Camshaft adjuster with reset function

Abstract

The present invention relates to a hydraulic camshaft adjuster (1) having a stator (2), a rotor (3) rotatable relative to the stator (2) within a limited angular range, and a hydraulic supply device (4) having two working channels (5, 6) and a switching valve (7), wherein the two working channels (5, 6) for adjusting the rotor (3) relative to the stator (2) in two opposite directions of action can be connected to a pump (10) for pressurization or to a reservoir (11) for depressurization according to the switching position (8, 9) of the switching valve (7), wherein the hydraulic supply device (4) has a return pump (12) actuated by shifting the switching valve (7) between the switching positions (8, 9) of the switching valve, and by actuation of the return pump, one of the two working channels (6) can be pressurized to return the rotor (3) to a predetermined position.

Description

Technical Field

[0001] This invention relates to a hydraulic camshaft adjuster for adjusting the phase position of a camshaft relative to a crankshaft in a motor vehicle transmission system. The camshaft adjuster comprises: a stator, particularly a stator rotatably coupled to the crankshaft; a rotor, particularly a rotor rotatably coupled to the crankshaft, capable of rotating relative to the stator within a limited angular range; and a hydraulic supply device having two working channels and a (first) switching valve, wherein the two working channels for adjusting the rotor relative to the stator in two opposite directions of motion can be connected to a pump for pressurization or to a reservoir for depressurization, depending on the switching position of the switching valve. Hydraulic camshaft adjusters are known, for example, from JP H11-13 429A or DE 196 04865A1. Background Technology

[0002] The hydraulic camshaft adjuster must have a rest position in the depressurized state, which is actively achieved under depressurization conditions. For example, typically in the depressurized state, the rotor and stator are adjusted relative to each other to a defined position, such as a center position, from which the vehicle can be started. Returning to the rest position is also known as a fail-safe function.

[0003] Known hydraulic camshaft adjusters typically have an integrated spring mechanism for returning the rotor relative to the stator to a defined / end position. The (mechanical) restoring force of this integrated spring mechanism sets the rotor to the defined position under decompression.

[0004] However, the existing technology has several drawbacks. On the one hand, this spring mechanism introduces additional cost and weight to the spring mechanism itself and the components housing it. On the other hand, the arrangement of the spring mechanism requires axial and radial installation space, causing its integration to offset the requirement for the camshaft adjuster to be as compact as possible, especially axially narrow, and to avoid collision with the central magnet. Furthermore, this spring mechanism carries the risk of spring failure during operation due to material failure, and the spring tension acting on the rotor—which operates in one of the two adjustment directions—exerts a reaction torque on the rotor, potentially leading to different adjustment speeds in one or the other adjustment direction. Summary of the Invention

[0005] Therefore, the object of the present invention is to avoid or at least mitigate the disadvantages of the prior art and to provide a camshaft adjuster that implements the above-mentioned return to a defined position / rest position (fail-safe function), and the camshaft adjuster is constructed in a particularly cost-effective and weight-reducing manner without limiting the function of the camshaft adjuster.

[0006] The object of the invention is achieved by a camshaft adjuster having the features of claim 1. Other advantageous improvements are claimed in the dependent claims.

[0007] Therefore, the object of the present invention is achieved in the universal camshaft adjuster according to the invention, since the hydraulic supply device has a return pump that can be actuated by shifting the switching valve between switching positions, and by actuation of the return pump, one of the two working channels can be pressurized to return the rotor to a predetermined position.

[0008] This means that the objective of the invention is achieved, for example, by a hydraulic camshaft adjuster of the blade unit type, having a first working chamber formed between the stator and rotor and a second working chamber formed between the stator and rotor. The first working chamber can be supplied with hydraulic fluid / hydraulic medium / oil via a first working channel for adjusting the rotor relative to the stator in one direction of action, and the second working chamber can be supplied with hydraulic fluid / hydraulic medium / oil via a second working channel for adjusting the rotor relative to the stator in another direction of action. The pressurization of the working chambers is controlled by a switching valve. In normal adjustment mode, one working chamber is always connected to a pump for pressurization, while the other working chamber is connected to a reservoir for depressurization. According to the invention, the switching valve is designed to function as a pump (i.e., forming a return pump) because hydraulic fluid / oil is drawn from an unpressurized reservoir and supplied to one working chamber by means of the switching valve's cyclic switching (and therefore by the longitudinal movement of the switching valve (i.e., the switching adjustment movement)). In other words, supplying hydraulic fluid to one working chamber causes the camshaft adjuster to return to a predetermined position in a depressurized state, thus achieving an electro-hydraulic return function.

[0009] According to a preferred embodiment, the hydraulic supply device may have a second switching valve that, in a first switching position, connects one of the two working channels (e.g., the second working channel) to a return pump, and in the second switching position, connects both working channels to a pump or a reservoir depending on the switching position of the (first) switching valve. This means that in the second switching position, normal adjustment operations are performed, in which the working channels are pressurized and depressurized in a switchable manner, and in the first switching position, a return function is implemented, in which fluid is supplied to one working chamber (e.g., the second working chamber) via the return pump, and fluid is discharged from the other working chamber (e.g., the first working chamber) until a predetermined position is reached. The advantage of this is that it allows switching between normal and return functions.

[0010] According to another improvement of the preferred embodiment, the second switching valve can be designed for pilot control in a (oil / fluid) pressure-dependent manner, wherein the second switching valve is in a first switching position when the pump is under pressure reduction and in a second switching position when pressure is established at the pump. Specifically, the second switching valve is actuated via a control line connected to the pump, by means of which, when there is no pressure in the control line, the second switching valve is adjusted to its unactuated first switching position by the restoring force of a spring, and when pressure is present in the control line, the second switching valve is adjusted to its actuated second switching position against the restoring force of the spring. This ensures that during normal operation, when pressure is established at the pump, the second switching valve is in the second switching position, and under pressure reduction conditions, the second switching valve automatically returns to the first switching position. In this way, a particularly simple method of controlling the second switching valve can be provided.

[0011] According to another improvement of the preferred embodiment, the hydraulic supply device may have a neutral line that connects the return pump to the reservoir in the second switching position of the second switching valve, thereby forming an open central section separate from the working channel. This has the advantage that the regulating function is not affected by the return pump during normal operation.

[0012] According to another improvement of the preferred embodiment, the other working channel of the two working channels (e.g., the first working channel) can be connected to the first pipeline via a throttle valve in the first switching position of the second switching valve, and preferably connected to the second pipeline without throttling, wherein the first and second pipelines connect the same working channel (e.g., the first working channel) to the pump or to the reservoir depending on the switching position of the (first) switching valve. By means of throttling, a sufficiently high differential pressure can be provided to the second switching valve.

[0013] According to another improvement of the preferred embodiment, the second switching valve can be designed as a sleeve structure arranged coaxially around the switching valve. This has the advantage that the second switching valve can be integrated into an existing camshaft adjuster in a cost-effective and space-saving manner.

[0014] According to a preferred embodiment, the pump piston of the return pump can be integrally formed from the switching valve armature / switching valve slide of the (first) switching valve. According to an alternative preferred embodiment, the pump piston of the return pump can be designed to be connected in series with the switching valve armature / switching valve slide of the (first) switching valve. This means that the longitudinal movement of the switching valve armature is directly coupled to the pump piston, such that the cyclic switching of the (first) switching valve actuates the return pump, and thus achieves the return of the rotor. This means that the return spring previously used to return the rotor to a predetermined position can be replaced by existing components.

[0015] According to a preferred embodiment, the return pump can be connected via a suction line to an unpressurized reservoir, wherein the reservoir is formed in a cavity within the camshaft adjuster. This has the advantage that the suction line can be designed, for example, to be relatively short.

[0016] According to a preferred embodiment, the return pump can be designed such that its volumetric flow rate is greater than 1.2 l / min. In this way, the volumetric flow rate required to return the rotor can be provided.

[0017] In other words, in the camshaft adjuster according to the invention, the return function is not achieved by means of a spring mechanism as in known camshaft adjusters, but by means of a component or subsystem already present in the camshaft adjuster system. Therefore, this camshaft adjuster differs from known camshaft adjusters in that the return is performed by means of the cyclic switching of a modified electro-hydraulic switching valve rather than by a spring drive, wherein the modification includes an additional pumping function during the longitudinal movement of the switching valve armature. The pumping function can be implemented, for example, by a design of series connection of the pump piston and the switching valve armature, or preferably an integral design. Alternatively, other pump concepts, such as a diaphragm pump, are also conceivable. In the first operating state, the camshaft adjuster is in a depressurized state, for example, when the engine is stopped, because the lubricating oil pump cannot establish any supply pressure. By means of the circulation of the switching valve, as initiated by the ECU (engine control unit), oil is drawn into an unpressurized reservoir, such as a chamber in the camshaft adjuster, and supplied to the camshaft adjuster via pressure lines and a directional valve piloted in a manner related to engine oil pressure, so as to move the camshaft adjuster to a predetermined / preferred position. The directional valve can preferably be a sleeve structure arranged coaxially around the switching valve, which is axially displaced by engine oil pressure against a return spring, thereby releasing / closing the desired oil path accordingly. In a second operating state, such as after engine start or when engine oil pressure is present, the standard adjustment function of the camshaft adjuster is provided. Additionally, a slight throttling of the oil flow may be necessary to provide sufficient differential pressure for the pilot-controlled directional valve. Furthermore, an open central section can be provided for the pump function, preventing any influence on the switching behavior of the electro-hydraulic switching valve in this operating state. Attached Figure Description

[0018] The invention will now be described with reference to the accompanying drawings. In the drawings:

[0019] Figure 1 A schematic diagram of the camshaft adjuster according to the present invention in a first operating state is shown, and

[0020] Figure 2 A schematic diagram of the camshaft adjuster according to the present invention in a second operating state is shown. Detailed Implementation

[0021] The accompanying drawings are merely illustrative in nature and are intended only to understand the invention. Identical elements have the same reference numerals. Features of the various embodiments are interchangeable.

[0022] Figure 1 and Figure 2 The hydraulic camshaft adjuster 1 according to the invention is shown in two different operating modes. The camshaft adjuster 1 is used to adjust the phase position of the camshaft relative to the crankshaft in a motor vehicle transmission system. The camshaft adjuster 1 has a stator 2 and a rotor 3, the rotor being rotatable / adjustable relative to the stator 2 within a limited angular range. The stator 2 is rotatably coupled to the crankshaft, and the rotor 3 is rotatably coupled to the camshaft. In the figures, the stator 2 and rotor 3 are shown by way of example only as double-acting hydraulic cylinders, wherein adjustment of the hydraulic cylinder in one direction represents rotation of the rotor 3 in a first acting direction, and adjustment of the hydraulic cylinder in another direction represents rotation of the rotor 3 in a second acting direction opposite to the first acting direction.

[0023] To adjust the rotor 3 relative to the stator 2, the camshaft adjuster 1 has a hydraulic supply device 4, shown in the accompanying drawings as a hydraulic circuit diagram. The hydraulic supply device 4 has a first working channel 5 connected to a first working chamber formed between the rotor 3 and the stator 2, and a second working channel connected to a second working chamber formed between the rotor 3 and the stator 2. When pressure is applied to the first working channel 5 (or the first working chamber) (and pressure is released from the second working channel 6), the rotor 3 is adjusted in a first direction of action (right side in the drawings). When pressure is applied to the second working channel 6 (or the second working chamber) (and pressure is released from the first working channel 5), the rotor 3 is adjusted in a second direction of action (left side in the drawings).

[0024] The hydraulic supply unit 4 has a switching valve 7 that is adjustable between a first switching position 8 and a second switching position 9. In the illustrated embodiment, the switching valve 7 is designed as a 2 / 2-way valve. In the first switching position 8, the first working channel 5 can be connected to or connected to the pump 10 for pressurization, and the second working channel 6 can be connected to or connected to the tank / reservoir 11 for depressurization. In the second switching position 9, the first working channel 5 can be connected to or connected to the tank / reservoir 11 for depressurization, and the second working channel 6 can be connected to or connected to the pump 10 for pressurization. The switching valve 7 is designed as an electro-hydraulic valve that can be actuated / switched by a control unit (ECU) not shown.

[0025] According to the invention, the hydraulic supply device 4 has a return pump 12. The return pump 12 can be actuated / operated by shifting the switching valve 7 between switching positions 8 and 9. This means that additional pumping function is provided during the longitudinal movement of the switching valve 7. By actuating the return pump 12, one of the two working channels 5 and 6, or the second working channel 6 in the illustrated embodiment, can be pressurized to return the rotor 3 to a predetermined (rest) position.

[0026] In the illustrated embodiment, the return pump 12 has a pump piston 14 that can be displaced within the pump chamber 13. This displacement allows hydraulic fluid to be drawn from the tank / reservoir 11 via the suction line 15 and introduced into the second working channel 6 via the pressure line 16. The pump piston 14 is moved by the longitudinal / switching motion of the switching valve 7. The pump piston 14 can, for example, reduce the size of the pressure chamber 18 connected to the suction line 15 and / or the pressure line 16 by resisting the restoring force of the spring 17. A check valve 19 can be arranged in the suction line 15 to prevent reverse flow from the pressure chamber 18 through the suction line 15 into the reservoir 11. A check valve 20 can also be arranged in the pressure line 16 to prevent reverse flow from the second working channel 6 through the pressure line 16 into the pressure chamber 18.

[0027] Preferably, the pump piston 14 can be integrally formed from the switching valve armature / switching valve slide of the switching valve 7. Alternatively, the pump piston 14 can be designed to be connected in series with the switching valve armature / switching valve slide of the switching valve 7. Further alternatively, the return pump 12 can be designed as a diaphragm pump, etc., even if not shown.

[0028] Between the working channels 5 and 6 and the switching valve 7 or return pump 12, another switching valve 21 in the form of a directional valve is arranged. This switching valve can be adjusted between a first switching position 22 and a second switching position 23. The switching valve 21 is pilot-controlled according to the oil pressure of pump 10. This means that the switching valve 21 is actuated via the control line 24 connected to pump 10, and the switching valve is in the unacted first switching position 22 when pump 10 is in a depressurized state (see...). Figure 1 And when pump 10 is pressurized, it is in the actuated second switching position 23 against the restoring force of spring 25 (see...). Figure 2 ).

[0029] In the first switching position 22, the first working channel 5 is connected to pipeline 26, which is connected to pump 10 in the first switching position 8 of switching valve 7, and the first working channel is connected to pipeline 27, which is connected to reservoir 11 in the first switching position of switching valve 7. In the first switching position 22, the first working channel 5 is connected to pipeline 26 via throttle valve 28, which restricts fluid flow. The second working channel 6 is connected to pressure line 16 in the first switching position 22. By means of the start-up cycle of switching valve 7, return pump 12 draws fluid from reservoir 11 and delivers the fluid to the second working chamber via pressure line 16 and switching valve 21, thereby adjusting rotor 3 to a predetermined (stationary) position / default position. Fluid can be discharged from the first working chamber via pipeline 27.

[0030] In the second switching position 23, the first working channel 5 is connected to pipeline 26, which connects to pump 10 in the first switching position 8 of switching valve 7 and to reservoir 11 in the second switching position 9 of switching valve 7. In the second switching position 22, the second working channel 6 is connected to pipeline 27, which connects to reservoir 11 in the first switching position 8 of switching valve 7 and to pump 10 in the second switching position 9 of switching valve 7. In the second switching position 23, pressure pipeline 16 is connected to reservoir 11 via neutral pipeline 29. Therefore, the return pump 12 has an open central portion in the second switching position 23, so that the switching behavior of switching valve 7 is not affected.

[0031] List of reference numerals

[0032] 1 Camshaft Adjuster

[0033] 2. Stator

[0034] 3 rotors

[0035] 4. Hydraulic supply device

[0036] 5 First Working Channel

[0037] 6 Second Working Channel

[0038] 7. Switching valve

[0039] 8 First Switching Position

[0040] 9 Second switching position

[0041] 10 pumps

[0042] 11. Storage

[0043] 12 Return Pump

[0044] 13 Pump Room

[0045] 14 Pump piston

[0046] 15. Suction line

[0047] 16 Pressure lines

[0048] 17 Springs

[0049] 18 pressure chambers

[0050] 19 Check valve

[0051] 20 Check valve

[0052] 21 Second switching valve

[0053] 22 First Switch Position

[0054] 23 Second switching position

[0055] 24 Control lines

[0056] 25 springs

[0057] 26 First Pipeline

[0058] 27 Second Pipeline

[0059] 28 Throttling valve

[0060] 29 Neutral pipeline

Claims

1. Hydraulic camshaft adjuster (1) for adjusting the phase position of a camshaft relative to a crankshaft in a drive train of a motor vehicle, the camshaft adjuster having a stator (2), a rotor (3) which is rotatable relative to the stator (2) over a limited angular range, and a hydraulic supply device (4) having two working channels (5, 6) and a switching valve (7), wherein The two working channels (5, 6) for adjusting the rotor (3) relative to the stator (2) in two opposite directions can be connected to a pump (10) for pressurization or to a reservoir (11) for depressurization, depending on the switching position (8, 9) of the switching valve (7). The hydraulic supply device (4) has a return pump (12) that can be actuated by shifting the switching valve (7) between the switching positions (8, 9) of the switching valve, and by actuation of the return pump, one of the two working channels (6) can be pressurized to return the rotor (3) to a predetermined position.

2. The camshaft adjuster (1) according to claim 1, characterized in that, The hydraulic supply device (4) has a second switching valve (21) which connects one of the two working channels (6) to the return pump (12) in a first switching position (22) and connects the two working channels (5, 6) to the pump (10) or the reservoir (11) in a second switching position (23) according to the switching position (8, 9) of the switching valve (7).

3. The camshaft adjuster (1) according to claim 2, characterized in that, The second switching valve (21) is designed to be pilot-controlled in a pressure-dependent manner, wherein the second switching valve (21) is in the first switching position (22) when the pump (10) is under pressure reduction and is in the second switching position (23) when pressure is built up at the pump (10).

4. The camshaft adjuster according to claim 2 or 3, characterized in that, The hydraulic supply device (4) has a neutral line (29) that connects the return pump (12) to the reservoir (11) in the second switching position (23) of the second switching valve (21) to form an open central section separate from the working channels (5, 6).

5. The camshaft adjuster (1) according to any one of claims 2 to 4, characterized in that, The other working channel (5) of the two working channels is connected to the first pipeline (26) and the second pipeline (27) via a throttle valve (28) in the first switching position (22) of the second switching valve (21), wherein the first pipeline (26) and the second pipeline (27) connect the working channel (5) to the pump (10) or to the reservoir (11) according to the switching position (8, 9) of the switching valve (7).

6. The camshaft adjuster (1) according to any one of claims 2 to 5, characterized in that, The second switching valve (21) is designed as a sleeve structure arranged coaxially around the switching valve (7).

7. The camshaft adjuster (1) according to any one of claims 1 to 6, characterized in that, The pump piston (14) of the return pump (12) is integrally formed with the switching valve armature of the switching valve (7).

8. The camshaft adjuster (1) according to any one of claims 1 to 6, characterized in that, The pump piston (14) of the return pump (12) is designed to be connected in series with the switching valve armature of the switching valve (7).

9. The camshaft adjuster (1) according to any one of claims 1 to 8, characterized in that, The return pump (12) is connected via a suction line (15) to an unpressurized reservoir (11), wherein the reservoir (11) is formed in a cavity in the camshaft adjuster (1).

10. The camshaft adjuster (1) according to any one of claims 1 to 9, characterized in that, The return pump (12) is designed to have a volumetric flow rate greater than 1.2 l / min.

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