JP2622979B2 - Steering torque detection device and control method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering torque detection device having a neutral detection, adjustment, and failure notification function of a steering torque sensor.

[Conventional technology]

FIG. 6 shows a steering torque detection system to which a conventional steering torque detection device is applied. In the figure, reference numeral 20 denotes a steering torque detector, 21 denotes a constant current device that supplies a constant current to the Hall element 22, 23 denotes a differential amplifier, 30 denotes a slip ring, 40 denotes a controller, 41 denotes a CPU, and 42 denotes an A / D. The converter, T1 is a power supply terminal to which the vehicle side voltage is supplied, and T2 is a ground terminal.

In the steering torque detecting device configured as described above, a relative change of the torsion bar is detected as a position change between a magnet (not shown) and the Hall element 22 and amplified by the differential amplifier 23 to obtain the steering torque signal a. Is output to the slip ring 30. Controller 40 is slip ring 30
A / D converter 42 converts the steering torque signal a input through
Performs / D conversion to obtain steering wheel input torque and assists motor.

[Problems to be solved by the invention]

However, the steering torque detecting device having such a configuration has the following problem.

Since the power supply and the ground are not reliable due to the slip ring 30, the steering torque detecting device is not reliable. For example, if the power supply is momentarily interrupted, the output will drop abnormally.

It is necessary to maintain mechanical accuracy, and the assemblability is poor.
It is even necessary to combine the controller 40 and the steering torque detector 20.

It is difficult to make electrical adjustments to set an input torque-free state having a hydraulic center meaning indicating neutrality of input shaft torque in hydraulic power steering.
The steering torque detector 20 is set in a narrow space,
Further, the adjustment of the neutral point is performed after the total assembly of the relative displacement portions. Therefore, use of a potentiometer for steering in a vehicle is inappropriate in terms of reliability. Therefore, the offset and the gain greatly change due to a mechanical error. The assembling accuracy required in this case requires extremely high accuracy of several microns or less in consideration of stacking with electrical errors.

If there is a voltage fluctuation, the output will be affected.

When the body (vehicle body) is grounded, the ground potential fluctuates when the horn is sounding.
It is impossible to use the body as a 20 ground. Therefore, three lines of the slip ring are necessary, the ring diameter of the slip ring becomes large, and the accommodation is deteriorated.

When receiving electromagnetic interference (EMI), the steering torque signal a
When a few volts are superimposed on the normal steering torque signal,
Since the output is at ~ 5 volts, the steering wheel is taken off.

[Means for solving the problem]

In order to solve such a problem, a steering torque detection device according to a first invention (an invention according to claim 1) detects a steering torque and outputs a steering torque analog signal, and a steering torque analog signal. A / D that converts digital signals into digital signals and outputs them as steering torque digital signals
A CPU having a converter, the CPU performs a correction operation on the steering torque digital signal with an offset adjustment value and a gain adjustment value set by a controller electrically connected via a slip ring, This is a serial output to the controller.

A control method of a steering torque detecting device according to a second invention (an invention according to claim 2) includes a communication start procedure in which a controller declares a start of communication to the steering torque detecting device of the first invention, and a torque from the steering torque detecting device to the controller. And a torque signal transmission / reception procedure for transmitting a signal.

According to a third aspect of the present invention, there is provided a control method of a steering torque detecting device, wherein the controller declares a start of communication to the steering torque detecting device of the first invention, and the controller adjusts the steering torque detecting device. An adjustment start procedure for declaring the start, a torque signal transmission / reception procedure for transmitting a torque signal from the steering torque detection device to the controller, and an adjustment value transmission / reception procedure for transmitting an offset adjustment value and a gain adjustment value from the controller to the steering torque detection device. It is intended to have.

[Action]

According to the steering torque detection device of the present invention, the CPU converts the steering torque analog signal from the steering torque sensor into a steering torque digital signal, and electrically converts the converted steering torque digital signal via the slip ring. After the correction calculation based on the offset adjustment value and the gain adjustment value set by the controller connected to the controller, the data is serially output to the controller.

〔Example〕

FIG. 1 is a system diagram showing one embodiment of a steering torque detecting device according to the present invention. In the figure, 1 is a constant voltage power supply, 2 is a constant current device, 3 is a Hall element, 4 is a differential amplifier,
5 to 7 are A / D converters, 8 is a status monitor, 9 is an offset adder, 10 is an address decoder, 11 is an EEPROM, 12 is a gain adjuster, 13 is a serial transmitter, 14 is a serial receiver,
Reference numeral 15 denotes a code decoder, 16 denotes a power supply backup, 17 denotes a multiplexer, T1 denotes a power supply terminal to which power is supplied, T2 denotes a ground terminal, T3 denotes an output terminal, and 41 denotes a CPU. The dynamic amplifier 4 forms a steering torque sensor. This torque sensor corresponds to a conventional steering torque detecting device. The terminals T1 and T3 are connected to a controller (not shown) via a slip ring (not shown).
Further, the voltage of the constant voltage power supply 1 is supplied to the constant current generator 2, the differential amplifier 4, the A / D converter 5, and the CPU 41, and a power supply backup 16 is prepared as a power supply backup for the CPU 41.

Next, the operation of the steering torque detecting device thus configured will be described. The vehicle-side voltage applied from the power supply terminal T1 is stabilized by the constant voltage power supply 1. The constant current device 2 makes the current flowing to the Hall element 3 constant. This is to guarantee the voltage dependency of the Hall element 3 and the temperature change. The output voltage of the Hall element 3 is amplified by the differential amplifier 4 and converted into a digital value by the A / D converter 6. When this value is passed to the offset adder 9, the offset adder 9
Outputs an address for extracting an offset amount (offset adjustment value) to the address decoder 10, and outputs the address to the EEPROM 11.
Is added to the result of the A / D converter 6. This addition result is passed to the gain adjuster 12, which outputs an address for extracting a gain correction value (gain adjustment value) to the address decoder 10,
A fixed-point type binary value is obtained from the EEPROM 11. The gain adjuster 12 adjusts a multiplication value for the output value of the offset adder 9.

The operation of the offset adder 9 and the gain adjuster 12 will be described with reference to FIG. In the figure, the horizontal axis represents torque, and the vertical axis represents A / D conversion values. L1 is a reference straight line indicating an ideal value. When the straight line based on the adjustment value obtained when torque is free and when torque is applied is L2, the straight line L2
Is subtracted from the deviation value a1 in the torque-free state, and the result of the subtraction is used as a value b1 (b1> 1) indicating the slope with respect to the reference curve.
Divide by. In the case of the straight line L3, a deviation value a2 in the torque-free state is added from the value of the straight line L3, and the addition result is multiplied by a value b2 (b2> 1) indicating a slope with respect to the reference curve. In this case, addition and subtraction are performed by the offset adder 9, and multiplication and division are performed by the gain adjuster 12.

When an output instruction is issued from the code decoder 15, the serial transmission unit 13 outputs this result. If the instruction code from the code decoder 15 is a specific code, the signal from the gain adjuster 12 is ignored and the code decoder 15
Outputs the instruction code from.

The A / D converter 5 monitors the power supply voltage after the constant voltage, and adjusts the output of the A / D converter 6 when the voltage drop of the vehicle side power supply occurs and also affects the output of the differential amplifier 4. By omitting transmission, erroneous data generated due to fluctuations in the power supply voltage is prevented from being transmitted. The A / D converter 7 monitors the output state from the constant current device 2 and responds to the error force of the Hall element output due to the abnormality of the constant current device 2.

The code decoder 15 receives the received contents or the state of the status monitor 8.
The fixed code output to the serial transmission unit 13 and the failure content from the state monitoring unit 8 are sent to the EEPROM 11 according to the input content from the CPU, and the content of the adjustment value is set in the address decoder 10 and the EEPROM 11. The multiplexer 17 is used for controlling input / output of a serial line connected to the terminal T3.

Next, the operation of the steering torque detection system to which the steering torque detection device shown in FIG. 1 is applied will be described with reference to FIG. 2 and FIG. FIG. 2 is an explanatory view showing a normal operation, and FIG.
The figure is an explanatory view showing the operation at the time of adjustment. In FIG. 2, reference numeral 20 denotes a steering torque detecting device, and reference numeral 40 denotes a controller. First, the controller 40 notifies the device 20 of a communication start declaration. The code in this case is $ A5, for example. Here, ＄ means hexadecimal. Next, a communication start acknowledge signal is sent to the device 20.
Is transmitted, the controller 40 transmits a torque signal transmission request signal, and in response, the device 20 transmits a torque signal (信号 XX). The controller 40 receives the torque signal, but if there is a parity error, sends a signal requesting retransmission, and the device 20 transmits the torque signal again. Finally, the controller 40 requests transmission of the torque signal again to confirm the torque signal, the device 20 sends out the torque signal, and the controller 40 receives the torque signal. Thereafter, the above operation is repeated. As described above, the normal communication procedure includes the communication start procedure and the torque signal transmission / reception procedure.

Next, the operation at the time of adjustment will be described with reference to FIG. 3 showing a communication procedure. The communication procedure is the first procedure S1 to the fourth procedure
The first procedure S1 is the same as the normal procedure except that there is an adjustment start declaration and a torque signal confirmation transmission request signal. The second and third procedures are the same as the ordinary procedure. In the fourth adjustment procedure, the controller 40 first declares the transmission of the adjustment value “a” and sends the adjustment value “a” to the device 20. Next, the device 20 performs a procedure for confirming the received content. Thereafter, the same operation is performed, and finally, the adjustment value “b” is received, and the communication procedure is terminated. By storing these adjustment values in the EEPROM 11, the CPU can control the A / D converter 6
Can be corrected. Thus, the third
The communication procedure shown in the figure comprises a communication start procedure, an adjustment start procedure, a torque signal transmission / reception procedure, and an adjustment value transmission / reception procedure.

The following effects are obtained from the above operation of the present embodiment.

The CPU 41 can detect these abnormalities even if the power supply of the steering torque detection device is momentarily disconnected, the power supply line is disconnected, the ground is disconnected, the ground line is disconnected, the signal is disconnected or the signal line is disconnected, Recovery is possible. In this case, the grounding may be the body grounding, and therefore the slip ring may be two wires, so that the accommodation is improved.

Since the adjustment value is sent from the controller 40 to the device 20, it is easy to adjust the steering torque detection device 20 during assembly.

Variations in mechanical assembly can be absorbed, and integration of the steering torque detection device 20 and the controller 40 becomes unnecessary.

Although the possibility of changing the controller 40 is large for each vehicle type, the possibility of changing the steering torque detecting device is small and mass production is possible.

The error history (error history) can be read from the EEPROM 11, which is convenient for failure analysis.

In the above embodiment, a capacitor is usually used for the power supply backup unit 16. However, if a rechargeable battery is used in place of the power supply capacitor, there is an effect that it is possible to cope with a momentary power interruption for a long time.

In the above embodiment, the detection of the steering torque has been described, but the present invention is not limited to this, and can be similarly applied to the detection of the steering angle. An example of this is shown in FIG. FIG. 5 shows a configuration in which the constant current device 2, the Hall element 3 and the differential amplifier 4 of FIG. 1 are replaced with a steering angle detecting potentiometer 18. In the figure, 19a and 19b are disconnection detection resistors.

〔The invention's effect〕

As described above, according to the steering torque detecting device of the first invention, a steering torque sensor that detects a steering torque and outputs it as a steering torque analog signal, and converts a steering torque analog signal into a digital signal to output a steering torque digital signal. A CPU having an A / D converter for outputting as a signal,
U performs a correction operation on the steering torque digital signal based on an offset adjustment value and a gain adjustment value set by a controller electrically connected via a slip ring, and then outputs the result to the controller in a serial manner. Thus, if an abnormality is detected and an error is corrected by the CPU, it is possible to prevent an erroneous signal from being generated via a slip ring, and it is not necessary to increase mechanical accuracy.

According to the control method of the steering torque detecting device of the second invention,
The controller is provided with a communication start procedure for declaring the start of communication to the steering torque detection device of the first invention and a torque signal transmission / reception procedure for transmitting a torque signal from the steering torque detection device to the controller. And the controller can be easily communicated.

According to the control method of the steering torque detecting device of the third invention,
A communication start procedure in which the controller declares the start of communication to the steering torque detection device of the first invention, an adjustment start procedure in which the controller declares start of adjustment to the steering torque detection device, and a torque signal transmitted from the steering torque detection device to the controller. By providing the torque signal transmission / reception procedure and the adjustment value transmission / reception procedure for transmitting the offset adjustment value and the gain adjustment value from the controller to the steering torque detection device, there is an effect that the adjustment of the steering torque detection device can be facilitated.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of a steering torque detecting device according to the present invention, FIG. 2 is an explanatory diagram for explaining a communication method between the steering torque detecting device and a controller, and FIG. FIG. 4 is an explanatory diagram for explaining an adjusting method of the torque detecting device, FIG. 4 is a graph for explaining an offset and gain adjusting method in the steering torque detecting device of FIG. 1, and FIG. 5 is a steering torque of FIG. FIG. 6 is a system diagram showing a steering angle detection device as a modification of the detection device, and FIG. 6 is a system diagram showing a steering torque detection system to which a conventional steering torque detection device is applied. 1 ... constant voltage power supply, 2 ... constant current device, 3 ... Hall element, 4 ... differential amplifier, 5-7 ... A / D converter, 8 ...
State monitoring unit, 9: Offset adder, 10: Address decoder, 11: EEPROM, 12: Gain adjuster, 13:
Serial transmission unit, 14: Serial reception unit, 15: Code decoder, 16: Power supply backup, 17: Multiplexer, T1: Power supply terminal, T2: Ground terminal, T3: Output terminal, 41: CPU .

Claims (3)

(57) [Claims] 1. A CPU having a steering torque sensor for detecting a steering torque and outputting it as a steering torque analog signal, and an A / D converter for converting the steering torque analog signal into a digital signal and outputting the digital signal as a steering torque digital signal. The CPU, after performing a correction operation on the steering torque digital signal by an offset adjustment value and a gain adjustment value set by a controller electrically connected via a slip ring, A steering torque detecting device, which outputs serially. 2. A method according to claim 1, wherein the controller includes a communication start procedure for declaring the start of communication to the steering torque detection device according to claim 1, and a torque signal transmission / reception procedure for transmitting a torque signal from the steering torque detection device to the controller. A control method for a steering torque detecting device, which is characterized by the following. 3. A communication start procedure in which a controller declares a start of communication to the steering torque detector according to claim 1, an adjustment start procedure in which the controller declares start of adjustment to the steering torque detector, and the steering torque detector. A torque signal transmission / reception procedure for transmitting a torque signal from the controller to the controller,
An adjustment value transmitting / receiving procedure for transmitting an offset adjustment value and a gain adjustment value from a controller to the steering torque detection device.