JPH10258718A - Brake fluid pressure controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set an average current value unchanged even in a case of changing a dither period by setting a pulse width modulation period to one/integer of the changed dither half period in a case of changing the dither period. SOLUTION: When a brake pedal 1 is stepped on, a controller ECU30 reads a signal from a pressure sensor 9. The controller ECU30 calculates a current value matched with the fluid pressure feeding to a wheel cylinder 3 according to an operation quantity and at the same time switches the communication of a fail-safe valve 8 to a fluid pressure control valve 5 side. Secondly, the controller ECU 30 feeds a dither to a solenoid 22 by superimposing it to the operated current value. The solenoid 22 outputs a propulsion responding to the fed current value, and the fluid pressure is fed to a wheel cylinder 3 so as to provide a braking force. The PWM period may be set to one/even number of the dither half period for preventing the changes in the average current value, when the dither period is changed by a fail-safe treatment, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake fluid pressure control device for controlling an actual fluid pressure according to a target fluid pressure, and more particularly to a brake fluid pressure control device suitable for use in an electronic braking force control device.

[0002]

2. Description of the Related Art As is well known, a brake fluid pressure control device used in a braking force control device of an automobile or the like is digitized so as to effectively use the braking force of each wheel or depress a brake pedal. Control is performed so that each wheel does not lock even if it goes out. Normally, a solenoid is provided in the brake fluid pressure control device, and the fluid pressure is controlled by driving a fluid pressure control valve by controlling a current flowing through the solenoid.

In this type of brake fluid pressure control device, a dither current is superimposed on a current for driving the solenoid in order to prevent the spool provided in the fluid pressure control valve from sticking. This dither current has a triangular waveform, and its cycle (hereinafter referred to as dither cycle)
Is set equal to a control cycle set in advance for performing control.

[0004] As described above, the dither current is a current flowing through the solenoid to prevent the spool from sticking, so that the deviation of the average current is preferably zero. That is, when the dither current is superimposed on the current for driving the solenoid, it is preferable that the average value of the current after the superposition is set to be equal to the value of the current for driving the solenoid before the superposition. However, it is difficult to make the deviation of the average current completely zero, and various controls are performed so as to approach zero.

As one of the controls, the above-described triangular-wave-shaped dither current is generated by PWM-modulated pulses.
By changing the pulse width during modulation,
There is one that solves the above problem by changing the duty ratio. In this control, for example, the average value of the dither current by the PWM modulation is changed between a portion where the dither current rises (hereinafter referred to as rising dither) and a portion where the dither current falls (hereinafter referred to as falling dither). To solve the above problem.

FIG. 6 shows an example of a dither current.
In the example shown in FIG. 6, the dither cycle T _D is set to be the same as the control cycle. The dither period T _D is divided into a roughly with elevated dither period T ₁ and the falling dither period T _2. In this example, it is set the same time the increase dither period T ₁ and a lowered dither interval T _2. Further, as can be seen from FIG. 6, the dither current is generated by PWM modulation. In this example, PWM modulation period T _P is set to be one-tenth of the dither period T _D. That, PWM modulation period T _P is contained five cycles to increase the dither period T _1, and thus contained 5 cycles in descending dither interval T _2. This PWM modulation period _TP is set to be fixed.
The average value of the dither current is _Ia as shown.

[0007]

As described above, the above-described processing is conventionally performed by changing the duty ratio. However, in recent years, various fail-safe methods have been used to prevent accidents. Processing has been done. When the fail-safe processing is performed, the fail-safe processing must be performed with the highest priority, so that the above-described control cycle may be extended.

FIG. 7 shows that the control cycle changes and the dither cycle becomes P
WM modulation period T_PDither power when extended by one cycle
It is a figure which shows a flow. As shown in this figure, the dither
Period T _D'Is the PWM modulation period T_PFor 11 cycles (T_D+ T_P)
Therefore, the rising dither section T₁And descending dither section T_TwoWhen
Are the same, the PWM modulation period T_POn the way
Processing rises in dither section T₁Dither section T from_TwoChange to
Will be updated. In this case, the average current I shown in FIG._aCompared to
The average current is I_a′
Was.

The present invention has been made in view of the above circumstances, and has as its object to provide a brake fluid pressure control device in which the average current does not change even if the dither cycle changes.

[0010]

In order to solve the above-mentioned problems, the present invention provides a detecting means for detecting an operation amount of a brake pedal, and a target hydraulic pressure to be applied to a wheel cylinder in accordance with a detection result of the detecting means. Control means for calculating a current value corresponding to the above, and outputting a drive current in which a triangular-wave-shaped dither created by pulse width modulation is superimposed on the target hydraulic pressure, and a hydraulic pressure according to the drive current to the wheel cylinder. A brake fluid pressure control device having a supply means for supplying
When the dither cycle is changed, a setting change unit that sets the pulse width modulation cycle to an integer fraction of the changed dither half cycle is provided.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an entire brake fluid pressure control device according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a brake pedal, and the master cylinder 2 generates a hydraulic pressure when the brake pedal 1 is depressed.

Reference numeral 3 denotes a wheel cylinder for generating a braking force by hydraulic pressure, reference numeral 4 denotes an external hydraulic pressure supply source for supplying boosted hydraulic pressure, and reference numeral 5 denotes a brake pedal based on the operation amount of the brake pedal 1. A hydraulic pressure control valve for adjusting the pressure acting on the wheel cylinder 3 from the external hydraulic pressure supply source 4;
Controls the hydraulic pressure supplied from the external hydraulic pressure supply source 4 to the wheel cylinder 3 by controlling the driving of the hydraulic pressure control valve 5 to apply a braking force to the wheel cylinder 3 according to the operation amount of the brake pedal 1. Is a controller ECU that generates the following. The controller ECU 30 includes a CPU (central processing unit), a ROM (Read Only Memory), and a RAM (Random
Access memory) and a clock are provided. The RAM storage device is provided with a storage area for storing various information described below.

The controller ECU 30 has a function of calculating and calculating signals for controlling the motor 4c, the fail-safe valve 8, the solenoid 22, the hydraulic pressure passage opening / closing valve 29, and the like, based on various signals input thereto. . Further, a dither current value to be superimposed on the current supplied to the solenoid 22 is calculated, and this dither current value is calculated as P
It has a function to create by WM modulation. Further, the controller ECU 30 is provided with a dither signal generation circuit including a transistor and the like for generating a dither signal by the PWM modulation.

A pipe 4 on the output side of the master cylinder 2
3 is connected to a stroke simulator 7 that gives a stroke and a reaction force when the driver operates the brake pedal 1 via a switching valve 6, and is connected to the wheel cylinder 3 via a fail-safe valve 8. ing. Reference numerals 9 and 10 denote pressure sensors for measuring the hydraulic pressures of the master cylinder 2 and the wheel cylinder 3, respectively.
30.

Next, the internal structure of the external hydraulic pressure supply source 4 will be described. Reference numeral 4a denotes a hydraulic pump. The hydraulic pump 4a is driven by a motor 4c, sucks brake fluid from a reservoir 4d, and generates boosted hydraulic pressure. An accumulator 4b is connected to the output side of the hydraulic pump 4a so as to store a boosted high hydraulic pressure to be supplied to the wheel cylinder 3. Reference numeral 4E denotes a pressure sensor for detecting the pressure in the accumulator 4b. Based on the detection result from the pressure sensor 4E, the controller ECU 30 determines whether the pressure of the accumulator 4b becomes equal to or less than a predetermined value.
The motor 4c is driven to pressurize by the hydraulic pump 4a.

Next, the structure of the hydraulic control valve 5 will be described. Reference numeral 11 denotes a body, and a stepped valve hole 12 is provided inside the body 11, and a hydraulic pressure supply port 13, a drain port 14, and an output port 15 communicating with the valve hole 12 are provided, respectively. Is open in the valve hole 12. That is, the hydraulic pressure supply port 13 is connected to the external hydraulic pressure supply source 4, and the drain port 14 is connected to the reservoir 4d and is open to the atmosphere. The output port 15 is connected to the wheel cylinder 3 via a fail-safe valve 8 described later.

A spool 16 is slidably housed in the valve hole 12. The spool 16 is provided coaxially and is composed of two cylindrical members having different diameters, and has a function of controlling communication between the hydraulic pressure supply port 13 and the drain port 14 and the output port 15. A variable throttle s is provided between the hydraulic pressure supply port 13 and the small diameter spool 16a.
Is formed, and a variable throttle t is formed between the drain port 14 and the large diameter spool 16b. Therefore, when the spool 16 moves to the left in the drawing, the variable throttle t closes, and the variable throttle s opens to increase the pressure of the output port 15.

The output of the output port 15 is connected to a reaction force chamber 18 at one end of the hydraulic pressure control valve 5 through a pipe 17 branched from a pipe 32 toward the wheel cylinder 3. The force chamber 18 constitutes a reaction force generating means 19.
The reaction force chamber 18 is formed of a space of the valve hole 12 between one end of the valve hole 12 and the large-diameter spool 16b. When the brake pedal 1 is not operated, FIG.
The compression spring 21 for closing the variable aperture s and keeping the variable aperture t in communication is provided.

At the other end of the pressure control valve 5, a proportional solenoid 22 is provided. This solenoid 22
A movable member 23 provided coaxially with the valve hole 12 and movably in the axial direction; a coil 24 and a yoke 25 provided to apply a thrust to the movable member 23 in the axial direction; A compression spring 26 is provided between the armature 23 and the yoke 25 and applies an elastic force to the left in the figure.

A line between the accumulator 4b of the external hydraulic pressure supply source 4 and the hydraulic pressure supply port 13 of the hydraulic pressure control valve 5 having the above-described structure is provided with a fluid that is opened and closed by a signal from the controller ECU 30. A pressure passage opening / closing valve 29 is provided. In other words, when the hydraulic pressure supply opening / closing valve 29 opens and closes the hydraulic pressure supply path from the external hydraulic pressure supply source 4 to the hydraulic pressure control valve 5, the brake pedal 1 is not operated as shown in FIG. The high-pressure brake does not leak to the wheel cylinder 3 side. Note that A
When the control of the BS function or the traction control function is performed, not only the operation amount of the brake pedal 1 described below, that is, not only the output of the sensor 9 in this embodiment but also the wheel speed sensor 44 or the acceleration sensor, the yaw rate The target hydraulic pressure is calculated based on a signal from a sensor that detects the behavior of the vehicle such as a sensor or a steering sensor (both not shown).

In the above configuration, when the brake pedal 1 is depressed, the controller ECU 30
And calculates a current value corresponding to the hydraulic pressure supplied to the wheel cylinder 3 according to the operation amount of the brake pedal 1, opens the switching valve 6, and opens the hydraulic passage opening / closing valve 29. The communication of the failsafe valve 8 is switched to the hydraulic pressure control valve 5 side. Next, the controller EC
U30 superimposes the dither on the calculated current value and supplies it to the solenoid 22. The solenoid 22 generates a thrust corresponding to the current value supplied from the controller ECU 30 in the left direction in FIG. 1 to propel the spool 16 in the left direction in the figure. In this case, the controller ECU 30
Since the dither is superimposed on the current output from, the spool 16 moves to the left in the figure while dithering in the left and right directions in FIG. Thus, the spool 16 moves to the left in FIG.
Is opened, the hydraulic pressure is supplied to the wheel cylinder 3 via the output port 15 and the pipe line 32, so that a braking force is obtained.

On the other hand, when the brake pedal is released, the controller ECU 30 reads the brake pedal with a signal output from the pressure sensor 9 so that the hydraulic pressure of the wheel cylinder 3 provided for each wheel is reduced to 0 MPa. Calculate the appropriate current value. This current value is set in advance according to the characteristics of the hydraulic pressure control valve 5 and the wheel cylinder 3. The controller ECU 30 superimposes dither on the calculated current value and outputs it to the solenoid 22. As a result, the solenoid 22
Is generated, the spool 16 is returned to the right in FIG. 1 to open the variable throttle t, and the brake fluid supplied to the wheel cylinder 3 is returned to the reservoir 4 d of the external hydraulic pressure supply 4 to return to the wheel 4. The hydraulic pressure in the cylinder 3 disappears. Then, the controller ECU 30 confirms that the hydraulic pressure of the wheel cylinder 3 has become 0 MPa based on the output of the pressure sensor 44, switches the fail-safe valve 8 to the master cylinder 2 side, and closes the hydraulic pressure passage opening / closing valve 29. still,
When the brake fluid pressure of the wheel cylinder 3 is lowered despite the operation of the brake pedal 1, the controller ECU 30 switches the fail-safe valve 8 to the fluid pressure control valve 5 side based on this detection signal. Instead, the hydraulic pressure from the master cylinder 2 is supplied to the wheel cylinder 3 by communicating with the master cylinder 2 side.

The overall configuration and operation of the brake fluid pressure control device according to one embodiment of the present invention have been described above. Next, a dither current waveform superimposed on the current supplied to the solenoid 22 will be described. Is a waveform of the underlying indicated waveform in FIG. 6, but the dither cycle PWM modulation period as shown in FIG. 7 by the fail-safe processing, etc. T _P
When extending by one cycle of, or change or change from a raised dither period T ₁ in the middle of the PWM modulation period T _P as described above to descend dither period T _2, from the lowered dither period T ₂ to the raised dither period T ₁ Therefore, the average current of the dither current changes.

However, as shown in FIG. 2, when the dither period is T _D ″, that is, when the dither period T ₀ is extended by two PWM modulation periods T _P (T _D +2
T _P ), as described above, from the rising dither section T ₁ to the falling dither section T _{2 in} the middle of the PWM modulation period T _P even if the rising dither section T ₁ and the falling dither section T ₂ are set to be the same. changed or, the average current of the dither current is no longer able to change to or changed from the lowered dither period T ₂ to the raised dither period T _1.

That is, in order to prevent the average current of the dither current from fluctuating when the control cycle, that is, the dither cycle changes, the length of the rising dither section and the length of the falling dither section are set to be the same. period of the interval may be set to be an even multiple of the PWM modulation period T _P (2n times).
In other words, in order to prevent the fluctuation of the average current when the dither cycle changes, the PWM cycle may be set to an even number (1 / 2n) of the dither half cycle. This is the point of the present invention.

Next, the flow of actual control when the above-described control is performed will be described. FIG. 3 shows a controller EC provided in the brake fluid pressure control device according to one embodiment of the present invention.
It is a flowchart which shows the control example of U30. This flowchart shows processing for one dither cycle. In the following processing, a counter for measuring the elapsed time, a register for storing the elapsed time, a register for storing the control cycle, a register for storing the PWM modulation cycle, and a descending dither are output in the RAM provided in the controller ECU 30. There is provided a register or the like for storing the switching time to be performed, and the control proceeds with reference to the contents of this register.

In the register storing the control cycle, "10" is stored in advance as a basic control cycle, the control cycle is set to 10 msec, and the register storing the PWM modulation cycle is stored in the register storing the reference control cycle. Based on "1"
Is stored, and the PWM modulation cycle is set to 1 msec. The register for storing the switching time for outputting the falling dither stores “5” because the rising dither section and the falling dither section are set to be the same, and the length of the rising dither section and the falling dither section is Is 5ms
ec.

When the process starts, in step S1, a counter provided in the RAM for measuring an elapsed time is initialized. That is, a process of substituting “0” into this counter is performed. When the initialization is completed, the content of this counter is rewritten to the content indicating the elapsed time each time the time elapses. When the process in step S1 ends, the process proceeds to step S2. In step S2, the content of the counter storing the elapsed time is compared with the content of the register storing the control cycle. That is, in step S2, a process of measuring the control cycle is performed.

If it is determined "No" in step S2, that is, if it is determined that the elapsed time has not elapsed for the control cycle, the contents of the register whose elapsed time is measured and the control cycle are determined again. Is compared with the contents of the register storing. On the other hand, if "Yes" is determined in step S2, that is, if it is determined that the elapsed time has elapsed by the control period, the content of the counter for measuring the elapsed time is substituted into the register for storing the elapsed time. Is done.

In step S3, the content of the register for storing the elapsed time is divided by 10 (ie, 2n),
A process for substituting the period into a register for storing the period is performed. That is, in the process of step S3, the number of PWM cycles included in the dither cycle is fixed at 10 cycles without being changed.
A process of changing the PWM modulation cycle is performed. In other words, the PWM modulation cycle is set to 1/10 (1 / 2n) of the dither cycle.

When the above processing is completed, the process proceeds to step S4. In step S4, the process of outputting the dither current in the rising dither section is started. At this time, the PWM modulation cycle is modulated based on the PWM modulation cycle calculated in step S3. When the process of the ascending dither section is started in step S4, the process proceeds to step S5, in which the process of reinitializing the content of the counter for measuring the elapsed time, that is, the process of substituting “0” into this counter is performed. Also in this case, as described in step S1, the content of the counter is rewritten to indicate the elapsed time each time the time elapses.

In step S6, the content of the register storing the elapsed time, which is the previous control cycle, is divided by 2 as the switching time for outputting the descending dither, and is substituted into the register indicating the switching time. The reason for providing the register indicating the switching time is that if the control cycle is extended by spending time on other processing described below,
This is for the purpose of turning back between the ascending dither section and the descending dither section.

In step S7, processing other than the processing relating to the dither current, for example, processing such as fail-safe processing, is performed. When the time set in step S6 elapses, the processing in the descending dither section is started. That is, the process of step S8 is interrupted, and the controller ECU 3
From 0, a process is performed in which the current on which the dither for the falling dither section is superimposed is output to the solenoid 22. Step S
When the processing of No. 8 is completed, the processing for one dither cycle is completed. When the processing described above and the processing in step S7 are completed, the processing returns to step S2, and the above-described processing is repeatedly performed.

FIG. 4 is a diagram showing the relationship between the duty and the current value during PWM modulation in the rising dither section and the falling dither section. In the processing of steps S4 and S8 shown in FIG. 3, the triangle wave is subjected to PWM modulation described below and output. This process is necessary to keep the average value of the dither current constant. The relationship between the duty and the current value of the PWM modulation in increasing the dither interval is represented by the curve reference numeral I ₁₀ is attached, the relationship between the duty and the current value of the PWM modulation in descending dither interval, reference numeral I _It is represented by the curve marked ₂₀ . Reference numeral I ₃₀ is affixed straight line showing the relationship between the duty and the current value of an ideal PWM modulation.

In the figure, for example, when the current value is 1.0
In the case of [A], if the relationship between the duty and the current value in the rising dither section and the falling dither section is the same, the PWM modulation may be performed with a constant duty, but as shown in FIG. Since the characteristics are different between the rising dither section and the falling dither section, the duty is set to 60% in the rising dither section and 20% in the falling dither section. FIG. 5 is a diagram showing a dither waveform according to the present invention. As shown in this figure, the control cycle (dither cycle)
Does not change from the rising dither section to the falling dither section in the middle of the PWM modulation cycle, and conversely, does not switch from the falling dither section to the rising dither section.

As described above, in this embodiment, the PW
The M modulation cycle is set to 1/10 of the dither cycle. However, when the dither cycle is set to be long, the PWM modulation cycle is set to 1/12 of the dither cycle, and when the dither cycle is set to be short, PWM is set. The PWM modulation cycle is set to 1/8 of the dither cycle, for example, the modulation cycle is set to 1/8 of the dither cycle.
If it is (1 / 2n), PW according to the length of the dither cycle
The M modulation period may be changed. Further, in the present embodiment, the lengths of the ascending dither section and the descending dither section are the same, and each section is set to be half of the dither cycle. The length of the falling dither section may be set to an even number (1 / 2n) of the dither cycle.

In the embodiment of the present invention described above, the average value of the dither current does not change even when the dither cycle changes. Therefore, the dither effect can be changed by appropriately adjusting the dither cycle. In addition, since the PWM modulation cycle can be arbitrarily set, the frequency of turning on / off the transistor for performing the PWM driving operation can be reduced, so that heat generation of the PWM driving circuit can be suppressed.

[0038]

As described above, according to the present invention,
Even when the dither cycle is changed, the pulse width modulation cycle is changed to an integer fraction of the half dither cycle, so that the average current value does not fluctuate.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an entire brake fluid pressure control device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining a dither average current when a control cycle changes.

FIG. 3 is a flowchart illustrating a control example of a controller ECU 30 provided in the brake fluid pressure control device according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating a relationship between a duty and a current value during PWM modulation in a rising dither section and a falling dither section.

FIG. 5 is a diagram showing a dither waveform according to the present invention.

FIG. 6 is a diagram illustrating an example of a dither current.

7 is a diagram showing a dither current when the dither cycle control period is changed is extended by one cycle of the PWM modulation period T _P.

[Explanation of symbols]

Reference Signs List 3 Wheel cylinder 4 External hydraulic pressure supply source (supply means) 5 Hydraulic pressure control valve (supply means) 9 Pressure sensor (detection means) 30 Controller ECU (control means, setting change means)

Claims (1)

[Claims] 1. A detecting means for detecting an operation amount of a brake pedal, and a current value corresponding to a target hydraulic pressure to be applied to a wheel cylinder is calculated in accordance with a detection result of the detecting means. A brake fluid pressure control device comprising: a control unit that outputs a drive current in which a triangular-wave-shaped dither created by modulation is superimposed; and a supply unit that supplies a hydraulic pressure according to the drive current to the wheel cylinder. A brake fluid pressure control device comprising: a setting change unit that sets the pulse width modulation period to an integer fraction of the changed dither half period when the period is changed.