JPH0331068A - Diagnostic method for power steering system - Google Patents

Abstract

PURPOSE:To attain the diagnosis of a change in steering force in relation to a change in a car speed by setting a pressure in a reaction force chamber in accordance with an engine speed at the time of a self diagnostic mode for diagnosing whether the change of steering force for changing of the car speed in a power steering system having the reaction force chamber is good or not. CONSTITUTION:Pressure oil, through rotation of an oil pump 3 by an engine 1, is supplied to a power cylinder through a control valve 12 in a power steering. Through a solenoid valve 11 controlled by a control unit 7 in accordance with an engine speed signal (a) and a car speed signal (b), the pressure oil is supplied to a reaction force chamber in the control valve 12. In the case of a power steering system thus constituted, at the time of a self diagnostic mode, a drive current of the solenoid valve 11 is controlled in accordance with a value of the engine speed signal (a) in the control unit 7. In this way, a pressure in the reaction force chamber can be controlled based on the engine speed signal (a), and the characteristic of a change of steering force in relation to a change in a car speed can be diagnosed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for diagnosing the quality of changes in steering force with respect to changes in vehicle speed.

[Conventional technology]

First, a typical power steering system will be explained using FIG. 2. In Fig. 2, 1 is the engine, 2 is the vehicle speed sensor, 3 is the oil pump, 4 is the tank, 5 is the discharge side piping, 6 is the return side piping, 7 is the control device, 8 is the current supply line, 9
10 is the ignition key, 11 is the solenoid valve, 12 is the power steering control valve, and 13 is the steering shaft.

Next, the operation will be explained. First, normal operation will be explained. When the ignition key 9 is turned on and the engine 1 starts, the oil pump 3 is rotated by the engine 1 and supplies oil to the power steering control valve 12 and the like as pressure oil. The supplied oil passes through the power steering control valve 12 and the like, and then returns to the tank 4 via the return pipe 6. The engine 1 outputs an engine speed signal a to the control device 7, and the vehicle speed sensor 2 outputs a vehicle speed signal a to the control device 7. The control device 7 manually inputs an engine speed signal a and a vehicle speed signal S, supplies a current corresponding to the engine signal A and a vehicle speed signal S to the solenoid 14 via a current supply line 8, and controls the reaction pressure. Generates steering force according to vehicle speed.

Figure 3 is an explanatory diagram showing details of solenoid valve ll.
14 is a solenoid, 15 is a spool, 16 is a reaction force chamber in the power steering control valve 12,
In this figure, the same or equivalent parts as in FIG. 2 are given the same reference numerals. FIG. 3(a) shows the state of the solenoid valve when the vehicle is running at high speed, the valve being in the "open" state and a predetermined pressure being supplied to the reaction force chamber. This predetermined pressure is converted into torque to generate a predetermined steering force.

Figure 3 (bl is the state of the solenoid valve when the vehicle is stationary. The valve is in the "closed" state, and the pressure in the reaction force chamber is the tank pressure. Therefore, the reaction force becomes zero.

At the time of shipping inspection, etc., it is necessary to confirm the operation of the power steering system described above. FIG. 4 is a flowchart showing a conventional diagnostic flow for this purpose. First, ignition key 9 and diagnostic switch SW (Figure 2)
is turned on (step 21). As a result, the vehicle remains in the self-diagnosis mode until the ignition key 9 is turned off. This diagnostic switch SW is located in a position where the user cannot operate it, and is normally turned off. When the diagnostic switch SW is off, the operation of the flowchart shown in FIG. 4 is not performed, and normal processing is performed.

Next, start the engine with the starter inch (step 22), and set the current (approximately 0.95A) at vehicle speed Ok m/h.
to drive the solenoid 14 (step 23). From then on,
Solenoid 14 continues to be driven by this current.

Next, check whether the vehicle speed signal is normal or not.
If the vehicle speed signal is normal, a flag indicating that the vehicle speed signal is normal is set in the internal memory (step 25). Normally, immediately after entering the self-diagnosis mode, the vehicle is not running, so the vehicle speed signal will not be normal, but this flow is repeatedly executed as shown in step 35, so the process moves to step 24 after the vehicle is running. In this case, the counter that counts the vehicle speed signal holds the number of pulses equal to or greater than a predetermined number of pulses (for example, 7 pulses), so the vehicle speed signal becomes normal.

Next, it is determined whether the engine speed signal is normal (for example, whether the number of pulses is 21 or more) (Step 26)
, if the engine speed signal is normal, a flag indicating that the engine rotational speed signal is normal is set (step 27). Next, it is determined whether the solenoid is normal or not (step 28), and if it is normal, a flag indicating that the solenoid is normal is set (step 29), and if it is not normal, the current supply to the solenoid 14 is stopped (step 30). . Whether or not the solenoid 14 is normal is determined based on whether the drive current value set in step 23 is a specified value.

Next, it is determined whether the backup power source is normal or not (step 31), and if it is normal, a flag indicating that the backup power source is normal is set (step 32). Next, it is determined whether the steering force characteristic changeover switch is normal or not (switch 33), and if it is normal, a flag indicating that the changeover switch is normal is set (switch 34). The determination as to whether the changeover switch is normal or not is made by, for example, determining that the changeover switch is normal if either sport or normal has been selected at least once.

Next, it is determined whether the diagnostic switch SW is on or not (step 35), and as long as the switch SW is on, step 24)
Repeat steps from 35.

Next, after the diagnostic switch SW is turned off, the solenoid is stopped and the diagnostic results are output (steps 36 and 37). The diagnosis result is determined to be normal or abnormal depending on whether a flag is set in the corresponding internal memory, and the indicator light is blinked depending on whether it is normal or abnormal or depending on the diagnosis target.

[Problem to be solved by the invention]

However, when diagnosing the power steering system in conventional self-diagnosis mode, the vehicle
Since the vehicle only travels, it is not possible to see changes in steering force in response to changes in vehicle speed, and even if there is a problem with changes in steering force, it cannot be discovered. In this case, changes in steering force in response to changes in vehicle speed cannot be known unless the vehicle is actually driven at a considerable speed during normal processing, or the vehicle speed signal fails intentionally to put the engine in a nuisance mode, which is virtually impossible. .

The present invention has been made in view of the above points, and an object thereof is to provide a power steering system diagnostic method capable of diagnosing changes in steering force in response to changes in vehicle speed in self-diagnosis mode. .

[Means to solve the problem]

In order to achieve such an object, the present invention diagnoses whether the steering force change is good or bad by setting the pressure in the reaction force chamber according to the engine speed in the self-diagnosis mode.

[Effect]

In the power steering system diagnosis method according to the present invention, the solenoid valve drive current is controlled by the engine signal in the self-diagnosis mode.

〔Example〕

An embodiment of the power steering system diagnostic method according to the present invention will be described with reference to FIG. The difference between the flow shown in FIG. 1 showing this embodiment and the flow shown in FIG. 4 showing the conventional method is step 40, so the explanation of steps other than step 40 will be omitted.

In the self-diagnosis mode, the vehicle travels when checking the vehicle speed signal, but this travels only a few meters, and in this traveling state, changes in steering force relative to changes in vehicle speed cannot be diagnosed. In this embodiment, even if the vehicle is stopped, changes in steering force relative to changes in vehicle speed can be diagnosed. Next, step 40 will be explained.

In step 40, the engine speed signal a (Fig. 2,
(see FIG. 3) to control the drive current of the solenoid valve 11. The engine rotational speed signal a is input to the control device 7, and the control device 7 controls the drive current of the solenoid valve 11 according to the value of the signal a. Therefore, the pressure in the reaction force chamber 12 is controlled by the engine speed signal a,
By making the value of the engine rotational speed signal a correspond to the vehicle speed, it is possible to diagnose the characteristics of changes in steering force with respect to changes in vehicle speed. As a result, changes in steering force can be easily observed without running the vehicle or requiring the complicated effort of switching to an engine-sensitive mode when a vehicle speed signal fails.

FIG. 5 is a graph showing the vehicle speed conversion value when the engine is activated, where SL is during normal processing and S2 is during self-diagnosis mode. Since the engine speed cannot be increased too high in self-diagnosis mode, by creating a characteristic in which the vehicle speed rises rapidly relative to the engine speed,
This makes it possible to diagnose steering force characteristics at high speeds even at low engine speeds.

In this way, by being able to diagnose whether the change in steering force is good or bad in response to a change in vehicle speed in the self-diagnosis mode, it is possible to observe changes in the weight of the steering force when the vehicle is stopped during a shipping inspection or the like. It is possible to detect a state in which oil pressure is not normally supplied to 16.

〔Effect of the invention〕

As explained above, in the self-diagnosis mode, the present invention diagnoses whether the change in steering force is good or bad in response to a change in vehicle speed by setting the pressure in the reaction force chamber according to the engine speed and diagnosing whether the change in steering force is good or bad. In this case, there is an advantage that there is no need to actually run the vehicle, and there is no need to go through the complicated and troublesome effort of setting the engine-sensitive mode when the vehicle speed signal fails.

[Brief explanation of drawings]

Figure 1 is a flowchart for explaining an embodiment of the power steering system diagnostic method according to the present invention, Figure 2 is a system diagram showing a general power steering system, and Figure 3 is a detailed diagram of the system related to the solenoid valve. 4 is a flowchart for explaining the conventional power steering system diagnosis method, and FIG. 5 is a graph showing the vehicle speed conversion value when the engine is detected during normal processing and diagnosis (self-diagnosis mode). It is.

Claims (1)

[Scope of Claims] A method for diagnosing, using a self-diagnosis mode, whether a change in steering force in response to a change in vehicle speed in a power steering system having a reaction force chamber for changing the steering force in accordance with a change in vehicle speed is performed using a self-diagnosis mode. A method for diagnosing a power steering system, comprising: diagnosing whether the steering force change is good or bad by setting a pressure in a reaction force chamber according to the engine rotational speed in the mode.