JP2020183174A - Electric brake control device - Google Patents

Abstract

To satisfactorily suppress dragging of a brake during turning of a vehicle.SOLUTION: An electric brake control device retracts a pressing member based on a value obtained by subtracting a detection value of a load sensor immediately before turning of a vehicle from a detection value of a load sensor during turning. Thereby, contact of a rotary disk to a friction pad can be prevented, and dragging can be satisfactorily suppressed.SELECTED DRAWING: Figure 6

Description

The present invention relates to an electric brake control device that controls an electric brake.

Patent Document 1 describes a hydraulic brake system that controls a clearance between a rotating disc and a friction pad based on a turning state of a vehicle. In the hydraulic brake system described in Patent Document 1, when the steering angle is large, the clearance is larger than when it is small, and when the vehicle speed is high, the clearance is smaller than when it is slow.

JP-A-2005-67247

An object of the present invention is to satisfactorily suppress the dragging of the brake while the vehicle is turning.

Means, actions and effects to solve problems

When the vehicle turns, the rotating disc tilts and comes into contact with the friction pad, which may cause dragging. Further, when the rotating disc is tilted and comes into contact with the friction pad, a load may be applied to the pressing member even when the disc brake is not operating. The load applied to the pressing member is smaller when the disc brake is in the operating state, but is larger when the tilt of the rotating disc is large than when it is small.
On the other hand, the load applied to the pressing member is detected by the load sensor, but the 0 point of the load sensor may shift due to temperature drift. Therefore, it is difficult to accurately detect the load caused by the inclination of the rotating disc, especially in the non-operating state of the disc brake.
On the other hand, in the electric brake control device according to the present invention, the pressing member is retracted based on the value obtained by subtracting the detected value of the load sensor immediately before turning of the vehicle from the detected value of the load sensor during turning. As a result, it becomes possible to prevent the rotating disc from coming into contact with the friction pad while the vehicle is turning, and dragging can be satisfactorily suppressed.

It is a figure which conceptually shows the electric brake system provided with the electric brake control device which is one Embodiment of this invention. It is sectional drawing of the electric brake included in the said electric brake system. It is a flowchart which shows the motor control program stored in the storage part of the electric brake control device. It is a flowchart which shows the target movement amount acquisition program stored in the storage part of the electric brake control device. It is a flowchart which shows a part of the said target movement amount acquisition program. It is a figure which shows the target clearance acquisition map stored in the said storage part. It is a figure which shows the clearance in the said electric brake. (a) It is a figure which shows the clearance in a straight running state of a vehicle. (b) It is a figure which shows the clearance in a turning state of a vehicle. It is a figure which shows the relationship between the inclination amount of a disc and a load in the said electric brake.

Hereinafter, an electric brake system including an electric brake control device according to an embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, the electric brake system is provided on each of the front, rear, left and right wheels of the vehicle, 8FL, 8FR, 8RL, 8RR, respectively, and the electric brakes 10FL, 10FR, 10RL, 10RR (hereinafter, electric) that suppress the rotation of the wheels are provided. When it is not necessary to distinguish the brakes and the like by the wheel positions, when they are collectively referred to, the description is made without adding FL, FR, RL, RR), the electric brake control device 12 and the like for controlling these electric brakes 10. including.

The electric brake 10 is a disc brake as an electric friction brake in this embodiment. The electric brake 10 has the same structure, and as shown in FIG. 2, a rotating disc (hereinafter, simply abbreviated as a disc) 16 as a brake rotating body that is rotated together with the wheel 8 and a disc 16 It includes a pair of friction engaging members 17 and 18 located on both sides, and a pressing device 20 that presses the friction engaging members 17 and 18 against the brake rotating body 16. The pressing device 20 includes an electric braking actuator 24 provided with an electric motor 22, a pressing member 26 that is moved by the braking actuator 24 in a direction parallel to the axis Lp, and a caliper 28. The axis Lp extends parallel to the rotation axis (not shown) of the brake rotating body 16.

The braking actuator 24 may include, for example, a speed reducer that reduces the rotational speed of the electric motor 22 in addition to the electric motor 22. The friction engaging members 17 and 18 include back plates 17r and 18r and friction pads 17p and 18p held by the back plates 17r and 18r, respectively.

The braking actuator 24 advances the pressing member 26 in a direction parallel to the axis Lp, and the caliper 28 is moved, whereby the pair of friction pads 17p and 18p are pressed against the disc 16. The rotation of the wheel 8 is suppressed by the frictional engagement between the friction surfaces 17f and 18f of the friction pads 17p and 18p and the friction surface 16f of the disc 16, and the electric brake 10 is operated.
Further, the electric brake 10 is provided with a rotation speed sensor 40 for detecting the rotation speed (rotational speed) of the electric motor 22, a load sensor 42 for detecting the load applied to the pressing member 26 (see FIG. 1), and the like.

As shown in FIG. 1, each electric motor 22 of the electric brake 10 is connected to a motor ECU (Electric Control Unit) 36 mainly composed of a computer via an inverter 34. An inverter 34, a rotation speed sensor 40, a load sensor 42, and the like are connected to the motor ECU 36, respectively.

In the motor ECU 36, the rotation angle of the electric motor 22 is acquired based on the rotation speed of the electric motor 22 detected by the rotation speed sensor 40, and the movement amount of the pressing member 26 and the like are acquired based on the rotation angle. Further, the load of the pressing member 26 detected by the load sensor 42 corresponds to the pressing force of the friction engaging members 17 and 18 against the brake rotating body 16.

The electric brake system is provided with a brake ECU 50 mainly composed of a computer. The brake ECU 50 includes an execution unit 50c, a storage unit 50m, an input / output unit 50i, etc., and the above-mentioned motor ECU 36 and the like are connected to the input / output unit 50i so as to be able to communicate with each other, and the wheel speed sensor 52 and the brake operation state. The acquisition device 54, the surrounding condition acquisition device 56, the steering angle sensor 58, and the like are connected. Further, the detected values of the rotation speed sensor 40 and the load sensor 42 are supplied from the motor ECU 36 to the brake ECU 50.

The wheel speed sensors 52 are provided on the front, rear, left, and right wheels 8, respectively, and detect the rotational speeds of the wheels 8. Based on the detected value of the wheel speed sensor 52, the traveling speed of the vehicle and the slip state of each of the wheels 8 can be acquired.
The brake operation state acquisition device 54 acquires the operation state of the brake operation member (not shown) by the driver. The operating state of the brake operating member by the driver can be expressed by the operating movement amount of the brake operating member, the operating force applied to the brake operating member, and the like.
The surrounding condition acquisition device 56 includes a camera, a radar device, an ultrasonic device, and the like, and acquires the surrounding conditions of the own vehicle, which is a vehicle equipped with the electric brake system. The surrounding condition acquisition device 56 detects an object, a lane marking, etc. around the own vehicle, acquires a relative positional relationship between the peripheral object, the lane marking, etc., or a road on which the own vehicle travels based on the lane marking. Get the state of curvature.
The steering angle sensor 58 may detect the steering angle of a steering operating member (for example, a steering wheel) (not shown), or may detect the steering angle of the steering wheel of the vehicle. The steering angle of the steering wheel can be obtained by detecting the operating state of a steering actuator (not shown).

The motor ECU 36 controls the electric motor 22 by controlling the inverter 34 based on a control command from the brake ECU 50. Further, by controlling the electric motor 22, the amount of movement of the pressing member 26 and the load applied to the pressing member 26 are controlled.
The motor control program represented by the flowchart of FIG. 3 is stored in the storage unit of the motor ECU 36. In step 111 (hereinafter, simply abbreviated as S111; the same applies to other steps), it is determined whether or not there is a control command from the brake ECU 50, and if the determination is YES, control is performed in S112. It is determined whether or not the command is a movement amount control command, and in S113, it is determined whether or not the control command is a load control command. If the determination in S112 is YES, the movement amount of the pressing member 26 acquired based on the detection value of the rotation speed sensor 40 in S114 becomes the target movement amount represented by the information supplied together with the movement amount control command. The electric motor 22 (braking actuator 24) is controlled so as to approach. If the determination in S113 is YES, in S115, the electric motor 22 is controlled so that the detected value of the load sensor 42 approaches the target load represented by the information supplied together with the load control command. If the determinations in S112 and 113 are NO, control is performed in S116 according to the control command.

The operation of the electric brake system configured as described above will be described.
In the brake ECU 50, the brake operation state acquired by the brake operation state acquisition device 54 and the slip state of each wheel 8 acquired based on the detection value of the wheel speed sensor 52 (hereinafter, at least these brake operation states and the slip state). There is a request to operate the electric brake 10 based on one or more of the relative positional relationships between the peripheral object and the own vehicle acquired by the peripheral condition acquisition device 56 (the state including one is referred to as the vehicle state). Whether or not it is determined.
Then, when it is determined that there is an operation request for the electric brake 10, the front, rear, left and right wheels 8 are provided based on at least one of the state of the vehicle and the relative positional relationship between the peripheral object and the own vehicle. The target load and the target clearance of the electric brake 10 are acquired, and the target movement amount of the pressing member 26 is acquired based on the change amount of the target clearance. The target clearance will be described later. In this embodiment, when the target load is smaller than the set load, a movement amount control command is output to the motor ECU 36 together with information indicating the target movement amount, and when the target load is equal to or more than the set load, the load control command is issued. Is output with the target load. When the control command is a movement amount control command, the determination of S112 is YES in the motor ECU 36, and in S114, the electric motor 22 is controlled so that the movement amount of the pressing member 26 approaches the target movement amount. When the control command is a load control command, the determination in S113 is YES, and in S115, the electric motor 22 is controlled so that the load approaches the target load. The friction surfaces 17p and 18p of the pair of friction pads 17p and 18p are frictionally engaged with the friction surfaces 16f of the disc 16, respectively, and the electric brake 10 is put into an operating state.

When the operation request of the electric brake 10 is eliminated, the pressing member 26 is retracted and the friction pads 17p and 18p are separated from the disc 16. The pressing member 26 is further retracted by a set amount from the time when the load detected by the load sensor 42 becomes equal to or less than the threshold value near 0 due to the retracting of the pressing member 26. In this case, the clearance between the friction surface 18p (17p) of the friction pad 18p (17p) and the friction surface 16f of the disc 16 is A {see FIG. 7A}, and the position of the pressing member 26 in this case is initially set. The position.

On the other hand, while the vehicle is turning, the disc 16 is tilted as shown by the alternate long and short dash line in FIG. Even when the electric brake 10 is inactive, the friction surface 16f of the disc 16 may come into contact with the friction surface 18f of the friction pads 17p and 18p (in the case of FIG. 2, the friction pad 18p), causing dragging. .. On the other hand, if the pressing member 26 is largely retracted, dragging can be avoided, but next, when the electric brake 10 is operated, a large delay occurs, which is not desirable.
Further, when the disc 16 is tilted and comes into contact with the friction pads 17p and 18p, a load is applied to the pressing member 26, and the detected value of the load sensor 42 becomes larger than 0. The detected value of the load sensor 42 due to the inclination of the disc 16 is smaller than that in the operating state of the electric brake 10, but when the positions of the friction pads 17p and 18p are the same, the amount of inclination of the disc 16 (for example, It can be represented by the inclination angle of the reference line Lc extending in the radial direction of the disc 16, or can be represented by the amount of movement Δ in the direction parallel to the axis Lp of the radial outer edge on the reference line Lc of the disc 16). When it is large, the detected value of the load sensor 42 is larger than when it is small. Therefore, as shown in FIG. 8, the amount of inclination of the disk 16 can be estimated based on the detected value of the load sensor 42.

However, the 0 point of the load sensor 42 may shift due to temperature drift, and in particular, when the electric brake 10 is not operating, the load applied to the pressing member 26 due to the inclination of the disc 16 can be accurately detected. Have difficulty. Therefore, it is difficult to accurately obtain the amount of inclination of the disc 16 based on the load.
Therefore, in this embodiment, when the electric brake 10 is in the non-operating state and the vehicle is traveling straight, the detection value W of the load sensor 42 is acquired every set time and stored in the storage unit 50 m. Remember. Then, the latest (immediately before turning) detection value stored in the storage unit 50m is set as the load reference value Wa, and the value obtained by subtracting the load reference value Wa from the detection value W of the load sensor 42 during turning of the vehicle is used. Based on this, the amount of inclination of the disk 16 is estimated.
In this way, by subtracting the load reference value Wa from the detected value W of the load sensor 42 during turning, the 0 point deviation due to the temperature drift can be offset, so that the subtracted value Wd (= W-Wa) is It can be considered that the load is applied to the pressing member 16 due to the inclination of the disc 16. Therefore, the amount of inclination of the disc 16 is estimated based on the subtracted value, and the target clearance of the pressing member 26 is acquired, so that the clearance during turning can be set to an appropriate size. Hereinafter, the subtracted value is referred to as a true load.

The clearance is the distance between the friction surface 16f of the disc 16 and the friction surface 18f (17f) of the friction pad 18p (17p) in the electric brake 10. Although it is difficult to accurately obtain this distance, when the operation of the electric brake 10 is released, the pressing member 26 is returned to the initial position, so that the clearance is as shown in FIG. 7A. It is considered to be in A.

However, even when the electric brake 10 is inactive, the disc 16 tilts when the vehicle turns. Further, due to thermal expansion of the disc 16, the distance between the friction surface 16f of the disc 16 and the friction surface 18f (17f) of the friction pad 18p (17p) changes. Therefore, the actual clearance is not always A in the non-operating state of the electric brake 10.
Therefore, in the present embodiment, the clearance means the friction surface 16f of the disc 16 and the friction surface 18f (17p) of the friction pad 18p (17p) when it is assumed that the vehicle is in a straight running state and is not affected by thermal expansion or the like. 17f) means the distance from. The target clearance is the target value of the clearance, and the target clearance correction value is the difference between the target clearance and the clearance A.

In this embodiment, the target clearance in the straight-ahead state of the vehicle is A in the non-operating state of the electric brake 10, but the target clearance is acquired based on the true load Wd during turning. Specifically, as shown in FIG. 6, the relationship between the true load Wd and the target clearance (target clearance correction value) is acquired and stored in advance. Then, the target clearance Cr is acquired based on the relationship (target clearance acquisition map) shown in FIG. 6 and the true load Wd. Then, the change amount of the target clearance Cr is obtained by subtracting the previous value Cr (n-1) from the current value Cr (n) of the target clearance, and the target movement amount of the pressing member 26 is obtained based on the change amount of the target clearance Cr. Is obtained. For example, when the target clearance acquired based on the true load Wd is (A + B) as shown in FIG. 7 (b), the amount of change in the target clearance Cr {Cr (n) −Cr (n-1). } Becomes B {= (A + B) -A}, and the target movement amount of the pressing member 26 is determined based on B.

The clearance is determined by the amount of retreat of the pressing member 26 and the movement of the caliper 28. Therefore, the change amount B {Cr (n) −Cr (n-1)} of the target clearance is not always the target movement amount of the pressing member 26, but the target movement amount is the change amount {Cr (n) of the target clearance. ) -Cr (n-1)}.

The information representing the target movement amount acquired in this way is supplied to the motor ECU 36 together with the movement amount control command. In the motor ECU 36, the determination in S112 becomes YES, and in S114, the electric motor 22 is controlled so that the movement amount of the pressing member 26 approaches the target movement amount. As described above, even if the pressing member 26 is moved by the target movement amount, the distance between the friction surface 16f of the disc 16 and the friction surface 18f of the friction pad 18p is the target clearance (A + B). Is not always.

Further, as shown in FIG. 6, an upper limit value is set for the target clearance. Even if the true load Wd becomes larger than the set value Wds, the target clearance is maintained at the upper limit value Crth. By setting the upper limit value in the target clearance in this way, it is possible to prevent the pressing member 26 from retreating too much, and then to suppress the delay in effectiveness when the operation request of the electric brake 10 is issued.

In the operating state of the electric brake 10, the friction pads 17p and 18p are in a compressed state, and the target clearance is smaller than A and acquired as a negative value smaller than 0. Similarly, the amount of change in the target clearance is acquired as the target movement amount, but when the load is increased, the target movement amount becomes the target advance amount, and when the load is decreased, it becomes the target backward amount.

In the brake ECU 50, the target movement amount acquisition program represented by the flowchart of FIG. 4 is executed at predetermined set times.
In step 1 (hereinafter abbreviated as S1; the same applies to other steps), the detected values of the wheel speed sensor 52, the brake operation state acquisition device 54, the surrounding condition acquisition device 56, the steering angle sensor 58, and the load sensor 42. Etc. are acquired, and in S2, it is determined whether or not the electric brakes 10 provided on the front, rear, left, and right wheels 8 are in the operating state. If the determination is YES, the target clearance and the target load are acquired in S3 based on the state of the vehicle, the relative positional relationship between the peripheral object and the own vehicle, and the like, and in S4, based on the amount of change in the target clearance. The target movement amount or target load of the pressing member 26 acquired is output to the motor ECU 36 together with the control command.

On the other hand, in the non-operating state of the electric brake 10, the determination of S2 is NO. In S5, it is determined whether or not the vehicle is turning. For example, when the absolute value of the detection value of the rudder angle sensor 58 is equal to or more than the set value that can be regarded as turning, or when the peripheral condition acquisition device 56 acquires that the road shape is curved by the set curvature or more. Etc., it can be determined that the vehicle is turning. When the determination in S5 is NO, the value of the load W acquired in S1 is stored as the load reference value Wa in S6. While the vehicle is traveling straight, the load reference value Wa is overwritten and the latest value is stored in the storage unit 50 m.

Next, in S7, the turning determination flag is turned off, and in S8, the target clearance is set to A (the target clearance correction value is 0). Since the target clearance is always set to A in the straight-ahead state of the vehicle, the amount of change in the target clearance {Cr (n) -Cr (n-1)} is set to 0 and the target movement amount is set to 0 in S9. Often.

If the determination in S5 is YES, the turning determination flag is turned ON in S10, the target movement amount is acquired in S11, and the target movement amount is output to the motor ECU 36. An example of execution of S11 is shown in the flowchart of FIG.
In S21, the true load Wd is acquired by subtracting the load reference value Wa stored in the storage unit 50 m from the load W detected during turning. In S22, it is determined whether or not the true load Wd is larger than the threshold value Wdm. When the true load Wd is smaller than the threshold value Wdm, the amount of inclination of the disc 16 is small, so that it is considered that the need to retract the pressing member 26 is low. Therefore, when the determination in S22 is NO, the target clearance Cr (n) is set to A in S23. In S24, the change amount of the target clearance {Cr (n) −Cr (n-1)} is acquired, the target movement amount is acquired, and is output to the motor ECU 36. In this case, the target movement amount is often set to 0.

On the other hand, when the determination in S22 is YES, the target clearance Cr is acquired in S25 based on the target clearance acquisition map shown in FIG. 6 and the true load Wd, and in S26, the target clearance is set. The amount of change {Cr (n) −Cr (n-1)} is acquired, the target retreat amount of the pressing member 26 is acquired based on the amount of change in the target clearance, and is output to the motor ECU 36 together with the movement amount control command.
In the motor ECU 36, the determination in S112 is YES, and in S114, the electric motor 22 is controlled so that the retreat amount of the pressing member 26 acquired based on the detection value of the rotation speed sensor 40 becomes the target retreat amount.

The target clearance is A when the vehicle changes from a turning state to a straight running state, or when the true load Wd becomes smaller than the threshold value Wdmmin from a state of the threshold value Wdm or more. In S9 or S24, the target movement amount becomes a negative value (advance amount of the pressing member 26). The pressing member 26 is advanced by the motor ECU 36 (S114).

As described above, in the present embodiment, when the electric brake 10 is in the non-operating state and the vehicle is in the turning state, the pressing member 26 is retracted based on the true load Wd. As a result, the clearance can be set to an appropriate size. Next, the dragging can be satisfactorily suppressed while suppressing the delay in effectiveness when the electric brake 10 is operated.
Further, since the target clearance is provided with an upper limit value, it is possible to avoid the pressing member 26 from retreating too much, and even if there is a request to operate the electric brake 10 during turning, the operation delay can be satisfactorily suppressed.

As described above, in this embodiment, the electric brake control device is based on the brake ECU 50, the motor ECU 36, the wheel speed sensor 52, the brake operation state acquisition device 54, the surrounding environment acquisition device 56, the steering angle sensor 58, the rotation speed sensor 40, the load sensor, and the like. 12 is configured. Further, the storage unit 50m of the brake ECU 50 of the electric brake control device 12 corresponds to the load storage unit, and a portion for storing and executing S11 of the brake ECU 50, a portion for storing S112 and 114 of the motor ECU 36, and a portion for executing. The pressing member retracting portion is configured by the portion for storing the target clearance acquisition map of FIG.

It is not indispensable to acquire the true load Wd, and the target clearance can be acquired based on the detected value of the load sensor 42 during turning.
In addition, the structure of the electric brake 10 does not matter, and the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art.

10: Electric brake 12: Electric brake control device 16: Disc 22: Electric motor 24: Braking actuator 26: Pressing member 34: Inverter 36: Motor ECU 42: Load sensor 50: Brake ECU 58: Steering angle sensor

Claimable invention

The patentable inventions are described in the following sections.
(1) An electric brake control device that is provided on each of a plurality of wheels of a vehicle and controls an electric brake that suppresses rotation of the wheels.
Each of the electric brakes includes a pair of friction engaging members located on both sides of a rotating disc that can rotate with the wheels, and a pressing device that presses the pair of friction engaging members against the rotating disc. However, it is provided with a braking actuator and a pressing member that is moved forward and backward by the braking actuator.
The electric brake control device
A load sensor that detects the load applied to the pressing member, and
An electric brake control device including a pressing member retracting portion that retracts the pressing member based on a detection value of the load sensor when the vehicle is turning and the electric brake is in a non-operating state.
As described in item (2), it is not indispensable to return the pressing member based on the value obtained by subtracting the detected value of the load sensor immediately before turning from the detected value of the load sensor during turning of the vehicle, and the load during turning. It is also possible to allow the pressing member to be returned based on the value of the sensor.

(2) The electric brake control device includes a load storage unit that stores a detection value of the load sensor when the vehicle is not turning.
The pressing member retracts the pressing member based on a value obtained by subtracting the detected value of the load sensor stored in the storage unit immediately before the turning of the vehicle from the detected value of the load sensor while the vehicle is turning. The electric brake control device according to item (1).

(3) The electric brake control device according to item (2), wherein the pressing member retracting portion retracts the pressing member more rearward than when the subtracted value is large.

(4) The electric brake control device includes a disc tilt amount estimation unit that estimates the tilt amount of the rotating disc based on the subtracted value.
Item (2) or (3) that the pressing member retracting portion retracts the pressing member to a position further rearward than when the tilt amount of the rotating disc estimated by the disc tilt amount estimating unit is large. The electric brake control device described in.
The amount of inclination of the rotating disk can be expressed by the inclination angle of the reference line extending in the radial direction of the rotating disk, the amount of movement of the outer edge in the radial direction of the rotating disk in the axial direction, and the like.

(5) Item (2) to (4) that includes a retreat limiting portion that limits the retreating amount of the pressing member to the set retreating amount even if the subtracted value becomes larger than the set value. The electric brake control device according to any one of the above.

Claims (1)

An electric brake control device that is provided on each of a plurality of wheels of a vehicle and controls an electric brake that suppresses the rotation of the wheels.
Each of the electric brakes includes a pair of friction engaging members located on both sides of a rotating disc that can rotate with the wheels, and a pressing device that presses the pair of friction engaging members against the rotating disc. However, a braking actuator equipped with an electric motor and a pressing member that is moved forward and backward by the braking actuator are provided.
The electric brake control device
A load sensor that detects the load applied to the pressing member, and
A load storage unit that stores the detected value of the load sensor and
When the electric brake is in the non-operating state, the value obtained by subtracting the detected value of the load sensor stored in the load storage unit immediately before the turning of the vehicle from the detected value of the load sensor while the vehicle is turning. An electric brake control device including a pressing member retracting portion that retracts the pressing member based on the above.

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