Method for lubricating an interface between a piston of a pump and a shaft and system implementing such a method

Abstract

This method of lubricating an interface (26) between a piston (8) of a pump (4) for compressing a fluid and a shaft (18) configured to drive the piston (8) comprises projecting a jet (24) of a lubricating fluid directed towards the interface (26). Figure for abstract: Fig 1.

Description

Title of the invention: Method for lubricating an interface between a pump piston and a shaft and system implementing such a method Technical field

[0001] The present invention relates to the lubrication of an interface between a piston of a pump for compressing a fluid and a camshaft driving the piston.

[0002] In particular, the present invention relates to a lubrication method and a system implementing such a method comprising a nozzle for projecting a jet of a lubricating fluid towards the interface in order to lubricate the piston and the cam.

[0003] Generally, the present invention applies to any need for lubrication of a piston driven by a cam. Previous techniques

[0004] A piston-type high-pressure fuel injection pump makes it possible to distribute fuel to the fuel injectors of a thermal engine of a motor vehicle at a high pressure, the pressure of a high-pressure injection pump reaching, for example, a pressure of 500 bars.

[0005] The pump comprises a piston driven by a cam of a camshaft of the engine to compress the fuel, for example gasoline.

[0006] The movement of the piston in a cylindrical housing surrounding the lower part of the piston requires lubrication to prevent the piston from seizing in the housing.

[0007] According to the prior art, lubrication is carried out by means of an oil conduit opening into the housing so as to lubricate the piston and the housing.

[0008] The oil then flows along the piston by gravity and lubricates the cam.

[0009] Such a lubrication method is not suitable for engines with a compact structure, particularly due to a lack of space near the piston housing to convey the oil.

[0010] In addition, the oil is not directed towards an interface between the piston and the cam. The lubrication is carried out indirectly, reducing the quantity of oil lubricating the interface and potentially causing phenomena of flaking and tearing of material (well known as "pitting corrosion" in English).

[0011] Furthermore, with such a method, seizure phenomena between the piston and its housing have been observed.

[0012] Publication FR-A1-3013774 discloses a high pressure fuel injection pump for an engine comprising a tappet including a tappet body, a tappet shaft fixed rotation relative to the tappet body, a roller mounted to rotate relative to the tappet body around the axis of rotation and a bearing arranged between the axis of rotation and the roller, the roller being capable of cooperating with a cam secured to a crankshaft of the engine. Lubricating elements of the bearing are formed in the material of the axis of rotation.

[0013] However, this solution requires a complex modification of a roller rotation shaft. Statement of the invention

[0014] The present invention therefore aims to overcome all or part of the aforementioned drawbacks and in particular proposes a simple solution to implement in order to carry out precise and low-cost lubrication of an interface between a piston of a pump for compressing a fluid and a shaft driving the piston.

[0015] The present invention relates to a method for lubricating an interface between a piston of a pump for compressing a fluid and a shaft configured to drive the piston, comprising the projection of a jet of a lubricating fluid directed towards the interface. This method further allows the lubrication of an interface between said piston and its housing in the pump.

[0016] The present invention is of simple structure which allows it to be adapted to numerous piston pump structures, in particular high pressure fuel injection pumps of compact structure engines comprising a piston for compressing the fuel.

[0017] Advantageously, the method comprises guiding the lubricant jet so that the lubricant jet flows over a portion of the piston.

[0018] The present invention also relates to a system for pressurizing a fluid comprising a shaft, a pump comprising a piston for compressing a fluid, and a lubrication device, the shaft being configured to drive the piston, the lubrication device comprising a nozzle configured to project a jet of a lubricating fluid directed towards an interface between the piston and the shaft.

[0019] Advantageously, the pump comprises a casing housing the piston and a deflector formed in the casing so that the jet of lubricating fluid is deflected by the deflector and flows over a portion of the piston.

[0020] Optionally, the pump includes a high pressure fuel feed pump.

[0021] Advantageously, the nozzle comprises a calibrated orifice controlling the flow rate of the lubricating fluid.

[0022] The present invention also relates to a lubricating fluid cover for a thermal engine of a motor vehicle comprising a system for placing under pressure pressure as defined previously, the lubricating fluid tank comprising a supply channel feeding the nozzle.

[0023] Advantageously, the nozzle and the pump are arranged in the lubricating fluid tank so that the jet of lubricating fluid falls back to the bottom of the lubricating fluid tank under the effect of gravity.

[0024] The present invention also relates to a heat engine comprising a lubricating fluid tank as defined above.

[0025] The present invention also relates to a motor vehicle comprising a heat engine as defined above. Brief description of the drawings

[0026] Other objectives, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

[0027] [Fig-1] schematically illustrates a heat engine according to the invention;

[0028] [Fig.2] schematically illustrates an example of the embodiment of a system for putting under pressure of a fluid according to the invention; and

[0029] [Fig.3] schematically illustrates a motor vehicle according to the invention.

[0030] Detailed description of at least one embodiment

[0031] [Fig.l] schematically represents an example of a thermal engine 1 comprising a lubricating fluid tank 2 comprising for example a cylinder head of the thermal engine 1.

[0032] The lubricating fluid tank 2 comprises a system 3 for pressurizing a fluid. The system 3 comprises, for example, a high-pressure fuel injection pump 4 comprising a casing 5, a suction inlet 6 connected, for example, to a fuel tank, an outlet 7 connected, for example, to an injection rail, a piston 8 comprising at a first end a piston head 9, a cylinder 10 connected to the suction inlet 6 and to the outlet 7, and a lubrication device 11.

[0033] The piston head 9 translates in the cylinder 10 to form a compression chamber 12 so as to compress the fuel.

[0034] The piston 8 comprises at a second end a pusher 14 housed in a housing 15 of the casing 5, for example of cylindrical shape, in contact with a boss 16 of a shaft 18 driven by a crankshaft of the thermal engine 1.

[0035] The pump 4 further comprises a return spring 20 inserted between the casing 5 and the pusher 14.

[0036] Boss 16 pushes piston 8 into cylinder 10 to compress the fuel.

[0037] The return spring 20 exerts a return force on the piston 8 when the boss 16 is no longer in contact with the pusher 14 so that the pusher 14 is in contact with tree 18.

[0038] The pressurizing system 3 comprises a lubrication device 11 comprising a nozzle 22 projecting a jet 24 of a lubricating fluid towards an interface 26 between the piston 8 and the shaft 18 so as to lubricate the interface 26.

[0039] Depending on the position of the shaft 18, the interface 26 is defined as being the contact surface between the boss 16 and the pusher 14 or between the shaft 18 and the pusher 14.

[0040] Advantageously, the housing 15 is integrated into the casing 5 of the pump 4. In another embodiment, the casing 5 is a part added to the pump 4 or formed in the lubricating fluid tank 2 of the thermal engine 1.

[0041] A wall of the lubricating fluid tank 2 comprises an opening into which the nozzle 22 is inserted, comprising an orifice 28 calibrated to control the flow rate of the sprayed lubricating fluid.

[0042] The nozzle 22 is for example shrunk into the opening or screwed so as to be less sensitive to machining chips from the lubricating fluid tank 2. In another embodiment, the nozzle 22 makes it possible to spray the lubricating fluid in the form of fine droplets of lubricating fluid.

[0043] The lubricating fluid is for example oil coming from a lubrication circuit of the thermal engine 1, taken from the lubricating fluid tank 2 (also called “oil tank”) of the engine 1 via a pump (not shown) and a supply channel 30.

[0044] The lubricating fluid is sprayed by the nozzle 22 towards the interface 26 so that the lubricating fluid directly sprays the interface 26. The lubricating fluid sprays the pusher 14 and flows onto the shaft 18, preventing the connection between the shaft 18 and the pusher 14 from seizing. In addition, a portion of the fluid that sprays the pusher 14 rises into the housing 15 during the translation of the pusher 14, which reduces the risk of seizing at the interface between the pusher 14 and the housing 15.

[0045] The lubricating fluid joins the lubricating fluid tank 2 by gravity.

[0046] According to another particularly advantageous embodiment illustrated in [Fig.2], the lubrication device 11 comprises the nozzle 22, and a deflector 32 of the pump 4 is formed in the housing 15, for example by molding the casing 5.

[0047] The nozzle 22 is oriented so as to direct the lubricating fluid towards the deflector 32, for example formed as a flare of the housing 15. The jet 24 of the lubricating fluid is projected by the nozzle 22 and enters directly into the housing 15 following the deflection of the jet 24 by the deflector 32. The lubricating fluid then flows by gravity along the piston 8 and onto the walls of the housing 15, then falls back onto the boss 16 and into the lubricating fluid tank 2.

[0048] Compared to the mode shown in [Fig. 1], the direct lubrication of this lower part of the housing 15, in addition to that of the lower end of the piston 8, allows to bring more oil up into the housing 15 and to avoid the risk of seizure between the piston and the inner wall of the housing 15 during the translation of the piston 8 in the cylinder 10.

[0049] Alternatively, the deflector 32 is oriented so as to deflect the jet 24 in several directions.

[0050] The deflector 32 makes it possible, for example, to distribute the projected lubricating fluid equally between the shaft 18 and the pusher 14.

[0051] The nozzle 22 continuously sprays the lubricating fluid during the movement of the piston 8. In another embodiment, the lubricating fluid is sprayed only during part of the movement of the piston 8.

[0052] [Fig. 3] schematically represents a motor vehicle 34 comprising a thermal engine 1 comprising a system 3 for pressurizing a fluid as described previously.

Claims

Claims

1. A method of lubricating an interface (26) between a piston (8) of a pump (4) for compressing a fluid and a shaft (18) configured to drive the piston (8), characterized in that the method comprises projecting a jet (24) of a lubricating fluid directed towards the interface (26); and guiding the jet (24) of lubricant such that the jet (24) of lubricant is deflected by a deflector (30) formed in a casing (5) of the pump (4), the casing (5) housing the piston (8), and then flows over a portion of the piston (8).

2. A system (3) for pressurizing a fluid comprising a shaft (18), a pump (4) having a piston (8) for compressing a fluid, and a lubrication device (11), the shaft (18) being configured to drive the piston (8), characterized in that the lubrication device (11) comprises a nozzle (22) configured to project a jet (24) of a lubricating fluid directed towards an interface (26) between the piston (8) and the shaft (18), the pump (4) comprising a casing (5) housing the piston (8) and a deflector (32) formed in the casing (5) so that the jet (24) of lubricating fluid is deflected by the deflector (32) and flows over a portion of the piston (8).

3. System (3) according to claim 2, wherein the pump (4) comprises a high pressure fuel supply pump.

4. System (3) according to one of claims 2 and 3, in which the nozzle (22) comprises a calibrated orifice (28) controlling the flow rate of the lubricating fluid.

5. Lubricating fluid tank (2) for a thermal engine (1) of a motor vehicle (34) comprising a pressurization system (3) according to one of claims 2 to 4, the lubricating fluid tank (2) comprising a supply channel (30) supplying the nozzle (22).

6. A lubricating fluid tank (2) according to claim 5, wherein the nozzle (22) and the pump (4) are arranged in the lubricating fluid tank (2) such that the jet (24) of lubricating fluid falls back to the bottom of the lubricating fluid tank (2) under the effect of gravity.

7. Thermal engine (1) comprising a lubricating fluid tank (2) according to any one of claims 5 and 6.

8. Motor vehicle (34) comprising a thermal engine (1) according to claim 7.

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