JPH0426707Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Field of Application) This invention relates to a device for reducing the load upon startup of a drive motor in an air compressor controlled by a pressure switch.

(Prior art and its problems) Conventional air compressors have a pressure switch that stops the drive motor when the pressure in the air tank exceeds a predetermined pressure, and starts it when the pressure drops below a predetermined pressure. Some use a control method.
In this case, it is necessary to reduce the load on the drive motor even when the drive motor is started. Conventionally, this starting load reduction device operates a solenoid valve by supplying power to a drive motor,
A method has been proposed in which a timer relay or the like is activated to maintain a no-load state for a predetermined period of time at startup.

However, devices that require electromagnetic valves, relays, or other electronic components are expensive and may cause electrical failures. Also,
A timer-based system always operates at a constant unloading time regardless of the pressure inside the air tank, resulting in unnecessary idle operation and wasteful consumption of compressed air.

(Technical issues of the invention) In view of the above-mentioned problems, this invention has been developed in the air compressor that uses a pressure switch control system.
Focusing on the fact that when the drive motor stops, the compression piston always stops at almost a predetermined position, and therefore the output shaft of the drive motor also stops at almost the same angular position, when the drive motor starts, the compressor load changes to It is an object of the present invention to provide a starting load reducing device for an air compressor that can easily start a drive motor by preventing the load from being applied to the motor.

(Means for Solving the Problems) In order to solve the above problems, a start-up reducing device for an air compressor according to this invention drives a compression piston in a compression cylinder by a drive motor,
In the air compressor that compresses the air in the compression cylinder and sends it into the air tank, a magnet is arranged around a part of the output shaft of the drive motor, and when the drive motor stops rotating, the output shaft A rotation detection valve for the drive motor is provided having a valve stem whose tip is placed close to the side that is not affected by the magnetic force of the magnet, and one of the rotation detection valves is connected to an air tank, and the other is connected to the air in the compression cylinder. The rotation detection valve connects the air tank to the unload valve when the drive motor stops rotating. It is characterized by being released into the atmosphere.

(Operations and Effects of the Invention) As described above, according to this invention, when the air pressure in the air tank exceeds a predetermined pressure and the pressure switch is turned off and the drive motor stops, the compression piston moves to reduce the air pressure in the compression cylinder. Since the stop is caused by the pressure balance between the air pressure and the air pressure in the air supply chamber that supplies air into the cylinder, the stop position is always approximately the same. As a result, the drive motor output shaft also stops at the same angular position, so that the magnet disposed on a part of the circumferential surface of the drive motor output shaft is also always oriented in substantially the same direction. By the way, the tip of the valve stem is placed close to the side of the output shaft that is not affected by the magnetic force of the magnet when the drive motor stops rotating, so when the drive motor stops rotating, it is released from the magnetic force of the magnet and the output is released. Move away from the axis. Due to this separation, the rotation detection valve of the drive motor detects that the rotation of the drive motor has stopped. At this time, the valve stem connects the air tank and the unload valve, and moves to a position where the unload valve releases the air in the compressed cylinder to the atmosphere. Therefore, the air pressure inside the compression cylinder becomes approximately equal to atmospheric pressure.

Further, when the air pressure in the air tank becomes less than a predetermined pressure, the pressure switch is turned on, and the drive motor starts to rotate, the air pressure in the compression cylinder is approximately equal to atmospheric pressure, so there is almost no load on the compression piston. Therefore, the drive motor can be started easily. By the way, since the output shaft also rotates during startup, the magnetic force of the magnet acts almost uniformly in the circumferential direction of the output shaft again, and this magnetic force causes the valve stem of the rotation detection valve of the drive motor to approach the output shaft. However, since the rotation detecting valve is connected to the unloading valve through the throttle passage, the operation of the unloading valve cannot quickly correspond to the operation of the valve stem.
In this way, even if the valve stem operates in response to the rotation of the output shaft, the operation of the unload valve is delayed a little, so the unloaded state of the compressor continues by that amount. This time is sufficient for the drive motor to reach a steady rotational speed.

Therefore, according to this invention, the load upon starting the drive motor can be reliably reduced with a simple structure.

(Example) Hereinafter, an example of this invention will be described with reference to the drawings.

In the figure, symbol A indicates an air compressor. This air compressor A includes a drive motor 5 provided in a housing 4 above an air tank 1 and a compressor main body 2 housed in a recess 1a of the air tank 1. It drives the machine body 2 and supplies the air compressed by the compressor body 2 into the air tank 1 through the discharge pipe 3.

That is, a motor stator 6 is provided within the drive motor housing 4a provided on the air tank 1, and a rotor 5a of the drive motor 5 fixed to the output shaft 9 is provided inside the motor stator 6. is,
Motor cooling fans 7 are formed on both sides of the rotor 5a. Further, inside the crankcase 4b, there is a crankshaft 10 fixed to one end of the output shaft 9 of the drive motor 5, and a connecting rod 1 whose one end is rotatably connected to the crankshaft 10.
1 is provided, a part of its side wall is opened, and an air filter 12 and an intake valve 13 are provided to form an air supply chamber. Compressor body 2
A compression piston 14 provided at the other end of the connecting rod 11 is slidably housed in a cylinder 2a, and a discharge chamber 1 formed in a cylinder head 2b is inserted into the cylinder 2a.
5 is provided with a discharge valve 16. A ventilation hole 17 is formed in the compression piston 14 to communicate the crankcase 4b, which also serves as an air supply chamber, and the inner space 15 of the cylinder 2a.A suction valve 18 made of an elastic body is provided at the end of the ventilation hole 17. ing.

Since compressor A is configured as described above,
When the drive motor 5 rotates, the crankshaft 10 and connecting rod 11 provided on the output shaft 9
is driven, and the compression piston 14 connected to the connecting rod 11 moves up and down within the cylinder 2a. When the compression piston 14 moves downward, the suction valve 18 is closed and the air in the cylinder 2a is compressed. At this time, the discharge valve 16 is opened, and the compressed air is sent to the other side of the discharge chamber 15. When the compression piston 14 moves upward, the air pressure inside the crankcase 4b becomes higher than the atmospheric pressure, so the intake valve 13 closes, and while the air pressure inside the case 4b becomes high, the air pressure inside the cylinder 2a becomes low. Intake valve 18 opens. A similar pressure difference closes the discharge valve 16. Therefore, the air in the crankcase 4b flows into the cylinder 2a through the ventilation hole 17. Compression piston 14 again
When the cylinder 2a moves downward, the air inside the cylinder 2a is compressed as described above, and at the same time, the internal pressure of the crankcase 4b is reduced, so the intake valve 13 opens and external air flows into the crankcase 4b through the air filter 12. Thereafter, the air supplied from the crankcase 4b into the cylinder 2a is similarly compressed by the vertical movement of the compression piston 14, and is continuously sent into the air tank 1 from the discharge valve 16 of the discharge chamber 15 via the discharge pipe 3. be provided. A check valve 19 is provided at the closed end of the discharge pipe 3, and the air tank 1
Backflow of compressed air fed into the interior is prevented.

Note that during the compressor operation, the air entering the housing 4 from the air intake port 8 is guided to the air flow guide 20 by the cooling fan 7, and is transferred to the compressor main body 2.
The air passes through the gap between the cylinder 2a and the recess 1a, cools the compressor body 2, prevents the temperature of the air inside the cylinder 2a from rising, and prevents the compression efficiency from being impaired.

By the way, when the pressure switch (not shown) that detects the air pressure in the air tank 1 is turned off and the drive motor 5 is stopped, the compression piston 14 is connected to the air pressure in the compression cylinder 2a and the supply supply that supplies air to the cylinder 2a. Since the stop is caused by the pressure balance with the air pressure inside the air chamber 4b, the stop position is always approximately the same. As a result, the drive motor output shaft 9 also stops at the same angular position.

Therefore, a load reduction device is provided that utilizes such characteristics of the output shaft 9 to reduce the load applied to the drive motor 5 when the drive motor 5 starts up.
This load reduction device is constructed as follows.

First, a disc-shaped member 21 made of a non-magnetic material is fixed to the end of the output shaft 9 of the drive motor 5, and a magnet 22 is further arranged on a part of the circumferential surface of the disc-shaped member 21. Therefore, when the pressure switch is turned on and the drive motor 5 is rotating, the magnetic force of the magnet 22 acts almost uniformly in the circumferential direction of the output shaft 9.

Next, a drive motor 5 is installed near the end of the output shaft 9.
A rotation detection valve 23 is provided. This rotation detection valve 23 brings the tip of a valve stem 25 slidably housed in a valve cylinder 24 close to the side of the output shaft 9 that is not affected by the magnetic force of the magnet 22 when the drive motor 5 stops rotating. In addition, one side of the valve cylinder 24 is provided with an air passage 26 communicating with an air tank, and the other side is provided with an air passage 27 communicating with an unload valve 30, which will be described later. Note that the passage 27 leading to the unload valve 30 is formed as a throttle passage, and the amount of air flowing through the passage 27 is restricted. At least the tip of the valve stem 25 is made of a magnetic material, and is normally biased away from the output shaft 9 by a spring 28. Therefore, while the drive motor 5 is rotating, the valve stem 25 is attracted toward the output shaft 9 side against the bias of the spring 28 due to the magnetic force of the magnet 22 provided on the output shaft 9, and approaches the air tank. 1 and to a position where the air passages 26 and 27 communicating with the unload valve 30 are blocked. On the other hand, when the drive motor 5 is stopped, it is separated from the output shaft 9 by the biasing force of the spring.
Move to the position where the air passages 26 and 27 are opened.

The unload valve 30 is provided on the side of the compression cylinder 2a, and a valve stem 32 is provided in a valve cylinder 31 having a passage 36 communicating with the rotation detection valve 23, and the discharge chamber 1 of the compression cylinder 2a is provided with a valve stem 32.
5 and a passage 34 leading to the atmosphere.
The valve stem 32 is normally urged by a spring 35 to a position where it blocks the passages 33 and 34, and compressed air is supplied from the rotation detection valve 23 through the passage 36. As a result, the valve stem 32 moves against the force of the spring 35 to a position where the passages 33 and 34 are opened.

Due to the load reduction device, when the drive motor 5 is rotating, the valve stem 25 of the rotation detection valve 23 of the drive motor 5 approaches the output shaft 9, and the valve stem 25 is connected to the air tank 1 and the unload valve 30. Since the unload valve 30 is held in a position that blocks the communicating passages 26 and 27, the unload valve 30 does not operate, and the discharge chamber 15 of the compression cylinder 2a is also blocked from the atmosphere.

On the other hand, when the air pressure in the air tank 1 exceeds a predetermined pressure and the pressure switch is turned off and the drive motor 5 stops, the valve stem 25 is released from the magnetic action of the magnet 22 and separated from the output shaft 9. , air tank 1 and unload valve 30
The unload valve 30 is operated to open the passages 33 and 34, and the compression cylinder 2a is moved to a position where the air in the discharge chamber 15 is released to the atmosphere. As a result, the air pressure inside the compression cylinder 2a becomes approximately equal to atmospheric pressure.

Furthermore, when the air pressure inside the air tank 1 falls below a predetermined pressure, the pressure switch is turned on, and the drive motor 5 starts to rotate, the internal pressure of the compression cylinder 2a is almost equal to atmospheric pressure, so the load on the compressor is sufficient. The load on the drive motor 5 is reduced. Therefore, the drive motor 5 can be started easily. By the way, when the drive motor 5 is started, the output shaft 9 also rotates, so the magnet 2 is turned on again.
The magnetic force of 2 acts on the rotation detection valve 23, and the valve stem 25 moves closer to the output shaft 9 again, but since the rotation detection valve 23 is connected to the unload valve 30 via the throttle passage 27, the unloading is stopped. The operation of the valve 30 cannot quickly correspond to the operation of the valve stem 25 of the rotation detection valve 23. In this way, even if the valve stem operates in response to the rotation of the output shaft 9, the operation of the unload valve 30 is delayed a little, so the unloaded state of the compressor continues by that amount. This time is sufficient for the drive motor 5 to reach a steady rotational speed.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of an air compressor according to this invention, and FIGS. 2 and 3 are cross-sectional views of the air compressor taken along lines X--X and Y--Y in FIG. 1, respectively. Code, A... Air compressor A, 1... Air tank, 1a... Recess, 2... Compressor body, 5... Drive motor, 9... Output shaft, 14... Compression piston, 20... Air Flow guide, 22...Magnet,
23... Rotation detection valve, 25, 32... Valve stem, 26, 27, 33, 34... Air passage,
30...Unload valve.

Claims (1)

[Scope of utility model registration request] In an air compressor in which a compression piston in a compression cylinder is driven by a drive motor to compress the air in the compression cylinder and feed it into an air tank, a portion of the circumferential surface of the output shaft of the drive motor is provided. A magnet is disposed, and a rotation detection valve for the drive motor is provided, the valve stem having a tip disposed close to the side of the output shaft which is not affected by the magnetic force of the magnet when the rotation of the drive motor is stopped; One of the valves is connected to the air tank and the other to the unload valve that releases the air in the compressed cylinder to the atmosphere through a throttle path, and when the drive motor stops rotating, the rotation detection valve connects the air tank and the unload valve. 1. A start-up load reduction device for an air compressor, characterized in that the air in the compression cylinder is released to the atmosphere by the unload valve.