JPH0130417B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a torque sensor, and more particularly to a torque detection device for detecting torque transmitted from a rotating shaft of a machine.

[Conventional technology]

As a device for detecting the torque of a shaft that transmits rotational power, for example, as shown in Japanese Patent Application Laid-Open No. 56-107140, gears are provided at both ends of the shaft,
There is a system in which a magnetic detection type sensor is provided in close opposition to both gears, and the torsion angle of the shaft is determined from the phase difference between the signal voltages generated by both the sensors.

[Problems to be Solved by the Invention] However, in the above device, when the rotational speed of the shaft is low, the signal voltage level becomes low and the phase detection error becomes large. Another problem was that external electromagnetic induction noise affected the magnetic circuit.

An object of the present invention is to provide a torque detection device that can detect rotations from low to high rotations with high accuracy and is not affected by electromagnetic induction noise.

[Means to solve the problem]

In order to achieve the above object, the torque detection device of the present invention forms a main optical path parallel to the axis of the rotating shaft, a light source faces one end of the main optical path, and a light receiving path faces the other end. In addition to placing each
The diameter d, length l, and transverse elastic modulus G of the rotating shaft,
The transmission torque τ of the rotating shaft is calculated from the pulse period T ₂ and pulse width t of the light received by the light receiver and the pulse period T ₂₀ and pulse width t ₀ measured in advance under no load using the following relational expression τ=π ² d ⁴ G/16l (t ₀ /T ₂₀ −t/T ₂ ).

[Effect]

According to the above configuration, when the rotating shaft is rotating,
The light from the light source becomes a light pulse when it enters the main optical path, and this light pulse is received by the light receiver after passing through the main optical path. At this time, if a transmission torque is applied to the rotating shaft, the rotating shaft is twisted, and the width t of the pulse received by the light receiver changes.
Therefore, after determining the diameter d, length l, and transverse elastic modulus G of the rotating shaft in advance, and measuring the pulse width T ₂₀ and pulse width t ₀ under no load, the above pulse width t and If we detect the pulse period T ₂ at that time,
It is possible to calculate the transmitted torque τ using the following relational expression τ=π ² d ⁴ G/16l (t ₀ /T ₂₀ −t/T ₂ ).

〔Example〕

Examples of the present invention will be described below.

FIG. 1 shows an embodiment of the invention.

In the figure, the rotational force of an engine 1 is transmitted to an output shaft 4 via a clutch means 2 and a reduction gear 3.
The speed reducer 3 includes gears 3a, 3b, 3c, and 3d and a power transmission shaft 5. The transmitted torque is measured on this power transmission shaft 5. A light receiving means 25 is disposed close to the left end of the power transmission shaft 5 in the radial direction of the shaft, and a light source 6 is disposed close to the right end of the power transmission shaft 5 in the radial direction of the shaft.
These light source 6 and light receiving means 25 are electrically connected to the circuit section 9. An enlarged cross-section of the power transmission shaft 5 is shown in FIG. A hole 16 is made in the center of the power transmission shaft 5, and a main optical path 20 is embedded therein. Holes are provided in the radial direction at both ends of the power transmission shaft 5 so as to pass through the holes 16, and the incident optical path 2 is inserted into the holes.
1 and a light receiving path 23 are embedded. These optical paths 2
A clad layer having a refractive index smaller than that of the optical path is provided on the outer periphery of each of the 0, 21, and 23 optical paths, and the light travels while being totally reflected in these clad layers. A total reflection mirror 22 is installed at the joint between the incident optical path 21 and the main optical path 20.
A total reflection mirror 24 is inserted into the joint portion of the main optical path 20 and the light receiving path 23. When light enters the incident optical path 21 from the light source 6, the light travels in the direction of an arrow. The light source 6 continuously emits light, but while the opening of the incident optical path 21 faces the light source 6,
The light enters the incident optical path 21, is reflected by the total reflection mirror 22, passes through the main optical path 20, is reflected by the total reflection mirror 24, passes through the light receiving path 23, and hits the light receiving means 25. FIG. 3 is a cross-sectional side view of the right end portion of FIG. 2, and when a load is applied to the main power shaft 4, the power transmission shaft 5 is twisted and the light receiving path 23 is displaced as shown by the broken line. The arrow indicates the direction of rotation of the shaft, and the twist angle θ is proportional to the torque τ. When the diameter of the power transmission shaft 5 is d, the length is l, and the transverse elastic modulus is G, the torque τ and torsion angle θ are calculated by the following formula, τ = (π/32)・d ⁴・G・θ/l …… It is expressed by equation (1). A photodiode or a phototransistor can be used as the light receiving means 25.
The input signal voltage of the input optical path and the light receiving means 2
FIG. 7 shows the light reception signal voltage of No. 5. In the same figure, a shows an incident signal that enters the incident optical path 21, and has a time width T ₁ ,
It is a pulse with a period T ₂ , and b in the figure shows the light receiving means 25.
The output signal is a pulse with a time width t and a period _T2 , and c in the figure is a phase difference pulse generated from both signals by a circuit described later. Time width T of phase difference pulse
The torsion angle θ is obtained from the period T ₂ and the period T 2 as follows: θ=2πT/T ₂ . . . Equation (2).

The light reception time t is maximum when there is no load. that value
If t _n , then t _n can be determined by measuring the period T ₂₀ of the output signal and the light receiving time t ₀ at no load in advance.
Time T corresponding to twist angle θ under load (Fig. 7c)
can be determined by the time formula.

T=(t ₀ /T ₂₀ )T ₂ −t ...Equation (3) From equations (1), (2), and (3), τ=π ² d ⁴ G/16・l(t ₀ /T ₂₀ − t/T ₂ )...Formula (
4) Therefore, the torque τ can be found using equation (4).

Next, the circuit shown in FIG. 8 will be described. power supply 40
Power is supplied from the resistor 41 to a series circuit of a light emitting diode 6' serving as a light source, a phototransistor 8 serving as a light receiving means, and a resistor 43. The light emitting diode 6' continuously emits light, but the phototransistor 8 receives light only when the power transmission shaft 5 rotates and the incident optical path 21 corresponds to the light source 6. At this time, the phototransistor 8 becomes conductive, and a pulse is applied to both ends of the resistor 43. This signal voltage pulse is sent to the counter 51. Further, the signal pulse of the phototransistor 8 is applied to a flip-flop 50, and its output is sent to a counter 52. Inverters 47, 48, resistors 44, 45, and capacitor 46
A clock pulse is generated by an oscillation circuit consisting of the following, and is applied to counters 51 and 52. Counter 51 counts time T shown in FIG. 7c, and counter 52 counts _T2 . These counted values of T and T ₂ are sent to the signal processing section 53.
The signal processing section 53 can be configured with a microcomputer. Here, the values of T and T ₂ are read, calculations are made using equations (2) and (3), and the calculated value of torque τ is output to an output boat (not shown).

FIG. 4 shows an improved sensor of the embodiment shown in FIG.
A light source 6 and a light receiving means 25 are arranged at positions facing the end faces of the optical fiber. The optical fiber 31 is fixed in the groove 32 with an adhesive 33 to prevent it from coming out due to centrifugal force caused by high-speed rotation of the power transmission shaft 5. 5 and 6 are left and right side views of the power transmission shaft 5, in which both end faces of the optical fiber 31, that is, the openings for light incidence and light output, have an outer diameter relative to the center of the power transmission shaft 5. Since it is located on the side, when the light source 6 is made to continuously emit light, the incident light occurs while the light source 6 and the opening of the optical fiber 31 are facing each other. Light is also emitted during this time, but if the power transmission shaft 5 is twisted, the time during which the emitted light hits the light receiving means 25 will be shorter than when there is no twist.

In this embodiment as well, the torque τ can be determined using equation (4), similar to the embodiment shown in FIG.

Therefore, according to this embodiment, the structures of the optical path and the power transmission shaft are simplified and can be manufactured at low cost.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a machine using the torque sensor of the present invention, FIG. 2 is a cross-sectional structural diagram showing one embodiment of the torque sensor of the present invention, and FIG. 3 is a cross-sectional side view of the right end of FIG. 4, 5, and 6 are cross-sectional structural diagrams and left and right side views showing other embodiments, FIG. 7 is a detection signal waveform diagram, and FIG. 8 is a circuit diagram. 5... Power transmission shaft, 6... Optical axis, 25... Light receiving means.

Claims (1)

[Scope of Claims] 1. A main optical path is formed parallel to the axis of the rotation axis, and a light source is arranged to face one end of the main optical path, and a light receiver is arranged to face the other end, and the rotation axis From the diameter d, length _l , and transverse elastic modulus _{G of} Transmission torque τ of rotating shaft
A torque detection device characterized in that it is provided with a calculation means for determining τ=π ² d ⁴ G/16l (t ₀ /T ₂₀ −t/T ₂ ) using the following relational expression.