JPH069970B2 - 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-driven power steering control device for assisting a steering device of an automobile with a motor rotational force.

[Conventional technology]

Conventionally, this type of power steering apparatus assists the driving force of a motor to a steering shaft or a rack shaft by a transmission mechanism such as a gear or a belt via a speed reducer.

[Problems to be solved by the invention]

In the conventional power steering device as described above, when the motor or the mechanical system is locked, it cannot be distinguished from the vicinity of the steering lock, so that the motor and the power element for controlling the motor are continuously heated. There was a risk that it could be destroyed by the temperature rise, or steering could not be performed due to a mechanical lock, leading to an accident.

The present invention has been made to solve the above-mentioned problems, and prevents damage to the motor and the power element due to a temperature rise, and enables steering even when mechanically locked, reducing steering discomfort. It is an object of the present invention to obtain a motor drive type power steering control device having high reliability and high safety.

[Means for solving problems]

A power steering control device according to the present invention includes a steering torque measuring means for measuring a steering torque by an input from a torque sensor, a vehicle speed measuring means for measuring a vehicle speed, and a front wheel at the time of steering a steering wheel by an input from a lock position detecting sensor. Lock position detection means for detecting the left and right lock positions, and if the output from this lock position detection sensor is other than the lock position and the motor current instruction value corresponding to the steering torque is equal to or greater than a predetermined current value, it is determined that the motor current is abnormal. A motor current abnormality determining means for outputting, a motor current determining means for determining the motor current to a value usually according to the steering torque, and a motor current determining means for determining the motor current to zero when the output of the motor current abnormality determining means is an abnormality determination output, Motor current control means for controlling the motor current based on the output of the current determination means.

[Work]

According to the present invention, when the steering wheel becomes heavy due to the destruction of the motor or the power element due to heat generation, or the steering wheel becomes heavy due to mechanical locking, the locking of the motor and the mechanical system by the lock position detection sensor and steering near the steering wheel lock position. By identifying and setting the motor current to zero,
This prevents damage to the motor and power element due to temperature rise, and enables steering even during mechanical lock, ensuring highly reliable and safe driving.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
FIG. 1 is a configuration diagram including a block circuit diagram of a motor drive type power steering control device according to the present invention,
In the figure, 1 is a steering wheel that receives a steering torque of a driver, 3 is a torque sensor that outputs a signal according to the torque applied to the steering wheel 1, 4a is a first universal joint, and 4b is a second universal joint. The joint 2a is a first steering shaft connecting the handle 1 and the torque sensor 3 to each other, 2b is a second steering shaft connecting the torque sensor 3 to the first universal joint 4a, and 2c is a first universal joint 4a. And a second universal joint 4b, a third steering shaft, 5 is a first pinion shaft connected to the second universal joint, and 6 is a first rack tooth portion 6a meshing with the pinion shaft 5. A rack shaft having a second rack tooth portion 6b, 7a is one tie rod 8a
And one end of the first rack tooth portion 6a are connected with each other, and 7b is another ball joint that connects between the other tie rod 8b and the end portion of the second rack toothed portion 6b. Reference numeral 9 is a control unit, 10 is a vehicle speed sensor for detecting a vehicle speed, 11 is a vehicle battery, 12 is a key switch, 13 is a DC motor having a shunt winding or a magnetic field, and is driven from the battery 11 via the control unit 9. It Reference numeral 14 is a worm shaft that is connected to the output shaft of the motor 13 and forms a speed reducer, 15 is a worm wheel shaft that meshes with and drives the worm shaft 14, and 16
This worm wheel shaft 15 and the second rack tooth portion 6b
An electromagnetic clutch that engages or disengages a mechanical connection between the second pinion shaft 17 that meshes with the second pinion shaft 17 according to an instruction from the control unit 9, and a lock position detection sensor 18 that detects a front wheel left-right lock position during steering of the steering wheel.

FIG. 2 shows a block circuit diagram of the control unit 9. 9a is a steering torque measuring means for measuring the steering torque by the input from the torque sensor 3, and 9b is a vehicle speed sensor 10.
The vehicle speed measuring means for detecting the vehicle speed by the input from 9c is the lock position detecting means for detecting the lock positions of the left and right front wheels when steering the steering wheel, and 9d is the output from the lock position detecting means 9c for steering torque other than the lock position. When the indicated motor current value is equal to or more than the predetermined current value, the motor current abnormality determining means 9j outputs the motor current abnormality, and 9e is normally a value according to the steering torque.
Is zero at the time of the abnormality determination output, and when the output of the lock position detection sensor 18 is the lock position detection, it is set to become zero or a predetermined value after the first predetermined time elapses. Motor current determining means for determining the motor current to a value that has been reduced, 9f is the motor current determining means 9
Motor current control means for controlling the motor current on the basis of the output of e, 9g is electromagnetic clutch control means for controlling the engagement or disengagement of the electromagnetic clutch 16 under a condition determined at least by the vehicle speed.

Next, the operation will be described with reference to FIGS. FIG. 3 is a control characteristic diagram of steering torque vs. motor current, FIG. 4 is a control characteristic diagram of vehicle speed vs. motor current and electromagnetic clutch applied voltage, and FIG. 7 is a flow chart showing a control program of the control unit 9.

First, when the key switch 12 is turned on when the engine is started, the electromagnetic clutch 16 is turned on, and the worm wheel shaft 15 and the second pinion shaft 17 are mechanically connected.
When a torque is applied to the handle 1 in this state, the control unit 9 controls the current of the motor 13 as shown in FIG. When the steering torque is increased to the right in FIG. 3, the motor 13 is turned on at the point a, and a motor current of I _OF (about 2 to 10 A) is passed in order to reduce the influence of the inertia of the motor and the mechanical system. The steering torque is further increased, and the motor current is linearly increased with respect to the steering torque from the six points.
It becomes 100% current at point c. On the contrary, the torque is reduced and the motor current decreases from the steering torque point c to the motor current value I _{OF at} the point b. When the torque further decreases to point a, the motor turns off. The same control is performed 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 is turned on at the point a and the motor current of I _OF flows. If the torque is further increased, the motor current is gradually increased from the point b.
The output torque to the steering wheel 1 gradually increases, and the auxiliary torque corresponding to the driver's force applied to the steering wheel 1 is applied to the worm wheel shaft 15, the electromagnetic clutch 16, and the second pinion shaft 1.
The second is transmitted to the rack tooth portion 6b via 7. For this reason,
The handle 1 becomes lighter. The above is the operation of this device when the vehicle is stopped.

Next, when the vehicle is in a running state, the motor current is controlled at the vehicle speed d point (vehicle speed = V ₂ ) as shown in FIG.
The current is reduced to _OF , and is made zero with the applied voltage of the electromagnetic clutch 16 at the vehicle speed at point e (vehicle speed = V ₁ ). For this reason, the worm wheel shaft 15 and the second pinion shaft 17 are disengaged from each other, and the steering wheel is not assisted by the driver turning the steering wheel. By the way, in the case where the steering of the steering wheel 1 is performed to the vicinity of the lock position like the steering when the vehicle is stopped, the steering wheel is heavy due to the vicinity of the steering wheel lock when the motor 13 or the mechanical system is locked. Since it cannot be distinguished from the case, the motor 13 is continuously energized to control the motor and the control unit 9 for controlling the motor.
There is a possibility that the power element forming a part of the above may be destroyed by the temperature rise due to heat generation. In addition, the steering wheel cannot be steered due to the mechanical lock, which could lead to an accident. Therefore, in the present invention, as shown in the flowchart of FIG. 7, the output from the lock position detection sensor 18 that detects the left and right lock positions of the front wheels during steering of the steering wheel is an output other than the lock position and the command value of the motor current corresponding to the steering torque is When the current value is equal to or more than a predetermined current value I _MO (for example, 15 to 25 A), it is determined to be abnormal, the motor current is set to zero, the electromagnetic clutch 16 is disengaged, and the motor 13 and the power element are prevented from being damaged by overheating, and the machine The steering wheel can be steered at the time of mechanical lock. Next, as shown in the characteristic diagram of decrease control of the motor current with respect to time when the state in which the current supplied to the motor 13 is equal to or more than a predetermined value continues for a predetermined time or more as shown in FIG. In the output, when the motor current exceeds a predetermined current value I _MO for a predetermined time T _MS (for example, 10 seconds to 1 minute), the motor 13 and a part of the control unit 9 are configured to energize the motor. In order to prevent the power element for controlling the temperature from being destroyed due to the temperature rise, it is controlled by the flowchart shown in FIG. That is, the motor current is controlled by a value obtained by multiplying the motor current I _M1 corresponding to the steering torque by the damping constant K _t that gradually decreases with the passage of time. As a result, the motor current gradually decreases and becomes zero in a predetermined time (for example, 30 seconds to 5 minutes), and the applied voltage of the electromagnetic clutch 16 is also controlled to zero at the same time, and the worm wheel shaft 1
The fifth pinion shaft 17 and the second pinion shaft 17 are disengaged from each other, so that the steering has no auxiliary bias.

In this way, by using the lock position detection sensor that does not cause variations between vehicles and judging the abnormality when the lock position is not reached, it is possible to reliably judge the abnormality without being affected by the steering wheel lock state and to achieve high accuracy. It is possible to avoid abnormalities.

Further, when the lock position is detected, the motor current is gradually reduced to zero or a predetermined value after a lapse of a predetermined time, whereby hunting control can be prevented and steering wheel shock can be reduced.

The lock position detection sensor 18 can be generally installed, and even if the lock position detection sensor 18 is used, there is no particular increase in cost.

Note that FIG. 6 is a characteristic diagram of motor current decrease control according to another embodiment. Even when the motor current is controlled to decrease as shown in FIG. Similar effects are obtained.

〔The invention's effect〕

As described above, according to the present invention, the lock position detection sensor distinguishes between the lock of the motor and the mechanical system and the steering near the handle lock position, and the motor current is set to zero when the motor and the mechanical system are locked. It is possible to prevent the motor and the power element from being destroyed due to a temperature rise, and to steer the steering wheel even when mechanically locked to ensure reliability and safe driving.

[Brief description of drawings]

FIG. 1 is a block diagram of a motor-driven power steering control device according to an embodiment of the present invention, FIG. 2 is a block circuit diagram of a control unit, FIG. 3 is a control characteristic diagram of steering torque vs. motor current, and FIG. FIG. 6 is a control characteristic diagram of vehicle current vs. motor current and electromagnetic clutch applied voltage, and FIG. 5 is a control characteristic diagram of the motor current with respect to time when a state in which the energizing current to the motor is a predetermined value or more is connected for a predetermined time or more, FIG.
FIG. 7 is a characteristic diagram of motor current reduction control according to another embodiment, and FIG. 7 is a flow chart of a control program. 1 ... Handle, 3 is a torque sensor, 5 ... First pinion shaft, 6 ... Rack shaft, 9 ... Control unit, 9a ... Steering torque measuring means, 9b ... Vehicle speed measuring means, 9c ... Lock Position detecting means, 9d ... Motor current abnormality determining means, 9e ... Motor current determining means, 9f.
Motor current control means, 9g ... Electromagnetic clutch control means,
10 ... Vehicle speed sensor, 11 ... Battery, 13 ... Motor, 14 ... Worm shaft, 16 ... Electromagnetic clutch, 17
...... Second pinion shaft, 18 ...... Lock position detection sensor. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (2)

[Claims] 1. A vehicle speed sensor for detecting a vehicle speed, a torque sensor provided in the middle of a steering shaft for detecting a turning force of a steering wheel, and a lock position detection sensor for detecting a left and right lock position of a front wheel when steering the steering wheel. A vehicle speed sensor, a torque sensor, and a control unit that receives each signal of the lock position detection sensor as an input; and a direct current motor that is driven from an in-vehicle battery via the control unit, the control unit comprising: Vehicle speed measuring means for measuring a vehicle speed by an input signal from the sensor, steering torque measuring means for measuring a steering torque by an input signal from the torque sensor, and a front wheel at the time of steering the steering wheel by an input signal from the lock position detection sensor. Lock position detecting means for detecting the left and right lock positions, When the output from the lock position detecting means is other than the lock position and the motor current instruction value corresponding to the steering torque is equal to or more than the predetermined current value, the motor current abnormality determining means for determining and outputting the motor current abnormality, A motor current determining unit that determines the motor current to a value according to the steering torque, and determines the motor current to zero when the output of the motor current abnormality determining unit is an abnormality determination output, and an output of the motor current determining unit. And a motor current control means for controlling the motor current based on the motor current. 2. The motor current determining means, when the output signal from the lock position detection sensor is the lock position detection,
The motor-driven power steering control device according to claim 1, wherein the motor current is gradually reduced to zero or a predetermined value after a predetermined time has elapsed.