JPH0224258A - Brake servo system for electric automobile - Google Patents

Abstract

PURPOSE:To reduce power consumption in a device equipped with a brake booster using as its drive source pressurized fluid from the pressurizing pump driven by motor, by driving a pressurizing pump through the connection of an electromagnetic clutch when an acceleration pedal is in a released state. CONSTITUTION:In order to supply boosted drive force to a main brake system of an electric automobile, a hydraulic pump 22 driven by means of a drive motor 10 is arranged, so that pressurized oil by the hydraulic pump 22 is supplied to a hydraulic booster 26 via a pipe 24. This pump 22 and the motor 10 are interlocked by means of a belt 42 layed on a pulley 38 equipped with an electronic clutch and a pulley 40. The clutch is controlled by means of a controller 20 to send a connection command from the controller 20 to the clutch when an acceleration sensor 44 detects that an acceleration pedal 46 is released, and to make the motor 10 drive the pump 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a brake servo system for an electric vehicle, and particularly to a control device for a pressurizing pump that is a supply source of pressurized working fluid used in a servo brake.

[Prior Art] Brake systems for electric vehicles are classified into a main brake system operated by a brake pedal, an electric brake system operated by regenerative braking of a drive motor, and a mechanically or electrically driven parking brake system. Of these brake systems, the main brake system is the most important in determining the braking ability during driving.
It is necessary to provide a reliable braking action that matches the driver's braking feeling.

Normally, in order to provide sufficient and reliable braking force to the high output of recent high-performance drive motors, a brake servo system is used for the main brake system, which increases the pressure applied to the brake pedal.

As a pressure increasing medium for such servo brakes, electric vehicles that do not have a negative pressure source, such as gasoline engine vehicles, require a pressure pump for the main brake system (a negative pressure pump for suction types), and this The pressure pump is rotationally driven by the electric vehicle's drive motor. The pressurized fluid from the pressurizing pump is supplied to the booster, and the pedaling force of a brake pedal linked to the booster is applied from the booster to the master cylinder of the brake system as a brake operating force. Hydraulic pressure or pneumatic pressure is used as the pressurized fluid, and sufficient braking force of the main brake system can be obtained.

[Problems to be Solved by the Invention] However, in the conventional brake servo system, the constantly driven motor rotates the pressurizing pump, which reduces the energy efficiency of the electric vehicle and reduces the mileage per charge. There was a problem with this.

As a conventional brake actuation device, Japanese Patent Application Laid-Open No. 58-3955
No. 4 is known, and this device discloses a device in which a motor-driven pump is used as a fluid brake booster, and the pump operates only when the brake is applied, thereby saving the driving force of the motor.

However, in this conventional device, fluid pressure is obtained by braking, so when sudden braking is required, the supply of working fluid pressure to the pump may be delayed relative to the required braking pressure. can be,
There has been a problem in that the main brake system of a motor vehicle cannot provide sufficient and reliable braking action.

In addition, in order to eliminate such delays, the capacity of the pump or booster must be sufficiently large, which increases the size of the device and requires a large driving force to operate the device. There was a problem in that it was not suitable for automobiles that required highly efficient operation, such as cars.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to operate the pressurizing pump only when necessary for braking, and normally stop it so as not to place a load on the drive motor of an electric vehicle. An object of the present invention is to provide an improved brake servo system for an electric vehicle that can supply a sufficient and reliable braking force when the vehicle is in a stable condition and a braking action is required.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an electromagnetic clutch that connects and disconnects the output transmitted from the drive motor to the pressure pump, and an accelerator sensor that detects when the accelerator pedal is released. When the accelerator pedal is released by the accelerator sensor, the electromagnetic switch is switched to the connected state to transmit the output of the drive motor to the pressure pump.

[Function] Therefore, according to the present invention, when the accelerator is depressed and the vehicle is traveling normally, the pressurizing pump is separated from the drive motor and does not impose any load on the drive motor.

As soon as the accelerator pedal is released, the pressurizing pump is connected to the drive motor, supplying the necessary pressurized fluid pressure to the booster, and preparing for braking.

Further, according to the present invention, when the accelerator is released, the pressure pump becomes a mechanical load on the drive motor,
Further, since the load (resistance) increases approximately in proportion to the square of the vehicle speed, it has the advantage that it can perform an action similar to the engine brake in a gasoline engine vehicle.

[Example] Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows the overall control system of an electric vehicle to which a brake servo system according to the present invention is applied, and in this embodiment, the main brake system is shown as a brake system using hydraulic pressure.

As is well known, the rotation of the electric vehicle drive motor 10 is transmitted to the drive shaft via the reducer 12, and the motor 1
By controlling the zero rotational speed or torque, desired power travel or regenerative braking action can be performed.

In order to control the drive motor 10, the voltage of the battery 16 is supplied to the motor 10 via a motor drive circuit 18, which is controlled by a controller 20.

In this embodiment, in order to supply boosted driving force to the main brake system of the electric vehicle, a hydraulic pump 22 driven by the drive motor 10 is provided, and pressurized oil is supplied from the hydraulic pump 22 via a pipe 24. It is supplied to the hydraulic booster 26.

As is well known, the hydraulic booster 26 is connected to the brake pedal 28.
The depression force of the brake pedal 28 is boosted by the booster 26 and supplied to the master cylinder 30. The brake oil pressure generated in the master cylinder 30 is transmitted from the combination valve 32 to the brakes 36 of each wheel via the brake oil pressure piping 34.

A characteristic feature of the present invention is that the hydraulic pump 22 is connected to the drive motor 10 via an electromagnetic clutch. In the embodiment, the hydraulic pump 22 has a pulley 38 with an electromagnetic clutch, and the drive motor 10 pulleys 4
The rotational driving force of the drive motor 10 is transmitted from the drive motor 10 to the electromagnetic clutch pulley 38 via the belt 42.

Therefore, when the electromagnetic clutch pulley 38 is in the engaged state, the rotational driving force of the drive motor 10 is transmitted to the hydraulic pump 22, and pressurized oil is sent to the hydraulic piping 24. However, when the electromagnetic clutch is disengaged, the hydraulic The pump 22 is in a rest state and pressurized oil is supplied, but as a result, the load on the drive motor 10 can be eliminated.

The command to connect and disconnect the electromagnetic clutch pulley 38 is supplied from the controller 20. Therefore, in the present invention, the controller 20 receives information from the accelerator sensor 44 when the accelerator pedal is depressed as information for instructing the connection and disconnection of the electromagnetic clutch. Receives release signal supply. The accelerator sensor 44 detects the release of the accelerator pedal 46, and the controller 20 supplies a command to engage the electromagnetic clutch when the accelerator sensor 44 detects the released state of the accelerator pedal 46.

In this embodiment, the controller 20 also monitors the state of the brake pedal 28. For this purpose, the brake pedal 28 is provided with a brake sensor 48, and when the brake pedal 48 is depressed, the controller 20 also monitors the state of the brake pedal 28. The controller 20 connects the electromagnetic clutch.

FIG. 2 shows an example of the controller 20, which mainly controls the drive motor 10 and the electromagnetic clutch 38.

The controller 20 has a constant voltage power supply circuit 50, which converts the voltage supplied from the battery 16 into a constant voltage and supplies it to each part of the controller.

As is well known, the controller 20 includes a CPU 52 and an R
It is possible to read necessary programs and data from the AM 54 and ROM 56 and output predetermined control signals.

Predetermined control signals are input to the controller 20 from various parts of the automobile, and in order to control the drive motor 10, the rotation speed and other parameters are detected from a well-known sensor (not shown), and each detection signal is sent via the digital input interface 58. The signal is supplied to the data bus 60.

Similarly, the accelerator release signal for controlling the hydraulic pump 22 in this embodiment is transmitted from the accelerator sensor 44.
Further, a brake pedal release signal is supplied from the brake sensor 48 to the analog input interface 62, and the AD
The data bus 60 is converted into a digital signal by the converter 64.
is supplied to

After the CPU 52 performs a predetermined calculation operation, a predetermined control signal is supplied from the output interface 66 to each part of the vehicle, and in the embodiment, the control signal from the output interface 66 is supplied to the motor drive circuit 10 and the electromagnetic clutch 38. ing.

The embodiment of the present invention has the above-mentioned configuration, and its operation will be explained below using the flowchart of FIG.

When the system starts, a switch interrupt (101) is performed at a predetermined period, for example, every 10 milliseconds, and the controller 20 first determines the output of the accelerator switch 44, and determines whether or not the accelerator pedal 46 is released (
102). When the output of the accelerator sensor 44 indicates that the accelerator is released, the controller 20 sends an engagement signal to the electromagnetic clutch 38, and the electromagnetic clutch becomes engaged (103).
The rotational driving force of the drive motor 10 is transmitted to the hydraulic pump 22, and pressurized oil is immediately supplied to the hydraulic booster 26. As long as the accelerator is released, the hydraulic pump 22 continues this pressurizing action.

Therefore, the hydraulic booster 26 can immediately supply the desired braking pressure to the main brake system when the brake pedal 28 is depressed.

On the other hand, if the accelerator sensor 44 determines (102) that the accelerator is depressed, the controller 20 next determines that the brake is released (104). Normally, the brake is released when the accelerator is depressed, so under this condition, that is, when the accelerator is depressed and the brake is released, the electromagnetic clutch 38 is disengaged and the cycle ends.

Therefore, it is understood that under normal running conditions, the electromagnetic clutch 38 is in the disengaged state, the hydraulic pump 22 does not impose any load on the drive motor 10, and the electric power of the battery 16 is effectively utilized.

In step 104, if the accelerator is depressed and the brake is also depressed, for example, when braking and accelerator opening are performed simultaneously when starting a car or cornering at high speed, the brake may be pressed even when the accelerator is depressed. In this embodiment, the electromagnetic clutch 3B is in a connected state, and the hydraulic pump 22 is rotationally driven to supply pressurized oil to the hydraulic booster 26, thereby ensuring the main braking operation.

Further, when the accelerator is depressed and the brake is released, the electromagnetic clutch 38 is activated at step 10 as shown in the figure.
5, the electromagnetic clutch 38, which was engaged when the accelerator was released or the brake pedal was depressed, is switched to the disengaged state, and the load on the drive motor 10 is immediately reduced.

As described above, in this embodiment, the hydraulic pump 22 is rotationally driven by the drive motor 10 only when the accelerator is released or the brake is depressed, and the hydraulic pump 22 is not a load on the drive motor other than that, and energy can be used with high efficiency. There are advantages.

Further, in this embodiment, the pressurized oil of the hydraulic pump 22 is directly supplied to the hydraulic booster 26, and when the hydraulic pump 22 is in a rest state, the pressure of the hydraulic booster 26 decreases. By using a pump with good start-up response, sufficient pressurized oil can be supplied, for example, within about 0.2 seconds from application of a command to engage the electromagnetic clutch 38 from the controller 2o.

Another embodiment of the present invention is shown in FIG. 4, and this embodiment is characterized in that an accumulator 70 is provided in the hydraulic piping 24 to the hydraulic pump 22. is stored in the accumulator 70, and even if the hydraulic pump 22 is in a rest state, the pressurized oil necessary for at least a plurality of braking operations can be supplied from the accumulator 70 to the hydraulic booster 26.

Therefore, according to this embodiment, even when the responsiveness of the hydraulic pump 22 is low, it is possible to sufficiently operate the main brake system of the electric vehicle.

Of course, the output oil pressure of the accumulator 70 also gradually decreases due to leaks from various parts. Therefore, in the second embodiment, the pressure in the accumulator 70 or the hydraulic piping 24 is measured by the oil pressure sensor 72, and this detection signal is sent to the controller 20. By supplying pressure oil to the accumulator 70, the controller connects the electromagnetic clutch 38 regardless of the accelerator or brake state when the oil pressure falls below a certain lower limit value, and supplies desired pressure oil to the accumulator 70.

Further, when the oil pressure exceeds a predetermined upper limit value, the controller 20 disconnects the electromagnetic clutch 38 and prevents the supply of pressurized oil, regardless of the state of the accelerator or brake described above.

In the embodiments described above, hydraulic pressure is used as the boosting fluid, but in the present invention, it is of course possible to use other fluids such as air pressure as pressurization or negative pressure.

[Effects of the Invention] As explained above, according to the present invention, the pressurizing pump is put into a rest state during normal driving, reducing the load on the drive motor, increasing the mileage of the electric vehicle per charge, and improving energy efficiency. It has the advantage of improving

Furthermore, since the hydraulic pump is operated immediately when the accelerator is released and supplies pressurized fluid to the booster, it is possible to perform sufficient and reliable braking when braking is required.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a preferred first embodiment of the brake servo system for electric vehicles according to the present invention, FIG. 2 is an explanatory diagram showing an example of the controller in FIG. 1, and FIG. FIG. 4 is a flowchart diagram showing the operation of the embodiment. FIG. 4 is an overall drive control configuration diagram of an electric vehicle showing another embodiment of the present invention. 10... Drive motor 16... Battery 18... Motor drive circuit 20... Controller 22... Hydraulic pump 44... Accelerator sensor 46... Accelerator pedal

Claims (1)

[Scope of Claims] A pressurizing pump that is rotationally driven by a drive motor of an electric vehicle and supplies pressurized fluid, and the pressurized fluid is introduced and works in conjunction with a brake pedal to provide a brake operating force to a master cylinder of a brake system. A brake servo system for an electric vehicle that increases the pressure on the brake pedal and transmits the pressure to the brake system, including a booster, an electromagnetic clutch that connects and disconnects the output transmitted from the drive motor to the pressure pump, and an accelerator pedal. An electric vehicle comprising: an accelerator sensor that detects a pedal release; and when the accelerator pedal is released by the accelerator sensor, the electromagnetic switch is switched to a connected state to transmit the output of the drive motor to a pressure pump. brake servo system.