Assembly comprising a heat engine with a cylinder head, cylinder-head cover, and tool for adjusting a camshaft

Abstract

The invention relates to an assembly comprising a heat engine equipped with a cylinder head (2) covered by a cylinder-head cover (4), which between them receive at least one camshaft having, on one side, a joining edge parallel to its axis, which is formed between two flat surfaces, and comprising a tool for adjusting the rotation of the camshaft, which tool fits into a bore in the cylinder-head cover, the adjustment tool comprising an attachment part (20) for attachment to the cylinder-head cover (4), and an independent rod comprising, at its end, a notch having two bearing faces which, in the fixed position of the tool, bear on the two surfaces of the camshaft on either side of the edge.

Description

[0001] DESCRIPTION

[0002] Title: ASSEMBLY COMPRISING A HEAT ENGINE WITH CYLINDER HEAD, CYLINDER HEAD COVER AND CAMSHAFT TIMING TOOL

[0003] 001. The present invention claims priority from French application No. 2308843 filed on 08 / 22 / 2023, the content of which (text, drawings and claims) is incorporated here by reference.

[0004] 002. The present invention relates to an assembly comprising a thermal engine equipped with a cylinder head covered by a cylinder head cover, and a tool for timing a camshaft of this cylinder head intended for maintenance operations on the engine, and relates to a method of installing the timing tool on the engine.

[0005] 003. Thermal engines have a cylinder head covering the cylinders, including intake and exhaust ducts equipped with valves to manage the inflow and outflow of gas flows into these cylinders. In the case of overhead camshafts, these shafts, arranged in the cylinder head, above the valve stems, act via their cams directly on the end of these stems in order to actuate the valves to manage their openings.

[0006] 004. In particular, it is known to provide a cylinder head comprising an upper joint plane receiving a cylinder head cover, the axes of the camshafts being arranged on this joint plane, which makes it possible to carry out machining for the shaft bearings in each of these parts forming a half-bearing.

[0007] 005. Camshafts are generally driven by a sprocket or pulley located at the end of each shaft, which receives a chain or a toothed belt respectively, which synchronizes the rotations. Some cylinder heads also have a phase shift system integrated into the sprocket or pulley, allowing the engine to operate optimally depending on the driving conditions.

[0008] 006. To carry out certain maintenance operations, in particular unscrewing the pulley or pinion at the end of a camshaft, in particular to change the timing belt, it may be necessary to set the angular position of the camshaft, and in certain cases a lock to apply a torque to this shaft along its axis.

[0009] 007. A known type of tool used for a camshaft timing operation, presented in particular by document US-A1-2006213045, comprises a straight rod inserted into a bore in the cylinder head cover above the camshaft, which descends along a flat formed on the side of this shaft, parallel to the axis, to finally fit into a bore in the cylinder head arranged just below this flat.

[0010] 008. After adjusting the angular position of the camshaft to a defined angle, an operator lowers the rod along the flat to insert its lower end into the bore of the cylinder head. With the flat positioned just above the bore receiving the lower end of the rod, this rod maintains an angular positioning of the flat, and forms a stop which can receive a force when a rotational torque is applied to the shaft.

[0011] 009. However, in some cases the cylinder head cover does not have a hole located above a flat part of the camshaft, which is accessible by a straight rod. In this case it is necessary to remove the cylinder head cover in order to directly access the camshafts located below, removal which may require the removal of injectors or a high pressure fuel pump fixed to this cylinder head cover.

[0012] 010. This operation of removing the cylinder head cover requires the replacement of its seal on the cylinder head during reassembly, and depending on the case, the seals of the injectors and the pump. There are then problems of risks of oil or fuel leaks in the event of a defect in these reassembly operations, and of high cost due to the replacement of the sealing parts and the significant labor time to carry out these operations.

[0013] 011. The present invention aims in particular to avoid these problems of the prior art.

[0014] 012. To this end, it proposes an assembly comprising a thermal engine equipped with a cylinder head covered by a cylinder head cover, receiving between the two at least one camshaft having on one side a junction edge parallel to its axis which is formed between two flat surfaces, and comprising a tool for timing the rotation of the camshaft which enters a bore in the cylinder head cover, this assembly being remarkable in that the timing tool comprises a fixing part on the cylinder head cover, and an independent rod comprising at its end a notch having two bearing faces which in the fixed position of the tool bear on the two surfaces of the camshaft on each side of the edge.

[0015] 013. An advantage of this assembly is that the rod is first introduced simply and quickly into the hole in the cylinder head cover, with freedom of inclination facilitating an approach to reach the edge of the shaft which can be offset from this hole. Then by tightening the fixing device, the rod is precisely positioned, placing its faces in contact with the two surfaces of the camshaft to form a precise setting of the rotational position of the shaft.

[0016] 014. In addition, the two supports on the surfaces on each side of the edge make it easy to resist torque in both directions, in particular to disassemble or reassemble a pinion or pulley at the end of the shaft by applying a rotational torque to the shaft.

[0017] 015. The system comprising a heat engine and a tool according to the invention may further comprise one or more of the following characteristics, which may be combined with each other.

[0018] 016. Advantageously, the two surfaces of the camshaft are perpendicular.

[0019] 017. In this case, advantageously the camshaft has two parallel surfaces, and a perpendicular surface which is closer to the axis than the parallel surfaces.

[0020] 018. Advantageously, each bearing face of the notch has a slightly curved shape with generators parallel to the axis of the camshaft.

[0021] 019. In particular, following the transverse direction the drilling of the cylinder head cover can in its extension open out next to the camshaft.

[0022] 020. In this case, advantageously the rod is curved, and has one end substantially perpendicular to the axis of the drilling.

[0023] 021. Advantageously, the rod is connected to a plate which, in the fixed position of the tool, is clamped between the fixing part and a joint plane of the cylinder head cover. 022. In this case, advantageously the lower face of the fixing part comprises a recess receiving the plate, these two parts having a bearing surface on the joint plane which are in the same plane.

[0024] 023. In addition, advantageously the assembly includes pins for positioning the plate relative to the fixing part.

[0025] 024. The invention also relates to a method for installing a timing tool for an assembly comprising any one of the preceding characteristics, remarkable in that it comprises a step of installing the camshaft in an angular intervention position, then a step of introducing the rod along a curved path in the bore which has been opened, to finish by adjusting the junction edge in the notch, then a step of tightening the rod by the fixing part.

[0026] 025. The invention will be better understood and other characteristics and advantages will appear more clearly on reading the description below given by way of example, with reference to the appended drawings in which:

[0027] 026. [Fig. 1] is a top view of a heat engine of an assembly according to the invention comprising the timing tool in position;

[0028] 027. [Fig. 2] is a detail view of the setting tool alone;

[0029] 028. [Fig. 3] is a cross-sectional view of the timing tool fixed on the cylinder head cover and resting on the camshaft; and

[0030] 029. [Fig. 4] is a diagram showing in cross-section the support of the tool faces on the surfaces of the camshaft.

[0031] 030. Throughout the document the upper or above direction relates to an engine having cylinders arranged along a vertical axis, the cylinder head being placed above on a horizontal joint plane. In the vehicle the engine can take any orientation.

[0032] 031. Figure 1 shows a cylinder head receiving above a cylinder head cover 4, with between the two at the joint plane two camshafts arranged in parallel, each comprising at one end a pulley 8 receiving a timing belt 10 driven by the engine crankshaft.

[0033] 032. Each pulley 8 comprising lateral flanges for retaining the belt 10, is connected to the camshaft by a hub 12 comprising a phase shift device allowing a modification of its angular position under the effect of a command to optimize the operation of the thermal engine.

[0034] 033. The cylinder head cover 4 has an upper joint plane 14 intended to receive an upper cover, which has been removed, closing an opening above the pulleys 8 in order to allow intervention on the belt 10, in particular to change it, and closing holes giving access above each camshaft.

[0035] 034. The presence of the flanges on each pulley 8, not allowing the belt 10 to slide on the side of the pulleys to remove it, requires the disassembly of these pulleys in order to change this belt. It is necessary to block each camshaft in rotation in order to apply a loosening or tightening torque to a screw fixed on the end of the shaft, with a resistant hold allowing this torque to be applied. In addition, the refitting of the belt 10 requires precise rotational positioning of the camshafts in order to maintain synchronization.

[0036] 035. A fixing plate 20 of a tool for setting the rotation of the exhaust camshaft, elongated in the transverse direction relative to the shafts, is fixed at its ends to the upper joint plane 14 by two screws 22 passing through holes 24 of this plate, then engaged in holes of the cylinder head cover 4 provided to receive the tightening screws of the upper cover.

[0037] 036. Figures 2 and 3 show the fixing plate 20 comprising below in the thickness a recess 26 receiving a plate 28 of a lower wedging part 30, in order to form a lower flat support face of this tool which is clamped on the upper joint plane 14 of the cylinder head cover 4.

[0038] 037. The plate of the wedging part 28 comprises two pins 32 protruding above which are engaged in two holes 34 of the fixing plate 20 to achieve positioning, and comprises a hole 36 receiving a screw 22 for tightening this plate.

[0039] 038. The plate of the timing part 28 comprises below a curved rod 38 having a substantially horizontal end which ends in a notch 40 formed by two perpendicular flat faces comprising a vertical face and a horizontal face which are positioned precisely. The curved rod 38 is engaged in a vertical bore 52 of the cylinder head cover 4, having a diameter slightly greater than that of this rod, which in the transverse direction opens out in its extension next to the camshaft 42.

[0040] 039. The camshaft 42 comprises at the level of the curved rod 38 a cross-section having in its angular setting position used for maintenance operations, a curved lower part 44 centered on the axis, two vertical parallel surfaces 46 and above a horizontal perpendicular surface 48.

[0041] 040. The horizontal surface 48 being closer to the axis than the vertical surfaces 46, two parallel edges 50 are obtained between these surfaces which, for a rotation of a quarter of a turn of the camshaft 42, have differentiated positions. In the intervention position, the two perpendicular faces of the notch 40 at the end of the curved rod 38 are supported on the horizontal surface 48 and the vertical face 46 arranged on the side of this rod, without the possibility of inversion with the other parallel edge 50 which could not come into this notch.

[0042] 041. The method of mounting the timing tool is as follows. In a first step, the engine crankshaft is arranged in an angular position placing the camshafts 42 in their intervention position. In particular, a bore in the cylinder head 2 at the end of a camshaft 42, comprising a mark, can be used to fix a tool for positioning and maintaining it in the angular intervention position.

[0043] 042. In a following step the curved rod 38 of the lower timing part of the tool 30 is introduced into the reduced diameter bore 52 of the cylinder head cover 4, following a curved path C which allows its end to be introduced vertically, then progressively following the descent to straighten this part to shift the notch 40 towards the edge of the camshaft 50.

[0044] 043. At the end of the descent along the curvature C, the plate of the wedging part 28 is obtained, resting on the upper joint plane of the cylinder head cover 14, and the notch 40 resting both on the horizontal face 48 and on the vertical face 46 which is turned towards the reduced drilling 52.

[0045] 044. The plate 20 is then placed on the upper joint plane of the cylinder head cover 14, then the two screws 22 are tightened while at the same time compressing the plate of the shimming part 28 which is thus positioned and firmly locked in position.

[0046] 045. Precise positioning and locking of the notch 40 in a position offset transversely relative to the reduced bore 52 of the cylinder head cover 4 is achieved by the two-piece setting tool comprising the movable lower part allowing movement along the curvature C, and the clamping plate 20 which is fixed only at the end of this movement. The operator can then safely carry out maintenance operations, including in particular the application of a torque for loosening or tightening screws on the camshaft 42.

[0047] 046. The assembly according to the invention makes it possible to use an existing bore 52 of the cylinder head cover 4 which, in the transverse direction, is offset relative to the camshaft 42, which makes it possible, without dismantling this cylinder head cover, to use a bore which does not come directly onto the edge of this shaft. 047. Figure 4 shows the bearing faces of the notch 40, each comprising a slightly curved shape having generatrices parallel to the axis of the camshaft 42, so as to form on each face substantially a bearing line giving a more precise pressure surface which promotes the transmission of a significant force blocking rotation.

Claims

CLAIMS 1. Assembly comprising a thermal engine equipped with a cylinder head (2) covered by a cylinder head cover (4), receiving between the two at least one camshaft (42) having on one side a junction edge (50) parallel to its axis which is formed between two flat surfaces (46, 48), and comprising a tool for timing the rotation of the camshaft (42) which enters a bore in the cylinder head cover (52), characterized in that the timing tool comprises a fixing part (20) on the cylinder head cover (4), and an independent rod (38) comprising at its end a notch (40) having two bearing faces which in the fixed position of the tool are in abutment on the two surfaces of the camshaft (46, 48) on each side of the edge (50).

2. Assembly according to claim 1, characterized in that the two surfaces of the camshaft (46, 48) are perpendicular.

3. Assembly according to claim 2, characterized in that the camshaft (42) comprises two parallel surfaces (46), and a perpendicular surface (48) which is closer to the axis than the parallel surfaces.

4. Assembly according to any one of the preceding claims, characterized in that each bearing face of the notch (40) has a slightly curved shape having generatrices parallel to the axis of the camshaft (42).

5. Assembly according to any one of the preceding claims, characterized in that in the transverse direction the drilling of the cylinder head cover (52) in its extension opens next to the camshaft (42).

6. Assembly according to claim 5, characterized in that the rod (38) is curved, and has one end substantially perpendicular to the axis of the bore (52).

7. Assembly according to any one of the preceding claims, characterized in that the rod (38) is connected to a plate (28) which in the fixed position of the tool is clamped between the fixing part (20) and a joint plane of the cylinder head cover (14).

8. Assembly according to claim 7, characterized in that the lower face of the fixing part (20) comprises a recess (26) receiving the plate (28), these two parts having a bearing surface on the joint plane (14) which are in the same plane.

9. Assembly according to claim 8, characterized in that it comprises pins (32) for positioning the plate (28) relative to the fixing part (20).

10. Method for installing a tool for setting an assembly according to any one of the preceding claims, characterized in that it comprises a step of installing the camshaft (42) in an angular intervention position, then a step of introducing the rod (38) along a curved path (C) in the bore (52) which has been opened, to finish by adjusting the junction edge (50) in the notch (40), then a step of tightening the rod (38) by the fixing part (20).

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