JPH01198294A - Stoppage detector for fan motor - Google Patents

Abstract

PURPOSE:To reduce manufacturing cost, by detecting stoppage of a fan motor based on the variation of drive current and alarming abnormal stoppage thereof. CONSTITUTION:Variation of current flowing through a fan motor is converted through a small resistor R1 into the variation of voltage waveform, which is compared with a reference voltage and shaped into the waveform of signal level then the shaped waveform is fed to a retrigger monostable multivibrator IC2. The IC2 feeds the shaped waveform, as a fan sensor timing pulse, to a judging means(CPU)1. Since the width of the voltage signal varies in proportion to the rotary speed of the fan motor, the IC2 retriggers if the width of the signal is narrower than a predetermined level but the IC2 does not trigger if the width of the signal is wider than the predetermined level and fixed a high level. The CPU1 confirms the condition of the fan motor based on the pulse and the level thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an abnormal stop detection circuit for a brushless fan motor for cooling an electronic circuit.

[Conventional technology]

Conventionally, fan motors used for cooling electronic circuits are often AC motors, and to detect fan motor stoppage due to physical or electrical accidents, visual confirmation, scenery or fan motor rotation detection, current This has been confirmed by measurement, or indirectly by detecting the temperature rise around the motor using a temperature sensor. Due to the miniaturization of electronic devices and the increase in packaging density, fan motors are required to be made smaller, and there is also a lack of space within the device, making it difficult to install sensors or devices for detecting air volume or fan motor rotation, current measurement, etc. There is no room for placement.

[Problem to be solved by the invention]

In the case of conventional cooling using a fan motor, it is expensive to install various sensors to check for abnormal stoppage of the fan motor as shown in L, and it is difficult to provide enough space between parts to improve the cooling effect. This has become difficult due to the demand for miniaturization, and there is a problem in that circuit elements may be damaged due to temperature increase inside the device. SUMMARY OF THE INVENTION An object of the present invention is to provide a device that uses a DC brushless morph that is small and has a large air volume, detects stoppage of a fan motor from changes in drive current, and displays a warning of abnormal stoppage of the fan motor.

[Means to solve the problem]

In order to achieve the above object, the present invention detects an abnormality based on a change in the current flowing through the fan motor, and displays a warning indicating that the fan motor has stopped.

[Effect]

In the fan motor stop detection circuit configured as described above, a change in the current flowing through the fan motor caused by an accident such as a stoppage of the fan motor due to an object or a power disconnection of the fan motor is converted into a voltage signal. The determination means (CPU
I), and a warning to stop the fan motor is displayed according to the judgment of the judgment means (CPUI).

〔Example] An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a circuit diagram showing an example of the present invention, FIG. 2 is a flowchart showing operation states, and FIG. 3 is a time chart showing signal states.

Changes in the current flowing through the fan motor are converted into voltage changes of the waveform (Wl) shown in the time chart by a small resistor R1 (hereinafter referred to as resistance R'1, R2, etc.) (flow chart N1 is shown), and R2 The signal is compared with the reference voltage given by R3, shaped into a signal level waveform (W2) (N3), and sent to the retrigger monomulti IC2 (hereinafter referred to as IC2). 1 as the fan sensor timing pulse (FSTP, W3 or W4) by IC2.
(N
4). Since w2 in the voltage signal (W2) fluctuates in proportion to the rotation speed of the fan motor, [c2 is R of the circuit.
With the signal determined by the time constant of 5 and CI as the limit, signals below this are retriggered as normal human power, and signals above this are assumed to have no pulse input and are not retriggered, but are fixed at the 'HiBJ level. . The CPUI uses this pulse and its level to check the state of the fan motor (N5). As long as the fan motor is operating without any abnormality, the FSTP signal is continuously sent. CPU
No. 1 determines that the fan motor is rotating normally because this pulse is sent normally. If the fan motor is stopped due to a foreign object, a normal current flows through the fan motor and the voltage increases and is fixed at the 'HighJ level. C.P.U.I.
It is determined that the fan motor has stopped, and a signal is sent to the display circuit 2 to display a warning (N6).

When the fan motor stops due to a disconnection, etc., there is no pulse input to lc2, and it is fixed at the "rLow" (W5) level without retriggering. In this state, the CPU makes a judgment to stop the fan motor and displays a warning on the display circuit 2. Display (N
6). In the fan motor stop warning display, the present invention can determine whether the voltage level of the old GHJ is "forced stop due to obstruction" or "Low" and separately display the cause of the fan motor stop, such as wire breakage. This is an example of the application.

〔Effect of the invention〕

According to the present invention, a DC brushless motor that is small and has a large air volume is used, and abnormalities are detected from changes in drive current without using various sensors such as IT sensors and temperature sensors on the body of the fan motor. This system provides a warning display for abnormal stoppage, and can be produced at a lower cost than conventional systems that use various sensors. It can also distinguish between forced stoppage of the fan motor and stoppage due to wire breakage.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of the present invention, FIG. 2 is a flowchart showing operation states, and FIG. 3 is a time chart showing signal states.

Claims (1)

[Claims] In a fan motor using a DC brushless motor used for cooling electronic circuits of electronic devices, means for detecting a current flowing through the fan motor and converting it into a voltage waveform;
A comparison means for comparing the detected voltage waveform with a set reference voltage, a signal generation means for generating a pulse signal by a signal from the comparison means to enable retriggering, a means for determining the state of the pulse signal, and a means for determining the determination result. A fan motor stop detection device comprising display means.