JPH07111198B2 - Fan rotation abnormality detection method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fan rotation abnormality detection method for detecting a low rotation of a fan and outputting a rotation abnormality to a fan control unit.

[Prior Art] Conventionally, a fan sensor shown in FIG. 4 has been known as a fan sensor for detecting abnormal rotation of a fan of this type. FIG. 4 (a) is a plan view showing the structure of a conventional fan sensor, and FIG. 4 (b) is a side view thereof. In FIG. 4, reference numeral 10 indicates a blade, and the blade 10 is fixed to the rotary shaft 18. The detection plate 12 is attached to a part of the rotary shaft 18, and a protrusion 13 is provided at one position on the periphery of the detection plate 12. In addition, a permanent magnet 16 is provided so as to sandwich the detection plate 12.
Is installed outside the rotating shaft 18, and the output of the coil (not shown) wound around the permanent magnet 16 is transmitted from the detection circuit box 14 to the control unit (not shown) via the signal harness 24. The detection circuit box 14 is also connected with a DC power supply harness 26 including a reset signal line from the control unit and a detection circuit power supply line. Further, the fan motor 28 is connected with power harnesses 20 and 22 for the fan motor.

Next, a conventional rotation abnormality detecting method for a fan sensor having such a configuration will be described with reference to FIGS. 5 and 6. The detection plate 12 attached to the rotating shaft 18 rotates as the fan rotates. At this time, since the protrusion 13 of the detection plate 12 traverses the magnetic field created by the permanent magnet 16 once per one rotation of the fan, the coil (not shown) wound around the permanent magnet is
As shown in FIG. 5 (b), one pulse is generated for each rotation of the fan. The pulse generated by the rotation of the detection plate 12 is input to the base of the transistor 30 which constitutes the detection circuit provided in the detection circuit box 14 shown in FIG. The pulse amplified by the transistor 30 is sent to a waveform shaping circuit 32 via a resistor, shaped into a square wave, and then input to a counter circuit 34. The counter circuit 34 counts the number of input pulses and transmits the count output to the control unit through the signal harness 24. At this time, a reset signal is sent from the control unit to the counter circuit 34 at regular time intervals via the DC power harness 26, and the counter circuit 34 is periodically reset to zero. Therefore, the control unit monitors the number of pulses sent from the counter circuit 34 within a certain period of time, and when the number of pulses within the certain period of time decreases, it is determined that the fan is in a low rotation state, and the fan rotation abnormality detection signal is output. Operates to output a fan alarm signal.

[Problems to be Solved by the Invention] However, according to the above-described fan rotation abnormality detection method, since the counter circuit counts the number of pulses generated in proportion to the fan rotation speed, a counter IC or the like is used. In addition to requiring a lot of wiring such as a power supply line (power supply and ground) to the counter circuit in the fan sensor, a reset signal line to the counter circuit and a signal line for sending the output of the counter circuit to the control unit, The cost was high.
In addition, it is necessary to create a software program for the control unit to send a reset signal to the counter circuit or judge the rotation abnormality based on the count pulse number transmitted from the counter circuit and output a fan alarm signal, which is a troublesome task. Met.

Therefore, an object of the present invention is to provide a fan rotation abnormality detection method with a simple circuit configuration that uses a small amount of wiring.
Moreover, it is an object of the present invention to provide a fan rotation abnormality detection method that can reduce costs by eliminating the need for a software program for a control unit for determining a rotation abnormality and outputting a fan alarm signal.

[Means for Solving the Problems] A method for detecting abnormal rotation of a fan according to the present invention includes a detection plate attached to a rotation shaft of the fan, and a protrusion provided on a peripheral portion of the detection plate disposed outside the rotation shaft. Install a permanent magnet,
A fan configured to detect abnormal rotation of a fan based on a pulse generated from a coil wound around the permanent magnet when the protrusion of the detection plate passes through the magnetic field of the permanent magnet as the fan rotates. In the rotation abnormality detection method, the protrusion of the detection plate is formed in a gear shape, and a plurality of pulses generated per fan rotation when the gear-shaped protrusion of the detection plate passes through the magnetic field of the permanent magnet are detected. Together, these pulses are rectified through a bridge-type full-wave rectifier circuit composed of diodes, then converted to a DC voltage by a resistor and a capacitor, and the DC voltage obtained when the fan's normal rotation speed is at the lower limit is used as the reference voltage. Applying the DC voltage to a series circuit composed of a Zener diode and a resistor that conducts at the reference voltage, and using the output of the series circuit as a base input. The transistor open collector output structure, characterized in that retrieving the fan alarm signal.

[Operation] According to the fan rotation abnormality detecting method of the present invention, since the protrusion provided on the peripheral portion of the detection plate has a gear-like shape, the coil wound around the permanent magnet has one rotation per fan rotation. Generate multiple pulses. By converting these multiple pulses generated when the fan is operating normally to a DC voltage and setting the converted DC voltage to be the breakdown voltage of the Zener diode, the transistor that receives this breakdown current becomes The ON state is entered, and the detection circuit maintains the low level output that is the normal rotation signal. When the fan rotation is abnormal, the number of pulses generated in a certain period of time decreases, so the voltage value of the converted DC voltage also decreases. Therefore, the reference voltage corresponding to the lower limit of normal rotation set by the Zener diode is not reached, and the transistor is turned off.
As a result, the low rotation of the fan is detected, and the detection circuit can output a high-level fan alarm signal.

[Embodiment] Next, regarding the fan rotation abnormality detection method according to the present invention,
The following is a detailed description with reference to the accompanying drawings.

1A and 1B are schematic structural views of a fan sensor showing an embodiment of the present invention, FIG. 1A being a plan view, and FIG.
Is a side view. In this embodiment, the same components as those of the conventional example shown in FIG. 4 are designated by the same reference numerals, and detailed description thereof will be omitted. That is, in FIG. 1, a detection plate 15 having a continuous gear-shaped protrusion 17 is used instead of the detection plate 12 having the protrusion 13 shown in the conventional example, and a cable connected to the detection circuit box 14. 4 is different from FIG. 4 in that only the signal harness 25 is provided.

Next, a method for detecting the rotation abnormality of the fan according to the present embodiment configured as described above will be described with reference to FIGS. 2 and 3.

When electric power is supplied to the fan motor 28 from the power harnesses 20 and 22, the rotary shaft 18 and the blades 10 rotate. Along with that, the detection plate 15 having the gear-shaped protrusion 17 also rotates, and since the gear-shaped protrusion 17 of the detection plate 15 crosses the magnetic field created by the permanent magnet 16, a coil (not shown) wound around the permanent magnet 16 is formed. As shown in FIG. 2 (b), a pulse is generated by the number of teeth of the gear-shaped protrusion 17 per one rotation of the fan. In this case,
Sixteen pulses are generated for each rotation of the fan. A plurality of pulses generated by the detection plate 15 having the gear-shaped protrusion 17 are input to the detection circuit shown in FIG. 3 provided in the detection circuit box 14. The detection circuit rectifies a plurality of input pulses through a bridge-type full-wave rectification circuit composed of diodes 40, 41, 42, 43, and smoothes them with a resistor 44 and a capacitor 45 to convert them into a DC voltage. This DC voltage is applied to the series circuit of the Zener diode 46 and the resistors 47 and 48. In this way, the DC voltage obtained by rectifying and smoothing a plurality of pulses generated by the rotation of the detection plate 15 is
It changes in proportion to the fan speed.

Here, a DC voltage obtained by rectifying and smoothing the fan at the lower limit of the normal rotation speed is used as a reference voltage, and the gear-shaped protrusion 17 is provided so that the Zener diode 46 may break down at this reference voltage.
By setting the number of protrusions of the detection plate 15 having the above or using the Zener diode 46 having the breakdown voltage value of the reference voltage, the breakdown current can flow when the fan is normally rotating. As a result, the base current is supplied to the transistor 50 having the open collector output configuration through the resistor 49, the transistor 50 is turned on, and the low level signal is sent to the control unit through the signal harness 25.

When the fan is in an abnormal state of low rotation, the number of pulses per unit time decreases, and the DC voltage obtained by rectifying and smoothing also decreases and does not reach the reference voltage. Therefore, the Zener diode 46 does not break down, no current is supplied to the base of the transistor 50, the transistor 50 is turned off, and a high-level fan alarm signal is sent to the control unit through the signal harness 25. Therefore, the detection circuit can detect the abnormal rotation of the fan.

[Effects of the Invention] As is apparent from the above-described embodiments, according to the present invention,
The zener diode breaks down the DC voltage obtained by rectifying and smoothing by making the detection plate for detecting abnormal rotation of the fan into a gear shape and making the number of generated pulses multiple per rotation of the fan. Since such a high voltage can be used, the breakdown voltage of this Zener diode can be used to detect fan rotation anomalies, and in addition to the counter ICs and other parts required by the conventional technology, these counter No need for power lines or signal lines to ICs. That is, the detection input signal itself uses the voltage obtained by rectifying and smoothing the pulse, and the output of the detection circuit is an open collector configuration, so that the detection circuit power supply line from the outside and the reset from the control unit to the counter circuit are performed. No need for signal lines.

In addition, unlike the conventional method of counting the number of pulses, the rotation abnormality is detected by the ON / OFF signal of the transistor of the detection circuit itself and the fan alarm signal is directly output as the detection signal, so the rotation abnormality like the conventional one is detected. It is not necessary to create a software program for the control unit for detecting.

Therefore, according to the present invention, in the fan rotation abnormality detection method, since the number of wirings used is small and the circuit configuration is simple, the effect of contributing to the reduction of manufacturing cost is extremely large.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and it is needless to say that various design changes can be made without departing from the spirit of the present invention.

[Brief description of drawings]

1 (a) and 1 (b) are schematic views of a fan sensor applied to the fan rotation abnormality detection method according to the present invention.
FIG. 2A is a plan view, FIG. 2B is a side view, and FIG. 2A is a schematic view showing a detection plate having gear-shaped protrusions used in the fan rotation abnormality detection method according to the present invention together with fan blades. ,
2 (b) is a waveform diagram showing the pulse output per one rotation of the fan when the detection plate having the gear-like protrusions of FIG. 2 (a) is used, and FIG. 3 is the rotation of the fan according to the present invention. FIG. 4 is a circuit diagram showing an embodiment of a fan alarm detection circuit for implementing the abnormality detection method, and FIGS. 4 (a) and 4 (b) are schematic diagrams of a fan sensor applied to a conventional fan rotation abnormality detection method. 5A is a plan view, FIG. 5B is a side view, FIG. 5A is a schematic view showing a detection plate used in a conventional fan rotation abnormality detection method together with fan blades, and FIG. FIG. 5A is a waveform diagram showing a pulse output per one rotation of the fan when the detection plate of FIG. 5A is used, and FIG. 6 is a fan alarm detection circuit diagram for implementing the conventional fan rotation abnormality detection method. 10 …… Vane, 12 …… Detection plate 13 …… Projection part, 14 …… Detection circuit box 15 …… Detection plate, 16 …… Permanent magnet 17 …… Gear-shaped projection 18 …… Rotary shaft, 20,22… … Power harness 24 …… Signal harness, 25 …… Signal harness 26 …… Power harness, 28 …… Fan motor 30 …… Transistor, 32 …… Wave shaping circuit 34 …… Counter circuit, 44,47,48,49… … Resistance 40,41,42,43 …… Diode 45 …… Capacitor, 46 …… Zener diode 50 …… Transistor

Claims (1)

[Claims] 1. A detection plate is attached to a rotation shaft of a fan, and a permanent magnet is installed outside the rotation shaft so as to sandwich a protrusion provided on a peripheral portion of the detection plate, and the permanent magnet of the permanent magnet is rotated as the fan rotates. In a fan rotation abnormality detection method configured to detect a fan rotation abnormality based on a pulse generated from a coil wound around the permanent magnet when a protrusion of the detection plate passes through a magnetic field, The protrusion is formed in a gear shape, and a plurality of pulses generated per one rotation of the fan when the gear-shaped protrusion of the detection plate passes through the magnetic field of the permanent magnet are detected, and these pulses are composed of diodes. After rectifying through a bridge-type full-wave rectifier circuit, convert it into a DC voltage with a resistor and a capacitor, and use the DC voltage obtained at the lower limit of the normal rotation speed of the fan as the reference voltage, It is characterized in that the DC voltage is applied to a series circuit composed of a Zener diode and a resistor which conducts at a reference voltage, and a fan alarm signal is taken out by a transistor having an open collector output configuration with the output of the series circuit as a base input. Fan rotation abnormality detection method.