JP2006281872A - Brake device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To set the optimum braking force when a relationship of stepping force of a brake pedal and a stroke is changed. <P>SOLUTION: When a braking signal output means outputs a braking signal according to operation of the brake pedal, a brake actuator is operated to generate the braking force for braking a wheel and a reaction force giving means gives reaction force relative to the operation of the brake pedal. A control means for controlling operation of the brake actuator and the reaction force giving means based on the braking signal increases the braking force relative to the stroke of the brake pedal when the reaction force relative to the stroke of the brake pedal is increased at high speed traveling. Therefore, the braking force can be prevented from being lacked while obtaining brake feeling with rigid feeling at the high speed traveling. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a so-called brake-by-wire type brake device that generates a braking force by operating a brake actuator in response to a braking signal output in response to an operation of a brake operator by a driver.

  In a brake-by-wire type braking device, the braking force for the same pedaling force and the same pedal stroke is changed according to the vehicle speed to improve the braking response at high speeds and to brake at low speeds. Patent Documents 1 and 2 below are known to improve operability.

Also, in the brake-by-wire brake system, the braking force is increased during high-speed driving while facilitating adjustment of braking force during low-speed driving by reducing the pedal stroke relative to the depression force of the brake pedal as the vehicle speed increases. This is known from US Pat.
JP 2001-278020 A JP 2000-229564 A Japanese Patent Laid-Open No. 11-157439

  By the way, what is described in Patent Documents 1 and 2 is not referred to the relationship between the pedaling force and the stroke when changing the braking force, and what is described in Patent Document 3 is the pedaling force or the pedal stroke. There is no mention of the relationship of the braking force to.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to set an optimum braking force when changing the relationship between the depression force and stroke of a brake pedal.

  To achieve the above object, according to the first aspect of the present invention, a brake operator operated by a driver, a braking signal output means for outputting a braking signal corresponding to the operation of the brake operator, wheels A brake actuator that generates a braking force for braking, a reaction force applying means for applying a reaction force to the operation of the brake operator, and an operation of the brake actuator and the reaction force applying means based on a braking signal output by the braking signal output means Control means for controlling the braking device, wherein the control means changes the relationship of the braking force to the stroke of the brake operator when the relationship of the reaction force to the stroke of the brake operator is changed. Proposed.

  According to the invention described in claim 2, in addition to the structure of claim 1, the control means increases the braking force with respect to the stroke of the brake operator when the reaction force with respect to the stroke of the brake operator is increased. A brake device is proposed.

  According to the invention described in claim 3, in addition to the configuration of claim 1, the control means reduces the braking force with respect to the stroke of the brake operator when the reaction force with respect to the stroke of the brake operator is reduced. A brake device is proposed.

  The brake pedal 11 of the embodiment corresponds to the brake operator of the present invention, the reaction force applying motor 12 of the embodiment corresponds to the reaction force applying means of the present invention, and the encoder 13 of the embodiment is a braking signal of the present invention. Corresponding to the output means, the electronic control unit 19 of the embodiment corresponds to the control means of the present invention.

  According to the configuration of claim 1, when the braking signal output means outputs a braking signal in accordance with the operation of the brake operator operated by the driver, the braking actuator is activated to generate a braking force for braking the wheel, The reaction force applying means applies a reaction force to the operation of the brake operator. The control means for controlling the operation of the brake actuator and the reaction force applying means based on the braking signal changes the relationship of the braking force to the stroke of the brake operator when the relationship of the reaction force to the stroke of the brake operator is changed. Therefore, while adjusting the stroke of the brake operator to the optimal size according to the vehicle speed and the road surface friction coefficient, the relationship between the braking force and the pedaling force (reaction force) is prevented from changing, and the effect is much different from the normal time. You can give the driver a sense of security by not getting braking characteristics.

  According to the second aspect of the present invention, when the reaction force against the stroke of the brake operator is increased, the braking force with respect to the stroke of the brake operator is increased. Can be prevented.

  According to the third aspect of the present invention, when the reaction force with respect to the stroke of the brake operator is reduced, the braking force with respect to the stroke of the brake operator is reduced. Can be prevented and wheel lock on a road surface having a small friction coefficient can be suppressed.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.

  FIGS. 1 to 5 show a first embodiment of the present invention. FIG. 1 is a diagram showing an overall configuration of a brake-by-wire brake device, and FIG. 2 is a block diagram showing a circuit configuration of an electronic control unit. FIG. 3 is a diagram showing a table for retrieving reaction force from the stroke of the brake pedal and a table for retrieving braking force from the stroke of the brake pedal. FIG. 4 is a graph showing (stepping force / stroke) and (braking force / stroke). FIG. 5 is a diagram showing a relationship, and FIG. 5 is a graph showing a change in vehicle speed with respect to time, and a table for retrieving a reaction force from the stroke of a brake pedal.

  As shown in FIG. 1, the brake-by-wire brake device includes a brake pedal 11 as a brake operator operated by a driver's foot, and pivotally supports the upper end of the brake pedal 11 so as to be swingable. A reaction force applying motor 12 as a reaction force applying means and an encoder 13 as a braking signal output means are connected to the supporting shaft. The brake pedal 11 is applied with a reaction force according to the stroke amount by the reaction force spring 14, and the brake pedal 11 has an arbitrary magnitude according to the stroke amount, the stroke speed, or other signals by the torque generated by the reaction force application motor 12. Reaction force is applied. The reaction force applying motor 12 not only generates a reaction force with respect to the operation of the brake pedal 11, but also has a function of changing an initial position of the brake pedal 11 (a position when no pedal force is applied). The encoder 13 outputs a signal corresponding to the operation amount of the brake pedal 11 (that is, the stroke of the brake pedal 11). The brake switch 15 detects the operation of the brake pedal 11 by the driver.

  On the other hand, the brake actuator 18 connected to the wheel cylinder 17 provided on the front and rear wheels 16 (only one wheel is shown in FIG. 1) of the vehicle is generated by a hydraulic pump or a hydraulic cylinder driven by a motor. The brake fluid pressure is controlled to an arbitrary magnitude and supplied to the wheel cylinder 17 to brake the wheel 16. The master cylinder is connected to the brake pedal 11, and the wheel cylinder 17 is operated with the brake fluid pressure generated by the master cylinder when the brake actuator 18 becomes inoperable due to a power failure or a control device failure. A fail-safe mechanism can be provided.

  In addition to the encoder 13 and the brake switch 15, the electronic control unit 19 that controls the operation of the reaction force applying motor 12 and the brake actuator 18 includes a vehicle speed sensor 20, a yaw rate sensor 21, a shift position sensor 22, a navigation device 23, and a VICS reception. A device 24 is connected.

  As shown in FIG. 2, the electronic control unit 19 includes pedal stroke calculation means M1, pedal speed calculation means M2, passive reaction force estimation means M3, rigidity reaction force calculation means M4, and viscous friction reaction force calculation means M5. The active reaction force compensation current calculation means M6 and the current control means M7 are provided. Signals from the encoder 13 are input to the pedal stroke calculation means M1 and the pedal speed calculation means M2, and a reaction force is applied to the current control means M7. The actual motor 12 current is fed back.

  Next, the operation of the embodiment having the above configuration will be described.

  In FIG. 2, when the driver operates the brake pedal 11, signals from the encoder 13 are input to the pedal stroke calculating means M1 and the pedal speed calculating means M2, and the pedal stroke calculating means M1 calculates the stroke of the brake pedal 11 and the pedal. The speed calculation means M2 calculates the stroke speed of the brake pedal 11. The passive reaction force estimation means M3 estimates the passive reaction force, that is, the reaction force generated by the reaction force spring 14 based on the stroke of the brake pedal 11.

  The active reaction force is a reaction force generated by the reaction force applying motor 12, which includes a rigid reaction force that simulates a reaction force that depends on the pedal position (stroke) when the brake pedal 11 is depressed, and the brake pedal 11. And a viscous friction reaction force that simulates a reaction force due to a viscous friction resistance that depends on the stepping speed (stroke speed) when stepping on the pedal, and the rigidity reaction force is based on the stroke of the brake pedal 11. The viscous friction reaction force is calculated by the calculation means M4, and the viscous friction reaction force calculation means M5 is calculated based on the stroke speed of the brake pedal 11.

  The active reaction force compensation current calculation means M6 subtracts the passive reaction force estimated by the passive reaction force estimation means M3 from the added value of the stiffness reaction force and the viscous friction reaction force, and the active reaction force to be generated in the reaction force applying motor 12 And the active reaction force is converted into a compensation current to be supplied to the reaction force applying motor 12. The current control means M7 performs feedback control so that the actual current flowing through the reaction force applying motor 12 matches the compensation current.

  The stiffness reaction force calculated by the stiffness reaction force calculation means M4 is corrected as follows according to the vehicle speed.

  The stiffness reaction force calculation means M4 sets the relationship of the depression force (reaction force) with respect to the stroke of the brake pedal 11 so as to change according to the vehicle speed as shown in FIG. That is, even when the pedal effort of the brake pedal 11 is the same F1, the stroke S1 of the brake pedal 11 at the high vehicle speed is set to be smaller than the stroke S2 of the brake pedal at the low vehicle speed. Sometimes, the brake pedal 11 can be improved in rigidity and a safe brake feeling can be obtained.

  However, since the magnitude of the braking force is proportional to the stroke of the brake pedal 11, if the stroke of the brake pedal 11 is reduced at a high vehicle speed as shown in FIG. There is a possibility that the braking force will be insufficient. Therefore, in this embodiment, as shown in FIG. 3B, the magnitude of the braking force with respect to the stroke of the brake pedal 11 is set to increase at high vehicle speeds. That is, by setting the braking force BF2 at the high vehicle speed to be larger than the braking force BF1 at the low vehicle speed for the same stroke S1, the original braking force BF2 can be obtained with the small stroke S1.

  The horizontal axis in FIG. 4 indicates (treading force / stroke), and the vertical axis indicates (braking force / stroke). The straight line L extending from the origin corresponds to the characteristic that the braking force increases linearly with increasing pedaling force. To do. If the pedaling force at the high vehicle speed for the same stroke is double the pedaling force at the low vehicle speed (change from point a to point b), the braking force at the high vehicle speed for the same stroke is 2 times the braking force at the low vehicle speed. By doubling (change from point a to point c), the braking force can be increased linearly with respect to the increase in pedaling force, and the same effect as a conventional brake device can be obtained.

  By the way, if it carries out as mentioned above, it can increase braking force linearly with respect to the increase in pedaling force, but the stroke of the brake pedal 11 with respect to the same pedaling force becomes smaller than before, and operativity falls. Therefore, when (stepping force / stroke) is increased at the first rate of change, (braking force / stroke) is increased at a second rate of change smaller than the first rate of change, that is, the hatched area in FIG. By setting to, the increase rate of the braking force can be suppressed to be low, and the operability of the brake pedal 11 can be prevented from being lowered.

  As described above, when the ratio of (stepping force / stroke) is changed in accordance with the vehicle speed, as shown in FIG. 5A, when the brake pedal 11 is stepped on with the pedaling force F1 at the vehicle speed V0, the vehicle speed decreases to V1. As shown in FIG. 5B, the stroke of the brake pedal 11 increases from S1 to S2, which gives the driver a feeling of strangeness. Therefore, in this embodiment, the ratio of the pedaling force to the stroke when the brake pedal 11 is depressed at the vehicle speed V0 is maintained until the vehicle stops with the characteristic of the broken line in FIG. It is possible to prevent the driver from feeling uncomfortable by preventing the position of 11 from changing.

  Next, a second embodiment of the present invention will be described with reference to FIGS.

  In the first embodiment described above, the stiffness reaction force calculation means M4 changes the relationship of the pedaling force (reaction force) with respect to the stroke of the brake pedal 11 in accordance with the vehicle speed. The relationship of the treading force (reaction force) is changed according to the road surface friction coefficient as shown in FIG. That is, even when the pedal effort of the brake pedal 11 is the same F1, the stroke S2 of the brake pedal 11 on the road surface with the low friction coefficient is set to be larger than the stroke S1 of the brake pedal on the road surface with the high friction coefficient. As a result, the stroke of the brake pedal 11 can be increased on the road surface with a low friction coefficient, and the stroke of the brake pedal 11 can be finely adjusted so that the wheels do not lock.

  However, since the magnitude of the braking force is proportional to the magnitude of the stroke of the brake pedal 11, if the stroke of the brake pedal 11 is increased on a road surface with a low friction coefficient as shown in FIG. The braking force also increases, and the braking force may become excessive. Therefore, in this embodiment, as shown in FIG. 6B, the magnitude of the braking force with respect to the stroke of the brake pedal 11 is set so as to decrease on the road surface with a low friction coefficient. That is, by setting the braking force BF1 on the road surface with a low friction coefficient to be smaller than the braking force BF2 on the road surface with a high friction coefficient for the same stroke S1, it is possible to prevent the braking force from becoming excessive. be able to.

  The horizontal axis in FIG. 7 indicates (treading force / stroke), and the vertical axis indicates (braking force / stroke). The straight line L extending from the origin corresponds to the characteristic that the braking force increases linearly with increasing pedaling force. To do. Assuming that the treading force on the road surface with the low friction coefficient for the same stroke is 0.5 times the treading force on the road surface with the high friction coefficient (change from point a to point b), By making the braking force 0.5 times the braking force on the road surface with a high friction coefficient (change from point a to point c), the braking force can be reduced linearly with respect to the decrease in the pedaling force. The same effect as the brake device can be obtained.

  By the way, if it does as mentioned above, the stroke of the brake pedal 11 will become large and delicate adjustment of braking force will become easy, but the response of braking force with respect to operation of the brake pedal 11 will fall. Therefore, when (stepping force / stroke) is decreased at the first rate of change, the second rate of change to decrease (braking force / stroke) accordingly is made smaller than the first rate of change, that is, FIG. By setting the region in the shaded area, the responsiveness of the braking force to the operation of the brake pedal 11 can be ensured.

  Although the embodiments of the present invention have been described above, various design changes can be made without departing from the scope of the present invention.

  For example, in the embodiment, the brake pedal 11 is illustrated as the brake operator, but the brake operator may be a brake lever.

Diagram showing the overall configuration of a brake-by-wire brake device Block diagram showing circuit configuration of electronic control unit The figure which shows the table which searches reaction force from the stroke of a brake pedal, and the table which searches braking force from the stroke of a brake pedal Diagram showing the relationship between (stepping force / stroke) and (braking force / stroke) The figure which shows the graph which shows the change of the vehicle speed with respect to time, and the table which searches reaction force from the stroke of a brake pedal The figure which shows the table which searches reaction force from the stroke of a brake pedal based on 2nd Example, and the table which searches braking force from the stroke of a brake pedal The figure which shows the relationship between (stepping force / stroke) and (braking force / stroke) based on 2nd Example.

Explanation of symbols

11 Brake pedal (brake operator)
12 reaction force motor (reaction force applying means)
13 Encoder (braking signal output means)
16 Wheel 18 Brake actuator 19 Electronic control unit (control means)

Claims (3)

A brake operator (11) operated by a driver;
Braking signal output means (13) for outputting a braking signal according to the operation of the brake operator (11);
A brake actuator (18) for generating a braking force for braking the wheel (16);
Reaction force applying means (12) for applying a reaction force to the operation of the brake operator (11);
Control means (19) for controlling the operation of the brake actuator (18) and the reaction force applying means (12) based on the braking signal output by the braking signal output means (13),
The said control means (19) changes the relationship of the braking force with respect to the stroke of a brake operation element (11), when the relationship of the reaction force with respect to the stroke of a brake operation element (11) is changed.   The said control means (19) enlarges the braking force with respect to the stroke of a brake operation element (11), when the reaction force with respect to the stroke of a brake operation element (11) is enlarged. Brake device. The said control means (19) makes small the braking force with respect to the stroke of a brake operation element (11), when reaction force with respect to the stroke of a brake operation element (11) is made small. Brake device.

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