JP4000675B2 - Brake device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize a clearance generating between a friction material and a rotor in non-braking time by eliminating an influence caused by the drift of the output of a pressing sensor, and to surely exhibit a reduction effect of dragging and a suppression effect against the delay in responsiveness for braking. SOLUTION: A differentiating circuit for the output of a press sensor 8 and a circuit comparing a differential quatient with a set threshold, are provided for an electrically drive braking device, and the control of a clearance is executed with a position where the differentiation value of the output of the press sensor is smaller than a set threshold, as an origin. The change rate of the output of the press sensor is suddenly changed at a position where a clearance between each pad 5 and a disc rotor 4 is zero, and since the position is set up as the origin, the clearance is thereby stable, so that dragging and a delay in responsiveness for braking hardly occurs.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a so-called by-wire type brake device for a vehicle (hereinafter referred to as an electric drive brake device).
[0002]
[Prior art]
The electric drive brake device controls an electric actuator by an electronic control device so as to generate a braking force corresponding to the output based on an output of a sensor that detects a brake operation force or a brake operation amount, and the friction material is rotated by the actuator. The wheel is braked by pressing the wheel.
[0003]
As a conventional example of this electrically driven brake device, for example, there is one disclosed in Japanese Patent Laid-Open No. 9-137841. The apparatus of the publication discloses a clearance generated between the friction material and the rotor during non-braking in the following manner, that is, a pressure sensor (referred to as a thrust sensor in the publication) for detecting the pressing pressure of the friction material and the friction material. A sensor for detecting the position of the electric actuator is provided, and the position where the output of the pressure sensor becomes zero is set as the origin, and the propellant of the electric actuator is moved backward by the position sensor output until the clearance reaches a specified value. I have to.
[0004]
[Problems to be solved by the invention]
If the above clearance is too small, the friction material contacts the rotor during non-braking due to the vibration of the rotor, and so-called drag occurs, which causes vehicle fuel consumption, friction material life, brake judder, etc. Become.
[0005]
On the other hand, if the clearance is too large, the time from when the brake pedal is depressed until the braking force is generated becomes long, causing problems such as a delay in braking response.
[0006]
Therefore, although sufficient consideration is given in setting the clearance, the method of setting the position where the output of the pressure sensor becomes zero as the origin of the clearance control as in the apparatus of Japanese Patent Laid-Open No. 9-137842, the temperature There is a disadvantage that the origin fluctuates due to the influence of changes and the like and the clearance varies due to this.
[0007]
That is, as shown in FIG. 4, the clearance must be zero when the sensor output is zero (solid line in FIG. 4). However, as indicated by the dotted line in the figure, when the output of the pressure sensor drifts due to the influence of temperature change, a deviation occurs between the sensor output zero position and the clearance zero position. Clearance is not secured.
[0008]
The clearance secured between the friction material and the rotor during non-braking is generally very small, about 0.5 mm, so the effect of sensor output drift is not negligible. To reduce drag and prevent response delay It is desirable to eliminate the influence.
[0009]
An object of the present invention is to increase the accuracy of clearance control in response to such a request.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, the origin of the clearance generated between the friction material and the rotor is set based on the output of the pressure sensor when the brake is released, and the motor is electrically driven from the origin until the clearance reaches a specified value. In a vehicle brake device that moves the actuator propellant backward, a differential circuit for the pressure sensor output and a circuit for comparing the differential value with a set threshold value are provided, and the origin of the clearance is determined by comparing the differential value of the pressure sensor output with the set threshold value. It was decided to control the clearance.
[0011]
In addition, an electric actuator that presses the friction material and makes sliding contact with the rotor, an electronic control device that controls the electric actuator, and a pressure sensor that detects a pressing force applied to the friction material, In a vehicular brake device that sets the origin of the clearance generated between the friction material and the rotor based on the output and retracts the propellant of the electric actuator from the origin until the clearance reaches a specified value, the rotational position of the motor or the brake A position detection sensor for detecting the position of the piston is provided, a differential circuit for the pressure sensor output and a differential circuit for the position detection sensor output are provided, and a ratio of the differential value of the pressure sensor output to the differential value of the position detection sensor. Comparing circuit provided with a dividing circuit for calculating the value and comparing a division result by the dividing circuit with a set threshold value Provided, decide the origin of clearance by comparing the division result and the preset threshold is had as clearance control is performed.
[0012]
The above-mentioned threshold value is set to a value (for example, a value as close to zero as possible) that can determine a sudden change in the differential value of the output of the sensor in consideration of the output characteristics of the pressure sensor.
[0013]
[Action]
The principle of origin setting by the brake device of the present invention will be described with reference to FIG.
Now, when the propellant of the electric actuator begins to move backward due to the release of braking, the output of the pressure sensor gradually decreases. The change rate of the sensor output at this time changes suddenly at the position where the pressing force does not act on the friction material (the position where the clearance is zero). By detecting the differential value of the sensor output and comparing it with the set threshold value, the sudden change position can be detected. If it is set as the origin, the origin is always set at the zero clearance (or almost zero) position, and there is an extreme deviation of the origin. Does not occur.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of an electrically driven brake device according to the present invention. This is an application example to a floating type disc brake, in which 1 is a brake pedal and 2 is a pedal force sensor for detecting the depression force of the brake pedal 1. The pedal force sensor 2 may be replaced with a stroke sensor that detects the depression amount of the brake pedal 1. Whether the brake pedal is ON or OFF can be determined based on whether or not the pedal force sensor 2 is output, but a brake switch for detecting the ON / OFF may be separately added. It is also free to add a stroke simulator (not shown) that generates a depressing reaction force of the brake pedal 1.
[0015]
3 is an electronic control unit that inputs information from various sensors to control the electric actuator 10, 4 is a disk rotor, 5 is a pad (friction material), 6 is a caliper, and 7 is a housing fixed to the caliper 6.
[0016]
The electric actuator 10 includes a brake piston 11 that is inserted into a cylinder of the caliper 6 and stopped by a pad 5 (or caliper 6), a ball nut 12, a screw shaft 13 that is screwed to the ball nut 12, and an electric motor 14. And a gear set 15 comprising a pinion 15a and a spur gear 15b as main elements. The power of the motor 14 is transmitted through the gear set 15 to rotate the screw shaft 13, and the rotation of the screw shaft 13 causes the brake piston to rotate. 11 propels and presses the pad 5.
[0017]
In the illustrated brake device, a sleeve 16 and a spring 17 are interposed between the ball nut 12 and the end wall of the brake piston 11, and the sleeve 16 compresses the spring 17 and hits the end wall of the brake piston 11. After that, a thrust is generated in the brake piston 11. Further, a piston seal 18 is provided so that the return of the brake piston 11 is performed by the elastic restoring force of the piston seal 18.
[0018]
Further, an analog pressure sensor 8 (which may be a load cell, a strain sensor or the like) for detecting the pressing pressure by the brake piston 11 and an encoder for controlling the rotational speed of the motor 14 in order to execute the control described later. 9 and further includes a differentiation circuit (not shown) of the output of the pressure sensor 8 and a circuit (also not shown) for comparing the differential value of the sensor output with a set threshold. . The encoder 9 may be replaced with a position sensor as described in JP-A-9-137841. However, when a motor with a built-in encoder is used, the clearance can be controlled with a simpler structure.
[0019]
In this brake device, the electric actuator 10 is controlled by the electronic control unit 3 so as to generate a braking force according to the output of the pedal force sensor 2, and the pad 5 is pressed by the advanced brake piston 11 to rotate integrally with the disc rotor 4. A wheel (not shown) is braked. Further, when the braking is released, the brake piston 11 returns.
[0020]
Since the illustrated brake device employs an electric actuator of a reversible mechanism, the brake piston 11 can be returned by the force of the piston seal 18 while the motor 14 is de-energized. This device does not require clearance control when the clearance control target value is the same as the piston return amount by the piston seal 18, but controls the return amount of the ball nut 12 (= piston return amount) when the condition is not satisfied. There must be.
[0021]
For the control, the apparatus shown in the figure takes the output of the pressure sensor 8 into the electronic control unit 3 when the brake is released, passes it through a differentiation circuit, monitors the differential value, and the absolute value of the differential value is a predetermined threshold value. The smaller point is set as the origin, and the return amount (piston return amount) of the ball nut 12 from there is confirmed by the encoder 9, and when the return amount reaches a predetermined value, the reverse rotation of the motor 14 is stopped and the position is reached. The ball nut 12 is held.
[0022]
In this embodiment, the absolute value of the differential value is compared with the set threshold value. However, the differential value of the pressure sensor output when the brake is released has a negative value, and the point where this value becomes almost zero is the origin. The point where this differential value becomes larger than the set threshold may be used as the origin.
[0023]
The release of braking can be detected when the detection signal of the pedal force sensor 2 is smaller than a certain threshold value or when the brake switch is changed from ON to OFF. The above-described control is executed.
[0024]
In addition, if the control described above is executed when it is confirmed that the output of the pressure sensor has become smaller than a certain threshold after confirming the release of braking, the reliability of the positioning of the origin of the clearance can be improved. Get higher.
[0025]
FIG. 2 shows a flowchart of the control. The steps from the brake pedal ON to the pedal OFF are the same as the control in the conventional electric drive brake device. If advanced behavior control such as anti-lock is necessary, from the wheel speed sensor or acceleration sensor (both not shown) Based on this information, increase / decrease control of the pressing force (braking force) is performed.
[0026]
Further, when braking is released, clearance control with less error is performed according to the procedure described above.
[0027]
FIG. 3 shows a flowchart of control in the second embodiment. The difference between the differential value of the position detection sensor signal and the differential value of the pressure sensor signal and the set threshold value is obtained from the clearance origin from the first embodiment of FIG. The position detection signal is a differential value of the count number when the number of pulses is counted like an encoder. In the second embodiment, the control is slightly complicated, but since the influence of the time is eliminated because the ratio of the change amount of the pressing force to the change amount of the position is used as a reference, the brake is released slowly in the first embodiment. In such a case, there is a problem that the absolute value of the differential value of the pressure sensor output is also reduced and the difference from the set threshold value is reduced. However, the problem is solved in the second embodiment.
[0028]
【The invention's effect】
As described above, the brake device according to the present invention performs clearance control with the origin at the position where the change rate of the sensor output changes suddenly, not at the position where the output of the press sensor becomes zero. The effect of drift is eliminated, the clearance generated between the friction material and the rotor during non-braking is stabilized, and the effect of reducing drag and the effect of suppressing braking response delay are reliably exhibited.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of the brake device. FIG. 2 is a diagram showing an example of a control flowchart of the device. FIG. 3 is a diagram showing another example of the control flowchart. Fig. 5 is a diagram showing the deflection of the origin of the clearance by Fig. 5
DESCRIPTION OF SYMBOLS 1 Brake pedal 2 Treading force sensor 3 Electronic controller 4 Disc rotor 5 Pad 6 Caliper 7 Housing 8 Press sensor 9 Encoder 10 Electric actuator 11 Brake piston 12 Ball nut 13 Screw shaft 14 Motor 15 Gear set 16 Sleeve 17 Spring 18 Piston seal

Claims (2)

It has an electric actuator that presses the friction material and makes sliding contact with the rotor, an electronic control device that controls the electric actuator, and a pressure sensor that detects the pressure applied to the friction material. In the vehicle brake device for setting the origin of the clearance generated between the friction material and the rotor on the basis, and retracting the propellant of the electric actuator until the clearance reaches a specified value from the origin, a differentiation circuit for the pressure sensor output, A vehicular brake device characterized in that a circuit for comparing a differential value with a set threshold value is provided, and the clearance control is performed by determining the origin of the clearance by comparing the differential value of the pressure sensor output with the set threshold value. It has an electric actuator that presses the friction material and makes sliding contact with the rotor, an electronic control device that controls the electric actuator, and a pressure sensor that detects the pressure applied to the friction material. In the vehicular brake device in which the origin of the clearance generated between the friction material and the rotor is set based on this, and the propellant of the electric actuator is moved backward from the origin until the clearance reaches a specified value, the rotational position of the motor or the brake piston A position detection sensor for detecting the position is provided, a differentiation circuit for the pressure sensor output and a differentiation circuit for the position detection sensor output are provided, and a ratio of the differential value of the pressure sensor output to the differential value of the position detection sensor is calculated. And a comparison circuit for comparing the result of division by the division circuit and a set threshold value. , The division result as a vehicle brake system, wherein the clearance control decided origin clearance by comparison with a set threshold value has to be made.

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