JP4071349B2 - Brake device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a brake device including a stroke sensor and a hydraulic pressure sensor, and more particularly to a brake device that enables failure detection of the stroke sensor and the hydraulic pressure sensor.
[0002]
[Prior art]
A brake device having a brake assist function (BA function) that applies a braking force larger than a braking force determined by a pedal position to a wheel when a driver's brake operation speed is equal to or higher than a predetermined value is known (US Pat. No. 5,158,343, JP-A-7-156767, etc.). This is because the driver's brake operation is measured using a stroke sensor, and when a brake operation faster than a predetermined threshold is detected, it is determined that this is an emergency brake and a full brake is automatically applied. That's it.
[0003]
Separately from this, a brake device having an automatic brake function used for the purpose of adjusting the distance between the preceding vehicle and the like is known. This means that a relatively low braking force is automatically generated under a specific condition based on some judgment. In this case, it is necessary to apply a low braking force smoothly, and the hydraulic pressure is controlled so that the target brake hydraulic pressure is equal to the actual brake hydraulic pressure detected by the hydraulic pressure sensor.
[0004]
[Problems to be solved by the invention]
By the way, in the automatic brake system having both the brake assist function and the automatic brake function described above, both the stroke sensor and the hydraulic pressure sensor are used. If these sensors break down, an unintended sudden brake is applied. It may be trapped, or it may become impossible to start with the brakes applied. Therefore, in order to detect a sensor failure, it is conceivable that both sensors can be duplicated and the output of the duplicated sensors can be compared so that the failure of the sensor can be detected. In addition to an increase in cost, problems such as inability to secure a mounting space for the sensor occur.
[0005]
In view of the above circumstances, an object of the present invention is to provide a brake device capable of detecting failure of sensors without providing double stroke sensors and hydraulic pressure sensors.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the brake device according to the first aspect of the present invention detects the depression amount of the brake cylinder and the master cylinder connected to the two pipes by generating the braking fluid pressure corresponding to depression of the brake pedal. And a hydraulic pressure sensor for detecting a braking hydraulic pressure generated by the master cylinder provided in each of the pipes, and assisting a stepping force of the brake pedal and transmitting it to the master cylinder. And a booster that operates the automatic brake by applying a force to the master cylinder while moving the brake pedal by the control device. The control device operates the automatic brake during the parking brake operation. The stroke sensor or each hydraulic pressure sensor is compared by comparing the output value of the stroke sensor with the output value of each hydraulic pressure sensor. Characterized in that any failure of the with fault detection means for determining by majority.
In this brake device, when both the stroke sensor and the hydraulic pressure sensor are normal, a certain relationship is established between the output values of both sensors. Accordingly, the output values of the stroke sensor and the hydraulic pressure sensor are compared, and if it is detected that the two output values are out of a certain relationship, it is determined that the sensor has failed.
[0007]
Brake device of the invention of claim 2 is the invention of claim 1, wherein the failure detecting means, stores a table showing the non-linear characteristics of the output value and the output value of the hydraulic pressure sensor of the stroke sensor during normal After one of the output values of the stroke sensor or the hydraulic pressure sensor is converted by the table , the converted value is compared with the other output value, and a failure occurs when the deviation exceeds a threshold value. It is characterized by determining.
In this brake device, when both the stroke sensor and the hydraulic pressure sensor are normal, a non-linear relationship (non-linear characteristic) is established between the output values of both sensors due to the effect of brake rigidity. That is, in the low hydraulic pressure region (the region where the brake rigidity is low), a large amount of brake fluid is consumed for the deformation of the brake hose and the low rigidity portion of each part, and the hydraulic pressure shifts to the medium-high pressure region (the region where the brake rigidity is relatively high). Accordingly, the brake fluid is consumed to generate an effective braking force. Accordingly, a non-linear relationship is established between the output value of the stroke sensor, which is the amount of depression of the brake pedal, and the detected value of the brake hydraulic pressure output from the hydraulic pressure sensor, instead of a linear relationship. The failure detecting means stores a table of data indicating this non-linear characteristic, and converts the output value of one sensor using this table. Then, the converted value is a value that compensates for the influence of the brake rigidity described above. Therefore, when both sensors are normal, the converted value should be approximately equal to the output value of the other sensor. Therefore, the converted value is compared with the output value of the other sensor to check the deviation. If the deviation is larger than the threshold value, it is determined that one of the sensors is faulty.
[0009]
According to a third aspect of the present invention, the brake device according to the first or second aspect is characterized in that the failure detecting means resets a past failure detection memory by an ignition OFF operation or an ignition ON operation after the ignition OFF. .
In the case of this brake device, when the brake air is released, the output of the stroke sensor and the hydraulic pressure sensor may be out of a certain relationship, which may cause a temporary false detection. Even in this case, the ignition is turned off. If it is turned on again after being turned off, the previous failure memory is automatically deleted.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration of a brake device according to an embodiment. Reference numeral 1 in the figure denotes a stroke sensor that detects the amount of depression of the brake pedal BP, and the signal is input to the control device 2. The brake pedal BP is connected to a booster 4, and the booster 4 is connected to a master cylinder 9 that generates a brake fluid pressure.
[0011]
Two pipes 21 and 22 for transmitting the generated braking fluid pressure are connected to the master cylinder 9. One pipe 21 is connected to two pipes 23 and 24 via the ABS modulator 10. The other pipe 22 is also connected to the two pipes 25 and 26 via the ABS modulator 10. Further, wheel brakes 11, 12, 13, 14 for generating a braking force with the transmitted braking fluid pressure are connected to the pipes 23, 24, 25, 26 after the ABS modulator 10. The pipes 22 and 21 are provided with hydraulic pressure sensors 16 and 17 for detecting a braking pressure generated by the master cylinder 9.
[0012]
What is indicated by 15 is an ABS controller, and the ABS controller 15 controls the transmission of braking fluid pressure from the master cylinder 9 to the wheel brakes 11, 12, 13, 14 by supplying a signal to the ABS modulator 10. If necessary, avoid the locking tendency of each wheel.
[0013]
Pressure conduits 5, 6 are connected to each pressure chamber of the doubler device 4, and the pressure conduit 6 leading to the pressure chamber (working pressure chamber) on the brake pedal BP side is connected to the system pressure source (constant pressure source) via the electromagnetic valve 3. ) 7 or a second pressure source (operating pressure source) 8 is selectively connected. The pressure conduit 5 leading to the opposite pressure chamber (constant pressure chamber) is fixedly connected to a system pressure source (constant pressure source) 7. As an example of the gas booster, the constant pressure source is an intake manifold of the engine, the operating pressure source is atmospheric pressure, and the operating pressure source is maintained at a higher pressure than the constant pressure source.
[0014]
The control device 2 takes in the output signal of the stroke sensor 1, the output signals of the hydraulic pressure sensors 16 and 17, or the signal of the ABS controller 15, and gives a control signal to the electromagnetic valve 3. For example, when the control device 2 determines that the speed of the signal of the stroke sensor 1 (depressing speed of the brake pedal BP) exceeds a threshold value, it determines the start of the BA brake (braking by brake assist), and the electromagnetic valve 3 Is driven to connect the pressure conduit 6 to the second pressure source 8 and a full brake is applied to generate braking force on the wheel brakes 11, 12, 13, 14 via the ABS modulator 10. In addition, if it is determined that a relatively low braking force should be applied smoothly and automatically for the purpose of adjusting the inter-vehicle distance from the preceding vehicle, etc., the start of automatic braking is determined and the target brake fluid pressure Then, the electromagnetic valve 3 is controlled so that the actual brake fluid pressure detected by the brake fluid pressure sensors 16 and 17 becomes equal, and the brake fluid pressure is feedback-controlled.
[0015]
In addition, the control device 2 also functions as a failure detection means 2 a that detects a failure of the stroke sensor 1 and the hydraulic pressure sensors 16 and 17. In the case of this brake device, when both the stroke sensor 1 and the hydraulic pressure sensors 16 and 17 are normal, there is a non-linear relationship between the output values Vs and Vp of both sensors due to the influence of brake rigidity as shown in FIG. (Nonlinear characteristics) is established. That is, in the low hydraulic pressure region (the region where the brake rigidity is low), a large amount of brake fluid is consumed for the deformation of the brake hose and the low rigidity portion of each part, and the hydraulic pressure shifts to the medium-high pressure region (the region where the brake rigidity is relatively high). Accordingly, the brake fluid is consumed to generate an effective braking force. Accordingly, a non-linear relationship is established between the output value Vs of the stroke sensor 1 that is the amount of depression of the brake pedal and the output value Vp of the hydraulic pressure sensors 16 and 17 instead of a linear relationship.
[0016]
The failure detection means 2a in the control device 2 stores a data table (characteristics in FIG. 2) indicating the nonlinear characteristics. Then, the output value Vs of the stroke sensor 1 is converted using this table. Then, the converted value V ′s is a value that compensates for the influence of the brake rigidity described above. Therefore, when both the stroke sensor 1 and the fluid pressure sensors 16 and 17 are normal, the converted value V ′s is The output value Vp of the hydraulic pressure sensors 16 and 17 should be almost equal. Therefore, the failure detection means 2a compares the converted value V's with the output values Vp of the hydraulic pressure sensors 16 and 17, and checks the deviation | V's-Vp | When it is larger, it is determined that one of the sensors has failed.
[0017]
Next, the content of control by the control device 2 will be described below with reference to a flowchart. The control routine of the flowchart shown in FIG. 3 is started and executed at regular time intervals by timer interrupt processing.
[0018]
In step 101 after the ignition is turned on, first, the failure flag F_Flag is reset. In the next step 102, it is determined whether or not a failure has already been detected during the current ignition on period. If the failure has been detected, the processing in step 102 is repeated until the ignition is turned off. If no failure is detected, the stroke sensor value Vs and the hydraulic pressure sensor value Vp are read in steps 103 and 104, respectively. Here, for example, Vp can be calculated as an average value of the outputs Vp1 and Vp2 of the two hydraulic pressure sensors 16 and 17.
[0019]
Next, it is determined in step 105 whether or not the parking brake is operating. If the parking brake is operating, the automatic brake is increased or decreased to a predetermined pressure at a predetermined speed for detecting a failure in step 106. If it is determined in step 105 that the parking brake is not activated, it is determined in step 107 whether or not BA brake (brake assist braking) control is necessary. If necessary, the BA brake is activated in step 108. Further, in step 109, it is determined whether or not the automatic brake is applied for the purpose of adjusting the distance between vehicles, and the automatic brake is applied if necessary.
[0020]
Needless to say, even if any of the determinations in steps 105, 107, and 109 is no longer necessary, the stroke and hydraulic pressure increase and decrease due to the driver's brake operation will occur. During the increase / decrease of these strokes and hydraulic pressure, in step 111, the stroke sensor value Vs is converted to V's using the nonlinear conversion input / output table shown in FIG. It is checked whether or not the difference of V's exceeds a predetermined threshold value C. If the difference between Vp and V's exceeds a predetermined threshold C, it is determined that a failure has occurred in either the stroke sensor 1 or the hydraulic pressure sensor 16, 17, and in step 113, a failure flag F_Flag = 1, F_Flag = 1 is maintained until the ignition is turned off thereafter.
[0021]
Next, another control example will be described. FIG. 4 is a flowchart showing the contents. In this example, the failure part can be determined more accurately by comparing the outputs of the three hydraulic pressure sensors 16 and 17 and the stroke sensor 1.
[0022]
In step 201 after starting the ignition, first, failure flags F_Vp1, F_Vp2, and F_Vs representing failure of each sensor are reset. In the next step 202, it is determined whether or not two or more sensor failures have already been detected during the current ignition off period, and if two or more sensor failures have been detected, the ignition is turned off. Perform an infinite loop. If no failure is detected and if only one sensor failure is detected, the stroke sensor value Vs and the hydraulic pressure sensor values Vp1 and Vp2 are read in step 203, respectively.
[0023]
Next, if it is determined in step 204 that the parking brake is operating, in step 205, the automatic brake is increased or decreased to a predetermined pressure at a predetermined speed for failure detection. If it is determined in step 204 that the parking brake is inoperative, it is determined in step 206 whether or not a failure of the stroke sensor 1 has been detected. If the stroke sensor has failed, the hydraulic pressure sensor value is determined in step 207. Is used to determine whether or not the BA brake control is necessary. If the BA brake control is necessary, the BA brake control is performed at step 208.
[0024]
If the stroke sensor 1 is normal, it is determined in step 209 whether or not the BA brake control is necessary using the stroke sensor value. If the BA brake control is necessary, the process proceeds to step 208. Further, in step 210, it is determined whether or not the automatic brake is applied for the purpose of adjusting the distance between vehicles, and if necessary, the automatic brake is applied using the normal hydraulic pressure sensor value in step 211. Let And the failure determination process shown in FIG. 5 is performed during increase / decrease in these strokes and hydraulic pressures.
[0025]
In the failure determination routine of FIG. 5, first, in step 212, the stroke sensor value Vs is converted to V's using the nonlinear conversion input / output table characteristics shown in FIG. The failure flag F_Vp1 of the pressure sensor 16 is checked. If the failure flag F_Vp1 = 1, that is, if a failure has already occurred in the hydraulic pressure sensor 16, the converted value V's of the output Vs of the stroke sensor and the output value of the remaining hydraulic pressure sensor 17 in step 214. Compare Vp2. If the difference | V′s−Vp2 | exceeds the threshold value C, it is impossible to determine which sensor has failed at this time, so in step 215, the failure flag F_Vp2 of the hydraulic pressure sensor 17 is detected. = 1, and in step 224, the failure flag F_Vs = 1 of the stroke sensor 1 is set.
[0026]
Similarly, in step 216, the failure flag F_Vs of the stroke sensor 1 is checked, and if the failure flag F_Vs = 1, that is, if a failure has already occurred in the stroke sensor 1, the hydraulic pressure sensor is detected in step 217. The output values Vp1 and Vp2 of 16 and 17 are compared. If the difference | Vp1−Vp2 | exceeds the threshold value C, it is impossible to determine which sensor has failed at this time, so in step 218, the failure flag F_Vp1 = 1 of the hydraulic pressure sensor 16 In step 227, the failure flag F_Vp2 = 1 of the hydraulic pressure sensor 17 is set.
[0027]
Further, similarly, in step 219, the failure flag F_Vp2 of the hydraulic pressure sensor 17 is checked. If the failure flag F_Vp2 = 1, that is, if a failure has already occurred in the hydraulic pressure sensor 17, the flow goes to step 220. The conversion value V ′s of the output Vs of the stroke sensor and the output value Vp1 of the remaining hydraulic pressure sensor 16 are compared. If the difference | V′s−Vp1 | exceeds the threshold value C, it is impossible to determine which sensor has failed at this time, so in step 215, the failure flag F_Vs = In step 230, the failure flag F_Vp1 = 1 of the hydraulic pressure sensor 16 is set.
[0028]
If it is determined in step 213, 216, 219 that no failure has occurred in any sensor, three sensor output values are obtained in steps 222 and 223, steps 225 and 226, and steps 228 and 229. Are compared, and failure determination is performed based on the principle of majority vote. That is, if two of the three sensor output values are the same and the rest are different, the two sensors that generate the same output are determined to be normal, and the sensors that show different output values are determined to be faulty.
[0029]
For example, in steps 222 and 223, V's is compared with Vp1 and Vp2. If V's is different for both Vp1 and Vp2, it is determined that the stroke sensor 1 has failed, and a failure flag F_Vs = 1 is set in step 224. In steps 225 and 226, Vp2 is compared with V's and Vp1. If Vp2 is different from V ′s and Vp1, it is determined that the hydraulic pressure sensor 17 has failed, and a failure flag F_Vp2 = 1 is set in step 227. In steps 228 and 229, Vp1 is compared with V's and Vp2. If Vp1 is different from V ′s and Vp2, it is determined that the hydraulic pressure sensor 16 has failed, and a failure flag F_Vp1 = 1 is set in step 230.
[0030]
In this way, by comparing the output values of the three sensors (stroke sensor 1 and hydraulic pressure sensors 16, 17), it is possible to determine not only the sensor failure but also which sensor has failed. it can.
[0031]
【The invention's effect】
As described above, according to the invention of claim 1, paying attention to the fact that there is a fixed relationship between the output value of the stroke sensor and the output value of the hydraulic pressure sensor, by comparing both output values, Since the failure of the stroke sensor or the hydraulic pressure sensor is determined, the failure of the sensor can be reliably detected without duplicating the stroke sensor and the hydraulic pressure sensor. Therefore, the cost is not increased and the problem of securing the mounting space for the sensor does not occur.
[0032]
According to the invention of claim 2, since both sensor outputs are compared with each other in consideration of the nonlinear characteristics of the stroke sensor output and the hydraulic pressure sensor output relating to the brake rigidity, the failure detection of both sensors is accurately performed. be able to.
[0034]
According to the invention of claim 3 , since the failure detection memory is reset by the ignition OFF operation or the ignition ON operation after the ignition OFF, the failure is temporarily erroneously determined as when the brake air is released. Even if there is a case, no special failure memory erasure operation is required.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of a brake device according to an embodiment of the present invention.
FIG. 2 is a view showing a table stored in the control device of the brake device.
FIG. 3 is a flowchart showing control contents of a control device of the brake device.
FIG. 4 is a flowchart showing another example of control contents of the control device of the brake device.
FIG. 5 is a flowchart showing details of a subroutine in the flowchart of FIG. 4;
[Explanation of symbols]
BP Brake pedal 1 Stroke sensor 2 Control device (Failure detection means)
2a Failure detection means 9 Master cylinder 16, 17 Hydraulic pressure sensor

Claims (3)

A master cylinder that generates braking fluid pressure in response to the depression of the brake pedal and is connected to the two pipes, a stroke sensor that detects the depression amount of the brake pedal, and the master cylinder that is provided in each of the pipes A brake device having a hydraulic pressure sensor for detecting a braking hydraulic pressure,
A booster device for assisting the depression force of the brake pedal and transmitting it to the master cylinder and operating the automatic brake by applying a force to the master cylinder while moving the brake pedal by a control device;
The control device operates the automatic brake during parking brake operation, compares the output value of the stroke sensor with the output value of each hydraulic pressure sensor, and malfunctions of either the stroke sensor or each hydraulic pressure sensor. A brake device comprising a failure detection means for determining a vehicle by majority vote.   The failure detection means stores a table indicating non-linear characteristics between the output value of the stroke sensor and the output value of each hydraulic pressure sensor at a normal time, and one of the output values of the stroke sensor or the hydraulic pressure sensor 2. The brake according to claim 1, wherein after the conversion is performed according to the table, the converted value is compared with the other output value, and when the deviation exceeds a threshold value, a failure is determined. apparatus. 3. The brake device according to claim 1, wherein the failure detection unit resets a past failure detection memory by an ignition OFF operation or an ignition ON operation after the ignition is turned OFF .

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