翻译部分
英文原文
Hydraulic pump
Abstract:
A hydraulic pump unit is encased between a pump body and a pump cover. A bearing hole passes through the pump body and is formed in the pump body. A drive shaft and a bearing bush are inserted into the bearing hole. The drive shaft drives the hydraulic pump unit and the bearing bush supports the drive shaft. At an end portion of the bearing hole, a seal chamber is formed. The seal chamber encases a seal member. An oil groove is formed inside the bearing hole. The oil groove connects the hydraulic pump unit side with the seal chamber and carries hydraulic oil for lubrication. The oil groove is formed in such a manner that a sectional area in the seal chamber side is greater than a sectional area in the hydraulic pump unit side. The bearing bush comprises a plurality of bush pieces arranged at a predetermined interval in an axial direction of the bearing hole. SUMMARY OF THE INVENTION
The following is an explanation of one embodiment applied to a hydraulic pump of a power steering of the present invention with reference to the drawings.
In the drawings, a reference numeral 1 denotes a pump body made of metallic materials such as aluminum alloy and so on and a reference numeral 2 denotes a pump cover made of metallic materials. The pump body 1 and the pump cover 2 encase a hydraulic pump unit 3. That is, an annular concave portion 4 is formed between the pump body 1 and the pump cover 2. The hydraulic pump unit 3 is installed in the annular concave portion 4.
In this embodiment, the hydraulic pump unit 3 is a vane hydraulic pump unit. The hydraulic pump unit 3 includes a cam ring 7 encasing a rotor 6. The rotor 6 comprises a plurality of vanes 5 which are radially movable in and out. Both sides of the cam ring 7 are guided by side plates 8 and 9. A pumping chamber 10 is formed by two adjacent one of the vanes 5 between the cam ring 7 and the rotor 6. The volume of the pumping chamber 10 varies by the rotation of the rotor 6. With this variation, an inhaling zone is formed in a portion increasing in volume and a discharging zone is formed in a portion decreasing in volume. Notch passages 8a and 8b are formed in the side plates 8 and 9. The side plates 8 and 9 face the discharging zone. The notch passages 8a and 9a open radially and outwardly. The oil discharged from the pump is discharged into a discharging chamber (a high pressure chamber) 11 of the annular concave portion 4 of the outer circumference of the cam ring 7. An inhaling port not shown in the drawing is formed in the side plate 9 facing the inhaling zone and passes therethrough.
A bearing hole 12 is formed in the pump body 1 and passes through the pump body 1. A seal chamber 13 is formed in an end portion of the bearing hole 12.
An oil groove 14 communicating from the hydraulic pump unit 3 side to the seal chamber 13 is formed in the bearing hole 12. The section of the oil groove 14 is a circular arc. the sectional area of the oil groove 14 in the seal chamber 13 side is greater than the sectional area of the oil groove 14 in the hydraulic pump unit 3 side and it is easy to form the oil groove 14 in a casting mold.
The oil groove 14 in this embodiment is divided at a substantially center position of the bearing hole 12. However, because the substantially center position of the bearing hole 12 is positioned between a plurality of bush pieces later-mentioned, the substantially center position of the bearing hole 12 is substantially communicated with an interval between the bush pieces. Because the oil groove 14 is divided at the substantially center position of the bearing hole 12, this divided part becomes a so-called labyrinth and a flow resistance is applied to hydraulic oil flowing in the oil groove 14. Therefore, it is possible to decrease the energy of the hydraulic oil flowing into the seal chamber 13.
The oil groove 14 can be continuously formed without dividing at the substantially center position of the bearing hole 12. The oil groove 14 can be continuously formed in a taper shape so that the sectional area increases gradually from the hydraulic pump unit 3 side to the seal chamber 13 side.
With this structure, the oil groove 14 can lead the leakage oil from the bearing hole 12 of the hydraulic pump unit 3 to the seal chamber 13. The leakage oil from the hydraulic pump unit 3 is the hydraulic oil leaking between the rotor 6 and the side plates 8 and 9 and is a little
hydraulic oil leaking from the joint between the pump body 1 and the side plate 9.
An inhaling passage 15, a discharging passage 16 and a spool valve receiving bore 17 are formed in the pump body 1. The inhaling passage 15 connects each pumping chamber 10 of the inhaling zone with a storage tank not shown in the drawing. The discharging passage 16 connects each pumping chamber 10 of the discharging zone with the actuator of the power steering not shown in the drawing. One end of the spool valve receiving bore 17 is sealed.
The inhaling passage 15 is branched into two directions at the joint facing the side plate 9. At the end portion of the inhaling passage 15, a circular arc shape inhaling port 18 is formed. The inhaling port 18 is formed so that the inhaling port 18 faces the inhaling port, not shown in the drawing, formed in the side plate 9. The inhaling passage 15 is connected with the seal chamber 13 through a low pressure passage 19. The low pressure passage 19 is substantially parallel with the bearing hole 12.
The discharging passage 16 is bent radially and outwardly at the joint facing the side plate 9. An orifice passage 21 connected with an inhaling port 20 formed in the side plate 9 is formed in the discharging passage 16.
A reference numeral 22 denotes a bearing bush inserted into the bearing hole 12. The bearing bush 22 comprises a plurality of bush pieces 23 positioned at a predetermined interval in the axial direction of the bearing hole 12. In this embodiment, the bearing bush 22 comprises two bush pieces 23 positioned at the interval 1 in the axial direction of the bearing hole 12. The bush piece 23 is formed into a cylindrical shape by rounding a plate member. The inner surface of the bearing bush 22 is smooth. The oil groove is not formed in the bearing bush 22.
The interval 1 between the two-bush pieces 23 forming the bearing bush 22 is preferable to be substantially 1/3 of the axial length L of the bearing bush 22 in order to secure the area for supporting the bearing bush 22. In this embodiment, the interval 1 between the bush pieces 23 is substantially 1/5 of the axial length L of the bearing bush 22.
A reference numeral 25 denotes a drive shaft for driving the hydraulic pump unit 3. The drive shaft 25 is inserted into the bearing hole 12 in such a manner that the drive shaft 25 is supported by the bearing bush 22. The drive shaft 25 has serrations 26 formed near the forward end. The serrations 26 pass through the through hole 9b of the side plate 9 and are fitted in the serration hole 27 of the rotor 6. With this, the drive shaft 25 is capable of driving the rotor 6 of the hydraulic pump unit 3. The forward end portion of the drive shaft 25 is tapered and loosely fitted in the through hole 8b of the side plate 8.
A spool valve 30 controlling the quantity of the oil is slidably movable and is fitted in the spool valve receiving bore 17. The spool valve 30 divides the inside of the spool valve receiving bore 17 into a first pressure chamber 17a and a second pressure chamber 17b. The spool valve 30 is normally biased toward the first pressure chamber 17a side by a spring force of a control spring 31. The control spring 31 is encased in the second pressure chamber 17b. The spool valve 30 closes a drain passage 33 connecting the inhaling passage 15 in a normal condition.
In the pump body 1, a passage 35 is formed. The passage 35 is connected with a discharging lot not shown in the drawing in order to connect with the discharging passage 16 and to lead hydraulic oil to the power steering, that is, the actuator not shown in the drawing. The passage 35 is connected with the second pressure chamber 17b through a passage 36. The pressure in the discharging passage 16 is led into the second pressure chamber 17b.
A reference numeral 39 denotes a pressure switch mounted on the pump cover 2. The pressure switch 39 comprises a fixed contact 39a and a moving contact 39b. The pressure switch 39 is able to operate according to the pressure of the discharging chamber 11 because the end portion of the moving contact 39b faces a passage 40 connecting with the discharging chamber 11. The pressure switch 39 is thrust into and fixed in the inside of a concave portion 41. The inside of the concave portion 41 is connected with the through hole 9b of the side plate 9 through a radial passage 42 and an axial passage 43.
The pump body 1 and the pump cover 2 are connected and fixed with each other by bolts not shown in the drawing. The joint between the pump body 1 and the pump cover 2 is sealed by a seal ring 44 so as to prevent the hydraulic oil discharged into the discharging chamber 11 from leaking to the outside.
A reference numeral 45 denotes a seal ring installed between the pump cover 2 and the side plate 8. The seal ring 45 separates the discharging chamber 11 from the through hole 8b of the side plate 8. A reference numeral 46 denotes a seal member. The seal member 46 is installed in the seal chamber 13 and seals the drive shaft 25.
With this structure, the drive shaft 25 is rotationally driven through the pulley not shown in the drawing and the rotor 6 connected with the drive shaft 25 is rotationally driven. When the rotor 6 is rotationally driven, with the rotation of the rotor 6, the volume of the inhaling zone increases and the volume of the discharging zone decreases. Hydraulic oil is inhaled from the inhaling passage 15 through the inhaling port 18 into the pumping chamber 10 in the inhaling zone, passes through the pump and is discharged from the pumping chamber 10 in the discharging zone into the discharging chamber 11. The hydraulic oil discharged into the discharging chamber 11 is led to the first pressure chamber 17a through the leading passage 34. The hydraulic oil led into the first pressure chamber 17a is led into the actuator of the power steering not shown in the drawing through the orifice passage 21, the discharging passage 16 and the passage 35.
In a normal condition, the spool valve 30 is urged toward the first pressure chamber 17a side by the control spring 31 and closes the drain passage 33 by the land portion 32 of the main body of the spool valve 30. All of the discharged oil led into the first pressure chamber 17a is led into the actuator not shown in the drawing through the orifice passage 21. When the rotational speed of the pump increases, the quantity of the oil discharged from the pump increases and the quantity of the oil discharged from the pump led into the first pressure chamber 17a increases, the hydraulic oil in the first pressure chamber 17a is led into the discharging passage 16 under the limitation of flow by the orifice passage 21, the spool valve 30 moves rightward and compresses the control spring 31 to a predetermined length
according to the front and rear differential pressure of the orifice passage 21, opens the drain passage 33 and returns surplus oil from the drain passage 33 to the inhaling passage 15 and the storage tank not shown in the drawing.
As the hydraulic pump unit 3 is driven, the hydraulic oil is discharged into the discharging chamber 11 and leaks from a gap formed among the rotor 6 and the side plates 8 and 9 for lubrication. A small amount of the hydraulic oil also leaks from the joint between the pump body 1 and the side plate 9.
The leakage oil from the hydraulic pump unit 3 is collected into the bearing hole 12 of the hydraulic pump unit 3 side. That is, the leakage oil from the joint between the rotor 6 and the side plate 9 is led into the through hole 8b and is collected into the bearing hole 12 through the
engaging gaps of the serrations 26 and 27 and the through hole 9b of the side plate 9.
into the
The leakage oil from the joint between the rotor 6 and the side plate 9 is collected into the bearing hole 12 through the through hole 9b of the side plate 9. The oil collected
bearing hole 12 of the side plate 9 lubricates the bearing hole 12 and is led into the seal chamber 13 through the oil groove 14 formed in the bearing hole 12. The hydraulic oil led to the seal chamber 13 is sealed by the seal member 46 in the seal chamber 13 and is returned to the inhaling passage 15 and the storage tank not shown in the drawing through the low pressure passage 19.
At this time, the leakage oil led into the bearing hole 12 from the hydraulic pump unit 3 is directly supplied from the bearing hole 12 of the hydraulic pump unit 3 side into the inner surface of the bearing bush 22, is led into the seal chamber 13 through the oil groove 14 formed in the bearing hole 12 and is supplied from the seal chamber 13 side into the inner surface of the bearing bush 22. Because a part of the leakage oil led along the oil groove 14 is supplied from the oil groove 14 to spaces neighboring one another, the part of the leakage oil is supplied from the spaces between the bush pieces 23 into the inner surface of the bearing bush 22.
The oil supplied to the inner surface of the bush pieces 22 is led into the bearing gap in a state of a wedge. The bearing gap becomes narrower in a rotational direction with the rotation of the drive shaft 25. The oil film pressure caused by the wedge action forms a satisfactory lubricating oil film so that the drive shaft 25 is smoothly supported.
The hydraulic oil led from the oil groove 14 into the seal chamber 13 is sealed by the seal member 46 encased in the seal chamber 13.
The sectional area of the oil groove 14 in the seal chamber 13 side is formed so as to be greater than the sectional area of the oil groove 14 in the hydraulic pump unit 3 side. The oil groove 14 leads the leakage oil from the hydraulic pump unit 3 to the seal chamber 13. Therefore, when the quantity of the leakage oil from the hydraulic pump unit 3 increases, the flow speed in the oil groove 14 in the hydraulic pump unit 3 side becomes slower than the flow speed in the seal chamber 3 side and the energy of the hydraulic oil led into the seal chamber 13 decreases.
Thus, because it is possible to prevent the energy of the hydraulic oil led into the seal
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