Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2001-07-02
2002-10-29
Pyo, Kevin (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C073S862321, C356S152300
Reexamination Certificate
active
06472656
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a torque measuring device which measures torque of a rotating body, more particularly to a device for measuring torque of a rotating body, in which electricity and measurement signals are transmitted and received in a noncontact manner between a rotary section and a stationary section in order to measure torque of the rotating body with a strain gage, and to a method for measuring the torque.
2. Description of Related Art
Conventionally, a device, in which a plurality of strain gages connected so as to constitute a Wheatstone bridge circuit are attached by means of adhesive to a cylindrical distortion generating body connected between a rotating shaft and a load shaft driven by the rotating shaft and in which thereby a torsion quantity generated in the distortion generating body is converted into electricity quantity as torque quantity of a rotating body and transmitted to the stationary section, has been used for measurement of the torque of the rotating body. In this measuring device, important are a method for transmitting required electric power from a stationary section to a circuit on a rotary section and a method for transmitting to the stationary section an electrical signal gained by converting a torque quantity of the rotary section into electricity quantity where various problems have been pointed out in conventional mechanical contact methods.
In order to solve the above-mentioned problems with the mechanical methods, a method for converting an electrical signal of a rotating body into an optical signal and transmitting the optical signal to a stationary section: “Detection Signal Transmission Device for Physical Quantity-Electrical Quantity Converter for Rotating Body” has been proposed (Japanese Patent Laid-open No. Hei 6-301881). Hereinafter, measuring mechanism of the conventional “Detection Signal Transmission Device for Physical Quantity-Electrical Quantity Converter for Rotating Body” will be described based on FIG.
7
.
The measuring mechanism comprises five main parts including a torque transmission part, a photo coupling part, a torque detecting part, signal processing circuit part and electricity receiving part. The main parts relating to the invention will be explained as follows.
In
FIG. 7
, the torque transmission part is constituted as a so-called flexible coupling mechanism providing a connecting function with flexibility. The main mechanism thereof is formed symmetrically with respect to a distortion generating body
701
.
The photo coupling part is a mechanism which transmits a measured signal from a rotary section to a stationary section. A signal transmission part on the rotary section is constituted by a light emitting side ring
714
attached to the distortion generating body
701
and a plurality of light emitting diodes
721
which are electricity-into-light conversion elements and attached to the light emitting side ring
714
.
Moreover, a signal receiving part on the stationary section is constituted by a light receiving side ring
713
and a plurality of photodiodes
720
which are light-into-electricity conversion elements and attached to the light receiving side ring
713
. The light emitting side ring
714
of the signal transmission part is formed such that its inner periphery is fixed to the distortion generating body
701
, and its outer periphery is shaped substantially bowl-like in cross-section. The light emitting diodes
721
are attached to a bottom part of the bowl shape.
On the other hand, the ring
713
of the signal receiving part is formed such that its inner periphery is shaped substantially bowl-like, and the photodiode
720
are attached to a bottom part of the bowl shape. These two kinds of rings, namely the light receiving side ring
713
and the light emitting side ring
714
are arranged so that the substantially bowl-shaped opening portions face each other and are positioned close to each other. Eight pieces of the photodiodes
720
are attached to the inner periphery of the light receiving ring
713
. And, five pieces of the light emitting diodes
721
are attached along the entire periphery of the ring and are simultaneously lightened.
The distortion generating body
701
is a cylinder with a large diameter as a whole, where a distortion generating part
701
a
has a reduced thickness at its center area in the axial direction, and in the area with the reduced thickness, two side surfaces symmetrical with respect to the axis of the cylinder are shaved into flat surfaces. Strain gages
723
are attached to the flat portions and are incorporated into a Wheatstone bridge circuit
723
having two attached sheets (a pair) of the strain gages
723
as opposing sides.
The signal processing circuit
722
includes a circuit where a detection signal detected by the strain gages
723
attached to the distortion generating part
701
a
as the torque detecting part is appropriately amplified, waveform-shaped and signal-processed and where the processed signal is outputted to the photo coupling part comprising the light emitting diodes
721
and the photodiodes
720
.
The electricity receiving part is constituted by a noncontact-type rotary transformer. An electricity transmitting ring
711
on the stationary section and an electricity receiving ring
712
on the rotary section are arranged facing each other and close to each other. At opposing side surfaces of the rings
711
,
712
, a pair of substantially U-shaped ferrite cores (not shown) are mounted with their openings facing each other. An electricity transmitting coil
716
and an electricity receiving coil
717
are wound in a ring-like manner within respective spaces inside the substantially U-shaped ferrite cores.
In the conventional method for converting an electrical signal of the rotary section into an optical signal and transmitting the optical signal to the stationary section, there has been such a problem that a plurality of electricity-into-light conversion elements are arranged on the rotary section leading to an increased power consumption on the rotary section and therefore the size of a rotary transformer which transmits electric power from the stationary section to the rotary section has to be increased. There has been another problem that the rotary transformer for transmitting power and a light conversion part for transmitting a torque signal from the rotary section to the stationary section are separately structured, with the result that the device had to be increased in size and that it was difficult to properly position each part.
Moreover, since there were eight pieces of light receiving rings mounted at equal intervals and five pieces of light emitting diodes mounted at equal intervals throughout the entire ring and so on, making the manufacturing difficult and it was required to select elements which have small variance in characteristics from each other and which have a wide range (for example ±100 degrees) of directivity characteristics to uniformly transmit light.
Further, unless the five pieces of light emitting diodes are lightened simultaneously, the light emitting region is not shaped in an arch band of about 45°, forcing control of a drive circuit to be complicated. And, in case one or more of the light emitting diodes or the light receiving diodes fail to duly function, torque can not be detected at some places causing a problem.
Furthermore, the distortion generating body is a cylinder with a large diameter as a whole, but the distortion generating part which is a torque detecting part has a reduced thickness at its center area in the axial direction, and in the area with the reduced thickness, two side surfaces symmetrical with respect to the axis of the cylinder are shaved into flat surfaces, on which stress is concentrated causing a strength problem.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a device having a structure in which electric power is efficiently transmitted from a stationary section to a rotary section rotating
Minebea Co. Ltd.
Pyo Kevin
Sohn Seung C.
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