Hydraulic camshaft adjuster for variable valve control of an internal combustion engine

Abstract

Hydraulic camshaft adjuster for variable valve control of an internal combustion engine, comprising a stator (1) and a rotor (2) and several pressure chambers (3) bounded by these, which can be pressurized with pressure medium to adjust the relative rotational angular phase between stator (1) and rotor (2), wherein, for the drainage of pressure medium from at least one of the pressure chambers (3) into the environment by gravity during a standstill of the internal combustion engine in a rotational angular phase for controlling maximally late valve timing of the internal combustion engine, at least one pressure medium drain connection (11, 12, 28, 29) to the environment is provided, which can be closed again by adjusting the relative rotational angular phase during an engine start, characterized in that the pressure medium drain connection (11, 12, 28,29) at least one first pressure medium drain channel (13, 14, 30, 31) extending from the outer diameter of the stator (1) to at least one bearing surface (10) on the inner diameter, and at least one second pressure medium drain channel (15, 16, 32, 33) on the outer diameter of the rotor (2), the latter communicating on the one hand with a pressure chamber (3) and on the other hand with the first pressure medium drain channel (13, 14, 30, 31) during a motor standstill.

Description

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

[0002] From DE 10 2019 119 865 B4 a hydraulic camshaft adjuster for a drive train of a motor vehicle is known, comprising a stator and a rotor rotatable thereto, wherein working chambers are formed between the stator and the rotor which can be supplied with hydraulic fluid for adjusting the rotor relative to the stator.

[0003] DE 101 62 553 A1 discloses a further hydraulic camshaft adjuster in which an oil drain opening is provided. Other camshaft adjusters with drain openings are known from DE 10 2006 012 348 A1, US 6 006 708 A and EP 2 224 105 B1. Due to the relatively low oil pressure during the starting process of the internal combustion engine, the aforementioned camshaft adjusters reach an advanced position relatively late.

[0004] The invention is therefore based on the objective of proposing a hydraulic camshaft adjuster which enables improved hydraulic camshaft adjustment during engine start-up of the internal combustion engine in a structurally simple manner and in particular avoids disturbances caused by noise and vibrations.

[0005] The problem is solved by the features of claim 1. Further advantageous and claimed embodiments are described in the respective dependent claims, the description, and the drawings.

[0006] Thus, a hydraulic camshaft adjuster for variable valve timing of an internal combustion engine is proposed, comprising a stator and a rotor and several pressure chambers bounded by these, the latter being pressurized with hydraulic fluid to adjust the relative rotational phase between stator and rotor for controlling the valve timing of the internal combustion engine. To allow hydraulic fluid to drain from at least one pressure chamber to the environment by gravity during engine shutdown, when the camshaft adjuster is in a rotational phase position to control maximally late valve timing, at least one hydraulic fluid drain connection to the environment is provided, which can be closed again by adjusting the relative rotational phase during engine start-up.

[0007] The release of pressurized fluid during engine shutdown significantly reduces or even eliminates the damping caused by the pressurized fluid displaced from the pressure chambers during the adjustment towards earlier valve timing during engine start-up. This allows for a very rapid adjustment of the rotational angle phase towards earlier valve timing, even during engine start-up and without the required pressurized fluid pressure, solely due to the dynamic alternating torques of the internal combustion engine's camshaft and the frictional forces occurring during operation.

[0008] In a particularly advantageous way, starting from a standstill with maximally late set valve timing, a short-term decompression of the internal combustion engine can be achieved during an engine start, and disturbances caused by noise and vibrations, so-called Noise Vibration Harshness (NVH) problems, can be reliably avoided.

[0009] The pressure medium drain connection has at least one first pressure medium drain channel extending from the outer diameter of the stator to at least one bearing surface on the inner diameter. Additionally, at least one second pressure medium drain channel is arranged on the outer diameter of the rotor, such that during a motor shutdown, it communicates with both a pressure chamber and the first pressure medium drain channel. This enables a direct pressure medium drain connection between at least one pressure chamber and the environment during a motor shutdown.

[0010] A simple closure of the pressure medium drain connection during a motor start can be achieved if the first and second pressure drain channels are arranged in such a way that, by adjusting the relative rotation angle phase position, the first pressure medium drain channel can be covered by the outer diameter of the rotor and the second pressure medium drain channel can be covered by the bearing surface on the inner diameter of the stator in a pressure medium-tight manner.

[0011] The pressure medium drainage connection can be further simplified in terms of design by having the first pressure medium drainage channel as a radial through-hole on the stator and the second pressure medium drainage channel on the outer diameter of the rotor as a radially arc-shaped recess extending in the circumferential direction, preferably as an arc groove.

[0012] The arc groove can be arranged in such a simple way that, during a motor stop, it communicates with a through-bore at one end in the area of ​​the stator bearing surface and with a pressure chamber at the other end, which is free and located outside the area of ​​the bearing surface.

[0013] In an embodiment optimized for engine start and pressure fluid drainage during engine standstill, the arc groove extends with its free second end outside the bearing surface area, with a predetermined arc length in the direction of the change in the relative rotational angular phase during engine start. Preferably, this arc length corresponds to an adjustment of the relative rotational angular phase by 1° to 2° during engine start. This allows the pressure fluid drainage connection to be interrupted or closed during engine start by an adjustment of the relative rotational angular phase towards earlier valve timings, as soon as an adjustment of 1° to 2° from the maximum retard position is reached.

[0014] By adjusting the radial depth of the arc groove on the rotor and the diameter of the radial through-hole on the stator to the operating conditions of the camshaft adjuster, the pressure medium drainage connection can be further optimized in a simple manner. Preferably, the operating conditions during normal operation of the internal combustion engine, in particular the operating temperature when the engine is warm, are used as the basis for optimizing the desired pressure medium drainage.

[0015] It is also advantageous if, for the drainage of pressure medium from at least two pressure chambers arranged diametrically opposite each other on the stator or rotor into the environment by gravity during engine shutdown, at least two pressure medium drain connections to the environment are provided, also arranged diametrically opposite each other on the stator or rotor. In this way, it is possible to position the pressure medium drain connections in the direction of gravity during engine shutdown, such that one pressure medium drain connection, arranged at the bottom in the direction of gravity, serves to drain the pressure medium, and the other diametrically opposite pressure medium drain connection, arranged at the top in the direction of gravity, serves to vent the pressure chambers or to allow air to enter them during pressure medium drainage.

[0016] It is advantageous if at least two of the first pressure medium channels, arranged diametrically opposite each other on the stator in the area of ​​the bearing surfaces, are aligned as radial through-holes. Consequently, when the motor is stationary, these channels can be positioned in the direction of gravity.

[0017] Preferably, at least two first pressure medium drain channels, designed as radial through-holes and arranged diametrically opposite each other on the stator in the area of ​​the bearing surfaces, and at least two second pressure medium drain channels, designed as radial arc grooves extending circumferentially around the outer diameter, are provided on the rotor, also arranged diametrically opposite each other. The respective first and second pressure medium drain channels communicate as described above when the motor is at a standstill and can be closed again as described above when the motor is started.

[0018] In an advantageous embodiment of the invention, at least two pairs of pressure medium drain connections to the environment are provided for the drainage of pressure medium from at least two pairs of pressure chambers arranged diametrically opposite each other on the stator and rotor, respectively, by gravity during engine standstill. Consequently, at least four pressure chambers of the camshaft adjuster can be directly connected to the environment for the drainage of pressure medium by gravity during engine standstill, and these connections can be sealed again to prevent pressure medium leakage during engine start-up. This design enables optimized pressure medium drainage by gravity from the pressure chambers in any engine standstill position.

[0019] Preferably, two pairs of first pressure medium drain channels, each arranged diametrically opposite and aligned on the stator in the area of ​​the bearing surfaces and designed as radial through-holes, and at least two pairs of second pressure medium drain channels, each arranged diametrically opposite on the rotor and designed as radial arc grooves extending circumferentially around the outer diameter, are provided. The respective first and second pressure medium drain channels communicate as described above when the motor is at a standstill and can be closed again as described above when the motor is started.

[0020] The camshaft adjuster described above is particularly advantageous 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 easily brought back to a defined standstill position.

[0021] The problem according to the invention is also solved by a method for operating a previously described hydraulic camshaft adjuster, wherein the camshaft adjuster is moved from a maximally late adjustment position for controlling maximally late valve timing during an engine standstill of the internal combustion engine during an engine start-up, by means of alternating torques occurring during operation on the camshaft of the internal combustion engine, in less than one second to a middle adjustment position for operating the internal combustion engine, which lies between the maximally late adjustment position and a maximally early adjustment position for controlling maximally early valve timing.

[0022] In this way, by using retarded valve timing while the engine is off during start-up, the intake gas exchange valves of the internal combustion engine can be held open briefly, thus achieving a momentary decompression of the engine. This rapid adjustment towards earlier valve timing, utilizing the alternating torques acting on the camshaft during operation, prevents the aforementioned disturbances to the internal combustion engine caused by noise and vibrations during start-up.

[0023] Preferably, during a standstill of the internal combustion engine, at least some of the hydraulic pressure fluid is released into the environment by gravity, thus avoiding or at least reducing damping caused by the pressure fluid being displaced from the pressure chambers when adjusting towards earlier valve timings.

[0024] Furthermore, the aforementioned method allows the camshaft adjuster to be brought into a defined stop position when the internal combustion engine is at a standstill, such that at least one pressure medium drain connection intended for pressure medium drainage is aligned in the direction of gravity.

[0025] Further claimed features of the invention will become apparent from the following description and from the drawings, which further explain the present invention. The drawings show: Fig. 1 an exploded view of a hydraulic camshaft adjuster according to the invention for variable valve control of an internal combustion engine in a first embodiment, Fig. 2 the hydraulic camshaft adjuster in a cutaway side view in an operating state during a standstill of the internal combustion engine, Fig. 3 an enlarged section from Fig. 2, Fig. 4 a hydraulic camshaft adjuster according to the invention for variable valve control of an internal combustion engine in a cutaway side view in a second embodiment in an operating state during an engine standstill of the internal combustion engine.

[0026] The figures illustrate various views and embodiments of a hydraulic camshaft adjuster according to the invention for variable valve control of an internal combustion engine. These illustrations also clarify the method according to the invention.

[0027] The hydraulic camshaft adjuster comprises a stator 1 rotatably driven about a rotational and central axis 27 and a rotor 2 torsionally rigidly coupled to a camshaft (not shown) ( Fig. 1 and Fig. 2) The stator 1 is driven by a crankshaft (not shown) of the internal combustion engine via a coaxially arranged drive wheel 35, here a sprocket, which is non-rotatably connected to it by screw connections 34. It is coaxially supported with its inner diameter or inner circumference on the outer diameter or outer circumference of the rotor 2. For adjusting the relative rotational phase between them in both directions of action of the camshaft adjuster to control the valve timing of the internal combustion engine, the stator 1 and rotor 2 are arranged so that they can be rotated relative to each other. They define several pressure chambers 3, here four by way of example, arranged one behind the other around the circumference in the direction of rotation or circumferential rotation. These pressure chambers can be pressurized with a pressure medium to adjust the relative rotational phase between the stator 1 and rotor 2. The pressure chambers 3 are arranged in pairs diametrically opposite each other on the stator 1 and the rotor.Oil from a reservoir in an oil circuit, preferably from the engine oil circuit of the internal combustion engine, is preferably used as the pressure medium.

[0028] To adjust the relative rotational angle phase position, four radially projecting vanes 4 are provided on the outer diameter of the rotor 2, extending into each pressure chamber 3 ( Fig. 1 and Fig. 2) The vanes 4 can be pressurized with pressure medium on both sides through openings 5, 6 on the outer diameter of the rotor 2 in the respective pressure chamber 3 in the direction of rotation. By pressurizing the vanes 4 and correspondingly discharging the pressure medium, they can be rotated relative to the rotor 2 and the stator 1 in both directions of rotation within the pressure chambers. By adjusting the relative rotational phase angle between the stator 1 and rotor 2, the camshaft of the internal combustion engine can be adjusted towards later or earlier valve timing to open or close gas exchange valves (not shown) of the internal combustion engine.

[0029] By rotating the rotor 2 relative to the stator 1 counterclockwise, the relative rotational phase can be adjusted towards later valve timing, and by rotating the rotor 2 relative to the stator 1 clockwise, the relative rotational phase can be adjusted towards earlier valve timing. The adjustment of the relative rotational phase towards later valve timing is limited to a maximum retarded position by a retarded stop 7, and the adjustment towards earlier valve timing is limited to a maximum advanced position by an advanced stop 8. The vanes 4 can be engaged at the stops 7 and 8 in the rotational and circumferential directions, respectively, to limit the adjustment. They are each arranged in two pressure chambers 3 diametrically opposite each other on the rotor 2 and stator 1.

[0030] The stops 7, 8 are each formed on radially inwardly projecting webs 9 of the stator 1 on the sides of the webs 9 oriented in the circumferential or rotational direction. The webs 9 each delimit the pressure chambers 3 in the rotational or circumferential direction. Radially on the inside of the inner diameter, they form bearing surfaces 10 by which the stator 1 is supported on the outer diameter of the rotor 2. The pressure chambers 3 are delimited radially outward by the stator 1 and inward 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 vanes 4 for a pressure-tight seal.

[0031] Fig. 1 and Fig. Figure 2 shows the camshaft adjuster in a first embodiment. Fig. Figure 2 shows the internal combustion engine during a standstill, with the stator 1 and the rotor 2 set in a relative rotational phase position at the maximum retarded position. The vanes 4 are positioned in the pressure chambers 3 at the respective retarded stop 7 in the rotational or circumferential direction.

[0032] To allow pressure medium to drain from two pressure chambers 3 arranged diametrically opposite each other on the stator 1 and rotor 2, respectively, by gravity during engine shutdown, two diametrically opposite pressure medium drain connections 11, 12 to the environment are provided. Each of these drain connections consists of a first pressure medium drain channel 13, 14 extending between the outer and inner diameters of the stator 1 in the area of ​​the bearing surfaces 10, and a second pressure medium drain channel 15, 16 arranged on the outer diameter of the rotor 2. The first pressure medium drain channels 13, 14 and the second pressure medium drain channels 15, 16 are arranged diametrically opposite each other on the stator 1 and rotor 2, respectively. This is indicated by a dash-dotted line and by dashed lines for the hidden body edges. Fig. 1).

[0033] The first pressure medium drain channels 13, 14 are each designed as radial through-bores on a web 9 of the stator 1 and are arranged diametrically opposite each other in alignment. The second pressure medium drain channels 15, 16 are formed by radial recesses extending circumferentially on the outer diameter of the rotor 2, each designed as an arc groove. The first pressure medium drain channels, or the radial through-bores 13, 14, are each located in the circumferential or rotational direction in the region of the early stop 8 of the respective web 9 on the stator 1.

[0034] After Fig. 2 and Fig. 3 The first pressure medium drain channels or the radial through-bores 13, 14 and the second pressure medium drain channels or the arc grooves 15, 16 are arranged such that during a motor standstill the arc 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 area of ​​the bearing surface 10 of the stator 1 with the respective through-bore 13, 14 and with a free second end 19, 20 with the respective pressure chamber 3 in the area of ​​the early stop 8 ( Fig. 3) In this way, during an engine standstill in the maximum late position 7, the pressure medium from the area of ​​the pressure chambers 3, which is located on the side of the vanes 4 arranged in the direction of adjustment during an engine start towards early and which decreases in size during adjustment, can be completely drained into the environment through the pressure medium drain connections 11, 12.

[0035] The through bores 13, 14 on the inner diameter of the stator 1 and the arc slots 15, 16 on the outer diameter of the rotor 2 are arranged at the same axial height X, so that the through bores 13, 14 are radially opposite the arc slots 15, 16 in the relative rotational angle phase position during the motor standstill and communicate with them for the pressure medium drainage.

[0036] Here, the arc grooves 15, 16 with the free second ends 19, 20 with a predetermined arc length S are arranged in the circumferential or rotational direction counterclockwise for adjusting the relative rotational angle phase position for engine start, i.e. in the direction of adjustment to earlier valve timings, extending freely outside the area of ​​the bearing surface 10 for communication with the pressure chambers 3.

[0037] Consequently, during an engine shutdown, pressure medium can drain from the pressure chambers 3 through the free ends communicating with them (arc grooves 15, 16) and further via the through-bores 13, 14 communicating with the latter, directly into the environment by gravity. In this way, during an engine shutdown, the direct pressure medium drain connections 11, 12 act, to a certain extent, as a short circuit between the pressure chambers 3 and the environment for the discharge of the pressure medium.

[0038] 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 drain and the other through-hole 13, 14 for the ventilation of the pressure chambers 3 or for air entry into them during pressure medium draining, as indicated by an arrow in each case.

[0039] Pressure medium drainage by gravity is also possible from the pressure chambers 3 that do not communicate directly with the environment via the pressure medium drain connections 11, 12 during a motor stop, since these pressure chambers 3 are in pressure medium communication with a central annular channel 21 in the area of ​​a central through-opening 22 on the rotor 2 via the openings 5, 6 on the outer diameter of the rotor 2 and are in pressure medium communication with the pressure chambers 3 directly connected to the pressure medium drain connections 11, 12 via the annular channel 21 ( Fig. 1 and Fig. 2) A central hydraulic control valve (not shown) for hydraulic control of the camshaft adjuster can be inserted into the central through-opening 22 on the rotor 2.

[0040] To optimize the desired pressure medium drainage, the design of the pressure medium drainage connections 11, 12 can be further optimized by adjusting the radial depth T of the arc grooves 15, 16 on the rotor 2 and / or by adjusting the diameter D of the radial through-bores 13, 14 on the stator 1 to the operating conditions of the camshaft adjuster ( Fig. 3) Preferably, the operating conditions during normal operation of the internal combustion engine are used as a basis, in particular the operating temperature when the engine is warm.

[0041] Since the hydraulic fluid has at least partially drained from the pressure chambers 3 via the hydraulic fluid drain connections 11, 12 during engine shutdown, the damping caused by the hydraulic fluid displaced from the pressure chambers 3 during engine start-up is reduced to such an extent that, even with insufficient hydraulic pressure during engine start-up, the adjustment can be achieved solely by the alternating torques of the camshaft acting on the rotor 2 during operation. This also overcomes the friction that would otherwise oppose adjustment towards earlier valve timing.

[0042] It is also possible to provide torsional spring means (not shown) arranged between stator 1 and rotor 2 to assist in adjusting the relative rotational angle phase position towards earlier valve timings during engine start-up, which preload stator 1 and rotor 2 to adjust the relative rotational angle phase position towards earlier valve timings.

[0043] Preferably as in Fig. 2 and Fig. 3 shown, during an engine standstill, the first pressure medium drain channels or the through bores 13, 14 are arranged in the direction of action of gravity 23 indicated by an arrow ( Fig. 2) The through-bore 14, located at the bottom relative to the direction of gravity 23, and the second pressure medium drain channel or the arc groove 16 serve for the direct drainage of the pressure medium into the environment, while the through-bore 13 and the arc groove 15, located at the top relative to the direction of gravity 23, provide ventilation for the pressure chambers 3 during the pressure medium drainage. In this way, optimal pressure medium drainage can be achieved during a shutdown of the internal combustion engine.

[0044] Preferably, a locking mechanism 24 is provided, by which, in certain operating conditions, such as during the operation described in Fig. 2 and Fig. 3. In the engine standstill of the internal combustion engine, stator 1 and rotor 2 can be rigidly coupled. Preferably, the locking mechanism 24 is designed and the camshaft adjuster is arranged on the camshaft in the mounted state such that, when the engine is at standstill in a position 7 where stator 1 and rotor 2 are locked in the maximum late position, the pressure medium drain connections 11, 12 are aligned in the direction of the force of gravity 23 as described above. Fig. 2) To lock stator 1 and rotor 2, the locking mechanism 24 has several locking pins 26 arranged in bores and pre-tensioned by springs 25, which are displaceable by the application of pressure medium ( Fig. 1).

[0045] During engine start-up, the first pressure medium drain channel or through-holes 14, 15 on the bearing surfaces 10 are sealed by the outer diameter of the rotor 2, and the second pressure medium drain channel or arc grooves 15, 16 are sealed by the bearing surface 10 on the inner diameter of the stator 1, creating a pressure medium-tight or airtight seal. This is achieved by adjusting the relative rotational phase towards earlier valve timing, i.e., by rotating the rotor 2 clockwise relative to the stator 1. To prevent unwanted pressure medium leakage at the pressure medium drain connections 11, 12, the bearing surfaces 10 are designed with a corresponding width B in the circumferential or rotational direction for sealing.

[0046] To achieve a rapid interruption of the pressure medium drain connections 11, 12 to the environment during engine start-up, the arc 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 drain during engine standstill, is set according to an adjustment of the relative rotational angular phase position by a rotational angle α of the rotor 2 and the camshaft of 1° to 2° during engine start-up. This allows the pressure medium drain connections 11, 12 to be interrupted during engine start-up by an adjustment of the relative rotational angular phase position towards earlier valve timing as soon as the rotor 2 is rotated 1° to 2° relative to the stator 1 from the maximum late position at the late stop 7.

[0047] The engine starts from the maximum late position 7, which is set when the internal combustion engine is at a standstill. Consequently, when the intake gas exchange valves of the internal combustion engine are actuated by the camshaft adjuster, the intake gas exchange valves can be held open briefly during the first engine stroke of the starting process, thus achieving a brief decompression of the engine during the starting process.

[0048] Furthermore, by at least partially releasing the pressure medium from the pressure chambers into the environment while the internal combustion engine is at rest, the relative rotational angle phase during engine start-up can be adjusted from the maximum late position to an intermediate position between the maximum late position 7 and the maximum early position 8 in less than one second, enabling continued operation of the internal combustion engine. The camshaft adjuster according to the invention is therefore particularly advantageous for use in vehicles with a hybrid drive, in which the internal combustion engine can be started very quickly by the electric motor of the hybrid drive and easily brought back to a defined standstill position.

[0049] Due to the rapid adjustment and the brief decompression of the internal combustion engine during engine start-up, disturbances caused by noise and vibration, so-called NVH problems (Noise Vibration Harshness), can be reliably avoided.

[0050] In Fig. Figure 4 shows a second embodiment of a camshaft adjuster according to the invention, in which, in addition to the first embodiment according to Fig. 1 and Fig.In addition to the first pair of pressure medium drain connections 11, 12 arranged diametrically opposite each other on the stator 1 and rotor 2, a second pair of pressure medium drain connections 28, 29 is provided. The second pair of pressure medium drain connections 28, 29 serves as a direct connection to the environment for the drainage of pressure medium from the two remaining pressure chambers 3 of the camshaft adjuster, which are arranged diametrically opposite each other on the stator 1 and rotor 2, during a shutdown of the internal combustion engine. Consequently, all four pressure chambers 3 of the camshaft adjuster can be directly connected to the environment for the drainage of pressure medium by gravity during a shutdown of the engine, and can be sealed again to prevent pressure medium leakage during engine start-up.

[0051] The second pair of pressure medium drain connections 28, 29 is arranged offset by 90° in the direction of rotation from the first pair of pressure medium drain connections 11, 12 and is designed analogously to the first pair, so that the second pair of pressure medium drain connections 28, 29 also functions analogously in operation. Accordingly, the second pair of pressure medium drain connections 28, 29 consists of first pressure medium drain channels 30, 31, which are designed as diametrically opposed, aligned radial through-bores on the webs 9 of the stator 1 in the area of ​​the bearing surfaces 10. These through-bores correspond to second pressure medium drain channels 32, 33 on the outer diameter of the rotor 2, which are designed as recesses or arc grooves, respectively, as described above.

[0052] Corresponding to the first pair of pressure medium drain connections 11, 12, the arc grooves 32, 33 in the illustrated maximum late position 7 of the camshaft adjuster communicate 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, the through-holes 30, 31 on the stator 1 can be sealed again by the outer diameter of the rotor 2 and the arc grooves 32, 33 on the rotor 2 can be sealed again by the bearing surfaces 10 on the inner diameter of the stator 1 in a pressure medium-tight manner by the adjustment of the relative rotational angle phase.

[0053] In this way, when the internal combustion engine is at a standstill, a direct discharge of pressurized fluid into the environment is achieved from all four pressure chambers 3 of the camshaft adjuster by gravity. This option enables optimized discharge of pressurized fluid by gravity from the pressure chambers 3 in any engine standstill position. Reference symbol list 1 Stator 2 Rotor 3 pressure chamber 4 wings 5 Opening 6 Opening 7 Late attack, maximum late position 8 Early strike, maximum early position 9 Bridge 10 storage area 11 Pressure medium drain connection 12 Pressure medium drain connection 13 First pressure medium drain channel, through-hole 14 First pressure medium drain channel, through-hole 15 Second pressure medium drainage channel, recess, arc groove 16 Second pressure medium drainage channel, recess, arc groove 17 End 18 End 19 End 20 End 21 Ring channel 22 Passage opening 23 Direction of action of gravity 24 locking mechanism 25 springs 26 Locking pin 27 Rotation and central axis 28 Pressure medium drain connection 29 Pressure medium drain connection 30 First pressure medium drain channel, through bore 31 First pressure medium drain channel, through-hole 32 Second pressure medium drainage channel, recess, arc groove 33 Second pressure medium drainage channel, recess, arc groove 34 screw connections 35 drive wheel 36 Sealing element 37 End 38 End 39 End 40 End X axial height S arc length α Rotation angle Diameter B Width T depth

Claims

[1] Hydraulic camshaft adjuster for variable valve control of an internal combustion engine, comprising a stator (1) and a rotor (2) and a plurality of pressure chambers (3) delimited by these, which can be pressurised with pressure medium to adjust the relative rotational angle phase position between the stator (1) and the rotor (2), wherein at least one pressure medium outlet connection (11, 12, 28, 29) to the environment is provided for the discharge of pressure medium from at least one of the pressure chambers (3) into the environment by the effect of gravity during an engine standstill of the internal combustion engine in a rotational angle phase position for controlling maximally late valve control times of the internal combustion engine, which pressure medium outlet connection can be closed again by adjusting the relative rotational angle phase position during an engine start, characterized bythat the pressure medium discharge connection (11, 12, 28, 29) has at least one first pressure medium discharge channel (13, 14, 30, 31) on the stator (1) running from the outer diameter to at least one bearing surface (10) on the inner diameter, and at least one second pressure medium discharge channel (15, 16, 32, 33) on the outer diameter of the rotor (2), the latter communicating on the one hand with a pressure chamber (3) and on the other hand with the first pressure medium discharge channel (13, 14, 30, 31) during an engine standstill. [2] Hydraulic camshaft adjuster according to claim 1, characterized by that during an engine start, by adjusting the relative rotational angle phase position, the first pressure medium discharge channel (13, 14, 30, 31) can be covered in a pressure-tight manner by the outer diameter of the rotor (2) and the second pressure medium discharge channel (15, 16, 32, 33) can be covered in a pressure-tight manner by the bearing surface (10) on the inner diameter of the stator (1). [3] Hydraulic camshaft adjuster according to one of claims 1 or 2, characterized by that the first pressure medium discharge channel (13, 14, 30, 31) is designed as a radial through-bore on the stator (1) and the second pressure medium discharge channel (15, 16, 32, 33) on the outer diameter of the rotor (2) is designed as a radial arcuate groove running in the circumferential direction. [4] Hydraulic camshaft adjuster according to claim 3, characterized by that during a motor standstill, the curved groove (15, 16, 32, 33) on the outer diameter of the rotor (2) communicates in the circumferential direction with a first end (17, 18) in the region of the bearing surface (10) of the stator (1) with the through-bore (13, 14, 30, 31) and with a free second end (19, 20) outside the region of the bearing surface (10) with a pressure chamber (3). [5] Hydraulic camshaft adjuster according to claim 4, characterized bythat during an engine standstill, the curved groove (15, 16, 32, 33) runs with the free second end (19, 20) outside the area of ​​the bearing surface (10) with a predetermined arc length (S) in the direction of the adjustment of the relative rotational angle phase position to the engine start, wherein the arc length (S) corresponds to an adjustment of the relative rotational angle phase position at engine start by a rotation angle (α) of 1° to 2°. [6] Hydraulic camshaft adjuster according to one of claims 1 to 5, characterized by in that at least two pressure medium outlet connections (11, 12) arranged diametrically opposite one another on the stator (1) and on the rotor (2) are provided to drain pressure medium from at least two pressure chambers (3) arranged diametrically opposite one another on the stator (1) and on the rotor (2) into the environment by the effect of gravity during the engine standstill of the internal combustion engine. [7] Hydraulic camshaft adjuster according to one of claims 1 to 6, characterized by in that for the discharge of pressure medium from two pressure chambers (3) arranged diametrically opposite one another on the stator (1) and on the rotor (2) into the environment by the effect of gravity during the engine standstill of the internal combustion engine, two first pressure medium discharge channels (13, 14) arranged diametrically opposite one another on the stator (1) in the region of the bearing surfaces (10) and designed as radial through-bores and two second pressure medium discharge channels (15, 16) arranged diametrically opposite one another on the rotor (2) and designed as radial arcuate grooves running in the circumferential direction on the outer diameter are provided. [8] Hydraulic camshaft adjuster according to one of claims 1 to 6, characterized byin that for the discharge of pressure medium from two pairs of two pressure chambers (3) each arranged diametrically opposite one another on the stator (1) and on the rotor (2) by gravity into the environment during the engine standstill of the internal combustion engine, at least two pairs of two first pressure medium discharge channels (13, 14, 30, 31) each arranged diametrically opposite one another on the stator (1) in the region of the bearing surfaces (10) and designed as radial through-bores and two pairs of two second pressure medium discharge channels (15, 16, 32, 33) each arranged diametrically opposite one another on the rotor (2) and designed as radial arcuate grooves running in the circumferential direction on the outer diameter are provided.

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