JPS6320271A - Motor-driven type power steering controller - Google Patents

Abstract

PURPOSE:To prevent the destruction of a motor and a power element by reducing the motor electric current to zero when the destruction due to the heat generation is generated on the motor or the power element. CONSTITUTION:When a key switch is turned ON on the engine start, an electromagnetic clutch 16 is turned ON, and a worm wheel shaft 15 and the second pinion shaft 17 are connected mechanically. When a steering wheel 1 is applied with a turning moment in this state, a control unit 9 controls the electric current of a motor 13. The control unit 9 is equipped with a motor electric current anomaly judging means 9d which judges the anomaly of electric current when the indication value of the motor electric current corresponding to the steering torque is over a prescribed electric current value. When the output of the motor electric current anomaly judging means 9d accords with the output in the judgement 'anormaly', the motor electric current is reduced to zero on the basis of the output of the motor electric current determining means 9c.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Applicability] The present invention relates to a motor-driven power steering control device that assists and biases a steering device of an automobile using motor rotational force.

[Conventional technology]

Conventionally, this type of power steering device auxiliarily biases the driving force of a motor to a resteering shaft or a rack shaft by a transmission mechanism such as a gear or a belt via a reduction gear.

[Problem that the invention seeks to solve]

Conventional power steering devices such as those described above cannot distinguish the steering wheel from being locked when the motor or mechanical system is malfunctioning, so current is continuously applied to the motor, causing the motor and the power element that controls the motor to generate heat. There was a risk that the vehicle would be destroyed by rising temperatures, or the steering wheel would become impossible to steer due to a mechanical lock, leading to an accident.

This invention was made to solve the above-mentioned problems, and it is a motor drive that prevents the motor and power element from being destroyed due to temperature rise, and also enables steering even when mechanically locked, allowing safe driving. The purpose of this invention is to obtain a power steering control device based on the following formula.

[Means for solving problems]

The motor-driven power steering control device according to the present invention includes a vehicle speed sensor that detects vehicle speed, a torque sensor that detects the rotational force of the steering wheel, a lock position detection sensor that detects the left and right lock positions of the front wheels when steering the steering wheel, and the above-described components. A control unit that receives signals from each sensor as input,
It is equipped with a motor driven via this control unit and an electromagnetic clutch that is engaged and disengaged by the control unit.

[For production]

In this invention, if the motor or power element is destroyed due to heat generation, or if the steering wheel becomes heavy due to mechanical locking, the lock position detection sensor detects the locking of the motor, locking of the mechanical system, and steering near the steering wheel locking position. The system identifies this and sets the motor current to zero, as well as interrupting the electromagnetic clutch. This prevents damage to the motor and power device, and allows the steering wheel to be operated even when mechanically locked.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows a configuration diagram including a block circuit diagram of a motor-driven power steering control device according to the present invention.
In the figure, 1 is a steering wheel that receives the driver's steering rotational force, 3 is a torque sensor that outputs a signal according to the rotational force applied to the steering wheel 1, 4a is a first universal joint, and 4b is a second universal joint. A universal joint, 2a is a first steering shaft that connects the handle 1 and the torque sensor 3, 2b is a second steering shaft that connects the torque sensor 3 and the first universal joint 4a, and 2c is a first steering shaft. A third joint connecting universal joint 4a and second universal joint l-4b
a steering shaft 5, a first pinion shaft connected to the second universal joint, 6 a rack shaft having a first rack tooth 6a and a second rack tooth 6b that mesh with the pinion shaft 5; 7a is one tie rod 8
7b is a ball joint that connects the other tie rod 8b and the end of the second rack tooth 6b. . 9 is a control unit, 10 is a vehicle speed sensor that detects the vehicle speed, 11 is an on-board battery, 12 is a key switch, and 13 is a DC motor having a shunt winding or a magnetic field, which is driven from the battery 11 via the control unit 9. Ru. 14 is a worm shaft 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; 16;
An electromagnetic clutch 18 connects or disconnects the mechanical connection between the wheel shaft 15 and the second pinion shaft 17 that engages with the toothed portion 6b according to instructions from the control unit 9; This is a lock position detection sensor that detects the left and right M wheel lock positions during steering.

FIG. 2 shows a block circuit diagram of the control unit 9, in which 9a is a steering torque measuring means for measuring steering torque based on input from the torque sensor 3, and 9b is a vehicle speed sensor 10.
9c is a lock position detecting means for detecting the lock position of the left and right front wheels when the steering wheel is being steered; 9d is a lock position detecting means for detecting the lock position of the left and right front wheels when the steering wheel is turned; and 9d is a lock position detecting means in which the output from the lock position detecting means 9c corresponds to the steering torque at positions other than the lock position. Motor current abnormality determining means 9e outputs a determination that the motor current is abnormal when the specified motor current instruction value is equal to or higher than a predetermined current value. Normally, the output of the motor current abnormality determining means 9d is an abnormality determination output at a value corresponding to the steering torque. 9f is a motor current control means for controlling the motor current based on the output of the determining means 9e;
g is an electromagnetic clutch control means that controls the engagement or disengagement of the electromagnetic clutch 16 under conditions determined by at least the vehicle speed.

Next, the operation will be explained with reference to FIGS. 3 to 5. 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 flowchart showing a control program of the control unit 9.

First, when starting the engine, the key switch 12, the wheel shaft 15, and the second pinion shaft 17 are mechanically connected. When a rotational force 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 point a, and in order to reduce the influence of inertia of the motor and mechanical system, IoF (2 to 10
A motor current of about A) is applied. The steering torque is further increased, and the motor current is increased linearly with respect to the steering torque from point b, and the current becomes 100% at point 0.

Conversely, when the torque is decreased, the motor current decreases from the point where the steering torque is 0, and reaches l at point b. This is the motor current value of F. When the torque further decreases to point a, the motor is turned off. Similar control is also performed in the left direction. The relationship between transmitted torque and motor current is proportional. Therefore, when the torque increases in FIG. 3, the motor turns on at point a, and a motor current of IoF flows. When the torque is further increased, the motor current is controlled to gradually increase from point b, so the output torque to the worm shaft 14 gradually increases, and the auxiliary torque corresponding to the driver's force applied to the handle 1 is controlled. The signal is transmitted to the second rack tooth portion 6b via the worm wheel shaft 15, the electromagnetic clutch 16, and the second pinion shaft 17. Therefore, the handle 1 becomes lighter. The above is the operation of this device when the car is stopped.

Next, when the car is in a running state, the motor current is controlled by I at point d vehicle speed (vehicle speed = v2) as shown in Figure 4.
. The current is reduced to F, and is brought to zero together with the voltage applied to the electromagnetic clutch 16 at the 8-point vehicle speed (vehicle speed = v0). As a result, the worm wheel shaft 15 and the second pinion shaft 17 are separated, so that the driver who turns the steering wheel receives no auxiliary bias. By the way, when steering the steering wheel 1 close to the lock position, such as when steering when the car is stopped, the steering wheel becomes heavy due to the locking position when the motor 13 or mechanical system lock is malfunctioning. Therefore, there was a risk that the motor 13 would be continuously energized and the power element forming part of the control unit 9 that controls the motor and the motor 13 would be destroyed by the temperature rise due to heat generation. Additionally, the mechanical lock made it impossible to steer the nozzle, which could lead to an accident. Therefore, in this invention, as shown in the flowchart of FIG. 5, when the output of the lock position detection sensor 18 that detects the left and right lock positions of the front wheels when the steering wheel is turned is at a position other than the lock position, the command value of the motor current corresponding to the steering torque is set to a predetermined value. If the current value exceeds lo, it is determined to be abnormal and the motor current is set to zero, and the electromagnetic clutch 16 is shut off to prevent damage from overheating of the motor] 3 and the power element due to heat generation, and to prevent mechanical locking. It is possible to perform steering wheel steering.

〔Effect of the invention〕

As explained above, according to the present invention, the lock position detection sensor distinguishes between motor lock, mechanical lock, and steering near the handle lock position, and reduces the motor current to zero and disconnects the electromagnetic clutch. This makes it possible to prevent damage to the motor and power element, and also allows the steering wheel to be steered even when mechanically locked, resulting in highly safe power steering.

[Brief explanation of the drawing]

Fig. 1 is a configuration 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 the control unit, Fig. 3 is a control characteristic diagram of steering torque versus motor current, and Fig. 4 5 is a control characteristic diagram of vehicle speed vs. motor current and electromagnetic clutch applied voltage, and FIG. 5 is a flowchart of the control program. 3 is a torque sensor, 5 is a first pinion shaft, 6 is a rack shaft, 9 is a control unit, 9a is a steering torque measuring means, 9b is a vehicle speed measuring means, and is 9C a lock. Position detection means, 9d...Motor current abnormality determination means, 9e...Motor current determination 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, 18. Lock position detection sensor. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (2)

[Claims] (1) A vehicle speed sensor that detects vehicle speed, a torque sensor that is installed in the middle of the steering shaft and detects the rotational force of the steering wheel, a lock position detection sensor that detects the left and right lock positions of the front wheels when steering the steering wheel, and the vehicle speed sensor mentioned above. A control unit that receives signals from a torque sensor and a lock position detection sensor as input, a DC motor driven from an on-board battery via the control unit, and an electromagnetic motor that is directly connected to the output shaft of this motor and coupled or separated by the control unit. A motor-driven power steering control device characterized by comprising a clutch. (2) The control unit includes a steering torque measuring means that measures the steering torque based on input from the torque sensor;
A vehicle speed measuring means for measuring the vehicle speed, a lock position detecting means for detecting the left and right lock positions of the front wheels when steering the steering wheel based on input from a lock position detecting sensor, and an output from the lock position detecting sensor is an output other than the lock position. a motor current abnormality determining means for determining and outputting a motor current abnormality when a motor current instruction value corresponding to the steering torque is equal to or higher than a predetermined current value; a motor current determining means that determines the motor current to be zero when the output is determined to be abnormal, a motor current controlling means that controls the motor current based on the output of the motor current determining means, and an electromagnetic clutch that operates under conditions determined by at least the vehicle speed. 2. The motor-driven power steering control device according to claim 1, further comprising electromagnetic clutch control means for controlling engagement and disengagement.