Transfer pump for injection of fuel at high pressure

Abstract

A transfer pump for the injection of fuel under high pressure of the type comprising a piston (10) providing the hydraulic liquid to a deformable bellows (14), the deformations of said bellows (14) in a cylindrical chamber (20) filled with fuel giving rise to a high pressure pumping effect of said fuel; a cam (5) provided with lugs (6) carried by a drive shaft (1), is characterized in that the oil portion of the pump comprises: the portion of the drive shaft (1) bearing the cam (5); the cam (5) and its lugs (6); the roller (7) with its shaft (8) and its roller bearing (9) carried by a bearing member (12), by which roller the cam(5) bears on the piston (10); as well as the upper portion of said piston (10); such that all the mechanical drive portion and angle change are bathed in the oil of the oil portion.

Description

[0001] The present invention relates to improvements in pumps for the injection of fuel at high pressure, of the type comprising a piston delivering hydraulic fluid into a deformable element such as a bellows, the deformations of said bellows in a cylindrical chamber filled with fuel giving rise to a pumping effect of said fuel toward high pressure injectors.

[0002] Pumps of this type have been described in U.S. Pat. No. 2,826,068, 2,828,240 and patent application 06/02594 in the name of the applicant.

[0003] The present invention has for its object to provide a solution to two problems which arise from mounting this type of pump on motors.

[0004] The first problem arises because in certain motors it is necessary to integrate the direct injection high pressure injection pump at the end of the camshaft or on the transmission pulleys and not directly on the cylinder head. In the case of the utilization of a single piston pump an angle change is necessary, which gives rise to various drawbacks such as: the size of the pump, the requirement for an adaptation housing, lubricating means, noise, wear of the elements etc.

[0005] The second problem arises because for such a mounting, it is necessary to provide an operating play between the drive means of the pump and the latter, of the Oldham joint type, for example. When the pump is single piston, there are produced large vibrations from the resistive couple of the pump, possibly even with negative peaks, which vibrations can give rise to loosening the contact surfaces which transmit the couple, which loosening generates couple returns in the motor shaft. These couple returns constitute a disturbing element for the operation of the motor such as: coupling jolts on the camshaft or timing chain, unacceptable noise.

[0006] The solution of the first problem consists in designing the pump such that the oil portion comprises not only the pumping portion but also all the drive portion and angle change.

[0007] This has the advantages: on the one hand suppression of dynamic sealing in translation on the transfer single piston pump which is very cumbersome and remains difficult to control; on the other hand all the drive elements will be perfectly lubricated. Moreover, the increase of the closed cycle oil volume increases the resistance to oil temperature and decreases the risks of heating.

[0008] The solution of the second problem consists in providing a free wheel between the drive shaft and the cam.

[0009] By way of non-limiting example, and to facilitate understanding of the invention, there are shown the following drawings, in which:

[0010] FIG. 1 is a cross-sectional view of an embodiment of the transfer pump according to the invention,

[0011] FIG. 2 is a cross-sectional view on A-A of FIG. 1,

[0012] FIG. 3 is a fragmentary view showing a modification of FIG. 2.

[0013] Referring to these drawings, it will be seen that the pump according to the invention comprises a drive shaft 1, connected by an Oldham joint 2 to the drive member (camshaft for example) not shown.

[0014] The shaft is carried by a housing 3.

[0015] The shaft carries a cam 5, which, in the illustrated example, comprises four lugs 6.

[0016] A piston 10 comes to bear by means of a spring 11 against the cam 5, with interposition between the piston 10 and the cam 5 of roller 7, carried by a shaft 8 by means a needle bearing 9.

[0017] Preferably, a bearing member 12 is interposed between the roller 7 and the piston 10. This bearing member 12 is preferably constituted by two oppositely facing cups 12a, 12b, separated by a partition 12c provided with a plurality of openings 23.

[0018] The external wall of the bearing member 12 comprises recesses which facilitate the passage of oil about this member 12.

[0019] The piston 10, urged by spring 11, slides in a sleeve 13.

[0020] The end 13a of the sleeve 13 enters a bellows 14, provided at its lower end with a circular member 15, urged by a return spring 16.

[0021] The interior within the sleeve 13 and at its end is disposed a disc 17 which comprises at its center a bore 19, in which slides a finger 18, carried by said circular member 15, at its center. This ensures correct guiding of the bellows 14 during its successive elongations. The guidance of the bellows 14 permits decreasing and best adjusting the diameter of the chamber 20 in which said bellows expands; this chamber 20 being filled with fuel.

[0022] In FIG. 1 it is seen that the cam 5 turns within a circular chamber 21 provided within the housing 3.

[0023] This chamber 21; the bore 22 within which slides the roller 7, the bearing member 12 and the upper portion of the piston 10; the internal bore 10a of said piston; the internal bore of the sleeve 13 and the interior of the bellows 14 are filled with a hydraulic liquid. This liquid passes about the member 12 and also within it where it traverses the partition 12a through the openings 23; then it enters the internal bore 10a of the piston 10 through the opening 24 and passes through the disc 17 by its openings 25.

[0024] This ensures good communication between them, of the various elements filled with oil.

[0025] There is this obtained a relatively great volume of the volume of oil which his continually pumped, which improves the lifetime of this oil and decreases the risk of heating.

[0026] To avoid the effects of pulsations adapted to be provoked by the movements of the lugs 6 of the cam 5, there can preferably be used a volume compensator 26, which communicates with the chamber 21 in which the cam 5 acts (FIG. 1).

[0027] For the same reason, there can be provided a volume compensator 27, which communicates with the bore 22 (FIG. 2).

[0028] Moreover, the non-return valve 28 is disposed in the internal bore 10a of the piston 10.

[0029] This has the result that only the portion 29 of said bore 10a, located downstream of the non-return valve 28, is placed under pressure and hence only a small volume of oil is placed under pressure, whilst the rest of the volume of oil is not pressurized. During rising movement of the piston 10, under the action of the return spring 11, the communication is re-established between the oil which has been pressurized and all the rest which has not been.

[0030] To contributes to avoiding heating of the oil.

[0031] As the shaft 1 is driven by a freewheel mechanism, the shocks which are transmitted to the came 5 are not transmitted to the drive shaft 1.

[0032] The sealing of the oil portion of the pump is ensured by a simple joint with loops 30 disposed between the shaft 1 and housing 3.

[0033] All the components of the mechanical drive portion: cam 5, roller 7 and its roller bearing 9, bearing member 12 sliding in the bore 22, are immersed in the oil and are perfectly lubricated.

[0034] FIG. 3 shows a modified embodiment of the upper portion of FIG. 2, showing the drive mechanism above the cam 5.

[0035] In this figure, the same elements bear the same reference numerals.

[0036] The cam 5 is, in this example, of one piece with the motor shaft 1, the transmission by Oldham joint 2 comprising a freewheel mechanism 3.

[0037] The portion forming a cam 5 comprises a cylindrical cup 32 in which will engage a cylindrical axle 31 with interposition between said axle 31 and the internal wall of the cup, of a guide element.

[0038] The roller bearing 4 carrying shaft 1 is located outside the housing 3, the sealing joint with loops 30 being in the housing 3, between the roller bearing 4 and the cam 5.

[0039] In this embodiment, the roller bearing 4 is not lubricated by the hydraulic oil but by the motor oil.

Claims

1. Transfer pump for injection of high pressure fuel of the type comprising a piston (10) supplying hydraulic liquid to a deformable bellows (14), the deformations of said bellows (14) in a cylindrical chamber (20) filled with fuel, giving rise to a pumping effect at high pressure of said fuel; a cam (5) provided with lugs (6) carried by a drive shaft (1), characterized by the fact that the oil portion of the pump comprises: the portion of the drive shaft (1) bearing the cam (5); the cam (5) and its lugs (6); the roller (7) with its shaft (8) and its roller bearing (9) carried by a bearing member (12), by which roller the cam (5) bears on the piston (10); as well as the upper portion of said piston (10): such that all the mechanical drive portion and the angle change bathe in the oil of the oil portion.

2. Transfer pump according to claim 1, in which the sealing between the oil portion and the drive shaft (1) is ensured by a simple joint with loops (30).

3. Transfer pump according to claim 1, in which the chamber (21) of the housing (3) in which the cam (5) works is connected to a volume compensator (26).

4. Transfer pump according to claim 3, in which a second volume compensator (27) is connected to the bore (22) in which operate the roller (7), the bearing member (12) and the upper portion of the piston (10).

5. Pump according to claim 4, in which the piston (10) comprises an internal bore (10a) communicating with said bore (22) by an opening (24) and comprises a non-return valve (28); such that the volume of oil placed under pressure is small.

6. Pump according to claim 5, in which the piston (10) sides in a sleeve (13) provided at its base with a disc (17) having a bore (19) in which slides a finger (18) carried by a member (15) fixed to the base of the bellows (14); so as to ensure the guidance of said bellows (14) during its successive deformations.

7. Pump according to claim 1, in which the shaft drive mechanism for the shaft (1) is a freewheel mechanism.