EP0469334A1 - Method for changing the angular position of shafts for an internal combustion engine - Google Patents

Abstract

A camshaft (1) which can be rotated relative to a shaft driving it has a phase converter (2) with a piston (12) which is hydraulically loaded on both sides. The sprocket (7) driving the camshaft has external teeth (11). A toothing (16) connected to the camshaft via a hollow shaft (17) is designed as an internal toothing. Corresponding toothings (13, 14) of the piston engage in both toothings. An axial recess (60) is arranged in the camshaft, in which an inserted tube (61) separates two spaces (62, 64) from one another. A switching valve (46) fed from the oil circuit supplies the piston with pressure oil in one position via one of the spaces, so that it is displaced axially into a first end position and the camshaft rotates in the process. In a second position, the piston is pushed axially back over the second space by means of pressure oil. The device takes up little space and is simply constructed. <IMAGE>

Description

The invention relates to a device according to the preamble of claim 1.

It is known to adapt the valve timing of an internal combustion engine to its speed in order to be able to operate it optimally in the widest possible speed range. This can improve torque, power, exhaust emissions, idling behavior and fuel consumption.

One possibility of changing the valve timing during the operation of the internal combustion engine is to preferably rotate the position of the intake camshaft in relation to the crankshaft driving it with the aid of a so-called phase converter. Depending on the oil pressure, a coupling member is axially displaced, which is coaxially surrounded by the wheel driving the camshaft. The coupling member carries two toothings, at least one of which is helically toothed, each of which interacts with a corresponding toothing on the camshaft or in the wheel, e.g. known from EP-0 335 083.

Phase shifters are known, e.g. from EP 0 356 162 or the already mentioned EP 0 335 083, in which the wheel driving the camshaft has an internal toothing which engages in an external toothing which is assigned to the coupling member acting as a hydraulically actuated piston. The piston carries a second toothing, which is designed as an internal toothing and which engages in a corresponding external toothing of the camshaft. Phase converters are also known, e.g. from EP 0 245 791, in which the coupling member moved by a hydraulic piston or an electromagnet carries two axially offset external toothings, one of which engages in an internal toothing of the camshaft, while the other engages in an internal toothing of the driving wheel.

All of the devices mentioned have the disadvantage that they take up a considerable amount of additional installation space, which increases the installation length of an internal combustion engine equipped with such a device. Usually, a plane delimits a front end of the internal combustion engine, which is formed by the endless drive running over the wheel driving the camshaft. In the known prior art, this conclusion is either clearly surmounted by the device, or the wheel had to be arranged further away from the end face of the internal combustion engine due to the structural volume of the device.

The invention is therefore based on the object of avoiding the abovementioned disadvantages and thus creating a compact device for changing the relative rotational position of shafts in an internal combustion engine, which takes up little space and at the same time leaves the overall length of an internal combustion engine equipped with the device as short as possible .

This object is achieved with the features specified in claim 1. Advantageous embodiments, which also include a compact hydraulic control of the device, are named in the subclaims.

This device enables a compact construction of the phase converter and a simple design of the drive end of the camshaft. The compact structure is achieved by such an arrangement of the two pairs of teeth common in a generic phase converter that the wheel driving the camshaft has a first external toothing and that a second toothing connected to the camshaft is designed as an internal toothing, with corresponding toothing in these two toothings engage the coupling member designed as a piston. The gears are all substantially coaxially enclosed by the wheel, so that no additional space extending in the axial direction is required.

The second toothing is advantageously not formed directly in the camshaft, but in a hollow shaft detachably connected to the camshaft, which at the same time delimits a space from the camshaft in which the piston can be axially displaced into its end positions.

The problem of axially securing the wheel is advantageously solved in that the wheel is axially fixed to the hollow shaft without the necessary rotational movement between the wheel and the hollow shaft being hindered when the phase converter is actuated. The wheel can be designed as a sprocket or pulley and can be secured with a spring ring acting between the hollow shaft and the wheel or can be screwed to the hollow shaft in such a way that the screws pass through elongated holes arranged in the wheel by means of guide sleeves.

The simple design of the drive-side end of the camshaft, which only utilizes the available space, is achieved by removing the shut-off device controlling the supply and removal of oil from the phase converter or the camshaft. The shut-off device can be located at any point on the internal combustion engine, e.g. be arranged in the cylinder head and is also operated hydraulically.

A tube is held in an easy to manufacture, stepped, axially extending recess of the camshaft, which separates two spaces from one another, which, depending on the position of the shut-off element, enable the supply or discharge of oil into the camshaft or the phase converter. The rooms are connected to radial bores of the camshaft, which in turn cooperate with lines which open into annular spaces of the shut-off element designed as a changeover valve.

The radial bores can be arranged at any point on the camshaft.

The phase converter protrudes only slightly from the drive end of the camshaft and can be assembled as a complete unit. If a phase converter is not to be installed, the camshaft can still be used by attaching a modified sprocket.

The camshaft, which is usually made of a hard material, does not require any teeth or thread.

The device requires only a small amount of oil, since only the oil displaced from the chambers adjoining the pistons has to be renewed for moving the piston from a first to a second end position.

The emptying of the chambers after the internal combustion engine has been switched off is avoided in that oil-carrying lines are designed as risers which prevent oil from flowing back. The actuation circuit for the device is part of the oil circuit of the internal combustion engine. The lubrication circuit for the camshafts is connected to this actuation circuit in such a way that the lubrication is retained in the event of a failure of the phase converter or the shut-off device.

The device is still quiet when the internal combustion engine is operating, since there is no mechanical connection between the device and a hood covering it, e.g. there are centered components of the device in this hood.

• Fig.1 einen Querschnitt durch eine erste Ausführungsform,
• Fig.1 a die erste Ausführungsform mit einer modifizierten Nockenwelle,
• Fig.2 einen Querschnitt durch eine zweite Ausführungsform,
• Fig.2a die zweite Ausführungsform mit einer modifizierten Nockenwelle,
• Fig.3 schematisch einen Ölkreislauf der Vorrichtung mit einem Absperrorgan in einer ersten Stellung,
• Fig.4 schematisch einen Ölkreislauf der Vorrichtung mit einem Absperrorgan in einer zweiten Stellung,
• Fig.5 die Nockenwelle einer dritten Ausführungsform,
• Fig.6 einen Querschnitt durch einen Zylinderkopf einer Brennkraftmaschine mit der dritten Ausführungsform,
• Fig.7 einen Schnitt entlang der Linie VII - VII gemäß Fig.6 und
• Fig.8 eine Ansicht aus Richtung des Pfeiles X gemäß Fig.2.

The device is explained in more detail by way of example with reference to figures below. Show it:

• 1 shows a cross section through a first embodiment,
• 1a the first embodiment with a modified camshaft,
• 2 shows a cross section through a second embodiment,
• 2a shows the second embodiment with a modified camshaft,
• 3 schematically shows an oil circuit of the device with a shut-off element in a first position,
• 4 schematically shows an oil circuit of the device with a shut-off element in a second position,
• 5 shows the camshaft of a third embodiment,
• 6 shows a cross section through a cylinder head of an internal combustion engine with the third embodiment,
• 7 shows a section along the line VII - VII according to FIG. 6 and
• 8 shows a view from the direction of arrow X according to FIG.

In an internal combustion engine (not shown in detail) with four overhead camshafts arranged in a motor vehicle, a phase converter 2 at the drive-side end 3 is assigned to each of the two camshafts 1 serving as the inlet. Each camshaft 1 is held in a plurality of bearings 4 which are connected to a lubrication circuit 5. The oil circuit of the internal combustion engine comprises the lubrication circuit 5, an actuation circuit for adjusting the phase converter 2 and a lubrication circuit of a crankshaft 6, which is only indicated.

The phase converter 2 is essentially made up of the three commonly used elements which are in engagement with one another via toothings. On the one hand, from a wheel 8, which serves to drive the camshaft 1 and is designed as a chain wheel 7, into which an inner hub 9, which carries a first, oblique toothing 11 designed as first outer toothing 11, is welded. The wheel 8 is connected via the first toothing 11 to a coupling member designed as a hydraulically loaded piston 12 on both sides via a corresponding, first oblique inner toothing 13 which is axially displaceable in two end positions E1, E2 with respect to the axis N running longitudinally and centrally in the camshaft 1 is. The piston 12 carries a second, oblique external toothing 14 which engages in a corresponding toothing 16 of a hollow shaft 17 which is designed as a second internal toothing 16 and which is connected to a flange 18 of the camshaft 1. A cap 19 is pressed into the inner hub 9.

The piston 12 divides a space 20 enclosed between the flange 18 and the hollow shaft 17 into a first chamber 21 and a second chamber 22.

In Fig. 1 and Fig. 2, the piston 12 is in a first end position E1, which is in a first operating state, e.g. idling.

In the first embodiment according to FIGS. 1 and 1, the chain wheel 7 is axially fixed on the hollow shaft 17 by means of a prestressed spring ring 23. It lies half in a groove 24 of the chain wheel 7 and the other half in a recess 25 of the hollow shaft 17, the depth of which is at least twice as great as that of the groove 24.

The spring ring 23 is accessible via a plurality of mounting openings 26.

If the wheel 8 is designed as a pulley, 18 sealing rings are inserted adjacent the spring ring 23 and between the hollow shaft 17 and the flange.

During assembly, the spring ring 23 is placed in the recess 25 into which it is half immersed due to its pretension. Subsequently the sprocket 7 is pushed onto the hollow shaft 17, an integrally formed bevel 27 presses the spring ring 23 completely into the recess 25 before it lies halfway in this groove 24 when the recess 25 and groove 24 overlap. The spring ring 23 can be circular or rectangular in cross section.

In a second embodiment of the device according to FIGS. 2 and 2a, the chain wheel 7 is axially secured to the hollow shaft 17 by means of screws 28. These screws 28 are screwed into the thread of the hollow shaft 17 and are slidably guided in the slots 30 of the chain wheel 7 by means of guide sleeves 29. A small axial play A remains between the guide sleeve 29 and the wheel 8.

The phase converter 2 is held in both embodiments with screw connections 31 in slots 32 of the hollow shaft 17 with sleeve nuts 33 against rotation. The elongated holes 32 allow the phase converter 2 to be installed in the correct position, regardless of the position of the camshaft 1 secured against rotation for the installation.

The phase converter 2 can be completely preassembled before mounting on the camshaft 1. A pin is inserted into a fitting bore 34 that penetrates the sprocket 7 and the hollow shaft 17 and secures the two parts against rotation. The sprocket 7 is then axially fixed to the hollow shaft 17 with a spring ring 23 or the screws 28 and the guide sleeves 29 as already described. After the cap 19 has been pressed in and the piston 12 has been pushed into the toothings 11 and 16, the phase converter 2 is fastened to the flange 18 as a complete unit; the piston 12 is pushed onto a radial flange 35 of the camshaft.

The oil circuit of the internal combustion engine has a pump 40 which conveys oil from a reservoir 41 through a filter 42. From there, a branch 43 leads to a switching valve 44, to the crankshaft 6 of the internal combustion engine and, via an oil-supplying channel 45, to a changeover valve 46 arranged parallel to this channel 45 and to a downstream pressure reducing valve 47.

A pressure limiting valve 48 is connected between the filter 42 and the crankshaft 6 and limits the oil pressure supplied by the pump 40 to a maximum pressure PM.

From the pressure reducing valve 47 branches off the lubrication circuit 5, which pressurizes the bearings 4 with a pressure P1, which is preferably less than the pressure PM.

The changeover valve 46 has integrated check valves 49, via which the channel 45 can be coupled to the phase converters 2. A first and a second line 50 and 51 each lead from the changeover valve 46 to a separate bearing 52 of the camshafts 1. A connection is made via ring channels 53 running in these bearings 52 to first and second bores 54 and 55 running radially in the camshafts 1.

In the camshaft 1 shown above the axis N, a cylindrical, stepped recess 60, which extends from the end 3 in a rotationally symmetrical manner to the axis N, is introduced. It has a first diameter D1 from the end 3 to immediately behind the first bore 54, then a second, smaller diameter D2 between the bores 54, 55 and from there to an immediately smaller diameter D3 until immediately behind the second bore 55. A tube 61 is held in the recess 60 as a cylindrical body, which is widened radially at the end 3 to the diameter D1 and, moreover, has the diameter D2. The tube 61 thus separates an annular outer space 62 within the recess 60, into which the first bore 54 opens and which is connected to the first chamber 21 at the end 3 via an almost radially extending connecting bore 63.

The second bore 55 cuts the recess 60 in the area of the diameter D3 and is connected to an interior 64 running inside the tube 61.

In a modification shown in FIG. 1, a built, hollow camshaft 1 is shown, into which a bushing 65 is inserted. The tube 61 is held at the end 3 in a clamping ring 66 and in the bush 65. The flange 18 is formed in one piece with the radial flange 35 and pushed separately onto the camshaft 1. The second bore 55 runs partially in the bush 65 and is in turn connected to the interior 64. The outer space 62 formed between the tube 61 and the recess 60 connects the first bore 54 to the first chamber 21.

The modification shown in FIG. 2a is identical to FIG.la with regard to the mounting of the tube 61 in the bush 65, but the flange 18 is inserted in one piece with a sleeve 67 into the built-in camshaft 1.

When the internal combustion engine is operating, the pump 40 pumps oil from the reservoir 41 through the filter 42 to the branch 43. The switching valve 44 is switched on or off by an electronic control unit 70 depending on the input signals load and speed of the internal combustion engine.

In the switched-off state, no oil gets from the branch 43 via the switching valve 44 to the switching valve 46. This is spring-loaded in a first position S1, which corresponds to the end position E1 of the piston 12. That with Oil through the channel 45 along the arrows shown opens the check valves 49, so that the oil flows through first annular spaces 71 into the first lines 50 and from there into the first bores 54. The pressure acts from the bore 54 through the outer space 62 and the connecting bore 63 on the first chamber 21 and holds the piston 12 in its first end position E1 (FIG. 3).

In a second operating state of the internal combustion engine, e.g. a medium speed range, the control unit 70 switches the switching valve 44 on, so that oil flows from the branch 43 via the switching valve 44 to the switching valve 46 and shifts it into a second position S2, which corresponds to the end position E2 of the piston 12. The oil flowing into the second annular spaces 72 via the check valves 49 now reaches the second bores 55 via the second lines 51. From there, the pressure acts on the second chamber 22 through the interior 64. The oil flows out of the open end of the tube 61 into a cavity 73 formed by the radial flange 35 and the cap 19 and from there via openings 74 in the piston 12 into the second chamber 22. This piston 12 is axially displaced into the second end position E2, with the oblique toothings 11, 13 and 14, 16 the sprocket 7 is rotated relative to the camshaft 1. Rotational displacements occur in the phase converters 2 between the components bordering on sliding surfaces F.

The oil volume displaced from the first chamber 21 during the displacement from the end position E1 to the end position E2 flows through the connecting bore 63, the outer space 62 and the first bore 54 into the annular channel 53 and from there via the first line 50.

In both end positions E1, E2 of the changeover valve 46, the annular spaces 71, 72 receiving oil flowing back from the phase converters 2 are connected to risers 75 which open geodetically above the phase converters 2 in the internal combustion engine, so that after the internal combustion engine has been switched off, the actuation circuit is prevented from being emptied is.

When the piston 12 is moved from the end position E2 to the end position E1, the oil displaced from the second chamber 22 flows through the openings 74, the cavity 73, the interior 64 and the second bore 55 into the annular channel 53 and from there via the second Line 51 into the changeover valve 46.

When the engine is operating at low speeds, the pump 40 does not deliver a maximum pressure PM. If it is nevertheless necessary to move the piston 12, the check valves 49 cause the annular spaces 71, 72 to be filled in batches. As a result, the piston 12 is shifted in stages from one end position to the other.

Instead of the switching valve 46 responsible for two camshafts 1, the two camshafts 1 can each be assigned their own actuation circuit. Each camshaft 1 is assigned a channel 45, a changeover valve 46 with a check valve 49 and a pressure reducing valve 47.

In a third embodiment of the invention according to FIG. 5, no separate bearing point 52 is required to ensure the supply and discharge of oil into the camshaft 1. The radial first and second bores 54, 55 are arranged at locations on the camshaft 1 which are supported in the bearings 4.

The bearings 4 are each designed as an upper and lower half 4a, 4b in an upper part 80 and a lower part 81 of a bearing frame 82 for camshafts. Channels 83, 84 run in the upper part 80 as part of the lubrication circuit 5. From the channel 83 located downstream of the pressure reducing valve 47 and running parallel to the axis N in the upper part 80, channels 84 branch off at right angles in a transverse plane Q to each bearing 4. Bores 85 receive screw connections 86 for fastening the upper part 80 to the lower part 81. The channels 84 are guided in a ring around the bores 85 lying between the axis N and the channel 83, so that the oil with the pressure P1 adjacent to the transverse plane Q supplies the bearing 4 in its upper half 4a via two lubrication openings 87.

The supply of outer space 62 and inner space 64 takes place in an analogous manner to the first two embodiments of the invention, but the line 50 leading to the first bore 54 is arranged in a first bearing 4 and the line 51 leading to the second bore 55 is arranged in a second, adjacent to the first bearing 4. The lower halves 4b each have a groove 88, which is arranged symmetrically to the transverse plane Q between the lubrication openings 87 according to FIG. 7. The first line 50 opens into this groove 88, the second line 51 into the groove 88 of a second bearing 4.

According to FIG. 6, the bearing frame 82 is fastened on the side of a cylinder head 89 facing away from the combustion chambers, in which part of the lines 50, 51 of the actuation circuit are arranged.

The embodiment of the embodiment described above separates the parts of the lubrication circuit 5 and the actuation circuit arranged in a bearing 4 and thus also the different oil pressures P1, PM. Also in this embodiment, the camshaft 1 in the modified form according to Figures 1 and 2a can be used. The length of the bush 65 is carried out in accordance with the distance between two adjacent bearings 4.

Claims (21)

1. Device for the automatically controlled change in the relative rotational position of two shafts in an internal combustion engine, with at least one camshaft that can be rotated relative to a shaft that drives it (crankshaft) as a function of parameters of the internal combustion engine, and having a wheel which drives the camshaft and carries a first toothing, which acts on a second toothing connected to the camshaft via a coupling element which is acted upon by an oil circuit and which can be displaced axially at least in two end positions, characterized in that the first toothing (11) as first external toothing (11) is formed, which interacts with a corresponding first internal toothing (13) of the coupling member (piston 12), and that the second toothing (16) is designed as a second internal toothing (16) which interacts with a corresponding second external toothing (14) of the coupling member (piston 12). 2. Device according to claim 1, characterized in that the second toothing (16) is arranged in a hollow shaft (17) which is detachably connected to the camshaft (1). 3. Apparatus according to claim 2, characterized in that the hollow shaft (17) axially by means of screw connections (31) is secured against rotation on the camshaft (1) and these connections (31) in the hollow shaft (17) pass through elongated holes (32) . 4. The device according to claim 2, characterized in that the piston (12) divides a space (20) into two chambers (21, 22) which is formed between the camshaft (1) and the hollow shaft (17). 5. The device according to claim 2, characterized in that the wheel (8) is held axially on the hollow shaft (17). 6. The device according to claim 5, characterized in that the wheel (8) is held axially by means of a radially preloaded spring ring (23) on the hollow shaft (17). 7. The device according to claim 6, characterized in that the spring ring (23) in each case in a groove (24) of the wheel (8) and in a recess (25) of the hollow shaft (17) is arranged. 8. The device according to claim 4, characterized in that the wheel (8) is fixed axially by means of screws (28) on the hollow shaft (17), these screws (28) by means of guide sleeves (29) in the wheel (8) arranged elongated holes Push through (30). 9. The device according to claim 8, characterized in that a small axial clearance (A) remains between the guide sleeves (29) and the wheel (8). 10. The device according to one or more of the preceding claims, with an axial recess arranged in the end of the camshaft adjacent to the hollow shaft, which is connected to the oil circuit, and with a shut-off element which controls the filling and emptying of the chambers with oil,
characterized in that a cylindrical body (tube 61) arranged in the recess (60) separates an annular outer space (62) which, in a first position (S1) of the shut-off element (changeover valve 46), fills the first chamber (21) with a first bore (54) of the camshaft (1) connected to the oil circuit. 11. The device according to claim 10, characterized in that in a second position (S2) of the switching valve (46), the first chamber (21) is connected to the first bore (54) for emptying. 12. The apparatus according to claim 11, characterized in that in the first and in the second position (S1 and S2), the second chamber (22) by means of a by the tube (61) enclosed interior (64) with a second to the oil circuit connected bore (55) of the camshaft (1) is connected. 13. The apparatus according to claim 12, characterized in that the switching valve (46) is arranged parallel to an oil-supplying channel (45) of the oil circuit and has annular spaces (71, 72) which in the first and second position (S1 and S2 ) with first or second lines (50 or 51) connected to the first or second bore (54 or 55) are. 14. The apparatus according to claim 13, characterized in that between the channel (45) and the annular spaces (71, 72) check valves (49) are arranged. 15. The device according to one or more of the preceding claims, characterized in that the channel (45) downstream of the changeover valve (46) opens into a pressure reducing valve (47) which via a lubrication circuit (5) with bearings (4) of the camshaft (1 ) connected is. 16. The device according to one or more of the preceding claims, characterized in that the channel (45) upstream of the switching valve (46) has a branch (43) which with a pump (40), the switching valve (46), a switching valve ( 44) and the lubrication circuit of the crankshaft (6) of the internal combustion engine. 17. The device according to one or more of the preceding claims, characterized in that the switching valve (44) in dependence on input signals of a control device (70), the switching valve (46) from one position (S1 or S2) to the other position (S2 or S1) moves. 18. The device according to one or more of the preceding claims, with at least 2 camshafts, characterized in that each camshaft is assigned a changeover valve (46) with a check valve (49) and a channel (45) with a pressure reducing valve (47). 19. The apparatus according to claim 12, characterized in that the recess (60) from the end (3) along an axis (N) to behind the first bore (54) a first diameter (D1), between the bores (54, 55) has a smaller, second diameter (D2) and from there to behind the second bore (55) has an even smaller, third diameter (D3). 20. The apparatus according to claim 12, characterized in that the first and second bores (54 and 55) are arranged within a separate bearing point (52) of the camshaft (1). 21. The apparatus according to claim 12, characterized in that the first bore (54) opens into a groove (88) of a first bearing (4) of the camshaft (1) and that the second bore (55) into a groove (88) one second, adjacent to the first camp (4) opens.

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