JP2003057133A - Torque sensor - Google Patents

Abstract

(57) [Problem] To provide a torque sensor that can be easily mounted with a small number of parts by using a temperature detecting coil, can detect temperature without bulk at low cost. SOLUTION: A pair of coaxially arranged torque detecting coils 11, 12 whose inductances change in opposite directions according to torque, and the pair of torque detecting coils 11, 12 are provided.
And a torque detecting means for outputting a torque detection voltage from a voltage based on each inductance change of the torque sensor. A torque sensor characterized by being coaxially disposed around the same.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor for detecting torque based on a change in inductance of a pair of coils.

[0002]

2. Description of the Related Art In such a torque sensor, the coil itself has a temperature characteristic, and temperature changes due to thermal expansion of components of the torque sensor, such as the entire housing, affect the torque detection output to accurately detect the torque. Hindering

Therefore, a temperature sensor such as a thermistor dedicated to temperature detection is provided in the torque sensor, and the value of the detected torque is corrected by the temperature detected by the temperature sensor.

[0004]

Since the thermistor or the like detects the temperature of the torque sensor, it must be attached to the torque sensor so that the temperature can be detected with high sensitivity, and a substrate or a holding component for holding the thermistor is required for the attachment. Therefore, the number of parts is large, the mounting work is troublesome and the cost is high, and the thermistor projects from the torque sensor main body and is bulky.

The present invention has been made in view of the above points,
The purpose thereof is to provide a torque sensor which can be easily attached with a small number of parts by using a temperature detecting coil, which is low in cost, and which can detect temperature without being bulky.

[0006]

In order to achieve the above object, the invention according to the first aspect of the present invention provides a pair of coaxially arranged torques whose inductances change in opposite directions depending on the torque. In a torque sensor including a detection coil and a torque detection unit that outputs a torque detection voltage from a voltage based on each inductance change of the pair of torque detection coils, a temperature detection coil whose resistance value changes with temperature is A torque sensor is characterized in that it is coaxially provided around a pair of coaxial torque detection coils.

Since the temperature detecting coil whose resistance value changes depending on the temperature is used and is coaxially provided in the vicinity of the pair of coaxial torque detecting coils, it can be easily mounted with a small number of parts and is low in cost and bulky.

Therefore, it is not necessary to attach the temperature sensor to the torque sensor, so that no special substrate or holding parts are required, and the number of parts can be reduced and the cost can be reduced.

According to a second aspect of the present invention, in the torque sensor according to the first aspect, the temperature detecting coil is provided around the outer circumference of the pair of torque detecting coils.

Since the temperature detecting coil is provided around the outer circumference of the pair of torque detecting coils, it can be mounted without a special substrate or holding parts, the number of parts can be reduced, and it is not bulky.

According to a third aspect of the present invention, in the torque sensor according to the first aspect, the temperature detecting coils are circumferentially provided adjacent to each other in the axial direction of the pair of torque detecting coils.

Since the temperature detecting coil is circumferentially provided adjacent to the pair of torque detecting coils in the axial direction, the temperature detecting coil can be mounted without a special substrate or holding parts, the number of parts can be reduced, and it is not bulky. .

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. The torque sensor 1 according to the present embodiment is applied to a power steering device of a vehicle, and its schematic structure is shown in FIG.

An input shaft 3 and an output shaft 4, which are rotatably supported in the housing 2 via bearings 5 and 6 and are coaxially inserted, are internally connected by a torsion bar 7. The cylindrical core 8 is provided on the outer peripheral surface of the large-diameter end portion 4a of the output shaft 4 by serration fitting so as to be slidable only in the axial direction with respect to the output shaft 4, and is provided so as to project from the input shaft 3. A pin 9 penetrates a long hole in the circumferential direction of the large-diameter end 4a and engages with the spiral groove 8a of the core 8.

Two torque detecting coils 11 and 12 supported inside the housing 2 are provided on the outer periphery of a cylindrical core 8 which slides in the axial direction, with a space therebetween. The two torque detection coils 11 and 12 are arranged on the opposite sides with respect to the center of axial movement of the core 8.

When a torsional force acts on the input shaft 3, the rotational force is transmitted to the output shaft 4 via the torsion bar 7,
The torsion bar 7 is elastically deformed and a relative displacement in the rotational direction occurs between the input shaft 3 and the output shaft 4. This relative displacement in the rotational direction causes the core 8 to slide in the axial direction through the engagement between the slider pin 9 and the spiral groove 8a.

When the core 8 moves in the axial direction, the area surrounding each core 8 of the torque detecting coils 11 and 12 changes,
As one area increases, the other area decreases. When the area surrounding the core 8 increases, the magnetic loss increases and the inductance of the coil decreases. Conversely, when the area surrounding the core 8 decreases, the magnetic loss decreases and the inductance of the coil increases.

Therefore, the core 8 is the torque detecting coil 11
When a torque that moves to the side acts, the inductance L1 of the torque detection coil 11 decreases, the inductance L2 of the torque detection coil 12 increases, and conversely, the torque that the core 8 moves to the torque detection coil 12 side. When is applied, the inductance L1 of the torque detection coil 11 increases and the inductance L2 of the torque detection coil 12 decreases.

A temperature detecting coil 45 is provided around the outer circumference of the torque detecting coils 11 and 12. The temperature detecting coil 45 is a coil formed of a thermistor whose resistance value changes with temperature.

A torque detecting coil 11 of the torque sensor 1,
A torque detection circuit 20 for detecting torque based on changes in the inductances L1 and L2 of 12 and a temperature detection circuit 40 by the temperature detection coil 45 are shown in FIG. 2 as a schematic configuration diagram.

The torque detecting coils 11 and 12 are connected at one end to each other, and a signal line extends from the connecting end and each other end, and is connected to a connecting terminal of a torque detecting circuit 20 provided in the electronic control unit ECU. .

In the torque detection circuit 20, the connection ends of the torque detection coils 11 and 12 are grounded, and the other ends are respectively resistive.
It is connected to the emitter terminal of the transistor 15 via 13, 14. The transistor 15 has a collector terminal to which a constant voltage is applied, and a base terminal to which an AC voltage is input.

The voltage signal line 16 extending from the connecting portion between the torque detecting coil 11 and the resistor 13 is connected to the smoothing circuit 23 via the capacitor 21, and extends from the connecting portion between the torque detecting coil 12 and the resistor 14. The voltage signal line 17 is connected to the smoothing circuit 24 via the capacitor 22.

That is, the torque detecting coils 11 and 12, the resistance
A bridge circuit is configured by 13, 14 and an oscillating voltage is input to the bridge circuit, and its output voltage is smoothed by the smoothing circuits 23, 24.
Is input to, and smoothed and output as the first and second voltages V ₁ and V ₂ .

The first and second voltages V ₁ and V ₂ are input to the inverting input terminal and the non-inverting input terminal of a differential amplifier 27, which is an operational amplifier, via resistors 25 and 26, respectively. Differential amplifier 27
Negative feedback is applied by a resistor 28 to function as a differential amplifier, and its output is CP as a torque detection voltage Vt.
Input to U30. The bias voltage V ₀ is input to the non-inverting input terminal of the differential amplifier 27.

Therefore, the differential amplifier 27 receives the first voltage V ₁
And the second voltage V ₂ are multiplied by an amplification degree A to obtain a bias voltage V ₀
Is output as the torque detection voltage Vt. That torque detection voltage _{Vt, Vt = (V 2 -V 1} ) a · A + _{V 0.}

The neutral torque detection voltage Vt that is not biased to either the right steering torque (torsion torque in the right direction) or the left steering torque (torsion torque in the left direction) is called the neutral point voltage, and is normal. At this time, the bias voltage V ₀ becomes the neutral point voltage.

The torque sensor 1 has the schematic circuit configuration as described above, and its operation is performed with the first and second voltages V ₁ and V _2.
Also, description will be made below with reference to FIG. 3 showing the state of the torque detection voltage Vt. In the coordinates shown in FIG. 3, the vertical axis is the voltage, the horizontal axis is in the right direction and the horizontal axis is in the left steering torque, and the origin 0 is the neutral point.

FIG. 3 shows the case where the torque sensor 1 operates normally. When the right steering torque increases, the input shaft 3
The core 8 moves toward the torque detection coil 11 side by the relative rotation of the output shaft 4 and the torque detection coil 11 to increase the inductance L2 of the torque detection coil 12 to increase the induced electromotive force thereof, and conversely the torque detection coil 11 since smaller the induced electromotive force decreases the inductance L1, the second voltage V ₂ increases, the first voltage V ₁ is reduced (see FIG. 3).

When the left steering torque increases, the second voltage V ₂ decreases and the first voltage V ₁ increases, contrary to the above (see FIG. 3). Therefore, the torque detection voltage Vt, which is the output of the differential amplifier 27 obtained by multiplying the difference between the two by A and adding the bias voltage, becomes an upward-sloping slope line that passes through the bias voltage V ₀ at the neutral point, as shown in FIG. .

The steering torque to the left and right can be detected from the torque detection voltage Vt based on the sloped line of the torque detection voltage Vt shown in the graph of FIG.

The CPU 30 outputs a motor control instruction signal to the motor driver 31 based on the torque detection voltage Vt, and the motor 32 assists steering by the motor driver 31.
Is driven. Therefore, in the steering operation, the assistance of the motor 32 according to the steering torque can be obtained.

In the power steering control mechanism as described above, the temperature change of the torque detecting coils 11 and 12 itself is canceled by the differential amplifier 27, but the housing or core which is an assembly part thereof is used. The effect of temperature change due to thermal expansion of itself is unavoidable.

Therefore, the torque sensor 1 is provided with a temperature detecting circuit 40. As shown in FIG. 2, the temperature detection circuit
In 40, the resistor 41 is connected to the temperature detection coil 45 in series,
The other end of the resistor 41 is pulled up to a constant voltage, and the other end of the temperature detecting coil 45 is grounded.

A temperature detection voltage Vs is output from the connection point between the resistor 41 and the temperature detection coil 45 and input to the CPU 30. The voltage divided by the resistor 41 having a constant resistance value and the temperature detecting coil 45 whose resistance value changes with temperature is output as the temperature detection voltage Vs. The temperature detection voltage Vs is digitally converted and used by the CPU 30 for temperature correction.

Therefore, when the temperature detection voltage Vs is input to the CPU 30 from the temperature detection circuit 40, the CPU 30 corrects the torque detection voltage Vt based on the temperature detection voltage Vs to accurately correct the temperature including components. Various steering torques can be detected and used for driving the motor 32.

The torque sensor 1 in this embodiment is
As described above, the temperature detection coil 45 is the torque detection coil.
Since it is installed around the outer circumference of 11 and 12, the torque detection coil 1
In the process of winding 1 and 12, finally the temperature detection coil 45
If it is wound continuously, it can be easily and efficiently installed, and workability is good. Also, the torque detection coil
The temperature change of the housing itself in which 11 and 12 are installed can be detected efficiently.

Further, since a special substrate for attaching the temperature detecting coil 45 and a holding component are not required, the number of components can be reduced and the cost can be reduced. Further, the torque sensor 1 does not become bulky as the diameter of the main body increases slightly.

In the above embodiments, the temperature detecting coil is used.
Although 45 is provided around the outer circumferences of the torque detection coils 11 and 12, the same effect can be obtained even if the temperature detection coils are provided adjacently in the axial direction of the pair of torque detection coils. You can

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a mechanical portion of a torque sensor according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an electric circuit of the torque sensor.

FIG. 3 is a diagram showing states of first and second voltages and a torque detection voltage in a normal state.

[Explanation of symbols]

1 ... Torque sensor, 2 ... Housing, 3 ... Input shaft, 4 ...
Output shaft, 5, 6 ... Bearing, 7 ... Torsion bar, 8
... core, 9 ... slider pin, 11, 12 ... torque detection coil, 13, 14 ... resistance, 15 ... transistor, 16, 17 ... voltage signal line, 20 ... torque detection circuit, 21, 22 ... capacitor, 23,
24 ... Smoothing circuit, 25, 26 ... Resistor, 27 ... Differential amplifier, 28 ... Resistor, 30 ... CPU, 31 ... Motor driver, 32 ... Motor, 40
… Temperature detection circuit, 41… Resistance, 45… Coil for temperature detection.

Claims (3)

[Claims] 1. A pair of coaxial torque detection coils whose inductances change in opposite directions depending on torque, and a torque detection voltage from a voltage based on each inductance change of the pair of torque detection coils. A torque sensor having a torque detecting means for outputting, wherein a temperature detecting coil whose resistance value changes depending on temperature is coaxially provided around the pair of coaxial torque detecting coils. 2. The torque sensor according to claim 1, wherein the temperature detecting coil is provided around outer circumferences of the pair of torque detecting coils. 3. The torque sensor according to claim 1, wherein the temperature detecting coils are circumferentially adjacent to each other in the axial direction of the pair of torque detecting coils.