Pump apparatus

In a pump apparatus having a reduction chamber for reducing pulsation of a hydraulic fluid pressurized in a pump section on the way of a discharge channel having an opening in the outer surface of the housing of the pump section, a remaining fluid inflow prevention pipe having one end fitted into and fixed to the discharge channel between the outer surface and the reduction chamber and the other end positioned in the reduction chamber is provided, and a seal lip for fluid-tightly sealing the space between the inner wall of the discharge channel and the one end is provided on the outer circumference of the one end. The seal lip is formed in a shape tapered toward the discharge side. Further, the outside diameter of the other end of the remaining fluid inflow prevention pipe is made larger than the inside diameter of the discharge channel.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2004-164502 filed in Japan on Jun. 2, 2004, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pump apparatus comprising, on the way of a discharge channel having an opening in the outer surface of the housing of a pump section, a reduction chamber for reducing pulsation of a hydraulic fluid pressurized by the pump section.

2. Description of Related Art

Recent automobiles are equipped with many assistant apparatuses such as a power steering apparatus and an automatic transmission apparatus, which are activated by oil pressure to assist driving operations, and a pump apparatus is installed to generate hydraulic oil pressure of such an assistant apparatus. Since the pump apparatus is installed in vehicles, it is required to be small in size and generate high oil pressure, and therefore a rotary positive displacement pump, such as a vane pump and a gear pump, is often used as a pump section for pressurizing the hydraulic oil.

In such a pump apparatus, the hydraulic oil is intermittently discharged from the pump section, and pulsation occurs in the discharged hydraulic oil. Hence, a reduction chamber for reducing the pulsation needs to be provided on the discharge side. When the reduction chamber and the pump apparatus are provided separately, the installation performance in a vehicle is poor, and therefore it is required to integrate the reduction chamber and the pump apparatus to achieve a compact structure.

As a pump apparatus capable of satisfying such a requirement for the compact structure, there is a pump apparatus that has a reduction chamber for reducing pulsation of hydraulic oil pressurized in the pump section on the way of a discharge channel having an opening in the outer surface of the housing of the pump section and is constructed to discharge the hydraulic oil whose pulsation has been reduced in the reduction chamber from the opening in the outer surface of the housing (see, for example, Japanese Patent Application Laid-Open No. 11-166483 (1999)).

In general, a pump apparatus installed in a vehicle is shipped after performing a performance inspection after assembly and removing the hydraulic oil used for the performance inspection. When shipping the pump apparatus, a dustproof cap is attached to the opening in the outer surface of the housing so as to prevent infiltration of foreign matters such as dust during the transport to a shipping destination.

However, in the pump apparatus having the reduction chamber on the way of the discharge channel as disclosed in the Japanese Patent Application Laid-Open No. 11-166483 (1999), since the configuration of the path from the pump section to the opening in the outer surface of the housing is complicated, it is difficult to perfectly remove the hydraulic oil used for the performance inspection, and consequently the pump apparatus is sometimes shipped with the hydraulic oil remaining in the reduction chamber. In this case, there was the problem that the hydraulic oil remaining in the reduction chamber flowed into the discharge channel on the opening side during the transport to the shipping destination, and the hydraulic oil flowed into the discharge channel on the opening side leaked out of the opening when a worker at the shipping destination detached the dustproof cap to install the pump apparatus in a vehicle. When such leakage of hydraulic oil occurs, various problems may be caused, for example, the periphery is soiled with the leaked hydraulic oil, and the leaked hydraulic oil drops on the floor and makes the floor slippery for the worker.

Such problems are not associated only with pump apparatuses using oil as a hydraulic fluid, and may also be caused by pump apparatuses using a liquid other than oil as a hydraulic fluid.

BRIEF SUMMARY OF THE INVENTION

The present invention has been made with the aim of solving the above problems, and it is an object of the present invention to provide a pump apparatus comprising a member for preventing the inflow of a hydraulic fluid remaining in a reduction chamber into a discharge channel on the opening side, and thereby avoiding leakage of the hydraulic fluid during installation at a shipping destination and preventing various problems associated with the leakage.

A pump apparatus according to a first aspect of the present invention is a pump apparatus comprising, on the way of a discharge channel having an opening in the outer surface of a housing of a pump section, a reduction chamber for reducing pulsation of a hydraulic fluid pressurized in the pump section, and characterized by comprising a remaining fluid inflow prevention pipe having one end fitted into and fixed to the discharge channel between the outer surface and the reduction chamber, and other end positioned in the reduction chamber, wherein a seal lip for fluid-tightly sealing the space between the inner wall of the discharge channel and the one end is provided on the outer circumference of the one end.

A pump apparatus according to a second aspect of the present invention is based on the first aspect, and characterized in that the seal lip is formed in a shape tapered toward the discharge side.

A pump apparatus according to a third aspect of the present invention is a pump apparatus comprising, on the way of a discharge channel having an opening in the outer surface of a housing of a pump section, a reduction chamber for reducing pulsation of a hydraulic fluid pressurized in the pump section, and characterized by comprising: a remaining fluid inflow prevention pipe having one end fitted into and fixed to the discharge channel between the outer surface and the reduction chamber, and other end positioned in the reduction chamber; and a seal part for fluid-tightly sealing the space between the inner wall of the discharge channel and the one end.

A pump apparatus according to a fourth aspect of the present invention is based on any one of the first through third aspects, and characterized in that the outside diameter of the other end of the remaining fluid inflow prevention pipe is made larger than the inside diameter of the discharge channel between the outer surface and the reduction chamber.

According to the first aspect, the pump apparatus comprises the remaining fluid inflow prevention pipe having one end fitted into and fixed to the discharge channel between the outer surface of the housing and the reduction chamber, and the other end positioned in the reduction chamber, and a seal lip for fluid-tightly sealing the space between the inner wall of the discharge channel and the one end of the remaining fluid inflow prevention pipe is provided on the outer circumference of the one end of the remaining fluid inflow prevention pipe. Therefore, the inflow of the hydraulic fluid remaining in the reduction chamber into the discharge channel is prevented by the remaining fluid inflow prevention pipe and the seal lip. According to the third aspect, the pump apparatus comprises the remaining fluid inflow prevention pipe having one end fitted into and fixed to the discharge channel between the outer surface of the housing and the reduction chamber, and the other end positioned in the reduction chamber; and a seal part for fluid-tightly sealing the space between the inner wall of the discharge channel and the one end of the remaining fluid inflow prevention pipe. Therefore, the inflow of the hydraulic fluid remaining in the reduction chamber into the discharge channel is prevented by the remaining fluid inflow prevention pipe and the seal part. When the pump apparatus is installed in a vehicle and activated, the hydraulic fluid discharged from the pump apparatus fills the reduction chamber, flows into the discharge channel from the other end of the remaining fluid inflow prevention pipe, and is fed out of the opening in the outer surface of the housing. Thus, the remaining fluid inflow prevention pipe and the seal lip or seal part prevent the hydraulic fluid remaining in the reduction chamber from flowing into the discharge channel without interfering with the function of the pump apparatus, thereby preventing various problems associated with the leakage of the hydraulic fluid from the opening in the outer surface of the housing.

According to the second aspect, since the seal lip is formed in a shape tapered toward the discharge side, when a force acts in the direction of pulling out the remaining fluid inflow prevention pipe, a force toward the discharge side acts on the seal lip due to the frictional resistance with the inner wall of the discharge channel, and the seal lip is pushed strongly against the inner wall of the discharge channel. Consequently, the frictional resistance between the inner wall of the discharge channel and the seal lip becomes stronger due to the push, and the remaining fluid inflow prevention pipe is prevented from being pulled out of the discharge channel.

According to the fourth aspect, since the outside diameter of the other end of the remaining fluid inflow prevention pipe is made larger than the inside diameter of the discharge channel between the outer surface of the housing and the reduction chamber, the other end of the remaining fluid inflow prevention pipe cannot be fitted into and fixed to the discharge channel, thereby preventing mistakes in connecting the remaining fluid inflow prevention pipe.

In the pump apparatus of the present invention, since the inflow of the hydraulic fluid remaining in the reduction chamber into the discharge channel is prevented by the remaining fluid inflow prevention pipe and the seal lip or seal part, the hydraulic fluid will not leak out during installation at a shipping destination, and therefore it is possible to prevent various problems associated with the leakage.

Additionally, in the pump apparatus of the present invention, since the remaining fluid inflow prevention pipe is provided, air in the reduction chamber can be exhausted from the remaining fluid inflow prevention pipe to the outside through the discharge channel. Therefore, the effect of a pulsation reduction in the reduction chamber can be stabilized, and the generation of an abnormal noise due to the air remaining in the reduction chamber can be reduced.

DETAILED DESCRIPTION OF THE INVENTION

The following description will explain in detail the present invention, based on the drawings illustrating some embodiments thereof.

FIG. 1is a vertical cross sectional view of a pump apparatus of Embodiment 1, andFIG. 2is a cross sectional view along the II-II line ofFIG. 1.

InFIG. 1, numeral1is a pump section. The pump section1is constructed as a gear pump, and comprises a driving gear10and a driven gear11that mesh with each other inside a cavity21which has an oval cross section and is formed in a gear housing20. The driving gear10and the driven gear11are sandwiched between a pair of side plates12,12fitted into the cavity21, and are supported rotatably at both ends while holding the meshed state. The gear housing20is sandwiched between a cover housing24and a disk-shaped base housing25, and the gear housing20and the cover housing24are fastened and fixed together to one surface of the base housing25with a plurality of fixing bolts26,26, . . . (only one is shown inFIG. 1).

In the gear housing20, a suction channel22for sucking a hydraulic oil is provided on one side of the meshed section of the driving gear10and driven gear11, and a discharge channel23(first discharge channel) for discharging the hydraulic oil is provided on the other side of the meshed section.

The suction channel22is connected to a reservoir tank T constructed inside a tank pipe6which is in the shape of a cylinder with a base, has an opening-side rim externally fitted and fixed to the outside edge of one surface side of the base housing25, and covers the gear housing20and cover housing24. The reservoir tank T is constructed so that it can be connected to the outside of the pump section1through a return pipe60provided on the tank pipe6.

The discharge channel23is connected to a reduction chamber3formed in the gear housing20and cover housing24from the connection surface between the two housings20and24. The reduction chamber3is connected to an outlet9formed in an outer surface27of the base housing25through a discharge channel90(second discharge channel). A cylindrical remaining fluid inflow prevention pipe5made of a synthetic resin is placed inside the reduction chamber3. One end50of the remaining fluid inflow prevention pipe5is fitted into and fixed to the discharge channel90, and the other end54thereof is positioned near the inner wall of the reduction chamber3opposite to the opening91of the discharge channel90.

A motor4for driving the pump section1is mounted on the other surface of the base housing25with a motor housing42therebetween. An output shaft40of the motor4passes through the motor housing42and protrudes toward the base housing25side. A pump shaft13is attached to the shaft center of the driving gear10of the pump section1. The pump shaft13passes through one side plate12and the base housing25, and protrudes toward the motor housing42side. The output shaft40and the pump shaft13are positioned to face each other between the base housing25and the motor housing42, and connected together with a fitting type coupling41.

The pump apparatus of the present invention constructed as described above supplies the hydraulic oil to the reservoir tank T, and drives the motor4to perform a pump operation. The rotation of the output shaft40of the motor4is transmitted to the pump shaft13through the coupling41, and then the driving gear10attached to the pump shaft13rotates together with the driven gear11that meshes with the driving gear10inside the cavity21of the gear housing20. With the rotation of the driving gear10and driven gear11, the pump section1keeps the hydraulic oil sucked from the suction channel22connected to the reservoir tank T between the teeth of the respective gears10and11and the inner surface of the cavity21of the gear housing20, and transports and pressurizes the hydraulic oil. The transported and pressurized hydraulic oil is fed from the discharge channel23to the reduction chamber3where the pulsation components are reduced, fills the reduction chamber3, and flows into the discharge channel90from the other end54of the remaining fluid inflow prevention pipe5. The hydraulic oil flowed into the discharge channel90is fed to a oil feed destination (not shown) from the outlet9, and the return oil from the oil feed destination is circulated into the reservoir tank T through the return pipe60of the tank pipe6.

After assembly, a performance inspection is performed on such a pump apparatus of the present invention by supplying the hydraulic oil from the suction channel22. After finishing the performance inspection, the hydraulic oil is removed, the reservoir tank T is mounted, a dustproof cap7(shown by the alternate long and two short dashes line inFIG. 1) is attached to the outlet9, and then the pump apparatus is shipped. The shipped pump apparatus is installed in a vehicle at a shipping destination by detaching the dustproof cap7from the outlet9and connecting the outlet9and the return pipe60to an oil feed destination of the pressurized oil, such as a power steering apparatus and an automatic transmission apparatus.

In the pump apparatus of the present invention, since the configuration of the path from the pump section1to the outlet9is complicated, it is difficult to perfectly remove the hydraulic oil used for the performance inspection, and consequently the pump apparatus is sometimes shipped with the hydraulic oil remaining in the reduction chamber3. In this case, the remaining fluid inflow prevention pipe5with the one end50fitted into and fixed to the discharge channel90prevents the hydraulic oil remaining in the reduction chamber3from flowing into the discharge channel90.

FIG. 3is an enlarged cross sectional view of the vicinity of the remaining fluid inflow prevention pipe5, andFIGS. 4A and 4Bare explanatory views showing the steps of connecting the remaining fluid inflow prevention pipe5to the discharge channel90.

A seal part51is formed on the outer circumference of the one end50of the remaining fluid inflow prevention pipe5. The seal part51is a seal lip in the form of a flange and capable of being deformed elastically. The outside diameter X of the seal part51is made slightly larger than the inside diameter Y of the discharge channel90to such a degree that the one end50of the remaining fluid inflow prevention pipe5can be fitted into the discharge channel90by deforming the seal part51elastically.

With this structure, when the one end50of the remaining fluid inflow prevention pipe5is fitted into the discharge channel90, the seal part51is elastically deformed and pushed against the inner wall93of the discharge channel90, and fluid-tightly seals the space between the inner wall93and the one end50. Therefore, the hydraulic oil8remaining in the reduction chamber3does not flow into the discharge channel90from the space between the one end50of the remaining fluid inflow prevention pipe5and the inner wall93of the discharge channel90. Moreover, since the other end54of the remaining fluid inflow prevention pipe5and the oil surface of the hydraulic oil8remaining in the reduction chamber3are sufficiently separated, the hydraulic oil8will not flow into the discharge channel90from the other end54of the remaining fluid inflow prevention pipe5. Therefore, even when the pump apparatus of the present invention is shipped in a state in which the hydraulic oil8used for the performance inspection remains in the reduction chamber3, the hydraulic oil8does not leak out of the outlet9when a worker at the shipping destination detaches the dustproof cap7to install the pump apparatus in a vehicle, thereby preventing various problems such as, for example, preventing the periphery from being soiled with the leaked hydraulic oil8, and preventing the leaked hydraulic oil8from dropping onto the floor surface and making the floor slippery for the worker.

On the other hand, the other end54of the remaining fluid inflow prevention pipe5has a larger diameter than the one end50, and the outside diameter Z of the other end54is made sufficiently larger than the inside diameter Y of the discharge channel90so that the other end54cannot be fitted into the discharge channel90. With this structure, since the other end54of the remaining fluid inflow prevention pipe5cannot be fitted into the discharge channel90(seeFIG. 5), it is possible to prevent mistakes in connecting the remaining fluid inflow prevention pipe5.

FIGS. 6A and 6Bare explanatory views showing the steps of connecting the remaining fluid inflow prevention pipe5to the discharge channel90of a pump apparatus of Embodiment 2.

InFIGS. 6A and 6B, numeral5is a cylindrical remaining fluid inflow prevention pipe made of a synthetic resin, and similarly to Embodiment 1, the one end50of the remaining fluid inflow prevention pipe5is fitted into and fixed to the discharge channel90. A seal part51is formed on the outer circumference of the one end50of the remaining fluid inflow prevention pipe5. The seal part51is a seal lip formed in a shape tapered toward the discharge side, and the outside diameter X of the larger diameter side of the seal part51is made slightly larger than the inside diameter Y of the discharge channel90. Moreover, a thin portion55having a larger inside diameter and a smaller thickness than other portion is formed in the one end50of the remaining fluid inflow prevention pipe5.

With this structure, when the one end50of the remaining fluid inflow prevention pipe5is fitted into the discharge channel90, the seal part51is elastically deformed to a smaller diameter and elastically comes into contact with the inner wall93of the discharge channel90to seal the space between the inner wall93of the discharge channel90and the one end50of the remaining fluid inflow prevention pipe5. At this time, the thin portion55is also elastically deformed and produces a repulsive force that pushes the seal part51against the inner wall93of the discharge channel90to improve the sealing performance of the seal part51. Thus, the remaining fluid inflow prevention pipe5and the seal part51certainly prevent the hydraulic oil8remaining in the reduction chamber3from flowing into the discharge channel90. Therefore, even when the pump apparatus of the present invention is shipped in a state in which the hydraulic oil8used for the performance inspection remains in the reduction chamber3, the hydraulic oil8will not leak out during installation at the shipping destination, thereby preventing various problems associated with the leakage.

Moreover, when fitting the one end50of the remaining fluid inflow prevention pipe5into the discharge channel90, a force acts on the seal part51in the opposite direction to the discharge side due to the frictional resistance between the inner wall93of the discharge channel90and the seal part51, and the force of pushing the seal part51against the inner wall93of the discharge channel90becomes weaker. Consequently, the frictional resistance between the inner wall93of the discharge channel90and the seal part51becomes weaker, and the one end50of the remaining fluid inflow prevention pipe5is easily fitted into the discharge channel90.

Further, when a force acts in the direction of pulling out the remaining fluid inflow prevention pipe5, a force toward the discharge side acts on the seal part51due to the frictional resistance between the inner wall93of the discharge channel90and the seal part51, and the larger diameter side of the seal part51is pushed strongly against the inner wall93of the discharge channel90. Consequently, the frictional resistance between the inner wall93of the discharge channel90and the seal part51becomes stronger, and prevents the remaining fluid inflow prevention pipe5from being pulled out of the discharge channel90.

The pump apparatus according to the present invention has been explained above based on the drawings illustrating Embodiment 1 or 2, but the pump apparatus of the present invention is not limited to the structures illustrated in Embodiment 1 or 2 above, and part of the structures may be added, deleted, or modified within the scope of the present invention.

For example, as shown inFIG. 7A, the one end50of the remaining fluid inflow prevention pipe5may comprise a seal part56with a larger diameter only in a predetermined distance from the end face along the axial direction. Alternatively, as shown inFIG. 7B, an O ring interposed between the one end50of the remaining fluid inflow prevention pipe5and the inner wall93of the discharge channel90may be constructed as a seal part57. Further, as shown inFIG. 7C, it may be possible to construct a seal part58by integrally forming an elastic material such as a synthetic resin or a natural rubber with the one end50of the remaining fluid inflow prevention pipe5.

Additionally, in Embodiment 1 or 2 as described above, although the material of the remaining fluid inflow prevention pipe5is a synthetic resin, it is not limited to a synthetic resin, and may be, for example a synthetic rubber or a natural rubber.

Moreover, in Embodiment 1 or 2 described above, since the whole remaining fluid inflow prevention pipe5is formed of a synthetic resin, the whole remaining fluid inflow prevention pipe5has elasticity. However, the whole remaining fluid inflow prevention pipe5does not necessarily have elasticity as long as the seal part51has elasticity.

Further, although Embodiment 1 or 2 described above explains the application of the present invention as a pump apparatus that is installed in a vehicle to obtain the hydraulic oil pressure of an assistant apparatus such as a power steering apparatus and an automatic transmission apparatus, the present invention is applicable to a pump apparatus for use in other applications, and is also applicable to a pump apparatus using a liquid other than oil as a hydraulic fluid. Besides, the pump section1is not limited to the gear pump explained in Embodiment 1 or 2 above, and may be other type of pump such as a vane pump. In addition, the driving source of the pump section1is not limited to the motor4.