JPH0348738A - Torque sensor - Google Patents

Abstract

PURPOSE:To obtain both high density and strength by providing a generating mechanism for torsion corresponding to torque from an input shaft to an output shaft, a means which produces magnetic flux around a ferromagnetic material fixed to the mechanism, a magnetic flux variation detecting means, an amplifying means for its output and a phase adjusting means. CONSTITUTION:One end 3a of a torsion bar 3 penetrating the torque detection sleeve consisting of two sleeves 1 and 2, the other end 3b is fixed to the sleeve 2, and a lost motion mechanism 4 is provided between the sleeves 1 and 2. Then when torque is applied between the sleeves 2 (input shaft) and 1 (output shaft), an exciting current is induced in the ferromagnetic material fixed to the sleeve 2 to produce the magnetic flux, part of which becomes leak luminous flux through a groove formed in the ferromagnetic material and varies according to the torque between the input and output shaft. Pickup coils 44 and 46 detect the variation. Consequently, a signal is zero when no sensor torque is applied and the input and output shafts are coupled with each other after the sensor sensitivity is increased or the torsion mechanism rotates by a specific angle, thereby improving the strength to an overload.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a torque sensor that measures the torque of a rotating shaft.
In particular, the present invention relates to a torque sensor used in a power steering device for a vehicle.

(Prior Art) Conventionally, a power steering device for a vehicle has been provided with a hydraulic control valve and a hydraulic pump to assist the driver with the force required for steering. Such devices usually include a mechanism using steering force feedback means to provide a steering feel. Hydraulic power steering devices have the problem of requiring maintenance of the power steering oil. The oil pressure required to drive a hydraulic power steering system is typically provided by an engine driving a hydraulic pump. In a hydraulic power steering system, the hydraulic pump is driven by the engine even when the auxiliary torque is zero, so the loss of the hydraulic pump is relatively large. This is becoming increasingly important as engines become smaller and more efficient.

The present invention was made to replace a conventional hydraulic power steering device with an electric power steering device. However, electric power steering devices that must measure the input torque from the steering wheel require a high intensity to detect small inputs and strength to withstand large inputs on the order of 100r and Nbs. .

Various torque sensors have been known in the past.

However, none of these torque sensors are suitable for electric power steering devices. There are two ways to measure torque: indirect measurement as a function of the driving force of the rotating shaft and the rotational speed of the rotating shaft, or measuring the actual deformation of the rotating shaft or, less practically, by measuring it statically. There is a method of measuring the reaction torque (moment) indirectly from the rotating shaft by measuring the reaction torque (moment) applied to the reference plane.

Up until now, indirect torque measurement methods have rarely been used for large machines that operate with relatively large torques or small machines that operate with relatively small torques, and direct torque measurement methods have often been used. . Similarly, in other non-mechanical fields, direct methods were preferred when measuring torque. For this reason, there has been a need for a method and means for directly measuring the deformation of the rotating shaft.

As described above, conventional methods for measuring the torsion of a rotating shaft are roughly divided into two types: contact type and non-contact type.

When measuring torque using a contact method, it is common to attach a strain gauge to a deformable member, for example. Strain gauges are reliable, convenient, and economical sensors. However, strain gauges work best when attached to a stationary member. Therefore, when a strain gauge is mounted on a rotating shaft, it is necessary to connect a conductive wire connected to the strain gauge to a detector via a slip ring.

Slip rings are themselves a source of electrical noise,
Installation is location sensitive and relatively expensive. In a torque sensor with a strain gauge attached to the rotating shaft, the output signal of the strain gauge can be transmitted to a remote location by using a slip ring that generates electrical noise and two conductors that are inductively coupled to each other. It will be transmitted to some electronic circuit.

To date, various torque sensors using rotational transducers such as slip rings and strain gauges have been commercialized at fairly high prices. However, such a torque sensor has a complicated structure and is expensive, so it is rarely used except for research or prototyping.

Such a contact-type torque sensor is not suitable for a power steering device of a vehicle. Generally, a steering wheel is manufactured so that it can only rotate left and right by a predetermined rotation angle. Therefore, when using a contact-type torque sensor, it is preferable to directly connect the strain gauge mounted on the rotating shaft to the electronic circuit located at a remote location using a conductive wire without using a slip ring. However, when the strain gauge and the electronic circuit are directly connected by a conductive wire, this conductive wire winds around the steering shaft or loosens, causing a problem that the conductive wire deteriorates over time. In other words, when considering vehicle safety and reliability,
The contact type torque sensor is not passed through the torque sensor of the vehicle power steering device.

Non-contact torque measurements typically involve measurements of magnetic properties. It is well known that when torque is applied to various metals, the magnetic properties of that metal change. In particular, the magnetic permeability of a ferromagnetic member tends to increase with tension, and conversely shows a decrease with compression. As a torque sensor utilizing this effect, for example, US Pat. No. 4,441,85
There is something proposed in Specification No. 5. U.S. Patent No. 4,4
No. 41.855 discloses a torque sensor that detects changes in magnetic permeability of a magnetic layer formed on the surface of a non-magnetic rotating shaft using at least one big amplifier coil disposed adjacent to the rotating shaft. Disclosed. The inductance of the pickup coil is proportional to the change in permeability of the magnetic layer. Since the magnetic permeability of the magnetic layer is proportional to the torque applied to the rotating shaft, the inductance of the pickup coil is
It is proportional to the torque applied to the magnetic layer. Therefore, the torque applied to the rotating shaft on which the magnetic layer is formed can be determined by detecting the inductance of the big amplifier coil.

However, the magnetic properties of the magnetic layer depend not only on the torque applied to the rotating shaft but also on the temperature of the rotating shaft. Further, even if the rotating shaft is made of the same material as the magnetic layer, there are still many problems.

(Problems to be Solved by the Invention) Generally, an electromagnetic torque sensor that detects changes in magnetic resistance or leakage magnetic flux measures distortion or deformation caused by application of torque. If these deformations for a given torque are relatively large, the torque sensor will be relatively sensitive. However, conventional high-sensitivity torque sensors cannot withstand large torques without reducing reliability. Resistance to large input torques applied by the steering wheel results in a torque sensor with poor elasticity and low sensitivity. The main problem with conventional non-contact torque sensors, such as leakage flux type torque sensors and variable magnetic resistance type torque sensors, is that they lack both the high sensitivity and strength required when applied to vehicle power steering systems, etc. That's something I don't have.

A typical maximum value of torque applied to the steering wheel is on the order of 70 inches, -1 bs when the power steering system produces maximum assist torque. however,
Current vehicle design standards require at least 100 i
It is required to withstand a torque of n, -1 bs.

Therefore, the technical object of the present invention is to construct a torque sensor that has both high sensitivity and strength and is applicable to power steering devices for vehicles and the like.

[Structure of the invention]

(Means for solving the problem) The technical means taken to achieve the above-mentioned problem consists of a human-powered shaft, an output shaft, and a system in which the input shaft rotates a predetermined amount before the input shaft is coupled to the output shaft. a ferromagnetic member fixed to the input shaft and having at least a pair of grooves in the longitudinal direction of the input shaft; a partial coil that forms an induced excitation current in the ferromagnetic member, thereby generating leakage magnetic flux in the groove; and a leakage magnetic flux generated in the groove when torque is applied to the ferromagnetic member. The present invention includes a pickup coil for detecting a change in the pickup coil, and adjustment amplification means for amplifying the output induced current of the pickup coil and adjusting its phase.

(Function) When torque is applied between the human power shaft and the output shaft, the ferromagnetic member fixed to the input shaft is displaced. At this time, at least a pair of grooves formed in the longitudinal direction of the ferromagnetic member are displaced depending on the magnitude of the torque.

On the other hand, an induced excitation current is induced in the ferromagnetic member by the action of the negative coil. At the same time, magnetic flux is generated by an induced excitation current flowing through the ferromagnetic member. A part of this magnetic flux becomes leakage magnetic flux in at least one groove.

At least one pair of grooves formed in the ferromagnetic member displaces depending on the magnitude of torque, so the amount of leakage magnetic flux generated in the grooves varies depending on the magnitude of torque applied between the input shaft and the output shaft. This will change. Changes in the amount of leakage magnetic flux are detected by two differentially connected pickup coils. The signal detected by the pickup coil has its phase adjusted by an adjustment amplification means, and after being further amplified, it is converted into a signal corresponding to torque.
is output.

According to the above-mentioned technical means, the leakage flux generated by at least one pair of grooves is detected by two differentially connected pickup coils. Therefore, the output signal is reliably zero when no torque is applied to the torque sensor. Therefore, the gain of the adjustment amplification means can be set high to increase the sensitivity of the torque sensor.

Furthermore, according to the aforementioned technical means, the operating range of the torsion mechanism is limited to a predetermined rotation angle, and the input shaft is coupled to the output shaft after the torsion mechanism has rotated by the predetermined rotation angle. Therefore, sufficient strength against overload can be provided.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

As schematically shown in FIG. 1, a ferromagnetic member 10 having discontinuities, cracks, or scratches 16 formed on its surface is disposed within the axis of a solenoid coil 12 that supplies excitation current. , eddy currents as shown by arrows 14 are generated within the ferromagnetic member 10.

When such a discontinuity is formed in the outer skin layer of a ferromagnetic material, the leakage flux at the discontinuity, indicated by leakage flux 18, is greater than the induced flux indicated by arrow 20 at the continuous surface portion ( This is because the magnetic permeability at the discontinuous portion is greater than the magnetic permeability at the surface portion of the ferromagnetic material. This is because it is orders of magnitude smaller than the magnetic flux.The magnitude of the leakage magnetic flux 18 excited in the coil at the same frequency as the excitation current frequency depends on the size, number, and depth of the discontinuities provided on the surface. is proportional to.

The structure of a torque sensor to which the present invention is applied will be explained with reference to FIG. In this example, the torque detection sleeve is formed from two sleeves I and 2. Torsion bar 3
passes through the sleeve. One end 3a of the torsion bar 3 is firmly fixed to the sleeve l so as to rotate together with the sleeve l. Also, the other end 3 of the torsion bar 3
b is firmly fixed to the sleeve 2 so as to rotate together with the sleeve 2.

A thrust motion mechanism 4 having a spline structure is provided between the sleeve 1 and the sleeve 2.

FIG. 3 shows a sectional view taken along the line AA in FIG. 2. The cost motion mechanism 4 includes a spline or a plurality of circumferential protrusions 2a provided on the sleeve l, and a recess 1a in which the protrusions 2a engage. The protrusion 2a is provided on the sleeve l. As shown in FIG. 2, the protrusion 2a has a gap with the side wall of the recess 1a. therefore,
Before the torque is transmitted between the sleeves l and 2 via the cost motion mechanism 4, the sleeve l can rotate through seven degrees of 'ζ±7ζ phase relative to the sleeve 2. Therefore, when the normal input torque is ±70 bond inches, that is, when the auxiliary torque is at its maximum, sleeves 1 and 2 rotate relative to each other by ±7 degrees. If the input torque is higher than 1, the cost motion mechanism 4 prevents relative rotation of the sleeves 1 and 2 and transmits the torque directly between the sleeves 1 and 2. Therefore, the torque sensor can withstand excessive torque loads.

Sleeve l has a stainless steel sleeve 5 attached to the bottle 6.
Fixed by The sleeve 2 is inserted into the sleeve 5. There is a detection sleeve on the outer circumferential side of the sleeve 5? a and 7b are fixed. The detection sleeves 7a and 7b rotate together with the sleeve 5, that is, with the sleeve 1.

Detection sleeve 7a, ? Another detection sleeve 9 is fixed between the portions b. The detection sleeve 9 is fixed to the sleeve 2 by a pin 8. Therefore,
The detection sleeve 9 rotates together with the sleeve 2.

This will be explained with reference to FIG. 4a. FIG. 4a is a second diagram depicting the relationship between the detection sleeves 7a and ffb and the detection sleeve 9.
It is an enlarged view of the main part of the figure. Between the detection sleeve 7a and the detection sleeve 9, there are many magnetic resistance parts 71, 73 and protrusions 1.
2.14 is formed. (Similarly, there are many magnetic resistance parts 7 between the detection sleeve 7b and the detection sleeve 9.
5.77 and a protrusion 76.7B are formed.

As shown in FIG. 4b, the magnetoresistive portions 73 and 75 are formed at positions opposite to each other. In addition, the magnetic resistance section 71
is formed at a position shifted from the magnetic resistance portion 73 by a predetermined distance α in the positive direction (in the direction shown in the figure) when no torque is applied to the torque sensor. Further, the magnetic resistance section 77 is formed at a position shifted in the negative direction (upward in the drawing) from the magnetic resistance section 75 by a predetermined distance α when no torque is applied to the lux sensor.

In the device of this embodiment, the above-mentioned interval α is set so that the amount of leakage magnetic flux generated in the state where no torque is applied to (Luxe) is equal.Such an interval α is set. Then, the influence of external factors such as temperature drift is canceled out, and a stable torque sensor can be constructed.

The explanation will be given again with reference to FIG. 4a. Magnetoresistive part'rl,
Pick-up coils 44 and 46 that are differentially connected to the negative coil 42 are arranged directly above the coil 72 . The pickup coils 44 and 46 are magnetic resistance parts 71 made of ferromagnetic material.
．． Changes in leakage magnetic flux due to changes in distance occurring in the vicinity of 72 are detected.

The leakage magnetic flux generated between the detection sleeves 7a and 9 will be explained below with reference to FIGS. 5a and 5b.

Torque sensor with no torque applied is 50%
It is in a combined state. Protrusions 76 and 7 are tightened by manual torque.
The distance between the detection sleeves Tb and 9 becomes shorter or longer, thereby reducing or increasing the leakage magnetic flux caused by the gap between the detection sleeves Tb and 9. As the distance between protrusions 76 and 78 increases, as shown in Figure 6a, the leakage flux increases, as shown in Figure 6b. Although not shown, when the distance between the protrusions 76 and 78 becomes longer, the protrusions 72
The distance between and 74 is shorter. Therefore, approximately twice the output can be obtained from the two differentially connected pickup coils 4146.

FIG. 7 shows a circuit configuration for detecting the amount of leakage magnetic flux generated between the detection sleeves 7a and 9 and between the detection sleeves 7h and 9. It should be noted that other conventional circuits may be used to derive the phase and amplitude of the signals output from the differentially connected pickup coils 44,46. In the example shown in FIG.
0 is partially connected to the coil 42 and the detection sleeve 7a1
An excitation current for inducing magnetic flux is supplied to 7b and 9. The pickup coils 44 and 46 are connected to a four-circuit changeover switch 52. The zero point detection circuit 54 consists of an operational amplifier 56 and an inverter 58, and the sine wave oscillation circuit 5
0 is connected to the four-circuit changeover switch 52. The operational amplifier 56 operates as a comparator, and OV is the reference value. The output of the four-circuit changeover switch 52 is filtered by an integrator circuit 60. A second operational amplifier 62 amplifies the output of the integrating circuit 60.

The operation will be explained based on the structure of the bed. Zero point detection circuit 54
outputs a square wave of positive polarity at the output terminal 567 while the polarity of the input sine wave is positive, while the output terminal 582 of the inharter 58 outputs a square wave of positive polarity while the polarity of the input sine wave is negative. Output waves. The positive pulse at the output 7 turns on switches B and C connected to the pick-up coil 44,46, supplying an output current to the integrating circuit 6G. Output end 582
The positive pulse generated in pickup coil 44.
Switches 0 and A connected to 46 are turned on to supply an output current to the integrating circuit 60.

FIG. 8 shows typical output characteristics of the device of this embodiment. 8th
As shown in the figure, this torque sensor can detect torque in both directions with good linearity within a limited area.

[Effects of the Invention] According to the present invention, it is possible to construct a torque sensor that has high torque detection sensitivity and has sufficient strength even against excessive torque.

[Brief explanation of drawings]

FIG. 1 is a perspective view depicting leakage magnetic flux generated in a magnetic resistance section formed on the surface of a ferromagnetic material. FIG. 2 is a sectional view depicting a torque sensor to which the present invention is applied. FIG. 3 is a sectional view taken along the line AA in FIG. 2. FIG. 4a is an enlarged sectional view of the main part of FIG. 2. FIG. 4b is an enlarged view of the main part showing the displacement of the magnetic resistance part formed in the detection sleeve. Figure 15a is a partial side view of the torque sensor of the present invention depicting the detection sleeve in a state where no torque is applied. Figure 5b depicts the leakage magnetic flux from the detection sleeve.
It is a BB sectional view of figure a. FIG. 6a is a partial side view of the torque sensor of the present invention depicting the detection sleeve in a state where torque is applied. Figure 6b depicts the leakage magnetic flux from the detection sleeve.
It is a CC sectional view of figure a. FIG. 7 is a circuit diagram of the torque sensor of the present invention. FIG. 8 is a graph plotting the output signal of the torque sensor against torque. 1... Sleeve (output shaft), 2... Sleeve (input shaft), 3... Torsion bar (twisting mechanism), 4... Lost motion mechanism (twisting mechanism), 5... Sleeve,
6... Bottle, 7a, 7b... Detection sleeve, 8... Bottle, 9... Detection sleeve (ferromagnetic material member), 42...
-Next coil, 44.46...Pickup coil, 50...Sine wave oscillation circuit (adjustment amplification means), 52...Four circuit changeover switch (adjustment amplification means) 54...Zero point detection circuit (adjustment amplification means), 58...inverter (adjustment amplification means)
, 60... Integrating circuit (adjustment amplification means), 62... Second operational amplifier (adjustment amplification means) 71... Magnetoresistive part, 72... Protrusion, 73.75... Magnetoresistive part ( a pair of grooves), 74.76...Protrusion, 77...Magnetic resistance part, 78...Protrusion.

Claims (1)

[Claims] An input shaft; an output shaft; the input shaft can rotate by a predetermined rotation angle until the input shaft is coupled to the output shaft; a torsion mechanism that generates torsion; a ferromagnetic member fixed to the input shaft and having at least a pair of grooves in the longitudinal direction of the input shaft; and forming an induced excitation current in the ferromagnetic member, thereby a primary coil that generates leakage magnetic flux in the groove; a pickup coil that detects a change in leakage magnetic flux that occurs in the groove when torque is applied to the ferromagnetic member; and an output induced current of the pickup coil. and adjustment amplification means for amplifying and adjusting its phase.