GB2187848A

GB2187848A - Torque detecting device

Info

Publication number: GB2187848A
Application number: GB08705519A
Authority: GB
Inventors: Kiyoshi Nagae; Naoyuki Maeda
Original assignee: Tokai TRW and Co Ltd
Current assignee: Tokai TRW and Co Ltd
Priority date: 1986-03-12
Filing date: 1987-03-09
Publication date: 1987-09-16
Anticipated expiration: 2007-03-09
Also published as: DE3707831A1; GB8705519D0; GB2187848B

Abstract

A torque detecting device includes a rotatable torque detecting shaft 3 having an input end 3a and an output end 3b rotatable in response to the rotation of the input end, all provided in a housing 1. A sleeve 4 is pinned to the shaft input end 3a and carries an insulating member 10. Annular cores 16, 17 are provided respectively coupled for rotation with the input end and the output end of the shaft. A primary coil 8 for connection to an a.c. power source and a secondary coil 13 for signals output are provided on the housing, while a secondary coil 11 for the power source and a primary coil 12 for the signal output are provided on the input end of the shaft. The coils 8, 11 thus form a power input transformer while coils 12, 13 form a signal output transformer, eliminating moving contacts. The core 17 has projecting pole pieces while windings 19a-b on the core 16 are connected in a bridge circuit supplied by coil 11 and feeding an output to coil 12. The phase and magnitude of the bridge output indicate direction and degree of torque. In an alternative arrangement the coil 19 is divided into primary and secondary windings (119p, s Figs. 10-12 not shown). <IMAGE>

Description

SPECIFICATION Torque detecting device The present invention relates to a torque detecting device and more particularly to a torque detecting device interconnected to a steering mechanism in an automobile and adapted to detect the steering torque of the automobile.

In the torque detecting apparatuses according to prior arts which incorporated a detecting device for detecting steering torque, a torque detecting device of a strain gauge type is provided wherein a strain gauge is directly attached to the surface of the connecting rod of the steering wheel and the strain generated at the connecting rod when the steering operation is applied is electrically detected by a bridge circuit.

In detecting devices of this sort, however, since the strain gauge is attached to the surface of the connecting unsuitable for application to a powered steering device for an automobile.

Another example of a torque detecting device according to a prior art is a torque detecting device of an excitation type in which a torsion bar of a ferromagnetic material is provided in the connecting rod of a steering wheel, an exciting coil and a detecting coil are provided around the outer circumference of said torsion bar and the alternating current excitation and magnetic strains are detected, whereby the steering torque is detected by utilizing magnetic anisotropy. In this type of detecting device, since bending force in uncertain directions may be applied to the torsion bar at the time of a steering operation other than the pure steering torque component, the distance between the torsion bar and the exciting and detecting coils cannot be accurately maintained and it fluctuates.Accordingly it is difficult to maintain accuracy in the detecting of the steering torque with this type of detecting device.

In addition to the abdve-mentioned type apparatuses, there is another type of steering torque detecting apparatus in which a torsion portion adapted to have strain imparted to it in response to changes in torque is formed in the connecting shaft of a steering wheel and the amount of torsion caused at the time of a steering operation is detected by a photo-diode, a photo-transistor, a Hall IC or the like.

However, since such detecting elements provide detecting characteristics which may be variable due to secular variations, temperature variations, etc., and as they themselves deteriorate, they cannot be satisfactorily used as steering torque detecting devices for cars which are subjected to hostile conditions and which need to provide reliability over a long period of time.

In view of the drawbacks pointed out above, the present invention has it as an object to provide a torque detecting device which is electrically stable, has excellent detection accuracy, has a long serviceable life and weatherproof characteristics, and displays excellent characteristics in the face of secular variations, such a detecting device being particularly suitable as one adapted to detect the steering torque of the steering wheel in an automobile.

A further object of the present invention is to provide a torque detecting device wherein a rotatable torque detecting shaft having an input end and an output end rotatable in response to the rotation of the input end is provided in a housing, an electromagnetic detecting portion being subject to the relative rotational displacement between the input and output ends are provided respectively at the side of the input end and at the side of the output end, and a primary coil for the power source and a secondary coil for signals are provided on the housing while a secondary coil for the power source and a primary coil for signals are provided at the side of the input end of the torque detecting shaft, so that supply of reference signals to the detecting portion for detecting the relative rotational displacement and take-out of the signals relating to the rotational displacement from the detecting portion can be formed mechanically and in a non-contacting condition by applying the principle of a transformer.

Yet another object of the present invention is to provide a torque detecting device adapted to detect torque in response to relative rotational displacement between an input end and an output end of a torque detecting shaft which is rotatably provided in a housing, the output end being rotatable in response to the rotation of said input end, said torque detecting device comprising a first annular magnet core rotatable integrally with the inlet end of the torque detecting shaft; a second annular magnet core arranged coaxially and opposedly with respect to the first annular magnet core and rotatable integrally with the outlet end of the torque detecting shaft; four detecting coils wound around the first annular magnet core in a substantially and equidistantly spaced manner and adapted to form an alternating current bridge circuit for detecting the relative rotational displacement; an annular primary power source coil fixedly mounted around the inner circumference of the housing for inputting a reference power signal from an external alternating current power source; an annular secondary power source coil connected to the input terminals of the alternating current bridge circuit, arranged coaxially and opposedly with respect to the primary power source coil and rotatable integrally with the input end of the torque detecting shaft; an annular primary signal coil connected to the output terminals of the alternating current bridge circuit and rotatable integrally with the input end of the torque detecting shaft; and an annular secondary signal coil arranged coaxially and opposedly with respect to the primary signal coil and fixedly mounted around the inner circumference of the housing for outputting the signals representative of the relative rotational displacement.

A still further object of the present invention is to provide a torque detecting device adapted to detect torque in response to relative rotational displacement between an input end and an output end of a torque detecting shaft which is rotatably provided in a housing, the output end being rotatable in response to the rotation of the input end, torque detecting device comprising a first annular magnet core housing a plurality of magnetic pole pieces and rotatable integrally with the input end of the torque detecting shaft; a second annular magnet core arranged coaxially and opposedly with respect to the first annular magnet core and rotatable integrally with the output end of the torque detecting shaft; an annular primary power source coil fixedly mounted around the inner circumference of the housing for inputting a reference signal from an external alternating current power source; an annular secondary power source coil arranged coaxially and opposedly with respect to the primary power source coil and rotatable integrally with the input end of the torque detecting shaft; a primary detection coil connected to the secondary power source coil and continuously wound around the plurality of magnetic pole pieces of the first annular magnet core; a secondary detection coil wound continuously around the plurality of magnetic pole pieces for detecting the relative rotational displacement; an annular primary signal coil connected to the secondary detection coil and rotatable integrally with the input end of the torque detecting shaft; and an annular secondary signal coil arranged coaxially and opposedly with respect to the primary signal coil and fixedly mounted around the inner circumference of the housing for outputting the detection signals representative of the relative rotational displacement.

According to the present invention, since the torque detecting device in itself is incorporated in a housing by way of an extremely simple construction and supply of the reference signals to the torque detecting device and take-out of the detection signals from the device can be executed through a non-contacting structure by applying the principle of a transformer, the inventive torque detecting device is excellent in terms of durability, weather-proofness and secular variation characteristics, and is highly reliable.

Fig. 1 illustrates a typical form of construction of the first embodiment of the torque detecting device according to the present invention; Fig. 2 illustrates an embodiment of the torque detecting portion taken along the line 1-1 of Fig. 1; Fig. 3 illustrates an electric circuit diagram for the torque detecting device shown in Fig.

1 and Fig. 2; Fig. 4 shows signal wave forms relating to the operation of the electric circuit shown in Fig. 3; Fig. 5 shows the relationship between the torque and the magnetized conditions as generated at the torque detecting portion shown in Fig. 2; Fig. 6 shows the relationship between the output signals obtained by the torque detecting device according to the present invention and the direction of the torque; Fig. 7 illustrates another embodiment of the torque detecting portion taken along the line II in Fig. 1; Fig. 8 shows the relationship between the torque and magnetized conditions as generated at the torque detecting portion shown in Fig. 7; Fig. 9 shows an example in which the torque detecting device according to the present invention is applied to a steering gear;; Fig. 10 shows a typical form of construction of the second embodiment of the torque detecting device according to the present invention; Fig. 11 shows the torque detecting portion taken along the line Il II in Fig. 10; and Fig. 12 shows an electric circuit diagram for the torque detecting device shown in Fig. 10 and Fig. 11.

Fig. 1 shows a typical form of construction of the first embodiment of the torque detecting device according to the present invention which is partly drawn in section.

Inside an annular housing 1 is provided a torque detecting shaft 3 rotatable by way of a bearing 2. One end of the torque detecting shaft 3 functions as an input end 3a while the other end of the shaft functions as an output end 3b. Namely, the output end 3b is caused to rotate by virtue of the torsion of the torque detecting shaft 3 in response to the rotation of the input end 3a and the relative rotational displacement between the input and output ends makes it possible to detect the amount of torque.

A sleeve 4 is fitted on the torque detecting shaft 3. One end of the sleeve is rotatably mounted to the input end 3a by a pine 5 and thus rotates together with the shaft while the other end of the sleeve is supported by a bearing 6 such that it may relatively rotate in relation to the output end 3b.

Along the inner circumference of the housing is fixed an annular primary power source coil 8 through an insulating member 7. The coil 8 is connected to an external alternating current power source (numeral 20 in Fig. 3) through an input lead 9. On the other hand, an annular secondary power source coil 11 is arranged along the outer circumference of the sleeve 4 and is adapted to be rotatable together with the sleeve. The secondary coil 11 is arranged through an insulating member 10 coaxially and opposedly with respect to the primary power source coil 8. Furthermore, an annular primary signal coil 12 rotatable integrally with the sleeve 4 is provided in the insulating member 10. On the other hand, in the insulating member 7 at the side of the housing 1, an annular secondary signal coil 13 is fixedly mounted coaxially and opposedly with respect to the primary signal coil 12.The secondary signal coil 13 is connected to an appropriate external signal processing circuit (not shown) by way of an output lead 14 for detected signals.

The annular magnet core 16 on which a detecting coil 19 is wound and the annular magnet core 17 constitute a torque detecting portion. The magnet core 16 is supported by the insulating member 10 at the side of the sleeve 4 and is rotatable integrally with the input end 3a of the torque detecting shaft 3 while the magnet core 17 is rotatable integrally with the output end 3b and is arranged coaxially and opposedly with respect to the magnet core 16.

Fig. 2 is a sectional view taken along the line I-I in Fig. 1 and shows in great detail a typical form of construction of the torque detecting portion explained above. As illustrated, the annular magnet core 1 7 is constructed to be integral with the output end 3b of the torque detecting shaft 3 and will be explained with reference to its function. It has two cutout portions 18a, 1 8b which are disposed at substantially diametrically opposite positions with respect to the rotational axis. The annular magnet core 16 which is rotatable in relation to the magnet core 17 has wound four detecting coils 1 9a through 1 9d around it in equidistantly relationship with each other.Constructed in this way, the respective magnetic circuits formed between the magnet core 1 7 and the magnet core 16 with respect to the detecting coils 19a through 19d may be varied depending on the relative rotational displacement between the magnet cores. It is further to be noted that a variation, i.e., increase/decrease in the magnetic capacity of one pair of detecting coils 19a, 1 9b versus the other pair of coils 19c, 1 9d in correspondence with the relative rotational displacement of the magnet cores is inversely effected.

Fig. 3 illustrates an electric circuit diagram for the torque detecting device according to the present invention.

An A.C. power source 20 is connected across the primary power source coil 8 by way of the power source input leads 9 and the opposite ends of the associated secondary power source coil 11 are connected respectively to input terminals J1, J2 of the alternating current bridge circuit constituted by the four detecting coils 19a through 19d. Output terminals J3, J4 of the bridge circuit are connected respectively to the opposite ends of the primary signal coil 12. The opposite ends of the secondary signal coil 13 are connected respectively to output terminals OUT of the torque detecting device through the detection signal output leads 14. The primary power source coil 8 and the secondary power source coil 11 as well as the primary signal coil 12 and the secondary signal coil 13 supply or receive the power or signals in a non-contacting condition through mutual inductance.

When a reference alternating current wave signal (shown in Fig. 4(A)) is supplied to the primary power source coil 8 from the A.C.

power source 20, an alternating current wave signal in proportion to the mutual inductance between the primary and secondary coils 8, 11 is induced at the secondary power source coil 11 and then is provided to the alternating current bridge circuit.

If no torque is applied to the input end 3a of the torque detecting shaft 3, the magnetized conditions with respect to one pair of detecting coils 19a, 1 9b and the other pair of detecting coils 19c, 19d are exactly the same, as shown in Fig. 5(A). As a result, no signal is outputted from the alternating current bridge circuit through the detecting doils 1 9a through 19d.

Conversely if torque is applied to the input end 3a in one rotational direction, the magnetized conditions or the magnetic capacity with respect to one pair of detecting coils 19a, 1 9b and the other pair of detecting coils 19c, 19d are inversely effected as shown in Fig.

5(B) and the output wave shown in Fig. 4(B) is generated as a detection signal at the output terminals J3, J4 of the alternating current bridge circuit. This detected signal represents the relative rotational displacement between the input end 3a and the output end 3b of the torque detecting shaft 3.

Then if torque is applied to the input end 3a in the reverse direction, the magnetized condition with respect to the detecting coils 19a through 19d becomes as shown in Fig.5 (C) and accordingly at the output terminals J3, J4 of the alternating current bridge circuit an output wave representing phase reversal with respect to the output wave shown in Fig. 4(B) is generated as in the manner shown in Fig.

4(C).

It is noted that the amplitudes of the output waves from the alternating current bridge circuit (as shown in Fig. 4 as h1, h2) vary in response to the magnitude of the torque or the relative rotational displacement between the input end 3a and the output end 3b of the torque detecting shaft 3.

Thus, the output signal obtained from the alternating current bridge circuit is output from the output terminals OUT through the primary signal coil 12 and the secondary signal coil 13, as the detection signal of the torque detecting device. As may be readily understood by those skilled in the art, the detected signal may be phasedetected with reference to a signal wave form from the power source whereby the torque detection signal corresponding to the direction and magnitude of the torque at the input end 3a may be obtained as shown in Fig. 6.

Fig. 7 illustrates another embodiment of the torque detecting portion which is shown in section in a manner similar to Fig. 2 and taken along the line I-I shown in Fig. 1. Although the annular magnet core 17 fixedly mounted to the output end of the torque detecting shaft 3 is identical to the magnet core shown in Fig. 2, the magnet core 16 arranged coaxially and opposedly with respect to the magnet core 17 is divided into four magnet core portions 16a through 16d and the detecting coils 1 9a through 1 9d are respectively wound around the divided magnet core portions.

Fig. 8 illustrates the magnetized conditions of the magnet core construction shown in Fig.

7. In a manner similar to that of Fig. 5, Fig.

8(A) illustrates the condition in which no torque is applied to the input end 3a of the torque detecting shaft 3. Fig. 8(B) illustrates the condition in which torque is applied in one rotational direction on the input end 3a. Fig.

8(C) illustrates the condition in which torque is applied on the input end 3a in the reverse rotational direction.

The torque detecting device according to the present invention which has been described in detail is most suitable for a steering torque detecting device used in an automobile which has to face hostile conditions over long periods of time. In this application, the steering gear housing may be used as the housing, as shown in Fig. 9, and the input end of the torque detecting shaft 3 is interconnected with the steering wheel of an automobile while the output end is connected to the left and right wheels through a pinion gear 21 and a rack shaft 22 for steering operation. The torque detecting signal output from the torque detecting device may be supplied to an electric motor or power control apparatus for the hydraulic pressure system, which is adapted to drive the above-mentioned steering rack shaft 22, in order to control the direction and magnitude of steering assisting power.

Fig. 10 illustrates a typical form of construction of the second embodiment of the torque detecting device according to the present invention which is partially shown in section.

As is clear from a comparison between Fig.

1 and Fig. 10, the second embodiment is con structed in a similar way to the first embodi ment except for the torque detecting portion with respect to the output end 3b of the torque detecting shaft 3. In Fig. 10, those com ponents which are the same as those in Fig.

1 are designated by the same numerals. It is to be noted that numerals 8a and 13a respectively designates yoke iron cores on the stator side which numerals 1 1a and 12a respectively designate yoke iron cores on the rotor side.

Numeral 116' designates a yoke portion of the magnet core 116.

Fig. 11 is a sectional view taken along the line Il-Il in Fig. 10 and shows a typical form of construction of the torque detecting portion according to the second embodiment. As illustrated, an annular magnet core 117 formed integrally with the output end 3b of the torque detecting shaft 3 has two projecting portions 11 7a and 11 7b in diametrically opposed relationship with respect to the rotational axis. A magnet core 116 which is rotatable in relation to the magnet core 117 has four magnetic pole pieces 116a, 116b, 116c and 116d.A primary detection coil 11 9p which is to be connected to the secondary power source coil 11 is sequentially wound on the respective magnetic pole pieces of the magnet core 117 and a secondary detection coil 1 19s is also similarly wound sequentially on the respective magnetic pole pieces of the magnet core 117.

The secondary detection coil 119s is connected to the primary signal coil 12. Thus constructed, the magnetic flux distribution generated by the secondary power signal applied to the primary detection coil 11 9p can be varied in response to relative rotational displacement between the magnet core 116 and the magnet core 117, which variation causes the secondary detection signal to be induced in the secondary detection coil 1 19s and this induced signal is applied to the primary signal coil 12. Accordingly the torque can be detected as a function of the relative rotational displacement between the magnet core 116 and the magnet core 117.It is to be understood here that the arrows indicated in relation to the magnetic pole pieces 116a, 116b, 1 16c and 1 16d of the magnet core 116 designate the direction of the magnetic flux 4' at an optional time, which fluxes are provided by the energized primary detection coil 119p.

Fig. 12 illustrates an electric circuit diagram of the second embodiment of the torque detecting device according to the present invention.

The A.C. power source 20 is connected across the primary power source coil 8 through the current input leads 9. The opposite ends of the secondary power source coil 11 are connected to the primary detection coil 1 19p which is in turn wound sequentially on four magnetic pole pieces 1 16a through 1 16d of the magnet core 116. The secondary detection coil 119s which is similarly wound se quentially on the four magnetic pole pieces is connected across the primary signal coil 12. It is to be noted that the symbols a through d in Fig. 12 correspond to the symbols for the respective magnetic pole pieces of the magnet core 116 and the dots designate the direction of winding.The opposite ends of the secondary coil 13 are connected to the output terminals OUT of the torque detecting device through the output leads 14.

As will be clear from the foregoing explanation, supply and reception of power and signals is accomplished in a non-contacting condition by means of the mutual inductance between the primary power source coil 8 and the secondary power source coil 11, between the primary detection coil 1 19p and the secondary detection coil 119s, and between the primary signal coil 12 and the secondary signal coil 13.

Like with the operation of the first embodiment, when a reference A.C. signal (as shown in Fig. 4(A)) is applied from the A.C.power source 20 to the primary power source coil 8, the output signal shown in Fig. 4(B) or Fig.

4(C) is sequentially generated as a detection signal through the secondary coil power source 11, the primary signal coil 119p, and the secondary detection coil 119s and then through the primary signal coil 12 and the secondary signal coil 13. This detected signal represents the relative rotational displacement between the input end 3a and the output end 3b of the torque detecting shaft 3 and hence the torque at the input end 3a in one rotational direction.

Claims

1. A torque detecting device adapted to detect torque in response to relative rotational displacement between an input end and an output end of a torque detecting shaft which is rotatably provided in a housing, the output end being rotatable in response to the rotation of said input end, said torque detecting device comprising:: a first annular magnet core rotatable integrally with the inlet end of said torque detecting shaft, a second annular magnet core arranged coaxially and opposedly with respect to said first annular magnet core and rotatable integrally with the outlet end of said torque detecting shaft, four detecting coils wound around said first annular magnet core in a substantially and equidistantly spaced manner and adapted to form an alternating current bridge circuit for detecting said relative rotational displacement; an annular primary power source coil fixedly mounted around the inner circumference of said housing for inputting reference power signals from an external alternating current power source;; an annular secondary power source coil connected to the input terminals of said alternating current bridge circuit, arranged coaxially and opposedly with respect to said primary power source coil and rotatable integrally with the input end of said torque detecting shaft; an annular primary signal coil connected to the output terminals of said alternating current bridge circuit and rotatable integrally with the input end of said torque detecting shaft; and an annular secondary signal coil arranged coaxially and opposedly with respect to said primary signal coil and fixedly mounted around the inner circumference of said housing for outputting the signals representative of said relative rotational displacement.

2. A torque detecting device as claimed in Claim 1 wherein said second annular magnet core is provided with two cut-out portions disposed at approximately diametrically opposite positions so as to render variable the magnetic circuit formed thereby together with said first annular magnet core.

3. A torque detecting device as claimed in Claim 1 or 2 wherein said first annular magnet core is comprised of a single member.

4. A torque detecting device as claimed in claim 1 or 2 wherein said first annular magnet core comprises four magnet core portions and said four detecting coils are wound respectively around said four magnet core portions.

5. A torque detecting device adapted to detect torque in response to relative rotational displacement between an input end and an output end of a torque detecting shaft which is rotatably provided in a housing, the output end being rotatable in response to the rotation of said input end, said torque detecting device comprising:: a first annular magnet core housing a plurality of magnetic pole pieces and rotatable integrally with the input end of said torque detecting shaft; a second annular magnet core arranged coaxially and opposedly with respect to said first annular magnet core and rotatable integrally with the output end of said torque detecting shaft; an annular primary power source coil fixedly mounted around the inner circumference of said housing for inputting reference signals from an external alternating current power source; an annular secondary power source coil arranged coaxially and opposedly with respect to said primary power source coil and rotatable integrally with the input end of said torque detecting shaft; a primary detection coil connected to said secondary power source coil and continuously wound around said plurality of magnetic pole pieces of said first annular magnet core; ; a secondary detection coil wound continuously around said plurality of magnetic pole pieces for detecting the relative rotational displacement; an annular primary signal coil connected to said secondary detection coil and rotatable integrally with the input end of said torque detecting shaft; and an annular secondary signal coil arranged coaxially and opposedly with respect to said primary signal coil and fixedly mounted around the inner circumference of said housing for outputting the detection signals representative of said relative rotational displacement.

6. A torque detecting device substantially as hereinbefore described with reference to, and as illustrated in Figs. 1 to 6 or Figs. 7 to 12 of the accompanying drawings.