Torque detector

A torque detector for detecting a torque applied to a load from a driving shaft is disclosed. The torque detector comprises an elastic member which is interposed between a first shaft connected to the driving shaft and a second shaft connected to the load so as to be connected thereto, an angular phase difference detecting means for detecting an angular phase difference occurring between the first shaft and the second shaft when the torque is transmitted from the first shaft to the second shaft through the elastic member, and a data processing means for calculating the torque from the detected angular phase difference.

BACKGROUND OF THE INVENTION 
The present invention relates to a torque detector, particularly to a 
torque detector for detecting a torque applied to a torque transmission 
shaft which is connected to a load such as a wheel of an automobile. 
The conventional torque detector of this type is provided with a detector 
shaft of which one end is connected to a driving shaft of an engine and 
the other end is connected to the torque transmission shaft. In this 
torque detector, the torque applied to the torque transmission shaft is 
detected by detecting the distortion occurring in the above detector 
shaft. 
The distortion of the above shaft is detected by a detecting means of a 
strain gauge type comprising a strain gauge in which electric resistance 
varies in proportion to the distortion, of a magnetic strain type 
comprising a magnetic strain pipe in which magnetic property varies in 
accordance with the distortion or of a phase difference type, which 
detects a phase difference between the distortion occurring at two 
separated points of the detector shaft. 
However, the conventional torque detector having the above structure is 
large in size and complex in structure. Namely, in the conventional torque 
detector, the torque is detected by detecting distortion occurring in the 
detector shaft so that if the detector shaft is short, the accuracy of the 
detection is low. Therefore, in order to improve the accuracy of the 
detection, the detector shaft must be made long. 
It has been required to control the ignition timing, the air-fuel ratio and 
the gear ratio of the transmission of the automobile in accordance with 
the torque applied to the load. 
However, the above described conventional torque detector is too large and 
too complex in structure to be mounted on the automobile practically. 
Accordingly, one object of the present invention is to provide a torque 
detector which is small in size and simple in structure enough to be 
mounted on an automobile. 
Another object of the present invention is to provide a torque detector 
which detects torque with excellent accuracy. 
SUMMARY OF THE INVENTION 
The torque detector of the present invention comprises an elastic member 
which is interposed between a first shaft connected to a driving shaft and 
a second shaft connected to a load so as to be connected thereto, an 
angular phase difference detecting means for detecting an angular phase 
difference occurring between the first shaft and the second shaft when the 
torque is transmitted from the first shaft to the second shaft through the 
elastic member, and a data processing means for calculating the torque 
from the detected angular phase difference. 
According to the torque detector of the present invention, a long detector 
shaft for detecting the distortion thereof need not be interposed between 
the first shaft and the second shaft so that the structure thereof can be 
made simple. Therefore, the torque detector of the present invention can 
be mounted on an automobile as a means for controlling an air-fuel ratio, 
ignition timing and gear ratio of the transmission thereof.

DETAILED DESCRIPTION OF EMBODIMENTS 
Hereinafter, the present invention will be explained in accordance with 
several embodiments thereof with reference to the accompanying drawings. 
FIGS. 1 to 3 illustrate a first embodiment of the torque detector according 
to the present invention. 
Shafts 1, 2 are coaxially arranged within a casing 8 so as to be opposed to 
each other and they are rotatably supported thereby. 
One end of the shaft 1 is connected to a power source outside of the casing 
8 while one end of the shaft 2 is connected to a load outside of the 
casing 8. 
A thick walled flange 2a is formed in the other end of the shaft 2 so as to 
be opposed to the other end of the shaft 1. In the flange 2a, four long 
holes 2b extending in the circumferential direction are formed at equal 
angular distances. 
Spring receiving members 3a, 3b having a semicircular cross section as 
shown in FIG. 4 and an axial length larger than the thickness of the 
flange 2a, are closely inserted into both ends of each of the long holes 
2b so as to project on both sides of the flange 2a. 
A coil spring 4 is arranged within each of the long holes 2b and both ends 
thereof are supported by a flat surface of each of the spring receiving 
members 3a, 3b. The curved surface of each of the receiving members 3a, 3b 
slidably contacts with the wall defining each of the end portions of the 
long hole 2b. 
In the other end of the shaft 1, a flange 1a is formed so as to be opposed 
to the flange 2a of the shaft 2. And grooves 1b are formed in the flange 
1a so as to be opposed to the long holes 2b formed in the flange 2a. 
A coupling flange 5 is fixed to the outer periphery of the flange 1a by 
means of rivets so as to cover the flange 2a. 
In a covering member such as flange 5, a wall portion 5c is provided in 
which grooves 5a are formed so as to be opposed to the grooves 1b of the 
flange 1a through the long holes 2b. 
Both end portions of each of the receiving members 3a, 3b, which project on 
both sides of the flange 2a, are inserted into the grooves 5a, 1b. 
To the outer periphery of the shafts 1, 2, annular plates 6, 7 are fixed, 
respectively. In the outer peripheral surface of each of the annular 
plates 6, 7, a plurality of teeth 6a, 7a are formed at equal angular 
distances. 
Electromagnetic pickups 9a, 9b are provided in the casing 8 so as to be 
opposed to the teeth 6a, 7a, respectively. The pickups 9a, 9b detect the 
passing of the teeth 6a, 7a and generate electrical signals. The generated 
electrical signals are supplied to an pulse phase difference detecting 
circuit (described hereinafter) by way of lead wires 10a, 10b. 
In operation, when the shaft 1 is rotated in the direction of the arrow in 
FIGS. 1 to 3, the coupling flange 5 also rotates with the shaft 1. 
One end surface 1c of each of the grooves 1b formed in the flange 1a of the 
shaft 1 and one end surface 5b of each of the grooves 5a formed in the 
coupling flange 5 push the receiving members 3a as shown in FIG. 3. This 
pushing force is transmitted to the receiving members 3b through the coil 
springs 4. The receiving members 3b push the flange 2a of the shaft 2 to 
rotate the shaft 2 in the same direction as the rotating direction of the 
shaft 1. 
When the load of the shaft 2 is small, the deforming amount of each spring 
14 is small and as the load of the shaft 2 increases, the deforming amount 
of each spring 4 increases in proportion thereto. 
Due to this deformation of the coil springs 4, a phase difference occurs 
between the shaft 1 and the shaft 2. This phase difference varies in 
proportion to the amount of deformation of the spring 4, that is, in turn, 
proportional to the torque applied to the load side. 
This phase difference is detected by the electromagnetic pickups 9a, 9b 
which are opposed to the teeth 6a, 7a formed in the annular members 6, 7. 
FIG. 5 is a wave form diagram of output signals detected by the pickups 9a, 
9b. 
FIG. 5(1) shows a pulse wave form of the output signal detected by the 
pickup 9a and FIG. 5(2) shows a pulse wave form of the output signal 
detected by the pickup 9b. 
FIG. 6 is a block diagram of the angular phase difference detecting means 
and the data processing means of the present invention. 
A rotating speed counting circuit 11 is electrically connected to the 
electromagnetic pickup 9a and a phase difference detecting circuit 12 is 
electrically connected to the electromagnetic pickups 9a l and 9b. 
The rotating speed counting circuit 11 and the phase difference detecting 
circuit 12 are electrically connected to a microcomputer 13 as the data 
processing circuit, respectively. And the data processing circuit 13 is 
electrically connected to an indicating circuit 14. 
In operation, the output signal 91a detected by the pickup 9a is fed to the 
rotating speed counting circuit 11 while the output signals 91a, 91b 
detected by the pickups 9a, 9b are fed to the phase difference detecting 
circuit 12. 
The rotating speed counting circuit 11 feeds digital data T1 which is 
proportional to the period of the PG,10 output signal 91a and is inversely 
proportional to the rotating speed N, to the data processing circuit 13. 
The phase difference circuit 12 feeds digital data P which is proportional 
to the phase difference between the output signals 91a, 91b, to the data 
processing circuit 13. 
The data processing circuit 13 calculates the torque from the digital data 
T.sub.1 and P and the obtained torque is indicated by the display circuit 
14. 
FIG. 7 is a circuit diagram of the rotating speed counting circuit 11. 
The reference numerals 11a, 11b designate counters, 11c, 11d, 11e designate 
shift registers and 11f designates a three-state buffer. 
The counter 11a comprises a clock terminal CL, a reset terminal R, a 
counter enable terminal EN, and output terminals Q.sub.2 to Q.sub.4. The 
output terminal Q.sub.4 is connected to the counter enable terminal EN. 
To the clock terminal CL, a clock pulse signal C.sub.1 is applied and the 
counter 11a counts the clock pulse signal C.sub.1. When the output signal 
from the output terminals Q.sub.4 is "1" level, the "1" level signal is 
fed to the counter enable terminal EN to stop the counting operation of 
the counter 11a. 
When the signal 91a shown in FIG. 8(1) is fed to the reset terminal R, the 
counter 11a is reset so that the output signal from the output terminal 
Q.sub.4 is changed into "0" level as shown in FIG. 8(5). 
When the signal 91a is changed into "0" level, the counter 11a starts the 
counting operation to generate the pulse signals shown in FIGS. 8(3), 8(4) 
from the output terminals Q.sub.2, Q.sub.3 in order. 
When the output signal from the output terminal Q.sub.4 is turned into "1" 
level, the counter 11a stops the counting operation, again. 
The counter 11b comprises a clock terminal CL, a reset terminal R and 
output terminals Q.sub.1 to Q.sub.12 which are electrically connected to 
input terminals D.sub.1 to D.sub.4 of each of shift registers 11c, 11d, 
11e, respectively. 
The output signal from the output terminal Q.sub.4 of the counter 11a and 
the signal 91a are fed to a NOR gate 11g and the NOR gate 11g feeds a 
pulse signal shown in FIG. 8(6) to a NOR gate 11h. 
The clock pulse signal C.sub.1 shown in FIG. 8(2) is also fed to the NOR 
gate 11h. The NOR gate 11h feeds a pulse signal shown in FIG. 8(7) to the 
clock terminal CL of the counter 11b. 
The output signal from the output terminal Q.sub.3 of the counter 11a is 
fed to the reset terminal R of the counter 11b. 
The output signal from the output terminal Q.sub.2 of the counter 11a is 
fed to a clock terminal CL of each of the shift registers 11c, 11d, 11e. 
The counter 11b stops the counting operation at the time t.sub.1 when the 
signal 91a shown in FIG. 8(1) is changed into "0" level and the output 
signal from the NOR gate 11g shown in FIG. 8(6) is changed into "1" level. 
Thereafter, the output signal from the output terminals Q.sub.1 to Q.sub.12 
of the counter 11b are temporally memorized by the shift registers 11c to 
11e at the time t.sub.2 when the output signal from the output terminal 
Q.sub.2 of the counter 11a is changed into "1" level. 
Next, at the time t.sub.3 when the output signal from the output terminal 
Q.sub.3 of the counter 11a is changed into "1" level, the counter 11b is 
reset and at the time t.sub.4 when the output signal from the output 
terminal Q.sub.4 of the counter 11a is changed into "1" level, the counter 
11b starts the counting operation, again. 
The counter 11b continuously feeds output signals (counted data) to the 
shift registers 11c, 11d, 11e so as to synchronize with the output signal 
91a from the pickup 9a. Each of the shift registers 11c to 11e feeds 
digital data T.sub.1 which is proportional to the pulse period of the 
output signal 91a, namely the reciprocal of rotating speed (1/N) of the 
shaft 1, from the output terminals Q.sub.1 to Q.sub.4 to a three state 
buffer 11f. 
The control terminal 111f of the three state buffer 11f is connected to a 
NAND gate 11i. 
To the NAND gate 11i, an input and output control signal (hereinafter will 
be called I/O signal) and a device select signal (SEL 1) are applied from 
a device control unit (DCU) of the microcomputer 13. 
When the output signal of the NAND gate 11i is changed into "0" level, 
digital data T.sub.1 which is proportional to the reciprocal of rotating 
speed is fed from the output terminals 112f to the microcomputer 13. 
In this circuit, a well known quartz clock of about 524KH.sub.3 is used to 
feed a clock pulse signal. 
FIG. 9 is a circuit diagram of the phase difference detecting circuit 12. 
The reference numerals 12a, 12b, 12d, 12f designate counters, 12c 
designates a R-S flipflop, 12g, 12h, 12designate shift registers and 12j 
designates a three-state buffer. 
The signals 91a, 91b shown in FIGS. 10(1), (2) are fed to the reset 
terminals R of the counters 12a, 12b, respectively. The counters 12a, 12b 
feed pulse signals shown in FIGS. 10(3) 10(4) from the output terminals 
Q.sub.1 thereof to the S terminal and the R terminal of the R-S flipflop 
12c, respectively. 
The R-S flipflop 12c feeds a pulse signal shown in FIG. 10(5), of which "1" 
level is kept for a time t corresponding to the phase difference between 
the signals 91a, 91b, from the output terminal Q to the NAND gate 12e. 
While the pulse signal from the R-S flipflop 12c is "1" level, the NAND 
gate opens to feed a clock pulse signal C.sub.1 shown in FIG. 10(6) to the 
clock terminal CL of the counter 12f. 
Next, the shift registers 12g to 12i, the three-state buffer 12j and a NAND 
gate 12k operate in the same manner as explained on the operation of the 
rotating speed counting circuit 11 to feed digital data P which is 
proportional to the time t corresponding to the phase difference between 
the output signals 91a, 91b, to the microcomputer 13. 
The microcomputer 13 memorizes the digital data T.sub.1 which is applied 
from the rotating speed counting circuit 11 and the digital data P which 
is applied from the phase difference detecting circuit 12 in an inside 
memory (RAM) every period determined by the program thereof. Then, the 
microcomputer 13 calculates the torque from the memorized data. 
The microcomputer 13 need not operate so as to be synchronous with the 
rotating speed counting circuit 11 and the phase difference detecting 
circuit 12 since each of the circuits 11, 12 is provided with a latch 
circuit. 
In order to improve the accuracy, the microcomputer 13 should be operated 
so as to receive input signals when the circuits 11, 12 receive input 
signals. 
According to the present invention, any device can be used as a display 
circuit 14. For example, 7 segment LED is used as a digital display 
circuit and D/A converter is used as an analogue display circuit. 
In operation, when the load torque is applied, the spring 4 is compressed 
in accordance therewith so that the phase of the signal 91b delays from 
that of the signal 91a. 
The shaft torque T is expressed by the following equation: 
EQU T=K.sub.1 .multidot.N.multidot.P=K.sub.2 (1/T.sub.1).multidot.P 
wherein K.sub.1, K.sub.2 are constant, N is a rotating speed, P is a 
digital data fed from the phase difference detecting circuit 12 and 
T.sub.1 is digital data fed from the rotating speed counting circuit 11. 
The value N.multidot.P is proportional to the angular phase difference of 
the shafts 1, 2. 
From the above equation, the shaft torque T can be calculated from the data 
T.sub.1 and P by the microcomputer 13. The calculated value of the shaft 
torque T is indicated by the display circuit 14. 
FIG. 11 illustrates a second embodiment of the torque detector according to 
the present invention. In the second embodiment, two springs 4 are 
arranged in the axial direction of the driven shaft 1 and the torque 
transmission shaft 2 within each of the long holes 2b. The other structure 
of the second embodiment is substantially equal to that of the first 
embodiment. 
The torque detector of the second embodiment is suitable to a detector 
which is used for detecting a large torque. 
FIGS. 12 and 13 illustrate a third embodiment of the torque detector 
according to the present invention. 
In the end surface of the shaft 1, which is opposed to that of the shaft 2, 
inner teeth 20 are formed and in the end surface of the shaft 2, outer 
teeth 21 are formed so as to mesh with the inner teeth 20 at a 
predetermined distance. 
The other structure of the third embodiment is substantially equal to that 
of the first embodiment. 
In operation, when the applied torque becomes remarkably large at an engine 
starting time or engine stopping time, the inner teeth 20 and the outer 
teeth 21 strike against each other to stop the spring 4 from being 
compressed further. 
Therefore, the spring 4 is prevented from being excessively compressed so 
that the spring constant of the spring 4 does not change and damage to the 
spring 4 is prevented. As a result, the torque detecting accuracy will 
always be high. 
FIGS. 14 and 15 illustrate a fourth embodiment of the torque detector 
according to the present invention. 
In the fourth embodiment, from the spring receiving members 3a, 3b project 
projecting portions 3c, 3d so as to be opposed to each other at a 
predetermined distance. 
In operation, when the compressing value of the spring 4 reaches a 
predetermined maximum value, the opposed ends of the projecting portions 
3c, 3d abut on each other to prevent the spring 4 from being compressed 
further. 
In the preceding embodiments, coil springs are used to connect the driving 
shaft to the torque transmission shaft. Instead, rubber members, torsion 
springs or elastic resins can also be used. 
The angular phase of each of the shafts 1 and 2 can be detected 
electromagnetically or photoelectrically. For example, an oscillator or a 
semiconductor could be employed. 
FIGS. 16 to 18 illustrate a fifth embodiment of the torque detector 
according to the present invention. In the fifth embodiment, the torque 
detector is provided in the transmission of an internal combustion engine. 
A flywheel 23 is connected to an engine crank shaft 22 so as to rotate 
therewith. 
One end of an input shaft 25 of the transmission is connected to a hub 28 
of a clutch disc 31 by a spline while the other end thereof is supported 
by a supporting member (not shown) through a bearing (not shown). 
Within a clutch cover 29 which is connected to the flywheel 23, the clutch 
disc 31, a pressure plate 32, and a diaphragm spring 33 are provided. 
The rotating driving force of the flywheel 23 is transmitted to the shaft 
25 through the clutch disc 31 when the clutch disc 31 is pressed to the 
flywheel 23 due to the displacement of a release bearing (not shown) 
through the diaphragm spring 33 and the pressure plate 32. 
FIGS. 17 and 18 illustrate the structure of the clutch disc 31. The clutch 
disc 31 comprises the hub 28 connected to the shaft 25 by a spline, a disc 
plate 34 supported by the hub 28, torsion springs 4A interposed between 
the hub 28 and the disc plate 34, a sub plate 35 and a facing 36. 
The torsion springs 4A absorb the torque changes occurring during the 
rotation of the engine and also reduce the noise of the driving device. 
Coil springs or rubber members can be substituted for the torsion springs 
4A. 
In operation, when the clutch is connected, the torque is transmitted to 
the load side so that the torsion springs 4A are compressed in accordance 
with the load torque. The compressing value of the torsion springs 4A 
corresponds to the angular phase difference between the flywheel 23 and 
the shaft 25. 
In the outer peripheral surface of the flywheel 23, teeth 23a are formed at 
equal angular distances. To the outer peripheral surface of the shaft 25, 
an annular plate 37 provided with teeth 37a in the outer peripheral 
surface thereof at equal angular distances, is integrally fixed. 
Electromagnetic pickups 9a, 9b are provided in the housing 50 so as to be 
opposed to the teeth 23a, 37a, respectively. 
The pickups 9a, 9b detect the angular phase of the flywheel 23 and the 
shaft 25, respectively. Then the torque is calculated from the difference 
between the detected angular phases by the processing circuit shown in the 
first embodiment. 
FIG. 19 illustrates a sixth embodiment of the torque detector according to 
the present invention. The crank shaft 22 and the flywheel 23 are 
connected to or cut out from the input shaft 25 of the transmission (not 
shown) by means of the clutch means 24 having the same structure as that 
of the fifth embodiment. 
A shaft 26 is interposed between the crank shaft 22 and the input shaft 25 
and one end of the shaft 26 is fixed to the input shaft 25. 
An annular plate 6 is integrally fixed to the shaft 22 so as to be opposed 
to a flange 26a formed in the other end of the shaft 22. 
In the flange 26a, a plurality of long holes are formed and springs 4 are 
accomodated therein. The springs 4 are supported by receiving members (not 
shown) which are engaged with a subplate 27 covering the outer periphery 
of the flange 26a and fixed to the annular plate 6. 
In the outer periphery of the annular plate 6, teeth 6a are formed while in 
the outer periphery of the flywheel 23, teeth 23a are formed. 
Electromagnetic pickups 9a, 9b are provided so as to be opposed to the 
teeth 6a, 23a, respectively. 
In operation, when the shaft 22 is rotated, the rotation thereof is 
transmitted to the input shaft 25 through the annular plate 6, the 
flywheel 23, and the clutch means 24. 
The angular phase of the annular plate 6 and the flywheel 23 are detected 
by the pickups 9a, 9b, respectively. The torque is calculated from the 
difference between the detected angular phase by the processing circuit 
described in detail in the first embodiment. 
As described above, the torque detector of the present invention is 
characterized in that torque is detected by interposing an elastic member 
between a shaft on a driving side and a shaft on a load side, and by 
detecting the angular phase difference between both shafts due to the 
deformation of the elastic member which occurs when the rotating force on 
the shaft on the driving side is transmitted to the shaft on the load side 
through the elastic member. 
The torque detector of the present invention having the above described 
structure can be made remarkably small as compared with a conventional 
detector which provides a separate shaft mounted coaxially between the 
above two shafts and measures the distortion occurring in the separate 
shaft. 
Therefore, the torque detector of the present invention can be mounted on a 
vehicle. 
The detected torque can be used for controlling the ignition timing and the 
air-fuel ratio of an engine and the gear ratio of a transmission.