Air compressor

Abstract

To acquire an air compressor which can suppress entry of dust into a crank case.SOLUTION: An air compressor 1 includes: a first cylinder 11a for storing a first piston 11b; a second cylinder 12a in which the air compressed in the first cylinder 11a is introduced, and which stores a second piston 12b; and a crank case 20. The crank case 20 includes: a cylindrical body 20a for storing a crank shaft 33; a first bore 20b into which a first rod 11c is inserted for connecting the crank shaft 33 and the first piston 11b; and a second bore 20c into which a second rod 12c is inserted for connecting the crank shaft 33 and the second piston 12b. The crank case 20 includes a first crank case 21 and a second crank case 23 assembled mutually so as to divide the cylindrical body 20a, divide the first bore 20b, and divide the second bore 20c.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 nailers and air dusters. [Background technology]

[0002] Patent Document 1 discloses a technology related to an air compressor. The air compressor has a reciprocating compression mechanism that generates compressed air. The compression mechanism has a crankshaft rotated by an electric motor and two compression units arranged on both sides in a direction approximately perpendicular to the crankshaft direction. The first compression unit has a first cylinder extending in a direction approximately perpendicular to the crankshaft and a first piston reciprocating in the first cylinder. The second compression unit has a second cylinder extending in a direction approximately perpendicular to the crankshaft and a second piston reciprocating in the second cylinder. The first piston and the second piston are connected to the crankshaft by a first rod and a second rod, respectively. The crankshaft, the first rod, and the second rod are housed in a crankcase made of metal, such as aluminum. The first cylinder and the second cylinder are supported by the crankcase.

[0003] The first and second pistons reciprocate in their respective cylinders due to the rotational power of the crankshaft. The first piston generates compressed air from the outside air taken into the first cylinder via the crankcase. The second piston further compresses the compressed air sent from the first cylinder to the second cylinder. The compressed air generated in the second cylinder is stored in a tank. The compressed air stored in the tank is supplied to pneumatic tools such as compressed air-driven nailers and air dusters.

[0004] The crankcase is provided with an intake section for taking in outside air. The intake section has an intake filter for filtering dust contained in the outside air. The crankcase is provided in a shape in which a cylindrical main body that accommodates the crankshaft, a first bore through which the first rod is inserted, and a second bore through which the second rod is inserted are connected. The crankcase is provided in a shape that allows the crankshaft, the first rod, and the second rod to be assembled. For example, in the conventional air compressor described in the cited document 1, parts of the substantially cylindrical shapes of the first bore and the second bore are cut out. A seal member that prevents dust from entering the crankcase is attached to the cutout portion. The seal member is provided using a material such as rubber.

[0005] In the unlikely event that the intake filter becomes clogged due to dust accumulation, etc., the intake performance of the intake section will decrease. If compressed air continues to be generated with the intake performance decreased, negative pressure will be generated inside the crankcase. The negative pressure will cause the rubber seal member to bend, and dust may enter the crankcase along with the outside air through the bent part of the seal member. If dust enters the compression mechanism, it may wear out the sliding members such as the piston, shortening the product lifespan. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-19476 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, there is a need for an air compressor that can prevent dust from entering the crankcase. [Means for solving the problem]

[0008] According to one aspect of the present disclosure, an air compressor has a first cylinder that houses a first piston. The air compressor has a second cylinder into which air compressed in the first cylinder is introduced and that houses a second piston. The air compressor has a crankcase. The crankcase has a cylindrical body that houses a crankshaft. The crankcase has a first bore through which a first rod that connects the crankshaft and the first piston is inserted. The crankcase has a second bore through which a second rod that connects the crankshaft and the second piston is inserted. The crankcase has a first crankcase and a second crankcase that are assembled to each other so as to divide the cylindrical body, divide the first bore, and divide the second bore.

[0009] Therefore, the cylindrical body, the first bore, and the second bore are divided into the first crankcase and the second crankcase so that the crankshaft, the first rod, and the second rod, which are connected together, can be assembled. The dividing surface of the crankcase is provided near the center of the crankcase so as to divide the cylindrical body, the first bore, and the second bore. Therefore, the periphery of the dividing surface of the first crankcase and the second crankcase can be provided with high rigidity. Therefore, the periphery of the dividing surface of the first crankcase and the second crankcase is not easily deformed by the pressure difference between the inside and outside of the crankcase. This makes it possible to suppress the intrusion of dust into the crankcase. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is an external perspective view of an air compressor. [Diagram 2] This is a view taken along the line II in Figure 1. This figure is a perspective view of the air compressor as seen from the left rear. This figure shows the state in which the main body cover has been removed to expose the compression mechanism. [Diagram 3] FIG. 2 is a cross-sectional view of a compression mechanism according to an embodiment of the present disclosure. [Figure 4] 4 is a cross-sectional view taken along line IV-IV in FIG. 3. [Diagram 5] FIG. 4 is a cross-sectional view of the crankcase taken along the cross section shown in FIG. [Figure 6] FIG. 5 is a vertical cross-sectional view of a crankcase taken along the cross section shown in FIG. [Figure 7] FIG. [Figure 8] FIG. 2 is an exploded perspective view of the crankcase as viewed from the left. [Figure 9] FIG. 4 is an exploded perspective view of the crankcase as viewed from the right. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] According to another feature of the present disclosure, the first crankcase has a first divided surface extending in a single plane. The second crankcase has a second divided surface extending in a single plane and facing the first divided surface. Therefore, the first crankcase and the second crankcase can be assembled to the crankcase by mating the first divided surface with the second divided surface. By increasing the flatness of the first divided surface and the second divided surface, the airtightness between the first divided surface and the second divided surface can be increased.

[0012] According to another feature of the present disclosure, the first crankcase has a first flange extending outward from a dividing edge of the cylindrical body and the first bore and the second bore. The second crankcase has a second flange extending outward from a dividing edge of the cylindrical body and the first bore and the second bore. The first flange and the second flange are assembled to each other by a fastener. Thus, by providing the first flange and the second flange, the dividing edge area of ​​the first crankcase and the second crankcase can be increased. This can improve the sealing property and rigidity at the dividing edge of the first crankcase and the second crankcase.

[0013] According to another feature of the present disclosure, a seal member is provided between the first flange of the first crankcase and the second flange of the second crankcase. This makes it possible to reduce the area of ​​the seal member visible from the outside of the crankcase. Therefore, the seal member is less deformed by pressure, for example, when a pressure difference occurs between the inside and outside of the crankcase. This makes it possible to suppress the formation of a path through which dust can enter around the seal member. This makes it possible to improve the sealing performance at the dividing edge between the first crankcase and the second crankcase.

[0014] According to another feature of the present disclosure, the crankcase has a first cover that closes a first end of the cylindrical body. The crankcase has a second cover that covers a second end of the cylindrical body and has an intake section that allows outside air to be introduced. The first crankcase has the first cover, and the second crankcase has the second cover. Thus, the first crankcase and the second crankcase are provided in a shape that does not divide the intake section. This makes it possible to prevent the formation of a path through which dust can enter the intake section.

[0015] According to another feature of the present disclosure, the crankcase is divided into a first crankcase and a second crankcase by a plane that is parallel to and approximately at the axial centerline of a cylindrical first bore located on the first cylinder side. Therefore, the axial centerline of the first bore is located approximately at the center of the crankcase in the axial direction of the crankshaft. Therefore, the dividing edges of the first crankcase and the second crankcase can be provided with high rigidity. In addition, the high rigidity of each dividing edge can be utilized to improve the ease of assembly of the first crankcase and the second crankcase.

[0016] According to another feature of the present disclosure, the air compressor has a tank that stores the air compressed in the second cylinder. The first crankcase has a base that is fastened to the tank. Therefore, the second crankcase can be removed from the first crankcase while the first crankcase is connected to the tank via the base. By removing the second crankcase, the crankshaft, the first rod, the second rod, etc. housed in the crankcase can be repaired, replaced, etc. This can improve the maintainability of the air compressor.

[0017] According to another feature of the present disclosure, the air compressor has a plurality of fasteners for assembling the first crankcase and the second crankcase. The plurality of fasteners includes a plurality of first bore side fasteners located around the first bore, and a plurality of second bore side fasteners located around the second bore, the number of which is greater than the number of the first bore side fasteners. Thus, by having more second bore side fasteners than the first bore side fasteners, the second bore has a higher fastening strength than the first bore. Therefore, the second bore can stably support the second cylinder, which generates compressed air at a higher pressure than the first cylinder.

[0018] Next, one embodiment of the present disclosure will be described with reference to Figs. 1 to 9. As shown in Figs. 1 and 2, an air compressor 1 has two approximately cylindrical tanks 2 that are long from front to back. The generated compressed air is stored in the two tanks 2. Legs 3 are provided at a total of four locations, at the front and rear of the two tanks 2. A rubber material with high vibration resistance is used for each leg 3. Side protectors 3a are provided in parallel on each leg 3. A drain cock 2a for discharging drain water from the tanks 2 is provided between the front parts of the two tanks 2. The upper parts of the two tanks 2 are mutually connected by a base part 4. A compression mechanism (compressor body) 10 is mounted on the upper surface of the base part 4. Handle parts 5 for carrying are provided at the front and rear of the base part 4, straddling the upper parts of the two tanks 2. Fig. 1 shows a state in which the compression mechanism 10 is covered with a body cover 6. When the body cover 6 is removed as shown in Fig. 2, the compression mechanism 10 is exposed.

[0019] As shown in FIG. 1, high-pressure outlets 7 and low-pressure outlets 8 are arranged on the front side of the main body cover 6, two on each side. 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. An operation unit 9 including various display units and mainly used for startup operations is provided on the front upper surface of the main body cover 6. A plurality of ventilation holes 6a are provided in a mesh-like arrangement on the front, rear, left and right sides of the main body cover 6 (the ventilation holes 6a on the rear side of the main body cover 6 are not visible in FIG. 1).

[0020] 2 and 3, the compression mechanism 10 has a first compression section 11 in the front part of a substantially cylindrical crankcase 20, and a second compression section 12 in the rear part of the crankcase 20. An electric motor 30 is supported on the right side of the crankcase 20 between the first compression section 11 and the second compression section 12. The crankcase 20 is fixed onto a base section 4.

[0021] As shown in FIGS. 2 and 3, the electric motor 30 is a brushless motor that can obtain a relatively large starting torque. The electric motor 30 has a circular rotor 30a and a similarly circular stator 30b located on the inner periphery of the rotor 30a. The stator 30b is fixed to the right side of the crankcase 20. A crankshaft (motor shaft) 33 is coupled to the center of the rotor 30a. A heat dissipation fan 31 is attached to the right end of the crankshaft 33. When the heat dissipation fan 31 rotates together with the crankshaft 33, heat generated by the electric motor 30 is dissipated, and the electric motor 30 is cooled. The crankshaft 33 extends leftward through the center of the stator 30b. The crankshaft 33 is supported rotatably between the right and left sides of the crankcase 20 via a right bearing 33a and a left bearing 33b. The left end side of the crankshaft 33 protrudes leftward through an intake section 40. An intake fan 32 is attached to the left end of the crankshaft 33. Outside air is blown into an intake section 40 by the rotation of the intake fan 32.

[0022] 3, power for generating compressed air is transmitted to the first compression section 11 and the second compression section 12 from a crankshaft 33. A first crank portion 34 and a second crank portion 35, each of which is substantially disk-shaped, are attached to the crankshaft 33 in an eccentric state with respect to the motor axis J. The first crank portion 34 is provided in the center of the crankshaft 33 in the left-right direction. The second crank portion 35 is provided to the right of the first crank portion 34, side by side with the first crank portion 34.

[0023] As shown in FIG. 3, a first rod 11c of the first compression section 11 is connected to the first crank section 34. A first piston 11b of the first compression section 11 is attached to the tip of the first rod 11c. The first piston 11b is housed in a first cylinder 11a extending in the front-rear direction, and reciprocates in the front-rear direction within the first cylinder 11a. A second rod 12c of the second compression section 12 is connected to the second crank section 35. A second piston 12b of the second compression section 12 is attached to the tip of the second rod 12c. The second piston 12b is housed in a second cylinder 12a extending in the front-rear direction, and reciprocates in the front-rear direction within the second cylinder 12a.

[0024] As shown in Fig. 3, the first crank portion 34 and the second crank portion 35 are eccentric in the same direction at the same position around the axis of the crankshaft 33. Therefore, one rotation of the crankshaft 33 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.

[0025] As shown in Fig. 3, 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 (see Fig. 2). 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 into the supply pipe 13 via the auxiliary check valve 11e is supplied directly to the second compression chamber 12d.

[0026] In this way, by starting the electric motor 30, 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.

[0027] As shown in Figs. 3 and 5, the crankcase 20 has a central cylindrical body 20a, a first bore 20b in the front portion, and a second bore 20c in the rear portion. The cylindrical body 20a has a generally cylindrical shape centered approximately on the motor axis J. The first bore 20b has a generally cylindrical shape centered approximately on the axial center of a first rod 11c extending in the front-rear direction. The opening at the rear end of the first bore 20b is connected to the cylindrical body 20a. The first cylinder 11a of the first compression section 11 is connected to the front end of the first bore 20b. The axial center line of the first cylinder 11a is approximately aligned with the axial center line K of the first bore 20b. The axial center line K is located at the center of the crankcase 20 in the left-right direction.

[0028] As shown in FIG. 3, the second bore 20c has a generally cylindrical shape centered approximately on the axial center of the second rod 12c extending in the front-rear direction. The second bore 20c is provided with a bore diameter smaller than that of the first bore 20b. The opening at the front end of the second bore 20c is connected to the cylindrical main body 20a. The second cylinder 12a of the second compression section 12 is connected to the rear end of the second bore 20c. The axial center line of the second cylinder 12a is approximately at the same position as the axial center line L of the second bore 20c. The axial center line L of the second bore 20c is located to the right of the axial center line K of the first bore 20b and closer to the electric motor 30. Therefore, the axial center line L of the second bore 20c is located to the right of the center of the crankcase 20 in the left-right direction.

[0029] 7 to 9, the crankcase 20 is divided into a first crankcase 21 on the left side and a second crankcase 23 on the right side. The first crankcase 21 and the second crankcase 23 are made of aluminum.

[0030] 3 and 4, the first crankcase 21 and the second crankcase 23 are divided into left and right halves by a plane S that extends substantially vertically. The plane S extends parallel to the axial centerline K of the first bore 20b at substantially the same left-right position as the axial centerline K. A first dividing surface 21d of the first crankcase 21 and a second dividing surface 23d of the second crankcase 23 are each formed as a single plane and face each other on the plane S.

[0031] 4, 5, 8 and 9, a base portion 28 extending substantially horizontally is provided on the lower part of the first crankcase 21. One base portion 28 is provided at the front and one at the rear of the first crankcase 21. The base portion 28 is connected to the upper surface of the base portion 4 that connects the two tanks 2. In this way, the crankcase 20 is held above the tanks 2.

[0032] As shown in Figs. 7 to 9, the first crankcase 21 has a cylindrical main body dividing portion 21a, a first bore dividing portion 21b, and a second bore dividing portion 21c that are integrally formed of the same material. The second crankcase 23 has a cylindrical main body dividing portion 23a, a first bore dividing portion 23b, and a second bore dividing portion 23c that are integrally formed of the same material. The cylindrical main body dividing portion 21a and the cylindrical main body dividing portion 23a divide the cylindrical main body 20a into left and right parts. The first bore dividing portion 21b and the first bore dividing portion 23b divide the first bore 20b into left and right parts. The second bore dividing portion 21c and the second bore dividing portion 23c divide the second bore 20c into left and right parts.

[0033] As shown in Figs. 8 and 9, the inner peripheral surface of the first bore 20b opens from the front end to the rear end at the dividing edge of the first bore dividing portion 21b. The inner peripheral surface of the second bore 20c opens from the front end to the rear end at the dividing edge of the second bore dividing portion 21c. The inner peripheral surface of the cylindrical main body 20a opens from the front end to the rear end at the dividing edge of the cylindrical main body dividing portion 21a. Moreover, the opening of the cylindrical main body dividing portion 21a communicates with the opening of the first bore dividing portion 21b and the opening of the second bore dividing portion 21c in the front-rear direction. Therefore, with the second crankcase 23 removed from the first crankcase 21, an assembly in which the crankshaft 33, the first rod 11c, and the second rod 12c are assembled can be inserted from the right to the left into the first crankcase 21.

[0034] As shown in Figs. 8 and 9, the crankcase 20 has a first cover 22 that closes the first end 20d on the right side and a second cover 24 that closes the second end 20e on the left side. The first cover 22 is made of the same material as the first crankcase 21 and is provided integrally therewith. The second cover 24 is made of the same material as the second crankcase 23 and is provided integrally therewith. A substantially cylindrical bearing recess 22a is provided in the center of the first cover 22. An insertion hole 22b that penetrates the first cover 22 in the left-right direction is provided in the center of the bearing recess 22a. A bearing 33a that rotatably supports the crankshaft 33 is held in the bearing recess 22a. The crankshaft 33 is inserted into the insertion hole 22b. A screw hole 22c for screwing and fixing the stator 30b with a fixing screw 29 is provided in the right side surface of the first cover 22.

[0035] As shown in Figures 7 to 9, the first crankcase 21 has a first flange 21e at the dividing edge of the cylindrical body 20a and the first bore 20b and the second bore 20c. The first flange 21e extends outward from the crankcase 20 along the first dividing surface 21d. The first flange 21e is provided continuously in the front-rear direction from the front end of the first bore 20b to the rear end of the second bore 20c, with a substantially constant thickness in the left-right direction. A plurality of screw holes 21f are provided in the first flange 21e. The screw holes 21f extend rightward from the first dividing surface 21d.

[0036] 7 to 9, the second crankcase 23 has a second flange 23e at the dividing edge of the cylindrical body 20a and the first and second bores 20b and 20c. The second flange 23e extends outward from the crankcase 20 along the second dividing surface 23d. The second flange 23e is provided continuously in the front-rear direction from the front end of the first bore 20b to the rear end of the second bore 20c, with a substantially constant thickness in the left-right direction. The second flange 23e is provided with a plurality of insertion holes 23f penetrating in the left-right direction.

[0037] As shown in Figs. 7 to 9, a passage groove 21g is provided in the lower part of the first bore divided part 21b of the first crankcase 21. The passage groove 21g is recessed from the first dividing surface 21d toward the right. The passage groove 21g extends in the front-rear direction from the front end of the first bore divided part 21b to the inner peripheral surface of the cylindrical main body divided part 21a. A passage groove 23g is provided in the lower part of the first bore divided part 23b of the second crankcase 23. The passage groove 23g is recessed from the second dividing surface 23d toward the left. The passage groove 23g extends in the front-rear direction from the front end of the first bore divided part 23b to the inner peripheral surface of the cylindrical main body divided part 23a. By connecting the first crankcase 21 and the second crankcase 23, the passage groove 21g and the passage groove 23g are connected to form the air passage 20f. The outside air taken into the cylindrical body 20a is supplied to the first cylinder 11a (see FIG. 3) through an air passage 20f.

[0038] As shown in Figs. 8 and 9, thin, flat rubber seal members 26 and 27 are interposed between the first divided surface 21d and the second divided surface 23d. The seal member 26 is provided in substantially the same shape as the first divided surface 21d of the upper first flange 21e and the second divided surface 23d of the upper second flange 23e. The seal member 26 is provided with a plurality of insertion holes 26a for inserting the fastener 25 described below. The seal member 27 is provided in substantially the same shape as the first divided surface 21d of the lower first flange 21e and the second divided surface 23d of the lower second flange 23e. The seal member 27 is provided with a plurality of insertion holes 27a for inserting the fastener 25.

[0039] The seal members 26, 27 shown in Figs. 8 and 9 are sandwiched between the first crankcase 21 and the second crankcase 23 to airtightly seal the gap between the first divided surface 21d and the second divided surface 23d. The seal members 26, 27 are thin in the left-right direction and have a radial length that is approximately the same as the radial thickness of the cylindrical main body 20a, the first bore 20b, or the second bore 20c. Therefore, even if the pressure inside the crankcase 20 becomes negative relative to the outside air, the seal members 26, 27 are unlikely to deform in the left-right direction and are unlikely to form a path in the radial direction through which the outside air can enter. Therefore, the intrusion of the outside air into the crankcase 20 due to the negative pressure is suppressed.

[0040] As shown in Figs. 8 and 9, the first crankcase 21 has six screw holes 21f, three on the upper first divided surface 21d and three on the lower first divided surface 21d. The second crankcase 23 has six insertion holes 23f, three on the upper second divided surface 23d and three on the lower second divided surface 23d. The seal member 26 has three insertion holes 26a and the seal member 27 has three insertion holes 27a. The screw holes 21f, the insertion holes 26a and 27a, and the insertion hole 23f are arranged so as to be aligned horizontally in a state where the first crankcase 21, the seal members 26 and 27, and the second crankcase 23 are connected in the left-right direction. A fastener (connecting screw) 25 for connecting the first crankcase 21 and the second crankcase 23 is inserted into the insertion holes 23f and the insertion holes 26a and 27a. The first crankcase 21 and the second crankcase 23 are connected by fastening each fastener 25 to the screw hole 21f. The second crankcase 23 can be removed from the first crankcase 21 by loosening each fastener 25.

[0041] As shown in Figs. 7 to 9, the multiple fasteners 25 include a first bore side fastener 25a attached around the first bore 20b in front of the crankshaft 33, and a second bore side fastener 25b attached around the second bore 20c in the rear of the crankshaft 33. More second bore side fasteners 25b are attached than the first bore side fasteners 25a. In this embodiment, two first bore side fasteners 25a are attached, one on the upper side and one on the lower side. Four second bore side fasteners 25b are attached, two on the upper side and two on the lower side. The first crankcase 21 and the second crankcase 23 are assembled with the multiple fasteners, and the seal members 26, 27 are interposed between the first crankcase 21 and the second crankcase 23, so that the crankcase 20 is airtight.

[0042] As shown in Figures 3 and 4, the second cover 24 is provided with an intake section 40 that introduces outside air into the crankcase 20. The second cover 24 has a plurality of intake holes 24e penetrating in the left-right direction. In Figures 3 and 4, outside air flows from left to right through the intake section 40 and is taken into the crankcase 20. Hereinafter, the upstream side of the intake flow will also be referred to as the outside, and the downstream side as the inside. The intake section 40 has the second cover 24 in which the intake holes 24e are formed, a filter 41 that closes the intake hole 24e of the second cover 24, a filter cover 42 that covers the filter 41, and a dust cover 43 that covers the filter cover 42.

[0043] 3 and 4, a cylindrical bearing recess 24a is provided at the center of the inner surface of the second cover 24. A bearing 33b is held in the bearing recess 24a. One regulating plate 33c is screwed to the opening side of the bearing recess 24a with four fixing screws 44. This causes the opening side of the bearing recess 24a to be closed by the regulating plate 33c. By sandwiching the bearing 33b between the bottom of the bearing recess 24a and the regulating plate 33c, misalignment of the bearing 33b in the direction of the motor axis J is restricted.

[0044] As shown in Figs. 3, 4 and 7, a filter accommodating recess 24b for accommodating a filter 41 is provided on the outer surface side of the second cover 24. A cylindrical protrusion 24c for forming the bearing recess 24a on the inner surface side is provided at the center of the filter accommodating recess 24b. The crankshaft 33 is inserted into an insertion hole 24d provided at the center of the protrusion 24c. Projections 24h that project radially outward are provided at four equal positions on the periphery of the protrusion 24c. A screw hole 24i is provided in each of the projecting portions 24h. A fixing screw 44 for screwing the restricting plate 33c to the second cover 24 is screwed into the screw hole 24i. The filter accommodating recess 24b is provided around the protrusion 24c.

[0045] 3, 5, and 7, the second cover 24 has a plurality of screw bosses 24f radially outward from the filter accommodating recess 24b. In this embodiment, four screw bosses 24f are provided. A screw hole 24g is provided on the inner periphery of each screw boss 24f. Fixing screws 45 are fastened into the screw holes 24g of the four screw bosses 24f, respectively, whereby the filter cover 42 and the dust cover 43 are screwed to the second cover 24 by so-called co-fastening.

[0046] As shown in Fig. 7, each screw boss portion 24f is provided on the outer surface of the second cover 24 in a state of protruding to the left. The outer diameter of each screw boss portion 24f is stepped, with a large diameter portion on the base side and a small diameter portion on the tip side. Air intake holes 24e are provided on both sides of each screw boss portion 24f. In this embodiment, a total of eight air intake holes 24e are provided. One filter 41 (see Fig. 3) is accommodated in the filter accommodating recess 24b so as to block the eight air intake holes 24e from the outside.

[0047] 3 and 4, the filter 41 is a sound-absorbing and dust-proof filter made of felt material and is formed in a generally circular plate shape. An insertion hole 41a is provided in the center of the filter 41, through which the convex portion 24c and the protruding portion 24h of the second cover 24 are inserted. Insertion holes 41b are provided around the insertion hole 41a at four locations, through which the large diameter portion of the screw boss portion 24f of the second cover 24 is inserted.

[0048] As shown in Figures 3 and 4, a filter cover 42 is attached to the outside (left side) of the filter 41. The filter cover 42 is formed in a disk shape with approximately the same diameter as the filter 41. The entire intake side of the filter 41 is covered by the filter cover 42. An insertion portion 42a through which the crankshaft 33 is inserted is provided in the center of the filter cover 42. The filter cover 42 has multiple intake holes that are not visible in the figures. Insertion holes 42b are provided at quarters on the peripheral side of the filter cover 42, for inserting the small diameter portion of the screw boss portion 24f of the second cover 24 therethrough.

[0049] As shown in Figs. 3 and 4, the dust cover 43 is formed in a disk shape with approximately the same diameter as the filter cover 42. The dust cover 43 blocks the flow of outside air generated by the intake fan 32, preventing it from being blown directly onto the filter cover 42. A cylindrical insertion portion 43a is provided at the center of the inner surface of the dust cover 43. The insertion portion 43a protrudes toward the filter cover 42 side (right side). The insertion portion 42a of the filter cover 42 is inserted into the insertion portion 43a. The tip of the crankshaft 33 protrudes outward through the inner circumferential side of the insertion portion 42a inserted into the insertion portion 43a. The intake fan 32 is supported by the protruding portion. Insertion holes 43b through which fixing screws 45 are inserted are provided at four equal circumferential positions on the inner surface of the dust cover 43.

[0050] 3 and 4, the outer periphery of the filter cover 42 and the dust cover 43 is bent at an angle of approximately 45° over the entire circumference with a constant width toward the second cover 24. An air intake 46 with a constant gap is formed between the bent dust cover 43 and the filter cover 42.

[0051] 3 and 4, the dust cover 43 and the filter cover 42 are joined to the second cover 24 by four fixing screws 45, so-called co-fastening. The large diameter portions of the four screw boss portions 24f of the second cover 24 are positioned in the insertion holes 41b of the filter 41. The small diameter portions of the screw boss portions 24f are positioned straddling the insertion holes 42b of the filter cover 42 and the insertion holes 43b of the dust cover 43. The fixing screws 45 are fastened into the screw holes 24g of the screw boss portions 24f, so that the dust cover 43 and the filter cover 42 are co-fastened to the second cover 24. As a result, the filter 41 is held in the filter accommodating recess 24b of the second cover 24.

[0052] As described above, the air compressor 1 has a first cylinder 11a that houses a first piston 11b as shown in Fig. 3. The air compressor 1 has a second cylinder 12a into which air compressed in the first cylinder 11a is introduced and that houses a second piston 12b. The air compressor 1 has a crankcase 20. The crankcase 20 has a cylindrical body 20a that houses a crankshaft 33. The crankcase 20 has a first bore 20b through which a first rod 11c that connects the crankshaft 33 and the first piston 11b is inserted. The crankcase 20 has a second bore 20c through which a second rod 12c that connects the crankshaft 33 and the second piston 12b is inserted. The crankcase 20 has a first crankcase 21 and a second crankcase 23 which are assembled to each other so as to divide the cylindrical body 20a, to divide the first bore 20b, and to divide the second bore 20c.

[0053] Therefore, the cylindrical body 20a, the first bore 20b, and the second bore 20c are divided into the first crankcase 21 and the second crankcase 23 so that the crankshaft 33, the first rod 11c, and the second rod 12c, which are integrally connected, can be assembled. The dividing surface (plane S) of the crankcase 20 is provided near the center of the crankcase 20 so as to divide the cylindrical body 20a, the first bore 20b, and the second bore 20c. Therefore, the periphery of the first dividing surface 21d of the first crankcase 21 and the periphery of the second dividing surface 23d of the second crankcase 23 can be provided with high rigidity. Therefore, the periphery of the first dividing surface 21d of the first crankcase 21 and the periphery of the second dividing surface 23d of the second crankcase 23 are not easily deformed by the pressure difference between the inside and outside of the crankcase 20. This makes it possible to suppress the intrusion of dust into the crankcase 20.

[0054] 8 and 9, the first crankcase 21 has a first divided surface 21d that extends in a single plane. The second crankcase 23 has a second divided surface 23d that extends in a single plane and faces the first divided surface 21d. Therefore, the first crankcase 21 and the second crankcase 23 can be assembled to the crankcase 20 by matching the surfaces of the first divided surface 21d and the second divided surface 23d. By increasing the flatness of the first divided surface 21d and the second divided surface 23d, the airtightness between the first divided surface 21d and the second divided surface 23d can be improved.

[0055] As shown in Figs. 7 to 9, the first crankcase 21 has a first flange 21e extending outward from the dividing edge of the cylindrical body 20a and the first bore 20b and the second bore 20c. The second crankcase 23 has a second flange 23e extending outward from the dividing edge of the cylindrical body 20a and the first bore 20b and the second bore 20c. The first flange 21e and the second flange 23e are assembled to each other by a fastener 25. Therefore, by providing the first flange 21e and the second flange 23e, the area of ​​the core dividing edge of the first crankcase 21 and the second crankcase 23 can be increased. This can improve the sealing property and rigidity at the dividing edge of the first crankcase 21 and the second crankcase 23.

[0056] As shown in Figures 8 and 9, the seal members 26, 27 are provided between the first flange 21e of the first crankcase 21 and the second flange 23e of the second crankcase 23. This makes it possible to reduce the area of ​​the seal members 26, 27 visible from the outside of the crankcase 20. Therefore, the seal members 26, 27 are less deformed by pressure, for example, when a pressure difference occurs between the inside and outside of the crankcase 20. This makes it possible to prevent the formation of a path through which dust can enter around the seal members 26, 27. This makes it possible to improve the sealing performance at the dividing edges of the first crankcase 21 and the second crankcase 23.

[0057] As shown in Figs. 7 to 9, the crankcase 20 has a first cover 22 that closes the first end 20d of the cylindrical body 20a. The crankcase 20 has a second cover 24 that covers the second end 20e of the cylindrical body 20a and has an intake section 40 that allows outside air to be introduced. The first crankcase 21 has the first cover 22, and the second crankcase 23 has the second cover 24. Therefore, the first crankcase 21 and the second crankcase 23 are provided in a shape that does not divide the intake section 40. This makes it possible to prevent the formation of a path through which dust can enter the intake section 40.

[0058] 3 and 4, the crankcase 20 is divided into a first crankcase 21 and a second crankcase 23 by a plane S that is parallel to and approximately at the axial centerline K of the cylindrical first bore 20b located on the first cylinder 11a side. Therefore, the axial centerline K of the first bore 20b is located approximately at the center of the crankcase 20 in the axial direction (left-right direction) of the crankshaft 33. This allows the dividing edges of the first crankcase 21 and the second crankcase 23 to be provided with high rigidity. Furthermore, by utilizing the high rigidity of each dividing edge, the assemblability of the first crankcase 21 and the second crankcase 23 can be improved.

[0059] As shown in Figures 2 and 4, the air compressor 1 has a tank 2 that stores air compressed in the second cylinder 12a. The first crankcase 21 has a base 28 that is fastened to the tank 2. Therefore, the second crankcase 23 can be removed from the first crankcase 21 while the first crankcase 21 is connected to the tank 2 via the base 28. By removing the second crankcase 23, the crankshaft 33, the first rod 11c, the second rod 12c, etc. housed in the crankcase 20 can be repaired, replaced, etc. This improves the ease of maintenance of the air compressor 1.

[0060] As shown in Figures 2, 8 and 9, the air compressor 1 has a plurality of fasteners 25 for assembling the first crankcase 21 and the second crankcase 23. The plurality of fasteners 25 include a plurality of first bore side fasteners 25a located around the first bore 20b, and a plurality of second bore side fasteners 25b located around the second bore 20c, the number of which is greater than that of the first bore 20b. Therefore, by making the number of second bore side fasteners 25b greater than that of the first bore side fasteners 25a, the fastening strength of the second bore 20c is higher than that of the first bore 20b. Therefore, the second bore 20c can stably support the second cylinder 12a, which generates compressed air with a higher pressure than the first cylinder 11a.

[0061] Various modifications can be made to the embodiment of the present disclosure described above. For example, in the present embodiment, the intake section 40 is provided on the left side of the compression mechanism 10. Instead of this, the intake section 40 may be provided on the right side, lower part, upper part, etc. of the compression mechanism 10.

[0062] In this embodiment, the crankcase 20 is divided into the first crankcase 21 on the right side and the second crankcase 23 on the left side. Alternatively, the crankcase 20 may be divided into an upper case and a lower case.

[0063] The plane S that divides the crankcase 20 into left and right parts may be located on the axial centerline K of the first bore 20b, or may be shifted to the left or right relative to the axial centerline K. The structure in which the crankcase is divided into the first crankcase 21 and the second crankcase 23 by a single plane S has been exemplified. Instead of this, for example, the dividing surface that divides the upper part of the crankcase 20 and the dividing surface that divides the lower part of the crankcase 20 may be shifted in position in the left-right direction.

[0064] In the illustrated configuration, the first flange 21e and the second flange 23e are provided continuously in the front-rear direction from the front end of the first bore 20b to the rear end of the second bore 20c. Instead of this, the first flange 21e and the second flange 23e may be provided only around the portion where the fastener 25 is attached. Alternatively, the first flange 21e and the second flange 23e may not be provided, and the first crankcase 21 and the second crankcase 23 may be connected by, for example, a substantially C-shaped rivet fastener 25. The number of first bore side fasteners 25a and second bore side fasteners 25b that connect the first crankcase 21 and the second crankcase 23 is not limited to the illustrated number and may be changed as appropriate.

[0065] The first crankcase 21 and the second crankcase 23 are shown as being made of aluminum. Alternatively, the first crankcase 21 and the second crankcase 23 may be made of, for example, magnesium or iron. The seal members 26, 27 are shown as being made of rubber. Alternatively, the seal members 26, 27 may be made of, for example, a synthetic resin with high sealing properties. A configuration in which no seal members are interposed between the first crankcase 21 and the second crankcase 23 may be used. [Explanation of symbols]

[0066] 1. Air compressor 2...Tank, 2a...Drain cock 3...legs 3a…Side protector 4…Base 5…Handle section 6...Main body cover, 6a...Ventilation hole 7...Discharge port (for high pressure) 7a…Adjustment dial 8...Discharge port (for low pressure) 8a…Adjustment dial 9...Operation unit 10...Compression mechanism (compressor body) 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 20... crankcase, 20a... cylindrical body, 20b... first bore 20c...second bore, 20d...first end, 20e...second end, 20f...air passage 21...first crankcase, 21a...cylindrical main body divided portion, 21b...first bore divided portion 21c... second bore division portion, 21d... first division surface, 21e... first flange, 21f... screw hole 21g…Passway groove 22...first cover, 22a...bearing recess, 22b...insertion hole, 22c...screw hole 23... second crankcase, 23a... cylindrical main body divided portion, 23b... first bore divided portion 23c... second bore division portion, 23d... second division surface, 23e... second flange, 23f... insertion hole 23g…Passway groove 24... second cover, 24a... bearing recess, 24b... filter accommodating recess, 24c... protrusion 24d...through hole, 24e...air intake hole, 24f...screw boss portion, 24g...screw hole 24h…Protrusion, 24i…Screw hole 25... coupling (connecting screw), 25a... first bore side coupling, 25b... second bore side coupling 26...sealing member, 26a...insertion hole 27...sealing member, 27a...insertion hole 28…Base 29…Fixing screw 30...electric motor, 30a...rotor, 30b...stator 31...Heat dissipation fan 32…Intake fan 33... crankshaft (motor shaft), 33a, 33b... bearings, 33c... regulating plate 34…First crank section 35…Second crank section 40…Intake section 41...filter, 41a, 41b...insertion holes 42... filter cover, 42a... insertion portion, 42b... insertion hole 43: dust cover, 43a: insertion portion, 43b: insertion hole 44,45…Fixing screws 46…Air intake J: Motor axis K…Axial centerline (of first bore) L...Axial centerline (of second bore) S…Plane

Claims

1. An air compressor, comprising: a first cylinder accommodating a first piston; a second cylinder into which the air compressed in the first cylinder is introduced and which accommodates a second piston; a crankcase having a cylindrical main body accommodating a crankshaft, a first bore through which a first rod connecting the crankshaft and the first piston is inserted, and a second bore through which a second rod connecting the crankshaft and the second piston is inserted; the air compressor, wherein the crankcase has a first crankcase and a second crankcase that are assembled to each other so as to divide the cylindrical main body, divide the first bore, and divide the second bore.

2. The air compressor according to claim 1, wherein: the first crankcase has a first dividing surface extending in a single planar shape; the second crankcase has a second dividing surface extending in a single planar shape and facing the first dividing surface.

3. The air compressor according to claim 1 or 2, wherein: the first crankcase has a first flange extending outward from a dividing edge of the cylindrical main body, the first bore, and the second bore; the second crankcase has a second flange extending outward from a dividing edge of the cylindrical main body, the first bore, and the second bore; the first flange and the second flange are assembled to each other by a coupling member.

4. The air compressor according to claim 3, wherein: a seal member is provided between the first flange of the first crankcase and the second flange of the second crankcase.

5. The air compressor according to claim 1, wherein: the crankcase has a first cover closing a first end of the cylindrical main body, and a second cover covering a second end of the cylindrical main body and having an intake portion formed to allow introduction of outside air; the first crankcase includes the first cover, and the second crankcase includes the second cover.

6. The air compressor according to claim 5, wherein: the crankcase is divided into the first crankcase and the second crankcase by a plane that is parallel to an axial center line of the cylindrical first bore located on the first cylinder side and that is substantially located on the axial center line.

7. An air compressor according to claim 5 or 6, having a tank for storing the air compressed in the second cylinder, wherein the first crankcase comprises a base portion fastened to the tank. An air compressor.

8. An air compressor according to claim 1, having a plurality of connectors for assembling the first crankcase and the second crankcase, wherein the plurality of connectors includes a plurality of first bore side connectors located around the first bore and a plurality of second bore side connectors located around the second bore and having a number greater than that of the first bore side. An air compressor.

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