JP2013180670A - Braking force control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a braking force control device that achieves desired attitude control performance irrespective of a design condition of a vehicle, and to control attitude of the vehicle positively on the basis of a traveling condition of the vehicle.SOLUTION: A braking force control device 140 decides a braking force distribution to be applied to wheels, on the basis of driving operation information such as driver's brake operation amount or steering wheel operation amount, so as to control a vehicle 100 in a predetermined state. The braking force distribution corresponds to a ratio between the braking force to be applied to front wheels of the vehicle and the braking force to be applied to rear wheels, or a ratio between the braking force based on regenerative brake and the braking force based on mechanical brake.

Description

  The present invention relates to a braking force control device that controls a braking force applied to each wheel of a vehicle.

  Conventionally, suspension mechanisms mounted on vehicles incorporate geometries that realize attitude control performance such as anti-dive, anti-lift, and anti-squat, and mainly control the vehicle attitude during braking and driving. . For example, in Patent Document 1 below, front and rear wheel braking force distribution control means for controlling the front wheel braking force distribution and the rear wheel braking force distribution to be changeable when the necessary braking force is distributed to the front wheel and rear wheel braking means of the vehicle. And suspension control means capable of adjusting the dynamic characteristics of the suspension for suspending the front and rear wheels of the vehicle on the vehicle body, and the vehicle pitch generated by the distribution change by the front and rear wheel braking force distribution control means in the suspension control means A vehicle attitude control device that adjusts the dynamic characteristics of a suspension so as to suppress the behavior is disclosed.

JP 2005-28934 A

  However, the above-described suspension mechanism according to the related art has a problem in that the setting of various geometries may be restricted due to the alignment constraint condition and the desired posture control performance may not be realized. In addition, the suspension mechanism according to the prior art has a problem in that the effect is passively exerted depending on the result of the braking / driving force acting on the vehicle, and active posture control may not be possible.

  The present invention has been made in view of the above-described problems of the prior art, achieves a desired attitude control performance regardless of the design conditions of the vehicle, and positively changes the vehicle attitude based on the running state of the vehicle. It is an object to provide a braking force control device that can be controlled.

  In order to solve the above-described problems and achieve the object, a braking force control device according to the present invention is a braking force control device that controls a braking force applied to each wheel of a vehicle, and is operated by a driver of the vehicle. Based on the driving operation information acquisition means for acquiring operation information and the driving operation information acquired by the driving operation information acquisition means, the braking force distribution to be applied to each wheel is controlled to a predetermined state of the vehicle. And a control means for applying the braking force to each wheel based on the braking force distribution determined by the determining means.

  According to the first aspect of the present invention, the braking force distribution to each wheel that has a different influence on the vehicle posture during braking is determined so as to control the vehicle posture to a predetermined state. Thus, it is possible to effectively control the attitude of the vehicle without being affected by the setting constraint conditions. Thereby, the vehicle posture at the time of braking can be stabilized, and a passenger's sense of security can be enhanced. Further, by controlling the vehicle posture using the braking force distribution of the vehicle, the control amount of the vehicle posture by the suspension mechanism can be reduced, and the degree of freedom in designing the suspension mechanism can be improved.

  According to the invention of claim 2, the distribution of braking force to the front wheels and the rear wheels is changed. Since the braking force on the front wheels and the rear wheels has different influences on the vehicle posture, the posture of the vehicle can be positively controlled by changing these distributions.

  According to the invention of claim 3, when the required braking force is small, the ratio of the braking force applied to the rear wheel is increased to enhance the braking effect, and when the required braking force is large, the ratio of the braking force applied to the front wheel is increased. The stability of the vehicle posture can be prioritized.

  According to the invention of claim 4, the braking force distribution between the braking force based on the regenerative force and the braking force based on the operation of the brake mechanism is changed on the same axle. Since the braking force based on the regenerative force and the braking force based on the operation of the brake mechanism have different effects on the vehicle attitude, the attitude of the vehicle can be positively controlled by changing their distribution.

  According to the invention of claim 5, when the required braking force is small, the ratio of the braking force based on the regenerative force is increased to improve fuel efficiency, and when the required braking force is large, the ratio of the braking force based on the operation of the brake mechanism is increased. The stability of the vehicle posture can be prioritized.

  According to the invention of claim 6, when the steering wheel operation amount is small, the ratio of the braking force based on the regenerative force is increased to improve fuel efficiency, and when the steering wheel operation amount is large, the braking force ratio based on the operation of the brake mechanism is increased. The stability of the vehicle posture can be prioritized.

It is explanatory drawing which shows the structure of the vehicle 100 to which the braking force control apparatus concerning embodiment is applied. It is explanatory drawing which shows typically the force which acts at the time of vehicle braking. It is a graph which shows an example of braking force distribution of front and rear wheels. It is a graph which shows an example of braking force distribution with an axle braking torque and a mechanical brake. It is a graph which shows the other example of braking force distribution with an axle braking torque and a mechanical brake. 5 is a flowchart showing a procedure of a braking force control process by a braking force control device 140. It is a figure which shows an example of a structure of an electrically driven brake.

  Exemplary embodiments of a braking force control apparatus according to the present invention will be explained below in detail with reference to the accompanying drawings. In the following embodiment, an example in which the braking force control device according to the present invention is applied to a vehicle 100 that is an electric automobile will be described.

(Embodiment)
FIG. 1 is an explanatory diagram illustrating a configuration of a vehicle 100 to which the braking force control device according to the embodiment is applied. In FIG. 1, illustrations of components that are not related to the application of the braking force control device to the vehicle 100 are omitted. A vehicle 100 is an electric vehicle, and travels by rotating a tire 101 by driving a motor 102 with electric power stored in a battery (not shown).

  The operation of the handle 113 by the driver is transmitted to the tire 101 via a steering shaft, a gear box, etc. (not shown), and the direction of the tire 101 is changed. The handle 113 is provided with a rotation angle sensor 114 that detects a handle rotation angle. A value detected by the rotation angle sensor 114 is output to a braking force control device 140 described later.

  The rotation of the tire 101 is braked by the operation of the brake pedal 103 and an accelerator pedal (not shown) by the driver. When the brake pedal 103 is depressed by the driver, the piston in the master cylinder 104 is driven by the depression force, and the brake fluid filled in the master cylinder 104 is pushed out. The pushed brake fluid is transmitted to the brake caliper 107 through the brake pipe 105. Note that the depression force on the brake pedal 103 and the accelerator pedal is measured by a pedal sensor (not shown) and output to a braking force control device 140 described later.

  When the stepping force on the brake pedal 103 is transmitted to the master cylinder 104, the pressure necessary for braking the vehicle 100 is obtained by amplifying the stepping force by the brake booster 110. The interior of the brake booster 110 is divided into two compartments: an air chamber on the brake pedal 103 side and a negative pressure chamber on the master cylinder 104 side. Due to the pressure difference between the two sections, a force is generated from the brake pedal 103 side toward the master cylinder 104 side, and assists in pushing the piston in the master cylinder 104. The negative pressure in the negative pressure chamber of the brake booster 110 is generated by the electric vacuum pump 111.

  The motor rotation speed sensor 121 measures the rotation speed of the motor 102 per unit time. The wheel speed sensor 122 is provided in each tire 101 and measures the rotational speed of each tire 101.

  The brake caliper 107 is provided with a brake pad 108 (see FIG. 2) and a piston. In the brake caliper 107, the piston is driven by the action of the pressure transmitted to the brake fluid and presses the brake pad 108 against the disc rotor 106. Then, the friction between the disc rotor 106 and the brake pad 108 releases the kinetic energy of the tire 101 as heat energy into the air, the rotation of the tire 101 stops, and the vehicle 100 stops.

  Here, the pressing force of the brake pad 108 against the disc rotor 106 is controlled by the braking force control device 140. The braking force control device 140 controls the braking force acting on each tire by controlling the hydraulic pressure of the brake fluid transmitted to the brake caliper 107 of the tire 101 for each of the left and right front and rear wheels of the vehicle 100.

  In the present embodiment, the braking force control device 140 controls the braking force of each tire 101 to control the posture of the vehicle 100 during braking. Although not shown in FIG. 1, each tire 101 is provided with a suspension mechanism, and the attitude of the vehicle 100 is controlled by geometry such as anti-dive and anti-lift. In the present embodiment, the attitude of vehicle 100 can be more positively controlled by using braking force control device 140 for attitude control of vehicle 100 in addition to the suspension mechanism.

  The braking force control device 140 includes a CPU, a ROM that stores and stores a control program, a RAM as an operation area of the control program, an EEPROM that holds various data in a rewritable manner, an interface unit that interfaces with peripheral circuits, and the like. Consists of including. The braking force control device 140 is connected to each part of the vehicle 100 via an interface part, exchanges information with each part, and controls each part.

Moreover, the braking force control apparatus 140 implement | achieves the driving | running | working state acquisition part 141, the operation information acquisition part 142, the determination part 143, and the control part 144, when the said CPU runs the said control program.
The traveling state acquisition unit 141 acquires traveling state information of the vehicle 100. The traveling state information is information such as traveling speed, acceleration, and angular speed of the vehicle 100, for example. The traveling state acquisition unit 141 acquires traveling state information by acquiring output values from, for example, the motor rotation speed sensor 121, the wheel speed sensor 122, an angular speed sensor (not shown), and the like.

  The operation information acquisition unit 142 acquires driving operation information by the driver of the vehicle 100. The driving operation information includes, for example, the depression amount of the brake pedal 103 or the accelerator pedal (brake operation amount and accelerator operation amount) by the driver, the rotation amount of the handle 113 (handle operation amount), and the like. The operation information acquisition unit 142 acquires driving operation information by acquiring an output value from a pedal sensor, a rotation angle sensor 114, or the like provided in a brake pedal or an accelerator pedal, for example.

  Based on the driving operation information acquired by the operation information acquisition unit 142, the determination unit 143 determines the braking force distribution to be applied to each wheel (tire 101) so as to control the attitude of the vehicle 100 to a predetermined state. . The determination unit 143 uses the driving operation information acquired by the operation information acquisition unit 142 to change the braking force distribution when it is predicted that the posture of the vehicle 100 becomes unfavorable, such as a dive or a lift. Then, the posture of the vehicle 100 is maintained in a predetermined state (a state close to the horizontal). At this time, the determination unit 143 may determine the braking force distribution using the traveling state information acquired by the traveling state acquisition unit 141.

  For example, the determination unit 143 determines the distribution of the braking force that acts on the front wheels of the vehicle 100 and the braking force that acts on the rear wheels. For example, the determination unit 143 determines a braking force based on a regenerative force generated when the vehicle 100 is decelerated, that is, a braking force based on an axle braking torque (regenerative brake), and a braking force based on an operation of a brake mechanism provided on each wheel, that is, a mechanical force. Determine the braking force distribution by the brakes. This is because the influence of the braking force by each of them on the posture of the vehicle 100 is different.

  FIG. 2 is an explanatory diagram schematically showing the force that acts during vehicle braking. 2 (a) shows the force exerted by the axle braking torque, and FIG. 2 (b) shows the force exerted by the mechanical brake. Further, in order to identify the reference numerals shown in FIGS. 2A and 2B, the reference numerals shown in FIG. 2A are suffixed with “1” and the reference numerals shown in FIG. 2B. Is suffixed with “2”.

In FIG. 2, assuming that the braking force acting on the front wheels of the vehicle is F _BF and the braking force acting on the rear wheels is F _BR , N _BF on the front wheel side and N _BR on the rear wheel side are the forces that control the vehicle posture. Join. The _{N BF} and _{N BR} is the braking force _F BF, instantaneous center of rotation of the wheel when applied is FB _{R C} F, _{C R} and the braking force _{F BF,} a straight line connecting the point of action of _{F BR,} the horizontal plane When the angles are θ _F and θ _R , they are expressed by the following formulas (1) and (2), respectively.
N _BF = F _BF × tan θ _F (1)
N _BR = F _BR × tan θ _R (2)

As shown in FIG. 2, the axle braking torque and the mechanical brake are different in the point of action of the braking force, and therefore the force (N _BF , N _BR ) exerted on the vehicle posture by the braking force is different. The determination unit 143 determines the braking force distribution to be applied to each wheel by using such a relational expression of force in addition to the above-described traveling state information and driving operation information. In the present embodiment, the anti-lift effect is greater than the anti-dive effect (| N _BF | <| N _BR |), and the mechanical brake effect is greater than the regenerative brake effect (| N _BF1 | < | N _BF2 |, | N _BR1 | <| N _BR2 |).

  FIG. 3 is a graph showing an example of braking force distribution between the front and rear wheels. In FIG. 3, the vertical axis indicates the ratio of the braking force applied to the front wheels to the braking force applied to the rear wheels (front wheel braking force / rear wheel braking force), and the value increases as the front wheel braking force increases. The larger the braking force, the smaller the value. The horizontal axis represents the required braking force calculated from the driver's brake operation amount. As shown in FIG. 3, when the required braking force is small, the ratio of the rear wheel braking force that has a large control effect on the vehicle posture is increased and the vehicle posture is maintained by the anti-lift effect. On the other hand, when the required braking force is large, the load moves to the front wheel side, so the rear wheel braking force is weakened and the anti-dive effect of the front wheel is utilized to maintain the stability of the vehicle behavior.

  FIG. 4 is a graph showing an example of braking force distribution between the axle braking torque and the mechanical brake. In FIG. 4, the vertical axis indicates the ratio (regenerative force / mechanical brake) between the braking force generated by the axle braking torque (regenerative brake) and the braking force generated by the mechanical brake, and the value increases as the braking force generated by the regenerative brake increases. The value decreases as the braking force by the mechanical brake increases. The horizontal axis represents the required braking force calculated from the driver's brake operation amount. As shown in FIG. 4, when the required braking force is small, the ratio of the regenerative brake is increased to improve the fuel consumption (electric cost). On the other hand, when the required braking force is large, priority is given to posture control by increasing the ratio of mechanical brakes that have a large control effect on the vehicle posture even with the same braking force.

  FIG. 5 is a graph showing another example of the distribution of braking force between the axle braking torque and the mechanical brake. In FIG. 5, the vertical axis represents the ratio (regenerative force / mechanical brake) between the braking force by the axle braking torque (regenerative brake) and the braking force by the mechanical brake, as in FIG. The horizontal axis represents the driver's handle operation amount (absolute value of the handle rotation angle). As shown in FIG. 5, when the steering wheel operation amount is small, that is, in the vicinity of a straight line, the ratio of the regenerative brake is increased to improve fuel efficiency. On the other hand, when the steering wheel operation amount is large, that is, during turning, priority is given to the posture control by increasing the ratio of the mechanical brake having a large control effect on the vehicle posture even with the same braking force.

  As described above, the determination unit 143 determines the braking force distribution to be applied to each wheel based on the traveling state information of the vehicle and the driving operation information of the driver. In addition to the stability of the vehicle posture, it may be possible for the driver to set what elements such as fuel efficiency are prioritized.

  Returning to the description of FIG. 1, the control unit 144 applies a braking force to each tire 101 based on the braking force distribution determined by the determination unit 143. The control unit 144 applies a predetermined braking force to each tire 101 by controlling the hydraulic pressure of the brake fluid transmitted to the brake caliper 107 of each tire 101. Further, the control unit 144 controls the braking force by the regenerative brake by controlling the rotational torque of the motor 102.

  FIG. 6 is a flowchart showing the procedure of the braking force control process by the braking force control device 140. In the flowchart of FIG. 6, the braking force control device 140 waits until the vehicle starts running (step S601: No loop), and when the vehicle starts running (step S601: Yes), the operation information acquisition unit 142. Thus, pedal stroke information indicating the pedal operation amount of the driver is acquired (step S602). Next, the braking force control device 140 acquires handle rotation angle information indicating the driver's handle operation amount by the operation information acquisition unit 142 (step S603). At this time, the traveling state acquisition unit 141 also acquires traveling state information of the vehicle 100 as needed.

  Subsequently, the braking force control device 140 calculates the driver's required braking force by the determination unit 143 (step S604), and first determines the braking force distribution of the front and rear wheels (step S605). Next, the determination unit 143 determines the braking force distribution (regeneration distribution) between the axle braking torque and the mechanical brake (step S606). At this time, the determination unit 143 calculates both the braking force distribution based on the required braking force shown in FIG. 4 and the braking force distribution based on the steering wheel operation amount shown in FIG. 5, and adopts the smaller value. Good. As a result, it is possible to employ a braking force distribution that places importance on the stability of the posture, thereby enhancing the passenger's sense of security. In this embodiment, the smaller one of the braking force distribution based on the required braking force and the braking force distribution based on the steering wheel operation amount is adopted, but each is weighted using a fixed value or another physical quantity. The method of superimposing can be taken.

  Then, the braking force control device 140 performs the braking force control of the front and rear wheels and the braking force control of the regenerative brake and the mechanical brake by the control unit 144 (step S607). Until the vehicle 100 finishes traveling (step S608: No), the braking force control device 140 returns to step S602 and repeats the subsequent processing. And if the vehicle 100 complete | finishes driving | running | working (step S608: Yes), the process by this flowchart will be complete | finished.

  In the present embodiment, the brake of the vehicle 100 has been described as a hydraulic brake, but the braking force control apparatus according to the present invention may be applied to an electric brake using an electric caliper. The electric brake is a brake system that obtains a braking force by operating an electric motor or the like mounted on a caliper and pressing a brake pad against a rotor. In the electric brake, the driver's operation is detected by a pedal stroke sensor, and the electric motor is controlled based on the operation amount (brake-by-wire).

  FIG. 7 is a diagram illustrating an example of the configuration of the electric brake. The electric brake device shown in FIG. 7 is provided on each of the four wheels of the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel, and a motor drive current corresponding to the target braking torque of each wheel is applied to the electric motor of each wheel. Sent. As shown in the figure, a brake rotor 1 that rotates together with wheels is provided, and the brake rotor 1 is pressed by a pair of brake pads 2 to generate braking torque and deceleration torque by frictional force. That is, the caliper 3 is supported on the vehicle body side so as to freely reciprocate (in the horizontal direction in the figure), and the electric motor 4 that is an electric actuator is fixed to the caliper 3. A piston 5 is slidably fitted to the caliper 3.

  A nut member 6 is fixed inside the piston 5, and a screw portion provided on the drive shaft 7 of the electric motor 4 is screwed into the nut member 6. When electric power is supplied to the electric motor 4, the drive shaft 7 rotates forward and backward, and the piston 5 is driven to reciprocate in the axial direction (left and right in the figure) via the nut member 6. Brake pads 2 are respectively provided on the caliper 3 facing one surface (the left surface in the drawing) of the brake rotor 1 and the tip portion of the piston 5 facing the other surface (the right surface in the drawing) of the brake rotor 1. Is attached.

  For example, when the drive shaft 7 of the electric motor 4 rotates in the forward direction, the piston 5 is driven in the left direction in the figure, and the brake pad 2 attached to the piston 5 presses the brake rotor 1 and at the same time the caliper 3 is counteracted. The brake rotor 1 is pressed by the pair of brake pads 2 by sliding in the right direction in the figure by force. As a result, braking torque and deceleration torque are generated. For example, when the drive shaft 7 of the electric motor 4 rotates in the reverse direction, the pair of brake pads 2 are separated from the brake rotor 1. Thereby, braking torque and deceleration torque are released.

  A control unit (ECU) 8 for controlling the electric motor 4 is provided, and brake pedal operation information (operation amount, operation speed) is input to the ECU 8. A control signal (current value command signal: motor drive current) is sent from the ECU 8 to the electric motor 4 in accordance with the brake pedal operation information, and the rotation direction and rotation speed of the drive shaft 7 are controlled. That is, the braking torque of each wheel is controlled.

  The electric motor 4 is provided with a rotation angle sensor 9 that detects the rotation angle of the drive shaft 7 and a current detection sensor 10 that detects a drive current. The rotation angle of the drive shaft 7 and the current value of the electric motor 4 are detected, and the rotation angle and the current value are input to the ECU 8 and feedback controlled.

  As described above, the braking force control device 140 according to the embodiment distributes the braking force to each wheel that has a different influence on the posture of the vehicle 100 during braking, and sets the posture of the vehicle 100 to a predetermined state. Decide to control. For this reason, the attitude of the vehicle 100 can be effectively controlled without being affected by the setting constraint conditions unlike the suspension mechanism. Further, by controlling the vehicle attitude using the braking force distribution of the vehicle 100, the control amount of the vehicle attitude by the suspension mechanism can be reduced, and the degree of freedom in designing the suspension mechanism can be improved.

  In addition, the braking force control device 140 changes the braking force distribution of the braking force on the front wheels and the rear wheels that have different effects on the vehicle posture, so that the posture of the vehicle 100 can be positively controlled. For example, when the required braking force is small, priority is given to the stability (control) of the vehicle posture by increasing the ratio of the braking force applied to the rear wheel, and when the required braking force is large, the ratio of the braking force applied to the front wheel is increased. The stability of vehicle behavior can be prioritized.

  Further, the braking force control device 140 changes the braking force distribution of the regenerative brake and the mechanical brake, which have different effects on the vehicle posture, on the same axle, so that the posture of the vehicle 100 can be positively controlled. For example, when the required braking force is small, the ratio of the braking force based on the regenerative force is increased to improve fuel efficiency, and when the required braking force is large, the ratio of the braking force based on the operation of the brake mechanism is increased to stabilize the vehicle posture. Can be prioritized. Further, for example, when the steering wheel operation amount is small, the ratio of the braking force based on the regenerative force is increased to improve fuel efficiency, and when the steering wheel operation amount is large, the ratio of the braking force based on the operation of the brake mechanism is increased to increase the vehicle posture. Stability can be prioritized.

  DESCRIPTION OF SYMBOLS 100 ... Vehicle, 101 ... Tire, 102 ... Motor, 103 ... Brake pedal, 104 ... Master cylinder, 105 ... Brake piping, 106 ... Disc rotor, 107 ... Brake caliper, 108 ... Brake pad , 110 ... Brake booster, 111 ... Electric vacuum pump, 113 ... Handle, 114 ... Rotation angle sensor, 121 ... Motor rotation speed sensor, 122 ... Wheel speed sensor, 130 ... EV-ECU, 140 ... ... braking force control device, 141 ... running state acquisition unit, 142 ... operation information acquisition unit, 143 ... determination unit, 144 ... control unit.

Claims (6)

A braking force control device for controlling a braking force applied to each wheel of a vehicle,
Driving operation information acquisition means for acquiring driving operation information by a driver of the vehicle;
Determining means for determining the braking force distribution to be applied to each wheel based on the driving operation information acquired by the driving operation information acquiring means so as to control the attitude of the vehicle to a predetermined state;
Control means for applying the braking force to each wheel based on the braking force distribution determined by the determining means;
A braking force control device comprising: The determining means determines a distribution of a braking force to be applied to a front wheel of the vehicle and a braking force to be applied to a rear wheel of the vehicle;
The braking force control apparatus according to claim 1, wherein the control means causes the braking force to act on the front wheel and the rear wheel based on the distribution. The driving operation information acquisition means acquires brake operation amount information by the driver,
The determining means calculates the driver's required braking force from the brake operation amount information, and when the required braking force is small, increases the ratio of the braking force applied to the rear wheel, and when the required braking force is large. The braking force control apparatus according to claim 2, wherein a ratio of a braking force applied to the front wheels is increased. The determining means determines a distribution of a braking force based on a regenerative force generated during deceleration of the vehicle and a braking force based on an operation of a brake mechanism provided on each wheel;
The control means according to any one of claims 1 to 3, wherein a braking force based on the regenerative force and a braking force based on an operation of the brake mechanism are applied based on the distribution. Power control device. The driving operation information acquisition means acquires brake operation amount information by the driver,
The determining means calculates the driver's required braking force from the brake operation amount information, and when the required braking force is small, increases the ratio of the braking force based on the regenerative force, and when the required braking force is large. The braking force control device according to claim 4, wherein a ratio of a braking force based on an operation of the brake mechanism is increased. The driving operation information acquisition means acquires handle operation amount information by a driver,
The determining means increases the ratio of the braking force based on the regenerative force when the handle operation amount is small, and increases the ratio of the braking force based on the operation of the brake mechanism when the handle operation amount is large. The braking force control apparatus according to claim 4 or 5.

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