WO2018046087A1

WO2018046087A1 - Camshaft adjustment apparatus and method

Info

Publication number: WO2018046087A1
Application number: PCT/EP2016/071200
Authority: WO
Inventors: Hagen MÜLLER; Theodor Hüser
Original assignee: HELLA GmbH & Co. KGaA
Priority date: 2016-09-08
Filing date: 2016-09-08
Publication date: 2018-03-15

Abstract

An apparatus (1) for camshaft timing adjustment, comprising at least a drive disc (10) and a hub (50) having a common rotational axis (2), wherein the drive disc (10) comprises at least one fluid chamber (20) accommodating a vane (60), wherein the vane (60) is attached to the hub (50) and separates the fluid chamber (20) into a first sub-chamber (21) and a second sub-chamber (22), has a reduced weight and is simple to manufacture, if the drive disc (10) comprises a ring segment shaped fluid channel (15) connecting a first sub-chamber (21) and a second sub-chamber (22) thereby enabling a fluid communication between the connected first and second sub-chambers (21), the fluid channel (15) being centered around the rotational axis (2) and if the apparatus (2) comprises a rotor (80) having a protrusion (90), the rotor (80) being driven to rotate around the rotational axis (2) while engaging with its protrusion the fluid channel (15) during rotation.

Description

Camshaft Adjustment Apparatus and Method

Field of the invention

The invention relates to an apparatus for camshaft adjustment of a combustion engine. The apparatus comprises at least a drive disc and a hub having a com- mon rotational axis, wherein the drive disc comprises at least one fluid chamber accommodating a vane. The vane is attached to the hub and separates the fluid chamber into a first sub-chamber and a second sub-chamber. By providing a fluid flow from one sub-chamber into another, the vane can be swiveled or pivoted and thus the angular position of the hub relative to the drive disc can be adjust- ed.

Description of the related art

Most combustion engines require a cam shaft for opening and closing the intake valves and outtake valves. The cam shaft is typically driven by the crank shaft via some sort of transmission, mostly by a chain drive or a belt drive. In four stroke engines (i.e. Otto-type engines) the cam shaft rotates with half the speed of the crank shaft. To optimize loading and unloading the cylinders, the angular relation of the cam shaft's rotational position relative to the crank shaft's rotational position can be adjusted, e.g. in response to changes of throttle position or rpm (rotations per minute) of the crank shaft. This change in angular relation is as well referred to as 'timing' as the angular relationship defines the point of time of opening and closing the respective valves(s) relative to a particular position of the respective piston.

Generally speaking, a drive disc, like e.g. a sprocket or a pulley, may be attached to the cam shaft. By driving the drive disc, the cam shaft rotates accordingly. To adjust the timing of the cam shaft during operation of the combustion engine it has been suggested to support the drive disc on a hub, the latter being connect- ed to the cam shaft. By adjusting the angular relation of the hub to the drive disc, the angular relation of the cam shaft to the crank shaft and thus the timing maybe varied. To enable the angular adjustment of the hub relative to the drive disc a hydraulic drive in the drive disc-hub unit has been suggested by attaching vanes to the hub. The vanes each separate a fluid chamber in the drive disc into a first sub-chamber and a second sub-chamber. A hydraulic oil pump is connected to the first and second chambers to pump oil from one sub-chamber into the other, thereby swivelling the hub relative to the drive disc. The hydraulic pump is typically driven by the crank shaft. Pumping of the fluid from one sub-chamber into the other is controlled by a valve unit. Examples of this type of timing adjustment apparatus are disclosed e.g. in US 8,291,876 Bl and US 6,453,859 Bl.

Summary of the invention

The problem to be solved by the invention is to provide a reliable, mechanically simple and light weight apparatus for camshaft timing adjustment and a method for camshaft timing adjustment.

Solutions of the problem are described in the independent claims. The dependent claims relate to further improvements of the invention.

The apparatus for camshaft timing adjustment comprises at least a drive disc and a hub having a common rotational axis. The hub may comprise coupling means for attaching the hub to a cam shaft of a combustion engine. They thus may form a disc drive hub unit. The drive disc may be connected or configured to be connected by some sort of transmission to a crank shaft of a combustion engine, e.g. by a belt drive, a gear drive, a chain drive or the like. Of course, the hub can as well be attached to the crank shaft and the drive disc may be connected by the transmission to the cam shaft. For simplicity only, it is assumed herein that (i) the hub is attached to or configured to be attached to the camshaft, and that (ii) the disc drive is driven via some transmission by the crank shaft, but without restricting the application to this installation.

The drive disc may be attached to the hub via a bearing enabling the drive disc to swivel relative to the hub. For example, the hub may comprise a first plain bear- ing surface and the drive disc may comprise a complementary second plain bearing surface providing a plain bearing when attached to each other. Other types of bearings may as well be used.

The drive disc comprises at least one fluid chamber accommodating a vane. The vane is attached to the hub and separates the fluid chamber into a first sub- chamber and a second sub-chamber. Thus, providing a fluid flow from the first sub-chamber into the second sub-chamber enables to enlarge the volume of the second sub-chamber and to reduce the volume of the first sub-chamber (and vice versa). Accordingly, the vane moves, e.g. pivots or swivels in the fluid chamber and thus the hub rotates relative to the drive disc as a function of the fluid flow between the first and second sub-chambers.

The drive disc preferably comprises a ring segment shaped fluid channel connecting a first sub-chamber and second sub-chamber, thereby enabling a fluid communication between the connected first and second sub-chambers. In case the drive disc comprises only a single fluid chamber accommodating a single vane, the respective first and second sub-chambers are connected by the fluid channel. In case the drive disc comprises multiple fluid chambers each accommodating a vane being attached to the hub, the first sub-chamber of a first fluid chamber may be connected to a second sub-chamber of a second (e.g. neighboured) fluid chamber. The first sub-chamber of the second fluid chamber may be connected to a second sub-chamber the first fluid chamber or to a second fluid chamber of a further fluid chamber. In the latter case the first sub-chamber of the further fluid chamber may be connected to the second sub-chamber of the first fluid chamber (or of another further fluid chamber). For example the first and second sub-chambers may be daisy-chained with periodic boundary conditions. The term periodic boundary condition indicates that the first sub-chamber of the last fluid chamber in the chain is connected by a fluid channel with the second sub- chamber of the first fluid chamber in the chain. Relevant is only that each first sub-chamber is connected by a ring segment shaped fluid channel with a second sub-chamber, enabling a fluid communication between the connected first and second sub-chambers.

A fluid channel can be considered as ring segment like channel, wherein the ring axis is the common rotational axis. The ring segment form is not necessarily a circular ring segment, but it should preferably be able to accommodate a circular ring or a circular ring segment (hereinafter simply 'ring (segment)') having a ring axis being on the rotational axis. One may say that the ring (segment) is centred at the rotational axis. 'Being centred' means in this context that the ring (seg- ment) axis and thus its rotational axis coincide at least approximately with the common rotational axis of the hub and the drive disc.

The vane may comprise at least one ring segment shaped recess. The recess may be is centred around the rotational axis as well or in other words, the axis of the ring shaped recess coincides at least approximately with the rotational axis. The recess is not necessarily a circular ring segment, but it should preferably as well be able to accommodate the ring (segment) being centred around the common rotational axis. Essentially, the accommodated ring (segment) should be able to rotate around the rotational axis, thereby traveling through the fluid channel and/or the fluid chamber and optionally through the recess. In case of two or more fluid chambers, the ring (segment) should preferably be able to travel through the respective two or more fluid channels and/or fluid chambers and optionally through the optional recess(es). Further, the apparatus may comprise a rotor having a protrusion, for example a ring protrusion engaging into at least one of the fluid chamber(s) and the fluid channel(s) and optionally into the recess(es). The rotor is driven to rotate around the rotational axis while engaging with its protrusion into the fluid channel and/or the fluid chamber during rotation. It may optionally as well engage into the recess (if present) if required by the location of the respective parts, but it suffices, if the rotor engages or in other words protrudes into the fluid channel or the fluid chamber.

The rotation of the protrusion in the fluid channel(s) provides a shear stress, due do the viscosity of the fluid. This shearing stress results in a pressure gradient between the first and second sub-chambers being connected by the fluid channel. The pressure gradient translates into a torque being applied to the respective vane(s). The torque enables to rotate the hub relative to the drive disc. It is thus sufficient to control the rotational speed of the rotor relative to the fluid channel to rotate (swivel) the hub relative to the drive disc. Controlling of the rotational speed can be obtained very simple, e.g. by an electric motor having an output shaft being coupled to the rotor. In the simplest case, the output shaft of the electric motor is simply attached to the rotor. The heavy, expensive and inefficient hydraulic pump and control valves can be omitted. This safes a couple of kg and in addition enhances the combustion engines efficiency, due to omitting the hydraulic pump being driven by the crank shaft. In a particular preferred example, the camshaft timing apparatus enables not only to adjust the camshaft angle relative to the crankshaft angle, when the two shafts are rotating, but as well to depressurize at least one cylinder, prior to start up of the combustion engine. This depressurization reduces the power for accelerating the crank shaft. The starter and the battery may thus be configured smaller, saving additional weight. As explained above, the protrusion preferably forms a ring or comprises a sequence of ring segments. These are simple to manufacture, i.e. cheap and reliable. The protrusion can thus be considered to be a ring (segment) having an inner radius being greater than the inner radius of the fluid channel (s). The outer radi- us of the protrusion is smaller than the outer radius of the fluid channel(s). The protrusion thus 'fits' into the fluid channel(s).

For example, the rotor may comprise a rotor disc being orthogonal to the rotational axis. The disc may axially cover the fluid chamber. This provides a very compact light weight reliable apparatus, being simple to manufacture and to assemble. This holds true in particular, if the protrusion is attached to the disc. Of course, the rotor may comprise two or more protrusions that may be attached to the disc. In this case, the protrusion(s) may extend axially from the disc at least into the fluid channel(s).

In an alternative embodiment, the rotor comprises a circular cylindrical shell en- closing the drive (e.g. instead of the disc). In this case the (at least one) protrusion may be an annular ring extending radially inwards from the circular cylindrical shell at least into the fluid channel, which has to be located accordingly.

In a preferred embodiment, the free cross section of the recess is smaller than the free cross section of the fluid channel. This ensures by very easy to manufac- ture means that the fluid flow through the recess is smaller than the fluid flow through the fluid channel. To avoid ambiguities, here the term 'free cross section' denotes the cross sectional area of the recess and the fluid channel, respectively orthogonal to the pressure gradient.

Particularly preferred, the protrusion may comprise at least one bearing surface being opposed to at least one bearing surface of the recess. Thus the bearing surfaces may be configured to provide a fluid dynamic bearing, wherein the fluid in the fluid chamber and the fluid channel is the bearing fluid. In other words, if the gap between the protrusion and the recess is sufficiently small, there is almost no pressure drop between the first and second sub chambers because the gap is essentially fluid tight. The rotor glides on a fluid film and may be supported by the hub via the hydrodynamic fluid bearing. The shear stress being transmit- ted due to the viscosity of the fluid in the gap between the rotor and the vane additionally enhances the torque being transferred from the rotor to the vane and thus the hub.

As explained above, the rotor may be connected to the output shaft of an electric motor (e.g. directly or via a gear or another type of transmission). The rota- tional speed of the rotor may thus be controlled easily, e.g. in dependency of an angular position being measured by a cam shaft angular positioning sensor. For example, the apparatus may comprise a controller being connected to the cam shaft angular position sensor to receive angular positon data from the cam shaft angular position sensor. This data may be analyzed, e.g. compared to a target value of the respective data. The electric motor may be controlled by the controller to thereby control the rotational speed of the rotor to match the measured data with the target value within a given accuracy. In other words, the controller is configured to determine a target value for the camshaft angular position and to adapt the rotor's rotational speed relative to the drive disc to force the fluid at least partially via the fluid channel from the respective first into the respective second sub-chamber(s), thereby swivelling the vane in the fluid chamber and thus the hub relative to the drive disc. The controller can be configured to control the rotational speed of the rotor to depressurize at least one cylinder prior to starting the engine. To avoid ambiguities, the drive disc may be a sprocket or a pulley for being connected by a camshaft timing chain and/or drive belt to a crankshaft. The hub may comprise coupling means for attaching the hub to a camshaft or in other words, the hub may be connected to a cam shaft or be configured to be connected. The above explained apparatus may be used to implement a method for adjusting an angular position of a hub relative to a drive disc, wherein the drive disc comprises at least one fluid chamber accommodating a vane and wherein the vane is attached to the hub and separates the fluid chamber into a first sub- chamber and a second sub-chamber. Each first sub-chamber is connected by a ring segment shaped fluid channel with a second sub-chamber, enabling a fluid communication between the connected first and second sub-chambers. The method essentially consists in applying a shear stress to the fluid by rotating a rotor that engages into the fluid channel and/or the fluid chamber(s). As ex- plained above, the rotor may as well engage in a recess being provided by the vane(s), but it is sufficient if the rotor engages into the fluid channel (and/or the fluid chamber).

Above, it was considered to be clear that the at least one fluid chamber and the at least one fluid channel are filled with a fluid, like e.g. an oil. Theoretically, any fluid providing a viscosity may be used, i.e. as well gaseous fluids (at 'normal' temperatures, thereby excluding super fluid phases of bosonic gases in the vicinity of OK), but a liquid fluid (liquid) is preferred, in particular if the liquid fluid has friction reducing properties and/or prevents corrosion.

Description of Drawings In the following the invention will be described by way of example, without limitation of the general inventive concept, on examples of embodiment with reference to the drawings.

Figure 1 shows an exploded view of an apparatus for camshaft timing adjustment. Figure 2 shows the rotor of the apparatus of Fig. 2,

Figure 3 shows a cross of a further apparatus for camshaft timing adjustment. The apparatus in Fig. 1 comprises a drive disc 10. The drive disc 10 is a toothed belt disc, but it could be as well a sprocket disc or a pulley. The drive disc 10 is supported by a hub 50. The drive disc 10 and the hub 50 have a common rotational axis 2. The hub 50 and the drive disc can be swivelled relative to each oth- er around the rotational axis 2, as indicated by a double headed arrow.

The drive disc 10 comprises three fluid chambers 20, being separated by disc material 12 protruding radially inwards. The disc material 12 can as well be referred to as radial protrusion 12. The fluid chambers 20 have the shape of a cylinder segment having a bottom 24, side walls 23 and a radially outer side wall 25. The radially inner sidewall is provided by the hub 50. The number of fluid chambers 20 and vanes 60 may be varied as required. Here three are depicted.

Each fluid chamber 20 accommodates a vane 60 being attached to the hub 50. The vanes 60 have side walls 63. The vanes 60 extend radially and separate the respective fluid chamber 20 into a first sub-chamber 21 and a second sub- chamber 22. In other words, the vanes 60 are in contact with the bottom 24 and the radially outer sidewall 25 and glide over these surfaces when the hub 50 swivels relative to the drive disc 10. Each first sub-chamber 21 is connected by a fluid channel 15 to a second sub-chamber 22 of a neighboured fluid chamber 20. Thus by pumping a fluid from the first sub-chambers 21 via the fluid channels 15 into the second sub-chambers 22, the vanes 60 and thus the hub 50 rotates counter clockwise relative to the drive disc 10 around the rotational axis 2. If the fluid is pumped in the opposite direction, the hub 50 rotates clockwise relative to the drive disc 10 around the rotational axis 2.

Pumping of the fluid is provided by a rotor 80, having a drive shaft 81 being at- tached to a circular rotor disc 85. Attached to the rotor disc 85 are rings 90, as well referred to as 'protrusions 90' (cf. Fig. 2), configured for engaging into the fluid channels 15. To enable this engagement, the vanes 60 comprise a corre- sponding number of recesses 65 (Fig. 1). The radially inwardly and outwardly facing surfaces 91 of the protrusions 90 may be bearing surfaces providing with their respective opposed surfaces of the recess 65 a hydrodynamic bearing.

The rotor 80 may be driven e.g. by an electric motor M (see Fig. 3) to rotate rela- tive to the drive disc 10. The fluid adheres to the rings 90 and thus rotation of the rotor provides a pressure gradient between the first sub-chambers 21 and their respective connected second sub-chambers 22. The fluid thus flows from the first sub-chambers 21 into the second sub-chambers 22 (or in the opposite direction, depending on the sign of the gradient). It should be noted, that the pres- sure gradient between the left side of a sidewall 63 and the right (opposed) side wall 63 of the same vane 60 causes a force being essentially the pressure gradient times the surface of the sidewall 63 (omitting corrections for non-alignment of the side walls 63 with the respective radial direction), which has to compensate for the forces being required to rotate vanes 60 and thus the hub 50. In this example, the vanes 60 are integrally formed by the hub, but this is only an advantageous detail. Further, the fluid chambers 20 have been shown to be open, but this is for illustrative purpose only, of course they are fluid tight. For example, the rotor disc 85 may cover and seal the fluid chambers.

Fig. 3 shows a cross section of a further camshaft timing adjustment apparatus 1, which is very similar to the apparatus as explained with respect to Fig. 1 and 2. The section plane of Fig. 3 corresponds to the plane A-A if the two timing apparatuses would be identical. The description of Figs. 1 and 2 can be read as well with respect to Fig. 3; the main difference is that the rotor 80 has only three instead of four ring formed protrusions 90 (rings 90). Accordingly the number of recesses 65 in the vanes 60 has been adapted as well. Beyond the rotor disc 85 has an enlarged diameter, covering the fluid chambers 20 completely. To seal the fluid chambers 20, the rotor 80 provides a small ring that engages into a com- plementary ring shaped groove (labyrinth sealing). Further, a fastening ring 100 is bolted to the drive disc 10 by bolts 101 to hold the rotor 80 and as well the hub 10 in their axial position. The clearance between the parts is partially slightly exaggerated, to ease distinguishing them.

List of reference numerals

1 apparatus for camshaft timing adjustment

2 rotational axis

10 drive disc

12 disk segment / protrusion

15 fluid channel

20 fluid chamber

21 first sub-chamber

22 second sub-chamber

23 side wall of sub-chamber

24 bottom of sub-chamber

25 outer side wall of sub-chamber

50 hub

60 vane

63 side wall of vane

65 recess in vane

80 rotor

81 shaft

85 rotor disc

90 protrusion / ring

91 bearing surface (optional)

100 fastening ring

101 bolt

M Motor

Claims

An apparatus (1) for camshaft timing adjustment, comprising at least a drive disc (10) and a hub (50) having a common rotational axis (2), wherein the drive disc (10) comprises at least one fluid chamber (20) accommodating a vane (60), wherein the vane (60) is attached to the hub (50) and separates the fluid chamber (20) into a first sub-chamber (21) and a second sub- chamber (22),

characterized in that the drive disc (10) comprises a ring segment shaped fluid channel (15), connecting each first sub-chamber (21) with a second sub- chamber (22), enabling a fluid communication between the connected first and second sub-chambers (21, 22), wherein the fluid channel (15) is centered around the rotational axis, the apparatus comprises a rotor (80) having a protrusion (90), the rotor (80) being driven to rotate around the rotational axis (2) while engaging with its protrusion (90) the fluid channel (15) during rotation.

The apparatus (1) of claim 1,

characterized in that

the vane (60) comprises at least one ring segment shaped recess (65), the recess (65) being centred around the rotational axis (2) and in that the rotor (80) engages in the recess (65).

The apparatus (1) of claim 2,

characterized in that

the free cross section of the recess (65) is smaller than the free cross section of the fluid channel (15).

4. The apparatus (1) of one of claims 2 or 3,

characterized in that

the protrusion (90) comprises at least one bearing surface being opposed to at least one bearing surface of the recess, said bearing surfaces provid- ing a fluid dynamic bearing, wherein the fluid in the fluid chamber (20) is the bearing fluid.

5. The apparatus (1) of one of claims 1 tor 4,

characterized in that

the protrusion forms a ring (90) or comprises at least one ring segment.

6. The apparatus (1) of one of claims 1 to 5,

characterized in that

the rotor (80) comprises a rotor disc (85) being orthogonal to the rotational axis (2), wherein the rotor disc (85) provides a cover for the fluid chamber (20).

7. The apparatus (1) of claim 6,

characterized in that

the protrusion (90) is attached to the rotor disc (85).

8. The apparatus (1) of claim 7,

characterized in that

the protrusion (90) extends axially from the rotor disc (85) into the recess (65).

9. The apparatus (1) of one of claims 1 to 8,

characterized in that

the rotor (80) is connected to the output shaft of an electric motor (M). The apparatus (1) of one of claim 9,

characterized in that

the apparatus (1) comprises a controller being connected to a cam shaft angular position sensor to receive angular positon data from the cam shaft angular position sensor and to the electric motor to control the rotational speed of the rotor (80) by adjusting the rotational speed of the motor's output shaft, wherein the controller is configured to determine a target value for the camshaft angular position and to adapt the rotor's (80) rotational speed relative to the drive disc (10) to force the fluid at least partially via the fluid channel (15) from the respective first into the respective second sub-chamber (21, 20), thereby swivelling the vane (60) and thus the hub (50) in the fluid chamber (20).

The apparatus (1) of one of claims 1 to 10,

characterized in that

the drive disc (10) is a sprocket or a pulley for being connected to a camshaft timing chain and/or drive belt to a crankshaft.

The apparatus (1) of one of claims 1 to 11,

characterized in that

the hub (50) comprises coupling means for attaching the hub (50) to a camshaft.

A method for adjusting an angular position of a hub (50) relative to a drive disc (10), wherein the drive disc (10) comprises at least one fluid chamber (20) accommodating a vane (60), wherein the vane (60) is attached to the hub (50) and separates the fluid chamber (20) into a first sub- chamber (21) and a second sub-chamber (22), wherein a first sub- chamber (21) and a second chamber (22) are in fluid communication via a fluid channel (15) being provided by the drive disc (10), characterized in that

shear stress is applied to the fluid by rotating a rotor (80) that engages into the fluid channel (15), thereby changing a pressure gradient between the first chamber (21) and the second chamber (22) being connected by the fluid channel.