JPH028251B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting torque from the torsion angle of an elastic body such as a torsion bar or a coil spring.

Conventional torque meters that detect the torsion angle of an elastic body, such as a torsion bar, from the time difference between signals from an alternator or other signal generator attached to both ends of the torsion bar are usually not temperature-corrected.

However, FIG. 1 shows a block diagram of a conventional temperature compensation circuit for a torque meter in which a temperature sensor is added as a temperature compensation means.

1 is a torsion bar where torque is detected, 2
a and 2b are rotary gears fixed to both sides of the torsion bar 1; 3a and 3b are pick-ups that extract changes in magnetic flux due to the rotation of the rotary gears 2a and 2b as changes in voltage; 4 is a bearing; 5 is a housing; 6 is a temperature sensor , 7 is a phase detection circuit, 8 is a temperature detection circuit, 9 is a divider, 10 is a torque signal not corrected by temperature, 11 is a temperature signal, and 12 is a temperature-corrected torque signal.

The torque applied to the torsion bar 1 is detected by the phase detection circuit 7 as a phase difference between the voltages generated in the pickups 3a and 3b, and a temperature-uncorrected torque signal 10 is obtained. Further, a temperature detection circuit 8 detects the temperature from a temperature sensor 6 disposed near the torsion bar 1, and a temperature signal 11 is generated. Therefore, the temperature uncorrected torque signal 10 is converted into the temperature signal 11.
By dividing by a correction constant corresponding to , a corrected torque signal 12 is output as a torque meter output.

In this method, the temperature sensor 6 is connected to the torsion bar 1.
There is also a method of obtaining the temperature signal 11 by attaching it directly to an elastic body and using a slip ring or a rotating transformer (not shown) (for example,
−108930).

The disadvantages of these measures are: ○A A temperature sensor is required.

○B A signal transmission line for the temperature sensor must be installed.

Therefore, the price of equipment as equipment increases,
Additionally, there is a problem of reduced reliability due to temperature sensors and signal transmission lines such as cables.

SUMMARY OF THE INVENTION An object of the present invention is to overcome the drawbacks of conventional devices and provide a torque detection device that detects temperature and corrects the sensitivity of a torque meter without additionally installing a temperature sensor or cable as in conventional means. , its purpose.

Fig. 2 is a block diagram showing the configuration of an embodiment of the present invention, Fig. 3 is an explanatory diagram of the structure of the magnetoelectric converter (so-called pick-up), and Fig. 4 shows the temperature characteristics of the barium ferrite magnet (temperature-specific characteristics). FIG.

20 is a temperature correction circuit, which is composed of 22 rectifiers, 23 monostables, 24 dividers, 25 auxiliary signal (constant/bias) input terminals, and 26 adders. 21 is a phase detector, 27 is a speed output terminal, 28 is a multiplication circuit (gain control), 2
9 is a torque output end.

The pickups 3a and 3b are formed into a horseshoe shape by disposing a yoke 32 at both ends of a rod-shaped ferrite magnet 31, and a coil 33 is wound around the yoke 32.

When the rotating gears 2a and 2b of the torque meter rotate,
The magnetic flux flowing through the yokes 32 of the pickups 3a, 3b changes, and a pulse or alternating current voltage is induced in the coil 33.

When torque τ acts on the elastic body 1, a torsional displacement Δθ is generated. The torque τ is detected from the time difference or phase difference between the induced voltages of the two pickups 3a and 3b due to the torsional displacement Δθ. Δθ=K ₁・τ …(1) Here, K ₁ is the elastic modulus and rigidity modulus of the elastic body. The torsion flexibility is determined by the shape.

When the elastic body 1 is rod-shaped, K ₁ =32L/πD ⁴ G (2) where D is the diameter of the elastic body 1, L is the length, and G is the rigidity.

When the elastic body 1 is a coil spring, K ₁ =64Dn/d ⁴ E (3) where D is the diameter of the coil, n is the winding, d is the wire diameter of the coil, and E is Young's modulus.

In either case, torsional softness is inversely proportional to temperature changes in elastic modulus such as rigidity and Young's modulus.
K ₁ changes, and the torsion angle or sensitivity to unit torque changes.

Note that the test torque meter can be calibrated by preparing a separate torque meter that has already been calibrated and directly connecting it to it.
When the torque meter is calibrated at the standard temperature, the torsion angle for a predetermined torque τ is expressed as Δθ ₀ , and the torsion angle when the temperature difference from the standard temperature is T is expressed as Δθ.

When the temperature coefficient of the elastic body 1 is α, it is expressed as follows: G=G ₀ (1+αT) …(4) E=E ₀ (1+αT) …(5).

However, G ₀ is the rigidity modulus at standard temperature, and E ₀ is Young's modulus at standard temperature.

From equations (2) and (4), G ₀ (1 + αT) = 32L/πD ⁴・1/K ₁ , so K ₁ = 32L/πD ⁴ G ₀ 1/1 + αT = K ₁₀ /1 + αT …(6) Here, K ₁₀ is the torsional softness at standard temperature.

Also, the torque signal when torque τ is applied is
V〓, the torque signal when torque τ is applied at standard temperature is V〓 ₀ , then V〓=CΔθ=CK ₁ τ …(7) V〓 ₀ = CΔθJ=CK ₁₀ τ …(8) However, C is a constant determined by the phase detector 21.

Therefore, from formulas (7) and (8), V〓/V〓 ₀ = K ₁ /K ₁₀ = 1/1 + αT...(9) Therefore, the following formula can be obtained.

V〓=1/1+αTV〓 ₀ (10) Prior to the temperature change correction, the magnetic circuit around the pickups 2a and 2b in FIG. 3 will be explained.

Since the magnetic resistance of the magnetic materials of the yoke 32 and the rotating gear 2a can be ignored, the magnetic circuit around the pickup is as shown in FIG.

34 is a magnetic path formed in the rotating gear 2a, V _n
is the magnetomotive force, V _n =B _r L _n /μ _n L _n is the length of the ferrite magnet 31, B _r is the residual magnetic flux density, μ _n is the reversible permeability of the ferrite magnet 31, and R _n is the ferrite magnet 31. 31 magnetic resistance, R _L is the magnetic resistance of the leakage magnetic flux, R _G is the magnetic resistance in the gap, then the magnetic flux φ _G passing through the coil 33 is φ _G = V _n /R _n + (1+R/R) R _G …(11) The cross-sectional area of each magnetic path is the cross-sectional area of the magnet 31 A _n
, and if the effective magnetic path lengths corresponding to the magnetic resistance values of the leakage flux magnetic path and the gap magnetic path are L _L and L _G , then V _n =L _n /μ _n Br R _n = L _n / μ _n A _n R _G = L _G / μ ₀ A _n R _L = L _L / μ _{0 A} nSince the reversible magnetic permeability μ _n of the ferrite magnet 31 is almost equal to the vacuum magnetic permeability μ ₀ , Equation (11) is expressed as φ _G =A _n B _r /1+(1/L _n +1/L _L )L _G (12).

As the rotating gears 2a and 2b rotate, the magnetic path length L _G of the gap changes periodically, and the magnetic flux φ _G passing through the coil 33 changes.

At this time, the voltage V _G induced in the coil 33 is V _G = Ndφ _G /dt = NA _n B _r d/dt {1/1+(1/L _n +1/L _L )L _G }
...(13) However, N is the total number of turns of the coil 33.

In equation (13), the residual magnetic flux density B _r changes depending on the temperature, and 1/1 + (1/L _n + 1/L _L ) L _G represents the shape of the magnetic circuit, and the rotating gear 2a,
It changes depending on the rotation of 2b. The magnitude of the time change is proportional to the rotational speed _Nr .

Therefore, the magnitude _G converted into direct current is expressed as _G = A ₁ B _r N _r . However, A ₁ is a constant.

However, as shown in FIG. 4, the temperature change in the residual magnetic flux density B _r is almost constant, and is expressed as follows.

B _r =B _rp (1+βT) However, B _rp is the residual magnetic flux density at standard temperature,
β is the temperature coefficient of residual magnetic flux density (Fig. 6).

Therefore, if the voltage induced in the coil 33 at standard temperature is V _Gp , then the following is obtained: V _G =V _G0 (1+βT) (14).

By applying this principle, an embodiment shown in the circuit block diagram for detecting torque in FIG. 2 is constructed.

First, the outputs of the two pick-ups 3a and 3b are passed through a phase detector 21 to obtain an output proportional to the twist angle.
Obtain Vτ.

The output V _G of one of the pickups, for example 3a, is passed through a rectifier 22 to obtain a DC signal _G.

Also, F/V (frequency → voltage) with monostable 23
By converting it, we can obtain a DC signal _G0 that is not affected by temperature.

The voltage _G is divided by the voltage _G0 in the divider 24 to calculate (1+βT).

This (1+βT) and the correction voltage V _R (=β/α−1) are added in the adder 26 to obtain β/α(1+αT), and if the gain of addition is α/β, then (1+αT) is obtained.

{(1+βT)+(β/α−1)}α/β=1+αT This (1+αT) and the output V of the phase detector 21
(=1/1+αTV〓 ₀ ) by the multiplier circuit 28 to derive a torque signal V〓 ₀ with no temperature error.

For example, in this embodiment, the temperature constant of elasticity of the elastic body 1 is α-0.035%/°C, and the temperature constant of the residual magnetic flux density B _r of the ferrite magnet 31 is β-0.2%/°C.

In addition, although the temperature-sensitive magnetic material (ferrite) is not directly attached to the elastic body 1, it can be placed near the elastic body to sufficiently maintain the temperature of the elastic body 1 by stirring the air due to the rotation of the elastic body 1. can be expressed.

FIG. 7 is an explanatory diagram of the structure of a pickup in another embodiment of the present invention.

Instead of the rotating gear, ferrite magnets 31 are embedded at equal intervals on the circumference of the rotating disk 71, and the pick-up 3a' is connected to the yoke 32 and the coil 33.
is formed. The signal processing circuit is the same as that shown in FIG.

FIG. 8 is a block diagram showing the configuration of a temperature correction circuit according to another embodiment of the present invention.

This is another method of detecting the temperature by calculating and determining the temperature change in the electromotive force, that is, the change in the magnetic properties of the ferrite magnet 31 that causes the change (residual magnetic flux density B _r in equation (13)).

Integrator 201 is used in place of the two speed detection circuits (rectifier 22 and monostable 23) in FIG.

The V _G induced in the coil 33 is derived from equation (13), and by integrating this, ∫V _G dt=NA _n B _r 1/1 + (1/L _n +1/L _L )L _G ... (15) is obtained.

This is connected to the rectifier or peak value follower 20.
2, a signal Vφ proportional to the residual magnetic flux density B _r that is not related to speed is obtained.

Vφ=K ₂ B _r [=K ₂ B _r0 (1+βT)] ...(16) This is added to the correction signal V _R in the adder 26, amplified and adjusted, and the multiplier circuit (gain control) 28
and the other uncorrected torque signal.
Temperature-compensated torque output signal multiplied by V〓
V〓 ₀ is derived.

By the way, the multiplier 28 that multiplies by (1 + αT) has a temperature change of 100°C width (±50°C), but the number to be multiplied is 1 + αT = 0.98 to 1.02, so it is a simple circuit that changes the amplification degree of the operational amplifier. You can get away with it.

Thus, according to the present invention, temperature information is calculated and derived from the torque detection signal (V _G ) without adding a new temperature sensor or wiring to the torque detector, and a correct temperature-corrected torque signal is generated. can be obtained. In other words, according to the present invention, it is only necessary to partially add a temperature correction circuit to the circuit for detecting torque and speed, and a highly accurate torque detection device can be realized without increasing costs or decreasing reliability.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the conventional device, Fig. 2 is a block diagram showing the configuration of an embodiment of the present invention, Fig. 3 is an explanatory diagram of the structure of the pickup, and Fig. 4 is the temperature characteristics of the barium ferrite magnet. (Magnetic field-
5 is a magnetic circuit diagram around the pickup, FIG. 6 is a temperature coefficient characteristic diagram of a barium ferrite magnet, and FIG. 7 is an explanatory diagram of the structure of a pickup in another embodiment of the present invention. 8
The figure is a block diagram showing the configuration of a temperature correction circuit in another embodiment of the present invention. 1... Elastic body (torsion bar), 2a, 2b
... Rotating gear, 3a, 3b, 3a' ... Magneto-electric converter (pickup), 4 ... Bearing, 5 ... Housing, 6 ... Temperature sensor, 7 ... Phase detection circuit, 8
... Temperature detection circuit, 9 ... Divider, 10 ... Torque signal without temperature correction, 11 ... Temperature signal, 12
...Temperature compensated torque signal, 20,200...
...Temperature correction circuit, 21... Phase detector, 22...
Rectifier, 23... Monostable, 24... Divider, 2
5... Correction signal input terminal, 26... Adder, 27...
...Speed output terminal, 28...Multiplication circuit, 29...
Torque output end, 31... Barium ferrite magnet, 32... Yoke, 33... Coil, 34
... Magnetic path, 71 ... Rotating disk, 201 ... Integrator, 202 ... Rectifier or peak value follower.

Claims (1)

[Scope of Claims] 1. An elastic body that transmits torque, and an elastic body that is provided close to the elastic body and spaced apart from each other in the direction of the rotation axis of the elastic body, that includes a temperature-sensitive magnetic body, and that is responsive to the rotation of the elastic body. Two magnetoelectric transducers each forming a magnetic circuit in which magnetic resistance changes and transmitting an electric signal according to the change in magnetic resistance; and a phase detector that detects an output phase difference between the two magnetoelectric transducers. a temperature correction circuit that calculates and derives a temperature correction signal related to the temperature of the elastic body from the output of the magnetoelectric converter; and a multiplication circuit that multiplies the output signal of the phase detector by the temperature correction signal, A torque detection device characterized in that the torque is detected based on a circuit output.