Air Compressor

Abstract

To solve a problem that, in an air compressor for supplying compressed air to an air tool such as a compressed-air drive type nailing tool as a power source, a compression mechanism is stopped once when the inner pressure of a storage tank reaches set pressure, therefore, in a prior art, a small-diameter hole for releasing residual pressure is formed at a cylinder in order to reduce a load at reactivation, however, compression efficiency is lowered accordingly, and the small-diameter hole is liable to be clogged by dust or the like, and in this disclosure, to provide an unload mechanism which does not allow such a problem to occur.SOLUTION: A spool valve 31 which is released by a solenoid actuator 40 is arranged in place of a conventional small-diameter hole. By transmitting a drive force of the solenoid actuator to the spool valve by an action of a lever of a transmission member, the solenoid actuator is reduced in a size and a cost. High residual pressure at a level of 4.5 MPa can be released by using the small-sized solenoid actuator.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to an air compressor that supplies compressed air to pneumatic tools, such as compressed air-powered nail guns and air dusters. [Background technology]

[0002] Patent Document 1 discloses technology related to an air compressor. The air compressor includes a compression mechanism that generates compressed air. The compression mechanism operates using an electric motor as a drive source. The compression mechanism is configured to convert the rotational output of the electric motor to reciprocate a piston in a cylinder and discharge compressed air (reciprocating type). The compressed air discharged from the compression mechanism is stored in a tank. The compressed air stored in the tank is supplied to an air tool.

[0003] When the storage pressure in the tank reaches a set pressure and the compression mechanism stops, compressed air (residual pressure) remains in the cylinder depending on the stopping position of the piston. This residual pressure becomes a load when restarting. For example, when handling high pressures of about 4.5 MPa, the residual pressure becomes large, and high loads at restart become a problem. Patent Document 1 discloses a technology that avoids high loads at motor startup by providing a small diameter hole in the cylinder for bleeding air. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6007570 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is a problem that the compression efficiency is reduced due to the small diameter hole for air bleeding provided to avoid high load at the time of starting the motor. In addition, there is a risk that the small diameter hole will become clogged with dust, reducing the air bleeding efficiency. The present disclosure aims to reliably avoid high load at the time of starting the motor without causing problems such as reduced compression efficiency and clogging of the small diameter hole. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, an air compressor includes a compression mechanism that compresses air in a cylinder by, for example, reciprocating a piston, and a tank that is connected to the cylinder and stores the compressed air. For example, when the internal pressure of the tank reaches a predetermined pressure, the operation of the compression mechanism is stopped by a stop mechanism. For example, a spool valve that is connected to the cylinder and can open and close the cylinder to the atmosphere is provided. For example, when the stop mechanism stops the compression mechanism, the spool valve moves in an opening direction by a solenoid actuator.

[0007] Therefore, when the compression mechanism stops, the spool valve is opened and the cylinder is opened to the atmosphere. This releases the residual pressure in the cylinder to the atmosphere, reducing the load when the compression mechanism is restarted. The reduced load when restarting reduces the vibration of the entire compressor. The spool valve is reliably opened in the opening direction by the operation of the solenoid actuator. Since it is not configured to remove residual pressure using a conventional small diameter hole, there is no decrease in compression efficiency. In addition, there is no problem such as clogging of the small diameter hole. The spool valve may be provided directly in parallel with the cylinder, or may be provided in parallel with the air chamber downstream of the cylinder. In either case, the spool valve is opened and the compression chamber of the cylinder is directly or indirectly opened to the atmosphere to remove residual pressure. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is an overall perspective view of an air compressor. [Diagram 2] FIG. 2 is an overall perspective view of the compressor with the main body cover removed to expose the compression mechanism. [Diagram 3]FIG. 2 is a cross-sectional view of the compression mechanism. [Figure 4] 4 is a cross-sectional view taken along line IV-IV in FIG. 3, and is a vertical cross-sectional view of the second check valve. [Diagram 5] 1 is a cross-sectional view of the unloading mechanism, the view showing the unactivated state. [Figure 6] FIG. 6 is an enlarged view of part VI in FIG. [Figure 7] This is a cross-sectional view of the unloading mechanism, showing the state in which it is operated to the opening side. [Figure 8] FIG. 8 is an enlarged view of part VIII in FIG. [Figure 9] FIG. 4 is a control block diagram of an unloading mechanism. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In one or more embodiments, for example, a transmission member may be provided between the spool valve and the solenoid actuator to transmit the driving force of the solenoid actuator to the spool valve. Therefore, the spool valve can be disposed away from the solenoid actuator. This increases the degree of freedom in the arrangement of the spool valve and the solenoid actuator.

[0010] In one or more embodiments, for example, the transmission member may be rotatably supported via a pivot shaft such that the transmission member rotates about the pivot shaft to transmit the driving force of the solenoid actuator to the spool valve.

[0011] In one or more embodiments, for example, the rotating support shaft is provided between the spool valve and the solenoid actuator. The transmission member may have a first transmission part extending from the rotating support shaft to the solenoid actuator and a second transmission part extending from the rotating support shaft to the spool valve, and the first transmission part may be longer than the second transmission part. Thus, the driving force of the solenoid actuator is amplified by the transmission member and transmitted to the spool valve. By adding a lever effect to the transmission member, the solenoid actuator can be made smaller and less expensive.

[0012] In one or more embodiments, for example, an air passage communicating between the cylinder and the tank and a check valve provided in the air passage to prevent backflow of air from the tank toward the cylinder may be provided. A spool valve between the check valve and the cylinder may open the air passage to the atmosphere. Thus, the residual pressure in the cylinder is efficiently released to the atmosphere by the spool valve. The check valve prevents the compressed air on the tank side from being released by the spool valve.

[0013] In one or more embodiments, for example, when the piston moves in an upward direction for compression, the solenoid actuator may be located below the bottom end of the piston, and thus the solenoid actuator is located away from the heat generating portion due to compression, thereby preventing malfunction of the solenoid actuator and increasing its durability.

[0014] In one or more embodiments, for example, the spool valve may be configured to have a spring biasing the spool valve in a closing direction, such that when the actuation force of the solenoid actuator is removed, the spool valve is forced closed by the bias of the spring.

[0015] In one or more embodiments, for example, a configuration may be adopted in which high-pressure air of at least 3 MPa or more is generated by a compression mechanism, and the high-pressure compressed air of 3 MPa or more is opened and closed by a spool valve.

[0016] In one or more embodiments, for example, the compression mechanism has a first cylinder on the upstream side and a second cylinder on the downstream side. It has a two-stage compression structure in which air compressed in the first cylinder is further compressed in the second cylinder. For example, the cylinder can be a second cylinder. Thus, the compressed air compressed to high pressure in two stages is released to the atmosphere by a spool valve, and the residual pressure in the first and second cylinders is efficiently removed.

[0017] In one or more embodiments, for example, the spool valve may have a first O-ring and a second O-ring that hermetically seal the air flowing in from the cylinder against the atmosphere. The difference in the pressure-receiving diameter between the first O-ring and the second O-ring may be set to, for example, within 0.5 mm. Thus, the residual pressure in the cylinder acts on one O-ring as an external force that moves the spool valve in the opening direction, and acts on the other O-ring as an external force that moves the spool valve in the closing direction. By setting the difference in the pressure-receiving diameter between the first O-ring and the second O-ring small, for example, within 0.5 mm, the effect of the residual pressure in the cylinder acting on the first O-ring and the second O-ring is offset. This allows the solenoid actuator to be made smaller and less expensive. EXAMPLES

[0018] As shown in Figures 1 and 2, an air compressor 1 has two cylindrical tanks 2 that are long from front to back. The generated compressed air is stored in the two tanks 2. A total of four legs 3 are provided in front and behind the two tanks 2. Each leg 3 is made of a rubber material with high vibration resistance. Side protectors 3a are provided in parallel on each leg 3. A drain cock 2a for draining water is provided between the front parts of the two tanks 2. The upper parts of the two tanks 2 are connected to each other by a base part 4. Handle parts 5 for carrying are provided at the front and rear of the base part 4. A compression mechanism 10 and a drive part 20 are mounted on the upper surface of the base part 4. Figure 1 shows the compression mechanism 10 and the drive part 20 covered by the main body cover 6.

[0019] On the front surface of the main body cover 6, two high pressure outlets 7 and two low pressure outlets 8 are arranged on the left and right sides. Compressed air of, for example, 2.5 MPa is supplied from the high pressure outlet 7. Compressed air of, for example, 1 MPa is supplied from the low pressure outlet 8. Adjustment dials 7a and 8a for setting the discharge pressure are provided above the outlets 7 and 8, respectively.

[0020] An operation unit 9 is provided on the front upper surface of the main body cover 6. The operation unit 9 has a power switch 9a, a tank internal pressure change button 9b, an operation mode change button 9c, as well as a discharge pressure display unit, a tank internal pressure display unit, etc., all concentrated in one place.

[0021] When the main body cover 6 is removed as shown in Fig. 2, the compression mechanism 10 is exposed. As shown in Fig. 3, the compression mechanism 10 has a first compression section 11 on the front side and a second compression section 12 on the rear side. High-pressure compressed air is generated by the two-stage compression sections 11, 12, front and rear. Air is introduced by the first compression section 11 on the front side to generate compressed air at a constant pressure. The compressed air compressed and generated by the first compression section 11 on the front side is supplied to the second compression section 12 on the rear side. The supplied compressed air is further compressed by the second compression section 12 to generate compressed air at a higher pressure (for example, 4.5 MPa).

[0022] A drive unit 20 is disposed between the first compression unit 11 and the second compression unit 12. The drive unit 20 has a cylindrical drive unit case 21. The drive unit case 21 is fixed onto the base unit 4. An electric motor 22 is supported on the right side of the drive unit case 21. A brushless motor capable of obtaining a relatively large starting torque is used for the electric motor 22. The electric motor 22 has a ring-shaped rotor 22a and a similarly ring-shaped stator 22b located on the inner periphery side of the rotor 22a. The stator 22b is fixed to the right side of the drive unit case 21. An output shaft 22c is coupled to the center of the rotor 22a. The output shaft 22c is inserted into the center of the stator 22b. A cooling fan 23 is coupled to the right end of the output shaft 22c.

[0023] A drive shaft 25 is coaxially coupled to the left end of the output shaft 22c. The drive shaft 25 is rotatably supported between the right and left sides of the drive unit case 21 via a right bearing 25a and a left bearing 25b. The inside of the drive unit case 21 is connected to the atmosphere. A first compression section 11 is provided at the front of the drive unit case 21, and a second compression section 12 is provided at the rear.

[0024] The first compression section 11 has a first cylinder 11a and a first piston 11b. The first cylinder 11a extends forward from the front of the drive section case 21. The first piston 11b is accommodated in the first cylinder 11a so as to be airtight movable back and forth. The first piston 11b is connected to a first crank portion 26 of the drive shaft 25 via a first rod 11c.

[0025] The second compression section 12 has a second cylinder 12a and a second piston 12b. The second cylinder 12a extends rearward from the rear of the drive section case 21. The second piston 12b is accommodated in the second cylinder 12a so as to be airtight movable back and forth. The second piston 12b is connected to a second crank portion 27 of the drive shaft 25 via a second rod 12c.

[0026] The first crank portion 26 and the second crank portion 27 are eccentric in the same direction at the same position around the axis of the drive shaft 25. Therefore, one rotation of the drive shaft 25 simultaneously performs a compression stroke of one of the first compression section 11 and the second compression section 12 and an intake stroke of the other. In the compression stroke in which the first piston 11b moves forward in the first compression section 11, the second piston 12b moves forward in the second compression section 12 to perform an intake stroke. In the intake stroke in which the first piston 11b moves rearward in the first compression section 11, the second piston 12b moves rearward in the second compression section 12 to perform a compression stroke.

[0027] The first compression chamber 11d of the first cylinder 11a and the second compression chamber 12d of the second cylinder 12a are communicated via a supply pipe 13. The upstream side of the supply pipe 13 is connected to the first compression chamber 11d via an auxiliary check valve 11e. The auxiliary check valve 11e prevents compressed air from flowing back from the supply pipe 13 to the first compression chamber 11d. The downstream side of the supply pipe 13 is connected to the second compression chamber 12d. The compressed air that flows from the first compression chamber 11d through the auxiliary check valve 11e and into the supply pipe 13 is supplied directly to the second compression chamber 12d.

[0028] In this way, by starting the electric motor 22, compressed air is generated in two stages, in the first compression section 11 and the second compression section 12. The compressed air supplied to the second compression chamber 12d of the second compression section 12 is compressed to a higher pressure as the second piston 12b moves backward. The compressed air generated in the second compression chamber 12d at a high pressure, for example, of about 4.5 MPa, flows into the air passage 15 leading to the tank 2 via the first check valve 14. The first check valve 14 prevents the compressed air that has flowed into the air passage 15 from flowing back into the second compression chamber 12d.

[0029] 4, the downstream side of the air passage 15 is connected to the left and right tanks 2. The downstream side of the air passage 15 is connected to the insides of the left and right tanks 2 via a second check valve 16. The second check valve 16 prevents the compressed air stored in the tank 2 from flowing back into the air passage 15.

[0030] An intermediate chamber 15a is provided on the upstream side of the air passage 15. An unloading mechanism 30 is provided in parallel with the intermediate chamber 15a. The unloading mechanism 30 has a function of releasing the compressed air (residual pressure) in the second compression chamber 12d to the atmosphere when the compression mechanism 10 is stopped. Details of the unloading mechanism 30 are shown in Figs. 5 and 6. The unloading mechanism 30 has a spool valve 31 and a solenoid actuator 40 that operates the spool valve 31 to the opening side. The spool valve 31 has a cylindrical spool body 32 and a cylindrical frame portion 33 that holds the spool body 32. The frame portion 33 is disposed in a horizontally laid position with the inner circumferential side open to the left and right. The spool body 32 is supported on the inner circumferential side of the frame portion 33 so as to be displaceable to the left and right.

[0031] Two O-rings 34, 35 are attached to the spool body 32. Between the two O-rings 34, 35, the inner peripheral hole 33b of the frame body portion 33 is in communication with the intermediate chamber 15a via the vent hole 18. A set screw 36 is fastened to the right end portion of the frame body portion 33. A compression spring 37 is interposed between the set screw 36 and the spool body 32, and the spool body 32 is biased to the left (closing side) by the biasing force of the compression spring 37.

[0032] A stopper flange portion 32a is provided on the right end portion of the spool body 32. The stopper flange portion 32a abuts against a step portion 33a of the frame portion 33, thereby restricting the movement end position on the closing side of the spool body 32. The position where the stopper flange portion 32a abuts against the step portion 33a corresponds to the closed position of the spool body 32. Figures 5 and 6 show a state in which the spool body 32 is held in the closed position and the spool valve 31 is closed.

[0033] Between the stopper flange portion 32a of the spool body 32 and the set screw 36, the frame body portion 33 is provided with one open hole 38. When the spool body 32 is in the closed position, the right-side first O-ring 34 is in sliding contact with the inner peripheral hole 33b of the frame body portion 33. Therefore, the right and left sides of the first O-ring 34 are airtightly blocked. In this state, the air hole 18 is airtightly blocked from the open hole 38 (the spool valve 31 is in a closed state).

[0034] 7 and 8, when the spool body 32 is displaced to the right against the compression spring 37, the spool valve 31 is opened. When the spool body 32 is displaced to the right, the first O-ring 34 is released from the inner peripheral hole 33b of the frame body portion 33. As a result, the right and left sides of the first O-ring 34 are in communication with each other. In this state, the vent hole 18 is in communication with the release hole 38. Therefore, when the spool valve 31 is opened, the compressed air in the air passage 15 including the intermediate chamber 15a is released to the atmosphere through the release hole 38. As a result, the residual pressure in the second compression chamber 12d is released to the atmosphere through the intermediate chamber 15a.

[0035] The first O-ring 34 on the right opens and closes the gap between the vent hole 18 and the open hole 38. The second O-ring 35 on the left is constantly in sliding contact with the inner circumferential hole 33b of the frame body portion 33, so that the vent hole 18 is constantly airtightly blocked from the atmosphere. Between the first O-ring 34 and the second O-ring 35, the air pressure of the second compression chamber 12d constantly acts on the inner circumferential hole 33b via the vent hole 18.

[0036] The first O-ring 34 is restricted from shifting leftward in the axial direction by the first shaft portion 32b provided on its left side. The first shaft portion 32b has a larger diameter than the second shaft portion 32c to which the second O-ring 35 is attached. Air pressure acting on the left surface of the first O-ring 34 acts as an external force that moves the spool body 32 to the right (opening side). Air pressure acting on the right surface of the second O-ring 35 acts as an external force that moves the spool body 32 to the left (closing side).

[0037] In this embodiment, the pressure-receiving diameter (outer diameter in the installed state) d1 of the first O-ring 34 is larger than the pressure-receiving diameter (outer diameter in the installed state) d2 of the second O-ring 35. In this embodiment, the pressure-receiving diameter d1 of the first O-ring 34 is set to a diameter difference of 0.5 mm or less with respect to the pressure-receiving diameter d2 of the second O-ring 35. As a result, the influence of the air pressure received by the first O-ring 34, which has a larger pressure-receiving diameter than the second O-ring 35, is suppressed to, for example, about 2 N. As a result, the biasing force of the compression spring 37 required to move the spool body 32 to the closing side can be smaller, for example, about 3 N. As a result, the compression spring 37 can be made smaller.

[0038] The reduction in size of the compression spring 37 reduces the biasing force that moves the spool body 32 to the closing side, so that a smaller driving force is sufficient to move the spool body 32 to the opening side, and therefore the solenoid actuator 40, which will be described below, can be made smaller.

[0039] The left end side of the spool body 32 protrudes leftward from the frame portion 33. The spool valve 31 operates to open by the driving force of the solenoid actuator 40. The spool valve 31 is arranged in parallel to the rear side of the intermediate chamber 15a. The solenoid actuator 40 is arranged on the left side of the second compression section 12. The solenoid actuator 40 is arranged forward of the stroke range of the second piston 12b in the front-rear direction. When the movement direction of the second piston 12b for compression is upward (rear in this embodiment), the solenoid actuator 40 is arranged below (forward in this embodiment) the downward end position (advance end position in this embodiment) of the second piston 12b. In this way, the solenoid actuator 40 is arranged at a position away from the heat generating portion (second compression chamber 12d) due to compression. This increases the durability of the solenoid actuator 40.

[0040] The driving force of the solenoid actuator 40 is transmitted to the spool valve 31 via a long transmission member 41. A support part 42 is provided at the rear end of the second cylinder 12a. The support part 42 is provided in a state in which it protrudes to the left side. The transmission member 41 is supported at the left end of the support part 42 via a rotation support shaft 43. The transmission member 41 is supported so as to be rotatable left and right via the rotation support shaft 43 near the center in the longitudinal direction.

[0041] The transmission member 41 has a first transmission part 41a on the front side of the rotation support shaft 43 and a second transmission part 41b on the rear side of the rotation support shaft 43. The front part of the first transmission part 41a is in contact with the operating part 40a of the solenoid actuator 40. The rear part of the second transmission part 41b is in contact with the left end part of the spool body 32. As shown in Figs. 5 and 7, the position of the rotation support shaft 43 is appropriately set with respect to the longitudinal position of the transmission member 41 so that the length L1 of the first transmission part 41a is longer than the length L2 of the second transmission part 41b. The rotation support shaft 43 is disposed shifted rearward from the longitudinal center of the transmission member 41. Therefore, the driving force of the solenoid actuator 40 (the thrust force of the operating part 40a) is amplified by the lever action of the transmission member 41 and transmitted to the spool body 32 as an external force in the opening direction.

[0042] The driving force of the solenoid actuator 40 is transmitted to the spool body 32 by the lever action of the transmission member 41, thereby making it possible to reduce the size and cost of the solenoid actuator 40. The smaller, lower-cost solenoid actuator 40 can achieve unloading of high-pressure air of, for example, about 4.5 MPa.

[0043] The solenoid actuator 40 uses a solenoid actuator in which the operating part 40a is protruded by de-energizing and retracted by energizing. When the operating part 40a of the solenoid actuator 40 is protruded by de-energizing as shown in Figs. 7 and 8, the transmission member 41 rotates in the clockwise direction around the rotation support shaft 43. This causes the spool body 32 to be pushed rightward by the second transmission part 41b. When the spool body 32 is pushed rightward against the compression spring 37, the first O-ring 34 separates from the inner peripheral surface of the frame part 33. This causes the intermediate chamber 15a to be opened to the atmosphere through the ventilation hole 18 and the release hole 38. Thus, the residual pressure in the second compression chamber 12d is removed.

[0044] 5 and 6, when the solenoid actuator 40 is energized and the operating part 40a is pulled in, the second transmission part 41b of the transmission member 41 is pushed leftward by the biasing force of the compression spring 37 of the spool valve 31, causing the transmission member 41 to rotate counterclockwise around the rotation support shaft 43. Also, the spool body 32 moves leftward by the biasing force of the compression spring 37. The spool body 32 moves leftward and the first O-ring 34 is pressed against the inner circumferential surface of the frame part 33. This airtightly blocks the gap between the vent hole 18 and the open hole 38, blocking the intermediate chamber 15a from the atmosphere.

[0045] The unloading mechanism 30 for releasing the residual pressure in the second compression chamber 12d is operated in conjunction with a stopping mechanism 50 for stopping the compression mechanism 10. As shown in FIG. 9, the operation control of the unloading mechanism 30 is incorporated into the control of the stopping mechanism 50. The stopping mechanism 50 has a pressure sensor 51 for detecting the internal pressure of the tank 2. When the internal pressure of the tank 2 reaches a predetermined pressure (for example, 4.5 MPa), this is detected by the pressure sensor 51. A detection signal of the pressure sensor 51 is input to a control circuit 52. As a result, the power circuit is cut off and the electric motor 22 is stopped, thereby stopping the compression mechanism 10.

[0046] When the compression mechanism 10 is stopped by stopping the electric motor 22, the unload mechanism 30 is started by the control circuit 52. First, the power supply circuit is cut off from the solenoid actuator 40. This causes the operating part 40a to protrude. As shown in Figs. 7 and 8, when the operating part 40a of the solenoid actuator 40 is protruded, the transmission member 41 rotates in the illustrated clockwise direction around the rotation support shaft 43. This causes the spool body 32 to be pushed rightward against the compression spring 37, and the spool valve 31 is opened. When the spool valve 31 is opened, the intermediate chamber 15a is opened to the atmosphere through the ventilation hole 18 and the release hole 38, and the residual pressure in the second compression chamber 12d is removed. When the residual pressure in the second compression chamber 12d is removed, the residual pressure in the first compression chamber 11d is also removed through the second compression chamber 12d.

[0047] When the air pressure in the tank 2 drops to a predetermined set pressure due to consumption of the compressed air in the tank 2, this is detected by the pressure sensor 51. In response to a detection signal from the pressure sensor 51, the control circuit 52 outputs a power supply signal to the electric motor 22. This starts the electric motor 22 and restarts the compression mechanism 10. When the compression mechanism 10 is stopped, the residual pressure in the first compression chamber 11d and the second compression chamber 12d is removed by the unloading mechanism 30, thereby reducing the load on the compression mechanism 10 when it is restarted. The reduced load reduces vibration of the air compressor 1.

[0048] The compression mechanism 10 is restarted by energizing the electric motor 22. After the compression mechanism 10 is restarted, the solenoid actuator 40 is energized at a timing when the rotation state of the electric motor 22 becomes stable. This stops the unloading mechanism 30. The solenoid actuator 40 is energized to retract the operating portion 40a, so that the transmission member 41 is rotatable toward the unloading stop side (counterclockwise direction in Figs. 7 and 8). The transmission member 41 is pushed by the spool body 32 moving leftward (airflow blocking side) by the biasing force of the compression spring 37, so that the transmission member 41 rotates counterclockwise around the rotation support shaft 43. As shown in Figs. 6 and 7, the spool body 32 moves leftward toward the blocking side by the biasing force of the compression spring 37, and the first O-ring 34 is brought into sliding contact with the inner peripheral hole 33b of the frame body portion 33, so that the air vent 18 is airtightly blocked from the open hole 38. This causes the intermediate chamber 15a and the air passage 15 to be airtightly blocked from the spool valve 31. Therefore, the compressed air generated in the second compression chamber 12d of the compression mechanism 10 flows into the tank 2 through the first check valve 14, the air passage 15, and the second check valve 16.

[0049] According to the air compressor 1 described above, when the compression mechanism 10 is stopped by the stop mechanism 50, the spool valve 31 of the unloading mechanism 30 is opened to release the second compression chamber 12d of the second cylinder 12a to the atmosphere. This releases the residual pressure in the second cylinder 12a to the atmosphere. In addition, the residual pressure in the first cylinder 11a is also released to the atmosphere via the second cylinder 12a. By removing the residual pressure in the first compression section 11 and the second compression section 12 in this manner, the load when the compression mechanism 10 is restarted is reduced. In this manner, since the second compression chamber 12d is opened to the atmosphere by the spool valve 31 when the compression mechanism 10 is stopped, problems such as reduced compression efficiency and clogging of the small diameter hole, which occur when residual pressure is removed by a conventional small diameter hole, are eliminated.

[0050] The spool valve 31 is opened by the operation of the solenoid actuator 40. A long transmission member 41 is interposed between the spool valve 31 and the solenoid actuator 40. The driving force of the solenoid actuator 40 is transmitted to the spool valve 31 via the transmission member 41. Therefore, the spool valve 31 can be disposed away from the solenoid actuator 40. This increases the degree of freedom in the arrangement of the spool valve 31 and the solenoid actuator 40.

[0051] The driving force of the solenoid actuator 40 is amplified by the lever action of the transmission member 41 and transmitted to the spool valve 31. This makes it possible to reduce the size and cost of the solenoid actuator 40. Even a small, low-cost solenoid actuator 40 has sufficient driving force to operate the spool valve 31, which opens and closes high-pressure air of approximately 4.5 MPa.

[0052] The intermediate chamber 15a partitioned by the first check valve 14 of the second compression section 12 and the second check valve 16 on the tank 2 side is opened to the atmosphere by the spool valve 31. As a result, the residual pressure in the second compression chamber 12d is quickly and efficiently released to the atmosphere by the spool valve 31.

[0053] The solenoid actuator 40 is disposed at a position spaced forward from the second compression chamber 12d. The second piston 12b moves backward during the compression stroke and moves forward during the intake stroke. The solenoid actuator 40 is disposed forward of the movement end (front end position) of the second piston 12b during the intake stroke. In this manner, the solenoid actuator 40 is disposed at a position sufficiently spaced away from the heat generating portion (second compression chamber 12d) due to compression, thereby increasing the durability of the solenoid actuator 40.

[0054] Various modifications can be made to the embodiment described above. For example, the spool valve 31 may be arranged in parallel with the intermediate chamber 15a downstream of the second compression section 12 as illustrated, or may be arranged directly in parallel with the second cylinder 12a. In this case, the second compression chamber 12d is opened to the atmosphere by the spool valve through an air hole provided in the second cylinder 12a, thereby removing residual pressure.

[0055] Although an example has been given of a configuration in which the compression mechanism 10 is stopped by the stop mechanism 50 when the air pressure in the tank 2 reaches 4.5 MPa, the predetermined pressure (set stop pressure) of the tank 2 at which the stop mechanism 50 stops the compression mechanism 10 can be changed and set arbitrarily, for example, to 3 MPa or more.

[0056] Although the compression mechanism 10 that compresses and generates the compressed material in two stages, the first compression section 11 and the second compression section 12, the unloading mechanism 30 illustrated above can also be applied to a compression mechanism having a single compression section.

[0057] The solenoid actuator 40 may be a solenoid actuator in which the operating part 40a is retracted when the current is cut off and protruded when the current is applied. Alternatively, a self-retaining solenoid actuator may be used in which the position of the operating part is held in both directions by magnetic force. In this case, the front end of the transmission member and the operating part of the solenoid actuator may be rotatably connected to each other, and the rear end of the transmission member and the left end of the spool body 32 may be rotatably connected to each other, so that the spool valve 31 is opened and closed by the moving operation of the operating part of the solenoid actuator in both directions. This makes it possible to omit the compression spring 37 of the spool valve.

[0058] The power source of the air compressor 1 may be a commercial 100V AC power source, or may be, for example, a rechargeable battery pack. The illustrated unloading mechanism 30 can be applied to both AC and DC powered air compressors.

[0059] The air compressor 1 of the embodiment is an example of an air compressor in one aspect of the present disclosure. The first cylinder 11a and the second cylinder 12a of the embodiment are an example of a cylinder in one aspect of the present disclosure. The first piston 11b and the second piston 12b of the embodiment are an example of a piston in one aspect of the present disclosure. The compression mechanism 10 of the embodiment is an example of a compression mechanism in one aspect of the present disclosure.

[0060] The tank 2 of the embodiment is an example of a tank according to an aspect of the present disclosure. The stop mechanism 50 of the embodiment is an example of a stop mechanism according to an aspect of the present disclosure. The spool valve 31 of the embodiment is an example of a spool valve according to an aspect of the present disclosure. The solenoid actuator 40 of the embodiment is an example of a solenoid actuator according to an aspect of the present disclosure. [Explanation of symbols]

[0061] 1. Air compressor 2. Tank 3...legs 3a…Side protector 4…Base 5…Handle section 6…Main unit cover 7…Discharge port (for high pressure) 8...Discharge port (for low pressure) 9...Operation unit 9a...Power switch, 9b...Tank pressure change button, 9c...Operation mode change button 10...Compression mechanism 11...First compression section 11a...first cylinder, 11b...first piston, 11c...first rod, 11d...first compression chamber 11e…Auxiliary check valve 12...Second compression section 12a... second cylinder, 12b... second piston, 12c... second rod, 12d... second compression chamber 13...Supply pipe 14…First check valve 15…Air passage 15a...middle room 16...Second check valve 18…Ventilation hole 20...Drive unit 21...Drive unit case 22...Electric motor 22a...rotor, 22b...stator, 22c...output shaft 23…Cooling fan 25…Drive shaft 25a, 25b...Bearings 26…First crank section 27…Second crank section 30...Unloading mechanism 31...Spool valve 32…Spool body 32a... stopper flange portion, 32b... first shaft portion, 32c... second shaft portion 33...Frame part 33a: step portion, 33b: inner peripheral hole 34…First O-ring 35…Second O-ring d1: pressure-receiving diameter of the first O-ring 34; d2: pressure-receiving diameter of the second O-ring 35 36…Setscrew 37…Compression spring 38...Open hole 40...Solenoid actuator 40a...Operating part 41...Transmission member 41a...first transmission section, 41b...second transmission section 42...Support part 43...Rotating shaft 50…stopping mechanism 51...Pressure sensor 52...Control circuit

Claims

1. An air compressor, A compression mechanism that compresses air in a cylinder by reciprocating a piston; a tank communicating with the cylinder and storing compressed air; a stop mechanism that stops driving the compression mechanism when the internal pressure of the tank reaches a predetermined pressure; a spool valve connected to the cylinder and capable of opening and closing the cylinder to the atmosphere; a solenoid actuator that moves the spool valve in an opening direction when the stop mechanism stops the compression mechanism; an air compressor having a transmission member rotatably supported between the spool valve and the solenoid actuator via a rotary support shaft, the transmission member transmitting the driving force of the solenoid actuator to the spool valve;

2. 2. The air compressor of claim 1, the rotary support shaft is provided between the spool valve and the solenoid actuator, the transmission member has a first transmission portion extending from the rotating support shaft to the solenoid actuator, and a second transmission portion extending from the rotating support shaft to the spool valve, An air compressor, wherein the first transmission portion is longer than the second transmission portion.

3. 3. An air compressor according to claim 1 or 2, an air passage communicating the cylinder with the tank; a check valve provided in the air passage to prevent a backflow of air from the tank toward the cylinder; an air compressor in which the air passage is opened to the atmosphere by the spool valve between the check valve and the cylinder;

4. An air compressor according to any one of claims 1 to 3, An air compressor in which, when the movement direction of the piston for compression is upward, the entire solenoid actuator is positioned downward and away from a compression chamber in which compressed air is produced by the piston.

5. An air compressor according to any one of claims 1 to 4, An air compressor having a spring that biases the spool valve in a closing direction.

6. An air compressor according to any one of claims 1 to 5, An air compressor in which high-pressure air of at least 3 MPa is generated by the compression mechanism.

7. An air compressor according to any one of claims 1 to 6, The compression mechanism has a first cylinder on an upstream side and a second cylinder on a downstream side, and has a two-stage compression structure in which air compressed by the first cylinder is further compressed by the second cylinder, The cylinder is the second cylinder of an air compressor.

8. An air compressor according to any one of claims 1 to 7, the spool valve is supported in an inner peripheral hole of a frame body so as to be displaceable in an axial direction via a first O-ring attached to one side of a displacement direction of the spool valve and a second O-ring attached to the other side of a vent hole through which air flows in from an air passage communicating between the cylinder and the tank, a first O-ring comes out of the inner peripheral hole due to displacement of the spool valve, opening the vent hole to the atmosphere, and the first O-ring comes into sliding contact with the inner peripheral hole, hermetically closing the vent hole against the atmosphere, while the second O-ring is constantly in sliding contact with the inner peripheral hole regardless of displacement of the spool valve; An air compressor in which the difference in pressure-receiving diameter between the first O-ring and the second O-ring is set to within 0.5 mm.

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