JPS6067262A - Motor-driven power steering controller - Google Patents

Abstract

PURPOSE:To prevent the spreading of trouble even if a gate control circuit is erroneously operated, by noise, by always applying voltage into the contact point between the terminal of a motor and the contact of a normal/reverse revolution relay through a resistor having a prescribed resistance value. CONSTITUTION:A transistor 21 is biased in the normal direction by resistors 37 and 38, and when a key switch 2 is turned ON, the transistor 21 is put into electric conduction, and a relay 20 is closed to supply electric power for a power steering system. When anomaly is generated in the contacts 4-7 of a normal/reverse revolution switching relay, and a trouble due to welding etc. is generated among said contacts, the relay 20 is necessarily put inoperative, and a contact 2a is opened to cut-off the supply of electric power. Therefore, the spreading of the trouble such as destruction of a power transistor 8 is prevented.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a power steering system for an automobile or the like in which the steering force of the steering wheel is assisted by an electric motor, and particularly relates to a power steering system for an automobile or the like in which steering force is assisted by an electric motor. Concerning protection systems.

[Background of the invention]

The so-called power steering system is one of the various auxiliary devices that reduce the steering force of an automobile and make driving operations safer and more nimble.

In recent years, as the reliability of electric devices and electronic components has improved, so-called electric power steering systems (Japanese Patent Laid-Open No. 57-772
57 (see Publication No. 57, etc.) have been put into practical use, and have been attracting attention in terms of size, weight, and cost reduction.

By the way, in such an idle power steering system, a relay is generally used to control switching of the rotational direction of the electric motor. This is because the power transistor for controlling the current of the motor will be destroyed if the contacts are exposed to hot water.

FIG. 1 shows an example of a conventional electric power steering control device.

In this figure, 1 is a battery for power supply, 2 is a key switch, 3 is a permanent magnet field type DC motor for assisting steering force, 4 to 7 are contacts of the forward/reverse switching relay, and 8 is a current for the motor 3. A power transistor for control, 9 a protection diode, 1O a current detector, 11 a gate control circuit, and 12 a sensor for detecting the difference between the steering angle of the steering wheel and the steering angle of the turning wheel.

Contacts 4 to 7 of the relay are controlled by a gate control circuit 11. For example, when the motor 3 is rotated in the forward direction, contacts 4 and 7 are closed, and when the motor 3 is rotated in the reverse direction, contacts 5 and 6 are closed. and 7, and 5 and 6 operate in pairs.

The power transistor 8 is controlled on and off by a gate control circuit 11, and the current flowing to the motor 3 is controlled by the on/off duty ratio, so-called chopper control.

The gate control circuit 11 is operated by a signal from the sensor 12, and when the difference between the steering angle of the steering wheel and the steering angle of the wheels becomes a predetermined value or more, the contacts 4 to 7 are closed as described above, and the power transistor 8 is connected to the gate control circuit 11. The electric motor 3 is rotated in a predetermined direction by supplying an on/off signal to perform steering assistance. At this time, the duty ratio of the ON/OFF signal is changed according to the information from the current detector 10, and the torque of the electric motor 3 is controlled to a predetermined value.

According to such an electric power steering system, it is smaller than the conventional hydraulic type by 14 fi -t, and it is easy to combine with the steering mechanism of a normal automobile, and the steering characteristics can be easily controlled. On the other hand, if the contact points 4 to 7 of the relay are contaminated as described above, the power transistor 8 will be exposed to the voltage 1. The disadvantage is that voltage is applied directly to it, causing it to break down in a short period of time.

[Purpose of the invention]

It is an object of the present invention to eliminate the drawbacks of the prior art described above, to prevent power transistors from being destroyed even if hot deposits occur on the contacts of a forward/reverse switching control relay, and to prevent 1M, 11JJJ 2 (provides a power steering control device).

[First aspect of the invention] In order to achieve this object, the present invention provides a method in which a voltage is constantly applied to a connection point between a terminal of a motor and a contact of a forward/reverse relay through a resistor having a predetermined resistance value. Check the voltage at the connection point at the timing when the relay contact should normally be open, and if the voltage at this time is outside of a predetermined range, it is assumed that the contact has leaked and the circuit from the battery is cut off. It is characterized by the following points.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electric power steering control device according to the present invention will be described in detail below with reference to illustrated embodiments.

FIG. 2 shows an embodiment of the present invention, in which 20 is a relay, 203 is a contact thereof, 21 is a transistor for controlling the relay 20, 22 is an SC circuit, 23 and 24 are comparators, 25
~31 is a diode, and 32 to 52 are resistors. In addition,
The rest is the same as the conventional example shown in FIG.

Transistor 21 is forward biased by resistor 37,38 and is therefore forward biased by key switch 2.
When the transistor 21 is turned on, the transistor 21 conducts, and the relay 20 closes its contact 20a and operates to supply power to the power steering system.

The set 22 becomes conductive when a signal is supplied from the comparator 23 or the unit 24 via the diodes 29 and 30,
Turn off the conducting transistor 21 and turn off the relay 2.
0 contact 20a is opened.

The comparators 23 and 24 are each composed of an operational amplifier with a light positive feedback of 45 and 46 resistors.
Reference voltages V- and Vb are supplied by 7.48 and 49.50. By establishing the relationship (V->Vb) between this reference voltage (2) and V'b, the entire system operates as a window comparator, and the input voltage Vx
, Vr respectively satisfy the following relationships.

■! It operates so that the necessary pressure to generate I and trigger 5CII, 22 is supplied to its gate.

V'-(Vx<Vb''-=(1,)V,<V
y <Vb ・・・・・・・・・(2) Resistors 32 and 33
．． 34 and 35, as well as the resistor 36, are the voltage V x that appears at the terminals of the motor 3 when all contacts 4 to 7 of the forward/reverse switching relay are closed.

It functions to make Vy a voltage that satisfies the following equation.

V,';>Vxo)Vb--"'f3)v,>
Vyo)Vb ・---------・(4) Here, 'V
xo and Vyo are the terminal voltages of the motor 3 when all the contacts 4 to 7 are closed.

Note that the resistance values of these resistors 32 to 36 and L7 are set to 1, for example, the voltages Vxo and Vyo 7Ji are each about 1/2 of the voltage of the battery 1, and
In order to suppress the power consumption by these resistors fL and others, it is preferable to set it to several K10 or more, for example.

Diodes 25 and 26, 27 and 28, and 29 and 30
i! , J'L each operate as an analog OR gate.

By the way, the sensor 12 detects the difference in angle between the steering wheel and the turning wheel, and when this angle difference exceeds a predetermined value, it generates a detection signal and supplies it to the gate control circuit 1. This is the same as the conventional example shown in FIG.
It is configured to generate a detection signal for keeping the gate potential at t22 at the ground potential simultaneously with the detection signal for the gate control circuit 11 described above.

Next, the operation of this embodiment will be explained.

When the key switch 2 is closed, a pace current is supplied to the transistor 21 via the resistor 37, which makes the transistor 21 conductive and operates the relay 20. The contact 20a is closed and the power steering system is supplied with operating power. is given, and stone production becomes possible.

Therefore, the gate control circuit 11 turns on/off contacts 4 to 7 and controls the power transistor 8 according to the detection signal from the sensor 2, and rotates the electric motor 3t in a predetermined direction to exert a power assist effect on the steering operation. have them do it.

On the other hand, in parallel with this, the comparators 23 and 24 perform a detection operation using the terminal voltages Vx and Vy of the motor 3 as input, and the voltages VX and VY are as described in (1) above.

Every time the equation (2) is satisfied, the output voltage ■A or Vm is generated, and the SC 22'! il-attempt to trigger.

By the way, these voltages Vx and Vy are as described above (31) when all contacts 4 to 7 of the forward/reverse switching relay are open.
, resistors 32 to 36 so that the voltage satisfies equation (4).
As it is stipulated by
It is when any one of the contacts 4 to 7 of the forward/reverse switching relay is closed that the output voltage Va is generated.

Now, let's assume that the contacts of the forward/reverse switching relay have no abnormality due to bathing, etc., and are operating normally. Then, if any of these contacts 4 to 7 are closed, the sensor 12 will detect it. This is limited to the state in which a signal is generated and the gate of the SCR22 is kept at ground potential via the diode 31. Therefore, even if the comparators 23 and 24 generate the output voltages VA and V11 at this time, the 8 Cl (22 is not triggered and the power steering system simply continues to operate under normal conditions.

Next, it is assumed that any one of the contacts 4 to 7 of the forward/reverse switching relay remains closed due to some reason such as contact wear.

Then, this contact that remains closed will be connected to sensor 2.
It will not open even if the detection Iha issue is not generated,
Therefore, the output voltage VA from comparators 23 and 24VC
, V! + appears regardless of the generation of the detection signal from the sensor 12, and the output voltages VA and Vl appear even when the diode 31 is not conductive due to the detection signal from the sensor 12.

As a result, 5CR22 is triggered to the on state by either or both of the output voltages V^, Vs, reducing the base voltage of transistor 21 to approximately ground voltage, turning off this transistor 21, thereby turning off all relays 20. It returns to the non-operating state and contacts 2a'&- open.

Therefore, according to this embodiment, when an abnormality occurs in the contacts 4 to 7 of the forward/reverse switching relay, and even one of them has a failure due to bathing, etc., the relay 20 is always deactivated. Since the contact 2a opens and the power supply is cut off, it is possible to prevent a failure such as destruction of the power transistor 8 from spreading.

Note that the internal resistance of the electric motor 3 is sufficiently small compared to the resistances 32 to 36 and can be ignored in practical terms, so the resistance is 32.3.
3 and either one of the resistors 34 and 35 may be omitted, and furthermore, only one of the voltages Vx and Vy may be detected by all the wind cooperators/parators, and in either case, the above implementation is possible. Example and tl can obtain similar effects.

〔Effect of the invention〕

As explained above, according to the present invention, even if the contacts of the forward/reverse switching relay are stained due to malfunction of the shift gate control circuit due to noise, it is possible to completely prevent the damage from spreading. Therefore, it is possible to eliminate the drawbacks of the prior art and easily provide a highly reliable control device with sufficient power transistor protection.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional example of a t-dynamic power steering control device, and FIG. 2 is a circuit diagram showing an embodiment of an electric power steering control device according to the present invention. l...Battery, 2...Key switch, 3...
Electric motor, 4 to 7... Forward/reverse switching relay contact, 8...
・Power transistor, 10...Current detector, 11・
...Gate control circuit, 12...Sensor, 20...Relay, 21...Control Figure 2

Claims (1)

[Claims] 1. In a power steering system in which the rotational direction of the electric motor for steering force assist is controlled by four bridge-connected relay contacts, a resistor with a predetermined resistance value is connected to the connection point between the electric motor and the relay contacts. A means for applying a predetermined voltage is provided to detect the voltage appearing at the connection point when the deviation between the steering wheel steering angle and the wheel running angle is less than a predetermined value, and when it is outside the predetermined range, An electric power steering control device characterized by being configured to cut off a circuit between an electric motor and a power source.