Camshaft adjuster including a discharge valve

Abstract

A hydraulic camshaft adjuster (1), in particular a vane-type hydraulic camshaft adjuster, including a rotor (2) and a stator (3) which are mounted to rotate with respect to each other, a cover (10) fixed on the stator (3), including a locking receiver and at least one locking pin (11, 12) accommodated in the rotor (2), the locking pin being slidable in the axial direction and prestressed in the direction of the locking receiver, and a hydraulic channel (27, 28, 29) to apply pressure of the locking pin (11, 12) against the prestress of same, the hydraulic channel being able to be filled and emptied with a hydraulic medium via a central screw, wherein in the rotor (2) at least one additional discharge channel (37, 38, 39, 40) fluidically connected to the hydraulic channel (27, 28, 29) is formed with a discharge valve (33, 34, 35, 36), wherein preferably the discharge valve (33, 34, 35, 36) closes the discharge channel (37, 38, 39, 40) when the locking pin (11, 12) is pressurized and opens the discharge channel when the hydraulic pressure acting on the locking pin (11, 12) falls.

Claims

1. A hydraulic camshaft adjuster comprising: a rotor and a stator supported rotatably relative to one another; a cover fixed to the stator and including a locking receptacle; at least one locking pin accommodated in the rotor in such a way that the at least one locking pin is displaceable in the axial direction, and is pretensioned with pretension in a direction of the locking receptacle; a hydraulic channel for acting with pressure on the at least one locking pin against the pretension, and fillable with a hydraulic medium emptiable via a central screw; and at least one additional discharge channel fluidically connected to the hydraulic channel and including a discharge valve formed in the rotor, wherein the discharge valve includes a valve seat fixed in the rotor, and a valve body movable with respect to the valve seat including a flow path, wherein the discharge valve includes a cartridge fixed in the at least one additional discharge channel and forms the valve seat.

2. The hydraulic camshaft adjuster as recited in claim 1 wherein the discharge valve is integrated in such a way that the discharge valve closes the at least one additional discharge channel when the at least one locking pin is acted on by hydraulic pressure, and opens the at least one additional discharge channel when the hydraulic pressure acting on the at least one locking pin drops, or the discharge valve is a shut-off valve and is situated in the at least one additional discharge channel in the rotor.

3. The hydraulic camshaft adjuster as recited in claim 1 wherein the hydraulic channel is formed in the rotor or in the cover, and forms a flow path for hydraulic medium through the rotor from a supply line to the at least one locking pin, and from the at least one locking pin to the discharge valve and to the at least one additional discharge channel.

4. The hydraulic camshaft adjuster as recited in claim 1 wherein the hydraulic channel is a ring channel leading from a supply line via the at least one locking pin back to the supply line.

5. The hydraulic camshaft adjuster as recited in claim 1 wherein the valve body includes a diaphragm whose axial width is less than an axial length of the valve body, or whose flow cross-sectional area is less than a flow cross-sectional area of the flow path.

6. The hydraulic camshaft adjuster as recited in claim 1 wherein the valve body is pretensioned into an open position, the at least one additional discharge channel being open in the open position, via a compression spring.

7. The hydraulic camshaft adjuster as recited in claim 1 wherein the valve body is provided with a through hole.

8. The hydraulic camshaft adjuster as recited in claim 1 wherein the discharge valve is a shut-off valve and the cartridge has at least one recess forming a flow path for hydraulic medium through the at least one additional discharge channel when the shut-off valve is open.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is explained in greater detail below with reference to exemplary embodiments, with the aid of drawings.

(2) FIG. 1 shows a top view onto one specific embodiment of a camshaft adjuster according to the present invention, without a cover;

(3) FIG. 2 shows a perspective view of a cartridge of a shut-off valve of a camshaft adjuster according to the present invention;

(4) FIG. 3 shows a perspective view of a valve body of a shut-off valve of a camshaft adjuster according to the present invention;

(5) FIG. 4 shows a sectional view of the shut-off valve in parallel to the rotation axis of the camshaft adjuster, in the closed state;

(6) FIG. 5 shows a sectional view of the shut-off valve in parallel to the rotation axis of the camshaft adjuster, in the open state;

(7) FIG. 6 shows a sectional view of the shut-off valve in parallel to the rotation axis of the camshaft adjuster during closing, between the open position of FIG. 5 and the closed position of FIG. 4; and

(8) FIG. 7 shows a schematic illustration of the forces acting on the valve body.

DETAILED DESCRIPTION

(9) The figures are merely schematic, and are used only for an understanding of the present invention. Identical elements are provided with the same reference numerals. Details of the various exemplary embodiments may also be combined and/or exchanged with one another.

(10) FIG. 1 shows a camshaft adjuster 1 according to the present invention in a top view, without a cover. Camshaft adjuster 1 is used for adjusting the rotation angle of a camshaft, not shown, with respect to the crankshaft of an internal combustion engine. The gas exchange valves of the internal combustion engine are actuated with the aid of the camshaft. The optimum valve timing changes with the engine speed. For the intake valves, the timing is retarded with increasing engine speed, and for the exhaust valves it is advanced. For engines having separate camshafts for the intake valves and exhaust valves, there is the option of easily achieving the desired speed-dependent adaptation of the timing by appropriately rotating the camshafts.

(11) Camshaft adjuster 1 includes a rotor 2 and a stator 3 which are concentrically rotatable about a rotation axis 4 of camshaft adjuster 1, and rotatable relative to one another about rotation axis 4. Vane cells 5, 6, 7, 8 are formed between rotor 2 and stator 3, and are to be acted on by hydraulic medium, for example pressure oil, in order to effectuate a relative rotation of rotor 2 and stator 3. The pressure oil is supplied to vane cells 5, 6, 7, 8 via hydraulic channels in rotor 2 via a central screw, not illustrated in the figures, which is situated in a central through opening 9 in rotor 2.

(12) A cover 10 (see FIG. 4) is fixed to stator 3 on the front side, i.e., on the front surface shown in FIG. 1. The cover is used, among other things, to seal vane cells 5, 6, 7, 8 formed between rotor 2 and stator 3, and generally has a locking receptacle, in the illustrated case two locking receptacles, not illustrated in the figures. Locking pins 11, 12 are situated in recesses 13, 14, respectively, formed in rotor 2, and are accommodated in such a way that they are displaceable in the direction of rotation axis 4. When they are moved out from rotor 2 in the direction of cover 10 (out of the plane of the drawing in FIG. 1) in the so-called locking position, locking pins 11, 12 may engage with the locking receptacles formed in each case at that location, thus preventing rotation of rotor 2 relative to cover 10, and thus relative to stator 3 to which cover 10 is fixed.

(13) As shown in FIG. 1, a stator segment 15, 16, 17, 18 is formed in each case between two adjacent vane cells 5, 6, 7, 8. A fastening hole 19, 20, 21, 22 is formed in each stator segment 15, 16, 17, 18, respectively. Rotor 2 includes four rotor vanes 23, 24, 25, 26. The cover is fixed to stator 3 via fastening elements, for example attached screws, which engage with fastening holes 19, 20, 21, 22. Each rotor vane 23, 24, 25, 26 divides one vane cell into subvane cells.

(14) An essentially ring-shaped hydraulic channel or C channel, referred to below as a ring channel 27, is formed in the front surface of rotor 2 on the cover side. A hydraulic medium line 28 via which hydraulic medium, generally oil, is supplied from a hydraulic tank or a hydraulic pump to ring channel 27 via the central screw opens into the ring channel. Hydraulic line 28 is also used for discharging hydraulic medium from ring channel 27 when the conveying direction of the hydraulic pump is reversed, or the central screw (as a switch valve) is appropriately adjusted.

(15) In the area of each rotor vane 23, 24, 25, 26, ring channel 27 is provided with a radially outwardly directed branch 29, 30, 31, 32 which leads to a discharge valve 33, 34, 35, 36, respectively. Discharge valves 33, 34, 35, 36 are situated in corresponding discharge channels 37, 38, 39, 40 formed in rotor 2, which are each fluidically connected to corresponding branch 29, 30, 31, 32.

(16) In the area of locking pins 11, 12, ring channel 27 also has widened areas, so that these are acted on by the pressure of the hydraulic medium in ring channel 27. The locking pins are arbitrarily pretensioned, for example mechanically, in the direction of the cover, i.e., out of the plane of the drawing in FIG. 1, with the aid of a spring, not illustrated, or hydraulically. If a relatively high pressure acts in ring channel 27, for example with the engine switched on, locking pins 11, 12 are pushed away from cover 10 by this pressure, against their pretension (into the plane of the drawing in FIG. 1), into their respective recess 13, 14 in rotor 2. When the pressure present in ring channel 27 drops below a predetermined value, for example due to switching off the engine and a resulting outflow of hydraulic medium from ring channel 27 via hydraulic medium line 28, with the aid of the hydraulic pump or the central screw, locking pins 11, 12 due to their pretension are moved out of the particular recess 13, 14 in the direction of cover 10 and the locking receptacles formed therein, and engage with the locking receptacles and lock rotor 2 with respect to cover 10 which is fixed to stator 3.

(17) Discharge valve 34 is illustrated in cross section in various functional positions by way of example for all mentioned discharge valves in FIGS. 4, 5, and 6. The location of the section is denoted by reference character IV-IV in FIG. 1. The following description references only valve 34, but correspondingly applies for remaining discharge valves 33, 35, 36 and the functional elements which cooperate with them in each case.

(18) Discharge valve 34 is situated in discharge channel 38, and includes a cartridge 41 and a valve body 42, also referred to as a hollow pin (see FIGS. 2 and 3). Cartridge 41 has an essentially cylindrical design, and includes a seating section 43 as well as an end section 44 having a smaller diameter than seating section 43. Three continuous flow recesses 45 situated in succession in the circumferential direction and passing through in the direction of discharge channel 38 are introduced into seating section 43. Front surface 46 of the cartridge facing away from seating section 43 is implemented as a sealing surface, and forms a valve seat on which valve body 42 may come to rest in a sealing manner.

(19) Valve body 42 has an essentially hollow cylindrical design with a central through hole 47 and two sliding bearing sections 48, 49. A circumferential groove 50 is introduced between sliding bearing sections 48, 49, and opens or closes an opening or transverse borehole (not illustrated in the figures) formed in rotor 2, depending on the position of valve body 42. Valve body 42 may take on a locking function if necessary. The sectional illustrations in FIGS. 4, 5, and 6 clearly show a central hole 51 which completely passes through valve body 42. On the side facing away from cartridge 41, valve body 42 includes a diaphragm 52 having an opening cross section that is smaller than hole 51. The function of diaphragm 52 is provided in the description of FIGS. 4, 5, and 6.

(20) Cartridge 41 and valve body 42 are axially situated in succession in discharge channel 38. With the aid of its seating section 42, cartridge 41 is pressed/guided into discharge channel 38. With the aid of its sliding bearing sections 48, 49, valve body 42 is displaceably supported in discharge channel 38 in the longitudinal direction of the discharge channel, and is pretensioned with respect to cartridge 41 in the direction of cover 10 (to the right in FIGS. 4, 5, and 6) with the aid of a compression spring 53. A discharge passage 55 to a hydraulic tank or the like is situated on the left side of discharge valve 34, as shown in FIGS. 4, 5, and 6. Ring channel 27 is shown on the right side of discharge valve 34 in FIGS. 4, 5, and 6. Front surface 54 of valve body 42 at the left in FIGS. 2, 3, and 4 is designed as a sealing surface which may come into sealing contact with front surface 46 of cartridge 41.

(21) The function of discharge valve 34 is explained below by way of example for all discharge valves 33, 34, 35, 36 with reference to FIGS. 4, 5, 6, and 7, the forces acting on the valve body being schematically illustrated in FIG. 7. FIG. 4 depicts the function of discharge valve 34 in the closed state. The side of valve body 42 opposite from sealing surface 54 is acted on by hydraulic medium via ring channel 27. In the illustration in FIG. 4, the hydraulic pressure acts on valve body 42 from the right side. The pretension force exerted by spring 53 on valve body 42 acts on the opposite side (left side). Hydraulic force F.sub.hydr acting on valve body 42 due to the oil pressure in channel 27 is greater than pretension force F.sub.Fe of spring 53, so that valve body 42 is pressed against cartridge 41 (to the left in FIG. 4), where it strikes against valve seat 46 and comes to rest on sealing surfaces 46 and 54 in a sealing manner. Ring channel 27 is thus separated from the tank via sealing surfaces 46 and 54 between valve body 42 and cartridge 41.

(22) FIG. 5 depicts the function of discharge valve 34 during opening or in the open state. When ring channel 27 is switched to the tank via the central valve, i.e., a flow connection from ring channel 27 to the tank via hydraulic medium line 28 is established, the pressure in ring channel 27 drops. If the pressure drops below a predetermined limiting value, hydraulic force F.sub.hydr becomes smaller than elastic force F.sub.Fe due to the lower pressure. As a result, valve body 42 is moved against the pressure in ring channel 27 (to the right in FIG. 5). A flow path is thus opened in discharge valve 34 which leads from branch 30 of ring channel 27 through diaphragm 52 and central hole 51, along the outside of end section 44, through flow recesses 45 of cartridge 41 to discharge passage 55. An additional connection from ring channel 27 to the tank is thus opened, through which the hydraulic medium may flow through the hollow valve body to the tank. Due to the provision according to the present invention of multiple additional discharge valves 33, 34, 35, 36, the pressure drop in ring channel 27 takes place very quickly, so that the pressure acting on locking pins 11, 12 is reduced very quickly, and the locking pins, due to the pretension acting on them, may arrive at the position in which rotor 2 is locked with the cover, at the required high speed.

(23) FIG. 6 depicts the function of discharge valve 34 during the closing operation. A defined volume flow of hydraulic medium in ring channel 27 is provided by an engine oil pump, not illustrated. This volume flow initially passes through open discharge valve 34 via the above-described flow path, back to the tank. Due to diaphragm 52, as a result of the volume flow a pressure P.sub.2 builds up in front of the diaphragm (indicated in FIG. 7). Pressure P.sub.2 is a function of the volume flow. The higher the volume flow passing through diaphragm 52, the greater is pressure P.sub.2.

(24) Diaphragm 52 throttles the volume flow, so that pressure P.sub.1 (indicated in FIG. 7) behind diaphragm 52 is always less than pressure P.sub.2. Consequently, a resultant pressure force F.sub.hydr which is directed opposite the pretension force of spring 53 acts on valve body 42. When there is sufficient volume flow, resultant pressure force F.sub.hydr is greater than pretension force F.sub.Fe of spring 53, so that valve body 42 moves against the elastic force and strikes against cartridge 41. As a result, discharge channel 38 and thus the connection from ring channel 27 to the tank are closed. A higher pressure builds up in flow channel 27 which pushes locking pins 11, 12 out of the respective locking receptacle of cover 10 in the direction of rotor 2, thus unlocking the camshaft adjuster.

LIST OF REFERENCE NUMERALS

(25) 1 camshaft adjuster 2 rotor 3 stator 4 rotation axis/longitudinal axis 5-8 vane cell 9 central through opening 10 cover 11 locking pin 12 locking pin 13 recess 14 recess 15-18 stator segment 19-22 fastening hole 23-26 rotor vane 27 ring channel 28 hydraulic line 29-32 branch 33-36 discharge valve 37-40 discharge channel 41 cartridge 42 valve body 43 seating section 44 end section 45 flow recesses 46 front surface 47 central through hole 48 sliding bearing section 49 sliding bearing section 50 groove 51 central hole 52 diaphragm 53 compression spring 54 sealing surface 55 tank channel P.sub.1 pressure behind the diaphragm P.sub.2 pressure in front of the diaphragm