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

Abstract

The invention relates to a hydraulic control valve (1) for a camshaft adjuster (5) for the variable valve control of an internal combustion engine, comprising a valve housing (2) having control connections (3, 4) for the inflow and outflow of hydraulic medium into and out of the camshaft adjuster, and a control piston (6) which is slidable in the valve housing for controlling the hydraulic medium inflow and outflow at the control connections, with a hydraulic-medium reservoir (18) being provided in the valve housing for collecting and temporarily storing the hydraulic medium flowing out of the camshaft adjuster at one of the control connections, and a throttled outflow connection (42) being provided for discharging the collected and temporarily stored hydraulic medium from the valve housing. The invention also relates to a camshaft adjusting assembly having a camshaft adjuster for the variable valve control of an internal combustion engine, comprising at least one control valve of this kind.

Description

[0001] Hydraulic control valve for a camshaft adjuster for variable valve control of an internal combustion engine

[0002] The invention relates to a hydraulic control valve for a 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. The invention further relates to a camshaft adjustment arrangement with a camshaft adjuster for variable valve control of an internal combustion engine, with at least one such control valve.

[0003] EP 2 041 404 B1 discloses a hydraulic control valve for a device for variably adjusting the control timing of gas exchange valves. The control valve comprises a hollow cylindrical valve housing with an inlet connection, an outlet connection, two supply connections, and a control piston that is axially movable within the valve housing.

[0004] Another hydraulic control valve is known from DE 102015 113 516 A1. DE 11 2018 001 233 T5 discloses a control valve of this type.

[0005] The invention is therefore based on the object of proposing a control valve and a camshaft adjustment arrangement of the aforementioned type which, in a structurally simple manner, enable the outflow of hydraulic fluid from the camshaft adjuster to be limited without influencing the inflow of hydraulic fluid into the camshaft adjuster.

[0006] The object is achieved by a hydraulic control valve having the features of claim 1 and by a camshaft adjustment arrangement having the features of claim 8. Further advantageous and claimed embodiments emerge from the respective subclaims, the description, and the drawings.

[0007] Thus, a hydraulic control valve for a camshaft adjuster for variable valve control in an internal combustion engine is proposed. The control valve has a valve housing with control ports for the inflow and outflow of hydraulic fluid into and out of the camshaft adjuster, and a control piston movable within the valve housing for controlling the inflow and outflow of hydraulic fluid at the control ports. In order to enable a structurally simple limitation of the outflow of hydraulic fluid from the camshaft adjuster, a hydraulic fluid reservoir is provided in the valve housing for collecting and temporarily storing the hydraulic fluid flowing out of the camshaft adjuster at one of the control ports, and a throttled outlet port is provided for discharging the collected and temporarily stored hydraulic fluid from the valve housing.

[0008] Accordingly, the proposed control valve enables the outflowing hydraulic fluid to be temporarily stored in the hydraulic fluid reservoir and the hydraulic fluid to be throttled from there. This allows the outflow of hydraulic fluid from the camshaft adjuster to be throttled directly at the control valve without affecting the hydraulic fluid supply to the camshaft adjuster, in particular without changing the control edges or flanks at the control ports of the control valve.

[0009] The throttled flow at the control valve ensures that more hydraulic fluid is always available to the camshaft adjuster than is drained from it. This reliably prevents the camshaft adjuster from running idle during operation and instabilities caused by air and foam formation in the adjustment system.

[0010] In a particularly preferred, simple embodiment of the invention, the throttled outlet connection is a restrictor with an orifice for discharging the hydraulic fluid from the valve housing. The design of the orifice allows the throttled outlet from the camshaft adjuster to be adjusted particularly easily on the control valve, depending on the operating conditions.

[0011] The proposed control valve can be further simplified in a next development of the invention if the orifice is designed as a cover which closes the valve housing at one end up to the orifice opening in a hydraulically tight manner.

[0012] The hydraulic fluid reservoir can be implemented as an integral component of the control valve in a particularly simple manner if it is formed as an additional hydraulic fluid chamber delimited by the valve housing and the orifice. The hydraulic fluid reservoir is preferably formed in an extended end of the valve housing.

[0013] It is also advantageous if the hydraulic fluid reservoir communicates with the control connections on the valve housing via a hydraulic fluid connection formed in the control piston and opening into the hydraulic fluid reservoir.

[0014] In a further simplified arrangement, the control piston preferably projects with a free end into the hydraulic fluid reservoir.

[0015] To actuate the control piston, which is movable within the valve housing, a plunger actuated by an actuator is preferably provided. In a particularly simple and space-saving manner, this plunger is preferably guided through the orifice and extends into the hydraulic fluid reservoir to establish actuating contact with the control piston.

[0016] The object of the invention is also achieved by a camshaft adjustment arrangement with a camshaft adjuster for variable valve control of an internal combustion engine with a control valve as described above. This results in the advantages already described above.

[0017] Preferably, the control valve is arranged coaxially to the rotational and central axis of the camshaft adjuster in a central receptacle of the same, connected to it in a rotationally fixed manner, and is designed with a throttled drain connection for discharging hydraulic fluid collected and temporarily stored in a hydraulic fluid reservoir in the control valve from the control valve.

[0018] Preferably, at least one stationary hydraulic fluid guide element is provided in the region of the throttled outlet connection, such that the hydraulic fluid guide element guides the hydraulic fluid flowing out of the control valve at the throttled outlet back into the camshaft adjuster.

[0019] This allows the throttled hydraulic fluid flowing from the control valve to be diverted directly into the camshaft adjuster via a short route and made available for camshaft adjustment. This prevents the hydraulic fluid from flowing into an engine tank, from which it must first be pressure-fed back into the camshaft adjuster. This allows for a pressure-free, radially external, direct hydraulic fluid return to the camshaft adjuster, which can, in particular, improve the dynamics of camshaft adjustment.

[0020] Further features of the invention will become apparent from the following description and the drawing, which further explains the present invention. The single figure shows an example of a hydraulic control valve 1 according to the invention for a hydraulic camshaft adjuster 5 for variable valve control of an internal combustion engine. This illustration also illustrates the camshaft adjustment arrangement according to the invention.

[0021] The control valve 1 has a cylindrical valve housing 2 with several radially extending control ports 3, 4 for the inlet and outlet of hydraulic fluid into and from the camshaft adjuster 5, which is only partially shown. To control the inlet and outlet of hydraulic fluid at the control ports 3, 4, a hollow cylindrical control piston 6 is movably arranged in the valve housing 2.

[0022] The camshaft adjuster 5 is arranged coaxially with a camshaft 7 of the internal combustion engine. The control valve 1 with the cylindrical valve housing 2 is arranged coaxially with the rotational and central axis 8 of the camshaft adjuster 5 in a central receptacle 9 of the camshaft adjuster 5, and is connected thereto in a rotationally fixed manner. Its free end is connected thereto in a central bore 10 extending from one end of the camshaft 7 and is screwed, for example, with an external thread into an internal thread of the bore 10, as shown.

[0023] The control valve 1 has an axial pressure connection 41 at the camshaft-side axial end of the valve housing 2, through which hydraulic fluid can be supplied from a central axial hydraulic fluid channel 11 in the camshaft 7. The latter can be pressurized with hydraulic fluid from a pressure source (not shown). The hydraulic fluid used is preferably engine oil from the engine oil circuit of the internal combustion engine.

[0024] Furthermore, an axial drain connection 42 is formed at the axial end of the control valve 1 facing away from the camshaft 7, via which hydraulic fluid can be discharged from the control valve 1 in a throttled manner.

[0025] The pressure port 41 communicates with an annular channel 14 which is axially delimited on the outer diameter of the control piston 6 by two control flanks 12, 13. Depending on the axial control position of the control piston 6, the control ports 3, 4 on the valve housing 2 for connecting the hydraulic medium to the camshaft adjuster 5 can be closed or opened via the control flanks 12, 13. Accordingly, hydraulic medium is supplied to the camshaft adjuster 5 at the respectively open control port 3, 4 and discharged from the camshaft adjuster 5 at the respectively closed control port 3, 4. The inflow and outflow of hydraulic medium into and out of the camshaft adjuster 5 via the control valve 1 at the control ports 3, 4.The camshaft adjuster 5 allows the rotational phase position between the camshaft 7 and a crankshaft of the internal combustion engine (not shown) that drives the camshaft adjuster 5 to be adjusted according to the engine's earlier or later valve timing. A center position of the control piston 6 between the positions for setting earlier or later valve timing is also possible.

[0026] In the exemplary control position of the control piston 6, the control port 3 is open and communicates with the annular channel 14, so that the camshaft adjuster 5 can be pressurized with hydraulic fluid from the pressure port 41 via the control port 3 and the annular channel 14. In contrast, the connection of the annular channel 14 to the control port 4 is blocked by the control flank 13 on the control piston 6, so that the control port 4 is depressurized. At the same time, the control port 4 is open to the interior of the valve housing 2 and communicates at the open camshaft-side axial end 15 of the control piston 6 with the hollow cylindrical cavity 16 within the latter.

[0027] As a result, the hydraulic fluid flowing out of the camshaft adjuster 5 at the control connection 4 reaches the interior of the valve housing 2 and flows in the cavity 16 inside the control piston 6 in an axial direction, so that it can exit through outlet openings 17 arranged at the free axial end of the control piston 6 into a hydraulic fluid reservoir 18 formed inside the valve housing 2. The cavity 16 in the control piston 6 serves for the axial hydraulic fluid connection to the hydraulic fluid reservoir 18. In the control valve 1, the flow of the hydraulic fluid flowing out of the camshaft adjuster 5 at the control connection 4 into the hydraulic fluid reservoir 18 is indicated by arrows.

[0028] The hydraulic fluid reservoir 18 is located in the axial end of the valve housing 2 facing away from the camshaft 7, which is axially extended for this purpose. It thus forms a hollow cylindrical additional hydraulic fluid chamber in which the hydraulic fluid exiting the outlet openings 17 at the free end of the control piston 6 is collected and temporarily stored.

[0029] The hydraulic fluid exiting the outlet openings 17 flows radially outward due to the centrifugal forces acting during operation. When the hydraulic fluid reservoir 18 is sufficiently filled, the hydraulic fluid flows out through the drain connection 42. The drain connection 42 is formed as a throttled drain by an orifice 19 with an orifice opening 20. The orifice 19 is designed as a cover that seals the valve housing 2 at the end facing away from the camshaft 7, except for the orifice opening 20, in a hydraulic fluid-tight manner. The orifice 19 can be simply screwed axially as a cover with an internal thread 21 onto an external thread 22 of the valve housing 2, as shown.

[0030] The hydraulic fluid reservoir 18 is defined as an additional hydraulic fluid chamber in the extended valve housing 2, radially defined by the latter and axially defined by the orifice 19. In the other axial direction, a retaining ring 23 inserted in a groove on the inner diameter of the valve housing 2 defines the hydraulic fluid reservoir 18. The control piston 6 is guided centrally through the retaining ring 23 and projects into the hydraulic fluid reservoir 18 with the outlet openings 17 formed at its free end.

[0031] The retaining ring 23 also serves as an axial end stop 24 for the control piston 6 in the control position shown. It also secures a bushing 25 arranged coaxially in the valve housing 2, on whose inner diameter the control piston 6 is axially guided. The bushing 25 is overmolded on its outer diameter with plastic 26 for attachment to the inner diameter of the valve housing 2. Radial through-openings 27, 28 and 29, 30 corresponding to the control connections 3, 4 are provided in the bushing 25 and in the plastic 26. They serve to connect the hydraulic fluid to the interior of the bushing 25, in particular to the annular channel 14 on the outer diameter of the control piston 6 for supplying hydraulic fluid to the camshaft adjuster 5.

[0032] To actuate the control piston 6, a plunger 32 actuated by an actuating unit 31 is preferably provided. The latter is guided axially through the orifice 20 for actuating contact with the control piston 6 and projects into the hydraulic fluid reservoir 18. The hydraulic fluid collected and temporarily stored in the hydraulic fluid reservoir 18 can exit axially from the valve housing 2 in a throttled manner through the radial annular gap S between the outer diameter d of the plunger 32 and the inner diameter D of the orifice 20. With a predetermined outer diameter of the plunger 32, the escaping hydraulic fluid flow at the throttled outlet 42 can be easily adjusted to suit the operating conditions using the inner diameter D of the orifice 20 alone. The actuating unit 31 is preferably designed as an electromagnet with an axially displaceable armature 33, by means of which the plunger 32 can be displaced.By energizing the actuating unit 31, the control piston 6, in actuating contact with the plunger 32, can be displaced from the illustrated position in the image plane to the right against the spring force of the return spring means 34 arranged in the valve housing 2. After the plunger 32 has been returned, the control piston 6 can be returned to its initial position by the spring force of the preloaded return spring means 34.

[0033] In the area of ​​the orifice 19 screwed onto the extended end of the valve housing 2, a funnel-shaped hydraulic fluid guide element 35 is arranged coaxially on the outside and fixedly connected to a magnet housing 37 of the actuating unit 31. With its funnel-shaped, widened free end 38, it encompasses the valve housing 2 radially outward in the area of ​​the screwed orifice 19 and the drain connection 42 throttled at the orifice opening 20.

[0034] A second hydraulic fluid guide element 36, which is connected in a rotationally fixed manner to the camshaft adjuster 5, surrounds the first hydraulic fluid guide element 35 with its funnel-shaped, tapered free end 39 radially outwardly, starting from the free end 38 of the same. Consequently, the hydraulic fluid flowing out of the control valve 1 at the throttled outlet connection 42 can be collected by the first hydraulic fluid guide element 35 and, by the action of the gravitational force g indicated by an arrow, can be returned to the funnel-shaped, widened free end 38. There, it exits into the second hydraulic fluid guide element 36 in a radially outward direction. At the inner circumference, which widens in a funnel shape towards the camshaft adjuster 5, the hydraulic fluid is guided further radially outwards towards the cam adjuster 5 by the centrifugal forces acting during operation, into a hydraulic fluid reservoir 40 connected to the cam adjuster and the second hydraulic fluid guide element 36.From there, it can flow directly into the camshaft adjuster 5 without pressure. This allows for a direct, pressureless radially outer hydraulic fluid return to the camshaft adjuster 5. List of reference symbols.

[0035] control valve

[0036] valve housing

[0037] Control connection

[0038] Control connection

[0039] Camshaft adjuster

[0040] control piston

[0041] camshaft

[0042] Rotation and center axis central mount

[0043] drilling

[0044] Hydraulic fluid channel

[0045] Control flank

[0046] Control flank

[0047] Ring channel axial end

[0048] cavity

[0049] Exit opening

[0050] Hydraulic fluid reservoir, hydraulic fluid chamber

[0051] aperture

[0052] aperture

[0053] internal thread

[0054] external thread

[0055] Retaining ring

[0056] End stop

[0057] socket

[0058] plastic

[0059] passage opening

[0060] passage opening

[0061] passage opening

[0062] passage opening

[0063] Actuator

[0064] pestle

[0065] anchor

[0066] Return spring means first hydraulic fluid guide element 36 second hydraulic fluid guide element 37 magnet housing

[0067] 38 End 39 End

[0068] 40 Hydraulic fluid reservoir 41 Pressure connection

[0069] 42 throttled drain connection d outer diameter D inner diameter

[0070] S Annular gap g Gravity

Claims

Patent claims 1. Hydraulic control valve (1) for a camshaft adjuster (5) for variable valve control of an internal combustion engine, comprising a valve housing (2) with control connections (3, 4) for the inflow and outflow of hydraulic fluid into and out of the camshaft adjuster (5) and a control piston (6) which is displaceable in the valve housing (2) for controlling the inflow and outflow of hydraulic fluid at the control connections (3, 4), wherein a hydraulic fluid reservoir (18) is provided in the valve housing (2) for collecting and temporarily storing the hydraulic fluid flowing out of the camshaft adjuster (5) at one of the control connections (3, 4), and an outlet connection (42) is provided for discharging the collected and temporarily stored hydraulic fluid from the valve housing (2), characterized in that the outlet connection (42) is throttled.

2. Hydraulic control valve according to claim 1, characterized in that the drain connection (42) is an orifice (19) with an orifice opening (20).

3. Hydraulic control valve according to claim 2, characterized in that the orifice (19) is designed as a cover which closes the valve housing (2) at one end up to the orifice opening (20) in a hydraulic-tight manner.

4. Hydraulic control valve according to claim 2 or 3, characterized in that the hydraulic fluid reservoir (18) is formed in an extended end of the valve housing (2) as an additional hydraulic fluid chamber delimited by the latter and the orifice (19).

5. Hydraulic control valve according to one of the preceding claims, characterized in that the hydraulic fluid reservoir (18) communicates with the one control connection (3, 4) on the valve housing (2) via a hydraulic fluid connection (16) formed in the control piston (6) and opening into the hydraulic fluid reservoir (18).

6. Hydraulic control valve according to one of the preceding claims, characterized in that the control piston (6) projects with a free end (17) into the hydraulic fluid reservoir (18).

7. Hydraulic control valve according to one of claims 2 to 6, characterized in that for actuating the control piston (6) a control unit (31) An actuatable plunger (32) for setting contact with the control piston (6) is guided through the aperture (20) into the hydraulic fluid reservoir (18).

8. Camshaft adjustment arrangement with a camshaft adjuster (5) for variable valve control of an internal combustion engine, with at least one hydraulic control valve (1) according to one of the preceding claims.

9. Camshaft adjustment arrangement according to claim 8, characterized in that the hydraulic control valve (1) is arranged coaxially to the rotational and central axis (8) of the camshaft adjuster (5) in a central receptacle (9) of the latter, connected to it in a rotationally fixed manner, and is designed with a throttled drain connection (42) for discharging hydraulic fluid collected and temporarily stored in a hydraulic fluid reservoir (18) in the control valve (1), wherein in the region of the drain connection (42) there is a stationary hydraulic fluid guide element (35) which guides the hydraulic fluid flowing out at the drain connection (42) back into the camshaft adjuster (5).

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