JPH04243658A - Failure detecting method for electrically-controlled brake device - Google Patents

Abstract

PURPOSE:To provide a method of detecting the failure of an electrically controlled brake device in a simple way. CONSTITUTION:An electrically controlled brake device is judged to be in failure when master cylinder liquid pressure and wheel cylinder liquid pressure do not satisfy the specified condition simultaneously during the operation of a brake pedal in such cases that the wheel cylinder liquid pressure PW is not generated (S5-YES) when the master cylinder liquid pressure PM is generated (S3-YES) and the wheel cylinder liquid pressure PW is generated (S7-NO) when the master cylinder liquid pressure PM is not generated (S3-NO).

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD The present invention relates to a method for detecting a failure in an electrically controlled brake system, and more particularly to a method for detecting a fail in an electrically controlled brake system equipped with a master cylinder and a wheel cylinder. be.

0002

[Prior Art] Conventionally, a brake device for decelerating and stopping an automobile generates hydraulic pressure in a master cylinder by operating a brake operating member such as a brake pedal, and uses that hydraulic pressure to operate a wheel cylinder to reduce friction. A hydraulic brake device is used that presses a member against a rotating body. However, in recent years, an electrically controlled brake device has been proposed in which the hydraulic pressure of a wheel cylinder is controlled based on electrical operation amount detection. For example, JP-A-63-2025
The electrically controlled brake device shown in 6 includes a master cylinder that generates brake fluid pressure according to the operating force of a brake operating member, a wheel cylinder that operates a brake that suppresses rotation of the wheel, and a master cylinder and a wheel. In a hydraulic brake device including a fluid passage communicating with a cylinder, an electrically controlled fluid pressure source that generates brake fluid pressure at a height that produces a braking effect corresponding to the operating force or stroke of a brake operating member is used. A switching device is provided separately from the master cylinder and inserted into the main fluid passageway to connect the electrically controlled fluid pressure source and the master cylinder, whichever generates higher fluid pressure, to the wheel cylinder. The electrically controlled hydraulic pressure source is configured to generate a hydraulic pressure that is gradually higher than that of the master cylinder, and normally the electrically controlled hydraulic pressure source is communicated with the wheel cylinder.

0003

[Problem to be Solved by the Invention] With this arrangement, when the electrically controlled hydraulic pressure source is normal, the hydraulic pressure of the electrically controlled hydraulic pressure source is supplied to the wheel cylinder, but when the electrically controlled hydraulic pressure source fails, is automatically supplied with master cylinder hydraulic pressure. However, since the above switching device has a complicated structure, it is inevitable that the cost will increase, and it is not possible to notify the driver that the electrically controlled hydraulic pressure source has failed.

The present invention has been made against the background of the above-mentioned circumstances, with the object of providing a method for easily detecting a failure in an electrically controlled brake system.

[0005]

[Means for Solving the Problems] The gist of the present invention is that if the difference between the master cylinder hydraulic pressure and the wheel cylinder hydraulic pressure detected at the same time during the operation of a brake operating member is outside the set range, a failure occurs. There is something to be said.

[0006]

[Operation] In an electrically controlled brake system, the master cylinder hydraulic pressure and the wheel cylinder hydraulic pressure detected at the same time during operation of the brake operating member are generally not equal, but are not unrelated. For example, the hydraulic pressure of a wheel cylinder is controlled to a value within a range with a predetermined width with respect to the master cylinder hydraulic pressure itself or a curve representing the value obtained by multiplying the master cylinder hydraulic pressure by a predetermined coefficient. It will be done. Therefore, if the hydraulic pressure in the wheel cylinder falls outside the above range, this means that a failure has occurred in the electrically controlled brake system.

[0007]

According to the present invention, a failure in an electrically controlled brake device can be easily detected. Furthermore, in order to detect a failure by detecting the hydraulic pressure of the wheel cylinder, there are also sensors for detecting the amount of brake operation such as operating force and stroke, a means for determining the target hydraulic pressure based on the output signals of these sensors, and a wheel cylinder. It is possible to detect a failure in any part of an electrically controlled brake device, such as a device that controls hydraulic pressure to a target hydraulic pressure.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1, a brake pedal 10 as a brake operating member is connected to a master cylinder 12, and hydraulic pressure corresponding to the depression force of the brake pedal 10 is generated in the master cylinder 12. Master cylinder 12
is connected to the two-position solenoid valve 16 by a liquid passage 14, and to the reservoir 20 by a liquid passage 18. The 2-position solenoid valve 16 is connected to the liquid passage 1 in its original position.
4 is in communication with the liquid passage 21 and the stroke simulator 22 is shut off, but when the solenoid is energized, the state is switched to a state where the liquid passage 21 is shut off and the master cylinder 12 is communicated with the stroke simulator 22. The stroke simulator 22 accommodates the brake fluid discharged from the master cylinder 12, allows the brake pedal 10 to be depressed, and provides the brake pedal 10 with a reaction force corresponding to the depression stroke. Liquid passage 2
1 is branched into a liquid passage 24 and a liquid passage 25, and the liquid passage 25 is provided with a proportion valve 23.

The liquid passage 24 and the liquid passage 25 each have two
It is branched at the crotch, and one two-position solenoid valve 26, 28 is disposed at each branch. 2 position solenoid valve 2
6 connects the master cylinder 12 and the front wheel cylinder 30 in the original position, and when the solenoid is energized, the hydraulic control valve 32 and the front wheel cylinder 30 communicate with each other.
communicate with. Similarly, the 2-position solenoid valve 28 connects the master cylinder 12 and the rear wheel cylinder 34 in its original position, and when the solenoid is energized, the hydraulic control valve 36
and the rear wheel cylinder 34.

The reservoir 20, the pump 38 and the accumulator 40 are connected to each other by a liquid passage 42, and the liquid in the reservoir 20 is pumped up by the pump 38 and stored in the accumulator 40 at a certain range of liquid pressure. The hydraulic pressure control valve 32 is connected to the accumulator 40, the front wheel cylinder 30, and the reservoir 20 through a liquid passage 42, a liquid passage 44, and a liquid passage 46, and controls the hydraulic pressure of the front wheel cylinder 30 by controlling the excitation current of the solenoid. The height is controlled to correspond to the magnitude of the excitation current. The hydraulic pressure control valve 36 is also similar, and includes an accumulator 40, a rear wheel cylinder 34, and a reservoir 2.
0 through a liquid passage 42, a liquid passage 48, and a liquid passage 46.

FIG. 2 shows an enlarged view of the vicinity of the brake pedal 10. The brake pedal 10 is rotatably attached to a bracket 50 by a support shaft 52. Further, a spring 54 is stretched between an arm portion 56 of the brake pedal 10 and the bracket 50, and is engaged with a pin 58 on the arm portion 56 side and a support member (not shown) on the bracket 50 side, and The pedal 10 is biased counterclockwise. As a result, brake pedal 1
0 is always in contact with the brake switch 62 via the cushion material 60 and is kept at the original position. The brake switch 62 also functions as a stopper. The brake switch 62 includes a rod 66, a spring 68, and a contact 70, as shown in FIGS. 3 and 4. rod 66
is in contact with the cushioning material 60 and compressing the spring 68, the contacts 70 are separated from each other and the brake switch is in the OFF state, and the cushioning material 60 is separated and the rod 66 is pushed out by the spring 68. In this case, the contacts 70 come into contact with each other and turn on.

The pin 58 connects one end of a booster rod 74 to the brake pedal 10, and the other end of the booster rod 74 extends to a booster 76 and is engaged with a reaction piston (not shown).

Further, a load cell type pedal force detection device 80 as a pedal force sensor is disposed on the booster rod 74. The load cell type pedal force detection device 80 detects the compressive force of the booster rod 74 that is generated when the pedal portion 81 is depressed.

The present brake system is controlled by a control device 86. The control device 86 includes a CPU 87, a RAM 88, and a R
It includes an OM 89, an input section 90, an output section 91, and a bus. The brake switch 62, the pedal force sensor 80, the hydraulic pressure sensor 94 that detects the hydraulic pressure of the master cylinder 12 (the hydraulic pressure sensor will be described later in FIG. 5), the hydraulic pressure sensor 95 that detects the hydraulic pressure of the accumulator 40, and the wheel cylinder. hydraulic pressure sensors 96, 97 for detecting the hydraulic pressures of 30, 34;
Wheel speed sensors 98, 9 that detect the rotational speed of the front and rear wheels
9 and a longitudinal G sensor 100 that detects longitudinal acceleration of the vehicle body are connected to an input section 90 of the control device 86,
The output section 91 is connected to the hydraulic pressure control valves 32, 36 and the two-position solenoid valves 16, 26, 28. Control device 86
Various programs are stored in the ROM 89, one of which is a fail detection program for the electrically controlled braking device shown in the flowchart of FIG.

The hydraulic pressure sensors 94, 95, 96, 97 are shown in FIG.
As shown in FIG. 2, mounting screws 102 are provided, and are fixed to the liquid passages 14, 42, 44, and 48, respectively. A liquid passage 104 is formed in the mounting screw 102, and the liquid pressure in the liquid passages 14, 42, 44, 48 is applied to the diaphragm 10.
6. diaphragm 106
The hydraulic pressure transmitted to the sensor 110 is further transmitted to the sensor 110 by the sealed liquid in the sealed chamber 108 . The output voltage of sensor 110 is amplified by amplifier 112 and supplied to input 90 of control device 86 via cable 114 .

In the brake system constructed as described above, while the key switch of the automobile is in the OFF state, the
Position solenoid valves 16, 26, 28 are in the position shown in FIG.
It is in communication with 34. When the key switch is turned on, the two-position solenoid valves 16, 26, 28 are switched, and the master cylinder 12 is communicated with the stroke simulator 22, while the accumulator 40 is communicated with the wheel cylinders 30, 34. Therefore, when the brake pedal 10 is depressed, the stroke simulator 22 applies a reaction force to the brake pedal 10 according to the depression stroke. Therefore, as the depression stroke of the brake pedal 10 increases, the depression force increases, and as shown in FIG. 7, the output voltage of the depression force sensor 80 increases. This output voltage is supplied to the control device 86, and the control device 86
The hydraulic pressures of the wheel cylinders 30 and 34 are controlled via the hydraulic pressure control valves 32 and 36 so that the output voltage of the sensor 100 is at a predetermined level with respect to the output voltage of the pedal force sensor 80. Therefore, regardless of the slope of the road, the load, the friction coefficient of the brake pads, etc.
The deceleration is controlled to a magnitude commensurate with the depression force of the brake pedal 10. This is electrical control mode,
The brake device normally operates in this mode.

However, if a failure occurs in the pedal force sensor 80 as a manipulated variable sensor or the hydraulic pressure control valves 32 and 36, operation in the electric control mode becomes impossible, so this brake device automatically switches to the manual mode. It is possible to switch. Therefore, while the key switch is in the ON state, the program shown in FIG. 6 is repeatedly executed at minute intervals along with other programs (not shown).

First, in step 1 (hereinafter simply referred to as S1; the same applies to other steps), the hydraulic pressure sensor 9
The hydraulic pressure PM of the master cylinder 12 detected at step 4 is read, and furthermore, the hydraulic pressure PW of the wheel cylinders 30, 34 detected by the hydraulic pressure sensors 96, 97 is read at step S2. Here, the hydraulic pressure PW of the wheel cylinder of each wheel detected by the hydraulic pressure sensors 96 and 97 is read. At S3, the hydraulic pressure P of the master cylinder 12
It is determined whether the value of M is 10 kgf/cm2 or more, and if the determination is YES, it is determined in S4 whether the hydraulic pressure PW of each wheel cylinder is 5 kgf/cm2 or less, and the four wheels If at least one of the cylinder hydraulic pressures PW is determined to be YES, it is determined that the electrically controlled brake system has failed, and the manual mode is set in S5. Accordingly, the two-position solenoid valves 16, 26, and 28 are switched to the original position shown in FIG.
2 is separated from the stroke simulator 22 and communicated with the wheel cylinders 30 and 34, so this brake device operates in the same manner as a normal manual brake.

On the other hand, in S4, all four wheel cylinder hydraulic pressures are greater than 5 kgf/cm2 and NO.
If it is determined that the electrically controlled brake system is normal, the electrical control mode described above is set in S6. Also, in S3, the hydraulic pressure PM of the master cylinder 12 is 1
If it is determined to be NO, which is smaller than 0 kgf/cm2, and if at least one of the wheel cylinder hydraulic pressures PW is determined to be NO, which is greater than 5 kgf/cm2, in S7, it is determined that a failure has occurred, and the manual mode is set in S5. is set. Although it is possible to determine that the electrically controlled brake system is normal when the determination is YES in S7, in this embodiment, neither failure nor normality is determined. The program of this example is based on the following problems: master cylinder hydraulic pressure is generated but wheel cylinder hydraulic pressure is not generated, or master cylinder hydraulic pressure is not generated but wheel cylinder hydraulic pressure is generated. This method detects failures based on However, there are special cases where the difference between the master cylinder hydraulic pressure and the wheel cylinder hydraulic pressure is outside the setting range, and in general, Figs. 8 and 10
The present invention can be implemented using a program according to another embodiment shown in FIG.

In S11 of FIG. 8, the hydraulic pressure PM of the master cylinder 12 detected by the hydraulic pressure sensor 94 is read, and in S12, the anti-skid control, The wheel cylinder hydraulic pressures PW of wheels that are not subjected to special control such as traction control or distribution control of left and right braking force during turning braking are read. In S13, the wheel cylinder hydraulic pressure P read in S12 is
It is determined whether W is a value less than or equal to the upper limit value P1 and greater than or equal to the lower limit value P2. Here, the upper limit value P1 and the lower limit value P2 are set by adding constant widths ΔPA and -ΔPB to the value obtained by multiplying the hydraulic pressure PM of the master cylinder 12 by a coefficient k, and as shown in FIG. 9, P1= It is a value expressed as k・PM +ΔPA P2=k・PM −ΔPB. In this embodiment, since the wheel cylinder hydraulic pressure PW is generally controlled to a value obtained by multiplying the master cylinder hydraulic pressure PM by a coefficient k,
The upper limit value P1 and lower limit value P2 are set as described above. If the determination is YES in S13, the brake system is normal and the above-mentioned electric control mode is set, and if the determination is NO, it has failed and the above-mentioned manual mode is set.

Still another embodiment is shown in FIG. S21
The master cylinder hydraulic pressure PM is read in S2.
2, the wheel number i is set to 1. The wheel number i indicates the position of each wheel and is set in advance. In this embodiment, the wheel number i of the left front wheel (FL) is 1,
Hereinafter, right front wheel (FR), left rear wheel (RL), right rear wheel (RR)
The wheel numbers i are 2, 3, and 4, respectively. S2
In step 3, the wheel cylinder hydraulic pressure PW (FL) is read as the wheel cylinder hydraulic pressure PW (1). S
At step 24, it is determined whether the hydraulic pressure PW (FL) is within the set range, and if the determination is YES, the wheel cylinder hydraulic pressure PW (FL) is determined to be normal. Next, in S25, it is determined whether the wheel number i≧4, and in this case, since the wheel number i=1, the determination is NO, and in S26, the value of the wheel number i is incremented, and the process returns to S23, where the wheel number The value of the wheel cylinder hydraulic pressure PW (FR) with number i=2 is read.

On the other hand, if the determination is NO in S24, it is determined in S27 whether anti-skid control is being performed by the control device 86 for the left front wheel (FL), and if the determination is YES, the wheel control is performed in S28. It is determined whether the value of the hydraulic pressure PW (FL) of the cylinder is within the setting range for anti-skid control (P4 or more and P3 or less). Here, P3 and P4 are the values expressed as P3=k・PM +ΔPC P4=k・PM −ΔPD like P1 and P2, and as shown in FIG. 9, P3 is a larger value than P1, and P4 is It is set to a value smaller than P2. When the wheel cylinder hydraulic pressure PW of a specific wheel is anti-skid controlled by the control device 86,
The wheel cylinder hydraulic pressure PW of that wheel may be controlled to a value outside the setting range P2 to P1, and in that case, even though the wheel cylinder hydraulic pressure PW of that wheel is normal, It will be determined that it is not normal. Therefore, it is determined whether the wheel cylinder hydraulic pressure PW of the wheel is within a range P4 to P3 that is wider than the set range P2 to P1. If the determination is YES in S28, the wheel cylinder hydraulic pressure PW (FL) is normal, and S25 and subsequent steps are executed. On the other hand, if the determination is NO in S27, the wheel cylinder hydraulic pressure PW is outside the setting range P2 to P1 even though anti-skid control is not being performed, and this brake system is considered to have failed, and the manual control is activated in S30. mode is set. Also, if the determination in S28 is NO, it is determined that the brake device has failed.

As mentioned above, if the wheel cylinder hydraulic pressure PW of at least one wheel is outside the above setting range, it is said that the brake system has failed, but the wheel cylinder hydraulic pressure of four wheels is If all PWs are determined to be normal, the wheel number i=4 and S2
The determination in step 5 is YES, indicating that the brake device is normal, and is set to the electric control mode in S29.

Furthermore, by providing a plurality of switches that are sequentially turned on each time the brake pedal 10 is operated by a predetermined stroke, the hydraulic pressure sensor 9 can be adjusted at a plurality of points in time.
4 and the output values of the hydraulic pressure sensors 96 and 97, it is also possible to detect a failure of the electrically controlled brake system.

In addition, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art without departing from the scope of the claims.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an electrically controlled brake device in which a fail is detected by a fail detection method that is an embodiment of the present invention.

FIG. 2 is a front view showing a brake switch, a pedal force sensor, and a brake pedal in the above embodiment.

FIG. 3 is a front sectional view showing a state in which the brake switch of the above embodiment is OFF.

FIG. 4 is a front sectional view showing a state in which the brake switch of the above embodiment is ON.

FIG. 5 is a sectional view of the hydraulic pressure sensor of the above embodiment.

FIG. 6 is a flowchart showing one of the programs stored in the control device of FIG. 1;

FIG. 7 is a graph showing the relationship between the stroke and the output voltage value of the pedal force sensor under normal conditions.

FIG. 8 is a flowchart showing a program of another embodiment of the present invention.

FIG. 9 is a graph showing the relationship between pedal force and hydraulic pressure under normal conditions.

FIG. 10 is a flowchart showing a program of still another embodiment of the present invention.

[Explanation of symbols]

10 Brake pedal 30 Wheel cylinder 34 Wheel cylinder 56 Arm part 62 Brake switch 66 Rod 68 Spring 70 Contact 80 Pedal force sensor 86 Control device 94 Liquid pressure sensor 96 Liquid pressure sensor 97 Liquid pressure sensor

Claims (1)

[Claims] Claim 1: A failure of an electrically controlled brake system in which a failure occurs if the difference between the master cylinder hydraulic pressure and the wheel cylinder hydraulic pressure detected at the same point in time during operation of a brake operating member is outside a set range. Detection method.