JP2008064115A - Reciprocating compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an impact when an unload piston collides with a valve body of a suction valve and improve durability and life of the unload piston and the suction valve.
An unload mechanism 31 includes a mounting cylinder 10 on a cylinder head 7, an unload bush 20, an unload piston 32, and the like. Further, the unload piston 32 is formed of a self-lubricating resin material from the piston main body 32A, the pressing portion 32B, the pressure receiving portion 32C, and the O-ring mounting groove 32D. And even when the unloading piston 32 slides toward the bottom side and the pressing part 32B strongly collides with the valve plate 15 of the suction valve when performing no-load operation, the impact force is alleviated and the valve plate 15 Prevents damage and reduces impact noise.
[Selection] Figure 1

Description

  The present invention relates to a reciprocating compressor suitably used as, for example, an air compressor, and more particularly to a reciprocating compressor having an unload mechanism that controls load operation and no-load operation.

  Generally, a reciprocating compressor includes a cylinder, a piston provided in the cylinder so as to be capable of reciprocating, a cylinder head mounted on the cylinder and having a suction chamber and a discharge chamber formed therein, A suction valve that is attached to the lower surface of the cylinder head and has a valve body that communicates and shuts off the suction chamber of the cylinder head with respect to the inside of the cylinder, and is provided in the cylinder head and forces the suction valve during no-load operation. And an unloading mechanism for automatically opening the valve.

  Further, the unload mechanism has a bottomed cylindrical unload cylinder in which an insertion hole communicating with the suction chamber is formed on the bottom side, and a base end side is slidably inserted into the unload cylinder. The front end side is comprised from the unload piston which protruded in the said suction chamber from the penetration hole of this unload cylinder.

  When a load operation is performed simultaneously with the start of the compressor, the suction valve is opened in the suction stroke, and the discharge valve is opened in the compression stroke, a large load is applied to a drive source such as an electric motor. For this reason, the unload mechanism forcibly opens the suction valve to perform no-load operation of the reciprocating compressor.

  Therefore, an air compressor will be described as an example of a reciprocating compressor according to the prior art and will be described with reference to FIGS.

  Reference numeral 1 denotes a cylinder formed in a substantially cylindrical shape by a metal material such as iron or aluminum. A valve seat plate 3 and a cylinder head 7 which will be described later are attached to an upper end portion 1A of the cylinder 1 by bolts (not shown). It is fixed. In addition, a step portion 2 is formed at the upper end portion 1 </ b> A of the cylinder 1 to restrict the valve opening of a suction valve 13 to be described later.

  Reference numeral 3 denotes a valve seat plate provided on the upper end portion 1A of the cylinder 1. The valve seat plate 3 is formed as a substantially rectangular flat plate, and defines a compression chamber 4 in the cylinder 1 with a piston 11 described later. It is made. The valve seat plate 3 is formed with a suction hole 5 and a discharge hole 6 so as to communicate with the compression chamber 4.

  Reference numeral 7 denotes a cylinder head mounted on the cylinder 1 with the valve seat plate 3 interposed therebetween. The cylinder head 7 is made of a metal material such as iron or aluminum. The cylinder head 7 is formed with a partition wall 7 </ b> A that defines a suction chamber 8 and a discharge chamber 9 in the cylinder head 7 with the valve seat plate 3. Further, the cylinder head 7 is formed with a suction port 7B and a discharge port (not shown). The suction port 7B communicates with the suction hole 5 through the suction chamber 8, and the discharge port passes through the discharge chamber 9. And communicated with the discharge hole 6.

  Reference numeral 10 denotes an attachment cylinder portion which is located in the suction chamber 8 of the cylinder head 7 and to which an unload mechanism 19 described later is attached. The attachment cylinder portion 10 is formed integrally with a bottomed cylinder, and the attachment cylinder portion An insertion hole 10 </ b> A that is located above the suction hole 5 and communicates with the suction chamber 8 is drilled on the bottom side of 10. The mounting cylinder portion 10 may be formed by a member separate from the cylinder head 7 and fixed to the cylinder head 7 by means such as screwing or welding.

  A piston 11 is slidably inserted into the cylinder 1 and is connected to a crankshaft (not shown) using a connecting rod 12, and the crankshaft is rotated by a drive source such as an electric motor. As a result, the cylinder 1 reciprocates.

  Reference numeral 13 denotes a suction valve attached to the lower surface side (compression chamber 4 side) of the valve seat plate 3 so as to open and close the suction hole 5. The suction valve 13 has a bolt 14 or the like on the base end side and the lower surface of the valve seat plate 3 The valve plate 15 is fixed to the front end and has a free end on the front end side. The valve plate 15 is formed of a thin plate having a spring property.

  A discharge valve 16 is attached to the upper surface side (discharge chamber 9 side) of the valve seat plate 3 so as to open and close the discharge hole 6. The discharge valve 16 is fixed to the valve seat plate 3 with a bolt 17 or the like at the base end side. The valve plate 18 is a free end at the front end side and extends to the periphery of the discharge hole 6.

  Reference numeral 19 denotes an unload mechanism positioned above the suction hole 5 and attached to the mounting cylinder portion 10 of the cylinder head 7. The unload mechanism 19 includes an unload bush 20, an unload piston 21 and a holding spring, which will be described later. 25, etc., and at the time of operation, the pressing portion 21B of the unload piston 21 pushes the valve plate 15 of the suction valve 13 to forcibly hold the suction valve 13 in the open state, thereby eliminating the compressor. Load operation.

  Reference numeral 20 denotes an unload bush that covers the upper opening of the mounting cylinder portion 10. The unload bush 20 is formed on the cylinder portion 20A that forms an unload cylinder together with the mounting cylinder portion 10, and on the cylinder portion 20A. It is comprised from the cover part 20B made. In addition, a connection port 20C communicating with an air chamber 23 described later is formed at the center of the lid 20B, and an air conduit (not shown) or the like is connected to the connection port 20C.

  The air conduit is connected to an external air tank or the like with a solenoid valve (both not shown) interposed therebetween. When the inside of the air tank reaches a specified pressure, the unload mechanism 19 opens this solenoid valve, and the air pressure (compressed air) in the air tank is supplied into the air chamber 23 through the air conduit, so that no load is applied. Do the driving.

  Reference numeral 21 denotes an unload piston that pushes the valve plate 15 of the suction valve 13, and the unload piston 21 extends in the axial direction by a metal material such as brass, iron, stainless steel, for example, as shown in FIG. It is formed as a rod-shaped body. Here, the unloading piston 21 is inserted into the insertion hole 10A of the mounting cylinder portion 10 and protrudes into the suction chamber 8, and the unloading piston 21 is positioned on the distal end side of the piston main body 21A and has a small diameter extending in the axial direction. A pressing portion 21B, a pressure receiving portion 21C positioned on the proximal end side of the piston main body 21A and slidably inserted into the cylindrical portion 20A of the unload bush 20, and an O formed on the outer peripheral side of the pressure receiving portion 21C It is comprised from the ring attachment groove | channel 21D.

  The outer periphery of the unload piston 21 is covered with a lubricating film 22 made of a self-lubricating resin material, for example, a phenol resin kneaded with carbon, a tetrafluoride resin, or the like.

  Here, the pressure receiving part 21C of the unloading piston 21 defines an air chamber 23 between the cylinder part 20A and the lid part 20B. An O-ring 24 is mounted in an O-ring mounting groove 21D formed on the outer peripheral side of the pressure receiving portion 21C. Furthermore, molybdenum heat-resistant grease is attached to the O-ring 24, and the gap between the pressure receiving portion 21C and the cylindrical portion 20A is sealed with this grease.

  Reference numeral 25 denotes a holding spring for holding the unloading piston 21 at the stop side position when the unloading mechanism 19 is stopped. The holding spring 25 is disposed around the piston main body 21A, and its upper end contacts the lower surface of the pressure receiving portion 21C. The lower end side is in contact with the bottom side in the mounting cylinder portion 10.

  In the conventional air compressor configured as described above, when the crankshaft is rotationally driven by a drive source (not shown) such as an electric motor, the piston 11 reciprocates in the cylinder 1 to cause the compression chamber 4 to move. Scale.

  During the load operation of the compressor, the suction chamber 13 is opened and discharged because the compression chamber 4 has a lower pressure than the suction chamber 8 and the discharge chamber 9 in the suction stroke in which the piston 11 slides downward in the cylinder 1. When the valve 16 is closed, external air is sucked into the compression chamber 4 from the suction port 7B via the suction chamber 8.

  Further, in the discharge stroke in which the piston 11 slides upward in the cylinder 1, the compression chamber 4 has a higher pressure than the suction chamber 8 and the discharge chamber 9, so the suction valve 13 is closed and the discharge valve 16 is opened. Thus, the air compressed in the compression chamber 4 is discharged as compressed air from the discharge port via the discharge chamber 9 and stored in an external air tank or the like.

  In this case, since the electromagnetic valve is closed in the unload mechanism 19 so that the compressor is loaded, the unload piston 21 is pushed upward toward the air chamber 23 by the holding spring 25, and the piston body The pressing portion 21 </ b> B of 21 </ b> A is held in a state of being separated from the valve plate 15 of the suction valve 13. As a result, the valve plate 15 of the suction valve 13 is separated from the valve seat plate 3 and seated as the piston 11 repeats the suction stroke and the discharge stroke.

  On the other hand, when the compressor is operated with no load, air pressure is supplied from the air tank or the like into the air chamber 23 of the unload mechanism 19 by opening a solenoid valve or the like. As a result, the unloading piston 21 slides downward against the holding spring 25 as shown in FIG. 7, and the pressing portion 21B at the tip pushes the valve plate 15 of the suction valve 13 downward, and the suction The valve 13 is forcibly held open.

  By the way, in the above-described reciprocating compressor according to the prior art, the entire unload piston 21 of the unload mechanism 19 is made of a metal material, and thus has the following problems.

  First, when the entire unload piston 21 is made of a metal material, the mass thereof increases. Therefore, when the unload mechanism 19 starts a no-load operation, the pressing portion 21B of the unload piston 21 is a suction valve. It collides with 13 valve plates 15 vigorously. As a result, the impact force when the two collide increases, and there is a possibility that the pressing portion 21B of the unloading piston 21, the valve plate 15 and the like are damaged.

  Secondly, at the start of no-load operation, if the pressing portion 21B of the unloading piston 21 collides with the valve plate 15 of the suction valve 13 with a large inertial force, a collision sound between the two tends to be generated. When the unload piston 21 made of this collides with the metal valve plate 15 vigorously, the noise level tends to increase.

  Third, since the unload piston 21 is formed of a metal material, it is formed in advance with a thickness that allows for thermal expansion, and the clearance between the piston main body 21A and the insertion hole 10A is also set large. For this reason, the mounting play of the unloading piston 21 becomes large, and due to this mounting play, the piston main body 21A and the insertion hole 10A are worn early, and the life of the unloading mechanism 19 is shortened.

  The present invention has been made in view of the above-described problems of the prior art. It alleviates the impact when the unload piston collides with the suction valve, enhances the durability of the unload piston, and offsets the portion where the unload piston slides. It is an object of the present invention to provide a reciprocating compressor capable of reducing wear.

  In order to solve the above-described problems, a reciprocating compressor employed by the present invention includes a cylinder, a piston provided in the cylinder so as to be capable of reciprocating, a suction chamber mounted on the cylinder, A cylinder head formed with a discharge chamber, a suction valve attached to the lower surface side of the cylinder head and having a valve body for communicating and blocking the suction chamber of the cylinder head with respect to the inside of the cylinder; and the cylinder head Provided with an unloading mechanism that forcibly opens the suction valve during no-load operation, and the unloading mechanism has a bottomed cylindrical shape in which an insertion hole communicating with the suction chamber is formed on the bottom side. An unload cylinder and a base end side are slidably inserted into the unload cylinder, and a distal end side is constituted by an unload piston projecting from the insertion hole of the unload cylinder into the suction chamber.

  The feature of the configuration adopted by the invention of claim 1 is that the unload piston is composed of a rod-like body extending in the axial direction, and is inserted into the insertion hole and protrudes into the suction chamber; A pressure portion that is located on the distal end side of the piston body and depresses the suction valve during no-load operation, and a pressure receiving member that is slidably inserted in the unload cylinder located on the proximal end side of the piston body. And at least the piston body of the unload piston is formed of a resin material.

  With this configuration, the entire unload piston can be reduced in weight, and when the no-load operation is started, the inertial force of the unload piston sliding in the unload cylinder can be reduced. As a result, even when the valve body of the suction valve is pushed downward by the pressing portion of the unload piston, the impact force when the pressing portion collides with the suction valve can be relaxed, and both are in contact with each other The collision noise can be reduced.

  Furthermore, since the piston body is made of a resin material, the clearance between the piston body and the insertion hole of the unload cylinder does not need to be set in advance in consideration of thermal expansion. Wear of only the piston body can reduce wear of the insertion hole of the cylinder head.

  Further, as in the invention of claim 2, the slidability between the piston body of the unload piston and the insertion hole is obtained by forming the unload piston at least the piston body from a self-lubricating resin material. It can be increased and uneven wear can be reduced.

  According to a third aspect of the present invention, at least the piston body of the unload piston is formed of a fiber reinforced resin material.

  Thereby, an unloading piston can be formed in light weight and high intensity | strength, for example using the resin material etc. which were reinforced with glass fiber.

  According to a fourth aspect of the present invention, the unload piston can be formed such that the piston body is made of a resin material and the pressure receiving portion is made of metal.

  Further, as in the invention of claim 5, the unloading piston can be formed of a resin body for the piston body and a metal for the pressing portion.

  Further, as in the invention of claim 6, a phenol resin can be used for the unload piston.

  As described above, according to the first aspect of the present invention, since at least the piston body is formed of a resin material among the unload pistons including the piston body, the pressing portion, and the pressure receiving portion, the weight of the entire unload piston is reduced. Inertia force generated during the sliding can be surely reduced. As a result, when the no-load operation is started, even when the pressing portion of the unload piston strongly collides with the valve body of the suction valve, the impact force at this time can be reduced, and the collision sound at the time of collision is also small. Can be suppressed.

  Furthermore, since the piston body is made of a resin material, the clearance between the piston body and the insertion hole of the unload cylinder does not need to be set in advance in consideration of thermal expansion. By wearing only the piston body, it is possible to prevent wear of the insertion hole of the cylinder head. Thereby, it can prevent reliably that a suction valve is damaged, and can improve durability and lifetime of a reciprocating compressor.

  According to the invention described in claim 2, since at least the piston body of the unload piston is made of a self-lubricating resin material, the lubricity when the unload piston slides in the unload cylinder is improved. The unloading piston can be operated smoothly, and uneven wear of these sliding portions can be reduced.

  Furthermore, according to the invention described in claim 3, since at least the piston body of the unload piston is formed of the fiber reinforced resin material, the overall strength of the unload piston is reduced while reducing the weight of the entire unload piston. And wear resistance, and durability and life can be improved.

  Further, according to the invention described in claim 4, since the unloading piston has the piston body made of a self-lubricating resin material and the pressure receiving part made of metal, the strength of the pressure receiving part can be further increased. Whenever the reciprocating compressor is switched from the no-load operation to the normal load operation, it is possible to reliably prevent the pressure receiving portion of the unload piston from repeatedly colliding with the unload cylinder and being damaged.

  Furthermore, according to the invention described in claim 5, since the piston body of the unload piston is formed of a resin material and the pressing portion is formed of metal, the strength of the pressing portion is further increased while reducing the weight of the unload piston. It can improve and it can prevent reliably that a press part breaks when it collides with a valve plate.

  Further, according to the invention described in claim 6, since the resin material used for the unloading piston is made of phenol resin, the weight of the unloading piston can be reduced with respect to the prior art, and the pressing portion is used as the valve plate. The impact force and the collision sound at the time of collision can be reliably reduced.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings of FIGS.

  Here, FIG. 1 and FIG. 2 show a first embodiment according to the present invention. In the embodiment, the same components as those of the conventional technology are denoted by the same reference numerals, and the description thereof is omitted.

  Reference numeral 31 denotes an unloading mechanism according to an embodiment of the present invention. The unloading mechanism 31 is located above the suction hole 5 and is attached to the mounting cylinder portion 10 of the cylinder head 7. The unload bush 20 is composed of an unload piston 32 and a holding spring 35, which will be described later. During operation, the pressing portion 32B of the unload piston 32 pushes the valve plate 15 of the suction valve 13 downward, and the suction valve By forcibly holding 13 in the valve open state, the compressor is operated without load.

  Reference numeral 32 denotes an unload piston applied to the embodiment of the present invention. As shown in FIG. 2, the unload piston 32 is a thermosetting material in which a self-lubricating resin material such as carbon is kneaded as a whole. It is made of a functional phenol resin, tetrafluoride resin or the like.

  Here, the unload piston 32 includes a piston main body 32A that passes through the insertion hole 10A of the mounting cylinder portion 10 and protrudes into the suction chamber 8, and a small diameter that extends in the axial direction and is positioned on the distal end side of the piston main body 32A. A pressing portion 32B, a pressure receiving portion 32C positioned on the proximal end side of the piston main body 32A and slidably inserted into the cylindrical portion 20A of the unload bush 20; and an outer peripheral side of the pressure receiving portion 32C. And an O-ring mounting groove 32D.

  Further, the pressure receiving portion 32C of the unload piston 32 defines an air chamber 33 between the cylinder portion 20A and the lid portion 20B. An O-ring 34 is mounted in an O-ring mounting groove 32D formed on the outer peripheral side of the pressure receiving portion 32C. Further, molybdenum-based heat-resistant grease is attached to the O-ring 34, and the gap between the pressure receiving portion 32C and the cylindrical portion 20A is sealed with this grease.

  Reference numeral 35 denotes a holding spring for holding the unloading piston 32 at the stop side position when the unloading mechanism 31 is stopped. The holding spring 35 is disposed around the piston main body 32A, and the upper end side contacts the pressure receiving part 32C. The lower end side is in contact with the bottom side of the mounting cylinder 10. The holding spring 35 constantly biases the unload piston 32 toward the air chamber 33 in this state.

  The air compressor according to the embodiment is configured as described above, and the basic operation is not different from that according to the prior art.

  However, according to the embodiment of the present invention, since the unload piston 32 is formed of a self-lubricating resin material, the weight of the unload piston 32 is, for example, about 1/3 of the unload piston 21 of the prior art. The weight can be reduced, and the inertial force generated when the unload piston 32 is displaced can be surely reduced.

  Thereby, when the unload mechanism 31 starts a no-load operation, even if the pressing portion 32B of the unload piston 32 collides with the valve plate 15 of the suction valve 13 positioned on the lower side, it is formed of a resin material. The unloaded piston 32 having a light weight is caused to collide, so that the impact force at the time of the collision can be reduced and the breakage of the valve plate 15 can be prevented.

  Further, since the pressing portion 32B of the unload piston 32 is also formed of a resin material, it occurs when the no-load operation is started and the pressing portion 32B of the unload piston 32 collides with the valve plate 15 of the suction valve 13. Impact noise can be reduced.

  Further, since the unload piston 32 is formed of a self-lubricating resin material, the clearance between the piston main body 32A and the insertion hole 10A and the clearance between the piston main body 32A and the cylindrical portion 20A are set narrowly in advance. Even if the mounting play is reduced, the material of the unload piston 32 is self-lubricating. Therefore, the unload piston 32 smoothly slides with respect to the unload cylinder, and uneven wear of the sliding portion is caused. Can be reduced.

  Moreover, even if the unload piston 32 is thermally expanded and the clearance between the piston body 32A and the insertion hole 10A is narrowed and the piston body 32A comes into contact with the insertion hole 10A, the resin is The piston body 32A made of a material only needs to be worn. Thereby, the unloading piston 32 can prevent the insertion hole 10A from being worn.

  On the other hand, regarding the clearance between the pressure receiving portion 32C of the unloading piston 32 and the cylinder portion 20A of the unloading bush 20, even if the unloading piston 32 is thermally expanded and the clearance becomes narrower, the pressure receiving pressure formed of resin. It is only necessary to wear the portion 32C. Thereby, the unload piston 32 can prevent the cylindrical portion 20A of the unload bush 20 from being worn.

  Furthermore, as described above, even if the unload piston 32 causes uneven wear that is offset with respect to the insertion hole 10A and the cylindrical portion 20A, the unload piston 32 can be manufactured from an inexpensive resin material. Therefore, it can also be used by exchanging, extending the life of the unload mechanism 31 and increasing the reliability of the air compressor.

  Further, since the unload piston 32 is formed of a resin material, it is not necessary to subject the surface thereof to rust prevention treatment, the conventional lubricating film 22 and the like can be omitted, and man-hours for forming the unload piston 32 are eliminated. Costs can be reduced.

  Thus, since the entire unload piston 32 is formed of a self-lubricating resin material, when the unloading mechanism 31 is operated, the pressing portion 32B of the unload piston 32 strongly collides with the valve plate 15 of the suction valve 13. The impact force can be reduced, and the suction valve 13 can be reliably prevented from being damaged, and the collision sound when the pressing portion 32B collides with the valve plate 15 can be reduced. Thereby, the durability and life of the unload piston 32 and the suction valve 13 can be greatly improved, and the compression performance and the like of the air compressor can be favorably maintained over a long period of time.

  Next, FIG. 3 shows a second embodiment according to the present invention. The reciprocating compressor according to this embodiment is characterized in that the piston main body 41A, the pressing portion 41B and the pressure receiving portion 41C of the unload piston 41 are made of fibers. It is formed by a reinforced resin material.

  Here, this fiber reinforced resin material is formed by mixing short fibers such as glass fibers with a resin material having self-lubricating properties such as phenol resin and tetrafluoride resin kneaded with carbon. The resin material (FRP) or the like.

  Thus, even in the present embodiment configured as described above, it is possible to obtain substantially the same operational effects as in the first embodiment, and the weight of the unload piston 41 is reduced to about 1/3 that of the prior art. In addition, the impact force and the collision sound when the pressing portion 41B collides with the valve plate 15 can be reliably reduced.

  In particular, in the present embodiment, by using a fiber reinforced resin material, it is possible to give high strength and wear resistance to the lightweight unload piston 41. For example, the unload piston 41 and the mounting cylinder portion 10 can be provided. The durability and life can be improved without applying lubricating oil or the like to the sliding surface.

  Next, FIG. 4 shows a third embodiment according to the present invention. The reciprocating compressor according to the present embodiment is characterized in that the unload piston 51 and the piston main body 52A and the pressing portion 52B are self-lubricating. The piston member 52 is formed of a resin material, and the pressure receiving portion 53A and the O-ring mounting groove 53B are configured by a pressure receiving member 53 formed of a metal material. Here, the piston member 52 and the pressure receiving member 53 are integrated by means such as insert molding, press fitting, and screwing.

  Thus, in the present embodiment configured as described above, it is possible to obtain substantially the same operational effects as those of the first embodiment. In particular, in the present embodiment, the strength of the pressure receiving portion 53A can be further increased, and the pressure receiving portion 53A of the unload piston 51 is held by the holding spring 35 every time the compressor is switched from the no-load operation to the normal load operation. This urging force can reliably prevent the lid portion 20B of the unload bush 20 from repeatedly colliding and being damaged.

  Further, for example, when the unloading piston 51 is replaced by integrating the piston member 52 and the pressure receiving member 53 detachably by screwing or the like, only the piston member 52 needs to be replaced. Etc. can be saved. In addition, as shown by the dotted line in FIG. 4, the pressing portion 52B ′ may be formed in a truncated cone shape on the distal end side of the unload piston 51.

  Next, FIG. 5 shows a fourth embodiment according to the present invention. The reciprocating compressor according to this embodiment is characterized in that the unloading piston 61 and the piston main body 62A and the pressure receiving portion 62B are self-lubricating. The piston member 62 is formed of a resin material and a metal pressing portion 63 that is integrated on the front end side of the piston member 62 using, for example, insert molding.

  Thus, in the present embodiment configured as described above, it is possible to obtain substantially the same operational effects as those of the first embodiment. And especially in this Embodiment, the strength of the press part 63 can be improved further, aiming at weight reduction of the unload piston 61 by forming only the press part 63 with a metal material, and the press part 63 and the valve plate 15 are improved. It can be surely prevented from being damaged when colliding.

  In the third and fourth embodiments, the piston bodies 52A, 62A, etc. of the unload pistons 51, 61 are made of a self-lubricating resin material. However, the present invention is not limited to this, and the piston body Similarly to the unload piston 41 of the second embodiment, 52A, 62A, and the like may be formed of a fiber reinforced resin material such as FRP.

  In each of the above-described embodiments, an air compressor is described as an example of a reciprocating compressor. However, the present invention is not limited to this, and is widely applied to, for example, a compressor that compresses a gas other than air. it can.

It is a longitudinal cross-sectional view which shows the unload mechanism etc. of the air compressor by the 1st Embodiment of this invention. It is a longitudinal cross-sectional view of the unload piston shown in FIG. It is a longitudinal cross-sectional view which shows the unload piston of the air compressor by 2nd Embodiment. It is a longitudinal cross-sectional view which shows the unload piston of the air compressor by 3rd Embodiment. It is a longitudinal cross-sectional view which shows the unload piston of the air compressor by 4th Embodiment. It is a longitudinal cross-sectional view which shows the air compressor by a prior art. It is a longitudinal cross-sectional view which shows the unload mechanism etc. of the air compressor by a prior art. It is a longitudinal cross-sectional view of the unload piston shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder 7 Cylinder head 8 Suction chamber 10 Mounting cylinder part 10A Insertion hole 11 Piston 13 Suction valve 15 Valve plate 20 Unload bush 31 Unload mechanism 32, 41, 51, 61 Unload piston 32A, 41A, 52A, 62A Piston main body 32B, 41B, 52B, 52B ′, 63 Pressing portion 32C, 41C, 53A, 62B Pressure receiving portion 32D, 53B O-ring mounting groove 52, 62 Piston member 53 Pressure receiving member

Claims (6)

A cylinder, a piston provided in the cylinder so as to be capable of reciprocating, a cylinder head mounted on the cylinder and having a suction chamber and a discharge chamber formed therein, and attached to the lower surface side of the cylinder head; A suction valve having a valve body that communicates and shuts off the suction chamber of the cylinder head with respect to the inside of the cylinder; and an unload mechanism that is provided in the cylinder head and forcibly opens the suction valve during no-load operation; The unload mechanism has a bottomed cylindrical unload cylinder in which an insertion hole communicating with the suction chamber is formed on the bottom side, and a base end side is slidably inserted into the unload cylinder. In the reciprocating compressor in which the tip side is constituted by an unload piston protruding from the insertion hole of the unload cylinder into the suction chamber,
The unload piston is composed of a rod-like body extending in the axial direction, and is inserted into the insertion hole and protrudes into the suction chamber. The unloading piston is located on the distal end side of the piston body and is in the no-load operation. And a pressure receiving portion that is located on the base end side of the piston body and is slidably inserted into the unload cylinder, and at least the piston body of the unload piston is A reciprocating compressor characterized by being formed of a resin material.   2. The reciprocating compressor according to claim 1, wherein the unload piston includes at least a piston body made of a self-lubricating resin material.   2. The reciprocating compressor according to claim 1, wherein the unload piston includes at least a piston main body formed of a fiber reinforced resin material.   4. The reciprocating compressor according to claim 1, wherein the unload piston has a piston body made of a resin material and a pressure receiving portion made of metal. 5.   4. The reciprocating compressor according to claim 1, wherein the unload piston has a piston body made of a resin material and a pressing portion made of metal. 5.   The reciprocating compressor according to claim 1, 2, 3, 4 or 5, wherein the resin material used for the unload piston is phenol resin.

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