JP2896600B2 - Electric power steering device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering device for a vehicle, and more particularly to an electric power steering device that performs a fail-safe operation related to a vehicle speed.

[Conventional technology]

2. Description of the Related Art Conventionally, fail-safe regarding a vehicle speed in an electric power steering device for a vehicle is determined to be a failure regarding the vehicle speed when the following conditions are satisfied, and power assist in the electric power steering device is stopped.

. When the engine speed is 4000 rpm or more and no vehicle speed signal is input from the vehicle speed sensor for 20 seconds.

. When the vehicle speed changes more than 20km / h during 140msec.

FIG. 4 is a diagram for explaining a conventional condition for determining a failure of a vehicle speed signal. The condition can be determined when the engine speed Ne is equal to or greater than a predetermined value Neα.

[Problems to be solved by the invention]

However, with regard to the above conditions, even when the vehicle is stopped, there is a possibility that the number of revolutions may increase due to the racing of the engine (idling), and that the conditions may be satisfied.

Conventionally, in order to avoid such a situation, there is a case where an idle switch for limiting an idle rotation speed is provided when the vehicle is stopped, but there is a problem that this inevitably increases the cost.

Also, the above condition may be satisfied even when the vehicle locks the tire due to sudden braking.

On the other hand, conventionally, a stop lamp switch signal indicating the operation of the brake is input to the controller to prevent erroneous determination at the time of the brake operation, but this also causes a problem of increased cost. There is.

[Object of the invention]

SUMMARY OF THE INVENTION The present invention is directed to solving such a problem of the prior art. In an electric power steering apparatus for a vehicle, an erroneous determination of a fail condition in each of the above-described cases based on a vehicle speed sensor is prevented. An object of the present invention is to enable a fail-safe operation to be correctly performed in a steering device.

[Means for solving the problem]

According to the present invention, there is provided an electric motor which controls an operation assisting force for a steering device of a vehicle in accordance with a vehicle speed, and stops the assist when a vehicle speed detection value detected by a vehicle speed sensor is 0 for a predetermined time or more at a predetermined engine speed or more. In the power steering device, a rotation speed change rate measurement unit that measures a change rate ΔNe of the engine rotation speed for a predetermined time immediately before the engine rotation speed reaches the predetermined rotation speed, wherein the rotation speed change rate ΔNe is equal to or less than a predetermined value. Vehicle speed signal detecting means for detecting the presence or absence of a vehicle speed signal within a predetermined determination time; and the vehicle speed sensor when the rate of change ΔNe of the rotation speed is equal to or less than a predetermined value and there is no continuous vehicle speed signal within the predetermined determination time. Fail determination means for determining a signal failure, and stopping the operation assist of the steering device at the time of the failure determination. We are taking the deposition. This aims to achieve the above-mentioned object.

[Action]

In the electric power steering device, the assist is stopped when the vehicle speed detected value by the vehicle speed sensor is equal to or more than 0 for a predetermined time at a predetermined engine speed or more, and the engine speed is calculated for a predetermined time immediately before the engine speed reaches the predetermined speed. The change rate is measured, and when this is equal to or less than a predetermined value, the presence or absence of a vehicle speed signal within a predetermined determination time is detected,
When there is no vehicle speed signal continuously within the predetermined determination time, a failure of the vehicle speed sensor signal is determined. Then, when the failure is determined, the steering assist operation is stopped, so that the erroneous determination of the fail condition in each case based on the vehicle speed sensor is prevented, and the electric power steering device correctly performs the fail-safe operation. Will be able to do it.

〔Example〕

FIG. 1 shows a system configuration according to an embodiment of the present invention. Reference numeral 11 denotes a controller for controlling driving and running of a vehicle.

The controller 11 has a steering motor (M) 12 connected to its ports a1 and a2, and a clutch for transmitting the operation force to a steering device (not shown).
Thirteen operation signals CLA and CLB are connected to ports a3 and a4. The steering motor 12 turns the steering device to the left or right in accordance with the polarities of the outputs M + and M- at the ports a1 and a2. The vehicle speed sensor 14 is connected to port a5.
And a ground sensor, and a rotation sensor 15 for detecting the engine speed is connected between the ports a6 and b2.

Further, a diagnosis output indicating the self-diagnosis result of the engine or the like is connected to the port a7, and the torque sensor 16 is connected to the ports a8, a9, a10, and a11.

When the battery 18 is connected to the port b1 and the ignition switch 17 is turned on, the port
It is connected to b2. The ground side of the battery 18 is connected to the port b3. The output of an alternator (not shown) connected to the engine is connected to port b4, and an ignition pulse from the ignition device 19 is supplied to port b5.
It is connected to the.

The present invention provides an electric motor that controls an assisting force of a steering device of a vehicle according to a vehicle speed, and stops the assist when a vehicle speed detected value by a vehicle speed sensor 14 is 0 for a predetermined time or more at a predetermined engine speed or more. In the power steering device, the rotation speed change rate measuring means 1 measures the change rate ΔNe of the engine rotation speed for a predetermined time immediately before the engine rotation speed reaches the predetermined rotation speed, and the vehicle speed signal detection means 2 detects the change in the rotation speed. Rate ΔNe
Is less than or equal to a predetermined value, the presence or absence of a vehicle speed signal within a predetermined determination time is detected, and the failure determination means 3 determines failure of the vehicle speed sensor signal when there is no continuous vehicle speed signal within the determination time. , The operation assist of the steering device is stopped.

FIG. 2 is a flowchart showing the operation of the present invention, and explains the control in the controller 11.

In the electric power steering device of the present invention, the engine speed Ne is measured, and the engine speed Ne is determined to be the predetermined engine speed Neα.
In this state, it is determined whether there is a vehicle speed signal from the vehicle speed sensor 14. When the vehicle speed signal is 0 for a predetermined time or longer, for example, the clutch 13 is turned off and power assist in the electric power steering device is stopped. This method is similar to that of the conventional device.

That is, first, the engine speed is equal to the predetermined speed Ne.
When it has reached α, the rate of change ΔNe of the engine speed in several seconds before that is measured.

Next, when the rate of change ΔNe of the engine speed at this time is smaller than a predetermined value ΔNeβ, it is determined that fail-safe determination is possible.

Further, when the determination can be made as described above, several seconds (Tse
c) Check for the presence of a vehicle speed signal.

Then, when there is no continuous vehicle speed sensor input within the determination time (Tsec), it is determined that the vehicle speed signal has failed.

FIG. 3 is a diagram for explaining a failure determination condition of a vehicle speed signal according to the present invention.

In the present invention, when the vehicle speed signal Ne is equal to or greater than the predetermined value Neα, the failure determination is performed as follows.

That is, the rate of change ΔNeβ of the vehicle speed, which is a reference for determination, is obtained from the following equation.

ΔNeβ = (Neα−Neβ) / T where Neβ is the engine speed before Tsec which reaches the rotation speed Neα.

ΔNeβ is a vehicle speed change rate value for determining that the engine is rapidly increased by racing, and can be determined by measuring in advance the actual vehicle.

That is, in the case of racing, the engine speed rapidly increases, and the vehicle speed change rate ΔNe becomes larger than the vehicle speed change rate ΔNeβ according to the equation. Therefore, when this condition is satisfied, it is determined that the racing has occurred, and the vehicle speed signal fails. Make no judgment.

That is, in the acceleration state during normal traveling, the vehicle speed change rate ΔNe becomes smaller than the vehicle speed change rate ΔNeβ according to the formula, so that when this condition is satisfied, it is possible to perform a failure determination of the vehicle speed signal.

As described above, according to the present invention, it is possible to prevent erroneous determination of a vehicle speed signal failure when the vehicle speed change rate ΔNe is increased due to racing or the like. In a normal traveling acceleration state of the vehicle, the vehicle speed change rate ΔNe is small, so that the failure determination of the vehicle speed signal can be appropriately performed.

〔The invention's effect〕

As described above, according to the present invention, in the electric power steering device for a vehicle, the control to stop the power assist when the vehicle speed detection value of the vehicle speed sensor is 0 at a predetermined engine speed or more is performed, and the vehicle speed change rate is reduced. Since the failure state of the vehicle speed signal is determined according to the magnitude, it is possible to prevent an erroneous failure determination of the output signal of the vehicle speed sensor when the vehicle speed suddenly increases due to racing or the like.

According to the present invention, the failure determination time of the vehicle speed sensor can be set short, so that the failure determination of the vehicle speed signal can be executed at an early stage, and the running stability can be improved.

Further, according to the present invention, the signals of the idle switch and the stop lamp switch are unnecessary, and there is no risk of cost increase based on these. Further, in the system of the conventional electric power steering apparatus, the present invention can be implemented only by changing the program, so that the ranking can be changed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a system configuration of an embodiment of the present invention, FIG. 2 is a flowchart showing an operation of the present invention, FIG. 3 is a diagram for explaining a failure judgment condition of a vehicle speed signal in the present invention, FIG. FIG. 4 is a diagram for explaining a conventional failure determination condition of a vehicle speed signal. 1 ... rotational speed change rate measuring means, 2 ... vehicle speed signal detecting means, 3 ... fail determining means, 14 ... vehicle speed sensor.

Claims (2)

(57) [Claims] An operation assisting force for a steering device of a vehicle is controlled in accordance with a vehicle speed, and the assist is stopped when a vehicle speed detected by a vehicle speed sensor is at a zero level for a predetermined time or more at a predetermined engine speed or higher. In the electric power steering device, the rotation speed change rate measuring means for measuring the change rate ΔNe of the engine rotation speed for a predetermined time immediately before the engine rotation speed reaches the predetermined rotation speed, and the rotation speed change rate ΔNe is a predetermined value. A vehicle speed signal detecting means for detecting the presence or absence of a vehicle speed signal within a predetermined determination time when the change rate ΔNe of the rotation speed is equal to or less than a predetermined value and the vehicle speed signal is not continuously provided within the predetermined determination time; A failure determination unit that determines a failure of the vehicle speed sensor signal; and when the failure is determined, the operation assist of the steering device is stopped. An electric power steering device characterized by the above-mentioned. 2. The electric power steering apparatus according to claim 1, wherein when the engine speed is equal to or higher than the predetermined speed and the rate of change ΔNe is equal to or higher than the predetermined value, it is determined that the vehicle is racing.