WO2007136168A2

WO2007136168A2 - Air compressor

Info

Publication number: WO2007136168A2
Application number: PCT/KR2007/000803
Authority: WO
Inventors: Dae Shig Kang
Original assignee: Yoosung Enterprise Co., Ltd.
Priority date: 2006-05-24
Filing date: 2007-02-15
Publication date: 2007-11-29
Also published as: WO2007136168A3; KR100783778B1; DE112007000153B4; KR20070113013A; DE112007000153T5

Abstract

The present invention relates to an air compressor in which a fuel pump or a power steering pump (40) installed to a rear side of a cover (10a) can be continuously driven even though an Operation of supplying compressed air is stopped when the pressure in an air tank for storing the compressed air to be provided to a variety of pneumatic equipment exceeds a predetermined pressure level.

Description

AN AIR COMPRESSOR Technical Field

[1] The present invention relates to an air compressor which can supply an air tank with compressed air such that the air tank for storing the compressed air to be provided to a variety of pneumatic equipment can be always maintained at a predetermined pressure level. More specifically, the present invention relates to an air compressor in which a fuel pump or a power steering pump installed to a rear side of the compressor can be continuously driven even though an operation of supplying compressed air is stopped when the pressure in an air tank exceeds the predetermined pressure level. Background Art

[2] In general, a heavy vehicle including a bus, a truck or a trailer is equipped with pneumatic equipment such as an air brake using a pressure of compressed air and an open/close actuator for automatically opening and/or closing a door using compressed air. The compressed air is supplied and stored into an air tank by means of the engine- operated air compressor and is then supplied to the pneumatic equipment. To this end, the compressed air in the air tank should be always maintained and stored at a predetermined pressure level.

[3] Fig. 1 shows an example of a general air compressor operating in the aforementioned operating manner. The air compressor is configured in the following manner. That is, since engine power is transmitted to a crankshaft c in a crankcase b mounted to an engine through a driving gear a engaged with a timing gear (not shown) to rotate the crankshaft, compressed air produced due to the operation of a piston in a pump chamber d is discharged through a discharge port e and then supplied and stored in an air tank f . If pressure in the air tank is greater than the predetermined pressure level due to such continuous operations, a portion of pressure is transmitted to an unloader h through a governor g as signal pressure, and thus, the unloader is operated to stop the compressed air from being supplied to the air tank, so that the air compressor can run idle. Further, if the pressure in the air tank is lowered as the compressed air in the air tank is consumed, the unloader is operated in reverse mode to allow compressed air to be supplied again into the air tank.

[4] However, the aforementioned air compressor is still running idle even when the unloader h prevents the compressed air from being supplied into the air tank f, power consumption of the engine is still made. Furthermore, fuel loss is increased due to the idle operation of the air compressor, and thus, it greatly runs counter to the improvement in the fuel economy of vehicles. [5] In addition, as the motions of the crankshaft c and the piston are continuously made, an internal temperature in cylinders is increased due to the factional heat and the consumption of engine oil supplied into the crankcase b is also increased. Furthermore, the atmosphere and surrounding equipment are contaminated due to hot discharged air containing a large amount of contaminants proportional to the increase in engine oil consumption. Moreover, there are problems in noise is generated and life span of the air compressor is greatly shortened due to increased wear.

[6] In order to solve the aforementioned problems, therefore, the inventors have invented an air compressor in which only a driving gear runs idle but no crankshaft and piston are operated to stop compressed air from being supplied to the air tank if the signal pressure is transmitted to an unloader when pressure in an air tank is greater than a predetermined pressure level, whereas the crankshaft and piston are again operated to supply the compressed air to the air tank if the pressure is lowered (Korean Patent Application No. 2004-13641).

[7] Figs. 2 and 3 are sectional views illustrating states where a crankshaft is moved forward or rearward in an air compressor according to a prior application of the present applicant. As shown in Fig. 2, if an engine Ia is operated in a state where a crankshaft 2 mounted in a crankcase 1 is moved forward due to a repulsion force of a ring-shaped plate spring 5 and a steel ring plate 7a and a friction ring plate 7b interposed between a clutch housing 3 and a driving gear 6 are thus brought into close contact with each other in the form of an integral unit, i.e. in a state where a clutch 7 causes the driving gear and the clutch housing to be connected with each other, power of the engine is transmitted to the crankshaft through the clutch housing via the clutch and the driving gear engaged with a timing gear (not shown) to rotate the crankshaft. As a pump piston 9a in a pump chamber 9 reciprocates through a connecting rod 9b, therefore, compressed air can be discharged through a discharge port 9c and then stored into an air tank 9d. Further, if pressure of compressed air supplied and stored in the air tank is increased above the predetermined pressure level due to such continuous operations, a portion of the compressed air serving as signal pressure is introduced into an air cylinder 8 through an inlet port 8b via a governor 9e. Then, if the introduced signal pressure is greater than the repulsion force of ring-shaped plate spring 5 for causing the crankshaft 2 to move forward, a piston 8a is pushed rearward to move the crankshaft rearward. Since the crankshaft is moved rearward to pull a push rod 4 for the ring- shaped plate spring as shown in Fig. 3, therefore, the spring is compressed so that the steel ring plate 7a and the friction ring plate 7b are thus released from the close contact state (disconnected from each other). Consequently, the connection between the driving gear 6 and the clutch housing 3 by the clutch 7 is released. Thus, even though the driving gear us continuously rotating by the engine power, the rotating force is not transmitted to the crankshaft 2 and only the driving gear runs idle.

[8] Accordingly, since the air compressor is not operated, the supply of compressed air into the air tank 8d is stopped to avoid unnecessary increase of the compressed air and also power loss of the engine Ia. Further, fuel consumption and engine oil consumption are greatly decreased and improvement in fuel economy of vehicles is also greatly achieved. Since the air compressor is operated only when necessary, the wear is lowered and thus the life span is also prevented from being shortened. Furthermore, since the temperature of discharged air is lowered due to reduction in internal friction heat and thus the hot air is not discharged when the compressor comes to a standstill, there is an advantage in that contamination in the atmosphere and surroundings are reduced.

[9] Such a prior invention allows the fuel and engine oil consumption to be greatly reduced. Since a fuel pump or a power steering pump is mounted to a rear end of a crankshaft of an air compressor to be operated together with the crankshaft in most of heavy vehicles (e.g., trucks and buses), however, the fuel or power steering pump is also not operated when the power is disconnected by the clutch to stop the air compressor from being operated. Therefore, there is a problem in that the fuel or power steering pump cannot be mounted the rear end of the crankshaft. As a result, there is another problem in that engine arrangement is very complicated and the number of parts and man-hour are increased in order to install the fuel or power steering pump such that the pump can be operated even when the air compressor is not operated. Disclosure of Invention Technical Problem

[10] The present invention is conceived to solve the aforementioned problems in the prior invention. An object of the present invention is to provide an air compressor wherein a fuel or power steering pump is operated even though a pump piston is stopped.

[11] Another object of the present invention is to provide an air compressor wherein a crankshaft and a connecting rod can be very simply and easily manufactured and assembled and fuel and oil consumption in an engine can also be minimized. Technical Solution

[12] The above objects of the present invention are achieved by providing an air compressor in which a driving force of a driving gear can be transmitted to a fuel or power steering pump through a driving shaft even in a state where the operation of a crankshaft and a piston is stopped and the supply of compressed air is thus stopped when pressure in an air tank exceeds a predetermined pressure level and signal pressure is transmitted. [13] The air compressor of the present invention comprises a crankcase formed with a pump chamber perpendicular to a crank chamber at a specific position thereof; a driving shaft formed with a driving gear rotatably engaged with a timing gear of an engine at a front end thereof exposed forward through a front surface of the crankcase; a crankshaft tube through which portions of the driving shaft received within the crank chamber but excluding a rear portion of the driving shaft are penetrated and connected and which includes an eccentric portion formed on an outer circumferential surface thereof corresponding to the pump chamber to be coupled with a connecting rod of a pump piston; a coupling for coupling a rear end of the driving shaft and a front end of a movable shaft of a fuel or power steering pump installed to a rear surface of a cover installed to cover an exposed rear end of the crankcase, the front end of the movable shaft being introduced into the crank chamber through the cover; a clutch installed between the rear portion of the driving shaft and a rear end of the crankshaft tube to allow or prevent a driving force of the driving shaft to be or from being transmitted to the crankshaft tube; and an air cylinder installed at a rear portion in the crank chamber directly in front of the clutch to stop the clutch from being operated when signal pressure is applied through an injection port or to allow the clutch to be operated when the signal pressure is not applied. Normally, the driving shaft and the crankshaft tube are connected to be rotatable together with each other by the clutch, and thus, the pump piston is operated to supply the air tank with the compressed air. If the pressure in the air tank exceeds the predetermined pressure level, however, the signal pressure is introduced into the air cylinder to stop the operation of the clutch. Therefore, the driving force is prevented from being transmitted to the crankshaft tube and the pump piston is thus stopped, but the fuel or power steering pump can be continuously operated because the movable shaft is coupled with the rear end of the driving shaft through the coupling.

Advantageous Effects

[14] According to the present invention, an air compressor has the following advantages.

[15] If a driving force of a driving shaft is transmitted to a crankshaft tube by means of a clutch, a pump piston is operated such that an air tank is supplied with compressed air and a fuel or power steering pump is operated. If internal pressure of the air tank is increased above a predetermined pressure level, an air cylinder is operated such that the clutch is disengaged to prevent the driving force of the driving shaft from being transmitted to a crankshaft tube and thus to prevent a pump chamber from being operated. Since the driving force of the driving shaft is still transmitted to a movable shaft even in such a case, however, the fuel or power steering pump is normally operated. [16] Accordingly, there is an advantage in that fuel loss, noise generation, contaminant discharge and the like can be greatly reduced, because the pump is not operated when the supply of compressed air is stopped. Furthermore, there is another advantage in that a crankshaft and a connecting rod can be very simply and easily manufactured and assembled due to simplified structure thereof as compared with an air compressor according to a prior invention.

Brief Description of the Drawings

[17] Fig. 1 is a schematic view showing the configuration of an example of a general air compressor.

[18] Figs. 2 and 3 are sectional views showing an operating state of an air compressor according to a prior application.

[19] Fig. 4 is a sectional view of an air compressor according to an embodiment of the present invention.

[20] Fig. 5 is an enlarged sectional view illustrating a state a clutch is engaged in the air compressor of Fig. 4.

[21] Fig. 6 is an enlarged sectional view illustrating a state a clutch is disengaged in the air compressor of Fig. 4.

[22] Fig. 7 is an enlarged view of a clutch of the air compressor according to the present invention. Best Mode for Carrying Out the Invention

[23] Hereinafter, an air compressor according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[24] Fig. 4 is a sectional view of an air compressor according to an embodiment of the present invention, Fig. 5 is an enlarged sectional view illustrating a state a clutch is engaged in the air compressor of Fig. 4, Fig. 6 is an enlarged sectional view illustrating a state a clutch is disengaged in the air compressor of Fig. 4, and Fig. 7 is an enlarged view of a clutch of the air compressor according to the embodiment of the present invention.

[25] The air compressor of the present invention comprises a crankcase 10 installed with a front surface attached to a relevant position of an engine A and provided with a crank chamber 11 ; a pump chamber 20 installed to be perpendicular to the crank chamber at a specific position of the crankcase; a driving shaft 30 formed with a driving gear 31 rotatably engaged with a timing gear of the engine (not shown) at a front end thereof exposed forward through a hole formed on the front surface of the crankcase; a fuel or power steering pump 40 installed to an a rear surface of a cover 10a to allow a front end of a movable shaft 41 thereof to be introduced into the crank chamber through a t hrough-hole of the cover installed to cover an exposed rear end of the crankcase and thus to engaged and driven with the driving shaft using a coupling 32; a crankshaft tube 50 through which portions of the driving shaft received within the crank chamber but excluding a splined portion 33 formed on the rear end of the driving shaft are penetrated and connected and which includes an eccentric portion 51 formed on an outer circumferential surface thereof corresponding to the pump chamber to be coupled with a connecting rod 22 of a pump piston 21 ; a clutch 60 installed between the rear portion of the driving shaft and a rear end of the crankshaft tube to allow or prevent a driving force of the driving shaft to be or from being transmitted to the crankshaft tube; and an air cylinder 70 installed at a rear portion in the crank chamber directly forward of the clutch to stop the clutch from being operated when signal pressure is applied through an injection port 71 or to allow the clutch to be operated when the signal pressure is not applied.

[26] Bushings are interposed between an inner circumferential surface of the hole formed on the front surface of the crankcase 10 and an outer circumferential surface of a front end of the driving shaft 30 penetrating through the hole and on inner circumferential surfaces of the front and rear ends of the crankshaft tube 50 coupled with the driving shaft, respectively, so that the driving shaft and the crankshaft tube can be smoothly rotated.

[27] Further, a portion of the driving shaft 30 which is received within the crank chamber 11 has a diameter smaller than that of the front end of the driving shaft penetrated through the through-hole such that the crankshaft tube 50 cannot be slipped forward, whereas a rear portion of the crankshaft tube where a cylinder portion 72 of the air cylinder 70 is engaged has an outer diameter smaller than that of a front end thereof such that the crankshaft tube cannot be slipped rearward either.

[28] Therefore, the crankshaft tube 50 is always rotated at a predetermined position without any forward and rearward slip in a state where it is coupled with the driving shaft 30, and thus, a bearing portion 23 of the connecting rod 22 coupled with the eccentric portion 51 is not deviated from the eccentric portion. Accordingly, the reciprocating motion of the pump piston 21 can be normally achieved.

[29] The fuel or power steering pump 40 can be driven even when the driving force of the driving shaft is not transmitted using the clutch 60, because a front end of the pump is in direct connection with the rear end of the driving shaft 30 through the coupling 32.

[30] The clutch 60 comprises a clutch wheel 61 which is coupled with the splined portion 33 formed on the outer circumferential surface of the driving shaft 30 not to be slipped in a forward or rearward direction by means of a snap ring and is formed with an inner spline 611 engaged with the splined portion at an inner circumferential surface thereof and an outer spline 612 at an outer circumferential surface thereof; a fixed clutch plate 62 including an inner spline 622 formed on an inner circumferential surface of a shaft tube 621 and engaged with a rear portion of an outer spline 52 formed on an outer circumferential surface of the rear end of the crankshaft tube 50 to allow a rear end thereof to be caught to a snap ring installed at a rear portion of the outer spline 52 and thus not to be moved rearward and a fixed piece 623 extending around the rear end of the outer circumferential surface thereof to extend in a direction normal to the outer circumferential surface; a cylindrical clutch housing 63 including an inner spline 631 formed on an inner circumferential surface of a hole at a front end thereof and engaged with an intermediate portion of the outer spline and another inner spline formed on an inner circumferential surface of a rear portion thereof with an inner diameter greater than the outer diameter of the fixed piece of the fixed clutch plate; a plurality of ring-shaped plate springs 64 mounted in a space defined between the fixed piece of the fixed clutch plate and a front surface of the clutch housing by the shaft tube; a movable clutch ring plate 65 having an inner diameter greater than a diameter of the clutch wheel and an outer diameter equal to the inner diameter of the rear end of the clutch housing and installed inside of the rear end of the clutch housing to allow a rear end on an outer circumferential surface thereof to be caught to a snap ring 651 installed on the inner surface of the rear end of the clutch housing and thus not to be separated rearward; a plurality of friction ring plates 66 each being mounted one by one in a space defined between the fixed and movable clutch plates and between the clutch wheel and the clutch housing, sized to have an outer diameter spaced apart from the inner spline of the clutch housing by a predetermined gap and formed with an interlocking spline 66a engaged with the outer spline of the clutch wheel at an inner circumferential surface of a hole; and a plurality of steel ring plates 67 each being mounted one by one in a space defined between the fixed and movable clutch plates and between the clutch wheel and the clutch housing, sized to have an inner diameter spaced apart from the outer spline of the clutch wheel by a predetermined gap and formed with a power transmission spline 67a engaged with the inner spline of the clutch housing at an outer circumferential surface thereof, wherein the plurality of friction ring plates or the plurality of steel ring plates are alternately interposed between the other adjacent plates.

[31] Therefore, when the clutch housing 63 is urged forward due to a repulsion force of the plurality of ring-shaped plate springs 64, the movable clutch ring plate 65 mounted in the rear portion of the clutch 60 is moved forward together with the clutch housing. Accordingly, the alternately arranged friction and steel ring plates 66 and 67 are moved also forward by an interval corresponding to a moving distance of the clutch housing. At this time, the repulsion force of the ring-shaped plate spring is also exerted on the fixed clutch plate 62 in a rearward direction, and thus, the friction and steel ring plates are brought into close contact with one another in the form of a single body because the fixed clutch plate is stationary.

[32] If the driving shaft is driven in such a state, the driving force is transmitted to the friction ring plates 66 through the interlocking spline 66a engaged with the outer spline 612 of the clutch wheel 61. Then, the force is transmitted to the clutch housing 63 by means of the inner spline 632 engaged with the power transmission spline 67a because the friction ring plates are brought into close contact with the steel ring plates 67 in the form of a single body. Therefore, since the clutch housing is driven, the force is transmitted to the outer spline 52 engaged with the inner spline 631 such that the crankshaft tube 50 can be driven.

[33] If the crankshaft tube 50 is driven in such a way, the pump piston 21 reciprocates in the pump chamber 20 by means of the connecting rod 22 connected with the eccentric portion 51 through the bearing 23. Thus, compressed air produced as such is discharged through the discharge port 24 and then supplied and stored in the air tank (not shown).

[34] If the pressure of the compressed air stored in the air tank in such a way is increased above the predetermined pressure level, a portion of the pressure is applied through the injection port 71 in the form of signal pressure such that the air cylinder 70 is operated to urge or push the clutch housing 63 in a rearward direction. At this time, since the fixed clutch plate 62 is supported by the snap ring such that a rear portion thereof is not slipped rearward, the movable clutch ring plate 65 is also moved rearward together with the clutch housing while the ring-shaped plate spring 64 is compressed.

[35] Therefore, an interval between the fixed and movable clutch plates 62 and 65 is increased, and thus, the friction and steel ring plates 66 and 67 are released from their close contact state. Accordingly, even though the friction ring plates are rotated together with the clutch wheel 61, the rotating force is not transmitted to the steel ring plates to allow the friction ring plate to be slipped with respect to the steel ring plate and thus to run idle. Consequently, since the driving force of the driving shaft 30 is not transmitted to the crankshaft tube 50, the operation of the pump piston 21 is stopped to thereby stop compressed air from being supplied into the air tank.

[36] Since the driving force is transmitted to the movable shaft 41 directly coupled with the rear end of the driving shaft 30 through the coupling 32 even in such a state, however, the fuel or power steering pump will be still operated.

[37] The air cylinder 70 is installed directly forward of the clutch 60 within the crank chamber 11 in such a manner that only a portion provided with the injection port 71 through which the signal pressure corresponding to a portion of the compressed air is introduced is exposed to the outside through between the pump chamber 20 and the cover 10a. The air cylinder 70 comprises the cylinder portion 72 provided with the injection port and installed rearward of the clutch 60 within the crank chamber 11, and a piston 73 mounted in the rearward open cylinder portion and coupled to the crankshaft tube 73 to be movable in a forward or rearward direction within a predetermined degree.

[38] Further, a bearing 70a is interposed between a rear surface of the piston 73 and a front surface of the clutch housing 63 to allow an interval between them to be kept constant and also the clutch housing to be smoothly rotated and supported.

[39] The air cylinder 70 so configured is operated as follows. If the pressure of the compressed air is greater than the predetermined pressure level and is thus applied into the cylinder portion 72 through the injection port 71 in the form of signal pressure, the piston 73 is moved rearward together with the clutch housing 63. Therefore, as the ring-shaped plate springs 64 are compressed and the friction and steel ring plates 66 and 67 are separated from one another, the transmission of the driving force of the driving shaft 30 by the clutch 60 is cut off to stop the crankshaft tube 50 from being driven.

[40] As the compressed air stored in the air tank is consumed, the pressure is lowered and the internal pressure of the air cylinder 70 is thus decreased below the repulsion force of the ring-shaped plate springs 64. Thus, since the clutch housing 63 is moved forward due to the repulsion force of the ring-shaped plate springs 64, the piston 73 is also moved forward. Further, since the movable clutch ring plate 65 causes the friction and steel ring plate 66 and 67 to be urged forward and brought into close contact with each other, the driving force of the driving shaft 30 is transmitted to the crankshaft tube 50 by means of the clutch 60 to allow the pump piston 21 to be driven and thus the operation of supplying the compressed air to be again performed.

[41] In such a operating process, an interval where the piston 73 of the air cylinder 70 is moved in a forward or rearward direction is determined to such a degree that the clutch housing 50 is moved forward by the repulsion force of the ring-shaped plate springs 64 to allow the friction and steel ring plates 66 and 67 to be brought into close contact with one another as a single body and thus to be rotated together.

[42] Furthermore, in order to absorb shock produced by the pressure and the like applied to the air cylinder 70 while the clutch 60 is engaged or disengaged, a thrust bushing 75 is interposed between a front end of the cylinder 70 and a fixed ring 74 coupled to the crankshaft tube 50 to support the front end of the cylinder portion 72.

[43] Further, in order to operate the piston 73 in an equilibrium state, a plurality of coil springs 76 and guide pins 77 for the rotation prevention are arranged at a suitable interval between the piston 73 and the cylinder portion 72.

[44] Although it has been illustrated in Fig. 4 showing an embodiment of the present invention that a plurality of pump chambers 20 are installed, a single pump chamber is preferably employed for the cost reduction in the case of a vehicle where rapid and large supply of compressed air is not required due to low consumption of the compressed air. In such a case, one pump piston 21, one connecting rod 22 and one eccentric portion 51 may be installed in an embodiment where a single pump chamber is employed.

[45] Although an embodiment where a single pump chamber 20 is employed has not been illustrated in the accompanying drawings, it can be simply modified from an embodiment where a plurality of pump chambers are installed and can thus be omitted herein. It is apparent to those skilled in the art that the foregoing will be included within the scope of the present invention.

Claims

[1] An air compressor, comprising: a driving shaft mounted in a crank chamber of a crankcase installed to an engine formed with a driving gear rotatably connected at the front end thereof exposed forward through a hole provided on the front surface of the crankcase; a pump chamber installed to be perpendicular to the crank chamber within the crankcase and provided with a discharge port for compressed air; a fuel or power steering pump installed to the rear surface of a cover installed to the exposed rear end of the crankcase and provided with a movable shaft to allow the front end of the movable shaft to be introduced into the crank chamber through a through-hole formed in the cover and to be directly coupled with the rear end of the driving shaft with a coupling; a crankshaft tube connected with portions of the driving shaft received within the crank chamber but excluding the rear portion of the driving shaft and formed with an eccentric portion connected with a bearing portion of a connecting rod of a pump piston mounted in the pump chamber at a portion on an outer circumferential surface thereof corresponding to the pump chamber; a clutch installed between the rear portion of the driving shaft and the rear end of the crankshaft tube to prevent a driving force of the driving shaft from being transmitted to the crankshaft tube when pressure of compressed air supplied from the pump chamber and stored in an air tank is increased above a predetermined pressure level and allow the driving force to be transmitted to the crankshaft tube when the pressure of the compressed air is decreased below a predetermined pressure level; and an air cylinder installed within the crank chamber directly in front of the clutch to stop the clutch from being operated when the pressure of compressed air supplied and stored in the air tank is increased above the predetermined pressure level and a portion of the pressure is introduced through an injection port as signal pressure.

[2] The air compressor as claimed in claim 1, wherein the clutch comprises: a clutch wheel coupled with a splined portion formed on the outer circumferential surface of the driving shaft and formed with the inner spline engaged with the splined portion at the inner circumferential surface thereof and an outer spline at the outer circumferential surface thereof; a fixed clutch plate including an inner spline formed on the inner circumferential surface of a shaft tube and engaged with a rear portion of an outer spline formed on the outer circumferential surface of the rear end of the crankshaft tube and a fixed piece extending around the rear end of the outer circumferential surface thereof; a cylindrical clutch housing including an inner spline formed on the inner circumferential surface of a hole at the front end thereof and engaged with the intermediate portion of the outer spline and another inner spline formed on the inner circumferential surface of the rear portion thereof with an inner diameter greater than an outer diameter of the fixed piece of the fixed clutch plate; a plurality of ring-shaped plate springs mounted in a space defined between the fixed piece of the fixed clutch plate and the front surface of the clutch housing in proportion to the length of the shaft tube; a movable clutch ring plate having the inner diameter greater than the diameter of the clutch wheel and an outer diameter equal to the inner diameter of the rear end of the clutch housing and installed inside of the rear end of the clutch housing; a plurality of friction ring plates each being mounted one by one in a space defined between the fixed and movable clutch plates and between the clutch wheel and the clutch housing, sized to have an outer diameter spaced apart from the inner spline of the clutch housing by a predetermined gap and formed with an interlocking spline engaged with the outer spline of the clutch wheel at the inner circumferential surface of a hole; and a plurality of steel ring plates each being mounted one by one in a space defined between the fixed and movable clutch plates and between the clutch wheel and the clutch housing, sized to have the inner diameter spaced apart from the outer spline of the clutch wheel by a predetermined gap and formed with a power transmission spline engaged with the inner spline of the clutch housing at the outer circumferential surface thereof, wherein the plurality of friction ring plates or the plurality of steel ring plates are alternately interposed between the other adjacent plates.

[3] The air compressor as claimed in claim 1 or 2, the air cylinder comprises a cylinder portion installed rearward of and around the crankshaft tube and a piston mounted in the cylinder portion and coupled to the crankshaft tube so as to be movable in a forward or rearward direction, wherein the air cylinder is installed directly forward of the clutch within the crank chamber in such a manner that only a portion provided with the injection port through which the signal pressure corresponding to the compressed air is introduced may be exposed to the outside through between the pump chamber and the cover.

[4] The air compressor as claimed in claim 3, wherein the air cylinder is provided with a plurality of coil springs and interval maintaining pins arranged at a suitable interval between the piston and the cylinder portion. [5] The air compressor as claimed in claim 1 or 2, wherein a bearing is interposed between a rear surface of the piston of the air cylinder and a front surface of the clutch housing. [6] The air compressor as claimed in claim 1 or 2, wherein a thrust bushing is interposed between a front end of the cylinder portion of the air cylinder and a fixed ring coupled to the crankshaft tube to support the front end of the cylinder portion. [7] The air compressor as claimed in claim 1 or 2, wherein a plurality of pump chambers are installed.