JP2000055094A - Electrically driven brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrically driven brake device capable of precisely detecting a zero position, and highly convenient. SOLUTION: During resting, if no braking is made, a position of an inner pad upon application of a current having a predetermined value to a motor (YES at step 13) is detected, and a reference position of the brake pad is determined in accordance with detected data. Further, a position returned from the reference position by a predetermined distance is set as a zero position at which the brake pad starts making contact with brake rotor. During no braking, since the reference position of the brake pad for calculating the zero position is obtained, variation in the detected value in association with braking, does not cause any affection, and accordingly, not only the reference position of the brake pad but also the zero position can be precisely detected. Accordingly, it is possible to ensure a precise pad clearance, and as well to prevent occurrence of a drag phenomenon of the brake bad, thereby it is possible to enhance the initial responsiveness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric brake device used for a vehicle.

[0002]

2. Description of the Related Art As an example of a conventional electric brake device,
There is one disclosed in Japanese Patent Publication No. 8-5373. In this electric brake device, a brake pad is pressed against a brake rotor via a force transmission mechanism by an operating force of a motor to generate a braking force. In this case, the current of the motor is monitored by the control device, and when an increase in the current due to the generation of the load on the brake shoe is detected, a reference motor position is set, and then this reference motor is applied to apply a desired clamping force. The number of rotations of the motor is counted from the position, and at the time of releasing the braking force, the number of rotations of the motor is counted back above the reference in order to ensure complete release of the brake.

[0003]

By the way, in the electric brake device, it is desired to accurately detect the zero point position where the brake pad starts to contact the brake rotor in order to ensure good braking. ing. However, in the above-described prior art, as described above, the zero point position (reference motor position) is set (detected) based on the data detected during normal braking, and the detection accuracy of the zero point position is poor. Become. That is, the increase in the current value due to the generation of the load on the brake shoe depends on the speed at which the brake pad operating portion of the force transmission mechanism is sent (that is, how the brake pedal is depressed), and the detection accuracy of the zero point position is inferior to this extent. Become.

As described above, when the detection accuracy of the zero point position becomes poor, (1) for example, the initial position [the motor rotation speed is set to 0
If the point position (the position returned beyond the reference motor position) is set to a small value, dragging will occur, and if the initial position is set to a large value, the initial responsiveness will decrease, or (2) each wheel The timing at which the braking force is generated differs, or (3) the vehicle behavior becomes unstable during braking. For this reason, the conventional technology described above has not been able to adequately meet the above-mentioned demands.

[0005] Another conventional example for setting the zero point position is disclosed in Japanese Patent Application Laid-Open No. 3-45462.
This device obtains the position of the brake pad when the motor is driven by depressing the brake pedal, and when a full brake state is detected, returns the position returned by a specified amount from the position of the brake pad to the initial position (point 0 position). ). However, stepping on the brake pedal until a full brake state is rare in normal use, and there is almost no chance of detecting (updating) the zero point position with this device, and accordingly, this device is inconvenient. It has become something.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a highly convenient electric brake device which can accurately detect a zero point position.

[0007]

According to the first aspect of the present invention,
An electric brake device for a vehicle that generates a braking force by pressing a brake pad against a brake rotor via a force transmission mechanism by an operating force of an electric actuator, and supplies a predetermined amount of current when the vehicle is stopped and non-braking. The position of the brake pad when it was supplied to the electric actuator and the brake pad was pressed against the brake rotor was detected, the reference position of the brake pad was determined based on the detected data, and the reference position was returned by a predetermined length. The position is a zero point position of the brake pad.

According to a second aspect of the present invention, in the configuration of the first aspect, the position of the brake pad is detected a plurality of times.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electric brake device according to an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, an electric brake device 1 includes four disc brakes 2 provided corresponding to four wheels of a vehicle, and a brake pedal 3.
A pedaling force sensor 4 for detecting an operation amount of the brake pedal, a master cylinder 5 for converting an operation amount of the brake pedal 3 into a hydraulic pressure,
Control is performed based on a power supply unit 7 capable of adjusting a current value to be supplied to a motor (electric actuator) 6 provided in the disc brake 2 and a detection signal (pedal force signal) of the pedal force sensor 4 or a calculation content when step S6 described later is executed. Generate a signal K,
The control device is generally constituted by a controller 8 for supplying a current having a magnitude based on the control signal K (hereinafter, referred to as a motor current I) from the power supply unit 7 to the motor 6, and a memory 9 connected to the controller 8.

As shown in FIG. 2, the disc brake 2 includes a caliper 12 movably supported by a carrier 11 provided on a fixed portion of an automobile, and a ball screw mechanism (force transmission mechanism) 13 housed in the caliper 12. And a motor 6 having a rotor (hereinafter referred to as a motor rotor) 15 fitted to a nut 14 of the ball screw mechanism 13, and the brake rotor 18 pressed by the axial movement of the screw shaft 17 of the ball screw mechanism 13. A pair of brake pads 19 (hereinafter, referred to as
1 is called an inner pad 19a and the left one is called an outer pad 19b. ) And a lid 21 for closing one opening (right side in FIG. 1) of a later-described hollow portion 20 of the caliper 12. The inner pad 19a and the outer pad 19b are arranged inside and outside the vehicle body, respectively, and supported by the carrier 11 so as to be movable in the axial direction of the brake rotor 18.

The screw shaft 17 of the disc brake 2 is moved by the motor 6 or the action of pressure oil described later.
2 moves to the left to press the inner pad 19a against the brake rotor 18, and the caliper 12 moves to the right in FIG. 2 with respect to the carrier 11 by the reaction, and the claw 22 of the caliper 12 pushes the outer pad 19b to the brake rotor 18. , Thereby generating a braking force.

The caliper 12 has a hollow portion 20 that is open at both ends (the left and right sides in FIG. 2). A motor housing portion 23 for housing the motor 6 in the hollow portion 20 is connected to the motor housing portion 23 by bolts (not shown) or the like. Brake rotor 1 coupled to the means
The claw portion 22 extending to the outer pad 19b side beyond
The opening of one side (the right side in FIG. 2) of the hollow portion 20 is closed by the lid 21 as described above.

The lid 21 is connected to the lid main body 24 and one of the hollow portions 20 (see FIG. 2) together with the lid main body 24.
And a cover main body support portion 25 for closing the opening (right side). The lid body 24 includes a cylinder body 28 having a hydraulic chamber 27 communicating with the master cylinder 5 via a port 26, a piston 29 slidably housed in the hydraulic chamber 27 of the cylinder body 28, and a cylinder body 28. A detent part 30 which is extended and has a space having substantially the same inner diameter as the hydraulic chamber 27, a flange part 31 formed on the outer peripheral side of the cylinder main body 28 and fixed to the lid main body support part 25,
It is equipped with. The supply of the pressure oil to the hydraulic chamber 27 causes the piston 29 to move to
2, the screw shaft 17 is pressed to the left in FIG. 2 to generate a braking force.

The ball screw mechanism 13 includes the screw shaft 17
And the nut 14 for guiding the screw shaft 17 in the axial direction.
The motor rotor 15 is fitted to the nut 14 as described above. The nut 14 on which the motor rotor 15 is fitted is connected to the caliper 1 via a bearing 33.
2 and thus rotatably provided in the motor housing 23. A bearing retainer 35 is attached to the nut 14 by a bolt 34. The bearing 33 has an inner ring side held by a bearing retainer 35 and a nut 14, and an outer ring side held by a caliper 12. And
The nut 14 is restricted from moving in the axial direction by the bearing 33, and the motor rotor 15 and the nut 14 are rotated in a state where the movement in the axial direction is restricted, so that the rotation is stopped by the detent plate 32. Screw shaft 1
7 can move in the axial direction.

One end of the screw shaft 17 (the brake pad 19
On the (side) side, a pressure plate 36 that is in contact with the inner pad 19a is fixed by bolts (not numbered). Screw shaft 17
The other end (the end of the screw shaft 17 opposite to the brake pad 19) is secured to the rotation preventing plate 32 by bolts (omitted by reference numerals).

The motor 6 comprises a stator 37 having a predetermined width fitted into the hollow portion 20 of the motor housing 23, and the motor rotor 15 arranged in the stator 37.
The motor rotor 15 is arranged at the center of the stator 37 in the width direction. The motor rotor 15 includes a sleeve 38 having a predetermined width to be fitted to the nut 14, and a plurality of magnets 39 arranged circumferentially on the outer peripheral side of the sleeve 38 and fixed to the sleeve 38. Stator 3
7, a plurality of coils (reference numerals are omitted) are arranged in the circumferential direction.

The motor 6 is connected to the controller 8 via a motor wire 40, and a control signal K
, The respective coils are selectively energized, and thereby the motor rotor 15 and thus the nut 14 are rotated by the magnetic force generated between the coils and the magnet 39. The rotation of the nut 14 causes the screw shaft 17 to move in the axial direction (leftward in FIG. 2 [braking force generation direction], rightward in FIG. 2 [braking force release direction]) as described later. . Then, the motor rotor 15 (nut 1
There is a certain correspondence between the amount of rotation of 4) and the amount of movement of the screw shaft 17, that is, the position of the screw shaft 17 (and the magnitude of the braking force and the amount of wear of the brake pad 19, etc.).

An encoder 41 for detecting the rotational position of the motor rotor 15 (nut 14) is provided near the bearing 33. The encoder 41 includes a rotary disk 42 having a slit (not shown) attached to the nut 14 by a bolt 34 and the caliper 12
And a detecting portion 45 fixed to the motor housing portion 23 via an encoder mounting plate 44 so as to be located in a concave portion 43 formed in a portion where the claw portion 22 is attached to the motor housing portion 23. The rotating disk 42 is
Of the nut 1 without being affected by the reciprocation of the pressing plate 36 (screw shaft 17).
4 to rotate with.

A cover 46 made of a flexible material is provided between the pressing plate 36 and the motor housing 23.
The encoder 41 and the nut 14 are protected from dust and the like. The cover 46 has a substantially ring shape and an inner circumferential portion is formed in an annular groove provided on the outer circumferential side of the pressing plate 36 (reference numeral omitted).
And the outer peripheral side portion is held in the motor housing 23 by bolts 47. The cover 46 is made of a flexible material, and can follow the forward and backward movements of the pressure plate 36 and the nut 14.

The encoder 41 detects the rotational position of the nut 14 and thus the motor rotor 15 based on the number of times light is transmitted through the slit by the detector 45, and inputs this detection signal to the controller 8 via an encoder wire 48. I am trying to do it. The controller 8 performs feedback control or the like using the detection signal to
While grasping the position, the motor 16 is controlled to generate a desired braking force.

The controller 8 generates a control signal K indicating the magnitude of the treading force signal (detection signal) from the treading force sensor 4, and outputs the control signal K via the power supply unit 7 in accordance with the content of the control signal K and the magnitude of the treading force signal. To operate the motor 6 to rotate the motor rotor 15 (the nut 14).
(Nut 14), the length corresponding to the rotation amount of the screw shaft 17
To generate a braking force. Further, the controller 8 controls the control signal K based on the treading force signal from the treading force sensor 4 in a zero point detection subroutine in step S6 described later.
A control signal K is generated separately from the power supply
The current I is supplied to the motor to detect a zero point position (a position at which the inner pad 19a starts to contact the brake rotor 18), as described later, so as to suppress the occurrence of dragging and the like. Regarding the setting of the zero point position, FIG.
A description will be given based on FIG.

In FIG. 3, the controller 8 first
It is determined whether or not an operation of detecting a zero point position (hereinafter, appropriately referred to as zero point detection) is required (step S1). If it is determined that the zero point detection operation is not necessary (NO in step S1), it is determined in step S2 whether or not braking is being performed. If the braking is being performed (determined as YES in step S2), it is determined that a zero-point detection operation is necessary in step S3, for example, a flag indicating this is set, and the process returns to the main routine (not shown) of the controller 8. The flag is used for the determination in step S1.

If YES is determined in step S1 (a zero-point detection operation is necessary), it is determined whether or not braking is being performed (step S4). If it is determined as NO (not braking) in step S4, it is determined whether or not the vehicle is stopped based on a signal of a wheel speed sensor (not shown) (step S5). Step S5
If YES is determined (the vehicle is stopped), a zero point detection subroutine is executed (step S6), and it is treated that the zero point has been detected (step S7), and the process returns to the main routine (not shown) of the controller 8. Stopped (YE in step S5
At the time of non-braking of S) (NO at step S4), the zero-point detection subroutine is executed (step S6).
As a result, it is easy to make the thrust of the inner pad 19a to the brake rotor 18 constant, and to enable the driver to perform zero point detection without operating the brake pedal. The convenience of point detection can be improved.

When NO is determined in step S2 (braking is not performed), when YES is determined in step S4 (braking is in progress), or when NO is determined in step S5 (the vehicle is not stopped), The process returns to the main routine (not shown) of the controller 8. As described above, the vehicle is stopped (step S5
If YES) and non-braking (NO in step S4),
The zero point detection subroutine (step S6) is executed.

In the zero point detection subroutine (step S6), as shown in FIG. 4, it is first determined whether or not the count value E is "6" (step S11). The count value E has been initialized to 0 in advance by, for example, the first subroutine when the ignition switch is turned on. If NO is determined in step S11 (the count value E has not reached "6"), the motor 6 is energized (the control signal K is set based on a signal set separately from the detection signal of the pedaling force sensor 4).
The screw shaft 17 (pressing plate 36) is advanced at a specified speed to press the inner brake pad 19 and the outer pad 19b against the brake rotor 18 (step S12). At this time, the current I supplied to the motor 6 is
(Shown by the symbol I) is equal to a predetermined threshold value _Th (the brake pad 19 for the brake rotor 18).
Is determined (step S13).

[0026] (a point C where the current I reaches the threshold T _h,. Showing the position corresponding to the point C in C ₀₎ YES and determines in step S13 and, the inner pad 19a brake rotor 18 Is detected (indicated by the position F / B value indicated by the dotted line in FIG. 5), and this detected value is stored in the memory 9 as a preliminary reference value (step S1).
Four ). In this case, the preliminary reference value is stored corresponding to step S17 described later. The position detection is performed a plurality of times (five times in the present embodiment) as described later, and the obtained plurality (5
) Are stored in the memory 9.

Subsequent to step S14, the current I to the motor 6 is reduced to a small value [I < _Th (the portion where the slope of the current I in the upper column of FIG. 5 is negative and the portion where I ≦ 0 in FIG. 5)] , Screw shaft 17
(Pressing plate 36) is retracted and the inner brake pad 19
The outer pad 19b is separated from the brake rotor 18 (step S15), the count value E is incremented by "1" (step S16), and the process returns to step S11.

Here, the correspondence between the position of the brake pad 19 with respect to the brake rotor 18 and the current I will be described with reference to FIG. The brake pad 19 (the inner pad 19a and the outer pad 19b) is
(When the current I starts to rise, this current rising point is indicated by A in FIG. 5 and a position corresponding to the current rising point A is indicated by A ₀ ), the brake pad 19 and the caliper 12 It will deform and store a kind of spring force,
Even if the current I is positive, if the value is small, the screw shaft 17 (the pressure plate 36) is retracted by the stored spring force. The position detection is performed a plurality of times, as described above. In the first detection operation, the current I is greatly increased due to the influence of the brake pad 19 and the back plate (pad shim) provided on the brake pad 19. not increased in linearly from the value of the time a to the threshold value T _h, in the vicinity of the current rise time a rise rate is small,
A predetermined time point (a time point corresponding to a target 0-point position, which is indicated by reference numeral B in FIG. 5).
Indicated by ₀ . ) Shows that the rate of increase is large.

Further, in the position detecting operation of the second and subsequent of the position detection operation of a plurality of times, the current value as shown in FIG. 5 is linearly increased from the current value of the current rise time A to the threshold value T _h And does not have a bending point as in the time point B generated in the first position detection operation.
In order to be distinguished from the current rise time A in the first position detection operation, the current rise time in the second and subsequent position detection operations will be indicated by a symbol D, and the position corresponding to the current rise time D (shown by a dotted line). position F / B) is called D _0. In this embodiment, to previously obtain the position detected by the current supply position D ₀ and threshold T _h is detected by the current rise time D in advance by experiment, the difference between both the position data as a specified value It is stored in the memory 9. The specified value stored in the memory 9 is used as data to be subtracted from the reference position data (value) for setting the zero point position in step S17 described later.

If it is determined in step S11 that the count value E has reached 6, the count value E is reset, the zero point position is set (step S17), and the count value E is returned to 0 (step S18). Returning to the flowchart of FIG.

Until it is determined in step S11 that the count value E has reached 6, the processes in steps S12 to S16 are performed a total of five times, and the memory 9 stores five preliminary reference values. Then, in step S17 after YES is determined in step S11, an average value is obtained for three preliminary reference values, excluding the maximum value and the minimum value, of the five preliminary reference values, and this average value is used as a reference value for the inner pad 19a. The value indicates the position (reference position data). Then, a value obtained by subtracting the specified value stored in the memory 9 from the reference position data (value) is set as a value indicating the zero point position,
It is used as a position reference when a braking force is generated.

The disc brake 2 is provided with a motor failure detecting means (not shown). And
While the hydraulic pressure is shut off in a normal state, if the failure of the motor 6 (the motor 6 does not operate) is detected by the motor failure detecting means, the master cylinder 5 responds to the depression force of the brake pedal 3 instead of the operation of the motor 6. The pressure oil is supplied to the hydraulic chamber 27 through the port 26.

In the electric brake device configured as described above, when the vehicle is stopped (YES in step S5) and is not braking (NO in step S4), a current of a predetermined magnitude is supplied to the motor 6 (step S13). (YES), the position of the inner pad 4 when the power is supplied is detected, and the reference position of the brake pad is determined based on the detected data. Further, a position returned by a predetermined length from the reference position is set as a zero point position at which the brake pad starts to contact the brake rotor.

As described above, since the reference position of the brake pad for calculating the zero point position is obtained during non-braking, the influence of the change in the detected value due to the braking is eliminated, and the reference position of the brake pad, that is, 0, is obtained. The point position can be detected with high accuracy. Therefore, accurate pad clearance can be ensured, and a drag phenomenon of the inner pad 19a or the outer pad 19b does not occur, and the initial responsiveness can be improved. In addition, by setting the zero point position with high accuracy as described above, it is possible to match the timing of generation of the braking force for each wheel, and the vehicle behavior during braking can be stabilized.

In the apparatus disclosed in Japanese Patent Application Laid-Open No. 3-45462, full-brake operation that requires very few actual operations is required in order to perform zero-point detection. In contrast to this, in the present embodiment, since zero point detection is performed during non-braking while the vehicle is stopped as described above, there are many opportunities to perform zero point detection. Will be higher. Further, since the zero point detection is performed during non-braking, the operation of the driver becomes unnecessary, and the zero point detection can be performed without the driver noticing.

In this embodiment, as described above, the processing of steps S12 to S16 (position detecting operation) is performed a total of five times until it is determined in step S11 that the count value E has reached 6. Therefore, the detection accuracy is improved. In this embodiment, the case where the position detection operation is performed five times is described as an example. However, the present invention is not limited to this, and the position detection operation may be performed one to four times or six or more times.

[0037]

According to the first aspect of the present invention, when no braking is performed,
Since the reference position of the brake pad for calculating the point position is obtained, the influence of the change of the detection value due to the braking is eliminated, and the reference position of the brake pad, that is, the zero point position can be detected with high accuracy. Therefore, accurate pad clearance can be ensured, and a drag phenomenon of the brake pad does not occur, and an initial response can be improved. In addition, by setting the zero point position with high accuracy, it is possible to match the timing of generating the braking force for each wheel, and to stabilize the vehicle behavior during braking. The invention according to claim 2 is
Since the position detection of the brake pad is performed a plurality of times, the detection accuracy of the reference position of the brake pad is improved, and the setting accuracy of the zero point position of the brake pad can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an electric brake device according to an embodiment of the present invention.

FIG. 2 is a side sectional view showing a disc brake of the electric brake device of FIG. 1;

FIG. 3 is a flowchart showing control contents of a controller of FIG. 1;

FIG. 4 is a flowchart showing a zero point detection subroutine of FIG. 3;

FIG. 5 is a time chart showing a correspondence relationship between a position of a brake pad with respect to a brake rotor and a motor current.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric brake device 4 Tread force sensor 6 Motor 8 Controller 12 Caliper 13 Ball screw mechanism 17 Screw shaft 18 Brake rotor 19 Brake pad

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (2)

[Claims] 1. An electric brake device for a vehicle that generates a braking force by pressing a brake pad against a brake rotor via a force transmission mechanism by an operating force of an electric actuator, wherein the predetermined braking force is applied when the vehicle is stopped and non-braking. A current of a magnitude is supplied to the electric actuator to detect a position of the brake pad when the brake pad is pressed against the brake rotor, and a reference position of the brake pad is determined based on the detected data. An electric brake device wherein a position returned by a predetermined length is set to a zero point position of a brake pad. 2. The electric brake device according to claim 1, wherein the position of the brake pad is detected a plurality of times.