AUTOMOBILE INTERNAL COMBUSTION ENGINE WITH CAMSHAFT-DRIVED HIGH-PRESSURE FUEL PUMP

Abstract

Internal combustion engine of a motor vehicle equipped with a fuel injection system, comprising a camshaft (6) disposed in a closed volume of a cylinder head (2) having a channel (20) supplied with pressurized oil for the lubrication of this camshaft (6), and comprising a high-pressure fuel pump including a cylindrical roller (12) fixed to the end of a sliding pump tappet (14), which bears against a pump cam (10) of the camshaft (6), the cylinder head (2) having an oil jet (30) connected to the lubrication channel (20), which has a calibrated flow control bore (38) directed towards the pump cam (12). Figure 1

Description

Title of the invention: AUTOMOBILE INTERNAL COMBUSTION ENGINE WITH CAMSHAFT-DRIVED HIGH-PRESSURE FUEL PUMP

[0001] The present invention relates to a motor vehicle internal combustion engine having a fuel injection system comprising a high-pressure pump driven by a camshaft, as well as to a motor vehicle equipped with such an internal combustion engine.

[0002] Some internal combustion engines include a fuel injection system comprising injectors continuously supplied by a high-pressure fuel reserve, having an electrical opening control giving a precise injection duration as well as a very fine spray which optimizes performance and pollutant emissions.

[0003] A known type of high-pressure fuel injection pump, presented in particular by document WO-A1-2018108350, comprises a pusher sliding perpendicularly to a camshaft driven in rotation in the cylinder head of the engine, comprising at its end a cylindrical roller disposed parallel to the camshaft which is permanently pressed against a cam of this shaft.

[0004] The sliding motion of the pump pusher, via the roller rolling on the pump cam, varies with each revolution the volume of a chamber receiving fuel through an inlet valve and expelling it through an outlet valve, thus ensuring a constant supply of fuel to the reservoir at high pressure. Depending on the operating conditions, the force exerted by the cam on the roller can be significant to achieve this pressure.

[0005] Generally, the upper volume of the cylinder head containing the camshaft has a low-pressure oil inlet delivered by the engine's lubrication pump, which generates droplets or a mist dispersed throughout this volume in order to lubricate the various moving components inside, including the rotation of the camshaft, the sliding of the distribution cams on sliding tappets or rocker arms, transmitting the lifting forces on the valves, and the sliding of the tappets or the rocker arms, and the sliding of the valve stems.

[0006] The cam actuating the roller of the high-pressure pump also receives the oil mist, like the other cams, to lubricate and cool the contacting surfaces. However, in certain operating conditions, high pressures may occur on the contact surface between the cylindrical roller and the cam, which limit to a straight segment of small width forming a very limited surface, while the lubrication of this contact is at this moment insufficient.

[0007] In this case, surface deterioration problems can occur, including overheating, pitting of surfaces and wear, which can lead to defective operation and even failure.

[0008] The present invention is specifically intended to avoid these problems of the prior art.

[0009] To this end, it proposes a motor vehicle internal combustion engine equipped with a fuel injection system, comprising a camshaft disposed in a closed volume of a cylinder head having a channel supplied with pressurized oil for the lubrication of this camshaft, and comprising a high-pressure fuel pump comprising a cylindrical roller fixed to the end of a sliding pump tappet, which bears against a pump cam of the camshaft, this internal combustion engine being notable in that the cylinder head has an oil jet connected to the lubrication channel, which has a calibrated bore for controlling the flow directed towards the pump cam.

[0010] One advantage of this thermal engine is that by dedicating an injector to form a jet of oil under pressure specifically directed on the pump cam, a particular oil flow on this cam is obtained thanks to its calibrated drilling which is constantly ensured, guaranteeing an oil film in contact with the roller and cooling of the surfaces.

[0011] In addition, the calibrated drilling of the injector allows the consumption of just the necessary flow, while maintaining upstream a pressure which allows for a jet of oil to be directed precisely onto the surfaces to be treated, without loss elsewhere, and while retaining the remaining flow necessary for the engine's operation.

[0012] By using the existing engine oil circuit, with only the economical addition of a nozzle, reliable lubrication of the pump cam and its roller is achieved under the most demanding operating conditions. Lubrication is ensured in all cases, for example, during a cold start of the vehicle with a closed cylinder head that has not yet developed an oil mist, or during high rotational speeds at high temperatures, resulting in greater heating of the contacting surfaces.

[0013] The heat engine according to the invention may further comprise one or more of the following characteristics which may be combined with each other.

[0014] Advantageously, the calibrated drilling is carried out over the entire length of the oil jet.

[0015] In this case, the calibrated drilling may include, along the length of the oil jet, a portion with a local reduction in cross-section.

[0016] Advantageously, the oil jet has a screw thread in the cylinder head.

[0017] In this case, advantageously the oil jet comprises a head resting on a plane of the cylinder head, including an outer contour allowing a grip by a screwing tool.

[0018] In particular, the oil jet can form a jet that is directed upwards.

[0019] Advantageously, the lubrication channel supplies each of the camshaft bearings.

[0020] The invention also relates to a motor vehicle comprising a heat engine having any one of the preceding characteristics.

[0021] The invention will be better understood and other features and advantages will become more apparent upon reading the following description given by way of example, with reference to the accompanying drawings in which:

[0022] [Fig. 1] is a diagram of the closed volume of the cylinder head of a heat engine according to the invention, showing a side view of the camshaft; and

[0023] [Fig.2] is a diagram of this volume presented in axial section.

[0024] Throughout the document the upper or top direction is relative to a vehicle placed on a horizontal surface.

[0025] Figures 1 and 2 show a cylinder head 2 placed on the upper horizontal plane of an engine block closing the cylinders, receiving above in a closed volume a camshaft support 4 containing bearings 26 receiving a camshaft 6 arranged parallel to the plane of the engine block.

[0026] The camshaft 6 has a series of cams 8 each actuating a pusher which acts on the end of a valve to achieve the intake or exhaust of the cylinder located below.

[0027] One end of the camshaft 6 has a pump cam 10 with three bosses for a three-cylinder engine, receiving the support of a cylindrical roller 12 having an axis A parallel to that of the camshaft, which is fixed to the base of a pump tappet 14 having an axis perpendicular to the axis A, sliding in a camshaft support 4 having a tappet housing 16. The pump, continuously driven with the rotation of the engine, maintains a high pressure in the reservoir which supplies the fuel injectors.

[0028] The cylinder head 2 has a horizontal supply channel 20 receiving oil pressure from the engine crankcase, to distribute it through a series of vertical holes 22 opening into an aligned hole 24 in the camshaft support 4, which supplies each camshaft bearing 26 to ensure its lubrication.

[0029] An oil jet 30 comprises a threaded part 32 screwed onto the top of the cylinder head 2, in a complementary bore of the cylinder head 34 opening into the horizontal channel 20, and a head 36 bearing on the upper surface of this cylinder head, comprising an outer contour allowing a grip by a screwing tool.

[0030] The oil jet 30 has along its entire length an axial bore 38 having a calibrated diameter for limiting the oil flow, allowing both to maintain upstream pressure to ensure the pressure necessary for the lubrication of the whole engine, and with this pressure to form along its axis a concentrated or divergent jet 40 which is directed onto the pump roller 12.

[0031] Alternatively, the calibrated bore 38 may include, along the length of the oil jet 30, a part with a local reduction in cross-section.

[0032] This is obtained in all cases of engine operation, in particular when the closed volume above the cylinder head does not have sufficient oil projection or mist to ensure the lubrication and cooling of the cam 10 and the pump roller 12 bearing on it.

[0033] The jet 30 and its complementary bore 34 can be easily added at limited cost to a cylinder head 2 having a supply channel arranged along the length of the camshaft 6 in order to supply all of its bearings 26, passing close to the pump cam 10, which represents a limited cost.

Claims

Demands

1. Internal combustion engine of a motor vehicle equipped with a fuel injection system, comprising a camshaft (6) disposed in a closed volume of a cylinder head (2) having a channel (20) supplied with pressurized oil for the lubrication of this camshaft (6), and comprising a high-pressure fuel pump comprising a cylindrical roller (12) fixed to the end of a sliding pump tappet (14), which bears against a pump cam (10) of the camshaft (6), characterized in that the cylinder head (2) has an oil jet (30) connected to the lubrication channel (20), which has a calibrated flow control bore (38) directed towards the pump cam (12).

2. Heat engine according to claim 1, characterized in that the calibrated bore (38) is made over the full length of the oil jet (30).

3. Heat engine according to claim 2, characterized in that the calibrated bore (38) has along the length of the oil jet (30) a part with a local reduction in cross-section.

4. Internal combustion engine according to any one of the preceding claims, characterized in that the oil jet (30) has a thread for screwing into the cylinder head (2).

5. Heat engine according to claim 4, characterized in that the oil jet (30) has a head (36) bearing on a plane of the cylinder head (2), comprising an outer contour allowing a grip by a screwing tool.

6. Heat engine according to any one of the preceding claims, characterized in that the oil jet (30) forms a jet (40) which is directed upwards.

7. Heat engine according to any one of the preceding claims, characterized in that the lubrication channel (20) supplies each of the bearings (26) of the camshaft (6).

8. Motor vehicle comprising a heat engine, characterized in that this heat engine is according to any one of the preceding claims.