GB2026612A

GB2026612A - Rotary positive-displacement fluid-machines

Info

Publication number: GB2026612A
Application number: GB7926215A
Authority: GB
Original assignee: Barmag Barmer Maschinenfabrik AG
Current assignee: Oerlikon Barmag AG
Priority date: 1978-07-28
Filing date: 1979-07-27
Publication date: 1980-02-06
Also published as: IT7949630A0; IT1120472B; FR2433655A1; GB2026612B; DE2833167C2; FR2433655B1; DE2833167A1

Abstract

A pumping unit for a motor vehicle I.C. engine comprises a lubricating oil pump (1) e.g. of the gear type, and a vacuum pump (6) e.g. of the sliding-vane type, for the braking system. The unit is in use partially submersed in an oil sump of the engine. An oil-pump rotor (2) and a vacuum-pump rotor (8) are fixed to a rotatable hollow shaft (13) and are separated from each other by a plate (16). The delivery side of the oil pump is connected intermittently by way of channels (22, 23) in the rotor (2) and the plate (16) to a radial passage (25) in the shaft, which also comprises outlet passages communicating with oil channels (28, 29) in the vacuum- pump rotor. A further channel (17) may be formed in the plate through which oil is sucked into the vacuum pump. Alternative oil channels and passages are described with reference to Figs. 2-6a (not shown). <IMAGE>

Description

SPECIFICATION A structural unit comprising an oil pump and a vacuum pump Internal combustion engines, particularly fourstroke engines, have so-called force feed lubrication. In this type of lubrication, the lubricating oil is fed by an oil pump from an oil sump to the individual lubrication points (Dubbels Taschenbuch fur den Maschinenbau, 12th Edition, Volume II, page 206). Internal combustion engines usually have an oil filter to remove solid impurities, which is arranged in such a way that it is readily accessible and can be cleaned or exchanged easily.

Motor vehicles often have a brake power assistance unit. A brake power assistance unit comprises a pneumatic piston or membrane system which is activated by a vacuum produced by the internal combustion engine of the motor vehicle. Vacuum pumps are being used more and more to produce this vacuum.

Oil pumps are usually gear pumps. Vacuum pumps are advantageously designed as vane pumps.

The object of the invention is to combine the oil pump and the vacuum pump in a structural unit, to arrange this structural unit in the oil sump of the internal combustion engine at the position of the formerly conventional oil pump and in so doing to lubricate the vacuum pump with a controlled quantity of oii. The fact that the vacuum pump is partially submersed in the oil sump giving rise to the danger of an overflow represents a partial problem. Such an overflow would cause oil to enter the brake power assistance unit and the brake system and that would impair the operation of the brake system. Another partial problem lies in the fact that, for technical and economic reasons, it is not possible to feed the partial oil stream serving to lubricate the vacuum pump via the central oil filter of the motor vehicle.In particular, spatiai and economic reasons prevent this. It is not possible to provide a special filter between the oil pump and vacuum pump for the partial oil stream because this filter would not be accessible in the oil sump and could not therefore be cleaned or exchanged, so that the vacuum pump would inevitably stop if the filter were blocked.

According to the invention there is provided a structural unit comprising an oil pump for circulating lubricating oil in an internal combustion engine of a motor vehicle and a vacuum pump for producing a vacuum to increase the braking power of the motor vehicle, which structural unit is in use partially submersed in an oil sump of the internal combustion engine, wherein an oil pump rotor and a vacuum rotor are mounted on a common rotatable hollow shaft for rotation therewith and are separated from one another by an intermediate plate, the delivery side of the oil pump is connected via a radial branch channel and a radial passage in the casing of the hollow shaft to the interior of the hollow shaft, and the hollow shaft comprises outlet channels in the region of the vacuum pump for supplying oil to lubricate the vacuum pump.

The invention allows the lubricating oil stream between the oil pump and vacuum pump to be ensured independently of the position of the oil in the oil sump. The lower end of the hollow shaft is preferably sealed. However, if the upper end of the hollow shaft is sealed, for example by the driving shaft coming from the engine, the lower end of the hollow shaft can have a throttle passage which both ensures that sufficient pressure is built up in the hollow shaft and prevents dirt from accumulating at the bottom of the hollow shaft It is also advantageous for a throttle to re arranged in the hollow shaft between the radial passage and the axial region of the vacuum pump.

The throttle also serves to control the quantity of oil supplied to the vacuum pump. The throttle can be designed, for example, as a screw thread in the inside of the casing of the hollow shaft, which has a conveying action directed toward the oil pump in the direction of rotation of the hollow shaft.

Instead of controlling the quantity of oil supplied to the vacuum pump by means of throttling, this can be achieved by supplying an intermittent flow of oil to the vacuum pump. This can be achieved in a number of ways. One way is for the delivery side of the oil pump to be continuously tapped by means of a stationary channel system arranged in the housing, but for this channel system to be connected to the interior of the hollow shaft and therefore to the vacuum pump only perodically as a function of the rotation of the hollow shaft. Control can therefore be effected by the size of the channel system and by the number of passages arranged in the casing of the hollow shaft.

Another way is for the oil to be supplied continuously from the delivery side of the oil pump to the hollow shaft which is surrounded by an annular chamber. However, this annular chamber is also connected on one side to the suction side of the oil pump so that a pressure drop occurs in the annular chamber and leads to an intermittent flow of oil into the interior of the hollow shaft as the hollow shaft is rotated.

In one embodiment, the oil is supplied intermittently by producing the radial branch channel in a gear wheel of the oil pump. The delivery side of the oil pump is therefore only tapped intermittently.

The radial passages of the casing of the hollow shaft should be dimensioned so as to prevent a build up of pressure which would subject the hollow shaft to an additional strain.

Another way of supplying a lubricating oil stream to the vacuum pump involves providing the vacuum pump with a suction passage in its housing beneath the oil level on its suction side. In order to avoid contamination, this suction passage.

is surrounded by a filter basket which is sealed firmly at the top and is provided with a filter at the bottom.

In order to obtain an additional means of metering independently of the throttling of the suction passage in this embodiment as well, the oil is also supplied intermittently by having the suction passage arranged as a radial passage in the intermediate plate between vacuum pump and oil pump, the suction passage opening via an axial branch passage on a face of the vacuum pump rotor, this face having a radial groove or other recess between this opening and its circumference.

Oil lubrication can also be performed by connecting the delivery side of the oil pump to the housing of the vacuum pump by means of a throttle channel so that a metered quantity of oil enters the housing of the vacuum pump through the throttle channel.

Another partial problem during the oil lubrication of the vacuum pump which is combined to form a structural unit with the oil pump lies in the oil outlet. The lubricating oil outlet of the vacuum pump preferably lies above the maximum oil level. This prevents oil from running back into the vacuum pump when the internal combustion engine is stationary. Quantities of lubricating oil which cool down when the internal combustion engine is stationary would make the vacuum pump incapable of operating during the start up of the internal combustion engine if the oil were then in the vacuum pump. The oil outlet channels can be directed horizontally so as to prevent heavy particles of dirt from falling into the oil outlet channel.It is particularly advantageous for the oil outlet channels from the vacuum pump to lie with their outlet openings above the maximum oil level in a generally vertical chicane wall on the side remote from the internal combustion engine. This not only avoids oil running back into the vacuum pump when the engine is stationary, but also has the effect that the outlet openings of the oil outlet channel or channels are protected in the lee of the chicane wall from the oil whirled round by the engine connecting rod.

It should be emphasised that the oil lubrication of the vacuum pump in the structural unit consisting of oil pump and vacuum pump generally demands several of the means proposed above both with respect to the supply of the oil and with respect to the discharge of the oil in order to achieve sufficient lubrication at all points of the vacuum pump and to prevent oil from accumulating at any point in the vacuum pump.

In the accompanying drawings: Figure 1 shows a structural unit composed of the oil pump and vacuum pump; and Figures 1 a and Figures 2 to 6 show ways of lubricating the vacuum pump with oil through special channel systems.

The unit illustrated in Figure 1 is arranged in the oil sump of an internal combustion engine and is slightly inclined to the horizontal, as can be seen from the oil level indicated by V, which is of course horizontal. The unit comprises an oil pump 1 having gear wheels 2 and 3 which mesh with each other and are mounted in a housing 4. The suction opening of the oil pump is designated by A in Figure 1 a. An outlet nozzle 5 communicates with the delivery side D of the oil pump.

The vacuum pump 6 is in the form of a vane pump and comprises four vanes 7, only two of which are shown in Figure 1. These vanes can perform a movement with a radial component in a rotor 8. The rotor is eccentrically mounted in a housing 9 so that the vanes form chambers with the rotor and the pump housing which change in volume during rotation. Pins 10 serve to guide the vanes 7. The vacuum nozzle is designated by 11.

The oil and air outlet opening 12 opens into the oil sump, above the oil level and in a generally horizontal direction so that neither drops of oil nor dirt can fall into the opening. The gear wheel 2 and the rotor 8 are mounted on a common hollow shaft 13. The hollow shaft 13 is coupled to a drive shaft 14 by a hexagonal coupling and is by the internal combustion engine. The gear wheel 3 is cantilevered on a shaft 15. The gear wheel 3 is entrained by the gear wheel 2. The oil pump and the vacuum pump are separated from each other by an intermediate plate 16. The oil pump housing 4 and vacuum pump housing 9 are rigidly connected to each other. The hollow shaft 13 is mounted at the end in hydraulic bearings.An oil channel 1 7 comprises an initial radially directed section followed by an axially directed section which opens opposite of a face of the rotor 8 of the vacuum pump 6 is arranged on the suction side of the pump, i.e. in the region of the angle a shown in Figure 1a in the intermediate plate 16, beneath the minimum oil level, to lubricate the vacuum pump with oil. A radial groove 20 in the rotor is in communication with the end of the oil channel 17 and extends to the circumference of the rotor. The opening into the oil channel 1 7 is covered by a cage 18. The cage 18 is sealed at the top and has a filter 19 at the bottom. The cage and filter prevent dirt from entering the channel 17.

A discontinuous oil stream is sucked into the vacuum pump by the oil channel 17 and the radial groove 20 owing to the vacuum prevailing in the vacuum chamber. The frequency of the oil supply depends on the speed and also on the number of radial grooves 20 in the rotor 8. It should be mentioned that a plurality of oil channels 1 7 can be provided on the vacuum side of the vacuum pump. The quantity of oil supplied can be controlled by the size and number of the oil channels 17 or radial grooves 20 so that an excess of oil is avoided in the vacuum pump.

In order to supply oil to the delivery or outlet side of the vacuum pump as weli, it is possible to provide an oil overflow channel 21 between the outlet channel 5 and the vacuum pump. This can be provided alone or in addition to the oil channel 17 and radial groove 20.

The oil channel system described below is provided in order to lubricate the vanes 7 as well as the bearings of the hollow shaft 13. The gear wheel has on its end adjacent the intermediate plate 16 a gear wheel face groove 22 which extends from the circumference of the face in a radial direction, and ends somewhere on the face. As the gear wheel 2 rotates, a groove 23 in the intermediate plate forms with the groove 22 an intermittently opened and closed channel which communicates with an annular chamber 24. A radial passage 25 of the casing of the hollow shaft communicates with the annular chamber 24.

Figure 1 a shows that the groove 23 lies in the region of the angle P, i.e. in the delivery region of the gear pump. A pulsating oil stream is consequently led into the interior of the hollow shaft 13 via groove 22, groove 23, annular chamber 24 and radial passage 25. The hollow shaft is sealed at one end by the drive shaft 14 and at the other end by a stopper 26. The stopper 26 has a small passage 27 to prevent dirt from accumulating at the bottom of the hollow shaft so that a portion of the oil stream led into the hollow shaft passes through this passage as the contamination falls. Moreover, the lubricating oil stream passes from the interior of the hollow shaft through lubricating oil passages 28 as well as guide passages 29 for the pins 7 into chambers 30 at the radially inner ends of the vanes 7.The oil forms an oil film on both sides of the vanes during the radial movement of the vanes 7. The chambers 30 have an opening or openings 31 to avoid a situation in which insufficient oil enters the chambers 30 through the passages 28 or the guides 29 during rapid movement of the vanes, i.e.

at high speeds of the internal combustion engine or with a cold and therefore highly viscous oil, and where the oil accumulates in the chambers 30 and thus obstructs free radial movement of the vanes. The openings 31 are preferably arranged on the suction side of the vacuum pump, i.e. in the region of the angle a shown in Figure 1 a. To prevent oil or contamination from penetrating into the suction openings 31, the mouths of the openings 31 are arranged above the oil level in a rib 32, on that side of the rib 32 which is remote from the vertical axial plane 33 of the motor shaft (not shown). This ensures that oil spray produced by the movement of the connection rod 34 does not enter the mouths of the openings 31.

Figure 2 shows another method of supplying oil to the vacuum pump and in particular of lubricating the bearings of the hollow shaft and the vanes. This method can replace those just described, or can, if necessary, be used in addition.

Figure 2 also demonstrates how the oil is supplied intermittently. A radial groove 35 is arranged in the oil pump housing 4 and extends on the delivery side of the pump (see angle p in Figure 1 a) from the circumference of the gear wheel 2 to the outer casing of the hollow shaft 13. The radical groove 35 is continued there in an axial groove. The radial passage 37 of the casing of the hollow shaft lies in the region of this axial groove.

The quantity of oil conveyed into the interior of the hollow shaft can be controlled by the number and size of the radial passage 37 or size of the radial and axial groove. In order to prevent too great a pressure drop in the region of the oil pressure pump owing to the supply of oil through the radial groove 35, axial groove 36 and radial passage 37, the interior of the hollow shaft 1 3 is provided with a throttle. This throttle can, as illustrated in Figure 2, consist of an internal screw thread which has a conveying action in the direction of the stopper 26 with the predetermined direction of rotation (see Figure 1 a). The stopper 26, in turn, has a passage 27 which is small enough to prevent a pressure drop but large enough to ensure that impurities can pass out through it.Figure 2 shows only part of the unit the rest being as shown in Figure 1 and Figure la.

Figure 3 again shows a partial section in which an oil inlet 38 is provided in the casing 9 of the vacuum pump. The oil inlet 38 lies on the suction side of the pump, i.e. in the region of the angle a shown in Figure 1a. This oil inlet passage 38 is very small so that the oil stream is throttled sufficiently. The oil inlet passage 38 is prevented from becoming contaminated and clogged by the cage 18 with filter 19. The rest of the unit is as shown in Figure 1.

The partial section in Figure 4 shows an arrangement which can replace that shown in Figure 2 and can be adapted selectively in addition to the other methods indicated or by itself to solve the problem of lubricating the vacuum pump with oil. According to Figure 4, an oil channel 39 is provided in the oil pump housing 4, the channel 39 having an axial portion and a radial portion and extending from the circumference of the gear wheel 2 to the casing of the hollow shaft 13. The oil channel 39 is in alignment with the radial passage 40 in the casing of the hollow shaft. The hollow shaft is sealed by a stopper 26. A throttle stopper 41 with a throttle passage 42 is used instead of the screw thread shown in Figure 2 and prevents too great a pressure drop on the delivery side of the oil pump.

The partial section in Figure 5 shows another method which can replace that of Figure 2 or 4 and can be used selectively in addition to any of the other methods or by itself. The oil channel guide shown in Figure 5 comprises a radial face groove 43 in the gear sheel 2 and an axial groove 44 in the oil pump housing 4. A radial passage 45 of the casing of the hollow shaft lies in the region of the face groove 44. A throttle is indicated diagrammatically by reference numeral 46, and could for example rate the form of the throttle shown in Figure 2 or that shown in Figure 4.

Figures 6 and 6a show a structural unit which is substantially the same as that shown in Figures 1 and 1 a, except that the annular channel 24 and the radial passage 25 are joined by a radial groove 48 arranged in the intermediate plate 1 6. This radial groove 48 extends in one stretch from the delivery side of the oil pump (angle p in Figure 6a) to the annular chamber 24 so that the annular chamber 24 is charged with a continuous oil stream. The radial suction channel 47 is provided on a side of the annular chamber 24 remote from the radial groove 48 and connects the annular chamber with the suction side of the oil pump. A pressure drop is thus produced in the annular chamber 24 from the mouth of the radial groove 48 to the mouth of the suction channel 47. A pulsating oil stream consequently only flows through the radial passage 25 of the casing of the hollow shaft 1 3.

Using an intermittent and pulsating oil supply and supplying the oil from the oil tank directly into the vacuum pump has the result that there is no risk of the oil pressure produced by the oil pump dropping to an undesirable extent, but at the same time the oil channels to the vacuum pump can be made sufficiently large for the unavoidable impurities in the oil tank not to lead to blockages.

Claims

1. A structural unit comprising an oil pump for circulating lubricating oil in an internal combustion engine of a motor vehicle and a vacuum pump for producing a vacuum to increase the braking power of the motor vehicle, which structural unit is in use partially submersed in an oil sump of the internal combustion engine, wherein an oil pump rotor and a vacuum rotor are mounted on a common rotatable hollow shaft for rotation therewith and are separated from one another by an intermediate plate, the delivery side of the oil pump is connected via a radial branch channel and a radial passage in the casing of the hollow shaft to the interior of the hollow shaft, and the hollow shaft comprises outlet channels in the region of the vacuum pump for supplying oil to lubricate the vacuum pump.

2. A unit according to claim 1, wherein the radial branch channel is made in a housing of the oil pump and has an outlet which opens onto the casing of the hollow shaft in the region of a hollow shaft bearing designed as a sliding bearing, and wherein the radial passage of the casing of the hollow shaft lies in the same normal plane as the outlet of the branch channel.

3. A unit according to claim 1, wherein the radial branch channel is made in a housing of the oil pump and has an outlet which opens on to the casing of the hollow shaft in the region of a hollow shaft bearing designed as a sliding bearing, an axially extending groove is connected to the outlet of the branch channel, and the radial passage extends through the casing of the hollow shaft, axially offset relative to the outlet of the branch channel, but in the region of the axially extending groove.

4. A unit according to any preceding claim, wherein the branch channel is in the form of a groove or other recess in a face of the oil pump housing.

5. A unit according to claim 3, wherein the axially extending groove is machined in the bearing bush.

6. A unit according to claim 3, wherein the axially extending groove is machined in the hollow shaft.

7. A unit according to claim 1, wherein the radial branch channel communicates with an annular chamber surrounding the casing of the hollow shaft and is connected to the radial passage of the casing of the hollow shaft.

8. A unit according to claim 7, wherein the annular chamber is connected at a location remote from the outlet of the radial branch channel to the suction side of the oil pump via a duct of narrow cross-section.

9. A unit according to claim 8, wherein the said duct is formed by a small suction groove which extends in a radial direction from the annular chamber to the suction side of the oil pump.

10. A unit according to any preceding claim, wherein the oil pump is a gear pump.

11. A unit according to any preceding claim, wherein the vacuum pump is a vane pump.

12. A unit according to any preceding claim, wherein at least the lower end of the hollow shaft is sealed.

13. A unit according to any preceding claim, wherein the end of the hollow shaft has a throttle passage.

14. A unit according to any preceding claim, wherein the hollow shaft has a throttle between the radial passage of the casing of the hollow shaft and the axial region of the vacuum pump.

15. A unit according to claim 14, wherein the throttle is provided by a screw-thread in the inside of the casing of the hollow shaft.

1 6. A unit according to claim 15, wherein the throttle screw thread has a conveying action directed towards the oil pump in the direction of rotation of the unit.

17. A unit according to any preceding claim, wherein the radial branch channel is in the form of a gear wheel.

18. A unit according to claim 17, wherein the radial branch channel is flush with the radial passage in the casing of the hollow shaft.

1 9. A unit according to claim 18, wherein the radial branch channel is connected via a stationary axial channel in the housing to the radial passage in the casing of the hollow shaft.

20. A unit according to any one of claims 1 7 to 19, wherein the radial branch channel is composed of a groove on the face of the gear wheel which groove extends only over a portion of the radius of the gear wheel and of a radial groove which extends in the end wall adjacent this face between the casing of the hollow shaft and the end of the groove in the face of the gear wheel, and the hollow shaft is surrounded by an annular chamber with which the radial groove and the radial passage in the casing of the hollow shaft both communicate.

21. A unit according to any preceding claim, wherein the radial passage has a larger crosssection in the casing of the hollow shaft than the radial branch channel.

22. A unit comprising an oil pump for circulating lubricating oil in an internal combustion engine of a motor vehicle and a vacuum pump for producing a vacuum to increase the braking power of the motor vehicle, which structural unit is in the use partially submersed in an oil sump of the internal combustion engine, in particular according to any one of the preceding claims, wherein the vacuum pump has a suction passage in its housing beneath the surface of the oil on its suction side.

23. A unit according to claim 22 wherein the suction passage is a radial passage arranged in the intermediate plate between vacuum pump and oil pump, the suction passage opening via an axial branch passage on a face of the vacuum pump rotor the face of the vacuum pump rotor having a radial groove or other recess radially between this opening and its circumference.

24. A unit according to claim 22 or 23, wherein the suction passage is surrounded by a filter basket which is firmly sealed at the top and is provided at the bottom with a filter.

25. A unit comprising an oil pump for circulating lubricating oil in an internal combustion engine of a motor vehicle and a vacuum pump for producing a vacuum to increase the braking power of the motor vehicle, which structural unit is in use partially submersed in an oil sump of the internal combustion engine, in particular according to any preceding claim, whrein the delivery channel of the oil pump is connected via a throttle passage to the vacuum pump.

26. A unit according to any preceding claim, wherein the lubricating oil outlet of the vacuum pump lies above the maximum oil level.

27. A unit according to any preceding claim, wherein the outlet openings of the oil outlet channels are above the maximum oil level and lie in a generally vertical chicane wall on the side remote from the internal combustion engine.

28. A unit comprising an oil pump and vacuum pump, substantially as herein described with reference to any one of the embodiments shown in the accompanying drawings.