JP2745463B2 - Torque sensor - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a torque sensor for detecting a torsional torque applied to a rotating shaft.

[Conventional technology]

As a conventional torque sensor that detects the torque generated when rotating a rotating shaft, see "Automotive Technology" Vol.41 No.10
As shown on page 1206 of 1987, a device using a potentiometer is known. As shown in a schematic diagram in FIG. 4 and a sectional view taken along the line AA in FIG. 5, the torque sensor has a torsion bar having a small diameter and a torsion at the center of the rotating shaft bodies 11a and 11b for which torque is to be detected. A potentiometer 14 is mounted on a rotary plate 13 at one end. And the rotating plate 15 is also provided at the other end of the torsion bar 12.
A rod 16 parallel to the torsion bar 12 is attached to the rotating plate 15 at a predetermined distance from the rotating shaft. An operation piece of the potentiometer 14 is fixed to the tip of the rod 16. In this way, when the rotating shaft 11 is rotated, the torsion bar 12 causes the potentiometer 14 to slide right and left. Therefore, by detecting the amount of change, the torsional torque of the rotating shaft body is detected.

As shown in FIG. 6 (a), as a detection circuit connected to this potentiometer, for example, a positive voltage + V and a negative voltage -V are applied to both ends of the potentiometer, and the voltage at the middle point is amplified via the amplifier 17. In some cases, a torque signal is obtained by the following method. As shown in FIG. 6 (b), a detection circuit is also used in which one end of the potentiometer 17 is grounded, a positive voltage is applied only to the other end, and the voltage at the midpoint is detected via the amplifier 14.

[Problems to be solved by the invention]

However, in the detection circuit of FIG. 6 (a), when the line a or c of the potentiometer 14 constituting the torque sensor is disconnected, the output X obtained from the amplifier 17 is minimized regardless of the position of the potentiometer 14, that is, the actual torque. Or, it indicates the maximum value. Therefore, when power steering control or the like is performed by the torque signal of the potentiometer 14, there is a disadvantage that abnormal control is performed. If the line b is disconnected, the output X of the amplifier 17 becomes unstable. To prevent this, it is necessary to connect a resistor R1 shown by a broken line between the output terminal of the line b and the ground. Further, there is a disadvantage that the value of X becomes abnormal even when the contact of the potentiometer becomes defective, and furthermore, there is a disadvantage that two positive and negative power supplies are required for the detection circuit.

In the detection circuit shown in FIG. 6 (b), an abnormal output is obtained when the lines a and b of the potentiometer 14 are short-circuited to the ground, and also abnormal when the line b is short-circuited to a and c. Output is obtained. Then, in order to avoid the output fluctuation due to the short circuit of the line b, the resistors R2, R
It is conceivable to connect 3 between the power supply and the earth end,
Also in this case, there is a drawback that only the short circuit of the line b is effective and the torque output fluctuates greatly when the other line is short circuited. Therefore, in order to solve such a problem, it is necessary to mount a plurality of potentiometers on the rotating plate 3 and compare their values, resulting in a disadvantage that the structure becomes complicated.

The present invention has been made in view of the problem of such a conventional torque sensor using a potentiometer,
When an abnormality such as disconnection or poor connection of any one of the potentiometers occurs, it is a technical object to detect the abnormality in a short time so that the torque output can be reduced to zero.

[Means for Solving the Problems] The present invention relates to a torque sensor 2 for detecting a torsional torque applied to a rotating shaft body by a signal obtained from a potentiometer 1, a voltage source 3 for supplying a voltage to a sliding contact of the potentiometer, A pair of resistors 4 and 5 respectively connected between both ends of the potentiometer and a ground terminal, and a terminal voltage of each resistor of the pair of resistors is detected, and a determination is made as to whether a sum of those terminal voltages is a predetermined value. A means for calculating and outputting a torque signal based on the terminal voltage when the sum of the terminal voltages is determined to be a predetermined value by the determining means, and a torque value when the sum of the terminal voltages is not determined to be the predetermined value by the determining means; Calculation means 7 for outputting a torque signal with zero set to zero
And having the following.

[Action]

According to the present invention having such features, a voltage is supplied to the sliding contact of the potentiometer attached to the rotating shaft body, the sum of the voltages at both ends is calculated, and the torque sensor is determined based on whether the sum is a predetermined value. An abnormality has been determined. If the sum is a predetermined value, the torque is calculated based on the detected terminal voltage. If the sum is not the predetermined value, the torque output is set to zero.

〔The invention's effect〕

Therefore, according to the present invention, the abnormality of the potentiometer which is easily deteriorated is always identified, and if there is an abnormality, the torque signal can be immediately reduced to zero. Therefore, various controls are not performed based on the abnormal torque signal, and the reliability can be greatly improved. Further, there is no need to provide another torque sensor for identifying a disconnection, a short circuit, or the like, and the effect that the reliability of signals can be improved at low cost can be obtained.

[Explanation of Example]

Next, this embodiment will be described. Also in this embodiment, the configuration of the potentiometer itself is the same as that of the conventional example described above, and the description thereof is omitted. In this embodiment, as shown in FIG. 2, a potentiometer 14 constituting a torque sensor is used.
A constant voltage Vi is supplied from a voltage source to the sliding contact 14b. Here potentiometer 14 is the total resistance value V _R, to the partial pressure ratio alpha and (0 ≦ α ≦ 1). That αV the upper resistance than sliding contact _R, the lower the resistance (1-
it is assumed that the divide in α) V _R. And potentiometer
Resistors 4 and 5 having a constant resistance value R are connected between both ends 14a and 14c of 14 and a ground terminal, respectively, and the terminal voltages are applied to amplifiers 21 and 22. Amplifiers 21 and 22 amplify these voltage signals and supply them to microcomputer 25 via A / D converters 23 and 24. The microcomputer 25 is a one-chip computer having a built-in input / output interface, a memory, and the like. Is calculated, and the steering motor 27 is
To give to.

The outputs of the A / D converters 23 and 24 are converted into torque signals according to the flowchart shown in FIG. That is, when the microcomputer 25 starts operation, first,
At 31, the A / D converters 23 and 24 read the A / D conversion values X and Y. Then, the value is added and it is checked whether or not the added value becomes a predetermined value β. If each terminal of the potentiometer 14 is not broken, the β
Is given by the following equation.

If where _R >> V R A is, R, V for _R and the voltage Vi is constant β is substantially constant. Therefore, in step 32, the sum of the voltages X and Y is β
Is determined, and if β, it is determined that each terminal of the potentiometer is not disconnected. If the value of β is substantially constant, the routine proceeds to step 33, where the error counter is cleared. Here, the microcomputer 25 has achieved the function of the judging means 6 for judging whether or not the sum of the voltages at both ends of the potentiometer is a predetermined value in steps 32 and 33. Next, the routine proceeds to step 34, where the magnitudes of X and Y are compared. If X is large, the torque signal I is obtained by the following equation: I = k (X-1 / 2β) (step 35). If the value of Y is large, the routine proceeds to step 36, where the torque signal I is obtained by the following equation.

I = −k (Y−1 / 2β) If the sum of X and Y is not the predetermined value β in step 32, the process proceeds to steps 37 and 38, where the error counter in the microcomputer 25 is incremented and the count value becomes N
Check if you have reached If the count value has not reached N, the process returns to step 34 to compare the values of X and Y and perform the same processing. If the count value of the error counter exceeds N, the process proceeds from step 38 to step 39, where the torque signal I
To 0 to turn off the driving of the motor 27. In this way, even if any of the lines of the potentiometer 14 is broken, an abnormality is determined, so that the motor output can be turned off, and the power steering can be controlled based on a correct torque signal only in a normal case. Can be. Here, the microcomputer 25 calculates the torque value based on the voltage at both ends when the determination means 6 determines in step 34 to 39 that the sum of the voltages at both ends of the resistor matches the predetermined value, and calculates the torque value at both ends. When the sum is not determined to be the predetermined value, the function of the torque calculating means 7 for setting the torque value to zero is achieved. Here, in this embodiment, the torque value is calculated by calculation from the voltage between both ends of the potentiometer.
It is also possible to store a torque value corresponding to one of the values in, for example, a ROM table or the like, and thereby obtain the torque value.

Although the torque sensor according to the present embodiment has been described as applied to a power steering device, it goes without saying that the torque sensor according to the present invention can be applied not only to a power steering device but also to various other devices. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing a functional configuration of the present invention, FIG. 2 is a block diagram showing one embodiment thereof, FIG. 3 is a flowchart showing the operation of the present embodiment, and FIG. FIG. 5 is a side view showing an example of the potentiometer section, FIG. 5 is a sectional view taken along line AA, and FIGS. 6 (a) and 6 (b) are views showing an example of a detection circuit of a conventional torque sensor. 1,14 ... potentiometer, 2 ... torque sensor, 3 ...
... Voltage source, 4,5 ... Resistance, 6 ... Determination means, 7 ... Torque calculation means, 11a, 11b ... Rotating shaft body, 12 ... Torsion bar, 13,15 ... Rotating plate, 16 ... Rod, 21,22 ... Amplifier, 23,24 ... A / D converter, 25 ... Microcomputer, 26 ... Drive unit

Claims (1)

(57) [Claims] 1. A torque sensor for detecting a torsional torque applied to a rotating shaft body by a signal obtained from a potentiometer, a voltage source for supplying a voltage to a sliding contact of the potentiometer, and a voltage source between both ends of the potentiometer and a ground terminal. A pair of resistors respectively connected thereto, detecting means for detecting terminal voltages of the respective resistors of the pair of resistors, and determining whether or not the sum of the terminal voltages is a predetermined value; and determining the terminal voltage by the determining means. When the sum of the terminal voltages is determined to be a predetermined value, a torque signal is calculated and output based on the terminal voltage, and when the sum of the terminal voltages is not determined to be the predetermined value by the determination means, the torque signal is set to zero. And a torque calculating means for outputting the torque.