Patent Application
20070056540
1. Field of the Invention
The invention relates to a control valve for influencing the action of a pressure medium on a camshaft adjuster of an internal combustion engine, in particular according to the preamble of claim 1. The invention additionally relates to a method for producing a control valve, in particular according to the preamble of claim 10.
2. Background of the Invention
A control valve for influencing the action of a pressure medium on a camshaft adjuster of an internal combustion engine is known from the applicant's patent application DE 10 2004 036 096.0, which was not published before the priority date of the present application, in which control valve a control piston is axially displaceable in a blind bore of a valve housing, wherein the action on a spring element is varied with the displacement of the control piston. The spring element is supported with one foot point on an end side of the control piston and with the opposite foot point on the base of the blind bore of the valve housing. The control valve has a pressure medium port, two tank ports and two working ports, which are associated with oppositely-acting working chambers of a hydraulic camshaft adjuster. In one axial position of the control piston, in the control valve, a first working port is connected to a tank port and the second working port is connected to the pressure medium port, so that it is possible to effect an actuating movement of the camshaft adjuster during which the working chamber which is associated with the second working port increases in volume. In another axial position of the control piston, the second working port is connected to a tank port and the first working port is connected to the pressure medium port, so that it is possible to effect an actuating movement of the camshaft adjuster during which the working chamber which is associated with the first working port increases in volume.
The invention is based on the object of simplifying production of the control valve mentioned in the introduction while further ensuring or improving its functions.
According to the invention, the object is achieved by means of a control valve according to the features of independent patent claim 1. Preferred embodiments of a control valve according to the invention emerge corresponding to the features of dependent patent claims 2 to 9. A further solution of the object on which the invention is based is provided by means of a method according to independent patent claim 10. Embodiments of the method according to the invention emerge from dependent patent claims 11 to 13.
The invention is based on the realization that the manufacture of the valve housing with a blind bore for holding the control piston has potential for optimization. Imprecise manufacture of the position of a base of the blind bore corresponding to the prior art can in some circumstances influence the function of the control valve, for example the foot point of a spring element, an end position of the control piston and/or the hydraulic conditions, for which reason the blind bore must be manufactured with a high degree of accuracy. It can additionally be necessary for the base of the blind bore to have an additional opening which forms a port, for example a tank port, and for the production of which a further bore must be formed in the valve housing in the region of the base of the blind bore. Here, impurities and burrs must be carefully avoided in the interior of the valve housing which, in an embodiment with a blind bore, is only completely open at one side, since said impurities and burrs can lead, during operation of the control valve, to adverse mechanical effects, increased wear to the point of failure of the control valve or of components which are hydraulically connected to the control valve. On the other hand, the production of a blind hole requires the use of a special tool, in particular a reamer, which, for example, makes an additional undercut necessary in the region of the base of the blind bore. In some circumstances, this requires an increased installation length of the control valve. In addition, the shape of the end face of the tool predefines the shape of the base of the blind bore which can be obtained, so that, in some circumstances, integration of further functions into the base of the blind bore is only possible with difficulty. For example, the base of the blind bore cannot delimit the actuating movement of the control piston. Such delimitation of the actuating movement of the control piston is, however, of increased significance since, for example, when a predefined end position of the control piston is exceeded, for example as a result of tolerances of the components of the control valve, the hydraulic connection to a port is only insufficiently opened or closed. Known solutions operate in that an end stop of the control piston is provided by the spring element “being compressed fully” for the end stop to be reached, wherein the end position is however still dependent on tolerances, also in the manufacture of the blind bore.
According to the invention, the previously explained realizations are implemented in that the spring element is supported not on a base of the blind bore, but rather, by means of the foot point situated at the opposite side from the control piston, on a housing insert. This means that both the valve housing and the housing insert can be produced separately, as a result of which
The embodiment according to the invention having a housing insert makes it possible, for example, for the bore of the valve housing for holding the control piston to be formed as a through bore, so that said bore can be produced more simply and with greater precision, and the formation of burrs is reliably avoided. The foot point of the spring element is then exactly predefined by inserting the housing insert into the valve housing, as a result of which the position of the foot point can be predefined with high accuracy. On the other hand, for different control valves, it is possible in some circumstances for the same valve housing to be used in connection with different housing inserts, different positions of the housing insert relative to the valve housing and/or different support locations of the spring element by means of different geometries of the housing inserts which are used.
According to a preferred embodiment of the control valve according to the invention, the housing insert is embodied in a multifunctional fashion in that, in addition to the support of the foot point for the spring element, said housing insert has recesses through which the pressure medium can pass out of the control valve in order to form a port, in particular a tank port. The production of the recesses in a housing insert is simplified with respect to such production for the design having a blind bore, with additional configuration possibilities for the recesses, for the number of recesses and for their distribution over the housing insert also being provided. By way of example, the recesses can extend inwards from an outer edge of the housing insert, so that radially outwardly situated webs or spring lips are formed between the recesses, which webs or spring lips can advantageously be used for a connection between the housing insert and the valve housing, while in some circumstances, a closed central region of the housing insert is provided in a radially inward region.
There are many possibilities for a connection between the housing insert and the valve housing. For example, the connection can be a form-fitting, force-fitting or cohesive connection. The housing insert can be pressed or screwed into the valve housing. According to one particular proposal for a simple design of the connection of the housing insert to the valve housing, which connection is also simple to assemble and, if appropriate, to disassemble, the invention proposes that the housing insert is clipped into the valve housing.
According to a refinement of the invention, in longitudinal section, the housing insert is approximately in the form of the longitudinal section of a hat or of a pot. By elastically deforming the housing insert, the “brim” of the hat or the edge of the pot can be radially compressed and expanded, so that the edge or brim is clipped into a suitable groove of an inner lateral surface of the valve housing. Accordingly, for manufacture, only one suitably formed groove, if appropriate with at least one insertion slope, must be formed in the lateral surface of the valve housing, while the housing insert can be produced cost-effectively, for example as a sheet metal part or a shaped part. The previously mentioned recesses can be advantageous in promoting the elastic compression and expansion of the edge or of the brim in the radial direction, said recesses forming elastic webs or spring lips as mentioned previously.
According to a further proposal of the invention, the mid-region of the hat is conical, said mid-region adjoining the edge or the brim. The desired deformation for clipping the housing insert in can be provided in this case by elastically deforming the conical mid-region and/or by changing the cone angle of the mid-region. In addition, the conical design of the mid-region offers improved possibilities for mounting the housing insert into the valve housing, as will be explained in more detail in the following.
According to a refinement of the invention, in addition to the function of supporting a foot point of the spring element and the function of forming the recesses for the port, the housing insert fulfills the additional function of providing a stop for the control piston, in order to predefine an axial end position of the control piston. This results in a defined end position of the control piston, as a result of which insufficient desired opening positions to one of the ports are avoided. At the same time, it is possible to avoid the situation where a stop for the control piston is provided only by the spring element “being compressed fully”. The position of the stop can be predefined exactly by means of the separately produced housing insert which is inserted into the valve housing. A spring action and/or damping action for an “impact” of the control piston against the stop can be obtained by suitably configuring the mechanical properties of the housing insert and/or the hydraulic properties in the region of the housing insert.
A particularly compact design is obtained if the control valve is suitable for being integrated into a camshaft. This additionally results, in some circumstances, in short hydraulic transmission paths between the control valve and the associated working chambers of the camshaft adjuster.
To produce a control valve, a bore is initially formed in the valve housing, said bore being at least of a length which permits it to hold both a control piston and also a housing insert. In the simplest case, said bore is a through bore with a constant cross section, wherein different cross-sectional configurations along the length of the bore are, however, also possible. In a subsequent working operation, a groove is formed in the bore of the valve housing, into which bore a housing insert can later be clipped. The housing insert is subsequently radially compressed. Said compression preferably takes place in such a way that the outer diameter of the housing insert is less than the diameter of the bore in that region in which the housing insert is inserted into the valve housing. In said state, the housing insert is then inserted into the bore of the valve housing, approximately as far as into the region of the groove, where the housing insert is then radially expanded, in particular by means of elastic forces of the housing insert. In the “clipped-in position”, the radially outer edge of the housing insert is ultimately received in the groove of the valve housing. The radial compression and/or the insertion of the housing insert into the groove can be assisted by means of suitable insertion slopes in the region of the valve housing. Alternatively, or in addition, the compression and expansion can take place using suitable tools.
According to a refinement of the invention, the housing insert has a conical mid-region, wherein the housing insert is radially elastically expanded and compressed by changing the opening angle of the conical mid-region.
Assembly is particularly simple if the housing insert is held in the compressed state by means of a tool which “retains” the previously mentioned reduced opening angle of the cone until the housing insert is arranged in the valve housing at the appropriate position for expansion.
Advantageous refinements of the invention emerge from the dependent patent claims and from the entire description. Further features can be gathered from the drawings—in particular the illustrated geometries and the relative dimensions of several components with respect to to one another and their relative arrangement and operative connection. The combination of features of different embodiments of the invention, or of features of different patent claims, deviating from the selected references back, is likewise possible and is hereby encouraged. This also relates to features which are illustrated in separate drawing figures or are mentioned in the description thereof. Said features can also be combined with features of different patent claims.
In the figures:
Axially running vane grooves 10 are formed on the outer lateral surface of the rotor 3, with one radially extending vane 11 being formed in each vane groove 10.
One vane 11 extends into each recess 5, with the vanes 11 bearing against the stator 2 in the radial direction and against the side covers 7, 8 in the axial direction. Each vane 11 divides a recess 5 into two pressure chambers 12, 13 which act counter to one another. In order to ensure that the vane 11 bears against the stator 2 in a pressure-tight manner, leaf spring elements 15 are attached between the groove bases 14 of the vane grooves 10 and the vanes 11, said leaf spring elements exerting a force on the vanes 11 in the radial direction.
The first and second pressure chambers 12, 13 can be connected via a control valve 18 to a pressure medium pump 19 or to a tank 20 by means of first and second pressure medium lines 16, 17. This forms an actuating drive which permits a relative rotation of the stator 2 with respect to the rotor 3. Here, it is provided either that all the first pressure chambers 12 are connected to the pressure medium pump 19 and all the second pressure chambers 13 are connected to the tank 20, or that the connections are in the exact opposite configuration. If the first pressure chambers 12 are connected to the pressure medium pump 19 and the second pressure chambers 13 are connected to the tank 20, the first pressure chambers 12 expand at the expense of the second pressure chambers 13. This results in a displacement of the vanes 11 in the circumferential direction, in the direction illustrated by the arrow 21. The rotor 3 is rotated relative to the stator 2 as a result of the displacement of the vanes 11.
In the illustrated embodiment, the stator 2 is driven by means of a crankshaft chain drive (not illustrated) which engages on the drive wheel 4 of said stator 2. It is likewise conceivable for the stator 2 to be driven by means of a belt drive or toothed drive. The rotor 3 is connected to a camshaft (not illustrated) in a force-fitting, form-fitting or cohesive fashion, for example by means of a press fit or by a screw connection by means of a central screw. The relative rotation of the rotor 3 with respect to the stator 2, as a consequence of the inlet or outlet of pressure medium into or out of the pressure chambers 12, 13, results in a phase shift between the camshaft and the crankshaft. Targeted inlet and outlet of pressure medium into the pressure chambers 12, 13 can therefore be used to vary the control times of the gas exchange valves of the internal combustion engine in a targeted fashion.
In the illustrated embodiment, the pressure medium lines 16, 17 are formed as substantially radially arranged bores which extend from a central bore 22 of the rotor 3 to the outer lateral surface thereof. A central valve (not illustrated) can be arranged within the central bore 22, by means of which central valve the pressure chambers 12, 13 can be connected to the pressure medium pump 19 or the tank 20 in a targeted fashion. A further option is to arrange a pressure medium distributor within the central bore 22, which pressure medium distributor connects the pressure medium lines 16, 17 via pressure medium ducts and annular grooves to the ports of an externally attached control valve 18.
The substantially radially running side walls 6 of the recesses 5 are provided with moldings 23 which extend into the recesses 5 in the circumferential direction. The moldings 23 serve as stops for the vanes 11 and ensure that the pressure chambers 12, 13 can be supplied with pressure medium even when the rotor 3 assumes one of its extreme positions relative to the stator 2, in which position the vanes 11 bear against one of the side walls 6.
In the event of insufficient pressure medium supply to the device 1, for example during the starting phase of the internal combustion engine, the rotor 3 is moved relative to the stator 2 in an uncontrolled fashion as a result of alternating and drag torques which the camshaft exerts on said rotor 3. In a first phase, the drag torques of the camshaft push the rotor relative to the stator in a circumferential direction which opposes the rotational direction of the stator, until said rotor and stator come into contact at the side walls 6. Subsequently, the alternating torques which the camshaft exerts on the rotor 3 lead to reciprocating oscillation of the rotor 3 and therefore of the vane 11 in the recesses 5, until at least one of the pressure chambers 12, 13 is completely filled with pressure medium. This leads to increased wear and to noise generation in the device 1. In order to avoid this, a locking element 24 is provided in the device 1. In addition, a pot-shaped piston 26 is arranged in an axial bore 25 of the rotor 3, which pot-shaped piston 26 is acted on with force in the axial direction by means of a spring 27. The spring 27 is supported at one side in the axial direction on a ventilation element 28 and is arranged with its remote axial end within the pot-shaped piston 26. A slotted guide 29 is formed in the first side cover 7 such that the rotor 3 can be locked, relative to the stator 2, in a position which corresponds to the position during starting of the internal combustion engine. In said position, the piston 26 is pushed into the slotted guide 29 by means of the spring 27 when there is insufficient pressure medium supply to the device 1. In addition, means are provided to push the piston 26 back into the axial bore 25, and therefore to release the locking, when there is sufficient pressure medium supply to the device 1. This is conventionally achieved by means of pressure medium which is conducted via pressure medium lines (not illustrated) into a cut-out 30 which is formed on the cover-side face end of the piston 26. In order to be able to conduct leakage oil out of the spring space of the axial bore 25, the ventilation element 28 is provided with axially running grooves, along which the pressure medium can be conducted to a bore in the second side cover 8.
A control piston 37 which is likewise of substantially hollow cylindrical form is arranged in an axially displaceable fashion within the valve housing 34. One axial end of the control piston is delimited in a pressure-tight fashion by means of a wall section 37a. The wall section 37a can be formed in one piece with the control piston or can be formed separately from the latter. The control piston 37 can be placed and held in any desired position within two extreme values, counter to the spring force of the first spring element 33, by means of an actuating element 32 (not illustrated).
The outer lateral surface of the control piston 37 is provided with a second, a third and a fourth annular groove 38, 39, 40. The second and the third annular grooves 38, 39 communicate with the interior of the control piston 37 via second and third openings 41, 42. The second annular groove 38 is formed in such a way that it communicates with the first openings 36 of the first annular groove 35 of the pressure medium port P in all positions of the control piston 37 relative to the valve housing 34.
During operation of the internal combustion engine, pressure medium passes from the pressure medium port P, via the second annular groove 38 and the second openings 41, into the interior of the control piston 37. In the first position of the control piston 37, illustrated in
If the electromagnetic actuating element 32 is supplied with electrical current, the control piston 37 is displaced counter to the spring force of the first spring element 33. As a result, the overlap of the first openings 36 of the working port B by a first control edge 43 of the third annular groove 39 increases. The overlap of the first openings 36 of the working port A by a second control edge 44 of the control piston 37 likewise increases. When the control piston 37 reaches a middle position (not illustrated), the working port A is no longer connected to the axial tank port T2 as a result of complete overlap of the second control edge 44. In addition, neither the working port A nor the working port B communicates with the third annular groove 39. Alternatively, the control piston 37 can be designed in such a way that, in the middle position, both working ports A, B communicate with the third annular groove 39.
If the control piston 37 is displaced further counter to the spring force of the first spring element 33, a third control edge 45 unblocks the first openings 36 of the working port A to the third annular groove 39. Pressure medium which flows in from the pressure medium port P now passes only to the working port A. At the same time, the fourth annular groove 40 communicates both with the working port B and with the radial tank port Tl. In this way, pressure medium passes from the pressure medium pump 19 into the first pressure chambers 12 which leads to a relative rotation of the rotor 3 with respect to the stator 2. The pressure medium which is pushed out of the second pressure chambers 13 passes via the working port B and the fourth annular groove 40 to the radial tank port T1. The third control edge 45 and the fourth annular groove 40 can be formed in such a way that, during displacement of the control piston 37, the working port A is initially connected to the pressure medium pump 19 and the working port B is then connected to the tank 20. Alternatively, both connections can be produced at the same time.
A substantially cylindrical filter 46 is arranged within the control piston 37. The filter 46 comprises a frame 47, preferably made from plastic, and at least one filter section 48. The filter section 48 is preferably composed of a mesh of plastic or metal, with the frame 47 being non-detachably connected to the filter sections 48. At the axial ends of the filter 46, the frame 47 has in each case one substantially circular segment 49, with the circular segments 49 being connected to one another by means of a plurality of longitudinal struts 50. The filter 46 is fixed within the control piston 37 in a force-fitting fashion by means of the circular segments 49. Here, it is advantageous to form an axial stop 51 within the control piston 37, said axial stop 51 serving as a travel delimitation when pressing the filter 46 into the control piston 37. Alternatively, the filter 46 can be pressed in in a manner which is controlled in terms of travel.
The filter 46 is arranged in the region of, and completely overlaps, the second openings 41. The filter 46 bears, at one of its axial ends, against the axial stop 51. The other axial end rests on a pot-shaped sleeve 52 which is fixed in the interior of the control piston 37 in a force-fitting manner. This ensures that the filter 46 maintains its position during operation of the internal combustion engine.
The sleeve 52 additionally closes off the control piston 37 in the axial direction and can serve as an engagement point of a plunger rod (not illustrated) of the actuating element 32.
The circular segments 49 of the filter 46 are connected in the radial direction to an inner lateral surface 53 of the control piston 37 in a pressure-tight manner, while a gap 54 is provided between the longitudinal struts 50 and the inner lateral surface 53.
Pressure medium flowing in from the pressure port P passes via the second openings 41 into an annular groove which is formed between the filter sections 48 and the inner lateral surface 53 and runs around the filter 46. The pressure medium passes via the filter sections 48 into the interior of the control piston 37, as a result of which any impurities which are present in the pressure medium are effectively kept away from the control edges 43, 44, 45.
Pressure medium flowing into the control valve 18 passes to the non-return valve 55 after passing through the filter 46. As a result of the arrangement of the filter 46 directly downstream of the pressure port P, the control edges 43, 44, 45 and the non-return valve 55 are effectively protected from damage on account of dirt particles in the pressure medium. Above a certain pressure within the control piston 37, the blocking body 57 is displaced counter to the spring force of the second spring element 58, and pressure medium can pass to the working ports A, B via fourth openings 60, which are formed in the housing 56, and the third openings 42.
During operation of the internal combustion engine, pressure pulsations are generated within the device 1 as a result of alternating torques of the camshaft. In the process, pressure peaks occur which are transmitted into the hydraulic system and can damage other consumers. The arrangement of a non-return valve 55 between the pressure chambers 12, 13 and the pressure medium port P prevents transmission of said pressure peaks into the hydraulic system. This protects both the pressure medium pump 19 and further consumers which are connected to said pressure medium circuit. In said embodiment, the non-return valve 55 is advantageously arranged within the control piston 37, and thus requires no additional installation space. A further advantage is that, specifically when using the control valve 18 as a central valve, the path between the location at which the pressure pulsations are generated and the non-return valve 55 is a minimum. Pressure fluctuations are intercepted practically at the point of generation.
In this embodiment, that face end of the control piston 37 which faces away from the tank port T2 is formed such that it is closed off. The housing 56 is H-shaped in longitudinal section, with the filter 46 being arranged in one chamber of the H and the blocking body 57 with the second spring element 58 being arranged in the other chamber. The second spring element 58 is supported on a closure 61. The radially running part of the housing 56 is provided with an opening which is matched to the blocking body 57 and serves as a seat 59.
During operation of the internal combustion engine, pressure medium passes into the interior of the valve housing 34 via the axially aligned pressure medium port P. Depending on the position of the control piston 37 within the valve housing 34, the pressure medium passes either via second openings 41 to the working port B or via third openings 42 to the working port A. At the same time, the respective working port A, B which is not being acted on by pressure medium is connected via the first annular groove 35 to the tank port T.
A filter 46 is arranged between the pressure medium port P and the working ports A, B. The filter 46 is formed in the shape of a pot and comprises a frame 47 and filter sections 48. At the side which faces toward the pressure port P, the frame 47 is provided with a radially extending collar which serves as an axial stop of the filter 46. In addition, it is possible to fix the filter 46 to the valve housing 34 in a form-fitting, force-fitting or cohesive manner. As in the embodiments described previously, a non-return valve 55 can also be arranged between the pressure medium port P and the working ports A, B here.
A control valve 70 according to the invention has a control piston 71 which is arranged in a valve housing 72 in an axially displaceable fashion. The control valve 70 and the control piston 71 are, for example, formed corresponding to one of the exemplary embodiments illustrated in FIGS. 1 to 6. However, the bore 73 of the valve housing 72 is formed according to
As illustrated in
Annular corners 89 or tapers are provided in the transition region between the recesses 88 and the edge 85, said annular corners 89 or tapers, together with the rest of the design of the housing insert 79, being intended to prevent the housing insert 79 becoming jammed in the valve housing during assembly. The conical mid-region 86 has an opening angle 90. For elastic radial compression of the housing insert 79, the opening angle 90 is reduced and/or the mid-region 86 is elastically deformed. During radial expansion for clipping the housing insert 79 into the groove 80, the opening angle 90 increases again.
The housing insert 79 is preferably inserted into the valve housing 72 using a tool 91 according to
The recesses 88 form a flow cross section to the port, for example in the direction of the tank. Here, a suitable selection of the ratio between the flow cross sections at port B in the control valve 70 and the recesses 88 is significant. If the outflow cross section, which is predefined by the recesses 88, is too small relative to the flow cross sections of the other ports involved, an undesired dynamic pressure can build up in the valve.
In an assembly process, the housing insert 79 can be supplied continuously, for example by means of an oscillating conveyer. Through suitable selection of the geometry of the housing insert, of the sheet metal thickness, and by specifying the curvatures and the opening angle 90 as well as the material and suitable material treatment processes, the force required for deforming the housing insert 79 and the securing effect which can be obtained by clipping the housing insert 79 into the groove 80 can be structurally predefined. The mechanical strength of the housing insert 79 and/or the surface hardness, in particular in the support region of the pressure spring 76, is preferably increased by means of case-hardening and tempering.
1 Device
2 Stator
3 Rotor
4 Drive wheel
5 Recesses
6 Side wall
7 First side cover
8 Second side cover
9 Connecting element
10 Vane groove
11 Vane
12 First pressure chamber
13 Second pressure chamber
14 Groove base
15 Leaf spring element
16 First pressure medium line
17 Second pressure medium line
18 Control valve
19 Pressure medium pump
20 Tank
21 Arrow
22 Central bore
23 Moldings
24 Locking element
25 Axial bore
26 Piston
27 Spring
28 Ventilation element
29 Slotted guide
30 Cut-out
31 Pressure medium circuit
32 Actuating element
33 First spring element
34 Valve housing
35 First annular groove
36 First openings
37 Control piston
37 a Wall section
38 Second annular groove
39 Third annular groove
40 Fourth annular groove
41 Second opening
42 Third opening
43 First control edge
44 Second control edge
45 Third control edge
46 Filter
47 Frame
48 Filter section
49 Segment
50 Longitudinal struts
51 Axial stop
52 Sleeve
53 Lateral surface
54 Gap
55 Non-return valve
56 Housing
57 Blocking body
58 Second spring element
59 Seat
60 Fourth opening
61 Closure
70 Control valve
71 Control piston
72 Valve housing
73 Bore
74 Chamfer
75 Chamfer
76 Pressure spring
77 Foot point, left
78 Foot point, right
79 Housing insert
80 Groove
81 Lateral surface
82 Annular insert
83 Stop
84 Brim
85 Edge
86 Mid-region
87 Central region
88 Recesses
89 Annular corner
90 Opening angle
91 Tool
92 Blind bore
93 Shoulder
94 Bore
95 Longitudinal axis
P Pressure medium port
T Tank port
T1Radial tank port
T2Axial tank port
A First working port
B Second working port
| Number | Date | Country | Kind |
|---|---|---|---|
| 102005037480.8 | Aug 2005 | DE | national |
