JP2001074572A - Torque detector for power steering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make steering feeling constant, irrespective of the temperature. SOLUTION: This torque detector 10 is provided with a torque sensor 12, a temperature sensor 14, a signal processing part 16 and the like. The torque sensor 12 outputs an electrical signal varied in response to a torque value applied to a steering shaft. The temperature sensor 14 measures temperatures of the torque sensor 12 and a PS(power steering) device 18. The signal processing part 16 corrects the electrical signal output from the torque sensor 12 to be output to the PS device 18, based on the temperatures detected by the temperature sensor 14, a temperature characteristic of the torque sensor 12 and a temperature characteristic of the PS device 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering torque detecting device used for power steering for reducing the steering force of a vehicle. Hereinafter, the power steering is abbreviated as “PS” and the torque detecting device for power steering is simply abbreviated as “torque detecting device”.

[0002]

2. Description of the Related Art A general torque detecting device includes a torque sensor that outputs an electric signal that changes according to a torque value applied to a steering shaft, and an electric signal corresponding to the torque value based on the electric signal output from the torque sensor. To extract P
And a signal processing unit for outputting to the S device.

[0003] Further, in a conventional torque detecting device, there is known a device in which an electric signal output from a torque sensor is corrected by a temperature compensation circuit to improve reliability (for example, Japanese Patent Application Laid-Open No. 2-195221). No.).

[0004]

However, in a PS device using such a torque detecting device, even if the torque value obtained from the torque detecting device becomes accurate with respect to a temperature change, the driver's steering feeling can be improved. However, there is another problem that the temperature varies depending on the temperature. Specifically, the return of the steering wheel, the sense of viscosity, the sense of inertia, and the like differ depending on the temperature.

[0005]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a torque detecting device capable of improving the steering performance by keeping the steering feeling constant regardless of the temperature.

[0006]

SUMMARY OF THE INVENTION The present inventor has noticed that the problem of steering feeling in a PS device using a conventional torque detecting device lies in the temperature characteristics of the PS device. In other words, in the PS device, the steering force increases as the temperature decreases (that is, the steering force decreases as the temperature increases), so that the steering feeling differs depending on the temperature. The reason may be that the viscosity of grease such as gears and bearings constituting the PS device increases due to a decrease in temperature. The present invention has been made based on this finding.

A torque detecting device according to the present invention includes a torque sensor, a temperature sensor, and a signal processing unit. The torque sensor outputs an electric signal that changes according to a torque value applied to the steering shaft. The temperature sensor measures the temperature of the PS device. The signal processing unit corrects the electric signal output from the torque sensor based on the temperature detected by the temperature sensor and the temperature characteristics of the PS device, and outputs the corrected electric signal to the PS device.

[0008] The electric signal corresponding to the torque value and the temperature is:
Output from the torque sensor and the temperature sensor to the signal processing unit. The signal processing unit corrects the electric signal output from the torque sensor by considering the temperature characteristics of the PS device, and converts the corrected electric signal (that is, the torque value) to the PS signal.
Output to the device. The PS device operates to reduce the steering force according to the torque value. At this time, since the torque value used in the PS device is corrected based on the temperature characteristics of the PS device, the steering feeling becomes constant regardless of the temperature.

The temperature sensor includes a torque sensor and a P sensor.
The temperature of the S device may be measured. in this case,
The signal processing unit corrects the electric signal output from the torque sensor based on the temperature detected by the temperature sensor, the temperature characteristic of the torque sensor, and the temperature characteristic of the PS device, and
It may be output to the S device.

[0010] The electric signal corresponding to the torque value and the temperature is:
Output from the torque sensor and the temperature sensor to the signal processing unit. The signal processing unit corrects the electric signal output from the torque sensor by considering not only the temperature characteristic of the torque sensor but also the temperature characteristic of the PS device, and sends the corrected electric signal (ie, torque value) to the PS device. Output. PS
The device operates to reduce the steering force according to the torque value. At this time, since the torque value used in the PS device is corrected based on the temperature characteristics of the PS device, the steering feeling becomes constant regardless of the temperature.

For example, the temperature characteristic of the PS device means that the steering force increases as the temperature decreases (in other words, the steering force decreases as the temperature increases). At this time, the signal processing unit, based on the temperature detected by the temperature sensor,
The electric signal is corrected so as to cancel the increase in the steering force due to the temperature drop. The electric signal that cancels the increase in the steering force is, for example, an electric signal corresponding to the torque value that is equal to or larger than the torque value actually applied to the steering shaft.

The signal processing section may determine when the torque value applied to the steering shaft is decreasing based on the electric signal output from the torque sensor, and correct the electric signal at that time. The time when the torque value applied to the steering shaft is decreasing is a so-called “when the steering wheel returns”. If the steering force increases due to a decrease in temperature, the steering wheel may not return to a predetermined position when the steering wheel returns. In such a case, the electric signal is corrected so as to cancel the increase in the steering force.

[0013]

FIG. 1 is a block diagram showing an embodiment of a torque detecting device according to the present invention. Hereinafter, description will be made based on this drawing.

The torque detecting device 10 according to the present embodiment includes a torque sensor 12, a temperature sensor 14, a signal processing unit 16, and the like. The torque sensor 12 outputs an electric signal that changes according to a torque value applied to the steering shaft (sensor shaft 124). The temperature sensor 14 measures the temperatures of the torque sensor 12 and the PS device 18. The signal processing unit 16
Based on the temperature detected by the temperature sensor 14, the temperature characteristics of the torque sensor 12, and the temperature characteristics of the PS device 18,
The electric signal output from the torque sensor 12 is corrected, and the output voltage Vt is output to the PS device 18. Although the signal processing unit 16 is provided in the torque detection device 10,
It may be provided in the EPS controller 48 (FIG. 2) of the PS device 18.

First, the basic operation of the torque detecting device 10 will be described.

An electric signal corresponding to the torque value and the temperature is:
Signal processing unit 1 from torque sensor 12 and temperature sensor 14
6 is output. The signal processing unit 16 includes the torque sensor 12
The electric signal output from the torque sensor 12 is corrected by considering not only the temperature characteristic of the PS device 18 but also the temperature characteristic of the PS device 18, and the corrected electric signal (that is, torque value) is output to the PS device 18. The PS device 18 operates to reduce the steering force according to the torque value. At this time, since the torque value used in the PS device 18 has been corrected based on the temperature characteristics of the PS device 18, the steering feeling is constant regardless of the temperature.

Next, each component of the torque detecting device 10 will be described.

The torque sensor 12 is of a magnetostrictive type, and includes an excitation source 121, excitation coils 122 and 123, a sensor shaft 12
4. It is composed of detection coils 125, 126 and the like.
The sensor shaft 124 is made of a ferromagnetic material such as iron, nickel, or an alloy thereof. When torque is applied to the sensor shaft 124, tensile stress and compressive stress are applied in a direction of ± 45 degrees with respect to the center line of the sensor shaft 124. There is a difference in the magnetic permeability between the direction in which the tensile stress is applied and the direction in which the compressive stress is applied due to the magnetostriction phenomenon. That is, torque can be detected by detecting the difference in the magnetic permeability.

Therefore, the excitation coils 122 and 123 and the detection coils 125 and 126 are arranged on the surface of the sensor shaft 124, and the excitation coils 122 and 123 are excited by the AC voltage of the excitation source 121. Then, AC voltage values corresponding to the magnetic permeability in the tensile direction and the magnetic permeability in the compression direction are separately obtained from the detection coils 125 and 126, respectively. Therefore, if these AC voltages are rectified and smoothed and converted to DC, the difference between them corresponds to the torque value applied to the sensor shaft 124.
Although not shown, the sensor shaft 124 is connected between an input shaft attached to a steering wheel and an output shaft attached to a steering mechanism such as a pinion and a rack. Note that the temperature characteristics of the torque sensor 12 are due to the fact that the physical properties of the excitation coils 122 and 123, the sensor shaft 124, the detection coils 125 and 126, etc. change with temperature.

The temperature sensor 14 is an electronic circuit including a thermistor, an operational amplifier, and the like.
The temperature of the S device 18 is measured directly or indirectly. The thermistor (not shown) is mounted on, for example, a circuit board, and the resistance value changes according to the temperature of the torque sensor 12 and the PS device 18. Then, the temperature sensor 14 outputs a voltage corresponding to the resistance value of the thermistor to the arithmetic and control circuit 30.

The signal processing unit 16 includes detection coils 125, 1
A rectifier circuit 19 for rectifying the AC voltage output from
20, a comparison circuit 22 for taking the difference between the output voltages of the rectifier circuits 19 and 20, a smoothing circuit 24 for converting the output voltage of the comparison circuit 22 into DC, a gain adjustment circuit 26 for correcting the output voltage of the smoothing circuit 24, and a midpoint adjustment circuit 28, an arithmetic control circuit 30 having functions such as temperature correction and voltage monitoring, an analog voltage output circuit 32 that operates based on an output signal of the arithmetic control circuit 30, and the like. The gain adjustment circuit 26 and the midpoint adjustment circuit 28 are configured by, for example, an A / D converter and a D / A converter. Arithmetic control circuit 30
Is composed of, for example, a microcomputer and an E ² PROM.

The arithmetic and control circuit 30 stores in advance data relating to gain and midpoint fluctuation (temperature characteristics of the torque sensor 12) and temperature characteristics of the PS device 18 due to temperature fluctuations. Then, the arithmetic and control circuit 30 controls the gain adjustment circuit 26 based on the output signal of the temperature sensor 14.
And outputs a correction signal to the midpoint adjustment circuit 28. When a predetermined torque value is applied or when the torque value is zero, the arithmetic control circuit 30 sends a correction signal to the gain adjustment circuit 26 and the middle point adjustment circuit 28 so that the gain and the middle point are correct. Output.

Further, the arithmetic and control circuit 30 includes a resistor 30
1,302, the output voltage of the smoothing circuit 24,
The output voltage and the like of the midpoint adjustment circuit are input, and these voltages are monitored. When the arithmetic control circuit 30 determines that the voltage is abnormal, the analog voltage output circuit 32 outputs high (for example, 5 [V]) or low (for example, 0 [V]).

FIG. 2 is a block diagram showing a PS device 18 using the torque detecting device 10 of FIG. Hereinafter, description will be made based on this drawing. However, the same parts as those in FIG.

The steering wheel 40 is connected to a steering input shaft 42, and a sensor shaft 124 is connected between the steering input shaft 42 and the steering output shaft 44. In the handle column housing 46, in addition to the steering input shaft 42, the sensor shaft 124, the steering output shaft 44, and the torque detection device 10, an EPS controller 48, an electric motor 50 controlled by the EPS controller 48, an electric motor A gear 52 fitted on the output shaft of the motor 50, a gear 54 fitted on the steering output shaft 44 and meshing with the gear 52, a steering output shaft 4
4, the bearings 561 and 562 provided on the steering input shaft 42, and the like are accommodated. Although the EPS controller 48 and the electric motor 50 are provided inside the handle column housing 46, they may be provided outside the handle column housing 46.

When torque is applied to the steering wheel 40, the steering input shaft 24 → the sensor shaft 124 →
The force is transmitted to the steering output shaft 44. The torque detector 10 converts a torque value applied to the sensor shaft 124 into an output voltage Vt, and outputs the output voltage Vt to the EPS controller 4.
8 is output. The EPS controller 48 outputs the output voltage V
At t, an assist amount is calculated based on a vehicle speed signal and an ignition-on signal (not shown), and a control signal C is sent to the electric motor 50. Then, the electric motor 50 rotates, so that the steering output shaft 4 is driven through the gears 52 and 54.
4. Apply rotational force to 4. Thus, the steering force on the steering wheel 40 is reduced.

FIG. 3 is a graph showing the relationship between the applied torque and the output voltage in the torque detector of FIG.
[1] is a first example, and FIG. 3 [2] is a second example. Hereinafter, the operation of the torque detection device 10 will be described more specifically with reference to FIGS.

The PS device 18 has a temperature characteristic that the steering force increases as the temperature decreases, or conversely, the steering force decreases as the temperature increases. At this time, the signal processing unit 16 corrects the output voltage Vt based on the temperature detected by the temperature sensor 14 so as to cancel the increase in the steering force due to the temperature decrease. The “applied torque” here refers to the steering shaft (the sensor shaft 12).
4) is the torque value actually applied.

In the first example shown in FIG. 3 [1], for the same applied torque T, the gain is set such that the output voltage Vt increases as the temperature decreases (so that the output voltage Vt decreases as the temperature increases). To adjust. That is, as the temperature decreases, the assist amount is increased by increasing the output voltage Vt. FIG. 3A shows one example for each of low temperature, normal temperature, and high temperature. In practice, for example, -30 ° C
Applied torque T and output voltage Vt every 1 ° C up to 60 ° C
Is stored in an E ² PROM or the like.

In the second example shown in FIG. 3B, when the applied torque T is decreasing, the same applied torque T
The gain is adjusted so that the output voltage Vt increases as the temperature decreases (so that the output voltage decreases as the temperature increases). If the steering force increases due to a decrease in temperature, the steering wheel may not return to a predetermined position when the steering wheel returns. In such a case, in this example, the output voltage Vt is corrected so as to cancel the increase in the steering force. Note that FIG.
[2] shows an example at a low temperature. Actually, a map indicating the relationship between the applied torque T and the output voltage Vt is stored in an E ² PROM or the like, for example, every 1 ° C. from −30 ° C. to 60 ° C.

The output voltage Vt in FIGS. 3 [1] and [2] and FIG. 7 described later is intended to correct only the influence of the temperature characteristics of the PS device 18 for easy understanding. However, the actual output voltage Vt is
The correction of the temperature characteristic is also taken into account.

FIG. 4 is a graph showing an example of the operation of the torque detection device 10 based on the relationship shown in FIG. FIGS. 5 and 6 show a torque detection device 1 based on the relationship of FIG.
11 is a flowchart showing the operation of the "0". Hereinafter, the operation of the torque detection device 10 will be described more specifically with reference to FIG. 1 and FIGS. 3 [2] to 6.

First, the output voltage Vt 'before correction is input (step 101 in FIG. 5). If Vt ′ ≧ Va1, the process proceeds to Vt ′ ≦ Va2, and if not, the process returns to step 101. Constant voltage Va1, Va2
Corresponds to the applied torque T for determining whether or not to correct the output voltage Vt ′ when the steering wheel returns. That is, if the applied torque T is equal to or less than a predetermined value, no problem occurs when the steering wheel returns, and thus the output voltage Vt ′ is not corrected.

In FIG. 6, it is determined whether or not the output voltage Vt 'before correction has changed from increasing to decreasing (step 201). If the output voltage Vt 'is increasing, the next output voltage Vt' is input (step 202), and the process returns to step 201. If the output voltage Vt 'changes from increasing to decreasing, it is determined that the steering wheel is returning, the output voltage Vt' at that time is set to the peak voltage Vp1, and it is determined whether or not Vt '≦ Vb1 (step 203). . Where Vb
1 = 2.5 + (Vp1-2.5) × 0.9.

If Vt'≤Vb1, the next output voltage Vt 'is input (step 204) and step 203
Return to If Vt ′ ≦ Vb1, correction of the output voltage Vt ′ is started by changing the gain (step 20).
5). Subsequently, it is determined whether or not Vt ′ ≦ Vc1 (step 206). Here, Vc1 = 2.5 + (Vp
1-2.5) × 0.1. If not Vt ′ ≦ Vc1, the next output voltage Vt ′ is input (step 20).
7) Return to step 206. If Vt ′ ≦ Vc1, the output voltage Vt ′ is corrected by returning the gain to the original value (step 208), and the process returns to step 208.

In FIG. 6, it is determined whether or not the output voltage Vt 'before correction has changed from decreasing to increasing (step 301). If the output voltage Vt 'is decreasing, the next output voltage Vt' is input (step 302), and the process returns to step 301. If the output voltage Vt 'changes from decreasing to increasing, it is determined that the steering wheel is returning, the output voltage Vt' at that time is set to the peak voltage Vp2, and it is determined whether or not Vt '≧ Vb2 (step 303). . Where Vb
2 = 2.5− (2.5−Vp2) × 0.9.

If Vt ′ ≧ Vb2, the next output voltage Vt ′ is input (step 304), and step 303
Return to If Vt ′ ≧ Vb2, the output voltage Vt ′ is corrected by changing the gain (step 30).
5). Subsequently, it is determined whether or not Vt ′ ≧ Vc2 (step 306). Here, Vc2 = 2.5− (2.
5-Vp2) * 0.1. If Vt '≧ Vc2, the next output voltage Vt' is input (step 30).
7) Return to step 306. If Vt ′ ≧ Vc2, the output voltage Vt ′ is corrected by returning the gain to the original value (Step 308), and the process returns to Step S308.

FIG. 7 is a graph showing a third example of the relationship between the applied torque and the output voltage in the torque detector of FIG. Hereinafter, description will be made based on this drawing.

In the first and second examples shown in FIG. 3, the output voltage Vt 'is corrected by changing the gain. On the other hand, in the present example, the output voltage Vt ′ is corrected by changing the offset voltage (midpoint voltage). FIG. 7 shows an example at a low temperature. In practice, for example, -30 ° C to 6
A map indicating the relationship between the applied torque T and the output voltage Vt is stored in an E ² PROM or the like at every 1 ° C. up to 0 ° C.

[0040]

According to the torque detecting device of the present invention,
By measuring the temperature of the PS device and correcting the electric signal output from the torque sensor based on the temperature characteristics of the PS device stored in advance and outputting it to the PS device, the influence of the temperature characteristics of the PS device is removed. Therefore, the steering feeling can be made constant regardless of the temperature. Therefore, the steering performance with respect to the temperature change can be improved.

According to the torque detecting device of the second aspect,
Measure the temperature of the torque sensor and the PS device, and based on the previously stored temperature characteristics of the torque sensor and the PS device,
By correcting the electric signal output from the torque sensor and outputting the corrected signal to the PS device, not only the influence of the temperature characteristic of the torque sensor but also the effect of the temperature characteristic of the PS device are removed, so that the steering feeling is not affected by the temperature. Can be constant. Therefore, the steering performance with respect to the temperature change can be further improved. According to the torque detecting device of the second aspect,
The number of components does not increase compared to the conventional torque detection device that corrects only the influence of the temperature characteristics of the torque sensor.

According to the torque detecting device of the third aspect,
Since the electric signal output from the torque sensor is corrected so as to cancel the increase in the steering force due to the decrease in temperature, P having a temperature characteristic in which the steering force increases as the temperature decreases.
In contrast to the S device, the steering feeling can be made constant regardless of the temperature.

According to the torque detecting device of the fourth aspect,
By judging when the torque value applied to the steering shaft is decreasing and correcting the electric signal at that time, it is possible to prevent the steering wheel from returning to a predetermined position when the steering wheel returns.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a torque detection device according to the present invention.

FIG. 2 is a configuration diagram showing a PS device using the torque detection device of FIG.

3 is a graph showing a relationship between an applied torque and an output voltage in the torque detection device of FIG. 1, wherein FIG. 3 [1] is a first example and FIG. 3 [2] is a second example.

FIG. 4 is a graph showing an example of an operation based on the relationship of FIG. 3 [2] in the torque detection device of FIG.

FIG. 5 is a flowchart showing an operation based on the relationship of FIG. 3 [2] in the torque detection device of FIG. 1;

FIG. 6 is a flowchart showing an operation based on the relationship of FIG. 3 [2] in the torque detection device of FIG. 1;

FIG. 7 is a graph showing a third example of the relationship between the applied torque and the output voltage in the torque detection device of FIG.

[Description of Signs] 10 Torque detection device 12 Torque sensor 14 Temperature sensor 16 Signal processing unit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Eiji Tanaka 300th Takatsukacho, Hamamatsu-shi, Shizuoka Suzuki Co., Ltd. F-term (reference) 3D033 CA11 CA16 CA28

Claims (4)

[Claims] A torque sensor that outputs an electric signal that changes in accordance with a torque value applied to a steering shaft; a temperature sensor that measures a temperature of a power steering device; a temperature detected by the temperature sensor; And a signal processing unit that corrects an electric signal output from the torque sensor based on a temperature characteristic of the device and outputs the corrected signal to the power steering device. 2. A torque sensor for outputting an electric signal that changes in accordance with a torque value applied to a steering shaft; a temperature sensor for measuring the temperatures of the torque sensor and the power steering device; a temperature detected by the temperature sensor; A signal processing unit that corrects an electric signal output from the torque sensor based on a temperature characteristic of the torque sensor and a temperature characteristic of the power steering device, and outputs the corrected electric signal to the power steering device. apparatus. 3. The temperature characteristic of the power steering device is such that the steering force increases with a decrease in temperature, and the signal processing unit is configured to determine whether the temperature of the power steering device is lower based on the temperature detected by the temperature sensor. The torque detection device for power steering according to claim 1 or 2, wherein the electric signal is corrected so as to cancel the increase in the steering force. 4. The signal processing unit determines, based on the electric signal output from the torque sensor, when the torque value applied to the steering shaft is decreasing, and corrects the electric signal at that time. Item 4. A torque detecting device for power steering according to item 3.