JP2004224119A - Brake control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake control device capable of generating stable braking force in response to stepping-on force of brake pedal even when the driving state of an internal combustion engine is changed. <P>SOLUTION: The brake control device is provided with a stepping-on force amplifying means amplifying the stepping-on force of a driver with a negative pressure generated by the internal combustion engine, a master cylinder generating fluid pressure in response to the stepping-on force of the driver amplified by the stepping-on force amplifying means, a pump driven by a motor to be an oil pressure generating source, a wheel cylinder generating the braking force on each wheel having the master cylinder and the pump as oil pressure sources, and a brake control means controlling the drive of the pump. A negative pressure detection means is provided to detect the negative pressure generated by the internal combustion engine, and when the detected negative pressure is not more than a prescribed pressure, the brake control means drives the motor to increase the pressure of the wheel cylinder having the pump as the oil pressure source. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a brake control device provided with a tread force amplifying device for amplifying a tread force of a driver, and more particularly to a tread force amplifying device utilizing negative pressure of an internal combustion engine and a brake control device capable of increasing the pressure of a wheel cylinder by a pump.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, tread force amplifying means that amplifies a driver's tread force by using a negative pressure generated by an engine is widely known. Here, in general, as the engine speed increases, the negative pressure decreases, so that the amplifying power varies according to the driving state of the engine. Therefore, as a technique for stably amplifying the driver's treading force even when the driving state of the engine changes, for example, a technique described in Patent Document 1 is known. In this publication, a mechanism for changing the amplification power in two stages is provided, and the amplification power is switched according to the situation of the vehicle. Thus, a stable braking force against the pedaling force is ensured.
[0003]
[Patent Document 1]
JP-A-6-32217
[Problems to be solved by the invention]
However, the above-described related art has the following problems. That is, it is necessary to provide a mechanism capable of changing the amplifying power in two stages, and there is a problem that the manufacturing cost increases. In addition, when the situation of the vehicle changes frequently, the amplifying force changes frequently, and the braking force changes accordingly. Therefore, the driver may feel uncomfortable.
[0005]
The present invention has been made in view of the above-mentioned conventional problems, and provides a brake control device capable of generating a stable braking force with respect to a pedaling force even when the driving state of an internal combustion engine changes. With the goal.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a negative pressure detecting means for detecting a negative pressure generated by the internal combustion engine is provided. When the detected negative pressure is equal to or less than a predetermined pressure, the motor is driven, and the wheel is driven by using the pump as a hydraulic pressure source. By increasing the pressure in the cylinder, a stable braking force can be generated even if the amplification force for amplifying the driver's pedaling force changes.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings.
[0008]
(Embodiment 1)
FIG. 1 is an overall view showing a brake control device according to Embodiment 1 of the present invention. It is assumed that the brake control device is mounted on a vehicle having a so-called automatic transmission in which the rotation of the engine is input via a torque converter, and the speed is output using a planetary gear.
[0009]
In the figure, MC is a master cylinder as a braking pressure generating means, which is a well-known tandem type. The master cylinder MC is provided with a booster BT using a negative pressure generated at an intake port of the engine. Here, the booster BT will be described. Air is introduced into the cylinder Es of the engine from an air intake passage Ein through a throttle TH. The combustion of the air and fuel once inhaled causes the piston PT to move up and down, and the burned air is output from the discharge path Eout. When the engine is driven, suction and discharge are repeated, so that a negative pressure is generated in the suction passage Ein. A booster circuit B is connected to the booster BT in the suction passage Ein, and assists the depression force of the brake pedal BP by using the negative pressure generated in the suction passage Ein. The intake path Ein is provided with an idle-up circuit Eup that bypasses the throttle TH. When it is desired to increase the idling speed in a cold state or the like, the idle-up circuit Eup is opened to increase the amount of intake air. Increase engine speed. In the present embodiment, the idle-up circuit Eup is provided. However, the present invention is not limited to this configuration. When an electronically controlled throttle is used, the idling speed is controlled by controlling the throttle opening. It may be controlled.
[0010]
The above-described engine control is controlled by an engine control unit ECU. This ECU is executed based on a signal from a sensor group SG including an engine speed sensor, an oil temperature sensor, a throttle opening sensor, and the like.
[0011]
When the brake pedal BP is depressed, pressure is generated in the master cylinder MC by the driver's depressing force and the assisting force of the booster BT. Then, the brake fluid as a fluid is supplied to the wheel cylinder WC as the braking force generating means via the two brake circuits 1 and 2. The reservoir RES for storing the brake fluid is provided in the master cylinder MC.
[0012]
The brake circuits 1 and 2 have a connection structure called a so-called X pipe. That is, the brake circuit 1 is branched at the branch point 1b and connects the wheel cylinder WC (FL) of the left front wheel and the wheel cylinder WC (RR) of the right rear wheel, and the brake circuit 2 is branched at the branch point 2b. The right front wheel cylinder WC (FR) and the left rear wheel cylinder WC (RL) are connected.
[0013]
In the present embodiment, an existing ABS unit ABSU is used.
The configuration will be described. In the brake circuits 1 and 2, upstream of the branch points 1b and 2b (on the master cylinder side), the switching valves 20 and 20 that are switched by the master cylinder pressure, and the oil pressure in the wheel cylinder extremely increases In this case, relief one-way valves 21 and 21 are provided on the master cylinder side for relief.
[0014]
The switching valve 20 normally keeps the master cylinder side and the wheel cylinder side in communication with each other, and when the hydraulic pressure is supplied from the master cylinder side, the switching valve 20 is switched against the spring force and the switching valve 20 is switched from the master cylinder side. This is a one-way valve that allows only hydraulic pressure supply. The relief one-way valves 21 and 21 are provided with springs with a large load, and always maintain a closed state during normal brake control regardless of the relationship between the master cylinder pressure and the wheel cylinder pressure.
[0015]
Downstream from the branch points 1b and 2b (on the side of the wheel cylinder WC), there are provided inflow valves 5 and 5, which are normally open ON / OFF valves driven by a solenoid.
Further, an outflow valve 6 composed of a normally closed ON / OFF valve driven by a solenoid is provided in the drain circuit 10 connecting a position downstream of each inflow valve 5 and the reservoir 7.
The inflow valve 5 and the outflow valve 6 reduce, maintain, and increase the pressure of the wheel cylinder WC. If the inflow valve 5 is opened and the outflow valve 6 is closed, the brake circuits 1 and 2 are closed. When both the valves 5 and 6 are closed, the brake fluid pressure is contained in the wheel cylinder WC, and the inflow valve 5 is closed and the outflow occurs. When the valve 6 is opened, a reduced pressure state is established in which the braking pressure in the wheel cylinder WC is released to the reservoir 7.
[0016]
Further, a pump 4 is connected to the brake circuits 1 and 2.
The pump 4 performs an operation of sucking the brake fluid released to the reservoir 7 by the ABS control from the suction circuit 41 and returning the brake fluid to the brake circuits 1 and 2 through the discharge circuit 43. In the present embodiment, the motor 8 A driven plunger pump is used.
[0017]
Therefore, in this embodiment, when wheel lock is likely to occur during braking, the inflow valve 5 and the outflow valve 6 are operated as necessary to increase, maintain, and reduce the pressure of the wheel cylinder WC. In addition to controlling the brake fluid pressure optimally, the brake fluid released to the reservoir 7 can be subjected to ABS control for returning the brake fluid to the brake circuits 1 and 2 at any time.
[0018]
Here, a case where it is desired to increase the pressure of the wheel cylinder FL by the brake assist control in the brake circuit 1 will be described. When the pressure is increased by the pump 4, the switching valve 20 is switched to the one-way valve side when the driver depresses the brake pedal BP, and the inflow valve 5 is turned off and opened, and the outflow valve 6 is turned off and closed. 8 drives the pump 4 to increase the pressure. At this time, since the master cylinder MC and the pump 4 are connected via the one-way valve of the switching valve 20, the hydraulic pressure does not flow backward from the pump 4 side to the master cylinder MC side. Note that the relief one-way valve 21 also maintains the closed state.
[0019]
The drive of the motor 8 (pump 4) and the drive of each of the inflow valve 5 and the outflow valve 6 in such ABS control are controlled by the control unit CU.
The control unit CU is connected to a sensor group SG for detecting a running state and transmits and receives information to and from the ECU. The sensor group SG includes a pressure sensor that detects the pressure of the master cylinder MC, a vehicle speed sensor that detects a vehicle speed, a wheel speed sensor that detects each wheel speed, and the like.
[0020]
FIG. 2 is a flowchart illustrating the brake assist control during cold air according to the embodiment.
[0021]
In step 101, the deceleration of the vehicle is calculated.
[0022]
In step 102, the vehicle deceleration change rate is calculated.
[0023]
In step 103, it is determined whether or not the negative pressure of the suction passage Ein is reduced. If it is determined that the negative pressure is reduced, the process proceeds to step 104; otherwise, the process proceeds to step 107. Specifically, the ECU detects whether or not the idle-up circuit Eup has been opened by the cold control.
[0024]
In step 104, it is determined whether or not the deceleration is larger than a1. If the deceleration is larger, the process proceeds to step 106; otherwise, the process proceeds to step 105.
[0025]
In step 105, it is determined whether or not the rate of change in deceleration is greater than b1, and if it is, the procedure proceeds to step 106, otherwise the procedure proceeds to step 107.
[0026]
In step 106, the cold brake assist control is executed. The details of the control will be described later.
[0027]
In step 107, the motor drive flag MOTOR_f is set to 0, and the ON duty PAB_Cont, which is the motor drive PWM control signal, is set to 0.
[0028]
In step 108, it is determined whether or not the rate of change in deceleration is greater than b2. If it is, the procedure proceeds to step 110; otherwise, the procedure proceeds to step 109.
[0029]
In step 109, it is determined whether or not the deceleration is larger than a2. If the deceleration is larger, the process proceeds to step 110. Otherwise, the control is repeated.
[0030]
FIG. 3 is a flowchart showing the brake assist control during cold operation.
[0031]
In step 201, the drive pattern ratio α of the motor 8 is calculated from the deceleration-deceleration change rate map.
[0032]
In step 202, the motor drive flag MOTOR_f is set to 1, and the ON duty PAB_Cont, which is the motor drive PWM control signal, is set to α calculated from the map.
[0033]
The brake assist control will be described in detail.
As described in FIG. 1, the master cylinder MC of the present embodiment is provided with a booster BT. The booster BT assists the driver's pedaling force by using a negative pressure in the suction passage Ein of the engine. Here, an idle-up circuit Eup that bypasses the throttle TH that adjusts the intake air amount is provided in the intake path Ein of the engine. When the engine is started in a cold region or the like, an auxiliary load such as an air conditioner heater is driven to increase an engine load. To cope with this, the engine is driven at a speed higher than the idling speed at room temperature. At this time, since the idle-up circuit Eup is opened, the negative pressure generated in the suction passage Ein becomes small.
[0034]
Therefore, whether or not the idle-up circuit EUp has been opened is received from the ECU, and it is determined whether or not the negative pressure has decreased. When the negative pressure is low, the calculated deceleration (master cylinder pressure) is compared with a threshold a1 smaller than the threshold a2 in the normal brake assist control, and when the negative pressure is larger than a1, the assist force of the booster BT is insufficient. Executes the brake assist control at cold time that compensates for. Even when the deceleration is smaller than the threshold value a1, the calculated deceleration change rate is compared with a threshold value b1 smaller than the threshold value b2 in the normal brake assist control. The brake assist control at the time of cold to compensate for the insufficient assisting force of the booster BT is executed.
[0035]
FIG. 4 is a map for calculating the drive pattern ratio α of the motor 8 in the cold brake assist control. The relationship between the deceleration and the deceleration change rate corresponding to each drive pattern ratio α shown in this map and the relationship between the calculated deceleration and the deceleration change rate correspond to which drive pattern ratio is calculated. To determine. Then, the ON duty ratio in the PWM control is set based on the determined α, and the motor 8 is driven.
[0036]
FIG. 5 is a diagram showing the relationship between the driver's depression force and the brake fluid pressure. In FIG. 5, the thin solid line indicates the brake characteristics when the negative pressure drops, and the thin dotted line indicates the maximum value of the cold-time brake assist characteristics when the negative pressure drops. Further, a bold solid line indicates a normal brake characteristic, and a bold dotted line indicates a normal brake assist characteristic. That is, by driving the pump 4 when the negative pressure drops, it becomes possible to secure the same brake fluid pressure as the normal brake characteristics, and it is possible to obtain a sufficient braking force.
[0037]
When the rate of change in deceleration is greater than b2 or when the rate of deceleration is greater than a2, normal brake assist control is executed. At this time, if it is determined that the normal brake assist control is necessary after the cold brake assist control is executed, the motor drive pattern is determined to secure the brake fluid pressure corresponding to the normal brake assist force. By outputting the ratio as a value obtained by adding the decrease in the negative pressure, it becomes possible to secure the same brake fluid pressure as the normal brake assist characteristic, and it is possible to obtain a sufficient braking force.
[Brief description of the drawings]
FIG. 1 is an overall view showing a brake control device according to a first embodiment.
FIG. 2 is a flowchart illustrating brake assist control according to the first embodiment.
FIG. 3 is a flowchart illustrating brake assist control during cold operation in the first embodiment.
FIG. 4 is a map showing a motor drive pattern ratio at the time of cold braking control in the first embodiment.
FIG. 5 is a diagram illustrating a relationship between a driver's depression force and a brake hydraulic pressure according to the first embodiment.
[Explanation of symbols]
1, 2 brake circuit 4 pump 5 inflow valve 6 outflow valve 7 reservoir 8 motor 10 drain circuit 41 suction circuit 43 discharge circuit CU control unit ECU engine control unit MC master cylinder WC wheel cylinder

Claims (1)

Treading force amplifying means for amplifying the treading force of the driver by a negative pressure generated by the internal combustion engine;
A master cylinder that generates a hydraulic pressure in accordance with the driver's treading force amplified by the treading force amplifying means,
A pump driven by a motor and serving as a hydraulic pressure source,
A wheel cylinder that generates a braking force on each wheel by using the master cylinder and the pump as a hydraulic pressure source,
A first brake circuit connecting the wheel cylinder and the pump;
A second brake circuit connecting the master cylinder and the first brake circuit;
A one-way state interposed between the first brake circuit and the second brake circuit to allow only the supply of hydraulic pressure from the first brake circuit side to the second brake circuit side when the master cylinder pressure is generated; A switching valve that establishes a communication state between the first brake circuit and the second brake circuit when the master cylinder pressure is not generated;
Brake control means for controlling the driving of the pump,
In the brake control device provided with
Providing a negative pressure detecting means for detecting a negative pressure generated by the internal combustion engine,
When the detected negative pressure is equal to or lower than a predetermined pressure, the brake control means drives the motor and increases the pressure of the wheel cylinder using the pump as a hydraulic pressure source.

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