicle is moving forward and backward, using the table, a predetermined value is added to the determined target pressure P *, or the determined target pressure P * is determined. By subtracting a predetermined value from * or multiplying the determined target pressing force P * by a predetermined value, the target pressing force P * may be made larger when the vehicle moves backward than when the vehicle moves forward. Further, instead of the table, one or both of the target pressurizing forces P * at the time of forward movement and reverse movement of the vehicle may be determined by a function prepared in advance.

When the parking brake is requested by operating the parking brake operator 20, the target pressure P * for either the downhill or the uphill is determined, and then the target pressure P * is determined. The other target pressure P * is determined by adding a predetermined value, subtracting the predetermined value from the determined target pressure P *, or multiplying the determined target pressure P * by a predetermined value. And the target pressure P * for the uphill
May be made larger than the target pressure P * for the downhill.

Instead of making the target pressure P * different between the forward and reverse travels, or making the target pressure P * different between the downhill and the uphill, step S28. May be different from each other in the target current I * derived by the conversion process of the above or the duty ratio DR derived by the conversion process of the step S30. In this case, for the same target pressing force P *, the target current I * or the duty ratio DR is increased when the vehicle is traveling backward as compared with when the vehicle is traveling forward, and is increased when traveling on an uphill slope as compared with when traveling downhill.

In the above-described embodiments and modifications, a manually operated switch is used as the parking brake operator 20. Instead, a manually operated dial operator, slide operator, or the like may be used. Etc. can also be adopted. In this case, the target pressing force P * can be continuously changed according to the operation position of the dial operator, the slide operator, or the like. In this case as well, when the operation positions of the dial operator, the slide operator, and the like are the same, the target pressing force P * when the vehicle is stopped on the uphill and the target pressure P * when the vehicle is stopped on the downhill are obtained. Needless to say, the target pressure P * is set to be larger than the target pressure P * by a predetermined amount. Further, instead of manual operation, various operators such as a switch operator, a dial operator, and a slide operator operated by a foot can be used.

In the above-described embodiment and the modified examples, the duo-servo type (DS type) is used as the electric drum brakes 40, 40, but the leading / trading type (LT type) may be used. The structure of this leading / trading type electric drum brake is shown in FIG. 10 along with FIG.
In this leading / trading type electric drum brake, an anchor pin 208 is provided at the position of the strut 210 in FIG. 9 described above, and the strut 210 is omitted. When the vehicle moves forward, X3 in FIG. The surface pressure of the portion is high, and during reverse, the surface pressure of the portion Y3 in FIG. The properties regarding the friction coefficient between the brake lining and the drum are the same as those of the duo servo type.

Therefore, the same operating force F * can be applied to the leading / trading type electric drum brake by the method adopted in the above embodiment and various modifications.
In contrast, the current flowing through the electric motor 41 is made larger when the vehicle is moving backward than when the vehicle is moving forward. Also, when a parking brake is requested by operating the parking brake operator 20,
According to the method adopted in the above embodiment and various modifications, the electric current flowing through the electric motor 41 is increased when the vehicle is stopping on an uphill slope compared to when the vehicle is stopping on a downhill slope. Thereby, also in this case, it is possible to correct the difference in the braking force related to the friction coefficient between the brake lining and the drum.

In the leading / trading type electric drum brake, the lever ratio of the lever 230a driven by the electric motor 41 is greatly affected. That is, when the distance from the driving point by the electric motor 41 to the contact point with the strut 216 is L1, the distance from the contact point to the pin 232a is L2, and the driving force by the electric motor 41 is Fm, the brake shoe 202b is pressed against the drum 206 with a force proportional to (L1 + L2) · Fm / L2. On the other hand, the brake shoe 202a is pressed against the drum 206 with a force proportional to L1 · Fm / L2. Thus, according to the configuration shown in FIGS. 10A and 10B, the portion of X3 where the surface pressure is high when the vehicle is moving forward is affected by the lever ratio more than the portion of Y3 where the surface pressure is high when the vehicle is moving backward. Receive higher.

Therefore, when the leading / trading type electric drum brake having the structure shown in FIGS. 10A and 10B is employed, the same depressing operation force F of the brake pedal 11 is applied when the vehicle is traveling in reverse. Electric motor 41
By adjusting the target pressure P *, the target current I *, the duty ratio DR, and the like, the current flowing through the electric motor 41 is made larger than the current flowing through the electric motor 41 when the vehicle is moving forward by the amount by which the influence of the lever ratio is canceled. It is good to control. The same applies to the case of requesting the parking brake by operating the parking brake operation member 20. The current flowing through the electric motor 41 on an uphill is lower than the current flowing on the electric motor 41 on a downhill by the lever ratio. It is better to make the control even larger by the amount that cancels out the influence of.

The electric drum brakes 40, 40 are not limited to the duo-servo type and the leading / trading type, but may be a drum brake of a two-leading type or a uni-servo type. Also in this case, it is preferable that the current flowing to the electric motor when the vehicle is moving backward is controlled to be larger than the current flowing to the electric motor when the vehicle is moving forward for the same depressing operation force F of the brake pedal 11. The same applies to a request for a parking brake by operating the parking brake operator 20. In the case of an uphill, the current flowing to the electric motor is
In the case of a downhill, it is preferable to control the current to be larger than the current flowing to the electric motor.

In the above-described embodiment and modifications, the electric drum brakes 40, 4 are provided only on the rear wheels RL, RR.
However, the electric drum brakes 40, 40 may be applied to the front wheels FL, FR. Also in this case, similarly to the above, it is preferable to control the current flowing to the electric motor.

Further, the present invention can be embodied in various modifications and improvements based on the knowledge of those skilled in the art, in addition to the above-described embodiments and modifications. Therefore, the technical scope of the present invention should be interpreted in consideration of these points.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an entire vehicle braking device according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the electric drum brake of FIG.

FIG. 3 is a flowchart of a program executed by the microcomputer of FIG. 1;

FIG. 4 is a graph showing a change characteristic of a pressing force with respect to an operation force.

FIG. 5 is a graph showing a change characteristic of a target current with respect to a target pressing force.

FIG. 6 is a graph showing a change characteristic of a duty ratio with respect to a target current.

FIG. 7 is a flowchart showing a part of a program executed by the microcomputer of FIG. 1 according to a modification of the embodiment.

8A is a graph showing a change characteristic of a correction coefficient with respect to a road surface friction coefficient, and FIG. 8B is a graph showing a change characteristic of a correction coefficient with respect to a temperature.

9A is a schematic diagram of a duo-servo type electric drum brake for explaining the operation of the electric drum brake when the vehicle advances, and FIG. 9B is a schematic diagram of the same type electric drum brake when the vehicle moves backward. It is a schematic diagram of the brake for explaining operation.

10A is a schematic diagram of the leading / trading type electric drum brake for explaining the operation of the leading / trading type electric drum brake when the vehicle is moving forward, and FIG. 10B is a schematic diagram of the same type of electric drum brake when the vehicle is moving backward. FIG. 4 is a schematic diagram of the brake for explaining the operation of the brake.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Service brake pedal device, 11 ... Brake pedal, 13 ... Brake pedal switch, 14 ... Operating force sensor, 20 ... Parking brake operator, 30 ... Electric disc brake, 31 ... Electric motor, 40 ... Electric drum brake, 41 ... Electric motor, 51 ... Vehicle speed sensor, 52
... tilt sensor, 53 ... controller, 55 ... driver,
56: Road surface friction coefficient sensor, 57: Temperature sensor, 100
... microcomputer, 200 ... backing plate, 202a, 202b ... brake shoe, 206 ... brake drum, 207 ... electric actuator, 208 ...
Anchor pins, 219a, 219b ... brake lining.

Claims (4)

[Claims] An electric drum brake for applying a braking force to a wheel by pressing a pair of brake linings against a drum that rotates integrally with the wheel by a driving force of an electric motor; A braking device for a vehicle, comprising: a motor control unit that controls a pressing force of the brake lining against the drum by flowing to a motor; a determination unit that determines whether the vehicle is moving forward or backward; Motor current changing means for controlling the motor control means in accordance with the determination result by the means, so that the motor current when the vehicle is moving backward is larger than the motor current when the vehicle is moving forward. A braking device for a vehicle, comprising: 2. An electric drum brake for applying a braking force to a wheel by pressing a pair of brake linings against a drum which rotates integrally with a wheel by a driving force of an electric motor, and a predetermined motor current in response to a parking braking request. And a motor control means for braking the wheels by flowing the electric motor to the electric motor, wherein the determination means determines whether the vehicle is stopped on an uphill slope or a downhill slope, Motor control means for controlling the motor control means in accordance with the determination result to make the motor current when the vehicle stops on an uphill slope larger than the motor current when the vehicle stops on a downhill slope. And a vehicle braking device. 3. A braking device for a vehicle according to claim 1, wherein a road surface condition detecting means for detecting a road surface condition where the vehicle is located, and a current flowing through the electric motor according to the detected road surface condition. And a current correction control means for performing correction control on the vehicle. 4. A braking device for a vehicle according to claim 1, wherein a temperature detecting means for detecting an environmental temperature of the electric brake, and a current flowing through the electric motor is corrected according to the detected environmental temperature. A vehicle braking device comprising: a current correction control means for controlling the vehicle.