JP2016050516A - air compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air compressor capable of enhancing cooling performance of a compression mechanism part.SOLUTION: In a crankcase, an internal fan 41 being blade elements is disposed on a non-compression mechanism part side of a flywheel 40. Each blade 41b of the internal fan 41 is positioned on or extended to a further peripheral side than bearings 36a, 36b of a compression mechanism part 7. A pair of vent holes 42a are formed to penetrate a flat plate part 49 of the flywheel 40 and a flat plate part 41a of the internal fan 41. In addition, a pair of vent holes 42b are formed further inside than the vent holes 42a to penetrate the flat plate part 41a of the internal fan 41, the flat plate part 49 of the flywheel 40, an eccentric collar 37b, a spacer 38b, a spacer 38a and an eccentric collar 37a in the axial direction. Furthermore, a vent hole 43a is formed in a first connecting rod 33a, and a vent hole 43b is formed in a second connecting rod 33b.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an air compressor suitable for generating compressed air necessary for driving an air tool such as a nail driver.

  In construction sites and the like, portable pneumatic tools for driving nails and screws into wood with compressed air pressure are widely used. In general, an air compressor that drives a pneumatic tool or the like converts the rotational motion of the rotating shaft of a driving unit such as a motor into the reciprocating motion of a piston in a cylinder via the crank shaft of the compressing portion, and the reciprocating motion of the piston The air sucked from the intake valve of the cylinder is configured to be compressed. The compressed air compressed in the cylinder is discharged from the exhaust valve of the cylinder through the pipe to the air tank and stored in the air tank. When compressing a gas to a high pressure, a multistage reciprocating compressor that increases the pressure stepwise is generally used. The high-pressure compressed air stored in the air tank is adjusted to an appropriate pressure by a pressure reducing valve attached to the air tank, and supplied to an air tool or the like via an air hose. Such an air compressor is disclosed in Patent Document 1, for example.

JP2013-40586A

  The compression mechanism part arrange | positioned in a crankcase is cooled by the airflow which generate | occur | produces in a crankcase, when the counterweight provided with a compression mechanism part rotates. However, in recent air compressors, the temperature rise of the compression mechanism has increased with the demand for higher output (higher discharge force) and smaller size, and the cooling effect has been insufficient.

  The present invention has been made in view of these circumstances, and an object thereof is to provide an air compressor capable of improving the cooling performance of the compression mechanism.

One embodiment of the present invention is an air compressor. This air compressor
An air tank for storing compressed air;
A compression unit that compresses air sucked from outside and supplies the compressed air to the air tank;
A drive source for driving the compression unit,
The compression part includes a crankcase, and a compression mechanism part disposed in the crankcase,
The compression mechanism is provided with a vent hole penetrating in the axial direction.

  An inertial body that rotates together with the compression mechanism portion in the crankcase may be provided, and the inertial body may have a flat plate portion having a diameter larger than the eccentric collar of the compression mechanism portion.

  The inertial body may have a vent hole adjacent to the compression mechanism and communicating with the vent hole.

  The vent may include a vent provided on an inner peripheral side from a bearing of the compression mechanism portion.

  The vent may include a vent provided on the outer peripheral side of the bearing of the compression mechanism.

  The vent may include a vent provided in a rod connected to the piston of the compression mechanism.

  The compression mechanism section is a crank mechanism configured by an eccentric collar attached to a rotation shaft of the drive source and a connecting rod provided on an outer periphery of the eccentric collar via a bearing, and the vent hole is arranged as the eccentric shaft. You may form in a color.

  The vent hole may also be formed in the connecting rod.

  The crankcase may include a blade element that sucks air from the compression mechanism portion side to the inner peripheral portion thereof and sends air from the outer peripheral portion to the compression mechanism portion side.

  You may have a guide air path which guides the airflow which the said blade | wing element generate | occur | produced in the said crankcase to the said compression mechanism part side.

  The guide air passage may be formed by an inner wall of the crankcase.

  You may arrange | position the said blade | wing element adjacent to the said compression mechanism part.

  A flywheel may be provided adjacent to the vane element.

  The flywheel may be interposed between the blade element and the compression mechanism.

  An intake passage inlet to the cylinder of the compression portion may be opened on or in the vicinity of the radial extension of the blade element.

  An intake port that communicates the inside and outside of the crankcase may be formed on the non-compression mechanism portion side of the blade element.

  The air inlet may be in close proximity to the negative pressure generating portion of the blade element.

  The blade element may include a flat plate portion and a centrifugal blade rising from the flat plate portion, and a vent hole may be formed in the flat plate portion.

  The blade element may include a hub and an axial flow type blade extending from the hub to the outer peripheral side, and a vent hole may be formed in the hub.

  The number of blades may be greater in some areas in the circumferential direction than in other areas.

  Each of the blades constituting the blade element may be positioned on the outer peripheral side or extend from the bearing of the compression mechanism unit.

  It should be noted that any combination of the above-described constituent elements, and those obtained by converting the expression of the present invention between methods and systems are also effective as aspects of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the air compressor which can improve the cooling performance of a compression mechanism part can be provided, As a result, a more compact, lightweight, and cheap air compressor can be provided.

1 is a perspective view of an air compressor 1 according to Embodiment 1 of the present invention. 1 is a horizontal sectional view of an air compressor 1. FIG. The AA fragmentary sectional view of FIG. The BB partial sectional view of FIG. FIG. 3 is an exploded perspective view of the compression mechanism unit 7, the flywheel 40, and the inner fan 41 of the air compressor 1. The horizontal sectional view of the air compressor concerning Embodiment 2 of the present invention. The vertical fragmentary sectional view containing the motor rotating shaft 5 of the air compressor which concerns on Embodiment 3 of this invention. The perspective view of the internal fan 41 of FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent component, member, etc. which are shown by each drawing, and the overlapping description is abbreviate | omitted suitably. In addition, the embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

Embodiment 1
FIG. 1 is a perspective view of an air compressor 1 according to Embodiment 1 of the present invention. FIG. 2 is a horizontal sectional view of the air compressor 1. 3 is a partial cross-sectional view taken along line AA of FIG. 4 is a partial cross-sectional view taken along line BB in FIG. FIG. 5 is an exploded perspective view of the compression mechanism unit 7, the flywheel 40, and the inner fan 41 of the air compressor 1.

  The air compressor 1 is arranged in parallel at a predetermined interval, a pair of air tanks 2a and 2b for storing compressed air, and a compression unit that compresses air sucked from the outside and supplies the air to the air tanks 2a and 2b 3 and a motor 4 as a drive source that is connected to the compression unit 3 and drives the compression unit 3, and the motor 4 is arranged so that the axial direction of the motor 4 is substantially orthogonal to the longitudinal direction of the air tanks 2a and 2b. The compression part 3 is arrange | positioned above a pair of air tank 2a, 2b.

  As shown in FIG. 2, the motor rotating shaft 5 passes through the compression portion 3, and a cooling fan 8 a (first cooling fan) is provided at the motor side end of the motor rotating shaft 5, and the non-motor side end portion Is provided with a cooling fan 8b (second cooling fan). The cooling fans 8a and 8b rotate integrally with the motor 4.

  As shown in FIG. 1, the air compressor 1 is provided with pressure reducing valves 9a and 9b, pressure gauges 10a and 10b for displaying the pressure of the compressed air having been reduced, and couplers 11a and 11b serving as compressed air outlets. It is done. By connecting the couplers 11a and 11b and a pneumatic tool such as a nailing machine (not shown) by a high-pressure air hose (not shown), an operator can operate the pneumatic tool using compressed air and perform appropriate work. Become.

  As shown in FIG. 2, the air tanks 2a and 2b have pressure control valves for discharging a part of compressed air to prevent damage to the main body when the pressure becomes higher than a predetermined value. 12 and a drain discharge device 13 are provided. The drain discharge device 13 has an operation unit 14, and by operating the operation unit 14, the compressed air and moisture in the air tanks 2 a and 2 b can be appropriately discharged to the outside.

  As shown in FIG. 2, the compression unit 3 is provided with a crank mechanism inside, and the rotational movement of the motor rotating shaft 5 is caused by the first piston 34a and the second piston 34b via the first connecting rod 33a and the second connecting rod 33b. Each is converted into a reciprocating motion. The first piston 34a is accommodated in the first cylinder 15a and the first cylinder head 16a. The second piston 34b is accommodated in the second cylinder 15b and the second cylinder head 16b. The first cylinder 15a and the second cylinder 15b are horizontally opposed to each other with the motor rotating shaft 5 interposed therebetween, and are arranged substantially parallel to the air tanks 2a and 2b in the example of the present embodiment. When external air is sucked in the compression unit 3, the air is first compressed by the first cylinder 15 a (low pressure side cylinder), and the air compressed by the first cylinder 15 a passes through the pipe 19 to the second cylinder 15 b (high pressure side cylinder). ) And further compressed by the second cylinder 15b is supplied to the air tank 2a through a pipe (not shown). The air tanks 2a and 2b are connected to each other by a connecting pipe (not shown), and the pressures of the air tanks 2a and 2b are in a balanced state.

  As shown in FIG. 2, the control circuit 21 (control circuit board) for driving the motor 4 is disposed to face the cooling fan 8b on the non-motor side of the compression unit 3, and is fixed to the air tank 2b. The motor 4 is a DC brushless type motor as a preferred example, and includes a stator coil 23, a rotor 24 disposed inside the stator coil 23, and a hall element substrate 25 that detects the rotational position of the rotor 24. The inverter is controlled by the control circuit 21. The control circuit 21 includes a semiconductor switching element for inverter control and the like, and is cooled by the cooling fan 8b.

  As shown in FIG. 1, a cover 26 that covers components of the air compressor such as the compressor 3, the motor 4, and the control circuit 21 is disposed above the air tanks 2a and 2b, and is fixed to the air tanks 2a and 2b. . Grip portions 31a and 31b for carrying the air compressor 1 are provided at both longitudinal ends of the air tanks 2a and 2b. The cover 26 is provided with an operation panel 28 having a power switch or the like (not shown) for operating the air compressor 1. The cover 26 is provided with air windows 29a and 29b (FIG. 2) on the wall surfaces facing the cooling fans 8a and 8b. The air tanks 2a and 2b are provided with leg portions 32 for preventing and protecting from direct contact with the ground.

  During such operation of the air compressor 1, the motor 4 is alternately subjected to a compression load when air is compressed by the reciprocating motion of the first piston 34a and the second piston 34b. Therefore, load current is generated in the stator coil 23 and the control circuit 21, and the temperature rises due to Joule heat accompanying the load current. The first piston 34a and the second piston 34b, the first cylinder 15a and the first cylinder head 16a, and the second cylinder 15b and the second cylinder head 16b rise in temperature due to the compression heat of the compressed air. The first connecting rod 33a and the second connecting rod 33b connected to the first piston 34a and the second piston 34b also rise in temperature, and the bearings (described later) of the first connecting rod 33a and the second connecting rod 33b also rise in temperature due to friction. The temperature of the pipe 19 and the air tanks 2a and 2b also rises because the compressed air whose temperature has risen due to the compression heat flows. Therefore, it is necessary to suppress the temperature rise of each part by cooling. Hereinafter, a configuration related to cooling will be described.

(Cooling by cooling fan 8a)
In FIG. 2, when the motor 4 is operated, the cooling fan 8a rotates, so that the motor 4 to the first cylinder 15a, the first cylinder head 16a, the second cylinder 15b, and the second cylinder are passed through the cooling fan 8a from the air window 29a. Cooling air toward the head 16b is supplied, and the temperature rise of each part is suppressed.

(Cooling by cooling fan 8b)
In FIG. 2, a control circuit 21 is disposed opposite to the cooling fan 8 b attached to the non-motor side end of the motor rotating shaft 5. When the motor 4 is operated, the cooling fan 8b rotates, whereby outside air is sucked from the wind window 29b, a cooling airflow is generated in the vicinity of the control circuit 21, and the temperature rise of the control circuit 21 is suppressed.

(Crankcase 17 internal cooling)
As shown in FIG. 5, in the compression mechanism part 7, the 1st connecting rod 33a is comprised as a crank mechanism by being attached to the motor rotating shaft 5 via the bearing 36a and the eccentric collar 37a. The second connecting rod 33b is configured as a crank mechanism by being attached to the motor rotating shaft 5 via a bearing 36b and an eccentric collar 37b. Spacers 38a and 38b are disposed between the eccentric collar 37a and the eccentric collar 37b. A flywheel 40 is provided adjacent to the second connecting rod 33b. The flywheel 40 includes a flat plate portion 49 and a counterweight portion 46 in which the center of gravity is unevenly distributed. The counterweight portion 46 rises from a part of the outer edge of the flat plate portion 49 toward the non-compression mechanism portion. An internal fan 41 that is a blade element is disposed on the non-compression mechanism portion side of the flywheel 40. The internal fan 41, the flywheel 40, the eccentric collar 37b, the spacer 38b, the spacer 38a, and the eccentric collar 37a are fastened (fixed) to each other by the screw material 6, attached to the motor rotating shaft 5, and the key 39 (FIG. 4). Thus, the motor rotates together with the motor rotating shaft 5.

  The internal fan 41 is a centrifugal fan in the present embodiment, and includes a flat plate portion 41a and a plurality of centrifugal blades 41b rising from the flat plate portion 41a. Each blade 41b is located on the outer peripheral side or extends from the bearings 36a, 36b of the compression mechanism section 7. A pair of vent holes 42 a is formed so as to penetrate the flat plate portion 49 of the flywheel 40 and the flat plate portion 41 a of the internal fan 41. In addition, the flat plate portion 41a of the internal fan 41, the flat plate portion 49 of the flywheel 40, the eccentric collar 37b, the spacer 38b, the spacer 38a, and the eccentric collar 37a are arranged in the axial direction (parallel to the motor rotating shaft 5) inside the air vent 42a. A pair of vent holes 42b are formed so as to penetrate in the direction). Further, a vent hole 43a is formed in the first connecting rod 33a, and a vent hole 43b is formed in the second connecting rod 33b. The outer periphery of the internal fan 41 is covered by the crankcase 17 and the bush 18 and guides the airflow generated by the internal fan 41 to the compression mechanism section 7 side (only the airflow toward the compression mechanism section 7 side is allowed). An air passage 47 (FIGS. 2 and 3) is formed.

  As shown in FIGS. 2 to 3, when the motor rotating shaft 5 rotates, the airflows CA <b> 1 and CA <b> 2 sucked into the inner peripheral portion of the internal fan 41 from the motor 4 side through the vent holes 42 a and 42 b when the motor rotation shaft 5 rotates. Occurs. As a result, airflow is circulated to every corner of the crankcase 17 and the compression mechanism 7 is reliably cooled. Further, on the outer periphery of the internal fan 41, an air flow CA3 toward the compression mechanism portion 7 is generated via the guide air passage 47, and the first piston 34a and the second piston 34b are reliably cooled. Further, the airflows CA1 and CA3 are formed more smoothly by the vent holes 43a and 43b, the circulation of the airflow is promoted, and the cooling effect is increased.

(Improving inhalation efficiency)
In FIG. 3, a crankcase cover 17 a is provided in the non-motor side opening of the crankcase 17 (on the non-compression mechanism portion side of the internal fan 41). The crankcase cover 17a is formed with an intake port 35 that allows the inside of the crankcase 17 to communicate with the outside air. A filter element 22 and a filter cover 27 are attached between the intake port 35 and the outside air. The crankcase cover 17a is in close proximity to the internal fan 41, and the intake port 35 is in close proximity to the negative pressure generating portion of the internal fan 41 (inner peripheral portion of the internal fan 41). On the other hand, as shown in FIG. 4, an intake passage 45 is integrally formed in the first cylinder 15a, and the intake passage entrance 44 is located on the outer peripheral side of the internal fan 41 (the portion into which the air flow generated by the internal fan 41 flows). 17 is formed.

  In FIG. 4, when the motor rotating shaft 5 rotates and the first piston 15a moves toward the bottom dead center, the pressure in the first compression chamber 48a decreases, and a reed valve (not shown) is opened to open the intake passage 45. The intake air IN2 is supplied to the first compression chamber 48a. Further, since the pressure in the crankcase 17 decreases, outside air is supplied into the crankcase 17 via the filter element 22 and the intake port 35 as in the intake air IN1 (FIG. 3). By the above operation, outside air is supplied to the first compression chamber 48a. At this time, since the internal fan 41 is also rotating simultaneously, the pressure on the outer peripheral side of the internal fan 41 increases and the pressure on the inner peripheral side of the internal fan 41 decreases. Therefore, the internal fan 41 strengthens the intake air IN1 by the suction negative pressure, and a part of the airflow CA3 flows into the intake passage 45 to strengthen the intake air IN2, thereby increasing the amount of air supplied to the first compression chamber 48a. There is also an effect of increasing the discharge amount of the compressor 1.

  According to the present embodiment, the following effects can be achieved.

(1) An internal fan 41 is provided in the crankcase 17, and the internal fan 41 sucks air from the compression mechanism 7 side to its inner peripheral part and sends air from its outer peripheral part to the compression mechanism part 7 side. Therefore, the cooling air can be circulated in the crankcase 17 and the cooling performance of the compression mechanism section 7 can be improved.

(2) The internal fan 41 is large in diameter so that each blade 41b is positioned on the outer peripheral side or extends from the bearings 36a, 36b of the compression mechanism section 7, and therefore the crankcase 17 is compared with a small fan. A strong airflow can be generated in the inside, and the cooling performance of the compression mechanism part 7 can be improved.

(3) Since the compression mechanism portion 7 is provided with the vent hole 42b penetrating in the axial direction, the cooling air can flow also inside the compression mechanism portion 7 and the cooling performance of the compression mechanism portion 7 can be improved. it can. Further, since the vent hole 42b penetrates the inside of the bearings 36a and 36b, the bearings 36a and 36b that easily generate heat can be suitably cooled.

(4) Since the vent hole 43a is provided in the first connecting rod 33a and the vent hole 43b is provided in the second connecting rod 33b, the circulation of the cooling air in the crankcase 17 can be made smoother, and the compression mechanism section 7 cooling performance can be improved.

(5) The intake passage 45 of the first cylinder 15a is provided in the portion where the air flow sent out from the internal fan 41 flows, and the negative pressure generating portion of the internal fan 41 and the intake port 35 of the crankcase cover 17a are closely opposed to each other. The internal fan 41 can increase the amount of air supplied to the first compression chamber 48a by the air flow generated by itself, and can promote the intake into the crankcase 17 by the suction negative pressure of the internal fan 41. Can be improved.

Embodiment 2
FIG. 6 is a horizontal sectional view of the air compressor according to Embodiment 2 of the present invention. This air compressor differs from that of the first embodiment shown in FIG. 2 and the like in that an intake passage inlet 44 is disposed on the outer periphery of the internal fan 41 (on the radial extension or in the vicinity thereof). Thereby, a part of the airflow generated by the internal fan 41 can be sent directly into the intake passage 45 like the airflow CA4. The air flow CA4 is further sucked into the first cylinder 15a through a passage (not shown). Therefore, since the air pressurized by the internal fan 41 can be sent into the first cylinder 15a as compressed air, the discharge amount can be improved. Other points of the present embodiment are the same as those of the first embodiment, and the same effects can be achieved.

Embodiment 3
FIG. 7 is a vertical partial cross-sectional view including the motor rotating shaft 5 of the air compressor according to Embodiment 3 of the present invention. FIG. 8 is a perspective view of the internal fan 41 of FIG. In this air compressor, the internal fan 41 is an axial fan, and the spacer 200 is interposed between the internal fan 41 and the second connecting rod 33b, as compared with the first embodiment shown in FIG. It differs from the point attached to the motor rotating shaft 5 and the point that the flywheel 40 is lost, and is the same in other points. The internal fan 41 includes a hub 203 formed of a cylindrical portion 204 and a flat plate portion 205, and a plurality of axial flow type blades 206 extending from the hub 203 to the outer peripheral side. Is formed. The airflow CA1 can be easily generated by the vent 202. Even when the internal fan 41 is an axial fan, an air flow similar to that of the first embodiment is generated, and a similar cooling effect can be obtained. Furthermore, in the internal fan 41 (axial fan), the number of blades 206 is set to be larger in some areas in the circumferential direction than in other areas so that the center of gravity is eccentric with respect to the rotation axis. A region where the number of blades 206 is large functions as a counterweight portion. In this way, the counterweight portion can also be formed by the blades 206 of the internal fan 41 (the same applies when the internal fan 41 is a centrifugal fan as in the first embodiment). If the internal fan 41 is made of a material having a large specific gravity such as a metal, the function as the counterweight portion is enhanced. Other points of the present embodiment are the same as those of the first embodiment, and the same effects can be achieved.

  The present invention has been described above by taking the embodiment as an example. However, it is understood by those skilled in the art that various modifications can be made to each component and each processing process of the embodiment within the scope of the claims. By the way. Hereinafter, modifications will be described.

  The drive source is not limited to the brushless motor illustrated in the embodiment, and may be an arbitrary rotational drive source such as a motor with a brush or an engine. The compression mechanism unit 7 may be another known compression mechanism such as a Scotch yoke mechanism. Further, there is no vent hole 42a, 42b, 43a, 43b, and a configuration in which air is sucked from an arbitrary location or a configuration in which any one or more locations are adopted is possible. Cooling air can be circulated in the case 17 and the cooling performance of the compression mechanism unit 7 can be improved as compared with the case where the internal fan 41 is not provided.

DESCRIPTION OF SYMBOLS 1 Air compressor, 2a, 2b Air tank, 3 Compression part, 4 Motor (drive source), 5 Motor rotating shaft, 6 Screw material, 7 Compression mechanism part, 8a, 8b Cooling fan, 9a, 9b Pressure reducing valve, 10a, 10b Pressure gauge, 11a, 11b Coupler, 12 Pressure control valve, 13 Drain discharge device, 14 Operation part, 15a 1st cylinder, 15b 2nd cylinder, 16a 1st cylinder head, 16b 2nd cylinder head, 17 Crankcase, 17a Crankcase cover, 18 bush, 19 piping, 21 control circuit, 22 filter element, 23 stator coil, 24 rotor, 25 hall element substrate, 26 cover, 27 filter cover, 28 operation panel, 29a, 29b wind window, 31a, 31b gripping Part, 32 leg part, 33a first connecting rod, 33b second connecting part 34a, 1st piston, 34b 2nd piston, 35 Air intake port, 36a, 36b Bearing, 37a, 37b Eccentric collar, 38a, 38b Spacer, 39 key, 40 Flywheel, 41 Internal fan, 41a Flat plate part, 41b Blade (Centrifugal), 42a, 42b vent, 43a, 43b vent, 44 intake passage inlet, 45 intake passage, 46 counterweight portion, 47 guide air passage, 48a first compression chamber, 49 flat plate portion, 200 spacer, 202 Vent, 203 Hub, 204 Cylindrical part, 205 Flat part, 206 Blades (Axial flow type), CA1, CA2, CA3, CA4 Air flow, IN1, IN2 Intake flow, R Rotation direction

Claims (8)

An air tank for storing compressed air;
A compression unit that compresses air sucked from outside and supplies the compressed air to the air tank;
A drive source for driving the compression unit,
The compression part includes a crankcase, and a compression mechanism part disposed in the crankcase,
The air compressor which provided the vent hole penetrated to an axial direction in the said compression mechanism part.   The air compressor according to claim 1, further comprising an inertia body that rotates together with the compression mechanism portion in the crankcase, wherein the inertia body has a flat plate portion having a diameter larger than an eccentric collar of the compression mechanism portion.   The air compressor according to claim 2, wherein the inertial body has a vent hole adjacent to the compression mechanism section and communicating with the vent hole.   The air compressor according to any one of claims 1 to 3, wherein the vent includes a vent provided on an inner peripheral side from a bearing of the compression mechanism portion.   The air compressor according to any one of claims 1 to 4, wherein the vent includes a vent provided on an outer peripheral side from a bearing of the compression mechanism section.   The air compressor according to any one of claims 1 to 5, wherein the vent includes a vent provided in a rod connected to a piston of the compression mechanism section.   The compression mechanism section is a crank mechanism configured by an eccentric collar attached to a rotation shaft of the drive source and a connecting rod provided on an outer periphery of the eccentric collar via a bearing, and the vent hole is arranged as the eccentric shaft. The air compressor according to any one of claims 1 to 6, wherein the air compressor is formed in a collar.   The air compressor according to claim 7, wherein the vent is also formed in the connecting rod.