JP2012251501A - Vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute a vacuum pump for inhibiting the intake of outer air into a driving chamber when a piston is actuated in an air exhausting direction.SOLUTION: An exhaust path E, to which air is fed from a negative pressure chamber A when the piston 2 is actuated in the air exhausting direction, and a ventilation path F, communicating with the ventilation port 7A of the driving chamber B join in a silencer 18 serving as a joining space, and the silencer 18 communicates with a pump outside space via an opening port 15A at an outside position of an air filter 17 of a filter space G. When the piston 2 is actuated in the air exhausting direction, a communication hole 2T is opened by the displacement of a piston ring 30, air in the negative pressure chamber A is fed to the driving chamber B from the communication hole 2T, and at the same time, air in the negative pressure chamber A is fed to the exhaust path E, and thus, air flows from the silencer 18 to the driving chamber B, to inhibit the intake of outer air into the driving chamber B.

Description

  The present invention relates to a vacuum pump that creates a negative pressure by the operation of a piston, and more particularly to a technique for controlling the flow of fluid by the operation of a piston ring provided in the piston.

  As a vacuum pump described above, Patent Document 1 includes a piston that is reciprocally movable inside a cylinder, a drive unit that converts a driving force of a motor into a reciprocating operation by a crank mechanism and transmits the piston to the piston, and a cylinder head that has intake air. A configuration with a valve body having a valve and an exhaust valve is shown. In Patent Document 1, a piston ring is provided on the outer periphery of the piston.

  Although different from the above-described vacuum pump, Patent Document 2 shows a compressor that compresses air, and this compressor includes a piston that can be reciprocated inside a cylinder like the vacuum pump. Drive means for actuating is provided.

  In Patent Document 2, a piston ring having a narrower width than the annular groove is provided in the annular groove on the outer periphery of the piston so as to be movable in the width direction. The annular groove has an inlet communicating with the cylinder head, a crank The piston ring is configured as an on-off valve by forming an opening communicating with the case side. With this configuration, when the piston is operated in the compression direction, the piston ring closes the opening to prevent the air flow from the cylinder head side to the crankcase side, thereby realizing the compression, and when the piston is operated in the intake direction, the piston ring Opening the opening allows air to flow from the crankcase side to the cylinder head side.

JP 2011-7118 A Japanese Patent Laid-Open No. 09-14141

  Assuming a vacuum pump with a negative pressure chamber formed on the cylinder head side and a drive chamber that houses the crank mechanism, etc. on the opposite side of the negative pressure chamber, it is possible to suppress the intrusion of dust and the like into the drive chamber. The drive chamber is preferably a closed space from the viewpoint of suppressing operation noise during operation.

  However, when the drive chamber is configured as a closed space, the internal air is compressed and depressurized when the piston is operated, which causes a fluctuation in the drive torque of the electric motor or the like that operates the piston and is stable. Driving was impaired.

  Therefore, it is considered to form a small-diameter opening in order to allow air to enter and exit. However, when the opening is formed in this way, when the piston is operated in the exhaust direction, dust and moisture are removed from the opening as the driving chamber is decompressed. The phenomenon of inhaling into the drive chamber is inevitable and there is room for improvement.

  For such inconvenience, it is conceivable to operate the piston ring so that the air in the negative pressure chamber is sent out to the drive chamber when the piston is operated in the exhaust direction. Since the structure prevents air flow when operating in the direction (compression direction), it cannot be simply combined.

  An object of the present invention is to rationally configure a vacuum pump that suppresses the intake of outside air into the drive chamber when the piston is operated in the exhaust direction.

  A feature of the present invention is that a piston is provided so as to be reciprocally movable inside the cylinder while partitioning the inside of the cylinder into a negative pressure chamber on the cylinder head side and a driving chamber on the opposite side of the negative pressure chamber. A piston ring having a width narrower than the width of the annular groove fitted in an annular groove formed on the entire outer periphery of the piston, and supply and discharge of fluid to and from the negative pressure chamber during the reciprocating operation of the piston. A valve unit provided in the cylinder head for control, and a communication hole is formed between the bottom of the annular groove and the drive chamber, and a vent hole is formed between the drive chamber and the external space. There is in point.

According to this configuration, when the piston operates in the intake direction, the piston ring is displaced to a position that closes the communication hole, so that a negative pressure is created in the negative pressure chamber and the fluid in the drive chamber is increased as the pressure in the drive chamber increases. Through the vent. On the other hand, when the piston is operated in the exhaust direction, the piston ring is displaced to a position that allows the fluid to flow into the communication hole, so that the fluid in the negative pressure chamber flows into the drive chamber, and the negative pressure chamber. The pressure drop is limited. As a result, when the piston reciprocates, the pressure fluctuation in the drive chamber is suppressed to suppress the suction of outside air from the vent, and the load fluctuation acting on the actuator that drives the piston is also suppressed from the suppression of the pressure fluctuation in the drive chamber. To achieve stable driving.
As a result, a vacuum pump that can be stably driven without restricting the intake of outside air to the drive chamber when the piston is operated in the exhaust direction without sucking dust and moisture into the drive chamber has been configured.

  The present invention includes an exhaust path that is closed when the piston unit is operated in the intake direction and is opened when the piston is operated in the exhaust direction, an exhaust path communicating with the exhaust valve, and the vent A vent path that communicates with the exhaust path, and an exhaust port that joins the exhaust path and the vent path in a merge space and communicates the merge space with a space outside the pump, and is provided between the merge space and the open port. A fluid filter may be provided.

  According to this, when the piston operates in the exhaust direction, the fluid in the negative pressure chamber is sent out from the exhaust valve to the exhaust path, passes through the fluid filter from the merge space, and is sent out of the pump through the opening. In addition, when the piston operates in the exhaust direction, the fluid in the negative pressure chamber flows into the drive chamber due to the displacement of the piston ring, so that the pressure drop in the drive chamber is suppressed, but if the negative pressure is not completely eliminated The fluid is sucked into the driving chamber from the vent. Since the vent hole communicates with the merge space through the vent path, when the fluid is sucked from the vent hole, the fluid sent from the exhaust path to the merge space is sucked and the outside air is rarely sucked. Further, even when the outside air is sucked into the driving chamber, dust and moisture contained in the air sucked from the opening are removed by the fluid filter, and the inconvenience that the dust and moisture are sucked into the driving chamber is suppressed.

  The present invention checks that the fluid in the drive chamber is sent out from the vent when the piston operates in the intake direction, and suppresses the flow of fluid from the vent to the drive chamber when the piston operates in the exhaust direction. A valve may be provided.

  According to this, when the piston operates in the intake direction and the pressure in the driving chamber rises, the check valve sends the fluid in the driving chamber to the ventilation path. On the contrary, even when the piston operates in the exhaust direction and the driving chamber becomes negative pressure, the check valve suppresses the flow of fluid into the driving chamber, so that the suction of the fluid to the driving chamber is suppressed. Thereby, it becomes possible to prevent suction of dust and moisture to the driving chamber.

It is sectional drawing of a vacuum pump. It is sectional drawing which shows the positional relationship of a piston ring and a communicating hole when a piston moves to an exhaust direction and an intake direction. It is sectional drawing of the vacuum pump of another embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Basic configuration]
As shown in FIG. 1, a piston 2 is provided inside the cylinder 1 so as to be reciprocally movable. A negative pressure chamber A is provided on the cylinder head side with respect to the piston 2, and the negative pressure chamber A is defined with respect to the piston 2. A reciprocating type vacuum pump is configured to include a driving chamber B that houses a crank mechanism C that transmits driving force to the piston 2 on the opposite side.

  This vacuum pump is used as a negative pressure source of an automobile brake booster (not shown). By operating the piston 2 in the intake direction (right side in FIG. 1), negative pressure is applied to the negative pressure chamber A. And the piston 2 is actuated in the exhaust direction (left side in FIG. 1) to discharge air as a fluid from the negative pressure chamber A to the outside. Note that this vacuum pump is not limited to that used in automobiles, but can be used in other devices that require negative pressure, and gas other than air may be used as a fluid.

[Specific configuration]
In this vacuum pump, a negative pressure chamber A is formed between the valve unit V and the piston 2 by arranging the valve unit V at one end (cylinder head side) of the cylinder 1. A pump housing 3 is disposed on the other end side of the cylinder 1, and a driving chamber B is formed by the internal space of the pump housing 3.

  An electric motor 4 is provided in the pump housing 3, a base end of a connecting rod 6 is connected to a crank arm 5 that rotates integrally with an output shaft 4 </ b> A of the electric motor 4, and a piston 2 is connected to the tip of the connecting rod 6. doing. Thus, the crank mechanism C includes the crank arm 5 and the connecting rod 6. With this configuration, the crank mechanism C converts the rotational driving force of the output shaft 4A of the electric motor 4 into a reciprocating operating force, which is transmitted to the piston 2, and the piston 2 is reciprocated.

  The drive chamber B has a structure in which a space opened laterally in the pump housing 3 is closed by a plate-like closing member 7, and a ventilation hole 7 </ b> A is formed in the closing member 7. A path block 15 having an internal space communicating with the vent 7 </ b> A is disposed outside the closing member 7, and the path block 15 and the closing member 7 are connected and fixed to the pump housing 3 by fixing bolts 8. In addition, a cylindrical portion 16 communicating with the internal space projects from the path block 15 in the direction of the valve unit V.

  The valve unit V includes an intake valve 22 at a portion communicating with the intake space 21 </ b> A of the valve body 21, and an exhaust valve 23 at a portion communicating with the exhaust space 21 </ b> B of the valve body 21. The valve unit V includes a cover plate 24 that isolates the intake space 21A and the exhaust space 21B from the external space, and a tube 25 that applies a negative pressure to an external brake booster is connected to the cover plate 24. Yes. The intake valve 22 is made of a material that can be flexibly deformed, such as rubber or resin. When the air flow is blocked, the outer lip portion is in close contact with the valve body 21 to allow the air flow. The lip portion rises from the valve body 21 to form a space that allows the flow of air. Further, the exhaust valve 23 is configured to be biased in the closing direction by the spring 23S. When the air flow is blocked, the outer periphery is in close contact with the valve body 21 by the biasing force of the spring 23S, and the air When allowing the flow, the outer peripheral portion rises from the valve body 21 against the urging force of the spring 23 </ b> S to form a space that allows the flow of air. As the intake valve 22 and the exhaust valve 23, a ball or poppet urged in the closing direction by a spring, or a plate-like member that is operated by a hinge may be used.

  The valve body 21 is provided with a cylindrical projecting portion 26 that communicates with the exhaust space 21 </ b> B so as to project toward the pump housing 3. A cylindrical connecting tube 9 is provided to connect the protruding portion 26 and the cylindrical portion 16 in a communicating state. The connecting tube 9 has one end fitted on the protruding portion 26 and the other end connected to the cylindrical portion 16. It is provided in a form that fits outside.

  The valve unit V is connected to the pump housing 3 in such a manner that the tip of the connecting bolt 10 inserted through the through hole between the valve body 21 and the cover plate 24 is screwed into the female screw portion of the pump housing 3. This connection is performed by a plurality of connection bolts 10. When connecting, the cylinder 1 is sandwiched between the valve unit V and the pump housing 3, and the connection pipe 9 is sandwiched between the valve unit V and the path block 15. These are integrated.

  A ventilation path F is formed from the ventilation hole 7 </ b> A through the internal space of the path block 15 and across the opening 15 </ b> A formed in the outer surface of the path block 15. An exhaust path E is formed from the exhaust space 21 </ b> B of the valve body 21 through the connection pipe 9 to the internal space of the path block 15. The ventilation path F communicates with the opening 15A through the filter space G, and the filter space G is provided with an air filter 17 (an example of a fluid filter).

  In particular, a hollow silencer 18 having a donut shape surrounding the filter space G is formed inside the path block 15. The space constituting the silencer 18 and the filter space G are formed between the outer wall of the closing member 7 and the inner wall of the path block 15, and the silencer 18 functions as a merging space for joining the exhaust path E and the ventilation path F. To do. In the filter space G, an air filter 17 is provided in close contact with the outer wall of the closing member 7 and the inner wall of the path block 15. The air filter 17 is made of wool felt having a dust removal performance, paper material, urethane foam or the like.

〔piston ring〕
As shown in FIG. 2, an annular groove 2G is formed on the entire circumference of the outer surface of the piston 2, and has a width narrower than the groove width of the annular groove 2G and in the width direction (the operation direction of the piston 2) inside the annular groove 2G. A piston ring 30 is fitted so as to be freely displaceable. Further, a piston guide bush 31 is fitted on the outer periphery of the piston 2, the piston ring 30 and the piston guide bush 31 are in contact with the inner peripheral surface of the cylinder 1, and the outer periphery at both ends of the piston 2 is the inner peripheral surface of the cylinder 1. It is comprised so that it may not touch. The annular groove 2G includes a first side wall 2Ga on the negative pressure chamber side, a second side wall 2Gb on the drive chamber side, and a bottom wall 2Gc that is a bottom portion of the annular groove 2G at a position sandwiched therebetween. The piston ring 30 has a triple structure in which three types of an inner ring 30A, an intermediate ring 30B, and an outer ring 30C are overlapped.

  The inner ring 30A is made of stainless steel and has a slit formed in the ring portion. The intermediate ring 30B and the outer ring 30C are made of tetrafluoroethylene resin, and a slit is formed in the ring portion. The slits of the inner ring 30A, the intermediate ring 30B and the outer ring 30C are the same as those generally formed to facilitate the enlargement of the inner diameter when fitted into the annular groove 2G. Also, the slit of the intermediate ring 30B is disposed at a position 180 degrees different from the slit of the inner ring 30A, and the slit of the outer ring 30C is disposed at a position 180 degrees different from the position of the slit of the intermediate ring 30B. The sealing performance is improved.

  The piston ring 30 exerts an urging force in a direction in which the inner ring 30A expands the radius. The urging force brings the outer periphery of the outer ring 30C into contact with the inner peripheral surface of the cylinder 1 and the inner ring 30A. A gap is formed between the peripheral surface and the bottom wall 2Gc of the annular groove 2G.

  A plurality of communication holes 2T for communicating the bottom wall 2Gc of the annular groove 2G and the inside of the piston 2 are formed, and the communication holes 2T communicate with the drive chamber B. When the piston 2 operates in the intake direction, as shown in FIG. 2B, the piston ring 30 is displaced in the direction of the first side wall 2Ga and comes into contact with the first side wall 2Ga. To prevent air flow from communicating to the communication hole 2T. On the contrary, when the piston 2 operates in the exhaust direction, as shown in FIG. 2A, the piston ring 30 is displaced in the direction of the second side wall 2Gb and comes into contact with the second side wall 2Gb. In order to form a gap between the piston ring 30 and the first side wall 2Ga, air flow from the negative pressure chamber A to the communication hole 2T is allowed.

[Operating form]
Due to such a configuration, when the piston 2 operates in the intake direction, the piston ring 30 is displaced to a position where it abuts (closely contacts) the first side wall 2Ga, and therefore air from the negative pressure chamber A to the drive chamber B Is blocked. By the operation of the piston 2, the intake valve 22 is opened and the air from the tube 25 is sucked into the negative pressure chamber A to apply the negative pressure, so that the air in the driving chamber B enters the ventilation path F from the vent 7A. It is sent and discharged out of the pump through the opening 15A.

  Further, when the piston 2 operates in the exhaust direction, the exhaust valve 23 is opened and air from the negative pressure chamber A is sent to the exhaust path E. At the same time, since the piston ring 30 is displaced to a position where it abuts on the second side wall 2Gb, the air in the negative pressure chamber A is sent to the communication hole 2T from the gap between the piston ring 30 and the first side wall 2Ga. In this operation, the driving chamber B reaches a negative pressure state. However, since air is sent from the communication hole 2T to the driving chamber B, the degree of negative pressure is low, and the amount of air sucked into the driving chamber B from the vent 7A is reduced. The In particular, since the ventilation path F that sends air to the ventilation hole 7A merges with the exhaust path E in the space of the silencer 18, it becomes possible to send air from the exhaust path E to the ventilation path F due to negative pressure. Even when air is sucked into the drive chamber B, the air in the exhaust path E and the air sucked through the opening 15A are mixed, and the amount of outside air sucked can be reduced. When air is sucked from the opening 15A, air filtered by the air filter 17 is sucked, so that dust and moisture (moisture) are removed by the air filter 17 and enter the driving chamber B. There is nothing.

  Further, when the piston 2 operates in the exhaust direction, the air in the negative pressure chamber A flows directly to the drive chamber B through the communication hole 2T. And the drive torque of the electric motor 4 is stabilized. In addition, driving the electric motor 4 with a constant load improves the durability of the electric motor 4 without changing the power supplied to the electric motor 4. During the reciprocating operation of the piston 2, air in the exhaust path E and the ventilation path F flows intermittently and generates noise with pressure fluctuation, but the silencer 18 suppresses noise.

[Another embodiment]
The present invention may be configured as follows in addition to the above-described embodiment (in this another embodiment, the same functions and the same numbers as those in the above-described embodiment are given to those having the same functions as those in the above-described embodiment. )

(A) As shown in FIG. 3, the air vent 7A is provided with a check valve 35 that opens when air is sent out from the driving chamber B and closes when air is sucked into the driving chamber B. A holding member 36 that holds the valve 35 is attached. The check valve 35 is made of a material that can be flexibly deformed, such as rubber or resin, like the intake valve 22 of the above-described embodiment. When the air flow is blocked, the outer lip portion is blocked. In close contact with the member 7, when the air flow is allowed, the outer peripheral lip part rises from the closing member 7 to form a space allowing the air flow. The check valve 35 may be configured by using a ball or poppet urged in a closing direction by a spring, or a plate-like member that is operated by a hinge.

  With this configuration, when the piston 2 operates in the intake direction, air can be discharged from the drive chamber B, while the piston 2 operates in the exhaust direction and the drive chamber B reaches a negative pressure state. Even in such a case, suction of air from the outside to the drive chamber B can be prevented, dust and moisture can be prevented from being sucked into the drive chamber B, and the driving torque of the electric motor 4 can be stabilized.

(B) It replaces with the check valve 35 of another embodiment (a), and when the piston 2 act | operates to an exhaust direction, the valve body of a structure which restrict | limits the inflow of the air with respect to the drive chamber B is provided. As an example, a configuration in which an opening functioning as an orifice is formed in a part of the check valve 35 of another embodiment (a) is conceivable. By adopting such a configuration, when the piston 2 operates in the intake direction, the air is discharged from the drive chamber B, while the piston 2 operates in the exhaust direction and the drive chamber B is in a negative pressure state. When the pressure reaches the value, the orifice of the check valve 35 operates to limit the amount of air sucked into the drive chamber B.

  As this valve body, it is possible to use a member such as a ball or a poppet urged in the closing direction by a spring, or a plate-like member operated by a hinge. A configuration that does not reach a completely closed state is adopted. Thus, when the piston 2 operates in the intake direction, the air can be discharged from the drive chamber B, while when the piston 2 operates in the exhaust direction and the drive chamber B reaches a negative pressure state, the drive is performed. By reducing the amount of air sucked into the chamber B from the outside, the suction of dust and moisture into the driving chamber B is suppressed, and the driving torque of the electric motor 4 is also stabilized.

(C) In the vacuum pump of the present invention, the configuration and arrangement of the valve unit V can be arbitrarily set, and the configuration and arrangement of each member are arbitrary, such as forming the exhaust path E and the ventilation path F integrally with the pump housing 3. Can be set.

  The present invention can be used for all vacuum pumps having a configuration in which a piston operates inside a cylinder.

1 cylinder 2 piston 2G annular groove 2Gc bottom (bottom wall)
2T communication hole 7T Ventilation hole 15A Opening port 17 Fluid filter (air filter)
18 Junction space (silencer)
23 Exhaust valve 30 Piston ring 35 Check valve A Negative pressure chamber B Drive chamber E Exhaust path F Ventilation path V Valve unit

Claims (3)

A cylinder,
A piston provided in a reciprocating manner inside the cylinder while partitioning the inside of the cylinder into a negative pressure chamber on the cylinder head side and a drive chamber on the opposite side of the negative pressure chamber;
A piston ring having a width narrower than the width of the annular groove fitted in the annular groove formed on the entire outer surface of the piston;
A valve unit provided in the cylinder head to control supply and discharge of fluid to and from the negative pressure chamber during reciprocating operation of the piston,
A vacuum pump in which a communication hole is formed between the bottom of the annular groove and the drive chamber, and a vent hole is formed between the drive chamber and the external space. The valve unit includes an exhaust valve that closes when the piston operates in the intake direction and opens when the piston operates in the exhaust direction;
An exhaust path that communicates with the exhaust valve and a vent path that communicates with the vent, and that joins the exhaust path and the vent path in a merging space and opens the merging space to communicate with a space outside the pump. The vacuum pump according to claim 1, further comprising a port, and a fluid filter provided between the merging space and the open port.   A check valve that feeds fluid in the drive chamber from the vent when the piston operates in the intake direction and suppresses the flow of fluid from the vent to the drive chamber when the piston operates in the exhaust direction; The vacuum pump according to claim 1 or 2.

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