JPH069981B2 - 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 rotational force of a motor.

[Conventional technology]

Heretofore, this type of power steering control device has assisted 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 reduction gear.

[Problems to be solved by the invention]

Since the conventional power steering control device is configured as described above, it is a method that shuts off the auxiliary urging of the motor at a certain vehicle speed or more when the vehicle is running, but when the vehicle speed sensor is disconnected, the steering wheel remains light while driving. There was a problem that was accompanied by danger.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a motor-driven power steering control device that can reliably and safely travel at high speed even when the vehicle speed sensor is disconnected. To do.

[Means for solving problems]

The motor-driven power steering control device according to the present invention determines that the vehicle is in the traveling state by the traveling determination means when the variation frequency and the variation amplitude of the vehicle height sensor are equal to or greater than a predetermined value for a predetermined time or longer, and when the vehicle speed is zero. When the output of the travel determination means is the travel determination output, the vehicle speed sensor disconnection determination means determines that the vehicle speed sensor is disconnected, and the motor current is controlled to zero when the vehicle speed sensor is disconnected.

[Work]

The motor-driven power steering control device according to the present invention detects the disconnection of the vehicle speed sensor by adding the vehicle height sensor and changing the control program of the control unit when the vehicle speed sensor is disconnected, and shuts off the motor current to eliminate auxiliary energization. Can be in a state.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, 1 is a steering wheel that receives a steering torque, 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,
4b is a second universal joint, 2a is a first steering shaft connecting the steering wheel 1 and the torque sensor 3, and 2b is a second steering shaft connecting the torque sensor 3 and the first universal joint 4a. 2c is a third steering shaft connecting the first universal joint 4a and the second universal joint 4b, and 5 is a second universal joint 4
A first pinion shaft connected to b, 6 is a rack shaft having a first rack tooth portion 6a and a second rack tooth portion 6b that mesh with the pinion shaft 5, and 7a is one of the tie rod 8a and the rack shaft 6. One ball joint that connects one,
7b is another ball joint for connecting the other tie rod 8b and the other of the rack shafts 6 to each other. 9 is a control unit, 10 is a vehicle speed sensor for detecting the vehicle speed, 18 is a vehicle height sensor for detecting the vehicle height of the vehicle, 11 is an on-vehicle battery, 1
Reference numeral 2 is a key switch, and 13 is a DC motor having a shunt winding or a magnetic field, which is driven from a battery 11 via a control unit 9. Reference numeral 14 is a worm shaft that is connected to the output shaft of the motor 13 and forms a speed reducer. Reference numeral 15 is a worm wheel shaft that is driven by meshing with the worm shaft 14.
Reference numeral 6 denotes an electromagnetic clutch for connecting or disconnecting the connection between the worm wheel shaft 15 and the second pinion shaft 17 meshing with the second rack tooth portion 6b of the rack shaft 6 according to the instruction of the control unit 9.

FIG. 2 is a block diagram showing the details of the control unit 9, wherein 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 measuring means for measuring the vehicle speed by the input of the vehicle speed sensor 10. , 9c
Is a vehicle height measuring means for measuring the vehicle height by the input of the vehicle height sensor 18, and 9d is a case where the fluctuation frequency and the fluctuation amplitude of the output signal from the vehicle height measuring means 9c are above a predetermined value for a predetermined time or longer. Traveling determination means for determining the traveling state,
Reference numeral 9e is the traveling determination means 9 when the output of the vehicle speed measurement means 9b is zero.
When the output of d is the travel determination output, the vehicle speed sensor disconnection determination means for determining the disconnection of the vehicle speed sensor 10, 9f normally determines the current of the motor 13 according to the steering torque, and the output of the vehicle speed sensor disconnection determination means 9e. Is a motor current deciding means for deciding the current of the motor 13 to be zero at the time of disconnection judgment output, 9g is a motor current controlling means for controlling the motor current based on the output of the motor current deciding means 9f, and 9h is a condition and a vehicle speed sensor which are decided at least by the vehicle speed. It is an electromagnetic clutch control means for performing control for connecting or disconnecting the electromagnetic clutch 16 under the output condition of the disconnection judging means 9e.

Next, the operation will be described with reference to FIGS. 3 is a control characteristic diagram of steering torque versus motor current, FIG. 4 is a control characteristic diagram 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. First, when the key switch 12 is turned on when starting the engine, the electromagnetic clutch 1
6 is turned on, and the worm wheel shaft 15 and the second pinion shaft 17 are 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. In FIG. 3, when the steering torque is increased to the right, the motor 13 is turned on at the point a to reduce the influence of the inertia of the motor and the mechanical system.
A motor current of o _F (about 2 to 10 A) is passed. Further, the steering torque is increased and the motor current is linearly increased with respect to the steering torque from the point b, and the current becomes 100% at the point c. On the contrary, the torque is decreased and the motor current decreases from the point c to the steering torque, and the motor current value becomes Io _{F at} the point b. When the steering torque further decreases to point a, the motor 13 is turned off. This is performed in the same manner as above even if the steering torque is applied to the left, and the relationship of the transmission torque to the motor current is proportional. As a result, b
Performing the control to gradually increase the motor current from the point causes the output torque to the worm shaft 14 to gradually increase, and the auxiliary torque corresponding to the force applied to the steering wheel 1 is applied to the worm wheel shaft 15, the electromagnetic clutch 16 and the electromagnetic clutch 16. Second
Is transmitted to the second rack tooth portion 6b via the pinion shaft 17 of. Therefore, the handle 1 becomes lighter. The above is the operation when the vehicle is stopped.

Next, when the vehicle is in a running state, as shown in FIG. 4, the control of the motor current is reduced to the current of Io _F at the vehicle speed at point d, and at the vehicle speed at point e, the applied voltage of the electromagnetic clutch 16 is increased. Set to zero. Therefore, the worm wheel shaft 15 and the second
Since the pinion shaft 17 is disengaged, the steering for the driver turning the steering wheel 1 is not assisted. However, in the conventional device, when the vehicle speed sensor 10 is disconnected, the control corresponding to the vehicle speed is not performed, so that the steering assist force works even at high speed and the steering wheel is too light, which is dangerous. The fluctuation frequency and fluctuation amplitude of the high sensor 18 are equal to or higher than a predetermined value (for example, ± 0.5 Hz or more
When the state of 1 cm or more) lasts for a predetermined time or more (for example, 5 seconds or more), it is determined that the vehicle is in a running state, and when the vehicle speed is zero at this time, it is determined that the vehicle speed sensor 10 is disconnected. When it is determined that the vehicle speed sensor is broken, the current of the motor 13 and the voltage applied to the electromagnetic clutch 16 are controlled to zero so that the steering wheel has no auxiliary biasing force.

In this way, by using the output signal of the vehicle height sensor 18 that faithfully reflects the actual vehicle traveling state and determining the traveling state based on the variation frequency and the variation amplitude of the vehicle height detection signal, highly accurate determination can be performed. It will be possible.

For example, if a shift position signal irrelevant to the engine state is used for running determination, a disconnection of the vehicle speed sensor is erroneously detected when the engine is stopped, and an engine speed signal unrelated to the shift position is used for running determination. However, when the shift position is in neutral, disconnection of the vehicle speed sensor is erroneously detected, and both are in a fail-safe state, which is not practical.

The vehicle height sensor 18 can be generally installed for an electronic suspension device or the like.
The use of does not particularly increase the cost.

〔The invention's effect〕

As described above, according to the present invention, when the vehicle speed sensor is disconnected, the steering wheel remains light even when traveling at high speed.As a countermeasure, the disconnection of the vehicle speed sensor is detected by adding a vehicle height sensor and changing the control program of the control unit, The motor current is cut off, which has the effect of enabling highly reliable and safe power steering, and making the device inexpensive.

[Brief description of drawings]

FIG. 1 is a block diagram of a motor-driven power steering controller according to an embodiment of the present invention, FIG. 2 is a block diagram of a control unit, FIG. 3 is a control characteristic diagram of steering torque vs. motor current, and FIG. FIG. 5 is a flow chart of the control program, which is a control characteristic diagram of the vehicle speed versus the motor current and the voltage applied to the electromagnetic clutch. 1 ... Handle, 2a, 2b, 2c ... Steering shaft, 3 ... Torque sensor, 6 ... Rack shaft, 9 ...
Control unit, 9a ... Steering torque measuring means,
9b ... vehicle speed measuring means, 9c ... vehicle height measuring means, 9d ...
… Running judging means, 9e …… Vehicle speed sensor disconnection judging means, 9
f ... Motor current determining means, 9g ... Motor current controlling means, 9h ... Electromagnetic clutch controlling means, 10 ... Vehicle speed sensor, 11 ... Battery, 13 ... DC motor, 14 ...
Worm shaft, 15 ... Worm wheel shaft, 16 ... Electromagnetic clutch, 17 ... Second pinion shaft, 18 ... Vehicle height sensor. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[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, a vehicle height sensor for detecting a vehicle height, the vehicle speed sensor, the torque sensor, and In a motor-driven power steering control device comprising a control unit that receives each signal of the vehicle height sensor as an input, and a DC motor that is driven from a vehicle-mounted battery via the control unit, an input signal from the torque sensor is used. Steering torque measuring means for measuring a steering torque value, vehicle speed measuring means for measuring a vehicle speed by an input signal from the vehicle speed sensor, vehicle height measuring means for measuring a vehicle height by an input signal from the vehicle height sensor, and The condition that the fluctuation frequency and fluctuation amplitude of the output signal of the vehicle height measuring means are equal to or higher than a predetermined value is maintained for a predetermined time or longer. If the output of the traveling determination means at the time of zero of the vehicle speed measuring means is the traveling determination output, the vehicle speed sensor disconnection determining means for determining that the vehicle speed sensor is disconnected, usually, The motor current is determined according to the steering torque, and when the output of the vehicle speed sensor disconnection determination means is the disconnection determination output, the motor current determination means determines the motor current to zero, and the motor current is determined based on the output of the motor current determination means. A motor drive type power steering control device comprising: a motor current control means for controlling.