Multi-locking of a camshaft adjuster, and method for operating a camshaft adjuster

Abstract

A hydraulic vane-type camshaft adjuster, having a stator and a rotor arranged therein such that the rotor can rotate during control mode, wherein the rotor and the stator form at least two working chambers and are separated by a vane. A locking pin immobilizes the rotor in a rotationally fixed manner in relation to the stator wherein the locking pin is connected to an active accumulator, which deflects the pin if required. The active accumulator is arranged below a rotation axis on a camshaft. A method is also provided.

Claims

1. A hydraulic camshaft adjuster for a camshaft comprising: a stator; a rotor situated rotatably in the stator during controlled operation, the rotor and the stator forming at least two working chambers situated between the rotor and the stator and separated by a vane fixed to the rotor, the working chambers fillable with hydraulic medium from a hydraulic medium supply device; an active pressure accumulator; a first locking link and a second locking link, the first locking link being connected to the active pressure accumulator, the second locking link being separate from and circumferentially offset from the first locking link; and at least one locking pin, the locking pin in a locking state fixing the rotor in a rotatably fixed manner with respect to the stator, the locking pin being movable between the first locking link and the second locking link to lock the rotor at two different rotational positions, the locking pin being connected to the active pressure accumulator in the first locking link, the active pressure accumulator deflecting the locking pin as necessary in the first locking link, the active pressure accumulator configured for being situated below a rotation axis of the rotor, the active pressure accumulator being situated outside of the stator and rotor.

2. The hydraulic camshaft adjuster as recited in claim 1 wherein the active pressure accumulator includes a storage space for the hydraulic medium, the hydraulic medium being transferable from the storage space via a pressure medium line into the interior of the rotor.

3. The hydraulic camshaft adjuster as recited in claim 2 wherein the storage space has a volume V.sub.1 greater than a volume V.sub.line of the line section from the outlet of the storage space to the working chambers plus the volume V.sub.VCP chamber of the working chambers.

4. The hydraulic camshaft adjuster as recited in claim 2 wherein an outlet of the storage space is situated below an outlet of the pressure medium line.

5. The hydraulic camshaft adjuster as recited in claim 1 wherein the active pressure accumulator discharges hydraulic medium based on a control signal.

6. The hydraulic camshaft adjuster as recited in claim 1 further comprising a central valve inserted into the rotor, hydraulic medium of the active pressure accumulator suppliable to the working chambers or to the first link, which is designed for accommodating the locking pin via the central valve.

7. The hydraulic camshaft adjuster as recited in claim 1 wherein the at least one locking pin includes two locking pins retractable into the first link, or one of the locking pins is retractably supported in the second link.

8. The hydraulic camshaft adjuster as recited in claim 1 wherein a 5/5-way valve, or a 4/3-way valve and a 3/2-way valve, are inserted between the working chambers and the active pressure accumulator.

9. A method for locking a rotor of a hydraulic camshaft adjuster relative to a stator of the camshaft adjuster, the method comprising: locking the rotor being with respect to the stator in a center position and also in an advance position or retard position via at least one locking pin, a first locking link and a second locking link, a hydraulic medium of an active pressure accumulator separate from a hydraulic medium supply device provided for filling working chambers between the rotor and the stator and being utilized for influencing a rotary motion of the rotor, the active pressure accumulator being situated outside of the stator and rotor, the first locking link being connected to the active pressure accumulator, the second locking link being separate from and circumferentially offset from the first locking link, the locking pin being movable between the first locking link and the second locking link to lock the rotor in the center position and also in the advance position or retard position, the locking pin being connected to the active pressure accumulator in the first locking link, the active pressure accumulator deflecting the locking pin as necessary in the first locking link.

10. The method as recited in claim 9 wherein the hydraulic medium of the active pressure accumulator is utilized for influencing a longitudinal motion of the locking pin, or the hydraulic medium of the active pressure accumulator is utilized for preventing the locking pin or multiple locking pins from retracting into the first link, the first link being a center locking link.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is explained in greater detail below, also with the aid of drawings in which various exemplary embodiments are illustrated.

(2) FIG. 1 shows the arrangement of an active pressure accumulator in a hydraulic camshaft adjuster according to the present invention, in a longitudinal sectional view;

(3) FIG. 2 shows the interconnection of a 5/5-way valve which includes two working chambers, which form a pressure chamber that is divided by a vane;

(4) FIG. 3 shows the interconnection from FIG. 2, but with the vane arrived in a retard position;

(5) FIG. 4 shows a volume flow/electrical control current diagram on which the control of the 5/5-way valve, as used in the exemplary embodiment according to FIG. 2, is based;

(6) FIG. 5 shows a perspective illustration of a central valve used in the hydraulic camshaft adjuster according to the present invention;

(7) FIG. 6 shows a hydraulic medium flow rate/electrical control current diagram, similar to the diagram from FIG. 4, which is used for supplying the central valve from FIG. 5 with oil;

(8) FIG. 7 shows an overall diagram made up of three partial diagrams for a center locking strategy when the internal combustion engine is stopped, at which point in time locking in the retard position is achieved, and in which a departure is made from the retard locking position for an extended period of time after the internal combustion engine has cooled down, and a center locking position is sought when the engine is restarted;

(9) FIG. 8 shows an illustration, comparable to FIG. 7, of an overall diagram, but with the engine not cooled down and a customary start/stop-restart situation present, whereby a center locking position that is achieved when the internal combustion engine is switched off is triggered, and a retard locking position is preselected for starting the engine;

(10) FIGS. 9 through 12 show the transition from an advance position into a retard locking position, with passing into a center locking position when the engine is started; and

(11) FIGS. 13 through 16 show the sequence of switching off the engine in an advance position, and transferring the rotor into a center locking position for restarting the internal combustion engine.

DETAILED DESCRIPTION

(12) The figures are strictly schematic in nature, and are used only for understanding of the present invention. Identical elements are provided with the same reference numerals.

(13) FIG. 1 illustrates a first specific embodiment of a hydraulic camshaft adjuster 1 according to the present invention. The camshaft adjuster is a vane-type hydraulic camshaft adjuster, i.e., includes a stator 2 and a rotor 3, between which vanes or pressure chambers 4 are formed. These pressure chambers 4 are not discernible in FIG. 1. However, one of pressure chambers 4 is discernible in FIGS. 2 and 3. It is also apparent in FIGS. 2 and 3 that each pressure chamber is divided by a vane 5 which is mounted on rotor 3 in a rotatably fixed manner, thus forming working chambers 6. One working chamber 6 is referred to as retard working chamber A, and the other is referred to as advance working chamber B. Working chamber 6 may also be referred to as a working space.

(14) Returning to FIG. 1, a central valve 7 is screwed into rotor 3. Central valve 7 is controlled via a central magnet 8, namely, a proportional magnet. Oil supply channels for working chambers 6 are opened by the control system. Oil may then be transferred into working chambers 6, or oil may be removed from working chambers 6, by a pump element, not illustrated, of a hydraulic medium supply device (not illustrated), such as an oil pump. For this purpose, a receiving element such as a tank or an oil pan is also connected.

(15) However, an active pressure accumulator 9 is also provided here. Pressure accumulator 9 is situated below a camshaft rotation axis 10. Camshaft rotation axis 10 may also be referred to as rotation axis for short.

(16) Active pressure accumulator 9 includes a piston 11 which is pretensioned via a spring 12. Spring 12 pretensions piston 11 in the direction of a storage space 13. Storage space 13 has a volume V.sub.1. An actuator 14 is provided for unlocking or locking active pressure accumulator 9. Actuator 14 may also be designed as a switching valve. It may also be designed as a solenoid valve. When energized, actuator 14 effectuates unlocking of piston 11, which is used for compression.

(17) A camshaft 17 is provided for connection to rotor 3 in a rotatably fixed manner. A valve 19 is provided at a slide bearing point 18 in order to interrupt an oil supply from the oil pump. A pressure medium line 20 is present for connecting an outlet 21 of storage space 13 to slide bearing point 18 and allowing oil access into the interior of camshaft 17. The oil from the interior of the camshaft may then penetrate into the interior of central valve 17, and may reach working chambers A or B through inlets which are opened as necessary. The supply from oil pump P is in particular from the top (but is also possible from other directions), i.e., on the top side of camshaft 17 at the slide bearing or at slide bearing point 18, while the supply from active pressure accumulator 9 is at the bottom, at slide bearing point 18.

(18) Ventilation 22 is also provided to be able to remove air from a spring chamber 23 or to draw air back into the spring chamber when the piston presses oil from pressure accumulator 9.

(19) FIG. 2 illustrates the use of a 5/5-way valve 24. 5/5-way valve 24 includes five inlets/outlets and five positions which the valve may assume during the adjustment. The inlets/outlets lead to hydraulic medium supply device P, a tank T, working chamber A, a center locking link 31, and working chamber B. The center locking position (MLP) is illustrated in FIG. 2. A connection 25 between working chamber A and a retard locking link 26 is present. For this purpose, working chamber A has an extra opening area 27.

(20) While FIG. 2 illustrates the center locking position, FIG. 3 illustrates the retard locking position. Two locking pins 28 are present. One of the two locking pins 28 is referred to as first locking pin 29, and the other of the two locking pins 28 is referred to as second locking pin 30. In the situation in FIG. 2, both locking pins 29 and 30 are locked into a center locking link 31. In the state in FIG. 3, first locking pin 29 is locked into retard locking link 26, and second locking pin 30 is locked into center locking link 31. Thus, there is a form fit at the positions of the two links 26 and 31 with locking pins 29 and 30, respectively.

(21) FIG. 4 illustrates a flow rate/current diagram, with electric current I plotted on the horizontal axis and hydraulic medium flow rate Q plotted on the vertical axis. At the far left end of the diagram, hydraulic medium supply device P, which is a component that is separate from active pressure accumulator 9, is connected to working chamber B, whereas working chamber A is connected to the tank. At the far right edge of the diagram, hydraulic medium supply device P is connected to working chamber A, and working chamber B is connected to the tank.

(22) Five areas 1, 2, 3, 4, and 5 are discernible in the diagram, and are also illustrated in FIG. 6. A locking command/a locking instruction is present in areas 1 and 5. In segments 2 and 4, no locking is achieved, and in addition no hydraulic clamping of vane 5 is effectuated. However, the hydraulic clamping of vane 5 is forced in an area 3.

(23) These areas 1 through 5 are predefined by the switch positions of 5/5-way valve 24, as illustrated in FIG. 2.

(24) A center locking position without locking pins 29 and 30 retracted is effectuated in settings 1 and 5 of 5/5-way valve 24.

(25) Separate from 5/5-way valve 24, a 4/3-way valve in addition to a 3/2-way valve is also possible. A separate valve is thus used for supplying center locking link 31, which is designed as an elongated hole.

(26) FIG. 5 illustrates central valve 7 and openings 32 therein. The supply of working chambers A and B, of pressure medium line PP, and of tank T, and the feed from hydraulic medium supply device P, are also indicated. Volume flow rate curve 33 for hydraulic fluid through the working chambers is denoted by reference numeral 33, whereas the (volume) flow rate curve through channel PP to pressure medium line 20 is provided with reference numeral 34. The activation of locking pins 28 is thus predefinable as a function of flow rate curve 34.

(27) The chronological sequence of the crankshaft speed (uppermost part of the diagram), the pulse duty factor/pulse width modulation state (PWM for short) in the middle part, and the angular position of the camshaft adjuster (phaser position) in the lower area are plotted on the horizontal axis in FIG. 7. The crankshaft speed is depicted by line 35. The pulse duty factor is depicted by line 36. The locking state is depicted by line 37.

(28) A state in the locking of a center position MLP, a retard position (Ret.), i.e., late position, and an advance position (Adv.), i.e., early position, is possible. At point in time (t), at which the ignition key is turned and the internal combustion engine is switched off, namely, point in time 38, the rotational speed of the crankshaft changes. The internal combustion engine is at a standstill at point in time 39. Current flow is no longer present, i.e., electric current no longer flows, at point in time 40. Approximately 10 minutes or even eight or more hours after point in time 40, the ignition key is turned at point in time 41, and at the same time, oil stored in active pressure accumulator 9 is conveyed into central valve 7. The unlocking strategy, as already provided, is run through at point in time 42. The center locking position is reached at point in time 43, since in this position the two locking pins 29 and 30 are in locking engagement at this point in time.

(29) Only at point in time 44 does ignition take place. This is the point in time of the so-called first ignition.

(30) FIG. 8 illustrates another state, namely, a state in which less than approximately eight hours time has elapsed between points in time 39 and 41, at least enough time that the motor or the internal combustion engine has not yet cooled down, and at least has not cooled below 100 C. or 80 C. This is the state of normal start/stop operation.

(31) FIG. 9 shows an active pressure accumulator 9, which is connected via pressure medium line 20 (PP) to center locking link 31 in a locking cover 45. Center locking link 31 is on the other side of a sealing cover 46, viewed from rotor 3. Locking pins 29 and 30 are inserted into rotor 3 with pretension via springs 47 and 48. Vane 5 is in its advance position, so that working chamber A has a maximum size. A switching valve 49 is connected to hydraulic medium supply device P (port C). However, switching valve 49 is in such a position that inflow from P to active pressure accumulator 9 and also to pressure medium line 20 is interrupted. A control unit 50 is used in this regard.

(32) In FIG. 9, rotor 3 is in an advance position prior to the engine start-up. In FIG. 10, the rotor is already in a center position, oil pressure being provided by active pressure accumulator 9 via pressure medium line 20 in link 31.

(33) While pressure accumulator 9 is not switched on (i.e., is off) in FIG. 9, in the state in FIG. 10 it is switched on (i.e., on).

(34) In the exemplary embodiment of the chronological state according to FIG. 11, rotor 3 has already arrived at its retard position. Locking link 31 has thus been overrun. FIG. 12 illustrates the state in which locking pin 29 is now in locking engagement with locking link 26.

(35) In a second variant, rotor 3 is illustrated in FIG. 13 in its advance position prior to the engine start-up. The rotor is once again situated between locking cover 45 and sealing cover 46. Active pressure accumulator 9 is not yet connected via pressure medium line 20 (PP), and is thus still off. Rotor 3 is between its advance position and the center position in the state illustrated in FIG. 14. However, first pin 29 has already retracted into locking link 31, and makes locking engagement there. Active pressure accumulator 9 is still off. However, as likewise illustrated in FIG. 13, switching valve 49 is not connected to port C, i.e., pump P. FIG. 15 illustrates the chronologically subsequent state in which second locking pin 30 now also retracts into locking link 31.

(36) In FIG. 16, second locking pin 30 is now also lockingly retracted into link 31, so that rotor 3 is now locked in its center position by locking pins 28. Switching valve 49 may also be connected through when, instead of a 5/5-way valve in position 1, the variant of the 4/3-way valve and 3/2-way valve use, already disclosed, is also desired.

LIST OF REFERENCE NUMERALS

(37) 1 camshaft adjuster 2 stator 3 rotor 4 vane/pressure chamber 5 vane 6 working chamber (retard working chamber A/advance working chamber B) 7 central valve 8 central magnet 9 active pressure accumulator 10 camshaft rotation axis 11 piston 12 spring 13 storage space 14 actuator 17 camshaft 18 slide bearing point 19 valve 20 pressure medium line 21 outlet of storage space 22 ventilation 23 spring chamber 24 5/5-way valve 25 connection 26 retard locking link 27 opening area 28 locking pin 29 first locking pin 30 second locking pin 31 center locking link 32 opening 33 volume flow rate curve 34 flow rate curve 35 crankshaft speed 36 pulse duty factor 37 locking state 38 ignition off 39 engine off 40 current off 41 ignition on 42 unlocking strategy 43 MLP reached 44 ignition 45 locking cover 46 sealing cover 47 spring 48 spring 49 switching valve 50 control unit