JPH04300766A - Brake device for vehicle - Google Patents

Abstract

PURPOSE:To provide a brake device for a vehicle capable of improving operation feeling. CONSTITUTION:It is provided with a brake booster 35 to assist piston drive force in a master cylinder 36, a vacuum pump 38 to generate negative pressure in a vacuum tank 37, and a pump drive control means 40 to drivingly control the vacuum pump 38 so as to conform the negative pressure in the vacuum tank 37 to a prescribed control target value. On the input stage of the pump drive control means 40, a target pressure setting means 10 from which a first setting pressure value, a second setting pressure value, or an intermediate value between the first setting pressure value and the second setting pressure value is output as a control target value of the negative pressure in the vacuum tank 37 according to vehicle speed, is provided side by side.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicular brake system, and more particularly to a vehicular brake system equipped with a brake booster (vacuum booster) often used in electric vehicles and the like.

0002

[Background Art] Generally, in an electric vehicle, the pressing force of the piston of the master cylinder is assisted in front of the master cylinder for transmitting hydraulic pressure to the wheel cylinders provided in the wheel brake units of the front and rear wheels. Brake devices equipped with a brake booster that increases braking force are often used.

FIG. 4 shows an example of this type of brake device. In this figure, when the brake pedal 31 is depressed, the arm 32 moves around the fulcrum 33 as indicated by the arrow in the figure.
This rotation of the arm 32 causes the plunger 34 to move in the direction of arrow B. Due to the movement of the plunger 34, the action of a vacuum valve (not shown) causes
A negative pressure chamber and an atmospheric pressure chamber are defined within the brake booster 35. When the brake pedal 31 is further depressed, the power piston (not shown) moves in the direction of arrow B due to the pressure difference between the negative pressure chamber and the atmospheric pressure chamber, and the push rod provided at the tip of the power piston moves the master cylinder 36.
The piston inside is pressed. In this way, by assisting the pressing force of the piston in the master cylinder 36, hydraulic pressure is transmitted from the master cylinder 36 to the wheel cylinders provided in the wheel brake units of the front and rear wheels (not shown), increasing the braking force. It is now possible to

[0004] Here, the brake booster 35 is connected to a vacuum tank 37 via piping, and a negative pressure is generated in the vacuum tank 37 by the action of a vacuum pump 38. The vacuum pump 38 is controlled by a vacuum controller 40, and the negative pressure in the vacuum tank 37 is -490 mmH.
It is controlled within the range of g to -550 mmHg. Also, the negative pressure inside the vacuum tank 37 is -40
When the temperature is 0 mmHg or less, the vacuum switch 39 is turned off, and the relay coil 41 in the vacuum controller 40 is no longer energized. Therefore, the relay switches 42 and 43 are turned OFF at the same time, and the accelerator signal that is the output of the accelerator device 50 is turned OFF.
OFF", making it impossible to run, and the start indicator light (green lamp) 51 goes out. In this figure, the reference numeral 44 is a vacuum sensor that detects the negative pressure within the vacuum tank 37, the reference numeral 52 is an auxiliary battery, and the reference numeral 53 is an ignition switch.

[0005]

[Problems to be Solved by the Invention] In the above conventional example, the negative pressure in the vacuum tank ranges from -490 mmHg to -5
It is designed to be controlled within a range of 50 mmHg, but since the negative pressure is constant regardless of the driving speed, when driving at low speeds, even if you lightly press the brake pedal, it will cause sudden braking, whereas when driving at high speeds, it will cause sudden braking. There was an inconvenience in that the user had to press hard and the operating feeling was not good.

[0006]

OBJECTS OF THE INVENTION An object of the present invention is to provide a vehicle brake system which can improve the inconveniences of the prior art, provide a suitable braking force regardless of the vehicle's running speed, and improve the operational feeling. It is about providing.

[0007]

[Means for Solving the Problems] The vehicle brake system of the present invention includes a brake booster that assists the driving force of the piston in the master cylinder by the depression force of the brake pedal, and a vacuum tank connected to the brake booster. A vacuum pump that generates pressure and pump drive control means that drive and control the vacuum pump so that the negative pressure in the vacuum tank matches a predetermined control target value are provided. The input stage of the pump drive control means is provided with a first value as a control target value for the vacuum tank internal negative pressure when the vehicle speed is lower than a predetermined lower limit speed.
When the vehicle speed exceeds a predetermined upper speed limit, the second set pressure value is set, and when the vehicle speed is between the upper speed limit and the lower speed limit, the first set pressure value is set. and second
Target pressure setting means for outputting values corresponding to vehicle speeds between the set pressure values are provided. This configuration attempts to achieve the above-mentioned purpose.

[0008]

[Operation] The target pressure setting means outputs a target value of the vacuum tank internal negative pressure according to the vehicle speed, and the pump drive control means drives the vacuum pump so that this target value matches the vacuum tank internal negative pressure. be done.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to FIGS. 1 to 3. Here, the same reference numerals are given to the same or equivalent components as in the conventional example shown in FIG.

FIG. 1 shows the configuration of a brake device according to an embodiment of the present invention. In this figure, a vacuum controller 40 as a pump drive control means includes a differential amplifier 1 mainly composed of an operational amplifier 5, a power transistor 2 for controlling the drive of a motor 38A constituting a vacuum pump 38, and a comparator 3. It is composed of: Of these, the differential amplifier 1 outputs a signal obtained by amplifying the difference between the output of the vacuum sensor 44 and the output of a vacuum pressure setting device constituting target pressure setting means to be described later. The output of the differential amplifier 1 is connected to the base of a power transistor 2, the collector of which is connected to one end of the motor 38A, and the emitter of which is grounded. The other end of the motor 38A is connected to the positive electrode of an auxiliary battery 52 via an ignition switch 53, and the negative electrode of this auxiliary battery 52 is grounded. The comparator 3 uses the output of the vacuum sensor 44 that detects the negative pressure in the vacuum tank 37 as its inverting input, the voltage of the reference voltage source 4 corresponding to the negative pressure of -400 mmHg as its non-inverting input, and its output terminal is It is grounded via a relay coil 41. Therefore, when the negative pressure in the vacuum tank 37 becomes -400 mmHg or less, the output of the comparator 3 becomes "L (low)" and the energization to the relay coil 41 is stopped.

The target pressure setting means 10 includes a comparator 1
1, comparator 12, and these comparators 11
. The comparator 11 takes the output of the F/V converter 13 as its inverted input, and has a predetermined lower limit speed v
1 (for example, 20 km/h)
Let the voltage at its non-inverting input. Also, comparator 1
2 uses the output of the F/V converter 13 as its non-inverting input, and uses the voltage of the reference power supply 16 corresponding to a predetermined upper speed limit v2 (for example, 80 km/h) as its inverting input. F/V
Converter 13 performs frequency/voltage conversion on the output of vehicle speed sensor 17 that detects vehicle speed, and sends a voltage corresponding to the vehicle speed to vacuum pressure setting device 14 . Vacuum pressure setting device 1
Reference numeral 4 is constituted by a so-called microcomputer, which outputs a control target value signal for the negative pressure in the vacuum tank 37 corresponding to the vehicle speed, as will be described later. Other configurations are shown in Figure 4 above.
This is similar to the conventional example.

Next, the overall operation of this embodiment configured in this manner will be explained with reference to the flowchart shown in FIG.

First, a CPU (not shown) in the vacuum pressure setting device 14 constituting the target pressure setting means 10 determines whether the output of the comparator 11 is "L" or not, so that the vehicle speed is 20 km/h or more. Determine whether or not (
Step S101). If the vehicle speed has not reached 20 km/h, the process proceeds to step S106, and the negative pressure control target value is set to -450 mmH, which is the first set pressure.
Outputs the voltage corresponding to g. As a result, the vacuum controller 40 drives and controls the vacuum pump 38 so that the negative pressure in the vacuum tank 37, which is the output of the vacuum sensor 44, matches the negative pressure control target value (
Step S107), the inside of the vacuum tank 37 is -45
The pressure becomes 0 mmHg.

On the other hand, in step S101, the vehicle speed is 20
km/h or more, the process advances to step S102, and the CPU sets the output of the comparator 12 to "H (high)".
” By determining whether the vehicle speed is 80km
/h or less. And the vehicle speed is 80km/
When the vehicle is running at a high speed exceeding h, the CPU proceeds to step S105 and outputs a voltage corresponding to -600 mmHg, which is the second set pressure, as the negative pressure control target value. As a result, the vacuum controller 40 drives and controls the vacuum pump 38 so that the negative pressure in the vacuum tank 37, which is the output of the vacuum sensor 44, matches the negative pressure control target value (step S107), and the vacuum tank 37 The pressure becomes -600 mmHg. On the other hand, in step S102, the vehicle speed is 80 km/h.
If it is less than h, the CPU executes step S103.
Proceed to -450mmHg~ as the negative pressure control target value.
A value corresponding to the vehicle speed, which is the output of the F/V converter 13, is output in the range of -600 mmHg. As a result, the vacuum controller 40 drives and controls the vacuum pump 38 so that the negative pressure in the vacuum tank 37, which is the output of the vacuum sensor 44, matches the negative pressure control target value (step S107), and the vacuum tank 37 -4
The predetermined pressure is in the range of 50 mmHg to -600 mmHg. In this way, the negative pressure within the vacuum tank 37 is controlled according to the vehicle speed, as shown in FIG.

The negative pressure in the vacuum tank 37 is -40
When it becomes 0mmHg or less, the output of comparator 3 becomes “L”.
”, and the relay coil 41 is no longer energized. Therefore, the relay switches 42 and 43 are simultaneously set to "OF".
F", the accelerator signal which is the output of the accelerator device 50 becomes "OFF", making it impossible to drive, and the start indicator light (green lamp) 51 goes out.

As explained above, according to this embodiment,
Since the target pressure setting means 10 and the vacuum controller 40 control the negative pressure in the vacuum tank 37 in accordance with the vehicle speed, it is possible to avoid sudden braking even when the brake pedal 31 is lightly depressed when driving at low speeds. Therefore, it is possible to secure sufficient braking force without having to fully depress the brake pedal 31 when driving at high speed, and as a result, the brakes are operated in an appropriate state regardless of the driving speed, improving the operational feeling. . Further, when the negative pressure inside the tank becomes -400 mmHg or less, such as when the vacuum pump 38 fails, the output of the accelerator device 50 is turned off and the start indicator light 51 is turned off, as in the conventional example. Since this abnormality warning function can be performed without using an expensive vacuum switch, it is possible to reduce costs.

[0017]

As the present invention is configured and functions as described above, the negative pressure in the vacuum tank can be controlled in accordance with the vehicle speed by the action of the target pressure setting means and the pump drive control means. This prevents the brakes from being too effective and causing sudden braking when driving at low speeds, and ensures sufficient braking force when driving at high speeds.
As a result, it is possible to provide an unprecedented and excellent vehicle brake device that can operate the brake in an appropriate state regardless of the traveling speed and can improve the operating feeling.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the embodiment of FIG. 1;

FIG. 3 is a diagram showing vacuum tank internal pressure characteristics according to vehicle speed in the embodiment of FIG. 1;

FIG. 4 is a diagram for explaining a conventional example.

[Explanation of symbols]

10 Target pressure setting means 31 Brake pedal 36 Master cylinder 35 Brake booster 37 Vacuum tank 38 Vacuum pump 40 Vacuum controller as pump drive control means

Claims (1)

[Claims] 1. A brake booster that assists the driving force of a piston in a master cylinder due to the depression force of a brake pedal; a vacuum pump that generates negative pressure in a vacuum tank that is communicated with the brake booster; In a vehicle brake device, the vehicle brake system includes a pump drive control means for driving and controlling the vacuum tank so that the negative pressure in the vacuum tank matches a predetermined control target value, and an input stage of the pump drive control means includes a As the pressure control target value, when the vehicle speed is lower than a predetermined lower limit speed, the first set pressure value is used, when the vehicle speed exceeds the predetermined upper limit speed, the second set pressure value is used. A target pressure setting means is provided which outputs a value corresponding to a vehicle speed between the first set pressure value and the second set pressure value when the speed is between the upper limit speed and the lower limit speed. Brake device for vehicles.