JPH04248428A - Torque detector - Google Patents

Abstract

PURPOSE:To measure torque with high accuracy by taking out a torque signal without receiving the effect of a drive shaft. CONSTITUTION:The capacitance of a capacitor is changed corresponding to the twist of a torsion bar and torque is detected based on the change quantity thereof. As compared with the case due to electromagnetic coupling, the change in capacitance of the capacitor can be largely taken and, as a result, torque can be measured with high accuracy. Further, the capacitance of a variable capacitor 2 composed of the same constitution is compared with that of a fixed capacitor 3 and, by detecting torque based on the difference in capacitance, the change in capacitance accompanied by an environmental change is set off even if it is generated and torque can be measured with high accuracy.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a torque detector;
In particular, the present invention relates to a torque detector that detects torque by capturing the torsional angle between a transmission shaft and a transmitted shaft as a change in capacitance.

0002

[Prior art and problems to be solved by the invention] Conventionally,
Torque detectors are used in various technical fields, and in automobiles, they are used in the following manner. For example, when a driver operates the steering wheel, a torque detector detects the torque applied to the steering shaft and its direction of rotation, and then a motor or the like applies force to the steering shaft in the direction of rotation, allowing easy steering with low torque. I'm trying to make it possible.

In such a so-called power steering device, for example, a torsion bar is provided as a torque detector between the steering shaft and the drive shaft, and a potentiometer is further attached to the steering shaft or the drive shaft to detect the difference between the steering shaft and the drive shaft. There is a method that detects the twist between the two parts based on the amount of rotation of a potentiometer. In this method, the potentiometer rotates as the steering shaft rotates, so it is conceivable to extract the potentiometer signal via a slip ring or via an electric wire long enough to accommodate multiple forward and reverse rotations. Considering the steering shaft of an automobile, which rotates frequently, it was not suitable in terms of durability, reliability, etc.

[0004] To avoid such problems of contact type,
Systems that are unaffected by the rotation of the steering shaft and take out signals without contact have also been proposed in, for example, Japanese Patent Application Laid-Open No. 63-292029 and Japanese Patent Application Laid-Open No. 1-140036. In this method, a torsion bar is interposed between the steering shaft and the drive shaft, and a magnetic body and a detection coil are provided for electromagnetic coupling between the steering shaft side and the drive shaft side, and the torsion of the torsion bar is detected by the detection coil. This is detected as a change in electromagnetic coupling.

However, in the electromagnetic coupling system, many other metal members are disposed close to the steering shaft and drive shaft inside the vehicle body, so it is difficult to make large changes in the electromagnetic coupling. However, the torque must be detected based on small changes, and the measurement accuracy is not always good.

The present invention has been made in order to solve these problems, and provides a torque detector in which the extraction of torque signals is not affected by the transmission shaft, driven shaft, etc., and can be measured with high precision. The purpose is to provide

[0007]

[Means for Solving the Problems] The torque detector of the present invention connects a transmission shaft and a transmitted shaft with a torsion bar, and detects torque based on the torsion of the torsion bar that occurs when the transmission shaft is rotated. In a torque detector, a blade-shaped shield plate attached to the transmission shaft or the transmitted shaft, a blade-shaped dielectric body attached to the transmitted shaft or the transmission shaft, and a blade-shaped shield plate placed on both sides of the shield plate and the dielectric body. The variable capacitor has a variable capacitor having a pair of fixed electrodes, and detecting means detects a change in the capacitance of the variable capacitor and detects torque based on the change.

Another torque detector of the present invention is a torque detector that connects a transmission shaft and a transmitted shaft with a torsion bar and detects torque based on the torsion of the torsion bar that occurs when the transmission shaft is rotated. In the device, a blade-shaped shield plate attached to the transmission shaft or the transmitted shaft, a blade-shaped dielectric body attached to the transmitted shaft or the transmission shaft, and a pair of blade-shaped shield plates arranged on both sides of the shield plate and the dielectric body. A variable capacitor having a fixed electrode, a blade-shaped shielding plate and a blade-shaped dielectric body attached to the transmitted shaft or the transmission shaft, and a pair of fixing devices placed on both sides of the shielding plate and the dielectric body. A fixed capacitor with an electrode, a pair of resistors connected to a variable capacitor and a fixed capacitor to form a bridge circuit, and an unbalanced current in the bridge circuit is detected and the unbalanced current is detected. and detection means for detecting torque based on current.

Another torque detector of the present invention includes one fixed electrode of the pair of fixed electrodes of the variable capacitor in the torque detector, and one fixed electrode of the pair of fixed electrodes of the variable capacitor. One of the fixed electrodes is also used as one fixed electrode.

0010

[Operation] In the torque detector of the present invention, when a force is applied to the transmission shaft, the torsion bar is twisted. and,
The overlapping area between the shield plate and the dielectric changes depending on the twist. This overlap area, that is, the electrode area changes, and the capacitance of the capacitor changes. Torque is detected by detecting changes in the capacitance of this capacitor.

Further, in another torque detector of the present invention, the capacitance of the variable capacitor changes in the same manner as in the above case. On the other hand, each member of a fixed capacitance type capacitor is attached to the transmission shaft, and its capacitance does not change. In this bridge circuit that includes a variable capacitor and a fixed capacitor, when the capacitance of the variable capacitor changes, an unbalanced current flows, and its magnitude and direction correspond to the magnitude of torque and direction of rotation. It becomes what it is.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram of a torque detector according to an embodiment of the present invention. In the figure, 1 is an oscillator, 2 is a variable capacitor type capacitor, and 3 is a fixed capacitor type capacitor. 4 is an ammeter, and R is a resistance. These capacitors 2 and 3 and resistors R and R constitute a bridge circuit, and as described later, the capacitance of capacitors 2 and 3 is equal when no torque is generated, and at that time, the bridge circuit is balanced. Therefore, no current flows through the ammeter 4.

FIGS. 2 and 3 show a variable capacitance type capacitor 2.
FIG. 3 is a side view and a sectional view showing the configuration of a fixed capacitance type capacitor 3. FIG. In the figure, 10 is a steering shaft of the handle, and 11 is a drive shaft on the wheel side. 12 is the steering shaft 1
0 and the drive shaft 11. 13 to 15 are fixed electrodes each made of a disk-shaped metal plate with a hole in the center, and 16 is the fixed electrode 1.
It is a cylindrical support that supports numbers 3 to 15. 17 is a blade-shaped shielding plate attached to the steering shaft 10. 1
Reference numeral 8 denotes a wing-shaped dielectric body attached to the drive shaft 11, and the shielding plate 17 and this dielectric body 18 are arranged between the fixed electrodes 13 and 14 with a 1/2 pitch offset from each other. 19 is a vane-like dielectric attached to the drive shaft 11. 20 is a blade-shaped shielding plate attached to the drive shaft 11, and the dielectric 19 and this shielding plate 20 are 1/2 of each other.
It is arranged between fixed electrodes 14 and 15 with a pitch shift.

The fixed electrodes 13 and 14, the shielding plate 17 and the dielectric 18 arranged between the two fixed electrodes constitute the variable capacitance type capacitor 2 shown in FIG.
4 and 15, as well as the dielectric 19 and shielding plate 20 disposed between both fixed electrodes, constitute the fixed capacitance type capacitor 3 shown in FIG. In this embodiment, the fixed electrode 14
serves as the fixed electrode for both capacitors 2 and 3,
A fixed electrode may be provided corresponding to each capacitor.

FIG. 4 shows fixed electrodes 13 to 1 in the configuration shown in FIG.
5 is a perspective view of the shielding plate, dielectric material, etc., with the torsion bar 12 removed from the steering shaft 10, with the exception of the torsion bar 12 and the support 16. FIG. As shown in the figure, the shielding plate 17, the dielectric 18, the dielectric 19, and the shielding plate 20 each consist of wings attached to four positions in the circumferential direction of the shaft, and the sizes thereof are the same. When no force is applied to the steering shaft 10, the area where the shielding plate 17 and the dielectric 18 overlap is equal to the area where the dielectric 19 and the shielding plate 20 overlap. The dielectric 19 and the shielding plate 20 are coaxially attached to the drive shaft 11, and their overlapping area does not change. However, since the shielding plate 17 is attached to the steering shaft 10 and the dielectric body 18 is attached to the drive shaft 11, when the torsion bar 12 is twisted, the overlapping area changes in proportion to the angle of the twist.

FIG. 5 shows an exploded view of the support tool 16 of FIG.
FIG. 3 is a perspective view of the steering shaft 10 of the present invention and a state in which the members fixed thereto are removed.

Now that the mechanisms of the variable capacitance type capacitor 2 and the fixed capacitance type capacitor 3 have been clarified through the above explanation, the electrical characteristics will be explained next.

FIG. 6 is an explanatory diagram showing the electrical configuration of the variable capacitance type capacitor 2. The capacitor capacity of two parallel plates is determined by the following formula. C=0.0885(ε・A/d)×10-6(
μF) ... (1) ε: Dielectric constant A: Area of electrode d: Distance between both electrodes Here, the capacitance of the area where there is nothing between the fixed electrode 13 and the fixed electrode 14 is C1, and the capacitance between the fixed electrode 13 and the fixed electrode is C2 is the capacitance of the region where the dielectric 18 is interposed between the fixed electrodes 14, C3 is the capacitance between the fixed electrodes 13 and the shielding plate 17, and C3 is the capacitance between the fixed electrodes 13 and the shielding plate 17.
The capacitance between C4 and C4 is assumed to be C4.

As shown in the figure, the shielding plate 17 is +Δ or -Δ
When the capacitor C2 is moved by an amount of
~The capacitance of C4 changes. For example, in the case of a change of +Δ, the capacitance of capacitor C2 decreases and capacitor C
3. The capacity of C4 increases. Also, in the case of a change of -Δ, the capacitance of capacitor C2 increases, and the capacitance of capacitor C3 increases.
, C4 decreases.

FIG. 7 shows a circuit in which the capacitor shown in FIG. 6 is connected to an oscillation circuit. As shown in the figure, an oscillation circuit 1 is connected to a series circuit of a variable capacitance type capacitor 2 and a resistor R, and a shielding plate 17 of the capacitor 2 is connected to one terminal of the oscillation circuit 1.

FIG. 8 is an equivalent circuit of FIG. 7. Here, assuming that the output impedance of the oscillation circuit 1 is sufficiently low, the voltage across the capacitor C3 can be obtained from the following equation. V1=V0・Z2/(Z1+Z2)
...(2)
◎However, Z1 and Z2 are as follows. Z1=1/{ω(C1+C2)} Z2=R/{
1+ωC3R)}...(3) Now, when the shielding plate 17 changes by +Δ, the capacitance of the capacitor changes as described above, so if the impedance before the change is Z1 and the impedance after the change is Z1c, then , (3), Z1<Z1c and Z2<Z2c. Therefore, (2)
In the equation, if the voltage across the changing capacitor 3 is V1Δ, then V1>V1c, and V1c decreases in proportion to the value of Δ.

Similarly, when the shielding plate 17 changes by -Δ, V1<V1c, and V1c increases in proportion to the value of Δ.

Now that the function of the shielding plate 17 in the capacitor of FIG. 6 has been clarified as described above, if the equivalent circuit of FIG. 8 is applied to the bridge circuit of FIG. 1, an equivalent circuit as shown in FIG. 9 can be obtained. I understand that. In Figure 9, CO
corresponds to the capacitance of the capacitor which is the sum of C1 and C2 in FIG. 6, and COX corresponds to the capacitance corresponding to CO on the fixed capacitance type capacitor side. Further, C3X corresponds to the capacitance corresponding to C3 on the fixed capacitance type capacitor side. CO4
corresponds to the capacitance of the capacitor, which is the sum of C4 of the variable capacitor type capacitor and C4X corresponding to the value on the fixed capacitor side.

Next, the operation of this equivalent circuit is shown in FIGS. 10 to 16.
The explanation will be based on.

FIG. 10 is a characteristic diagram showing the relationship between the torque applied to the steering shaft 10 and the torsion angle of the torsion bar 12, and it can be seen that the torsion angle increases in proportion to the torque. This twist angle is usually about ±3° at maximum. Figure 1
1 is a characteristic diagram showing the relationship between the capacitance of capacitors C2 and C3 and the twist angle. As described above, as the twist angle changes in the +Δ direction, the electrode area A changes, the capacitance of the capacitor C3 increases, and the capacitance of the capacitor C2 decreases. Moreover, the opposite phenomenon is shown for the change in the -Δ direction.

FIG. 12 shows the torsion angle and the above-mentioned capacitor C3.
FIG. When the twist angle changes, the capacitances of the capacitors C2 and C3 change as described above, so that the voltage V1 across the capacitors changes linearly in proportion to the change in the twist angle.

Now, focusing on the equivalent circuit of FIG. 9 again, when no torque is applied to the steering shaft 10, capacitor CO and capacitor COX are equal, capacitor C3 and capacitor C3X are equal, and the ammeter In this case, the relationship between the fixed electrode 14 and the shielding plate 17 is as shown in FIG. 13. Next, when the shielding plate 17 changes in the +Δ direction, the voltage V1 across the capacitor C3 increases as described above, the potential of the terminal A shown in the figure becomes high, and the potential of the terminal B does not change, so from the terminal A to the terminal A current I flows toward B, and its magnitude increases in proportion to the twist angle, that is, in proportion to the magnitude of the torque. The relationship between the fixed electrode 14 and the shielding plate 17 at this time is as shown in FIG.

Next, when the shielding plate 17 changes in the -Δ direction, the voltage V1 across the capacitor C3 decreases as described above, the potential of the terminal A shown in the figure becomes low, and the potential of the terminal B does not change. A current I flows from terminal B to terminal A, and its magnitude increases in proportion to the twist angle, that is, in proportion to the magnitude of torque. Fixed electrode 14 at this time
The relationship between the shielding plate 17 and the shielding plate 17 is as shown in FIG.

FIG. 16 is a characteristic diagram showing the relationship between the current flowing through the ammeter 4 and the torque in the above operation.

In the above embodiment, the variable capacitance type capacitor 2 and the fixed capacitance type capacitor 3 have the same structure, and the unbalanced current by the bridge circuit is detected, so that changes in capacitance due to environmental changes etc. are avoided. Even if there is a difference, it changes in the same way, so there is no reduction in measurement accuracy, and highly accurate measurement can be performed.

Although the above-described embodiment shows an example in which the fixed capacitance type capacitor 3 is attached to the drive shaft 11, it goes without saying that a structure in which it is attached to the steering shaft 10 may also be used. Further, in the above-described embodiments, the detection of torque acting between the steering shaft and the drive shaft, that is, the torque in the steering wheel mechanism, was described, but the object of the present invention is not limited to such. , it goes without saying that the present invention is applicable to any mechanism in which the transmission shaft transmits torque to the transmitted shaft.

Furthermore, since the capacitance of the variable capacitor 2 may change if the relative position in the axial direction of its constituent members, such as the shielding plate 17, changes, the support 16
Alternatively, it is desirable to provide a mechanism for adjusting the relative casting position of the shielding plate 17 in the axial direction, and to periodically check the position and adjust the position if the position has shifted. Further, it goes without saying that the variable capacitance type capacitor 2 and the fixed capacitance type capacitor 3 are not limited to the configurations of the illustrated embodiments, but can be modified as appropriate depending on the purpose of the present invention.

[0033]

[Effects of the Invention] As described above, according to the invention of the present application, the capacitance of the capacitor is changed in response to the torsion of the torsion bar, and torque is detected based on the amount of change. In comparison, the change in capacity can be large, and as a result, torque can be measured with high precision. In addition, the capacitance of a variable capacitor with a similar configuration and the capacitance of a fixed capacitor are compared, and torque is detected based on the difference, so there is no capacitance change due to environmental changes. Even if it is canceled out,
Highly accurate measurements are now possible.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a torque detector according to an embodiment of the present invention.

FIG. 2 is a side view showing the configuration of the capacitor in FIG. 1;

FIG. 3 is a cross-sectional view showing the configuration of the capacitor shown in FIG. 1;

FIG. 4 is a perspective view of the shielding plate, dielectric material, etc. in FIG. 3;

FIG. 5 is a partially exploded perspective view of the capacitor of FIG. 3;

FIG. 6 is an explanatory diagram showing the electrical configuration of a variable capacitor type capacitor.

FIG. 7 is a circuit diagram in which the capacitor shown in FIG. 6 is connected to an oscillation circuit.

FIG. 8 is an equivalent circuit of FIG. 7;

FIG. 9 is an equivalent circuit of FIG. 1;

FIG. 10 is a characteristic diagram showing the relationship between torsion angle and torque.

FIG. 11 is a characteristic diagram showing the relationship between capacitance change and twist angle of a capacitor.

FIG. 12 is a characteristic diagram showing the relationship between the voltage across the capacitor C3 and the twist angle.

FIG. 13 is an explanatory diagram showing a state in which the shielding plate and the dielectric material overlap when no torque is applied to the steering shaft.

FIG. 14 is an explanatory diagram showing a state in which the shielding plate and the dielectric overlap with each other when a force in the +Δ direction is applied to the steering shaft.

FIG. 15 is an explanatory diagram showing an overlapping state of the shielding plate and the dielectric when a force in the -Δ direction is applied to the steering shaft.

16 is a characteristic diagram showing the relationship between the bridge current and torque in FIG. 9. FIG.

[Explanation of symbols]

2; Variable capacitor 3; Fixed capacitance type capacitor 10; Steering shaft 11; Drive shaft 12; Torsion bar 13, 14, 15; Fixed electrode 17, 20; Shielding plate 18, 19; dielectric

Claims (3)

[Claims] Claim 1. A torque detector that connects a transmission shaft and a transmitted shaft with a torsion bar and detects torque based on the torsion of the torsion bar that occurs when the transmission shaft is rotated. A variable capacitor having a blade-shaped shielding plate attached, a blade-shaped dielectric body attached to the transmitted shaft or the transmission shaft, and a pair of fixed electrodes arranged on both sides of the shielding plate and the dielectric body. , detects the change in the capacitance of this variable capacitor,
A torque detector comprising a detection means for detecting torque based on the change. 2. A torque detector that connects a transmission shaft and a transmitted shaft with a torsion bar and detects torque based on the torsion of the torsion bar that occurs when the transmission shaft is rotated. A variable capacitor having a blade-shaped shielding plate attached, a blade-shaped dielectric body attached to the transmitted shaft or the transmission shaft, and a pair of fixed electrodes arranged on both sides of the shielding plate and the dielectric body. , a fixed capacitance type capacitor having a blade-shaped shield plate and a blade-shaped dielectric body attached to the transmitted shaft or the transmission shaft, and a pair of fixed electrodes arranged on both sides of the shield plate and the dielectric body; A pair of resistors connected to the variable capacitance type capacitor and the fixed capacitance type capacitor to form a bridge circuit, and detection for detecting an unbalanced current in the bridge circuit and detecting torque based on the unbalanced current. A torque detector comprising means. 3. One fixed electrode of a pair of fixed electrodes of a variable capacitor type capacitor and one fixed electrode of a pair of fixed electrodes of a fixed capacitor type capacitor are connected to one fixed electrode of a pair of fixed electrodes of a variable capacitor type capacitor. 3. The torque detector according to claim 2, further comprising an electrode.