JPH01132470A - Safety device for power steering device - Google Patents

Abstract

PURPOSE:To improve safety by forming a bridge circuit by means of a number of strain gauges, detecting the voltage of the ends of each strain gauge and the voltage differences between the strain gauges on the mutually opposite sides, and outputting an abnormality signal when voltage difference is generated. CONSTITUTION:The resistance values of a number of strain gauges 24-27 for detecting steering torque are equalized, and a bridge circuit is formed by these strain gauges 24-27 while making the strain gauges positioned on mutually opposite sides of the bridge circuit detect strains in the same direction. Differential amplifiers 28-31 as a first voltage detector for detecting voltages between A-D respectively are connected on both ends of each strain gauge 24-27. Also, differential amplifiers 33, 34 for detecting voltage differences between the differential amplifiers 28, 30 and 29, 31 respectively are provided, forming a second voltage detector for detecting voltage differences by these. Further, abnormality signal output devices 35, 36 are connected to the differential amplifiers 33, 34 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a safety device for a power steering device that detects steering torque using a strain gauge and controls the output of an actuator according to the steering torque. .

(Prior Art) A device is conventionally known that controls a steering force by attaching a strain gauge to a drive unit or the like of a power steering device and converting the strain detected by the strain gauge into torque.

(Problems to be Solved by the Present Invention) However, the power steering device using this strain gauge does not have a means for detecting a break in the circuit system of the strain gauge. Therefore, if the circuit system is disconnected, there is a problem that an accurate torque signal cannot be obtained.

An object of the present invention is to provide a safety device that automatically detects a failure when a failure occurs in a circuit system using a strain gauge.

(Means for Solving Problems) The present invention is based on a power steering device that detects steering torque using a strain gauge and controls an actuator such as an electric motor in accordance with the detected signal.

Based on the above device, the present invention configures a bridge circuit using strain gauges with equal resistance values, and
While the strain gauges located on opposite sides of the bridge circuit detect strain in the same direction, the voltage difference between the first voltage detector that detects the voltage at the end of each of these strain gauges and the strain gauge on the opposite side is detected. a second voltage detector that detects the
The present invention is characterized in that it includes an abnormal signal output device that outputs an abnormal signal when this voltage difference occurs.

(Operation of the present invention) Since the present invention is configured as described above, when the strain gauges provided on opposite sides of the bridge circuit are functioning normally, the voltage difference between the two strain gauges becomes zero. If one of the strain gauges is disconnected, the above voltage difference occurs, and when such a voltage difference occurs, the abnormality signal output device functions.

(Effects of the Present Invention) According to the safety device of the present invention, when the strain gauge is disconnected, a signal is output from the abnormality signal output device, so that the abnormality can be detected.

If an abnormality can be detected in this way, it will not only be possible to immediately repair the abnormality, but it will also be possible to stop the power steering system and switch to manual steering.

(Embodiment of the present invention) Figures 1 to 7 show a first embodiment, in which the wheel l is
It is connected to a steering link 3 via a knuckle arm 2. A rack 4 is formed on this steering link 3, and
This rack 4 has a pinion 5 formed on a pinion shaft 5.
a is engaged with a pinion 7 provided at the tip of an output shaft 6 of an electric motor m.

The pinion shaft 5 is rotatably supported by two bearings 9 and 10 provided in the gear box 8, as shown in FIG. Moreover, both these bearings9.
10 forms a gap 13.14 between it and the bearing insertion hole 11.12 of the gear box 8, and within this gap 13.14, the pinion shaft 5
allows it to oscillate.

In addition, the reference numeral 15 in the figure is a pressure pad, which is attached to the rack 4.
This is for bringing the pinion 5a into pressure contact with the pinion 5a.

In the pinion shaft 5 constructed as described above, a swing lever 18 is provided outside the bearing 9. This swing lever 16 has a ring portion 18 formed above its fulcrum 17 and an action portion 19 formed above this ring portion 18. The pinion shaft 5 is inserted through the ring portion 18. There is. Therefore, when the pinion shaft 5 swings, the swing lever 16 swings about the fulcrum 17.

Further, the tip of the acting portion 18 is inserted into an insertion hole 21 formed in the reaction force spool 20. As is clear from FIG. 5, this anti-casbourg 20 has a spring 22 acting on one end thereof, and the insertion hole 22
A leaf spring 23 is provided inside the lever 1, and the tip of the leaf spring 23 is fixed to the operating portion 18 of the swing lever.

A pair of strain gauges 24 to 27 are respectively attached to the front and back sides of the leaf spring 23 constructed as described above. These strain gauges expand and contract in length depending on the amount of deflection of the leaf spring 23, and have different resistance values depending on the length. However, when the lengths of these strain gauges are equal, in other words, when the leaf spring 23 is straight, the resistance values of the strain gauges 24 to 27 are made equal.

The strain gauges 24 to 27 constructed in this way form a bridge circuit as shown in FIG. Strain gauges 26 and 27 attached to the right side of the leaf spring 23 are also located on opposite sides.

A first voltage detector of the present invention is provided at both ends of each of the strain gauges 24 to 27 of the bridge circuit to detect voltages between A and 0, between C and B, between B and D, and between D and A. In addition to connecting the differential amplifiers 28 to 31, a differential amplifier 32 for detecting the voltage between A and B of the bridge circuit is also connected.

Further, a differential amplifier 33 for detecting the voltage difference between the differential amplifiers 28 and 30 and a differential amplifier 34 for detecting the voltage difference between the differential amplifiers 29 and 31 are provided. 33 and 34 function as the second voltage detector of the present invention.

Note that each of the differential amplifiers 28 to 34 has a gain of 1.
I'm trying to make it happen. However, it goes without saying that the gain does not need to be 1 as long as matching is achieved.

Differential amplifier 3 as a second voltage detector as described above
An abnormal signal output device 35.36 is connected to 3.34, and this abnormal signal output device 35.36 is configured so that the absolute value of the output signal of the differential amplifier 33.34 is lower than the constant value C1. Detect whether it is large or small. When the absolute value is smaller than or equal to the constant value C1, a normal signal is output, and in the opposite case, an abnormal signal is output. Furthermore, these abnormal signal output devices 35.3
6 is connected to an OR gate 37, and this OR gate 37 is configured to output a fail-safe signal.

Note that the output signal of the differential amplifier 32 is input to the controller 38, and this controller 38 inputs the output signal of the differential amplifier 32, that is, the strain gauges 24 to 27.
The electric motor m is controlled according to the output signal from the electric motor m.

Therefore, when the input shaft 40 is turned together with the handle 38,
In connection with this, the pinion shaft 5 also rotates, but at this time, the turning resistance of the wheel 1 acts, so the rack 4 does not move.
Only the pinion 5a rolls on the rack 4, and the pinion shaft 5
is oscillated within the range of the above-mentioned clearance 13.14. When the pinion shaft 5 swings in this manner, the swing lever 16 swings around the fulcrum 17, and the reaction force spool 20
While moving against the spring 22, the spool 20 stops at a position where the spring force of the spring 22 is balanced. The spring force when the spring 22 is bent in this way is proportional to the steering torque. In other words, the swing lever 16 swings in proportion to the steering torque, and the leaf spring 23 swings in proportion to the amount of swing.
The amount of curvature will also be determined.

For example, if the left side of the leaf spring 23 is curved, the strain gauges 24 and 25 provided on the left side are contracted, and the strain gauges 26 and 27 provided on the right side are expanded. Therefore, the resistance value of the strain gauge 26.27 on the right side increases from R to R+ΔR, and conversely, the resistance value of the strain gauge 24.25 on the left side decreases from R to R−ΔR.

Note that when the leaf spring 23 is not bent, the resistance value is 1, and the resistance values of all the strain gauges 24 to 27 are equal to R, so the voltage between A and B of the bridge circuit is 0.

However, if the resistance value changes as described above, the voltage between A and B becomes EX(ΔR/R), and a voltage proportional to the change in resistance value is obtained. In response to this voltage signal, the controller 3 operates to drive the electric motor m.

When the electric motor m is driven in this manner, the pinion 7 rotates together with the output shaft 6, so that the rack 4 is moved and the wheels 1 are steered by the driving force of the electric motor m.

When the strain gauges 24 to 27 that function as described above come off, they function as follows.

That is, if the leaf spring 23 bends to the left, the voltage between A and B becomes E (ΔR/R) as described above, which becomes the steering torque signal, but the voltage across each strain gauge at this time is It changes as follows.

A-C voltage = E((1/2)-(ΔR/2R))C-
Voltage between B = E ((1/2) + (ΔR/2R)) Voltage between B and D = E ((1/2) - (ΔR/2R)) Voltage between D and A = E ((1/2 )+(ΔR/2R)) Since the strain gauges 24 and 25 are attached to the same side of the leaf spring 23, the amount of change in resistance, that is, the amount of voltage change, should be approximately equal.

The same can also be said about the strain gauges 26 and 27.

Therefore, if the voltages across the strain gauges 24 and 25 are detected by the differential amplifiers 28 and 30, and the difference between the voltages detected by the differential amplifiers 28 and 30 is detected by the differential amplifier 33, Output voltage v of the differential amplifier 33
A becomes O. Further, if the voltage across the strain gauges 26, 27 is detected by the differential amplifiers 29, 31, and the voltage difference detected by these two differential amplifiers 29, 31 is detected by the differential amplifier 34, the differential Output voltage V of amplifier 34
e also becomes 0.

If the strain gauge 24 is now separated from the leaf spring 23, ΔR of the strain gauge 24 will no longer occur. Therefore, the voltage between A and 0 becomes E/2, and the voltage between B and D
A difference is generated with the inter-mold pressure, and the voltage output from the differential amplifier 33 becomes V^=ΔR/2R, which is no longer zero.

Then, whether or not this signal VA is zero is determined by the abnormality signal output device 35, but it is determined by the absolute value IVA of the voltage concerned.
It is determined whether + is smaller or larger than a certain value C1. If this absolute value IVA1 is smaller than the constant value C1, a normal signal (0) is output, and if it is larger than the constant value CI, an abnormal signal (1) is output.

Note that the OR gate 37 operates when an abnormal signal is output from either one of the abnormal signal output devices 35 and 36.
It is configured to output a fail-safe signal. When this fail-safe signal is output, either the electric motor is stopped or an alarm signal is issued, but either method may be used.

The second embodiment shown in FIG. 8 is similar to the first embodiment except that strain gauges 24 to 27 are provided on the action portion 18 of the swing lever 16.

In the third embodiment shown in FIG. 9, the rack 4 is moved by a power cylinder 41, and the power cylinder 41 is connected to a pump 43 and a tank 44 via an electromagnetic control valve 42. The electromagnetic control valve 42 is connected to the controller 38.

Therefore, in this third embodiment, the electromagnetic control valve 42 is controlled by the output signal of the controller 38, and the flow rate supplied from the pump 43 is controlled.

The configuration other than the above is the same as that of the first embodiment.

[Brief explanation of the drawing]

Drawings 1 to 7 show a first embodiment of this invention.
Figure 1 is a mechanical diagram of the power steering system, Figure 2 is a sectional view of the part that detects the steering torque, and Figure 3 is the m-
Figure 4 is a cross-sectional view taken along the line IV-IV in Figure 2, Figure 5 is a cross-sectional view taken along the line V-V in Figure 2, and Figure 6 is a side view of the leaf spring with the strain gauge attached. 7 is a circuit diagram, FIG. 8 is a sectional view corresponding to FIG. 5, and FIG. 9 is a mechanical diagram of a power steering device according to a third embodiment. 24-27...Strain gauge, 28-31...Differential amplifier as first voltage detector, 33.34...Differential amplifier as second voltage detector, 35.36...Abnormality Signal output device, m...Electric motor as actuator, 41...Same figure 1 figure 63 figure fire 4 figure ta 5 figure

Claims (1)

[Claims] In a power steering device that detects steering torque with a strain gauge and controls an actuator such as an electric motor according to the detection signal, a bridge circuit is configured with strain gauges with equal resistance values, and a bridge circuit is configured with strain gauges having equal resistance values. While the strain gauges located on the sides detect strain in the same direction, a first voltage detector detects the voltage at the end of each of these strain gauges, and a second voltage detector detects the voltage difference between the strain gauges on the opposing sides. A safety device for a power steering device that includes a detector and an abnormal signal output device that outputs an abnormal signal when this voltage difference occurs.