JPH0134523Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an overload detection device for rotating electric machines.
In particular, the present invention relates to an overload detection device for a rotating electrical machine that detects an overload state based on the temperature of the shaft of the rotating electrical machine.

[Conventional technology]

In general, when rotating electric machines such as electric motors and generators used as various power sources and power generation sources are driven above their rated output, they enter a so-called overload state and the rotational speed increases, causing a rise in temperature in various parts, and bearings It is easy to cause burnout accidents such as wires and windings. For this reason, they are usually operated at a load that is at or below the rated load.

For such load control, for example, a load cell is interposed between the motor shaft and the driven object, or a strain gauge is attached to the shaft, and the output of these load detectors is used to detect the load. A method is often adopted in which the control amount is determined by comparing the load value with a predetermined load setting value.

However, when a load cell is used, a space is required to mount the load cell, and the device configuration becomes complicated, so it is not suitable for anything other than large machines. Furthermore, since strain gauges are easily affected by vibrations, it is not necessarily the best option to attach them directly to the shaft because of reliability problems.

Therefore, in recent years, in order to solve the above-mentioned problems, an overload detection device has been proposed that detects the temperature of a predetermined location of a rotating electrical machine to detect that the rotating electrical machine has become overloaded.

This conventional example is shown for the electric motor shown in FIG. As shown in this FIG. A temperature detection element 8B is provided inside the pole winding 4. The outputs of these temperature detection elements 8A and 8B correspond to the temperatures of the respective mounting parts of the temperature detection elements 8A and 8B (i.e., the yoke 6 and the main pole winding 4) when the motor 2 is overloaded. An overload on the electric motor 2 was detected by monitoring whether the value reached the specified value.

[Problem to be solved by the invention] However, in the above-mentioned conventional technology, if the temperature detection elements 8A and 8B are attached directly to the rotor 12 that drives the shaft 10 or the shaft 10, overload detection can be performed with high accuracy. However, since the shaft 10 and the rotor 12 have a rotating structure and have large mechanical vibrations, there is a large possibility that the temperature detection elements 8A and 8B will be damaged, which is not preferable. In addition, the shaft 10 is connected to the covers 14 and 1.
6 via a bearing 18, it is difficult and impractical to route the signal lines of the temperature detection element attached to the shaft 10 and rotor 12. Therefore, in the prior art, the rotor 1, which is most sensitive to temperature rise during overload,
2.Since the surrounding temperature is not directly detected, the detection operation not only lacks precision, but also causes a delay in overload prevention, which is a practical disadvantage in that the function cannot be fully fulfilled. It was hot.

[Purpose of invention]

SUMMARY OF THE INVENTION An object of the present invention is to overcome the disadvantages of the prior art and to provide an overload detection device for an electric motor that has a simple configuration and can more accurately detect overload conditions.

[Means to solve the problem]

Therefore, in the present invention, the rotating shaft of the rotating electric machine is provided to protrude outward from one end of the stator case, and a heat-sensitive tape is attached to this protruding shaft portion, and a A light emitting means and a light receiving means are arranged to face each other. and,
The stator case is equipped with a dark box that shields the entire heat-sensitive tape portion, including the light emitting means and the light receiving means, from external light. This aims to achieve the above-mentioned purpose.

[Example of idea]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In the embodiment shown in FIGS. 1 to 3, the rotor shaft 62 of the rotating electric machine 22 is provided to protrude outward from one end of the housing 24 as a stator case, and the protruding shaft portion 62A is A liquid crystal display tape 64 as a heat-sensitive tape is attached, and a light emitting diode 34 as a light emitting means and a phototransistor 38 as a light receiving means are arranged close to and facing the liquid crystal display tape 64 portion.

The liquid crystal display tape 6 includes the light emitting diode 34 and the phototransistor 38 as a light receiving means.
A dark box 61 that shields the entire four parts from ambient light is
It is attached to the housing 24. The light emitting diode 34 and the phototransistor 38 constitute a photo sensor 66. The signal detected by the phototransistor 38 of the photo sensor 66 is sent to a signal processing circuit 58 as shown in FIG. This signal processing circuit 58 is actually mounted on a printed circuit board 60 together with a photo sensor 66 as shown in FIGS. 1 and 2. This printed circuit board 60 is supported by an L-shaped metal fitting as shown. In this case, a through hole 60A with a predetermined diameter is provided at the center of the printed circuit board 60, and the tip 62A of the rotor shaft 62 of the electric motor 20 (the tip opposite to the output side) is inserted into the through hole 60A. It is inserted for a predetermined length.

Then, the tip shaft portion 6 of the rotor shaft 62
A thin film-like liquid crystal display tape 64 as a heat-sensitive tape is wound around 2A with a predetermined width. This liquid crystal display tape 64 is made of a thin film in which liquid crystal is press-fitted and sealed, and its color changes depending on the temperature. Therefore, the shaft portion 62A
Since the rotor is directly wound around the rotor, it is possible to directly detect the temperature of the rotor and its vicinity more precisely and quickly than in the conventional example.

The signal processing circuit 58 includes a comparator 46 that compares the output of the phototransistor 38 with a predetermined reference value, and an on/off state depending on the output of the comparator 46.
It includes a switching transistor 48 whose emitter is grounded to turn off, a constant voltage circuit 32 and voltage dividing resistors 42 and 44 that set a reference value in the comparator 46.

This signal processing circuit 58 is also provided with an operation panel 28 . This operation panel 28 includes a power switch 30 for applying the power source 26 to the constant voltage circuit 32.
and an overload indicator lamp 52 that illuminates and displays the result of signal processing by the signal processing circuit 58 described above to indicate whether or not the rotating electric machine 22 is overheated.

To explain this in more detail, this power switch 26
The positive side of the voltage is connected via a power switch 30 in the operation panel 28 to a constant voltage circuit 32 consisting of a three-terminal regulator or the like. The output side of the constant voltage circuit 32 is connected to the negative side of the power supply 26 via a light emitting diode 34 as a light emitting means and a bias resistor 36, each connected in series. Further, on the output side of the constant voltage circuit 32, a closed circuit is constructed by connecting a phototransistor 38 as a light receiving means and a resistor 40 in series. Further, the output side of the constant voltage circuit 32 is formed so that the output is voltage-divided by resistors 42 and 44 and applied as a reference potential to a non-inverting input terminal of a comparator 46 as comparison means. The inverting input terminal of the comparator 46 is connected to the emitter of the phototransistor 38.

The output terminal of the comparator 46 is connected to the base of an NPN type switching transistor 48 and a resistor 50 whose one end is connected to the output side of the constant voltage circuit 32.
are connected to the other end of each. The emitter of this transistor 48 is connected to the negative side of the power source 26, and the collector is connected to the positive side of the power source 26 via an overload indicator lamp 52 in the operation panel 28. Here, numerals 54 and 56 are smoothing capacitors.

Next, the overall operation of this embodiment will be explained.

A potential as a reference value is applied to the non-inverting input terminal of the comparator 46. This reference potential is detected by the phototransistor 38 which is detected when the temperature of the rotor shaft 62 increases under an overload condition of the motor 22 and the color of the liquid crystal display tape 64 changes to correspond to the maximum allowable value of this temperature. is the output value.

Therefore, for example, if the power switch 30 is configured to be linked to the main switch of the electric vehicle, the signal processing circuit 58 will be activated when the main switch is turned on to power on the electric vehicle. Operate.

Then, along with the above operation, arrow A in FIG.
The light emitted from the light emitting diode 34 is irradiated onto the liquid crystal display tape 64 wrapped around the shaft portion 62A. At this time, the rotor shaft 62 is rotating, for example, in the direction of arrow B, but since it is wrapped around the entire circumference with a predetermined width, the rotor shaft 62 is rotated on the liquid crystal display tape 64 regardless of the rotation angle or some vibration. It is now possible to irradiate. A part of this irradiation light A becomes transmitted and scattered light depending on the color of the liquid crystal display tape 64 at that time, and the rest reaches the phototransistor 38 as reflected light as indicated by arrow A', and is used for activation. It will act as light energy. Therefore, the increase or decrease of this reflected light A' is determined by the color of the liquid crystal display tape 64 at that time.
These relationships will be specifically explained below.

When the motor 22 is under the rated load, the temperature of the shaft 62 is low, so the liquid crystal display tape 64 is in its normal color, for example, approximately black, and at this time, the output of the phototransistor 38 is smaller than the reference value, so The output of comparator 46 becomes a predetermined "low" level. As a result, since switching transistor 48 remains off, overload indicator lamp 52 does not light up.

Now, if we consider a case where the electric motor 22 becomes overloaded for some reason, as the load increases, the rotational speed of the rotor increases and the temperature of the shaft 62 increases, which causes the liquid crystal display to increase. The color of the tape 64 gradually changes to a color corresponding to high temperature, for example, to approximately white, and the output signal of the phototransistor 38 changes accordingly.

When the electric motor 22 is overloaded, the liquid crystal display tape 64 becomes approximately white, and as a result, the output signal of the phototransistor 38 exceeds the reference value, so that the comparator 46 outputs a "high level" signal.
The output turns on switching transistor 48. As a result, the overload indicator lamp 52 lights up, notifying the operator of the electric vehicle that the electric motor 22 has become overloaded.

In this way, it is detected and displayed that the motor 22 has become overloaded, so unlike the conventional example, the circuit configuration is relatively simple and there is no mechanical contact with the part to be measured. However, the temperature detection, that is, the load state can be detected more accurately and precisely.

[Other Examples]

By the way, the above-mentioned embodiment only has the function of displaying a warning to the operator when an overload condition is detected, but it is possible to stop the machine or set it to a predetermined standby condition when an overload condition is detected. It may be configured to wait for the operator's instruction input at the step . An example in that case will be described below.

FIG. 4 shows another embodiment of the present invention, in which reference numeral 68 indicates an overload detection section. Here, the same reference numerals are used for the same components as in the above-described embodiment.

The output signal of the phototransistor 38 as a light receiving means is applied to an analog/digital converter 72 via an amplifier 70 and converted into a digital signal. This digital signal is applied to microcomputer 74. With this microcomputer 74, amplifier 70, and A/D converter 72,
A signal processing circuit 58A is formed.

This microcomputer 74 constantly compares the received digital signal with a digital reference value corresponding to the overload state of the motor 22, and determines that the motor 22 has become overloaded when the digital signal exceeds the digital reference value. do. When this overload state is detected, each part 76 of the main body is controlled to a predetermined state. For example, the power supplied to the electric motor 22 may be reduced to a predetermined low level, or the machine may be completely stopped.

At the same time, the microcomputer 74
An overload warning is displayed on the operation panel 78, and then an alarm sound is emitted to call the operator's attention.

Furthermore, since the microcomputer 74 has a large degree of freedom, it can perform even more controls.

In addition, liquid crystal display tape 64 is used as a thermal tape.
It is not limited to. Further, the manner in which the color state of the thermosensitive tape changes is not limited to the above-mentioned example, and may be a two-stage color change using the set temperature as a reference value. In that case, a spectral filter may be provided in the photodiode as the light emitting element and the phototransistor as the light receiving element depending on the color of the overload state. In addition, this invention
The present invention is not limited to electric motors, but can also be applied to generators as rotating electric machines.

[Effect of idea]

As described above, according to the present invention, a heat-sensitive tape is pasted on the rotating shaft portion extending outside from a rotating electrical machine, and changes in the temperature of the rotating shaft, that is, overheating of the rotating electrical machine, are detected based on changes in light reflected from the heat-sensitive tape. Since it is configured to detect the presence or absence of a load condition, it is possible to detect the presence or absence of an overload condition quickly and without contact, and by covering the entire photo sensor part, including this heat-sensitive tape, with a dark box, It is possible to almost completely eliminate the influence of ambient light, and as mentioned above, it can be installed externally on the rotating shaft that extends from the rotating electrical machine, so it can be easily installed on existing rotating electrical machines. It is possible to provide a practical overload detection device for a rotating electrical machine that has the versatility of being able to be installed.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway front view showing an embodiment of the present invention, Fig. 2 is a partial sectional view taken in the direction of the arrow in Fig. 1, and Fig. 3 is a photodetector detected by the photo sensor shown in Fig. 1. Circuit diagram for processing signals, 4th
The figure is a block diagram showing another embodiment, and FIG. 5 is an explanatory diagram showing a conventional example. 20, 68... Overload detection unit, 22... Electric motor as rotating electric machine, 34... Light emitting diode as light emitting means, 38... Phototransistor as light receiving means, 58, 58A... Signal processing circuit,
61... Dark box, 62A... Shaft section, 64...
Liquid crystal display tape as thermal tape.

Claims (1)

[Scope of Claim for Utility Model Registration] A rotating shaft of a rotating electric machine is provided to protrude outward from one end of the stator case, and a heat-sensitive tape is pasted to the protruding shaft portion, and a portion of the rotating electrical machine is protruded from the shaft portion. Further, a dark box is attached to the stator case, and a dark box is provided in which a light emitting means and a light receiving means are disposed facing each other, and the entire heat sensitive tape portion including the light emitting means and the light receiving means is shielded from ambient light. Overload detection device for rotating electric machines.