GB2309270A

GB2309270A - Radial plunger pump

Info

Publication number: GB2309270A
Application number: GB9700715A
Authority: GB
Inventors: Yoshio Okubo; Toshiaki Hori
Original assignee: Unisia Jecs Corp
Current assignee: Hitachi Unisia Automotive Ltd
Priority date: 1996-01-17
Filing date: 1997-01-15
Publication date: 1997-07-23
Also published as: JPH09195926A; DE19701392A1; GB9700715D0; GB2309270A8; KR970059486A

Description

1 RADIAL PLUNGER PUMIP 2309270 The present invention relates to a radial

plunger pump suitable for use in an injection pump employed in an automotive fuel-injection system for feeding pressurized fuel to an injector, and specifically to a radial plunger pump which provides sufficient lubrication of all moving or rotating parts installed in a plunger pump housing, i.e., a proper amount of lubrication between the plunger pump shaft journal and a radial bearing, and ensure a good sealing action of an oil seal placed around the plunger pump shaft.

As is generally known, a conventional radial plunger pump includes a cylindrical eccentric cam (of a circle in cross-section) integrally connected to a pump shaft (a drive shaft) so that the axis of the eccentric cam deviates from the geometric center identical to the axis of the pump shaft, and a plurality of circumferentially equi-distant spaced radial plungers arranged radially with respect to the axis of the pump shaft in a manner so as to permit a reciprocating motion of each of the plungers between the top dead center (simply the top) and the bottom dead center (simply the bottom) of a cylindrical bore formed in the pump housing. When the eccentric cam rotates together with the p ' ump shaft, the plural plungers, being spring-biased against the cam surface of the eccentric cam, project radially inwardly from the top to the bottom and retract radially outwardly from the bottom to the top, in turns by way of rotation of the eccentric cam. With the prey iou s ly-noted arrangement, working fluid such as liquid fuel is sucked from a working-fluid supply passageway into the cylindrical bore with the radially-inward projecting motion of the plunger and then pressurized and discharged from the cylindrical bore into a working-fluid discharge passageway with the radial ly-ou tward retracting motion of the plunger. In recent years, this type of radial plunger pump is often used as a fuel pressurizing pump for an automobile fuel-injection system. When a radial plunger pump is applied to a fuel pressurizing pump of a fuel-injection system, there is a tendency for working fluid (fuel such as liquid gasoline having a lower viscosity) to leak through the clearance space between the plunger and the cylindrical bore into the space defined between the inner wall of the pump housing and the pump shaft and to reach around the entire face of the respective bearing. As a result, the fuel is mixed with the lubricating oil, thus lowering a scaling performance of the oil seal and also degrading a lubricating performance of lubricant (lubricating oil) delivered to the clearance space between the respective bearing and the pump shaft. To avoid this, Japanese Utility Model (Jikkai Heisei) Provisional Publication No. 6-43274 teaches the provision of a diaphragm type partition-wall member for prevention of fuel leakage from the plunger side to the pump-shaft journal side. In the prior art radial plunger pump structure disclosed in the Japanese Utility Model Provisional Publication No. 6-43274, a caulked member is integrally connected to the bottom end of each plunger by caulking. The caulked member is formed with a substantially circular lid-shaped shoe being in cam-connection with the eccentric cam and formed with an essentially annular groove. A diaphragm type thinned partition- wall member (of a substantially donut shape and of a proper flexibility) is fitted to and caulked to the annular groove of the caulked member in a fluid-tight fashion at its inner periphery, and is bolted to the pump housing in a fluid-tight fashion at its outer periphery, thereby dividing a space in the pump housing into a workingfluid chamber and a lubricating-oil chamber. In this manner, a plurality of diaphragm type partition-wall members are provided near the respective plunger bottom ends. The lubricating-oil chamber is filled with lubricant of a predetermined viscosity for adequate lubrication of the pump-shaft journal, thereby forming a good seal at the clearance space between the oil seal and the pump shaft, and permitting low-friction rotation of the pump shaft due to sufficient lubrication of the clearance space between the bearings and the pump shaft, and thus minimizing power loss from friction. However, in the radial plunger pump with the previously-discussed diaphragm type thinned partition-wall member, a plurality diaphragm type partition-wall members of the same number as the number of plungers must be installed in the pump housing, and additionally a plurality of caulked members must be attached to the respective plunger bottom ends. The number of parts of a radial plunger pump assembly is great and also such an assembling work is very troublesome. This increases production costs. Furthermore, the radial plunger pump assembly itself would be large-sized. Moreover, even when the outside diameter of the diaphragm type partition-wall member is set at a possible maximum value, such an outside diameter cannot be dimensioned to a satisfactorily great value, since a plurality of diaphragm type partition-wall members are separated from each other and provided in the limited space between the eccentric cam attached onto the pump shaft and the inner wall of the housing. As may be appreciated, the diaphragm type partitionwall member of the limited diameter has to elastically deform in synchronization with the reciprocating motion of the associated plunger during operation of the pump. Such an arrangement of the diaphragm type partition-wall member may increase a stress (the force acting across the unit area in the partition-wall member), thus decreasing the life of the partition-wall member. That is, such diaphragm type partition-wall structure is at a disadvantage in respect of durability.

Accordingly, it would be desirable to be able to provide an improved radial plunger pump which avoids the foregoing disadvantages of the prior art.

It would also be desirable to be able to provide a radial plunger pump with a simple partition-wall member of a high durability, which can enhance performance of lubrication of the pump-shaft journal by preventing working fluid (such as liquid fuel) from leaking from the plunger side towards around the pump-shaft journal with a possible minimum parts constructing a radial plunger pump assembly, and also avoid a great stress from 5 acting on the partition-wall member.

In order to accomplish the aforementioned and other objects of the invention, a radial plunger pump comprises a housing, a drive shaft rotatably supported in the housing, an eccentric cam of a circle in cross section, the eccentric cam being fixedly connected to the drive shaft so that an axis of the eccentric cam deviates from a geometric center identical to an axis of the drive shaft, a plurality of radial cylindrical bores formed in the housing, a plurality of radial plungers each accommodated in the associated one of the cylindrical bores and biased toward an outer periphery of the eccentric cam, for reciprocating motion of the plungers. each of the cylindrical bores communicating with both a suction passageway and a discharge passageway through check valves for sucking working fluid from the suction passageway on a suction stroke of the associated plunger, and for pressurizing the working fluid sucked and for feeding a pressurized working fluid to the discharge passageway on a discharge stroke of the associated plunger, an auxiliary ring fitted on the outer periphery of the eccentric cam so that the auxiliary ring is rotatable relatively with respect to the eccentric cam, and a flexible partition member provided between the auxiliary ring and the housing, for dividing a space in the housing into a working-fluid chamber and a lubricant chamber while enclosing the drive shaft, the lubricant chamber being filled with lubricant. It is preferable that the flexible partition member comprises a flexible bellows. The flexible bellows may be formed of a flexible metal bellows. Alternatively, the flexible bellows may be formed of a rubber material or a synthetic resin material. The radial plunger pump may further comprise a drain port defined in the housing for returning working fluid in the working-fluid chamber to the suction passageway. More preferably, an outside end of the flexible bellows may be firmly connected to a retaining ring fixed to the housing coaxially to the axis of the drive shaft, and an inside end of the flexible bellows may be firmly connected to a side wall of the auxiliary ring. 5 BRIEF DESCRIú11ON OF THE DRAWINGS Fig. 1 is a longitudinal cross-sectional view illustrating one embodiment of a radial plunger pump made according to the invention.

Fig. 2 is a lateral cross-sectional view taken along the line A - A of Fig. 1.

Fig. 3 is a cross-sectional view taken along the line B B of Fig. 2.

Fig. 4 is a lateral cross-sectional view taken along the line C - C of Fig. 1.

Fig. 5 is a lateral cross-sectional view taken along the line D - D of Fig. 1.

Fig. 6 is a cross-sectional view taken along the line E E of Fig. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, particularly to Fig. 1, the radial plunger pump of the invention is exemplified in case of a fuel - pressurizing pump for an automobile fuel-injection system. As shown in Fig. 1, the radial plunger pump 1 of the em bodiment functions to pressurize the working fluid such as liquid gasoline, which is supplied in the form of low-pressure working fluid from a fuel tank (or a fuel reservoir) 2 through a fuel-supply pump 3 to a suction port of the plunger pump 1, up to a predetermined pressure level, and to feed the pressurized working fluid to an injector 4. In a conventional manner, the injector 4 injects or sprays the pressurized working fluid (pressurized fuel) into the engine cylinder (not shown). Excess working fluid (excess fuel) is returned from the injector 4 to a suction passageway 5 of the pump 1. The housing assembly 6 of the radial plunger pump 1 is composed of a substantially cylindrical housing body 7 serving as a cylinder block, and front and rear covers 9 and 10. The two covers 9 and 10 are integrally connected to both end faces of the housing body 7 by way of bolts 8 in a manner so as to hermetically cover the respective end faces. A drive shaft (a pump shaft) 11 is inserted into the housing body 7 through a central bore of the front cover 9 and supported rotatably on the front and rear covers 9 and 10 through a pair of radial bearings 12 and 13. An oil seal 14 is fitted to the annular space between the outer peripheral surface of the drive shaft 11 and the inner peripheral wall surface of the front cover 9 to form a good seal therebetween. The drive shaft 11 is formed integral with an essentially circular eccentric cam 15 almost at its center, so that the axis of the eccentric cam is offset from the rotational axis of the drive shaft 11 by a predetermined value. Ile left-hand projected end (viewing Fig. 1) of the drive shaft 11 is so designed that the projected shaft end is able to be coupled with an engine camshaft (not shown) for ensuring a driven connection of the drive shaft 11 with respect to the engine camshaft.

The housing body 7 is formed with a plurality of radiallyextending, circumferentially-equidistant spaced cylindrical bores 17. A plurality of plungers 18 are slidably accommodated in the respective cylindrical bores 17 and permanently spring-loaded towards the cam surface of the eccentric cam 15, such that the co-rotation of the eccentric cam 15 with the drive shaft 11 produces the reciprocating motion of the respective plunger. The outward opening end of each of the cylindrical bores 17 is hermetically closed by means of a plug 19. As seen in Figs. 2 and 3, the housing body 7 is formed with a plurality of connection ports 20 (or connection passageways) communicating with the respective cylindrical bores 17. As seen in Figs. 2 and 3, a suction port 21 and a discharge port 22, both communicating with the associated connection port 20, are formed in the housing in such a manner as to axially extend in parallel with the axis of the drive shaft. The suction and discharge ports 21 and 22, forming a pair, are aligned with each other with respect to the axial direction. The connection port 20 is fluidly connected to the junction between the suction and discharge ports 21 and 22. A suction- side one-way check valve 23 is fluidly disposed between the associated suction port 21 and the associated connection port 20 for permitting fluid flow from the suction port 21 via the connection port 20 to the associated cylindrical bore 17 with the suction-side check valve 23 opened on the suction stroke (with the radially inward movement of the plunger 18), whereas a discharge-side one-way check valve 24 is fluidly disposed between the discharge port 22 and the connection port 20 for permitting a fluid flow from the associated cylindrical bore 17 via the connection port 20 to the discharge port 22 with the discharge-side check valve 24 opened on the discharge stroke (with the radially outward movement of the plunger 18). That is, when the plunger 18 moves radially inwardly and projects from the associated cylindrical bore during the suction stroke, the working fluid in the suction port 21 is sucked through the check valve 23 and the connection port 20 into the cylindrical bore 17. In contrast, when the plunger 18 moves radially outwardly and retracts again into the cylindrical bore during the discharge stroke, the working fluid in the cylindrical bore 17 is fed through the same connection port 20 and the check valve 24 to the discharge port 22. All of the suction ports 21 are communicated with a suction-side annular groove 25 (see Fig. 1) which is formed at one end face of the housing body 7, facing the front cover 9. On the other hand, all of the discharge ports 22 are communicated with a discharge-side annular groove 26, which is formed at another end face of the housing body 7, facing the rear cover 10. As seen in Fig. 1, these annular grooves 25 and 26 are respectively communicated with a suction passageway 5 and a discharge passageway 27 both defined in the housing assembly 6.

Referring to Figs. 1 and 6, two pressure regulators 28 and 29 are assembled on the rear cover 10. The pressure regulator 28 is fluidly connected to the suction passageway 5 for maintaining or regulating a suction pressure at a preset low- pressure level, whereas the pressure regulator 29 is fluidly connected to a return line through which the pressurized working fluid is returned from the injector 4 to the suction side for regulating an injection pressure of the working fluid from the injector 4 at a preset high-pressure level and for preventing the injection pressure from excessively developing. In Fig. 6, a return-line connection port between the return line of the injector 4 and the pressure regulator 29 is denoted by the reference sign "3T. Structures of the two pressure regulators 28 and 29 are similar to each other. Generally, the pressure regulator is so designed that a part of the working fluid in the line is drained through a drain port of the pressure regulator when a fluid pressure in the line connected to the pressure regulator becomes greater than the set pressure. The structure of each of the pressure regulators 28 and 29 is similar to a conventional pressure regulator. In the shown embodiment, the low- pressure side regulator 28 has a drain port 31 which communicates with the fuel tank 2 through a retum-line connection plug 32. The high- pressure side regulator 29 has a drain port 33 which communicates with the suction passageway 5. Hereinbelow described in detail is the structure of the suction passageway 5.

As seen in Fig. 6, the suction passageway 5 is constructed in such a manner as to extend from a suction-line connection port 34 toward the high-pressure side regulator 29, and to reorient at an annular groove 35 formed in housing to surround the outer periphery of the regulator 29, and finally to communicate with the suction-side annular groove 25 (see Fig. 1) formed at the one end face of the housing body 7.

On the other hand, an auxiliary ring 39 is mounted on the eccentric cam 15 through a metal bearing 38 while permitting a relative motion of the auxiliary ring 39 with respect to the eccentric cam 15. In other words, the auxiliary ring is installed on the outer periphery of the eccentric cam so that the auxiliary ring is rotatable relatively with respect to the eccentric cam 15. A seat cam 40 (of a high hardness and a low friction coefficient) is also mounted on and fitted to the outer peripheral surface of the auxiliary ring 39. The head (the bottom end) of the respective plunger 18 is permanently urged onto the outer periphery of the seat cam 40 by the spring bias. A pair of flexible bellows 41a and 41b are provided at both sides of the auxiliary ring 39, such that the bellows pair 41a and 41b covers around the length of the drive shaft 11 between the two bearings 12 and 13. One end of each of the bellows 41a and 41b is firmly connected to either one of the side walls of the auxiliary ring 39 in a fluid-tight fashion. The other end of the bellows 41a is firmly connected to a substantially annular bellows retaining ring 42 (see the left-hand side of Fig. 1) in a fluid-tight fashion, whereas the other end of the metal bellows 41b is firmly connected to a substantially annular bellows retaining ring 43 (see the right-hand side of Fig. 1) in a fluid-tight fashion. The left- hand retaining ring 42 is press-fitted into an essentially cylindrical hollow portion 9a formed in the front cover 9, so that the inside wall of the retaining ring 42 lies flush with the lefthand side wall of the housing body 7 and the outside wall of the retaining ring 42 lies flush with the side wall of the outer race of the radial bearing 12. The right-hand retaining ring 43 is pressfitted into an essentially cylindrical hollow portion 10a formed in the rear cover 10. The flexible bellows 41a and 41b serve as a flexible partition-wall member for dividing a space in the pump housing 7 into a working-fluid chamber 44 and a lubricant chamber 45 by enclosing all over the length of a part of the drive shaft 11 inserted into the pump housing with the flexible two bellows, and for preventing fuel leakage from the plunger side to the rotating drive-shaft journal side. An internal space between the inner wall of the respective bellows 41a and 41b and the outer periphery of the drive shaft inserted into the housing, is filled with lubricant of a predetermined viscosity for the purpose of adequate lubrication of the drive-shaft journals and the bearings. The working- fluid chamber 44 may be filled with leaked working fluid (leaked fuel) from the clearance space between the sliding surface of each plunger 18 and the cylindrical bore 17.

In Fig. 6, the reference numeral 46 denotes a drain port which is provided for returning the working fluid in the working s fluid chamber 44 to the suction passageway 5. The reference numeral 47 denotes a safety valve connected to the discharge side annular groove 26. In more detail, the safety valve 47 has a drain port connected to the working-fluid chamber 44. The safety valve is designed to return a part of the working fluid in the discharge passageway 27 via the working-fluid chamber 44 to the suction passageway 5 when the discharge pressure of the working fluid in the discharge passageway 27 exceeds a preset pressure level. Reference sign 36 denotes a discharge -pressure sensor disposed between the discharge-side annular groove 26 and the discharge-line connection port 37.

With the previous ly-noted arrangement, when the engine starts and thus the drive shaft 11 rotates in synchronization with rotation of the engine, the eccentric cam 15, integrally connected to the drive shaft 11, also rotates together with the drive shaft.

During rotation of the drive shaft, the auxiliary ring 39 revolves round the drive shaft 11, while preventing the auxiliary ring 39 from rotating on its axis by means of the two bellows 41a and 41b both fixedly connected to the auxiliary ring. With the auxiliary ring 39 revolving, the seat cam 40 installed on the outer periphery of the auxiliary ring 39, lifts in turn the plural plungers 18, whereby the plungers 18 repeatedly radially move inwardly and outwardly and thus the pumping action of the radial plunger pump can be attained successively. During operation of the pump, the working fluid (fuel), which is supplied from the fuel tank 2 through the fuel-supply pump 3 to the suction-line connection port 34, is regulated, in the middle of the suction passageway 5, at the preset low-pressure level by way of the pressure regulator 28. Thereafter, the regulated working fluid is sucked into the cylindrical bore 17 through the annular groove 35 of the high-pressure side regulator 29, the suction-side annular groove 25 formed in the housing body 7, the suction port 21, the suction-side check valve 23, and the connection port 20, in that order. Thereafter, the sucked working fluid in the cylindrical bore 17 is pressurized through the discharge stroke, and then delivered to the injector 4 from the cylindrical bore 17 through the connection port 20, the discharge-side check valve 24, the discharge port 22, the discharge-side annular groove 26, the discharge passageway 27 and the discharge-line connection port 37, in that order. After a required amount of working fluid is used by the injector 4, excessive working fluid enters the retum-line connection port 30 of the high-pressure side regulator 29, and then returned to the suction passageway 5 from the high-pressure side regulator 29 via the annular groove 35 defined on the outer periphery of the regulator 29. During is operation, the working fluid necessarily leaks into the space defined in the housing body 7 through the clearance space between the inner peripheral wall of the cylindrical bore and the sliding surface of the plunger 18. In the internal structure of the housing body 7 of the radial plunger pump made according to the invention, the internal space of the housing body 7 is divided, in a full fluid-tight fashion, into the working-fluid chamber 44 and the lubricant chamber 45 by means of the auxiliary ring 39, and the two bellows 41a and 41b. This prevents a working fluid of a low viscosity, such as a lubricant-fuel mixture produced due to leaked fuel, from coming in and around moving parts such as the bearings 12 and 13 installed on the drive shaft 11, and prevents the same from coming in and around the oil seal 14 installed on the drive shaft 11. Additionally, the life of the lubricant filling up in the lubricant chamber 45 can be increased, since there is less possibility that the lubricant of a predetermined viscosity is not mixed with or diluted with working fluid (fuel such as gasoline) of a comparatively low viscosity. The lubricant of the predetermined viscosity ensures adequate lubrication of the bearings 12 and 13, and ensures a good seating action of the oil seal 14 placed around the drive shaft 11. As a consequence, the initial performance of the respective bearings 12 and 13 and the initial sealing performance of the oil seal 14 can be insured for a long period of time, and thus the life of the radial plunger pump assembly itself can be increased.

As set forth above, according to the radial plunger pump of the invention, a pair of bellows 41a and 41b are used as a flexible partition member through which a space in the pump housing is divided into a working-fluid chamber 44 and a lubricant chamber 45. Additionally, each of the bellows 41a and 41b has an axial length enough to permit a displacement of the connected portion between the respective bellows and the auxiliary ring 39, which displacement occurs in synchronization with the revolution of the auxiliary ring 39 about the drive shaft 11. Thus, the respective bellows 41a and 41b can deform mildly over their entire length, thus flexibly following the revolving motion of the auxiliary ring 39 during operation without excessive stress or strain and undesired stress-concentration. This avoids a great stress from acting locally on the respective bellows 41a and 41b, both serving as a partition member.

Furthermore, this minimizes power loss (friction loss).

It is preferable that each of the previously-discussed bellows 41a and 41b comprises a flexible metal bellows. In case that the respective bellows 41a and 41b are formed of a flexible metal bellows, one end of the respective bellows (4. la; 41b) can be easily firmly connected to the side wall of the auxiliary ring 39 by way of welding, whereas another end of the bellows can be easily firmly connected to the associated bellows retaining ring (42; 43) by way of welding. As is generally known, a flexible metal bellows itself is free from degradation for a long period of time and thus has a high durability enough to stand long use. The flexible metal bellows may be made of a metal plate in a manner so as to be integrally formed into a bellows of a plurality of ridges (accordionlike walls) by means of bending, and so that the flexible metal bellows of a proper thickness and a proper number of ridges can provide a proper spring constant (or a proper flexibility) enough to allow the radial displacement (or the revolving motion) of the auxiliary ring 39. Alternatively, the flexible bellows (41a; 41b) may comprise a so-called weld bellows which is produced by integrally connecting a plurality of annular metal plates to each other by welding. Instead of a flexible metal bellows, a pair of flexible bellows (41a; 41b) may be made up of a rubber material, such as natural rubber or synthetic rubber, or a synthetic resin material. Moreover, although the flexible partition member of the shown embodiment is comprised of an accordion- like bellows, the flexible partition member may be comprised of a moderately- curved, single-ridged, thinned rubber material or thinned synthetic resin material.

As set forth above, in the radial plunger pump made according to the invention, an auxiliary ring is mounted on an eccentric cam fixed to the drive shaft so that the auxiliary ring is rotatable relative to the eccentric cam, and a partition member is provided between the auxiliary ring and the pump housing so that the partition member divides a space in the pump housing into a working-fluid chamber and a lubricant chamber, enclosing around the outer periphery of the drive shaft inserted into the pump housing. Such a simple partition structure composed of a small number of parts, can certainly prevent working fluid (fuel) from entering in and around the drive-shaft journal, thus enhancing a lubricating performance in and around the drive shaft journal and providing a good seal on the inner periphery of the oil seal, without increasing product costs and/or the size of the radial plunger pump assembly. Additionally, in the radial plunger pump of the invention, since the flexible partition member is provided between the pump housing and the auxiliary ring mounted on the eccentric cam, a rate of the maximum deflection to the axial length of the partition member can be reduced, and as a result a stress acting on the partition member is smaller, thus enhancing a durability of the partition member. Moreover, in the case that the partition member comprises a flexible bellows, the partition member can flexibly follow the - 14 revolving motion of the auxiliary ring round the drive shaft, thereby avoiding undesired stress- concentration of the partition member and minimizing power loss (the resistance to rotation of the drive shaft). In the shown embodiment, the outside end of each of the bellows (41a; 41b) is firmly connected to the associated bellows retaining ring fixed to the housing coaxially to the axis of the drive shaft and the inside end of the bellows is firmly connected to the associated side wall of the auxiliary ring slightly eccentric to the axis of the drive shaft, and whereby the flexibility of the bellows may be enhanced, thus eliminating high localized stresses in the bellows.

While the foregoing is a description of the preferred embodiments carried out the invention, it will be understood that the invention is not limitedto the particular embodiment shown and described herein, but that various changes and modifications may be made without departing from the scope of theinvention as defined by the following claims.

- is -

Claims

CLAIMS:

1. A radial plunger pump comprising:

a housing; a drive shaft rotatably supported in said housing; an eccentric cam of a circle in cross section, said eccentric cam being fixedly connected to said drive shaft so that an axis of said eccentric cam deviates from a geometric center identical to an axis of said drive shaft; a plurality of radial cylindrical bores formed in said 10 housing; is a plurality of radial plungers each accommodated in the associated one of said cylindrical bores and biased toward an outer periphery of said eccentric cam, for reciprocating motion of said plungers; each of said cylindrical bores communicating with both a suction passageway and a discharge passageway through check valves for sucking working fluid from said suction passageway on a suction stroke of the associated plunger, and for pressurizing the working fluid sucked and for feeding a pressurized working fluid to said discharge passageway on a discharge stroke of the associated plunger; an auxiliary ring fitted on the outer periphery of said eccentric cam so that said auxiliary ring is rotatable relatively with respect to said eccentric cam; and a flexible partition member provided between said auxiliary ring and said housing, for dividing a space in said housing into a working-fluid chamber and a lubricant chamber while enclosing said drive shaft, said lubricant chamber being filled with lubricant.

1) A radial plunger pump as claimed in claim 1, wherein said flexible partition member comprises a flexible bellows.

3. A radial plunger pump as claimed in claim 2, wherein said flexible bellows is formed of a flexible metal bellows.

4. A radial plunger pump as claimed in claim 2, wherein said flexible bellows is formed of a rubber material.

5. A radial plunger pump as claimed in claim 2, wherein said flexible bellows is formed of a synthetic resin material.

6. A radial plunger pump as claimed in any preceding claim, including. a drain port defined in said housing for returning working fluid in said working-fluid chamber to said suction passageway.

7. A radial plunger pump as claimed in claim 2, wherein an outside end of said flexible bellows is firmly connected to a retaining ring fixed to said housing coaxially to the axis of said drive shaft, and an inside end of said flexible bellows is firmly connected to a side wall of said auxiliary ring.

8. A radial plunger pump substantially as described with reference to, and as shown in, the accompanying drawings.