HYDRAULIC PUMP FOR A VEHICLE ENGINE

Abstract: A hydraulic pump in the form of an oil pump (12) for a vehicle engine has both its pinion (21) which is driven by the engine's crankshaft (3), and a ring-gear (22) which cooperates with the pinion (21), incorporated in an end-cover (11) fastened to the end of the engine block (2). A cap (15) is inserted in a collar (14) on the side of the end-cover facing away from the engine and is only held in position there by means of a locking ring (17) which engages with a groove (16) in the collar and presses the cap (15) towards the engine. Outside the oil pump, a partly socket-shaped belt pulley (7) is mounted on the crankshaft (3) and its socket-shaped portion substantially grips the collar. Fitting and removal are thus simplified and engine overall length reduced. Simplified sealing also reduces oil leakage risks.

Description: Hydraulic pump for a vehicle engine The present invention concerns a hydraulic pump, especially an oil pump, for a vehicle engine, provided with a pinion driven by the engine's crankshaft and with a centre-displaced ring- gear cooperating with it, and the pinion and the ring-gear are enclosed in a pump housing formed by an end cover fastened to the engine and another part secured thereto, of which at least the end cover has an aperture for the crankshaft. The use of an oil pump in the form of a gearpump which is installed concentrically about, and is driven by, the engine's crankshaft is known for vehicle engines with pressure lubrication system. According to a usual design, the oil pump gear-wheel is placed in a separate pump housing which is bolted firmly to sealing contact with the outside of an end cover which is placed on one end of the engine block and creates together with the sides of the engine block part of the seal of the inside of the engine. This end-cover preferably forms a transmission cover which contains the engine's camshaft transmission and possibly also its balance- shaft transmission, both of which are driven by a drive placed on the end of the crankshaft. Outside the oil pump, there has usually been outermost on the end of the crankshaft a belt pulley for driving various auxiliary units such as cooling- water pump, generator and steering servo-pump. In such cases the end of the crankshaft passes through both the end-cover and the separate pump housing, which have cooperating machined planar contact surfaces which have to be sealed against leakage from the oil pressurised in the oil pump. The conventional version of the separate pump housing with all the feed and delivery ducts integrated in the pump housing has given the pump housing irregular contours. The seal between the contact planes is provided by an O-ring which is fitted in a groove in the contact plane of the pump housing and follows the irregular contours of the oil pump. This design results in relatively time-consuming fitting and removal of the oil pump, as a number of screws placed around the periphery of the pump housing are required for the fixing and sealing contact of the pump housing on the end-cover. Fitting a separate pump housing on the outside of the engine block end-cover also increases the engine's overall length. The irregular seal also entails leakage risks, as the O-ring may spring out of its groove while being fitted. According to US-A-4382756, fixing a cap in a pump housing by means of a grooved ring with circular cross-section is known per se in a hydraulic pump. In such cases the cap covers the shaft end and provides its bearing. To ensure good pump function, internal parts of the pump are spring- loaded towards the cap, which is thus pressed outwards and held against the locking ring. Also known in another context is the fitting of a circular end-cap to a turbo-unit by means of a locking ring which is bevelled so as to press the cap inwards. The intention is to make it possible to fit the cap in the desired rotational position relative to the turbo-unit housing. The automotive industry is increasingly endeavouring to simplify manufacture and assembly, but none of the previously known solutions for gearpumps installed about crankshaft ends achieves the desired simplicity in the case of an engine- mounted hydraulic pump. One object of the invention is to achieve a hydraulic pump which is intended for a vehicle engine and is simpler and quicker to fit than previously. Another object is to make it possible to reduce the overall length of a vehicle engine with a hydraulic pump placed around and driven by the engine's crankshaft. A further object is to simplify and improve the sealing of this type of hydraulic pump. These objects are achieved according to the invention by the features stated in the characterising portion of claim 1. According to a particularly advantageous embodiment, the first part consists of an end-cover which together with the sides of the engine block encloses the inside of the engine laterally. This end-cover may preferably be a transmission cover which contains at least a transmission driven by the crankshaft. Using the end-cover of the engine block to form a pump housing which is closed by a cap secured only by a locking ring allows substantially simpler fitting and removal than previously. The fact that the oil pump's axial enlargement of the engine can thus be reduced makes it possible to pack the parts belonging to the engine closer together in the axial direction, thus reducing the overall axial length of the engine. This has great advantages in that the engine can be made accessible even on vehicles with little engine space, and/or other equipment in available engine space can be packed tighter. The invention is explained below in greater detail by means of an embodiment example illustrated in the accompanying drawings, in which : Fig. 1 shows a longitudinal section through an oil pump according to the invention, along the line I-l in Fig. 2, Fig. 2 shows a front view of an oil pump according to the invention, with cap removed, Fig. 3 shows a section along the line Ill-Ill in Fig. 2, Fig.4 shows a section along the line IV-IV in Fig. 2, Fig. 5 shows a section along the line V-V in Fig.2, Fig.6 shows a section VI-VI in Fig. 2, Fig.7 shows a section along the line VII-VII in Fig.2, and Fig. 8 shows an enlarged detail of Fig. 2. In an internal combustion engine 1 illustrated in Fig. 1, one end of a crankshaft 3 mounted in the engine block 2 protrudes from the latter. Starting from the engine block 2, the crankshaft end successively bears an inner sprocket 4, an outer sprocket 5, a dog 6 and a belt pulley 7, all of which are fitted nonrotatably on the crankshaft end by means of a key 8. The sprocket 4 drives via a chain 9 the engine's two camshafts (not shown) and the sprocket 5 correspondingly drives via a chain 10 the engine's two balancing-shafts (not shown). These two chain transmissions run in the inside of the engine, are lubricated by the engine's oil lubrication system and are enclosed in a normal manner by an end-cover 11 fastened to the end of the engine block 2. The end-cover 11 accommodates an oil pump 12 which is driven by means of the crankshaft 3 and the dog 6 and is connected by a suction line 13 to an oil sump at the bottom of the engine. As illustrated in Fig. 1 , the end-cover 11 is provided with a surrounding collar 14 which faces away from the engine block 2 and supports internally a cap 15. A locking ring 17 fitted in a groove 16 in the collar 14 holds the cap 15 in position in the collar 14. The cap 15 seals partly by means of a seal 18 of the O-ring type placed in a circumferential groove in the cap, against the inside of the collar 14 on the end-cover 11 and partly by means of a seal 19 of the shaft seal type against a neck 20 of the belt pulley 7. Should there be no belt pulley on this crankshaft end, the cap 15 may coverthe crankshaft end. In Fig.2, the belt pulley 7 and the cap 15 have been removed to show more clearly the inside of the oil pump 12. As illustrated, the dog 6 meshes with a pinion 21 which meshes in turn with a centre-displaced internally toothed ring-gear 22. The pinion 21 and the ring-gear 22 have between them in a usual manner a crescent-shaped spacing device 23 which is here integral with the end-cover 11 and is situated in the same cavity as the pinion 21 and the ring-gear 22. The suction side of the pump 12 is connected to the engine's oil sump via an inlet 24, a suction duct 25 and the suction line 13. From the pump outlet 26, oil on the pump's pressure side is supplied to the lubrication points in the engine via a pressure reducing valve 27 placed in the transmission cover 11. Oil returning from the pressure reducing valve 27 can reach the pump's suction side via a return port 28. To reduce the load on the seal 19 between the cap 15 and the belt pulley 7 there is in the cap 15 (see Fig.3) a drain duct 29 to remove leakage oil. The drain duct 29 is connected to the engine's crankcase and oil sump via a duct 30 in the end- cover 11. On the inside of the cap 15 is a groove 31 which runs along the pinion 21 along part of the latter's periphery (see Figs. 1 and 2) on the pump's suction side. This groove communicates with the pump's pressure side and has the function, by means of pressurised oil, of preventing air being drawn in radially from the crankshaft 3. The tightness of the pump is thus improved. As shown in Fig.4, pressurised oil runs from the outlet 26 via a duct 32 and the pressure reducing valve 27 to a distribution duct 33 which is situated in the engine block 2 and from which it can in known manner be distributed in the engine. The duct 32, which is horizontal, communicates via a vertical duct 34 and a pressure control device not shown here in detail with a return duct 35 via which oil can make its way back to the return port 28 of the pump 12. For fastening to the engine block 2, the end-cover 11 is provided with a number of screw holes 36, some of which are shown in Figs. 2 and 6. The more detailed design of the arrangement for fixing the cap 15 in the collar 14 of the end-cover 11 is illustrated in Fig. 8. The locking ring 17 is of the well-known Seger ring type and is held in place in the groove 16 by the fact that it springs radially outwards. The cap 15 is thus effectively locked in the collar 14, but is extremely easy to fit and remove. As illustrated, the wall 37 (on the left in Fig.8) of the groove 16 is somewhat inclined so that the groove 16 broadens radially inwards. The locking ring 17 is of substantially rectangular cross-section but has in its radial outer portion a chamfer 38 which matches the angle of inclination of, and is intended to cooperate with, the wall 37. The result is that upon radial expansion of the locking ring 17 (depicted in broken lines) it endeavours to move inwards towards the engine block 2, thereby urging the cap 15 to move in the same direction and consequently press the parts of the pump together to create between them good axial contact without play. This means that the thickness of the cap 15, as also the placing of the groove 16 in the axial direction, can be varied within certain limits without jeopardising the functioning of the pump, with consequent great advantages both during manufacture and during fitting. It is according to the invention essential that the locking ring 17 and the groove 16 cooperate in such a manner that the locking ring, when it expands in the groove, simultaneously moves towards the engine. This can also be achieved with an unchamfered locking ring but the version with chamfered locking ring illustrated is more advantageous from the force transmission point of view and creates better contact between the locking ring and the cap. The function intended can also be achieved with shapes of locking ring and groove other than shown here. As clearly shown in Fig. 1 , the belt pulley 7 may be so designed as at least partly to enclose the collar 14, thus allowing it to be placed closer to the engine block 2 than was previously possible. This contributes to achieving a desired shorter overall engine length. The simplified design of the oil pump 12 is advantageous from both the manufacturing and the fitting points of view. The engine end-cover and the pump housing incorporated in it can preferably be preassembled as a unit, thereby reducing engine assembling time. All that has to be done after the pinion 21 mounted in the end-cover and accompanied by the end cap has been engaged with the dog 6 is to tighten the screws of the end-cover. Inspection and servicing of the hydraulic pump are also facilitated, as all that has to be removed after the belt pulley is the locking ring and the cap. Engine assembly is also facilitated by the fact that the pressure reducing valve 27 is also incorporated in the transmission cover 11.

Claims: Claims 1. Hydraulic pump, especially an oil pump, for a vehicle engine, provided with a pinion (21) driven by the engine's crankshaft (3) and with a centre- displaced ring-gear (22) which cooperates with the pinion (21), the pinion and ring- gear being enclosed in a pump housing formed by an end cover (11) fastened to the engine and by another part (15) secured to the end- cover (11), of which at least the end-cover has an aperture for the crankshaft, c h aracterised in that the first part (11) has not only an axial cavity intended for the pinion (21) and the ring-gear (22) but also a collar (14) facing axially away from the engine and placed around the cavity, that the collar (14) is designed so that its inside centres the other part (15), which takes the form of a cap, so as to close the cavity, and that there is inside the collar (14) a peripheral groove (16) for a locking ring (17) which is so placed that by cooperating with the groove (16) it urges the cap (15) towards the interior of the cavity. 2. Hydraulic pump according to claim 1, characterised in that the groove (16) broadens radially inwards and that the groove's side (37) is planar and is inclined radially inwards away from the cavity so that when the locking ring (17) expands radially in contact with the latter the locking ring moves towards the interior of the cavity. 3. Hydraulic pump according to claim 2, characterised in that the locking ring (17) is of substantially rectangular cross-section but with a chamfer (38) on the radial outer portion of one side. 4. Hydraulic pump according to any of claims 1-3, characterised in that between the inside of the collar (14) and the shell surface of the cap (15) which matches the inside of the collar there is a seal (18), suitably in the form of an O-ring seal, placed in a peripheral groove in the cap. 5. Hydraulic pump according to any of claims 1-4, ch aracterised in that the cap (15) has a hole for the outer end and that this hole has in it a seal (19) which is intended to seal against a device connected to the outer end of the crankshaft, suitably a neck portion (20) of a belt pulley (7). 6. Hydraulic pump according to any of claims 1-5, characterised in that a crescent-shaped spacing device (23) intended to be located between the pinion (21) and the ring-gear (22) is integral with the end- cover (11). 7. Hydraulic pump according to any of the foregoing claims, ch a racte r i s e d in that the end-cover (11 ) takes the form of a transmission cover which contains at least one transmission driven by the crankshaft (3). 8. Hydraulic pump according to any of the foregoing claims, ch a racte r i s e d in that the collar (14) is surrounded radially externally by a portion of a partly socket-shaped belt pulley (7) fitted axially outside the pump (12) so that the socket-shaped part of the belt pulley and the collar are at least partly in the same plane as one another.

Inventors: BUELOW PER-ANDERS, NILSSON PER-INGE, BUELOW, PER-ANDERS, NILSSON, PER-INGE
Applicants: SAAB AUTOMOBILE, SAAB AUTOMOBILE AKTIEBOLAG
Application year: 1992
Main classification: F01M1
IPC codes: F01M1, F02B63, F02B67, F04C2, F04C11