JP3726443B2 - Electric brake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure a stable brake feeling irrespective of any flexural value variation of a brake pad in this dynamoelectric braking device. SOLUTION: When an extent of abrasion loss in a brake pad grows larger, a flexural value in this brake pad decreases, and thereby braking force to the same brake manipulated variable is enlarged, so that in the case where any wear in the brake pad is detected, the specified relation between the brake manipulated variable and the driving value of a dynamoelectric means is changed so as to have this dynamoelectric means driven by the driving value being smaller than that of the dynamoelectric means to the same brake manipulated variable as before the pad wear detection, on the basis of pad abrasion loss detected.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric brake device that obtains braking by pressing a brake pad against a disc rotor by an electric motor.
[0002]
[Prior art]
Most conventional vehicle brake devices are hydraulic, and include a cylinder and a piston. During braking, hydraulic pressure is introduced into the cylinder, and the hydraulic pressure is used to press the piston and press the brake pad against the disc rotor for braking. It was. When releasing the brake, the piston is returned using the elastic force of a rubber piston seal provided between the piston and the cylinder to prevent leakage of brake fluid.
[0003]
However, it is difficult for the piston return mechanism using the rubber elastic force of the piston seal to obtain an accurate piston return amount corresponding to the hydraulic pressure from the instability of the rubber friction force and the limit of the rubber elastic force. As a result, the brake pads are not completely separated from the disk rotor, and there is a risk that the brake will be dragged.
[0004]
On the other hand, in order to secure an accurate return amount of the brake pad and prevent dragging of the brake, an electric brake device in which the brake pad is pressed and separated from the disk rotor by an electric motor has been developed.
[0005]
For example, Japanese Patent Laid-Open No. 3-45462 discloses an electric unit that presses and separates a brake pad supported on the vehicle body against a disc rotor that rotates with a wheel in response to an operation of a brake operation unit by a driver. An electric brake that includes a brake operation amount detection unit that detects an operation amount of the brake operation unit, and that drives and controls the electric unit so that the detected brake operation amount and the drive amount of the electric unit have a predetermined relationship. An apparatus is disclosed. That is, when the stroke from the position of the brake pad when the brake pedal is released (the position where the gap between the disc rotor and the brake pad becomes a predetermined value) to the position of the brake pad in the full brake state is defined as “full stroke” The pad position is controlled so that the position where the full stroke is returned from the position of the brake pad in the full brake state becomes the pad position when the brake pedal is released, thereby ensuring an appropriate return amount. Further, during braking, the electric motor is driven so that the brake pedal stroke and the rotation angle of the electric motor have a predetermined relationship.
[0006]
[Problems to be solved by the invention]
However, when the electric motor is driven so that the pedal stroke and the rotation angle of the electric motor always have a predetermined relationship as in the conventional electric brake device, if the brake pad is worn and thinned, There is a problem that the brake pad is less bent at the time of pressurization, and the amount of absorption of the piston stroke due to the bend is reduced, so that the braking pressure of the brake pad with respect to the disc rotor increases with respect to the drive amount of the same electric means.
[0007]
That is, with the wear of the brake pad, it becomes a sensitive feeling for the same brake operation.
[0008]
The present invention has been made in view of the above-described conventional problems, and it is an object of the present invention to provide an electric brake device capable of maintaining a stable brake feeling regardless of a deflection amount change due to wear of a brake pad. To do.
[0009]
[Means for Solving the Problems]
As shown in FIG. 1, the present invention includes an electric means for pressing and separating a brake pad supported on the vehicle body side with respect to a disk rotor that rotates together with a wheel in response to an operation of a brake operation means by a driver. A brake operation amount detection means for detecting an operation amount of the brake operation means, and the drive amount of the electric means increases as the brake operation amount for pressing the brake pad detected by the brake operation amount detection means increases. In the electric brake device for driving and controlling the electric means, the pad wear detecting means for detecting the wear of the brake pad, and when the brake pad wear is detected, the brake pad is pressed against the disc rotor. wherein as driving of the electric unit is reduced for the same of the brake operation amount when to be, the And means for changing the drive amount of the electric means for rake operation amount is obtained by solving the problems by providing a.
[0010]
According to the present invention, when the wear of the brake pad is detected, the predetermined relationship is changed so that the drive amount of the electric means decreases with respect to the same brake operation amount as before the driver detects the wear of the pad. Therefore, even if the amount of bending of the brake pad decreases due to wear, the braking force does not increase, and even when the same amount of brake operation as before the amount of bending changes is applied, a stable brake feeling can be achieved. Can be maintained.
[0011]
Here, when the brake operation means is a brake pedal, the brake operation amount indicates a pressing force for pressing a button or the like when the brake operation means is a manual button, such as a pedaling force or a pedal stroke.
[0012]
When the brake operation means is a brake pedal, and the brake operation amount detected by the brake operation amount detection means is a pedaling force for stepping on the brake pedal, the driver's intention to brake is most accurately actualized. Therefore, it is possible to obtain a good brake feeling.
[0013]
Further, the pad wear detection means comprises a pressure sensor for detecting the pressure applied to the brake pad and a drive amount detection means for detecting the drive amount of the electric means. From the drive amount of the electric means at the initial stage of brake operation. It is good also as a structure which detects pad wear. As a result, when the brake pad wears, the brake pad wear can be accurately detected quantitatively by utilizing the change in the driving amount of the electric means at the initial stage of braking (at the start of braking) from the change in thickness. it can. Further, based on this, as the detected pad wear amount increases, the driving amount of the electric means with respect to the brake operation amount for pressing the brake pad is decreased, so that a more stable brake feeling is maintained. To be able to.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0015]
FIG. 2 is a schematic configuration diagram showing the overall configuration of the electric brake device to which the present invention is applied, in which the motor drive disk brake 14 is enlarged and shown in FIG. 3 is a sectional view taken along line IV-IV in FIG. 3, FIG. 5 is a sectional view taken along line VV in FIG. 4, and FIG. 6 is a sectional view taken along line VI-VI.
[0016]
The brake pedal 2 is provided with a pedaling force sensor 4 for detecting a pedaling force when the driver steps on the brake pedal 2 and a stroke sensor 6 for detecting a pedal stroke. The amount of operation (depression force and pedal stroke) of the brake pedal 2 by the driver is transmitted to the motor control unit 8. The motor control unit 8 controls the motor 12 by controlling the power supply unit 10 so that the brake operation amount (especially the pedal effort) and the drive amount of the motor 12 (motor rotation angle) have a predetermined relationship, and appropriately drives the motor. A braking force is generated in the disc brake 14. The motor control unit (changing unit) 8 changes the predetermined relationship when wear of each brake pad 20 and 22 is detected. A motor rotation angle sensor (drive amount detection means) 16 is attached to the motor 12.
[0017]
The motor drive disk brake 14 has a structure in which the brake pads 20 and 22 are pressed against the disk rotor 18 from both sides of the disk rotor 18 by driving the motor 12. A pressure sensor 24 that detects the pressure applied to the brake pad 20 is provided between the brake pad 20 and a piston 36 described later. The pressure sensor 24 can detect a weak force of several kg. As will be described later, the pad wear amount is detected by the pressure sensor 24 and the motor rotation angle sensor 16. Further, a braking torque sensor 28 for detecting a braking torque is provided between the brake pad 22 and the caliper 26.
[0018]
As shown in FIGS. 4 to 6, a shaft 34 and a piston 36 are provided inside the cylinder 30 of the motor-driven disk brake 14. The piston 36 has a groove 36a provided obliquely (spiral). The curved arm tip 34b of the shaft 34 is fitted in the groove 36a. The shaft 34 has a gear 34 a, and the gear 34 a meshes with the gear 12 a directly connected to the motor 12. The rotation of the motor 12 causes the gear 12a to rotate, and the gear 34a rotates, whereby the tip 34b of the arm of the shaft 34 slides in the groove 36a of the piston 36, and the piston 36 moves in the cylinder 30 as shown in FIGS. Move left and right. During non-braking, no force is applied to the brake pad 20, and the brake pad 20 and the pad back metal 20a are not fixed and are in a floating state. During braking, the piston 36 moves to the left in FIGS. 4 and 6, and the piston 36 pressurizes the pad back metal 20 a and presses the brake pad 20 against the disc rotor 18. When the brake pad 20 is pressed against the disk rotor 18, the cylinder 30 and the caliper 26 are biased to the right side of the figure by the reaction force from the disk rotor 18, and the brake pad 22 is applied to the disk rotor 18 from the left side of FIGS. Pressed. When the disc rotor 18 rotates in the direction indicated by the arrow a in FIG. 4, the brake pads 20 and 22 are also dragged in that direction, and the end of the pad back metal 22 a collides with the caliper 26. A braking torque sensor 28 is provided to detect the braking torque from the force caused by the collision.
[0019]
Hereinafter, the operation of the present embodiment will be described.
[0020]
When the pedal force sensor 4 and the stroke sensor 6 sense that the driver has started to step on the brake pedal 2, the motor control unit 8 issues a command to the power supply unit 10 and starts rotating the motor 12. Due to the piston return after the previous braking, there is a gap between the piston 36 and the pad back metal 20a or between the brake pad 20 and the disc rotor 18 for preventing dragging. In the initial stage of brake operation, first, the piston is moved so as to fill this gap. This corresponds to the initial stroke shown in FIG. The piston movement for the initial stroke is performed by rotating the motor 12 until a force sufficient to turn on the pressure sensor 24 is felt. After the pressure sensor 24 is turned on, the pressure is not detected and the motor control unit 8 adjusts the pedaling force with which the driver steps on the brake pedal 2 and the motor rotation angle (drive amount of the electric means) to a predetermined relationship. The braking force is controlled. The relationship between the pedal effort and the motor rotation angle is set in advance, for example, as a straight line L1, as shown in FIG. By changing this setting as shown by broken lines X and Y in FIG. 7, the brake feeling can be easily changed. For example, the increase amount of the motor rotation angle may decrease as the pedal effort increases as indicated by the broken line X, or the increase amount of the motor rotation angle increases as the pedal effort increases as indicated by the broken line Y. It can also be set.
[0021]
When releasing the brake, when the treading force sensor 4 and the stroke sensor 6 detect that the driver removes his / her foot from the brake pedal 2, the motor 12 is rotated in reverse until the pressure sensor 24 is turned off. Thereafter, the motor 12 is further rotated in the reverse direction so that a fixed piston return amount is obtained, and a clearance between the piston 36 and the pad back metal 20a or the brake pad 20 and the disk rotor 18 is secured. Thereby, an ideal piston return amount (retraction) after the pressure sensor 24 is turned off can be ensured.
[0022]
Further, when the brake pad 20 or 22 is worn and thinned, the flexure of the pad is reduced. Therefore, even if the piston stroke (motor rotation angle) after the pressure sensor 24 is turned on is the same, the brake pressure is increased. If left untouched, the brake feeling becomes sensitive to the pedaling force, so correction is required.
[0023]
Since the piston 36 is returned by a certain amount after the pressure sensor 24 is turned off, when the brake pad 20 is worn and thinned, the motor rotation angle at the position where the brake pad 20 contacts the disc rotor 18 increases, so the brake pad. A wear amount of 20 can be detected as the advance of the motor rotation angle in the initial stroke. That is, at the initial stage of brake operation, the wear amount of the brake pad 20 is detected by increasing the rotation angle for rotating the motor 12 until the pressure sensor 24 is turned on. And the correction | amendment according to the detected amount of wear is performed. Specifically, the motor rotation angle with respect to the pedal effort is reduced as the brake pad 20 becomes thinner. For example, in the relationship between the pedal effort and the motor rotation angle shown in FIG. 7, the slope of the graph L1 is reduced as shown in the graph L2. In this way, by correcting the “predetermined relationship” so that the motor rotation angle decreases with respect to the same pedal effort, a stable brake feeling can be maintained even when the brake pad 20 is less bent. .
[0024]
The electric brake device according to the present invention is not limited to the one described in the above embodiment, and various devices can be considered.
[0025]
For example, in FIG. 8 and FIG. 9 which is a cross-sectional view taken along line IX-IX, the cam 135 is used instead of the shaft 34, and the shape of the piston 136 is considerably different from that of the above embodiment. It has become.
[0026]
As shown in FIG. 8, the piston 136 is rectangular and has an elongated hole 136a therein. On the other hand, the cam 135 is rotatable with the pin 137 as a fulcrum, and the piston 136 side is divided into two as shown in FIG. 8 and has an elongated arc-shaped hole 135a as shown in FIG. The holes 135a are combined so that one side 136b of the piston 136 penetrates. On the opposite side of the cam 135 from the piston 136, teeth 135b are formed and meshed with a gear 112a directly connected to the motor 112 to constitute a so-called pinion rack mechanism.
[0027]
When the gear 112a is rotated by the motor 112, the cam 135 rotates with the pin 137 as a fulcrum, and the piston 136 moves in the left-right direction in the drawing by the rotational movement of the arc-shaped hole 135a, and braking and release are performed.
[0028]
In the embodiment described above and the like, the brake pedal 2 in the driver's seat is provided with the treading force sensor 4 and the stroke sensor 6. However, by providing the brake pedal 2 with a stroke simulator, the brake pedal 2 can be appropriately counteracted. A force and a stroke can be applied, and the brake feeling similar to that of a hydraulic brake can be secured for the driver.
[0029]
In the case of an electric brake, the brake operating means is not necessarily used continuously in the future, and means such as a push button or a manual lever may be used in the future. In this case, it is also possible to detect an operating force (such as a pressing force for pressing a button or a force for pulling a lever) to operate these means and use these operating forces in place of the pedaling force.
[0030]
As a comparative example, in order to improve the prior art, a pressure sensor having a range of several t, which can cover the entire brake usage range, and feedback-controlling the pressure with respect to the pedaling force can be considered.
[0031]
In this case, since the pressure sensor is in the range of several t and it is difficult to detect a force of several to several tens of kg at the start of braking, the same amount as the return amount when the brake is released is used as the initial stroke. Subsequent motor control adjusts braking force by feedback control of pressure with respect to pedaling force. According to this control method, the braking force change due to the change in the friction coefficient of the brake pad can be automatically adjusted, and the driver can always obtain the same braking force if the pedaling force is the same. In addition, since measures against wear of the brake pads are automatically taken, no special measures against wear are required.
[0032]
However, in this example, the brake pad wear countermeasure is automatically performed by performing feedback control, but a pressure sensor that covers the entire brake use area is required, and a system for performing feedback control is also required, There is a disadvantage that the apparatus becomes larger and more complicated and the cost becomes higher.
[0033]
In contrast, in the present embodiment, the pressure sensor only needs to be able to detect several kg, and only detects the initial brake operation. After that, the pressure is not detected and the pedaling force and the motor rotation angle are set in advance. The predetermined relationship is controlled, and when the wear of the brake pad progresses, the certain relationship is changed accordingly.
[0034]
Therefore, in this embodiment, it is possible to cope with the wear of the brake pad without increasing the size and complexity of the device, and it is possible to ensure a stable brake feeling.
[0035]
【The invention's effect】
As described above, according to the present invention, a stable brake feeling can be maintained regardless of changes in the amount of bending of the brake pad.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the gist of the present invention. FIG. 2 is a schematic diagram showing the overall configuration of an electric brake device to which the present invention is applied. FIG. 3 is an enlarged view of a motor-driven disk brake according to an embodiment of the present invention. Fig. 4 is a cross-sectional view taken along line IV-IV of the motor-driven disc brake of Fig. 3; Fig. 5 is a cross-sectional view taken along line V-V of Fig. 4; FIG. 7 is a diagram showing the relationship between the treading force and the motor rotation angle in the present embodiment. FIG. 8 is a plan view showing another example of the motor-driven disk brake. Sectional view along line IX [Explanation of symbols]
DESCRIPTION OF SYMBOLS 2 ... Brake pedal 4 ... Treading force sensor 6 ... Stroke sensor 8 ... Motor control part 10 ... Power supply part 12 ... Motor 14 ... Motor drive disk brake 16 ... Motor rotation angle sensor 18 ... Disk rotor 20, 22 ... Brake pad 24 ... Pressure sensor 26 ... caliper 28 ... braking torque sensor 30 ... cylinder 34 ... shaft 36 ... piston

Claims (4)

In accordance with the operation of the brake operation means by the driver, an electric means for pressing and separating the brake pad supported on the vehicle body side with respect to the disc rotor rotating with the wheel, and a brake operation amount for detecting the operation amount of the brake operation means And an electric brake device that drives and controls the electric device such that the drive amount of the electric device increases as the brake operation amount that presses the brake pad detected by the brake operation amount detection device increases. In
Pad wear detecting means for detecting wear of the brake pad;
When the brake pad is detected to be worn, the electric drive with respect to the brake operation amount is reduced such that the drive amount of the electric means decreases with respect to the same brake operation amount when the disc rotor is pressed against the brake pad. Means for changing the driving amount of the means;
An electric brake device comprising: 2. The electric brake device according to claim 1, wherein the brake operation means is a brake pedal, and the brake operation amount detected by the brake operation amount detection means is a stepping force applied to the brake pedal.   3. The pad wear detecting means according to claim 1, wherein the pad wear detecting means comprises a pressure sensor for detecting a pressure applied to the brake pad and a driving amount detecting means for detecting a driving amount of the electric means. An electric brake device characterized by detecting pad wear from a driving amount of the electric means in the above. 4. The electric brake device according to claim 3, wherein as the detected pad wear amount increases, the drive amount of the electric means with respect to the brake operation amount for pressing the brake pad is decreased .

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