JPH0435799B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a torque detector for detecting torque transmitted from a driving side to a driven side.

There is a need to accurately grasp the torque transmitted from the driving side to the driven side. For example, in the case of a screw tightening machine such as an impact wrench, it is necessary to accurately specify the tightening torque. There is a growing need to shorten assembly time while improving finish accuracy and safety, and it is essential in various assembly processes to reliably tighten to the specified torque without damaging parts, main bodies, etc. This is a request. In order to meet such demands, a small and highly accurate torque detector is essential.

Torque detectors suitable for such applications must meet stringent requirements, such as being small, lightweight, and requiring no or very easy maintenance. Conventionally, no torque detector has been available that satisfies all of these requirements.

SUMMARY OF THE INVENTION An object of the present invention is to provide a torque detector that is small, lightweight, and requires no maintenance, yet is capable of accurate torque measurement.

This purpose is to provide a torque detector having the structure described in the claims, that is, a strain gauge attached to a detection shaft and connected by a bridge, and a transformer for supplying voltage to the strain gauge. a voltage supply side transformer comprising a fixed core attached to a case, a fixed coil wound around the core, a rotating core disposed on a shaft, and a rotating coil wound around the core; A transformer for extracting the output of a gauge, which includes a rotating core disposed on a shaft, a rotating coil wound around the core, a fixed core attached to a case, and a fixed coil wound around the core. This is achieved by a torque detector having an output transformer comprising: a fixed coil and a rotating coil of the output transformer which are divided into two, and each coil is differentially connected.

The torque detector according to the present invention is extremely compact and
It is lightweight and accurate, and by utilizing its electrical output signal, control of the driven part at any torque is implemented to achieve the intended purpose.

The invention will now be disclosed with reference to the accompanying drawings, in which examples are shown.

FIG. 1 is a sectional view showing the structure of a torque detector 10 according to the present invention. In the figure, a plurality of strain gauges (not shown) are attached to the surface of the torque detection shaft 11, and each strain gauge is connected by a bridge. The shaded shaft is supported by bearings 12 and 13. The left end of the shaft is an input shaft 14 that should be connected to the drive section, and the right end is an output shaft 15 that should be connected to the driven section. In this embodiment, the input shaft 14 is configured to be detachable from the torque detection shaft.

The strain gauge attached to the surface of the torque detection shaft 11 is supplied with a predetermined voltage and generates an output voltage corresponding to the magnitude of the applied strain.
Since the strain gauge is attached to the surface of the rotating shaft, input and output must be exchanged by some method between it and the fixed case. In the present invention, a rotary transformer is used that utilizes the induction effect between cored coils disposed on both the rotating shaft side and the stationary side. Therefore, in order to supply voltage to the strain gauge, a voltage supply side rotating transformer is provided, which includes a fixed core 16, a fixed coil 17, a rotating core 18, and a rotating coil 19. The rotating core 18 is fixed on the shaft by a core holding nut 20. Also fixed core 1
6 is a fixed core holding nut 21 that also serves as a bearing box.
It is fixed to the case 22 by. A predetermined voltage is supplied from the input terminal 23 to the fixed coil 17 of the rotating transformer.

A voltage is induced by an inductive action between the fixed coil 17 and the rotating coil 19 that receive this voltage, and a predetermined voltage is supplied to the strain gauge on the detection axis.

The output of the strain gauge is connected to a pair of rotating coils 24 and 25 of an output side rotating transformer. These coil pairs are preferably wound in separate grooves in the rotary core 26 and connected in series so that their winding directions are opposite, and are differentially connected as a whole. The reason for this will be explained later. Note that the rotating core 25 is fixed onto the shaft 15 by a rotating core holding nut 27.

Fixed coils 28 and 29 and a fixed core 30 are attached to the case 22 to face the rotating coils 24 and 25 and the rotating core 26. A separator 31 is provided between the fixed core 16 of the voltage supply side rotating transformer and the fixed core 30 of the output side rotating transformer.
are maintained at predetermined intervals by

The output of the strain gauge on the detection shaft is connected in series with the rotating coils 28 and 29 on the output side. The fixed coils 24 and 25 on the output side are connected in series so that their winding directions are opposite, similar to the rotating coil. The bridge circuit output of the strain gauge is taken out from the output terminal 32 via the output side rotary transformer.

With the connection configuration described above, the coil and core of the rotary transformer on the output side of the strain gauge act as a normal transformer for the output of the strain gauge, but they act as a differential transformer for external signals. Acts as a dynamic transformer. Such a configuration is particularly suitable for a torque detector that is required to be small and lightweight yet extremely accurate, such as in the case of a screw tightening machine, for example.

That is, due to the strong demand for small size and light weight, it is not possible to make the distance between the voltage supply side coil and the output side coil sufficiently large until mutual interference is eliminated. It is also impossible to incorporate a sufficient amount of cores to prevent magnetic flux leakage. Due to the need to detect minute changes, it is also impossible to ignore the influence of the earth's magnetic field due to shaft rotation. Furthermore, since various external forces act upon screw tightening, the shaft may vibrate and the core gap may fluctuate, or the amount of leakage of the voltage supply side magnetic field lines may change due to axial movement.

In the torque detector according to the present invention, as described above, the output side coil acts as a normal transformer for signals and as a differential transformer for undesired external influences. Therefore, the output-side rotary transformer does not require any special noise countermeasures from the outside, so that the core and coil can be configured to be small and lightweight. Further, since there is no need to consider the influence on the output side of the voltage supply side rotating transformer, it is also possible to make it smaller and lighter. Furthermore, it is not necessary to use a special material for the core, and the structure as a whole is simplified, resulting in fewer breakdowns and extremely easy maintenance. Therefore, it meets the above requirements.

As described above, the torque detector according to the present invention has a small, lightweight, and simple configuration, and thus enables highly accurate torque measurement. Although this embodiment has been disclosed with reference to the application of a screw tightening machine, it is obvious that the invention can also be applied to other applications in which the torque transmitted from the drive side to the driven side is measured.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a torque detector according to the present invention. The correspondence of reference numerals in the figure is as follows. 1
... Torque detector, 11 ... Detection axis, 12, 13
... Bearing, 14 ... Input (drive) side shaft, 15 ...
Output (driven) side shaft, 16... Voltage supply side fixed core, 17... Voltage supply side fixed coil, 18... Voltage supply side rotating core, 19... Voltage supply side rotating coil, 20, 21... Core holder Natsuto, 22...
Case, 23... Input terminal, 24, 25... Output side rotating coil, 26... Output side rotating core, 27...
... Core holding nut, 28, 29 ... Output side fixed coil, 30 ... Output side fixed core, 31 ... Spacer, 32 ... Output terminal.

Claims (1)

[Claims] 1. A torque detector for detecting torque transmitted from a driving side to a driven side, comprising: a strain gauge attached to a detection shaft and connected by a bridge; and a voltage applied to the strain gauge. A transformer for supplying voltage, consisting of a fixed core attached to a case, a fixed coil wound around the core, a rotating core arranged on the shaft, and a rotating coil wound around the core. a supply side transformer, a transformer for extracting the output of the strain gauge, which includes a rotating core disposed on the shaft, a rotating coil wound around the core, a fixed core attached to the case, and the core. an output side transformer consisting of a wound fixed coil, the fixed coil and the rotating coil of the output side transformer are divided into two, and each coil is differentially connected. Detector.