KR20040091432A - Device for driving solenoid valve in a vehicle - Google Patents

Abstract

PURPOSE: A solenoid valve driving device is provided to prevent a solenoid driving switch from being broken down by dark currents by bypassing the dark currents with back electromotive force generated by a solenoid coil. CONSTITUTION: A solenoid valve driving device is composed of a brake pressure-control solenoid valve having solenoid coils(L1¯L8) therein and opening or closing a brake fluid passage by operating a plunger according to electric currents flowing through the coils and a driving unit(30) for driving the solenoid valve. The driving unit comprises a fail safe switch(Q0) for cutting off the supply of power toward the solenoid coil; solenoid driving switches(Q1¯Q8) for switching the electric currents flowing through the solenoid coil; and at least one bypass unit(40) for bypassing the electric currents by back electromotive force generated by the solenoid coil in operating the fail safe switch.

Description

Solenoid valve driving device {Device for driving solenoid valve in a vehicle}

The present invention relates to a solenoid valve driving apparatus, and more particularly to a solenoid valve driving apparatus for driving a solenoid valve for adjusting the brake pressure of a wheel cylinder provided in a vehicle.

In general, in a vehicle equipped with a vehicle brake system such as an anti-lock brake system (hereinafter referred to as ABS) or a brake traction control system (hereinafter referred to as BTCS), the wheel cylinder of each wheel is used. By reducing, maintaining, or increasing the brake hydraulic pressure applied to the vehicle, the steering stability is secured and the steering is stabilized. In such a vehicle brake system, a solenoid valve is provided on the hydraulic line on the inflow or outflow side of each wheel cylinder to adjust the brake hydraulic pressure in each wheel cylinder.

Conventionally, the solenoid valve is connected to a MOSFET in series so that the current by the battery flows or is blocked in the coil in the solenoid valve as the MOSFET is turned on or off to control the operation of the solenoid valve.

However, in recent years, a technique for one-chip driving a solenoid valve driving driver into an ASIC circuit has been proposed to reduce the size of a brake module such as ABS or TCS.

However, when the current is applied to the solenoid coil and then shut off, the solenoid coil generates instantaneous back electromotive force ranging from tens to hundreds of volts. That is, in an inductive load such as a solenoid coil, the current does not change instantaneously. If the current is cut off, the voltage corresponding to that is induced by the following equation.

E = -L (di / dt) [V]

(Where E is the counter electromotive force and L is the rate of change of current with respect to inductance di / dt time.)

Conventionally, since the dark current caused by the back electromotive force is divided by each critical component in the driving driver, a certain amount of protection is provided through self-heating. However, when one chip is made in the ASIC circuit, all the critical components are included in one element. Since the protection function cannot be performed through heat generation, the driving switch may be damaged by a relatively high dark current.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a solenoid drive device for preventing the solenoid drive switch from being damaged by back electromotive force generated by the solenoid coil.

1 is a control circuit diagram illustrating a solenoid driving device according to an embodiment of the present invention.

FIG. 2 is a view for explaining an operation of bypassing a dark current caused by back electromotive force generated by the solenoid coil of FIG. 1.

* Description of the symbols for the main functions of the drawings *

10 control unit 20 fail safe relay driving unit

30: solenoid valve drive unit

L1 to L8: solenoid coil

Q0: Failsafe Switch

Q1 to Q8: Solenoid Drive Switch

D10: Dark Current Protection Diode

B +: Battery

Solenoid valve driving apparatus according to the present invention for achieving the above object has a solenoid coil in its own, the brake pressure control solenoid valve for opening or closing the brake fluid flow path by the plunger according to the current flowing through the coil, the solenoid A solenoid valve drive device having a drive device for driving a valve, the drive device comprising: a fail-safe switch for shutting off power supply to the solenoid coil, a solenoid drive switch for switching a current flowing in the solenoid coil, and At least one bypass unit for bypassing the current caused by the back electromotive force generated by the solenoid coil when the fail-safe switch is operated.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

1 is a control circuit diagram illustrating a solenoid driving device according to an embodiment of the present invention. As shown in FIG. 1, the coils L1 to L8 in each solenoid valve provided on the inlet or outlet side of the wheel cylinder to adjust the brake pressure of the wheel cylinder are configured to receive a predetermined current from the battery. Solenoid drive switches Q1 to Q8 are provided at the rear ends of the solenoid coils L1 to L8. Each solenoid coil and a solenoid driving switch form a pair, and a pair of solenoid coil and a solenoid driving switch are connected in parallel with each other.

The solenoid driving switches Q1 to Q8 are formed of low side MOSFETs. As the MOSFETs are turned on or off, current is supplied or cut off to the solenoid coils L1 to L8 to open or close the solenoid valves. The low sipe MOSFET is operated by the solenoid valve driver 30.

In addition, in order to prevent damage to the solenoid coils L1 to L8 during fail safe, such as when the solenoid coils L1 to L8 may be damaged by excessive current, at the front end of each solenoid coil L1 to L8. A fail-safe switch Q0 called a fail-safe relay FSR is provided. The fail safe switch Q0 is operated by the fail safe relay driver 20.

The fail safe relay driver 20 and the solenoid valve driver 30 are driven by a controller 10 including a microcomputer. At this time, the controller 10 PWM-drives the solenoid valve drive unit 30 for the solenoid drive switches Q1 to Q8 by using a pulse width modulation (PWM) control method.

When each of the pair of solenoid coils and the solenoid driving switch is cut off in parallel with the current flowing in the solenoid coil, a bypass unit 40 is provided for bypassing the dark current caused by the counter electromotive force generated by the solenoid coil. The bypass portion 40 is composed of a diode D10, and the cathode C in the diode D10 is connected to the ground side.

Looking at the operation of the controller, the controller 10 turns on or off the desired solenoid drive switches Q1 to Q8 through the solenoid valve driver 30. The fail-safe control unit 10 turns off the fail-safe switch Q0 through the fail-safe relay driver 20 to prevent current from the battery B + from flowing through the solenoid coils L1 to L8. At this time, the dark current caused by the counter electromotive force generated by the solenoid coils L1 to L8 is bypassed through the bypass unit 40.

Hereinafter, a process of releasing dark current caused by back electromotive force generated by the solenoid coil which is an inductive load by turning off Q0 during fail safe will be described.

FIG. 2 is a view for explaining an operation of bypassing a dark current caused by back electromotive force generated by the solenoid coil of FIG. 1. Referring to FIG. 2, when the fail safe switch Q0 is turned off while the solenoid driving switch Q1 is on, a counter electromotive force is generated by the solenoid coil L1 which is an inductive load, and the counter electromotive force is relatively large. Dark current flows. However, due to the dark current protection diode D10, such a dark current is circulated and circulated in the direction of the arrow so that the solenoid driving switch Q1 is driven by the resistance component in the solenoid coil L1 and the solenoid driving switch Q1. It is not broken.

As described above in detail, the present invention has an effect of preventing the solenoid driving switch from being damaged by the dark current by bypassing the dark current caused by the counter electromotive force generated by the solenoid coil.

Claims (4)

A solenoid valve driving apparatus having a solenoid coil in itself, a brake pressure control solenoid valve for opening or closing a brake fluid flow path according to a current flowing through the coil, and a driving device for driving the solenoid valve. The driving device is a fail-safe switch for shutting off power supply to the solenoid coil, a solenoid driving switch for switching a current flowing through the solenoid coil, and a reverse electromotive force generated by the solenoid coil when the fail-safe switch is operated. And at least one bypass portion for bypassing current. The solenoid valve driving apparatus of claim 1, wherein the bypass unit is connected in parallel with the solenoid coil and the solenoid driving switch. The solenoid valve driving apparatus according to claim 1 or 2, wherein the bypass unit is a diode having a cathode connected to the ground side. The solenoid valve driving device according to claim 1, wherein the driving device is composed of one chip using an ASIC.