JPH0629031B2 - Motor drive type power steering control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive type power steering control device for energizing a steering device of an automobile with an auxiliary load by a rotational force of a motor.

[Prior Art] Conventionally, a motor-driven power steering control device of this type has a structure in which a driving force of a motor is urged by an auxiliary load to a steering shaft or a rack shaft by a transmission mechanism such as a gear or a belt via a reduction gear. Is.

[Problems to be solved by the invention]

However, in the conventional motor-driven power steering control device, the wiring is burned or the battery cannot be used in the event of an abnormality such as a short-circuit of the power element that constitutes the power element section that controls the electric current flow and direction of the motor. Had the drawback of inviting.

This invention has been made to solve such a problem, and can prevent the wiring from being burnt out at an abnormal time such as when a power element is short-circuited, or preventing the battery from becoming unusable, without enormous cost up. An object of the present invention is to obtain a motor-driven power steering control device with high safety.

[Means for solving problems]

The motor-driven power steering control device according to the present invention determines as abnormal when the difference between the steering wheel torque to the motor and the instruction current value corresponding to the vehicle speed and the actual motor current value is equal to or more than a predetermined value. The above-mentioned problem is solved by means for turning off the power element in the power element section including the power element of No. 4.

[Action]

In the present invention, when the difference between the instruction current value and the actual motor current value is equal to or larger than the predetermined value, it is determined to be abnormal, and the power element is turned off to cut off the current supplied to the motor.

〔Example〕

An embodiment of a motor-driven power steering control device of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of the embodiment.

In FIG. 1, reference numeral 1 is a steering wheel that receives a steering rotational force of a driver, and 3 is a torque sensor that outputs an electric signal in accordance with the rotational force applied to the steering wheel 1.

Between the steering wheel 1 and the torque sensor 3, the steering wheel 1 is connected to the first steering shaft 2a via the first steering shaft 2a.
Of the universal joint 4a, and the first universal joint 4a is connected to the second universal joint 4b via the second steering shaft 2b. The second universal joint 4b is connected to the torque sensor 3 via the third steering shaft 2c.

The torque sensor 3 is connected to the speed reducer 16 via the fourth steering shaft 2d. The output of the torque sensor 3 is the steering torque measuring means 9 in the control unit 9.
a (described later with reference to FIG. 2).

The reduction mechanism 16 is inserted between the electromagnetic clutch 15 and the pinion shaft 5. The pinion shaft 5 meshes with the rack tooth portion 6 a of the rack shaft 6.

Both ends of the rack shaft 6 are respectively ball joints 7a, 7a.
It is connected to the tie rods 8a and 8b via b.

On the other hand, 12 is a vehicle battery. The negative electrode of the battery 12 is grounded, and the positive electrode is connected to the control unit 9 via the key switch 13 and directly connected to the control unit 9.

The output of the vehicle speed sensor 10 is also input to the control unit 9.
Controls the drive of the motor 14 and the electromagnetic clutch 15.

The electromagnetic clutch 15 can connect or disconnect the mechanical connection between the motor 14 and the speed reducer 16 according to the instruction of the control unit 9.

FIG. 2 is a configuration diagram showing a specific configuration of the control unit 9 of the embodiment shown in FIG. In FIG. 2,
Reference numeral 9a is a steering torque measuring means for measuring a steering torque by the input from the torque sensor 3, and 9b is a vehicle speed sensor 1.
It is a vehicle speed measuring means for inputting an output from 0 to measure the vehicle speed.

The steering torque measuring means 9a and the vehicle speed measuring means 9b are connected in cascade, and the output of the vehicle speed measuring means 9b is sent to the motor current measuring means 9c.

The current measuring means 9c inputs the corresponding voltage due to the current flowing from the current sensor 9j described later and inputs the corresponding voltage to the motor 14 described above.
It is to measure the energizing current to.

The motor current storage means 9d stores and holds the steering torque and the current value of the motor 14 corresponding to the vehicle speed.

Normally, the value stored and held in the motor current storage means 9d is determined as the value read by the motor current determination means 9e, and when the output of the power element short circuit determination means 9f in the next stage is a short circuit output, it is set to zero. The motor current determining means 9e is the motor 1
The current of 4 is decided.

The power element short circuit judging means 9f constitutes the power element section 9i when the motor current measurement value by the motor current measuring means 9c is the command current or more and the difference is the predetermined value or more in response to the instruction of the energizing current to the motor 14. The power elements 9i _{1 to} 9i ₄ are judged to be short-circuited and output.

The electromagnetic clutch control means 9g controls to connect or disconnect the electromagnetic clutch 15 depending on at least the condition determined by the vehicle speed and the output condition of the power element short circuit determination means 9f.

Based on the output of the motor current determination means 9e, the power element section control means 9h instructs the power element section 9i to drive the motor 14
An on / off instruction for controlling the energizing direction and energizing current value is given.

Based on the output of the power element section control means 9h, the power element section 9i controls the current direction and current value of the motor 14, and the power element section 9i controls the motor 1
4 is composed of power elements 9i _{1 to} 9i ₄ which are configured in a bridge circuit so that the power feeding direction can be switched.

The value of the current flowing through the power element portion 9i is the current sensor 9j.
I try to measure at.

A voltage corresponding to the current flowing through the current sensor 9j is applied to the motor current measuring means 9c.

Next, the operation of the above embodiment will be described with reference to FIGS. FIG. 3 is a diagram showing control characteristics of steering torque versus motor current, FIG. 4 is a diagram showing control characteristics of vehicle speed versus motor current and electromagnetic clutch applied voltage, and FIG. 5 is a flow chart showing a control program of the control unit 9. Is.

First, at the time of starting the engine, step S1 in FIG.
Initialize with, and turn on the key switch 13,
The electromagnetic clutch 15 is turned on, and the motor 14 and the speed reducer 16 are mechanically connected.

When the driver applies a rotational force to the steering wheel 1 in this state, the control unit 9 causes the motor 1 to move as shown in FIG.
The steering torque measuring means 9a receives the output of the torque sensor 3 and measures the steering torque TS at step S2.

In FIG. 3, when the steering torque is increased to the right, a
At this point, the motor 14 is turned on, and in order to reduce the influence of the inertia of the motor 14 and the mechanical system, a current of I _OF is supplied to the motor 14 and the motor current I _MS Is measured (step S4).

Further, the steering torque is increased and the motor current is linearly increased with respect to the steering torque from the point b, and 100% is obtained at the point c.
It becomes an electric current.

On the contrary, when the steering torque is reduced and the steering torque is reduced from the point c, the motor current is reduced to a motor current value of I _{OF at} the point b.

When the torque further decreases to point a, the motor 14 is turned off. In this case, substantially the same control is performed even in the leftward direction.

The relationship between the transmission torque and the motor current is proportional. Therefore, when the torque increases in FIG. 3, the motor 14 is turned on at the point a and the motor current of I _OF flows.

Further, when the torque is increased, the current of the motor 14 is gradually increased from the point b, so the output torque to the speed reducer 16 is gradually increased, and the output torque to the reducer 16 is increased according to the driver's force applied to the steering wheel 1. Auxiliary torque is electromagnetic clutch 1
5, the reducer 16, and the pinion shaft 5 through the rack tooth portion 6
tell a.

Therefore, the handle 1 becomes lighter. The above is the description of the stop operation of the vehicle of the present invention.

Next, when the vehicle is in a running state, the vehicle speed measuring means 9b measures the output of the vehicle speed sensor 10 in step S3,
At step S4, the motor current is measured, and as shown in FIG. 4, the motor current determination means 9e reads out the current I _MI stored and held in advance in the motor current storage means 9d according to the steering torque and the vehicle speed. , The current I _MI controls the motor current.

The value of the current I _MI takes a value according to only the steering torque up to the vehicle speed at the point d, and a value corresponding to the steering torque after the point d,
The value is reduced to a value obtained by multiplying the damping rate according to the vehicle speed, and after the vehicle speed at point e (vehicle speed = assist decrease vehicle speed V ₂ ), a constant value I _OF is set to reduce the influence of the inertia of the mechanical system.

Next, the vehicle speed is f point {vehicle speed = assist cutoff vehicle speed V ₁ (V ₁ >
When a value of V _2)}, the motor current I _M and the electromagnetic clutch applied voltage EV are both zero, and the the motor 14 and speed reducer 16 is disengaged, the the connexion the driver to turn the steering wheel 1, energizing auxiliary loads There will be no steering.

However, in the conventional device, when the power elements 9i _{1 to} 9i ₄ forming the power element portion 9i are short-circuited, the wiring is burned or the battery rises.

Therefore, in the present invention, when energization command of the motor current, the motor current I _MS detected by the current sensor 9i In step S6, the command current I _MO above, the difference is the predetermined value I _OV
In the above case, the power element short-circuit determination means 9f determines that the power element is short-circuited. At the time of power element short circuit judgment,
In steps S7 and S8, the power element section control means 9 is provided.
The motor 14 is controlled by turning off the power element by h.
Current and the voltage applied to the electromagnetic clutch 15 are controlled to zero so that the auxiliary load is not energized.
At 9, the motor current instruction value I _M is stored in I _MO .

If the motor current is greater than or equal to the command current and the difference is less than or equal to the predetermined value in step S6, the vehicle speed V is higher than the assist cutoff speed V ₁ in step S10, that is, V> V ₁
If, performs the processing of step S7~S9, V> V ₁ if not, the process proceeds to step S11.

In step S11, the vehicle speed V is reduced by the assist vehicle speed V ₂ (V ₁ >
If it is not more than V ₂ ), in step S12, the motor current I _M
At the same time as I _M1 , the electromagnetic clutches are coupled in step S13, and the processing in step S9 is performed.

If V> V _{2 is} not satisfied in the relationship between the vehicle speed V and the assist decrease vehicle speed V ₂ in step S11, the motor current I _{M is set} to I _OF in step S14, and the processes of steps S13 and S9 are performed.

〔The invention's effect〕

As described above, according to the present invention, when the difference between the motor command current value and the actual motor current value is greater than or equal to a predetermined value, it is determined to be abnormal, and the power element is turned off.
It is possible to prevent the wiring from being burnt out and the battery from becoming unusable at the time of the above abnormality, and it is possible to improve safety.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of a motor drive type power steering control device of the present invention, and FIG.
FIG. 3 is a configuration diagram showing a specific configuration of a control unit of one embodiment of the present invention, FIG. 3 is a control characteristic diagram of steering torque vs. motor current for explaining the above embodiment, and FIG. FIG. 5 is a control characteristic diagram of the vehicle speed vs. motor current and the voltage applied to the electromagnetic clutch, and FIG. 5 is a flow chart of the control program of the embodiment. 1 ... Steering wheel, 3 ... Torque sensor, 9 ... Control unit, 9a ... Steering torque measuring means, 9b ...
Vehicle speed measuring means, 9c ... Motor current measuring means, 9d.
Motor current storage means, 9e ... Motor current determination means, 9
f ... Power element short circuit determination means, 9g ... Electromagnetic clutch control means, 9h ... Power element section control means, 9i ... Power element section, 9j ... Current sensor. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (2)

[Claims] 1. A torque sensor for detecting a turning force of a steering wheel of an automobile, a motor fed from an on-vehicle battery, a means for instructing an energization command current value of the motor based on signals of the torque sensor and the vehicle speed sensor, A power element section including first to fourth power elements configured in a bridge circuit so that the power feeding direction of the motor can be switched, the motor is controlled based on the command current value, and the command current value of the motor and the actual motor A motor drive type power steering control device comprising means for turning off the power element, which is determined to be abnormal when the difference between the current values is a predetermined value or more. 2. The control unit includes a power element section for controlling a current value and a current flowing direction to the motor,
A current sensor that is inserted in series with the power element unit to detect a current flowing to the motor, a motor current measuring unit that measures a current flowing to the motor by the current sensor, and the motor when a current is supplied to the motor. When the motor current measured by the current measuring means is greater than or equal to the command current and the difference is greater than or equal to a predetermined value, a power element short-circuit determination means for determining a power element short-circuit and an output condition of the power element short-circuit determination means The motor-driven power steering control device according to claim 1, further comprising a power element control unit that outputs a control output that turns off the power element.