JPH10159748A - Operation control mechanism compatible with power capacity for two-stage compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimally control a load depending on power capacity by forming two or more exhaust ports on a connecting tube between the delivery port of a pre-stage compression chamber and the intake port of a post-stage compression chamber, providing each exhaust port with a solenoid valve and controlling the solenoid valve, when drive current for an electric motor becomes equal to a load control start current value. SOLUTION: A two-stage compressor for feeding the compressed air to a pneumatic work machine such as a pneumatic nail driver, has a connecting tube 6a for connecting the delivery port 4b of a pre-stage compression chamber 2 and the intake port 5a of a post-stage compression chamber 3 to each other, and the delivery port 5b of the post-stage compression chamber 3 is connected to a compressed air reservoir 7 via a connecting tube 6b. In this case, exhaust ports 8a and 8b are formed on the connecting tube 6a, and respectively fitted with a first and a second solenoid valves SV1 and SV2. A control part 10 makes judgement about the load status of an electric motor 1 on the basis of a current value measured with a measurement means for measuring current flowing in a drive circuit. When the drive current becomes equal to a load control start current value, both of the solenoid valves SV1 and SV2 are controlled, thereby causing the valves SV1 and SV2 to control a load on the electric motor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stage compressor having a two-stage compression chamber for performing a gas compression operation by a common motor, and controls a load generated in the electric motor in accordance with a capacity of a power supply. The present invention relates to an operation control mechanism corresponding to a power supply capacity in a two-stage compressor.

[0002]

2. Description of the Related Art In general, a two-stage compressor for supplying compressed air to a pneumatic working machine such as a pneumatic nailing machine has two compression chambers. In this arrangement, the gas compressed in the first-stage compression chamber is further compressed in the second-stage compression chamber, and the discharge port of the second-stage compression chamber is connected to the compressed-gas storage tank. In each compression chamber, intake air is compressed by a piston-cylinder mechanism, and a piston rod of each piston is connected to an output shaft of a common electric motor to be integrally formed.

In a normal compressor, the electric motor is selected to have an output corresponding to the discharge load of the compression mechanism at the maximum pressure. Furthermore, a pressure switch that operates at the maximum pressure value is provided, and when the pressure in the tank rises to a predetermined value, the power supply of the motor is shut off and stopped, or the unload mechanism is operated to idle the compressor. doing.

[0004]

The operating state of the compressor at an intermediate pressure or lower which is close to the air pressure used by a tool such as a nailing machine has a sufficient margin for the electric motor. In the high pressure region, load control is performed to reduce the load on the electric motor by detecting the load condition of the electric motor and reducing the load on the electric motor by setting the discharge amount under the pressure to be large. Good driving is being done.

[0005] However, the capacity of the power supply for supplying power to the compressor is not always sufficient to operate the compressor. In particular, at exhibitions, etc., power is often supplied from a 15A capacity breaker for home use, and if the voltage drop increases due to the use of an extension cord, the current value rises with the pressure rise and the breaker operates. As a result, the compressor stopped working, and it was conceived that there was a problem with the compressor, which hindered sales promotion activities.

[0006] In addition, even in an actual work site, if the capacity of the power supply is not sufficient or if power is supplied to a plurality of devices from the same breaker, the breaker may operate. The work was interrupted, and each time the breaker located away from the site had to be replaced, the work efficiency could be reduced. The present invention solves the above problems, performs an optimal load control according to the capacity of a power supply, and operates an operation control mechanism in a two-stage compressor that efficiently operates a two-stage compressor without operating a power breaker. Is to provide

[0007]

In order to solve the above-mentioned problems, an operation control mechanism corresponding to a power supply capacity in a two-stage compressor according to the present invention compresses intake air by a piston / cylinder mechanism operated by a common power supply motor. A two-stage compression chamber that discharges and discharges the air, and the discharge port side of the first-stage compression chamber and the suction port side of the second-stage compression chamber are connected by a connecting pipe and arranged, and the discharge port of the second-stage compression chamber is compressed. In a two-stage compressor connected to a gas storage tank and supplying compressed air to a terminal such as a pneumatic nailer connected to the compressed gas storage tank, the connection pipe has at least two exhaust ports, An electromagnetic valve is provided at each exhaust port, and when the drive current of the electric motor reaches the load control start current value, the electromagnetic valve is controlled to reduce the load on the electric motor, and is input by the input means. Characterized by comprising a control unit for changing the setting of the load control start current value based on the power capacity of the information.

[0008]

1 and 2 show a perspective view and a block diagram of a two-stage compressor. The two-stage compressor uses a common electric motor 1 to operate a piston / cylinder mechanism to intake air. The two-stage compression chambers 2 and 3 for compressing and discharging are combined with a discharge port 4b of the front compression chamber 2 and an intake port 5a of the rear compression chamber 3
Are connected by a connecting pipe 6a, and the discharge port 5b of the compression chamber 3 at the subsequent stage is connected to the compressed gas storage tank 7 by a connecting pipe 6b.
Are mounted on two compressed gas storage tanks (hereinafter referred to as tanks) 7 connected to each other.

The compression chamber 2 in the first stage and the compression chamber 3 in the second stage
An exhaust port 8a and an exhaust port 8b are formed in the connecting pipe 6a between the first and second solenoid valves, and a first solenoid valve SV1 is provided in the exhaust port 8a, and a second solenoid valve SV2 is provided in the exhaust port 8b. I have.

The drive circuit for the electric motor 1 includes:
A pressure switch PS and a measuring means 9 for measuring a current flowing through the drive circuit are provided. The information on the drive current measured by the measuring means 9 is input to the control unit 10 for controlling the solenoid valves SV1 and SV2. Reference numeral 11 denotes a power switch, 12 denotes a transformer, 13 denotes a rectifier circuit for supplying DC power to a control unit and an electromagnetic valve, and 14 denotes a terminal such as a pneumatic nailing machine.

The pressure switch PS is arranged in the tank 7,
The measured pressure is set so that it operates when the internal pressure of the tank 7 reaches the maximum pressure to open the drive circuit of the motor and stop the electric motor 1.

The measuring means 9 is constituted by a current sensor such as a CT type current sensor, measures the current flowing through the motor drive circuit, and the measured current value is input to the control unit 10.

The control unit 10 may be constituted by a microprocessor, and determines the state of the load of the electric motor 1 from the current value measured by the measuring means 9 according to a control program stored in advance in a built-in memory. Control the solenoid valves SV1 and SV2 to control the load on the electric motor 1 when the load control start current value for reducing the load on the electric motor 1 or the load control release current value for releasing the load reduction is reached. Have been.

The control unit 10 is provided with a switch 15 which is a means for inputting power supply capacity information. The switch 15 is constituted by an ON / OFF switch such as a toggle switch. The ON / OFF state of the switch 15 is detected by the control unit 10, and the set values of the load control start current value and the load control release current value are changed. It is programmed to be. The switch 15 is used to manually switch the power supply capacity (breaker capacity) to 15 A or 20 A or more to inform the control unit 10 of the power supply capacity information. 15A and the load control start current value is set to A1.
(14.5 A), the load control release current value is changed to A2 (13.0 A).
A), and if it is in the OFF state, the breaker capacity is determined to be 20 A or more, and the load control start current value is set to A1 ′ (1
7.5A), the load control release current value is changed to A2 '(14.0
A) is programmed to be set.

Next, the operation of the operation control mechanism of the two-stage compressor will be described with reference to the block diagram of FIG. 2 and the flowchart of FIG.

The capacity of the power source (capacity of the breaker) is checked in advance, and if the capacity of the breaker is 15 A, the changeover switch is turned on.
F. Then, the power switch 11 is turned on to operate the two-stage compressor. In step ST1, the state of the pressure switch PS is confirmed. If the pressure in the tank 7 has reached the maximum pressure, the pressure switch PS operates (OFF).
Since the drive circuit of the electric motor 1 is opened, the electric motor 1 does not operate, and waits in step ST1 until the pressure in the tank 7 decreases. In this state, terminal 1
When the pressure switch PS is used, the pressure in the tank 7 decreases and the pressure switch PS returns (ON), and the process proceeds to step ST2. The pressure switch PS returns (ON) and the electric motor 1
When the drive circuit is closed, the electric motor 1 rotates and the piston 16 reciprocates inside the compression chambers 2 and 3.
When the piston 16 moves downward in the compression chamber 2 in the preceding stage, the volume in the compression chamber 2 expands. Therefore, the differential pressure between the intake port 4a and the inside of the compression chamber 2 opens the intake valve 17, and the gas in the compression chamber 2 Is supplied. At this time, the discharge valve 18 remains closed. At the same time, in the compression chamber 3 at the subsequent stage, the piston 16 moves upward and the volume in the compression chamber 3 is reduced, so that the differential pressure between the interior of the compression chamber 3 and the discharge port 5b opens the discharge valve 18 to open the compression chamber 3. Is discharged from the discharge port 5b. At this time, the intake valve 17 remains closed. The compressed gas discharged from the discharge port 4b of the first compression chamber 2 is sent to the suction port 5a of the second compression chamber 3 via the connecting pipe 6a, and is further compressed in the compression chamber 3 and discharged from the discharge port 5b. Discharged connecting pipe 6
After that, it is stored in the tank 7. By the way, when the pressure in the tank 7 increases, the load on the electric motor 1 increases,
As shown in the pressure / drive current characteristic curve of FIG. 4, the drive current of the electric motor 1 increases as the load increases (the pressure increases). Since the drive current of the electric motor 1 is measured by the current sensor 9 and input to the control unit 10,
The control unit 1 constantly monitors the input drive current information.
0 controls the solenoid valves SV1 and SV2 to execute the control operation process of the two-stage compressor.

If a timer interrupt occurs during the execution of the control operation processing, the control unit 10 temporarily suspends the processing, takes an interrupt procedure, jumps to an interrupt processing routine, and executes a timer interrupt processing program. In this timer interrupt process, it is determined whether or not the changeover switch 15 has been operated (step ST20). If the changeover switch 15 has not been operated, the interruption is terminated and the process returns to the main routine to execute the control operation process. Is operating, the state of the changeover switch 15 is determined (step ST21). If the changeover switch 15 is ON, it is determined that the power supply capacity is small (the breaker is 15 A), the process proceeds to step ST22, and the load control start current value A1 is set to 1
At 4.5 A, the load control release current value A2 is set to 13.0 A and the interrupt is terminated. If the changeover switch 15 is OFF, it is determined that the power supply capacity is large (the breaker is 20 A or more), and the process proceeds to step ST23. The load control start current value A1 'is 17.5A, and the control release current value A2' is 14.0A.
Set to A to end the interrupt. Upon completion of the interrupt, the process returns to the main routine and continues the control operation processing. Although the drive current measured by the current sensor 9 increases with an increase in load (an increase in pressure), the control unit 10 sets the drive current to a load control start current value A1 or A
It is determined whether it is 1 'or less (step ST2). If the switch 15 is ON, the control level is increased by one step at the load control start current value A1 or more, and if the switch 15 is OFF, the control level is increased by one step at the load control start current value A1 'or more (step ST3). This control level indicates the open state of the solenoid valve, and when the control level is 0, the solenoid valve SV1,
If SV2 is OFF (closed), 1 if solenoid valve SV
1 is ON (open) state, solenoid valve SV2 is OFF state, 2
In this case, the ON / OFF of the solenoid valves SV1 and SV2 is controlled by the control signals c1 and c2 output by the control unit 10 so that the solenoid valves SV1 and SV2 are turned on.

In the initial state, at the control level 0, the electric motor 1
Is started, when the switch 15 is ON, the drive current first reaches the load control start current value A1 (point a) (when the switch 15 is OFF, the drive current reaches A1 '( at point a ')) level 1 and step ST
7. In ST8, only the solenoid valve SV1 is turned on to open the exhaust port 8a. When the exhaust port 8a is opened, the gas of the primary pressure that has been compressed in the compression chamber 2 at the previous stage and passed through the connecting pipe 6a is discharged.
a, the pressure on the intake side introduced from the intake port 5a into the compression chamber 3 at the subsequent stage is reduced, and the driving force for driving the piston 16 in the compression chamber 3 at the subsequent stage can be reduced, so that the electric motor 1 is reduced. Thereafter, returning to step ST1, it is determined again whether or not the pressure in the tank 7 has reached the maximum pressure, and if not, it is determined whether or not the drive current is equal to or less than the load control start current value A1 or A1 '. . The load control start current value A1 is reached (b
(Point) or the load control start current value A1 'has been reached (point b'), the process proceeds to step ST3, and the control level is further increased by one step. At this time, since the level becomes 2, both the solenoid valves SV1 and SV2 are turned on in steps ST9 and ST10.
Then, the exhaust ports 8a and 8b are opened to further reduce the load on the electric motor 1. Load control start current value A1 or A1 '
If not, it is determined in step ST4 whether the drive current is equal to or greater than the load control release current value A2 or A2 '.

As a result of opening the solenoid valve to reduce the load on the electric motor, the load control release current reduces the discharge rate, but when a plurality of terminals are operating continuously, the pressure in the tank 7 is reduced. Since the load suddenly drops and the load on the electric motor 1 is greatly reduced, the electric motor 1 is in an easy operation state and the number of revolutions is rapidly increased, resulting in a drastically reduced drive current.

When the drive current is the load control release current value A2 or A
If it is 2 'or less, there is no use in performing the compression operation with the load reduced, so the process proceeds to step ST5 to lower the control level by one stage, close one open solenoid valve, and reduce the discharge pressure. To raise. When the compression operation is performed at the control level 1 and the driving current is the load control start current value A2 (point c) or A2 ′
When it has dropped to (point c '), the solenoid valves SV1 and SV2 are closed in step ST11 to perform the compression operation at the control level 0. If the compression operation is performed at the control level 2 and the driving current is the load control start current value A2 (point d) or A2 ′ (d ′).
(Point), the solenoid valve SV1 is opened in steps ST7 and ST8, the solenoid valve SV2 is closed, and the compression operation is performed at the control level 1.

When the drive current is the load control release current value A2 or A
If it is 2 'or more, the flow returns to step ST1 without changing the control level, and it is determined whether the pressure in the tank 7 has reached the maximum pressure.
In step 2, the drive current is monitored again. When the internal pressure of the tank 7 has reached the maximum pressure (PMAX), the pressure switch PS is turned off.
F, the drive circuit is opened, the electric motor 1 stops, the pressure in the tank 7 decreases, and the pressure switch PS returns (O
N) to wait in step ST1 until the pressure switch P
When S returns (ON), the electric motor 1 starts rotating and restarts the compression operation. As described above, the load control start current value can be changed according to the power supply capacity by previously confirming the power supply capacity (breaker capacity) and operating the switch 15 in accordance with the power supply capacity. The control according to the capacity can be performed. As a result, it is possible to avoid the occurrence of troubles such as the breaker being operated during the operation of the two-stage compressor and the supply of electric power being stopped, so that the work is not interrupted and the operation efficiency is reduced. As a result, the operation is not stopped during the demonstration at the exhibition or the like, and the sales promotion activities are not hindered.

As shown by the pressure / discharge amount characteristic curve in FIG. 4, when the power supply capacity is small, the breaker does not operate even if the discharge amount slightly decreases. Can be increased, and efficient operation can be performed according to the power supply capacity.

Even when the capacity of the breaker is large, when a plurality of devices such as other electric tools and lighting equipment are supplied with electric power from the same breaker, or when the breaker is located far away, the voltage drops due to line loss. If the load becomes large, the load on the two-stage compressor increases and the drive current of the electric motor rises, so that the breaker becomes easy to operate, and all equipment connected to this breaker may stop. Therefore, a trouble can be prevented beforehand by operating a switch which is an input means of power capacity information in consideration of a load state of the breaker, a distance from the breaker, and the like.

[0024]

According to the present invention, the capacity of the power supply (capacity of the breaker) is confirmed in advance, and the information relating to the capacity of the power supply is input to the control unit by the input means, so that the load control start current corresponding to the power supply capacity is obtained. Since the setting of the value can be changed, the control operation of the two-stage compressor according to the power supply capacity can be performed. As a result, it is possible to avoid the trouble that the breaker operates during operation and the two-stage compressor stops and the work is interrupted, and the operation does not stop during demonstrations at exhibitions etc. There will be no hindrance.

Further, when there is a margin in the power supply capacity, the discharge amount of the compressed gas can be increased, and an efficient operation corresponding to the power supply capacity can be performed without operating the breaker.

[Brief description of the drawings]

FIG. 1 is a perspective view of a two-stage compressor according to the present invention.

FIG. 2 is a block diagram showing a configuration of the two-stage compressor.

FIG. 3 is a flowchart illustrating operation control of the two-stage compressor.

FIG. 4 is a characteristic curve diagram showing a relationship between a pressure, a drive current, and a pressure and a discharge amount.

[Explanation of symbols]

 Reference Signs List 1 electric motor 2 compression chamber 3 compression chamber 6a connecting pipe 7 compressed gas storage tank 8a, 8b exhaust port 10 control unit 14 terminal 15 input means (switch) SV1, SV2 solenoid valve

Claims (1)

[Claims] A piston operated by a common power supply motor
A two-stage compression chamber for compressing and discharging the intake air by the cylinder mechanism is provided, and the discharge port side of the front-stage compression chamber and the intake port side of the rear-stage compression chamber are connected to each other by a connecting pipe, and arranged.
In a two-stage compressor that connects a discharge port of a compression chamber in a subsequent stage to a compressed gas storage tank and supplies compressed air to a terminal such as a pneumatic nailing machine connected to the compressed gas storage tank, at least the connecting pipe has Two exhaust ports are formed, and each exhaust port is provided with an electromagnetic valve. When the drive current of the electric motor reaches a load control start current value, the electromagnetic valve is controlled to reduce the load on the electric motor. An operation control mechanism corresponding to the power supply capacity in the two-stage compressor, comprising: a control unit that changes the setting of the load control start current value based on the power supply capacity information input by the input means.