Hydraulic camshaft phaser for variable valve control of a combustion engine and method for operating a hydraulic camshaft phaser

Abstract

The disclosure relates to a hydraulic camshaft phaser for variable valve control of a combustion engine including a stator, a rotor, and a plurality of pressure chambers delimited by the stator and rotor and into which pressure medium can be introduced in order to adjust the relative rotation-angle phase position between the stator and the rotor. At least one pressure-medium outflow connection to the surroundings is provided so that, in a rotation-angle phase position for activating maximally late valve control times of the combustion engine, pressure medium flows out of at least one pressure chamber into the surroundings due to gravity during an engine standstill of the combustion engine. The pressure-medium outflow connection can be closed again by adjustment of the relative rotation-angle phase position during an engine start. The disclosure also relates to a method for operating a hydraulic camshaft phaser of this type.

Description

[0001] The invention relates to a hydraulic camshaft phaser for variable valve control of an internal combustion engine according to the type defined in more detail in the preamble of claim 1. The invention further relates to a method for operating a hydraulic camshaft phaser of this type.

[0002] From DE 10 2019 119 865 B4, a hydraulic camshaft phaser for a drive train of a motor vehicle is known, which comprises a stator and a rotor which can be rotated relative thereto, wherein working chambers are formed between the stator and the rotor, into which hydraulic fluid can be introduced in order to adjust the rotor relative to the stator.

[0003] The invention is therefore based on the object of proposing a hydraulic camshaft phaser and a method of the aforementioned type, which enable improved hydraulic camshaft phasing during an engine start of the internal combustion engine in a structurally simple manner and, in particular, avoid disturbances due to noise and vibrations.

[0004] The object is achieved by the features of claim 1 and alternatively by the features of claim 10. Further advantageous and claimed embodiments emerge from the respective dependent claims, the description, and the drawings.

[0005] Thus, a hydraulic camshaft phaser for variable valve control of an internal combustion engine is proposed, which comprises a stator and a rotor and a plurality of pressure chambers which are delimited by said stator and rotor, wherein pressure medium can be introduced into the latter in order to adjust the relative rotation-angle phase position between the stator and rotor for activating the valve control times of the internal combustion engine. At least one pressure-medium outflow connection to the surroundings is provided so that, in a rotation-angle phase position of the camshaft phaser for activating maximally late valve control times, pressure medium flows out of at least one pressure chamber into the surroundings due to gravity during an engine standstill of the combustion engine, which pressure-medium outflow connection can be closed again by adjustment of the relative rotation-angle phase position during an engine start.

[0006] By the outflow of pressure medium during an engine standstill, the damping can be significantly reduced or even completely eliminated by displacing the pressure medium from the pressure chambers when adjusting during the engine start towards earlier valve control times. This enables a very rapid adjustment of the rotation-angle phase position towards earlier valve control times even during an engine start and when the required pressure medium pressure is not available, solely due to the dynamic alternating torques of the camshaft of the internal combustion engine acting during operation and also against the frictional forces occurring during operation.

[0007] In a particularly advantageous way, starting from an engine standstill with maximally late valve control times during an engine start, a short-term decompression of the internal combustion engine can be achieved and disturbances caused by noise and vibration, i.e., noise vibration harshness (NVH) problems, can be reliably avoided.

[0008] In a particularly simple design of the invention, the pressure-medium outflow connection has at least one first pressure-medium outflow channel on the stator, which runs from the outer diameter to at least one bearing surface on the inner diameter. Preferably, at least one second pressure-medium outflow channel is arranged on the outer diameter of the rotor in such a way that, during an engine standstill, it communicates with a pressure chamber on the one hand and with the first pressure-medium outflow channel on the other hand. In this way, a direct pressure-medium outflow connection between at least one pressure chamber and the surroundings is enabled during an engine standstill.

[0009] A simple closure of the pressure-medium outflow connection during an engine start can be achieved if the first and the second pressure discharge channel are arranged in such a way that, by adjusting the relative rotation-angle phase position, the first pressure-medium outflow channel can be covered in a pressure-tight manner by the outer diameter of the rotor and the second pressure-medium outflow channel can be covered in a pressure-tight manner by the bearing surface on the inner diameter of the stator.

[0010] The pressure-medium outflow connection can be further simplified in terms of construction by designing the first pressure-medium outflow channel as a radial through-hole on the stator and the second pressure-medium outflow channel on the outer diameter of the rotor as a radial recess extending in an arc in the circumferential direction, preferably as an elbow groove.

[0011] The elbow groove can be arranged in a simple manner such that, during an engine stop, a first end in the region of the bearing surface of the stator communicates with the through-hole and a free second end extending outside the region of the bearing surface communicates with a pressure chamber.

[0012] In a design optimized with regard to engine start and pressure-medium outflow during the engine standstill, the elbow groove extends with the free second end outside the region of the bearing surface with a predetermined elbow length in the direction of the adjustment of the relative rotation-angle phase position to the engine start. Preferably, this elbow length corresponds to an adjustment of the relative rotation-angle phase position during the engine start by an angle of rotation of 1° to 2°. This means that the pressure-medium outflow connection can be interrupted or closed during an engine start by adjusting the relative rotation-angle phase position towards earlier valve control times as soon as an adjustment of 1° to 2° away from the maximally late position is reached.

[0013] By adapting the radial depth of the elbow groove on the rotor and the diameter of the radial through-hole on the stator to the usage and operating conditions of the camshaft phaser, the pressure-medium outflow connection can be further optimized in a simple manner. To optimize the desired pressure-medium outflow, the operating conditions during normal operation of the internal combustion engine, in particular the operating temperature when the engine is warm, are preferably used as a basis.

[0014] It is also advantageous if at least two pressure-medium outflow connections arranged diametrically opposite one another on the stator and / or on the rotor to the surroundings are provided so that pressure medium flows out of at least two pressure chambers arranged diametrically opposite one another on the stator and / or on the rotor into the surroundings due to gravity during an engine standstill of the combustion engine. In this way, it is possible to position the pressure-medium outflow connections in the effective direction of gravity during an engine standstill, such that one pressure-medium outflow connection is arranged at the bottom in the effective direction of gravity for draining the pressure medium and the other pressure-medium outflow connection, arranged diametrically opposite, at the top in the effective direction of gravity for ventilating the pressure chambers or for air to enter the latter during the pressure-medium outflow.

[0015] It is advantageous if at least two first pressure-medium channels arranged diametrically opposite one another on the stator in the region of the bearing surfaces are arranged in alignment as radial through-holes. Consequently, the latter can be positioned in the effective direction of gravity during an engine standstill.

[0016] Preferably, at least two first pressure-medium outflow channels arranged diametrically opposite one another in alignment on the stator in the region of the bearing surfaces and designed as radial through-holes and at least two second pressure-medium outflow channels arranged diametrically opposite one another on the rotor and designed as radial elbow grooves extending in the circumferential direction on the outer diameter are provided. The respective first and second pressure-medium outflow channels communicate in the manner described above during an engine standstill and can be closed again in the manner described above during an engine start.

[0017] In an advantageous development of the invention, at least two pairs of pressure-medium outflow connections arranged diametrically opposite one another on the stator and / or rotor to the surroundings are provided so that pressure medium flows out of at least two pairs of pressure chambers arranged diametrically opposite one another on the stator and / or on the rotor into the surroundings due to gravity during the engine standstill of the internal combustion engine. Accordingly, at least four pressure chambers of the camshaft phaser can be directly connected to the surroundings for the outflow of pressure medium due to gravity during an engine standstill, and can be closed again in a pressure-tight manner during an engine start. This design enables optimized pressure-medium outflow from the pressure chambers due to gravity in any engine standstill position.

[0018] Preferably, two pairs of two first pressure-medium outflow channels arranged diametrically opposite one another in alignment on the stator in the region of the bearing surfaces and designed as radial through-holes, and at least two pairs of two second pressure-medium outflow channels arranged diametrically opposite one another on the rotor and designed as radial elbow grooves extending in the circumferential direction on the outer diameter are provided. The respective first and second pressure-medium outflow channels communicate in the manner described above during an engine standstill and can be closed again in the manner described above during an engine start.

[0019] The camshaft phaser described above is particularly advantageous for use in vehicles with a hybrid drive, in which the combustion engine can be started very quickly by the electric motor of the hybrid drive and can be easily brought back to a defined standstill position.

[0020] The object of the invention is also achieved by a method for operating a hydraulic camshaft phaser as described above, wherein the camshaft phaser is moved from a maximally late adjustment position for activating maximally late valve control times when the internal combustion engine is at a standstill during an engine start of the same by the effect of alternating torques occurring on the camshaft of the internal combustion engine during operation in less than one second into a central adjustment position located between the maximally late adjustment position and a maximally early adjustment position for controlling maximally early valve control times for operating the internal combustion engine.

[0021] In this way, through the late setting of the valve control times in the event of engine standstill during an engine start, the intake gas exchange valves of the internal combustion engine can be kept open for a short time and a short-term decompression of the internal combustion engine can be achieved. The above-described disturbances in the internal combustion engine caused by noise and vibration during an engine start are avoided by quickly adjusting the valve control times towards earlier with the aid of the alternating torques acting on the camshaft during operation.

[0022] Preferably, during an engine standstill of the internal combustion engine, pressure medium is at least partially released from the hydraulic pressure chambers into the surroundings due to gravity, thereby avoiding or at least reducing damping caused by the pressure medium displaced from the pressure chambers during an adjustment towards earlier valve control times.

[0023] In addition, the camshaft phaser can be brought into a defined stop position when the internal combustion engine is at a standstill by means of the aforementioned method, such that at least one pressure-medium outflow connection provided for pressure-medium outflow is aligned in the effective direction of gravity.

[0024] Further claimed features of the invention result from the following description and from the figures, on the basis of which the present invention is explained in more detail. In the figures:

[0025] FIG. 1 shows a hydraulic camshaft phaser according to the invention for variable valve control of an internal combustion engine in an exploded view in a first exemplary embodiment,

[0026] FIG. 2 shows the hydraulic camshaft phaser in a sectional side view in an operating state during an engine standstill of the internal combustion engine,

[0027] FIG. 3 shows an enlarged section from FIG. 2,

[0028] FIG. 4 shows a hydraulic camshaft phaser according to the invention for variable valve control of an internal combustion engine in a sectional side view in a second exemplary embodiment in an operating state during an engine standstill of the internal combustion engine.

[0029] The figures show various views and embodiments of a hydraulic camshaft phaser according to the invention for variable valve control of an internal combustion engine. These illustrations also illustrate the method according to the invention.

[0030] The hydraulic camshaft phaser comprises a stator 1 which can be driven to rotate about a rotation and center axis 27 and a rotor 2 which can be rigidly coupled to a camshaft (not shown) (FIGS. 1 and 2). The stator 1 can be driven by a crankshaft (not shown) of the internal combustion engine via a drive wheel 35, here a chain wheel, which is arranged coaxially and is connected to the stator in a rotationally fixed manner via screw connections 34. It is coaxially supported with the inner diameter or inner circumference on the outer diameter or outer circumference of the rotor 2. The stator 1 and rotor 2 are arranged so as to be rotatable relative to one another in order to adjust the relative rotation-angle phase position between them in both effective directions of the camshaft phaser for activating the valve control times of the internal combustion engine. They define a plurality of pressure chambers 3, here four as an example, which are arranged one behind the other in the direction of rotation or circumferential direction and into which pressure medium can be introduced in order to adjust the relative rotation-angle phase position of stator 1 and rotor 2. The pressure chambers 3 are arranged diametrically opposite each other in pairs on the stator 1 and the rotor. The pressure medium used is preferably oil from a reservoir in an oil circuit, preferably from the engine oil circuit of the internal combustion engine.

[0031] To adjust the relative rotation-angle phase position, four blades 4 protruding radially from the outer diameter of the rotor 2 and extending into each pressure chamber 3 are provided (FIGS. 1 and 2). The blades 4 can be supplied with pressure medium on both sides in the direction of rotation through openings 5, 6 on the outer diameter of the rotor 2 in the respective pressure chamber 3. By supplying pressure medium to the blades 4 and releasing the pressure medium accordingly, they can be rotated relative to the rotor 2 opposite the stator 1 in both directions of rotation in the pressure chambers. By adjusting the relative rotation-angle phase position between the stator 1 and rotor 2, the camshaft of the internal combustion engine can be adjusted towards later or earlier valve control times for opening or closing gas exchange valves (not shown) of the internal combustion engine.

[0032] By rotating the rotor 2 relative to the stator 1 in a counterclockwise direction, the relative rotation-angle phase position can be adjusted in the direction of later valve control times, and by rotating the rotor 2 relative to the stator 1 in a clockwise direction, the relative rotation-angle phase position can be adjusted in the direction of earlier valve control times. The adjustment of the relative rotation-angle phase position is limited in the direction of later valve control times to a maximally late position by a late stop 7 and the adjustment in the direction of earlier valve control times to a maximally early position is limited by an early stop 8. The blades 4 can be positioned against the stops 7, 8 in the direction of rotation or circumferential direction to limit the adjustment. They are each arranged in two pressure chambers 3 arranged diametrically opposite each other on the rotor 2 and stator 1.

[0033] The stops 7, 8 are each formed on radially inwardly projecting webs 9 of the stator 1 on the sides of the webs 9 aligned in the circumferential or rotational direction. The webs 9 delimit the pressure chambers 3 in the rotational and circumferential directions. They form bearing surfaces 10 radially inside on the inner diameter, with which the stator 1 is supported on the outer diameter of the rotor 2. The pressure chambers 3 are limited in the radial direction outwards by the stator 1 and inwards by the outer diameter of the rotor 2. Radial sealing elements 36 can be provided on the bearing surfaces 10 on the stator 1 and on the radial end faces of the free ends of the blades 4 for pressure-tight sealing.

[0034] FIGS. 1 and 2 show the camshaft phaser in a first exemplary embodiment. FIG. 2 shows the camshaft phaser during an engine standstill of the internal combustion engine, wherein the stator 1 and the rotor 2 are set in a relative rotation-angle phase position in the maximally late position. The blades 4 are positioned in the pressure chambers 3 at the respective late stop 7 in the direction of rotation or the circumferential direction.

[0035] Two pressure-medium outflow connections 11, 12 arranged diametrically opposite one another to the surroundings are provided so that pressure medium flows out of two pressure chambers 3 arranged diametrically opposite one another on the stator 1 and / or on the rotor 2 due to gravity during an engine stop of the combustion engine. The pressure-medium outflow connections each consist of a first pressure-medium outflow channel 13, 14 extending between the outer diameter and the inner diameter of the stator 1 in the area of the bearing surfaces 10 and a second pressure-medium outflow channel 15, 16 arranged on the outer diameter of the rotor 2. The first pressure-medium outflow channels 13, 14 and the second pressure-medium outflow channels 15, 16 are arranged diametrically opposite each other on the stator 1 and the rotor 2, respectively. This is indicated by a dash-dot line and by dashed lines for the hidden body edges (FIG. 1).

[0036] The first pressure-medium outflow channels 13, 14 are each designed as a radial through-hole on a web 9 on the stator 1 and are arranged diametrically opposite each other in alignment. The second pressure-medium outflow channels 15, 16 are formed by radial recesses which extend in a curved manner in the circumferential direction on the outer diameter of the rotor 2 and which are each designed as an elbow groove. The first pressure-medium outflow channels or the radial through-holes 13, 14 are each arranged in the circumferential or rotational direction in the region of the early stop 8 of the respective web 9 on the stator 1.

[0037] According to FIGS. 2 and 3, the first pressure-medium outflow channels or the radial through-holes 13, 14 and the second pressure-medium outflow channels or the elbow grooves 15, 16 are arranged such that, during an engine standstill, the elbow grooves 15, 16 on the outer diameter of the rotor 2 each communicate in the circumferential direction with a first end 17, 18 in the region of the bearing surface 10 of the stator 1 with the respective through-hole 13, 14 and with a free second end 19, 20 with the respective pressure chamber 3 in the region of the early stop 8 (FIG. 3). In this way, during an engine standstill in the maximally late position 7, the pressure medium from the region of the pressure chambers 3, which is located on the side of the blades 4 arranged in the direction of adjustment during an engine start-up in the direction of advance and which decreases during adjustment, can be completely discharged into the surroundings through the pressure-medium outflow connections 11, 12.

[0038] The through-holes 13, 14 on the inner diameter of the stator 1 and the elbow grooves 15, 16 on the outer diameter of the rotor 2 are arranged at the same axial height X, so that the through-holes 13, 14 are each radially opposite the elbow grooves 15, 16 in the relative rotation-angle phase position during the engine standstill and communicate with them for the pressure-medium outflow.

[0039] Here, the elbow grooves 15, 16 with the free second ends 19, 20 with a predetermined elbow length S in the circumferential or counterclockwise rotational direction for adjusting the relative rotation-angle phase position for the engine start, i.e., in the direction of adjustment to earlier valve control times, are arranged outside the region of the bearing surface 10, exposed for communication with the pressure chambers 3.

[0040] Consequently, during an engine standstill, pressure medium can flow from the pressure chambers 3 through the free ends of the elbow grooves 15, 16 communicating with them and further through the through-holes 13, 14 communicating with the latter due to gravity directly into the surroundings. In this way, during an engine standstill, the direct pressure-medium outflow connections 11, 12 act to a certain extent as a short circuit between the pressure chambers 3 and the surroundings for the outflow of the pressure medium.

[0041] Depending on the positioning of the through-holes 13, 14 during the engine standstill, one of the through-holes 13, 14 serves for the pressure-medium outflow and the other through-hole 13, 14 for the ventilation of the pressure chambers 3 or for the air inlet into them during the pressure-medium outflow, as indicated by an arrow.

[0042] The outflow of pressure medium can also be achieved due to gravity from the pressure chambers 3 which do not communicate directly with the surroundings via the pressure-medium outflow connections 11, 12 during an engine stop, since these pressure chambers 3 are in pressure-medium connection via the openings 5, 6 on the outer diameter of the rotor 2 with a central annular channel 21 in the region of a central through-opening 22 on the rotor 2 and are in pressure-medium connection via the annular channel 21 with the pressure chambers 3 which are directly connected to the pressure-medium outflow connections 11, 12 (FIGS. 1 and 2). A central hydraulic control valve (not shown) for hydraulically controlling the camshaft phaser can be inserted into the central through-opening 22 on the rotor 2.

[0043] To optimize the desired pressure-medium outflow, the design of the pressure-medium outflow connections 11, 12 can be further optimized by adapting the radial depth T of the elbow grooves 15, 16 on the rotor 2 and / or by adapting the diameter D of the radial through-holes 13, 14 on the stator 1 to the usage and operating conditions of the camshaft phaser (FIG. 3). The operating conditions during normal operation of the internal combustion engine, in particular the operating temperature when the engine is warm, are preferably used as a basis.

[0044] Since the pressure medium has at least partially drained from the pressure chambers 3 via the pressure-medium outflow connections 11, 12 during the engine standstill, the damping by the pressure medium to be displaced from the pressure chambers 3 is reduced to such an extent in the event of an engine start during the adjustment towards earlier valve control times that the adjustment can be carried out solely by the alternating torques of the camshaft acting on the rotor 2 during operation if the pressure medium pressure is insufficient during the engine start. This also makes it possible to overcome the friction that counteracts an adjustment towards earlier valve control times.

[0045] It is also possible to provide torsion spring means (not shown) arranged between the stator 1 and rotor 2 to assist the adjustment during an engine start-up in the direction of earlier valve control times, which pre-tension the stator 1 and rotor 2 to adjust the relative rotation-angle phase position in the direction of earlier valve control times.

[0046] Preferably, as shown in FIGS. 2 and 3, during an engine standstill the first pressure-medium outflow channels or the through-holes 13, 14 are arranged in the effective direction of gravity 23 indicated by an arrow (FIG. 2). The through-hole 14 located at the bottom relative to the effective direction of gravity 23 and the second pressure-medium outflow channel or the elbow groove 16 serve for the direct pressure-medium outflow into the surroundings, while the through-hole 13 located at the top relative to the effective direction of gravity 23 and the elbow groove 15 ventilate the pressure chambers 3 during the pressure-medium outflow. In this way, an optimal pressure-medium outflow can be achieved during engine standstill of the internal combustion engine.

[0047] Preferably, a locking mechanism 24 is provided, by means of which the stator 1 and rotor 2 can be coupled in a rotationally rigid manner in certain operating states, such as when the internal combustion engine is at a standstill as shown in FIGS. 2 and 3. Preferably, the locking mechanism 24 is designed in such a way and the camshaft phaser is arranged in the assembled state on the camshaft in such a way that in the event of an engine standstill in a position of the stator 1 and rotor 2 locked in the maximally late position 7, the pressure-medium outflow connections 11, 12 are aligned in the effective direction of gravity 23 as described above (FIG. 2). To lock the stator 1 and the rotor 2, the locking mechanism 24 has a plurality of locking pins 26 arranged in holes pre-tensioned by springs 25, which can be displaced by pressure medium (FIG. 1).

[0048] During an engine start-up of the internal combustion engine, by adjusting the relative rotation-angle phase position in the direction of earlier valve control times, i.e., by rotating the rotor 2 relative to the stator 1 in a clockwise direction, the first pressure-medium outflow channel or the through-holes 14, 15 on the bearing surfaces 10 are covered in a pressure medium-tight or airtight manner by the outer diameter of the rotor 2 and the second pressure-medium outflow channel or the elbow grooves 15, 16 are covered in a pressure medium-tight or airtight manner by the bearing surface 10 on the inner diameter of the stator 1. To avoid unwanted pressure-medium leakage at the pressure-medium outflow connections 11, 12, the bearing surfaces 10 are designed for sealing with a corresponding width B in the circumferential or rotational direction.

[0049] In order to achieve a rapid interruption of the pressure-medium outflow connections 11, 12 to the surroundings during an engine start-up, the elbow length S, along which the free second ends 19, 20 of the arc grooves 15, 16 communicate with the pressure chambers 3 for pressure-medium outflow during engine standstill, is set according to an adjustment of the relative rotation-angle phase position during an engine start by an angle of rotation α of the rotor 2 and the camshaft of 1° to 2°. As a result, the pressure-medium outflow connections 11, 12 can be interrupted during an engine start-up by adjusting the relative rotation-angle phase position in the direction of earlier valve control times as soon as the rotor 2 is rotated by 1° to 2° relative to the stator 1 and away from the maximally late position at the late stop 7.

[0050] The engine is started from the maximally late position 7, which is set while the combustion engine is at a standstill. Consequently, when the intake gas exchange valves of the internal combustion engine are controlled by the camshaft phaser, the intake gas exchange valves can be kept open for a short time during the first engine stroke during the start-up process, whereby a short-term decompression of the engine can be achieved during the start-up process.

[0051] In addition, by at least partial outflow of the pressure medium from the pressure chambers into the surroundings during engine standstill of the internal combustion engine, the relative rotation-angle phase position during engine start-up can be adjusted in less than one second from the maximally late position to an intermediate position between the maximally late position 7 and the maximally early position 8 for further operation of the internal combustion engine. The camshaft phaser according to the invention can therefore be used particularly advantageously in vehicles with a hybrid drive, in which the combustion engine can be started very quickly by the electric motor of the hybrid drive and can be easily brought back into a defined standstill position.

[0052] Due to the rapid adjustment and the short-term decompression of the internal combustion engine during an engine start, disturbances caused by noise and vibrations, known as NVH (noise vibration harshness) problems, can be reliably avoided.

[0053] FIG. 4 shows a second exemplary embodiment of a camshaft phaser according to the invention, in which, in addition to the first embodiment according to FIGS. 1 and 2, in addition to the first pair with two pressure-medium outflow connections 11, 12 arranged diametrically opposite one another on the stator 1 and the rotor 2, a second pair with two pressure-medium outflow connections 28, 29 arranged diametrically opposite one another on the stator 1 and the rotor 2 is provided. The second pair of pressure-medium outflow connections 28, 29 serves as a direct connection to the surroundings for discharging pressure medium from the two remaining pressure chambers 3 of the camshaft phaser arranged diametrically opposite one another on the stator 1 and rotor 2 during an engine standstill of the internal combustion engine. Accordingly, all four pressure chambers 3 of the camshaft phaser can be directly connected to the surroundings for the outflow of pressure medium due to gravity during an engine standstill, and can be closed again in a pressure-tight manner during an engine start.

[0054] Here, the second pair of pressure-medium outflow connections 28, 29 is arranged offset by 90° in the direction of rotation relative to the first pair of pressure-medium outflow connections 11, 12 and is designed analogously to the first pair, so that the second pair of pressure-medium outflow connections 28, 29 also functions analogously during operation. Accordingly, the second pair of pressure-medium outflow connections 28, 29 consists of first pressure-medium outflow channels 30, 31, which are designed as diametrically opposite radial through-holes arranged in alignment on the webs 9 of the stator 1 in the region of the bearing surfaces 10. The latter are each arranged in the manner described above corresponding to second pressure-medium outflow channels 32, 33 on the outer diameter of the rotor 2, which are designed as recesses or as elbow grooves.

[0055] Corresponding to the first pair of pressure-medium outflow connections 11, 12, the elbow grooves 32, 33 communicate in the shown maximally late position 7 of the camshaft phaser during an engine standstill with a first end 37, 38 in the area of the bearing surface 10 of the stator 1 with the respective through-hole 30, 31 and with a free second end 39, 40 with the respective pressure chamber 3. During an engine start-up, by adjusting the relative rotation-angle phase position, the through-holes 30, 31 on the stator 1 can be covered again in a pressure-tight manner by the outer diameter of the rotor 2 and the elbow grooves 32, 33 on the rotor 2 can be covered again in a pressure-tight manner by the bearing surfaces 10 on the inner diameter of the stator 1.

[0056] In this way, a direct pressure-medium outflow into the surroundings due to gravity is possible from all four pressure chambers 3 of the camshaft phaser in the event of an engine standstill of the internal combustion engine. This option enables optimized pressure-medium outflow from the pressure chambers 3 due to gravity in any engine standstill position.LIST OF REFERENCE SIGNS1 Stator

[0058] 2 Rotor

[0059] 3 Pressure chamber

[0060] 4 Blade

[0061] 5 Opening

[0062] 6 Opening

[0063] 7 Late stop, maximally late position

[0064] 8 Early stop, maximally early position

[0065] 9 Web

[0066] 10 Bearing surface

[0067] 11 Pressure-medium outflow connection

[0068] 12 Pressure-medium outflow connection

[0069] 13 First pressure-medium outflow channel, through-hole

[0070] 14 First pressure-medium outflow channel, through-hole

[0071] 15 Second pressure-medium outflow channel, recess, elbow groove

[0072] 16 Second pressure-medium outflow channel, recess, elbow groove

[0073] 17 End

[0074] 18 End

[0075] 19 End

[0076] 20 End

[0077] 21 Annular channel

[0078] 22 Through-opening

[0079] 23 Effective direction of gravity

[0080] 24 Locking mechanism

[0081] 25 Spring

[0082] 26 Locking pin

[0083] 27 Rotation and center axis

[0084] 28 Pressure-medium outflow connection

[0085] 29 Pressure-medium outflow connection

[0086] 30 First pressure-medium outflow channel, through-hole

[0087] 31 First pressure-medium outflow channel, through-hole

[0088] 32 Second pressure-medium outflow channel, recess, elbow groove

[0089] 33 Second pressure-medium outflow channel, recess, elbow groove

[0090] 34 Screw connection

[0091] 35 Drive wheel

[0092] 36 Sealing element

[0093] 37 End

[0094] 38 End

[0095] 39 End

[0096] 40 End

[0097] X Axial height

[0098] S Elbow length

[0099] α Angle of rotation

[0100] D Diameter

[0101] B Width

[0102] T Depth

Claims

1. A hydraulic camshaft phaser for variable valve control of an internal combustion engine, comprising:a stator,a rotor,a plurality of pressure chambers delimited by the stator and rotor, the plurality of pressure chambers configured to receive pressure medium so as to adjust a relative rotation-angle phase position between the stator and the rotor, andat least one pressure-medium outflow connection fluidly connected to surroundings outside of the hydraulic camshaft phaser, andwhen the hydraulic camshaft phaser is in a rotation-angle phase position that corresponds to a maximally late valve control time of the internal combustion engine, the pressure medium flows out of at least one pressure chamber of the plurality of pressure chambers and into the surroundings outside of the hydraulic camshaft phaser via gravity during an engine standstill of the internal combustion engine, and the at least one pressure-medium outflow connection can be closed via adjustment of the relative rotation-angle phase position during an engine start.

2. The hydraulic camshaft phaser according to claim 1, wherein the at least one pressure-medium outflow connection includes:at least one first pressure-medium outflow channel extending from an outer diameter of the stator to at least one bearing surface on an inner diameter of the stator, andat least one second pressure-medium outflow channel arranged on an outer diameter of the rotor configured to fluidly communicate with one of the plurality of pressure chambers and with the first pressure-medium outflow channel during an engine standstill.

3. The hydraulic camshaft phaser according to claim 2, wherein during an engine start-up, when adjusting the relative rotation-angle phase position, the first pressure-medium outflow channel is covered in a pressure-tight manner via the outer diameter of the rotor and the second pressure-medium outflow channel is covered in a pressure-tight manner by the at least one bearing surface on the inner diameter of the stator.

4. The hydraulic camshaft phaser according to one of claim 2, wherein the first pressure-medium outflow channel is configured as a radial through-hole on the stator and the second pressure-medium outflow channel on the outer diameter of the rotor is configured as a radial elbow groove extending in a circumferential direction.

5. The hydraulic camshaft phaser according to claim 4, wherein during an engine standstill, the radial elbow groove on the outer diameter of the rotor fluidly communicates in the circumferential direction with a first end of the radial through-hole in a region of the at least one bearing surface, and with a free second end extending outside the region of the at least one bearing surface with the one of the plurality of pressure chambers.

6. The hydraulic camshaft phaser according to claim 5, wherein during an engine standstill, the radial elbow groove extends with the free second end outside the region of the at least one bearing surface with a predetermined elbow length in a direction of adjustment of the relative rotation-angle phase position that corresponds to an engine start, wherein the predetermined elbow length corresponds to an adjustment of the relative rotation-angle phase position during an engine start by an angle of rotation of 1° to 2°.

7. The hydraulic camshaft phaser according to claim 1, wherein the at least one pressure-medium outflow connection comprises two pressure-medium outflow connections arranged diametrically opposite one another on the stator and on the rotor such that the pressure medium is configured to flow out of at least two pressure chambers of the plurality of pressure chambers arranged diametrically opposite one another on the stator and on the rotor and into the surroundings outside of the hydraulic camshaft phaser due to gravity during an engine standstill of the internal combustion engine.

8. The hydraulic camshaft phaser according to claim 2, wherein:the at least one pressure-medium outflow connection comprises two pressure-medium outflow connections arranged diametrically opposite one another on the stator and the rotor, andfirst pressure-medium outflow channels of the two pressure-medium outflow connections are arranged diametrically opposite one another in alignment on the stator and configured as radial through-holes, andtwo second pressure-medium outflow channels of the two pressure-medium outflow connections are arranged diametrically opposite one another on the rotor and configured as radial elbow grooves extending in a circumferential direction on the outer diameter of the rotor such that the pressure medium flows out of two pressure chambers of the plurality of pressure chambers, the two pressure chambers arranged diametrically opposite one another on the stator and on the rotor into the surroundings outside of the hydraulic camshaft phaser due to gravity during an engine standstill of the internal combustion engine.

9. The hydraulic camshaft phaser according to claim 2, wherein:the at least one first press-medium outflow channel comprises at least two pairs of first pressure-medium outflow channels arranged diametrically opposite one another in alignment on the stator in a region of the at least one bearing surface and configured as radial through-holes, andthe at least one second pressure-medium outflow channel comprises at least two pairs of two second pressure-medium outflow channels arranged diametrically opposite one another on the rotor and configured as radial elbow grooves extending in a circumferential direction on the outer diameter of the rotor such that the pressure medium flows out of two pairs of pressure chambers of the plurality of pressure chambers arranged diametrically opposite one another on the stator and on the rotor, and into the surroundings outside of the hydraulic camshaft phaser due to gravity during an engine standstill of the internal combustion engine.

10. A method for operating a hydraulic camshaft phaser according to claim 1, wherein the hydraulic camshaft phaser is moved from an engine standstill during an engine start from a first adjustment position corresponding to the maximally late valve control time of the internal combustion engine via alternating torques occurring on a camshaft of the internal combustion engine during operation in less than one second, to a middle adjustment position located between the first adjustment position and a maximally early adjustment position for operating the internal combustion engine.

11. A method for operating a hydraulic camshaft phaser for variable valve control of an internal combustion engine, comprising:providing:a stator,a rotor,a plurality of pressure chambers formed via:a plurality of radially inwardly extending webs arranged on the stator, anda plurality of blades of the rotor that extend radially outwardly from an outer diameter of the rotor, andthe plurality of pressure chambers configured to receive a pressure medium so as to adjust a relative rotation-angle phase position between the stator and the rotor, andmoving the rotor to a position relative to the stator corresponding to a maximally late valve control time of the internal combustion engine so that the hydraulic camshaft phaser drains the pressure medium out of one of the pressure chambers and directly to surrounding air outside of the hydraulic camshaft phaser, andmoving the rotor to a position away from the position corresponding to the maximally late valve control time so that the hydraulic camshaft phaser does not drain the pressure medium out of one of the pressure chambers and directly to surrounding air outside of the hydraulic camshaft phaser.

12. The method according to claim 11, wherein when the rotor is in the position relative to the stator corresponding to the maximally late valve control time of the internal combustion engine, another one of the pressure chambers receives air from the surrounding air outside of the hydraulic camshaft phaser.

13. The method according to claim 11, wherein when the rotor is in the position relative to the stator that corresponds to the maximally late valve control time, the hydraulic camshaft phaser drains the pressure medium out of the one of the pressure chambers via a first channel extending circumferentially on the rotor and a second channel extending radially through the stator.

14. The method according to claim 13, wherein when the rotor is moved to the position away from the position corresponding to the maximally late valve control time, the first channel is fluidly disconnected from the second channel.

15. The method according to claim 14, wherein the first channel is arranged on the outer diameter of the rotor, and the second channel extends entirely through one of the radially inwardly extending webs of the stator.

16. A hydraulic camshaft phaser for variable valve control of an internal combustion engine, comprising:a stator having radially inwardly extending webs,a rotor having radially outwardly extending blades, anda plurality of pressure chambers delimited by the radially inwardly extending webs of the stator and the radially outwardly extending blades of the rotor, the plurality of pressure chambers configured to receive a pressure medium so as to adjust a relative rotation-angle phase position between the stator and the rotor, andduring an engine standstill when the hydraulic camshaft phaser is in a rotation-angle phase position that corresponds to a maximally late valve control time of the internal combustion engine, a first radial through-hole extending entirely through one of the radially inwardly extending webs of the stator is configured to drain the pressure medium from one of the plurality of pressure chambers so that the pressure medium exits the hydraulic camshaft phaser from the stator and directly to surrounding air outside of the hydraulic camshaft phaser.

17. The hydraulic camshaft phaser according to claim 16, wherein when the hydraulic camshaft phaser is in a rotation-angle phase position that corresponds to a maximally late valve control time of the internal combustion engine, another one of the plurality of pressure chambers receives air from the surrounding air outside of the hydraulic camshaft phaser via a second radial through-hole extending entirely through another one of the radially inwardly extending webs of the stator.

18. The hydraulic camshaft phaser according to claim 16, wherein the radially outwardly extending blades extend radially outward from an outer diameter of the rotor, and the outer diameter of the rotor comprises a circumferentially extending channel fluidly connected to both the first radial through-hole and the one of the plurality of pressure chambers.

19. The hydraulic camshaft phaser according to claim 18, wherein the circumferentially extending channel is not continuously fluidly connected to the first radial through-hole.

20. The hydraulic camshaft phaser according to claim 19, wherein the circumferentially extending channel is not continuously fluidly connected to the one of the plurality of pressure chambers.

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