Control valve

Abstract

Control valve (2) with a valve housing (4), a control piston (6) which is arranged in the valve housing (4) and is displaceable in an axial direction (X), a check valve (14) which is formed by a first orifice (20) with a first orifice opening (22) which can be closed by a closing element (24), an inlet port (P) via which the control piston (6) can be pressurized with hydraulic oil, a filter (12) which is arranged between the check valve (14) and the inlet port (P), wherein a second orifice (21) with a second orifice opening (23) is arranged between the first orifice (20) and the inlet port (P), wherein the second orifice opening (23) is arranged circumferentially offset to the first orifice opening (22).

Description

Field of the invention

[0001] The invention relates to a control valve with a valve housing having a control piston which is arranged in the valve housing and is displaceable in an axial direction, with a check valve which is formed by a first orifice with a first orifice opening which can be closed by a closing element, with an inlet connection (P) via which the control piston can be pressurised with pressurised oil, and with a filter which is arranged between the check valve and the inlet connection.

[0002] In internal combustion engines, camshafts are used to actuate the gas exchange valves. Camshafts are mounted in the internal combustion engine in such a way that the cams mounted on them engage cam followers, such as bucket tappets, rocker arms, or rocker arms. When a camshaft is rotated, the cams roll on the cam followers, which in turn actuate the gas exchange valves. The position and shape of the cams thus determine both the opening duration and opening amplitude, as well as the opening and closing times of the gas exchange valves.

[0003] Many internal combustion engines have a variable valve train. On the one hand, the valve lift and valve opening duration should be variable, even up to the complete shutdown of individual cylinders. Concepts such as switchable cam followers or electro-hydraulic or electric valve actuation are provided for this purpose. Furthermore, it has proven advantageous to be able to influence the opening and closing times of the gas exchange valves while the internal combustion engine is running. It is particularly desirable to be able to influence the opening and closing times of the intake and exhaust valves separately, for example in order to specifically set a defined valve overlap. By adjusting the opening and closing times of the gas exchange valves depending on the current engine map area, for example the current speed orthe current load, the specific fuel consumption can be reduced, the exhaust emissions can be positively influenced, and the engine efficiency, maximum torque and maximum power can be increased.

[0004] The described variability of the gas exchange valve timing is achieved by a relative change in the phase position of the camshaft to the crankshaft. The camshaft is usually connected to the crankshaft via a chain, belt, gear drive, or equivalent drive concepts. A device for changing the timing of an internal combustion engine, a camshaft adjuster, is installed between the chain, belt, or gear drive driven by the crankshaft and the camshaft. This device transfers the torque from the crankshaft to the camshaft. This device is designed in such a way that the phase position between the crankshaft and camshaft is securely maintained during operation of the internal combustion engine and, if desired, the camshaft can be rotated within a certain angular range relative to the crankshaft.

[0005] In internal combustion engines with one camshaft each for the intake and exhaust valves, these can each be equipped with a camshaft adjuster. This allows the opening and closing times of the intake and exhaust gas exchange valves to be shifted relative to each other and the valve overlap to be precisely adjusted.

[0006] The seat of modern camshaft adjusters is usually located at the drive end of the camshaft. However, the camshaft adjuster can also be mounted on an intermediate shaft, a non-rotating component, or the crankshaft. It consists of a drive gear driven by the crankshaft and maintaining a fixed phase relationship with it, an output gear connected to the camshaft, and an adjustment mechanism that transfers the torque from the drive gear to the output gear.

[0007] In the case of a camshaft adjuster not mounted on the crankshaft, the drive wheel can be designed as a chain, belt, or gear and is driven by the crankshaft via a chain, belt, or gear drive. The adjustment mechanism can be operated electrically, hydraulically, or pneumatically.

[0008] A preferred embodiment of the hydraulically adjustable camshaft adjuster is the rotary piston adjuster. In these, the drive wheel is connected to a stator in a rotationally fixed manner. The stator and a rotor are arranged concentrically to one another, wherein the rotor is connected to a camshaft, a camshaft extension or an intermediate shaft in a force-fitting, form-fitting or material-locking manner, for example by means of a press fit, a screw or welded connection. A plurality of cavities are formed in the stator, spaced apart in the circumferential direction, which extend radially outwards from the rotor. The cavities are delimited in the axial direction by side covers in a pressure-tight manner. A vane connected to the rotor extends into each of these cavities and divides each cavity into two pressure chambers. By specifically connecting the individual pressure chambers to a hydraulic pump orWith a hydraulic fluid outlet, the phase of the camshaft relative to the crankshaft can be adjusted or maintained.

[0009] To control the camshaft adjuster, sensors record engine parameters such as load and engine speed. This data is fed to an electronic control unit, which, after comparing the data with a characteristic map of the internal combustion engine, controls the inflow and outflow of pressure fluid to the various pressure chambers.

[0010] To adjust the phase position of the camshaft relative to the crankshaft, in hydraulic camshaft adjusters, one of the two opposing pressure chambers of a cavity is connected to a pressure pump, and the other to the tank. Pressurizing one chamber and relieving the pressure in the other chamber causes a displacement of the vane and thus a direct rotation of the camshaft relative to the crankshaft. To maintain the phase position, both pressure chambers are either connected to the pressure pump or disconnected from both the pressure pump and the tank.

[0011] The pressure medium flows to and from the pressure chambers are controlled by a control valve, usually a 4 / 3 proportional valve. A valve housing is provided with one connection each for the pressure chambers (working connection), one connection to the pressure medium pump, and at least one connection to a tank. An axially displaceable control piston is arranged within the essentially cylindrical valve housing. The control piston can be moved axially into any position between two defined end positions by means of an electromagnetic actuator, counter to the spring force of a spring element. The control spool is also provided with annular grooves and control edges, whereby the individual pressure chambers can be connected either to the pressure medium pump or to the tank. A position of the control piston can also be provided in which the pressure medium chambers are separated from both the pressure medium pump and the pressure medium tank.

[0012] Dirt particles may be present within the pressure fluid circuit, which can be carried into the valve by the pressure fluid. Such dirt particles can arise during machining of the engine block or due to wear during operation of the internal combustion engine. If these particles enter the control valve, there is a risk that they will damage the valve's control edges or cause the control piston to jam within the valve housing. As a result, the phase position of the camshaft relative to the crankshaft can no longer be changed, which has a negative impact on the engine's fuel consumption, power, torque, or exhaust emissions.

[0013] Devices for varying the control times are known in which the penetration of dirt particles into a hydraulic proportional valve is prevented by installing pressure filters between the pressure pump and the pressure connection. For example, US Pat. No. 6,382,148 B1 describes an annular oil filter arranged in an annular groove of the valve housing, the base of the annular groove being provided with openings corresponding to the P-connection of the valve. The annular pressure filter is provided with an axially extending interruption at one point, whereby two circumferential ends of the pressure filter face each other. The circumferential ends of the pressure filter are provided with means for positive fastening. During assembly, the open filter is inserted into the annular groove, and the circumferentially open ends are connected to one another using the positive locking means.

[0014] A disadvantage of this design is the high effort required to install the filter on the valve housing. If the filter is improperly installed, there is a risk that the filter could become jammed between the control valve and the valve housing during installation, resulting in damage or even shearing off.

[0015] During operation of the internal combustion engine, alternating torques occur on the camshaft, which are transmitted as pressure surges via the pressure chambers to the hydraulic system of the camshaft adjuster. To prevent the transmission of such pressure surges, hydraulically releasable check valves are used in the pressure medium supply of the camshaft adjuster. DE 10 2010 026 853 A1 describes such a check valve that integrates a flat closing element and a filter into an injection-molded housing. Due to the design of the flat closing element, the check valve is low in mass and reacts comparatively quickly. The disadvantage of this integration of closing element and filter is that the aforementioned pressure surges cannot be completely eliminated, but rather, as pressure fluctuations, stress the filter and can damage it. Small orifice plates in particular lead to strong local flow, which can strain the filter fabric.Under particularly unfavorable operating conditions, additional oscillations can develop, which place further strain on the filter or, if cavitation bubbles collapse due to backlash moments, can even destroy it. Summary of the invention

[0016] The invention is therefore based on the object of avoiding these described disadvantages.

[0017] According to the invention, this object is achieved in that a second orifice plate with a second orifice opening is arranged between the first orifice plate and the inlet connection, wherein the second orifice opening is arranged offset in the circumferential direction to the first orifice opening. The first orifice plate thus forms the abutment for the closing element. The second orifice opening is arranged offset to the first orifice opening. As a result, pressure fluctuations introduced via the inlet initially act on the second orifice plate and are reflected outside the second orifice plate. The portion of the pressure wave that can propagate through the second orifice plate is then reflected by the first orifice plate. Since the free flow to the orifice plate is reduced in this way, the associated load acting on the filter is reduced.The pressure drop across the filter mesh is reduced, which in turn leads to lower flexural stress on the filter. The filter retains particles that could impair the function of the control valve. It can be made of wire mesh. The invention reduces the risk of filter mesh failure.

[0018] If the filter is positioned between the two orifices, only a portion of the filter mesh is exposed to these pressure fluctuations. Pulsations in the supply pressure, such as oscillations in the camshaft adjuster, still push the oil column back and forth in the area of ​​the screen, but it doesn't impact the screen across its entire cross-section. This reduces the oscillation load on the filter, increasing its service life.

[0019] The filter is preferably located downstream of the two orifices in the inlet flow direction. This allows almost all oscillation to be kept away from the filter. Only that portion of the oil flow that is reflected at least once, and preferably multiple times, by the orifices, and whose pressure peaks are significantly reduced due to the longer path, partial superposition, and internal fluid friction, reaches the filter.

[0020] The filter is preferably arranged between the pressure medium connection and the working connections. Advantageously, the control piston is hollow, the interior of the control piston communicates with one of the working connections, depending on its position, and the filter is arranged inside the control piston. The filter is designed such that it is held in position by force-locking or positive locking means. By arranging the filter within the control piston, no forces act on it during installation of the control valve into the valve seat. Damage during assembly is thus eliminated.

[0021] Axial stops can be incorporated within the control piston, allowing the filter to be positioned reliably during the assembly process. Alternatively, the filter can also be pressed in using a displacement-controlled method.

[0022] In a further development of the invention, the second orifice is larger than the first orifice on the check valve. This prevents flow losses.

[0023] In a subsequent design, the first and second apertures do not overlap in the axial direction. This ensures that at least two reflections of a pressure wave must occur before the pressure wave passes through both apertures.

[0024] In a further embodiment of the invention, the valve housing has a central axis, with the first orifice being arranged eccentrically relative to it. This allows the two orifices to be as far apart as possible in the axial direction, which promotes damping. Furthermore, the eccentric arrangement allows the closing element to be connected via a long closing element arm. A long closing element arm allows for a softer spring action of the closing element, ensuring lower closing forces and thus further reduced pressure peaks.

[0025] In a further development, the closing element is connected to a check valve housing by a closing element arm. The length of the arm is preferably greater than the greatest radial distance of the closing element from the injection-molded housing. In a further embodiment, the closing element arm connects the closing element to the check valve housing in the form of a partial spiral.

[0026] The check valve housing is preferably designed as an injection-molded housing in which the closing element, the first orifice plate, and the filter are arranged. Together, they form an injection-molded assembly. Preferably, the second orifice plate is also integrated into the injection-molded assembly, so no separate assembly is required.

[0027] In another embodiment, the filter is designed as a fabric insert that covers the entire interior of the valve housing. This allows the filter to be integrated particularly easily into the check valve housing. The entire unit is thus easy to assemble. Preferably, the second orifice plate is also incorporated into the check valve housing.

[0028] Alternatively, the filter covers only part of the interior of the check valve housing, ensuring that one of the apertures is completely covered. This allows the filter to be integrated into the second aperture, eliminating the need to attach it to the check valve housing. One embodiment also allows for the filter to be dispensed with and simply arrange the two apertures axially one behind the other.

[0029] In a further development, several additional orifices can be provided in addition to the first orifice. This allows pressure loads to be further reduced. The additional orifices can be spaced from the first orifice or from each other by spacer rings.

[0030] In another embodiment, the filter is axially movable within the valve housing. For this purpose, it can be integrated, for example, into a check valve housing, which forms axial stops for the filter. This allows the filter to move axially within a limited range during pressure peaks.

[0031] In a further embodiment, the filter has an annular enclosure. This can be made of metal or plastic and connects the filter to the valve housing or to a check valve housing. Within the enclosure, the filter can have a profiled filter mesh. The filter mesh can, for example, undulate concentrically. Individual parts of the filter mesh can protrude axially from the center plane of the suspension. This allows the filter mesh itself to absorb vibrations from the oil column, making it softer and more resilient due to this internal degree of freedom.

[0032] Preferably, a control valve according to the invention is part of a camshaft adjuster. It is particularly suitable for oil-actuated camshaft adjusters (oil pressure actuated), which are used in internal combustion engines with high camshaft torques and relatively low supply pressures.

[0033] In an advantageous embodiment of the invention, the interior of the control piston communicates with the pressure medium connection via second openings in the jacket surface of the control piston, regardless of its position, the filter is designed in the form of a cylinder jacket surface and arranged in the region of the second openings.

[0034] In this embodiment, a plurality of axially spaced annular grooves are formed on the outer surface of the substantially cylindrical valve housing. The groove bases of the annular grooves are provided with a plurality of openings, whereby each annular groove forms a connection of the valve. A control piston, which is also substantially cylindrical, is mounted within the valve housing and can be axially displaced within the valve housing via an adjusting mechanism. The outer surface of the control piston is also provided with a plurality of axially spaced annular grooves, wherein one of the annular grooves is designed such that it communicates with the annular groove of the valve housing, which serves as a pressure medium connection, in any position of the control piston within the valve housing. This annular groove of the control piston communicates with the hollow interior of the control piston via openings introduced into its groove base.Pressure medium can now flow through the pressure medium connection in the valve housing into the annular groove of the control piston and from there into its interior. The interior of the control piston is connected via additional openings to another annular groove in its outer surface. This annular groove communicates with a first or second working port, depending on the axial position of the control piston within the valve housing. Short description of the drawings

[0035] Further features of the invention will become apparent from the following description and the drawings, which illustrate exemplary embodiments of the invention in simplified form. They show: Fig. 1 an axial section through a control valve with a valve insert according to a first embodiment, Fig. 2 a plan view of a check valve in plane I according to Fig. 1, Fig. 3 a plan view of a seat element of the check valve according to Fig. 2, Fig. 4 in an axial section an insert housing for a valve insert according to Fig. 1, Fig. 5 in an axial section the insert housing according to Fig. 4 with an integrated filter, Fig. 6 a schematic diagram of a check valve with a filter from a control valve according to the prior art, Fig. 7 a schematic diagram of a check valve with a filter and a further orifice according to a first control valve according to the invention, Fig. 8 a schematic diagram of a check valve with a filter and a further orifice according to a second control valve according to the invention, Fig. 9a a check valve housing with a filter for a control valve according to the invention, Fig. 9b the check valve housing according to Fig. 9a in rear view with a locking element, Fig. 9c an enlarged view of a locking element according to Fig. 9b, Fig. 10 an axial section through a control valve with a valve insert according to a second embodiment, Fig. 11 a longitudinal section through a check valve housing for a control valve according to the invention, in which a filter is arranged and Fig. 12 an enlarged schematic diagram of a filter in cross section for a control valve according to the invention. Detailed description of the drawings

[0036] In Fig. 1 shows a control valve 2 which is designed as a central valve and is inserted into a central bore of a rotor of a hydraulic camshaft adjuster (not shown in detail here). The control valve 2 comprises a hollow, cylindrical valve housing 4 with a valve body (not shown in detail here, but only in Fig. 10 shown inlet connection P for a pressure medium such as oil, wherein a supply direction of the oil is indicated by the arrow P. In addition, two working connections A, B for the counter-rotating pressure medium chambers in the rotor of the camshaft adjuster and a drain connection T are formed in the valve housing 4. A control piston 6, which is spring-loaded by a spring 9, is guided axially within the valve housing 4, wherein, depending on its position, the inlet connection P is fluidly connected to one of the working connections A, B, while the other working connection A, B is connected to the drain connection T. In the area of ​​a pressure medium line 7 between the inlet connection P and the working connections A, B, a valve insert 8a is arranged.

[0037] The valve insert 8a comprises an insert housing 10 in which a filter 12 and a check valve 14 are arranged one behind the other downstream. The filter 12 comprises a filter fabric 16 and a filter frame 18 for clamping the filter fabric 16. A cavity for the pressure medium is formed between the filter fabric 16 and the check valve 14. In the illustrated embodiment, the check valve 14 is composed of a first orifice 20 with a first orifice opening 22 for the pressure medium and a closing element 24. The valve insert 8a is made of steel and is attached to an outer side of the valve housing 4 by flanging or bending. The insert housing 10 thus represents an extension of the valve housing 4, so that the valve insert 8a is an external valve insert.

[0038] The detailed structure of a first axially flat check valve 14 is shown in the Fig. 2 to 5. The locking element 24 is made of spring steel. The locking element 10 comprises three functional areas: a closure plate 26 for closing the opening 22 in the seat element 20, a resilient bending web 28, and two fixing arms 30a for fixing the locking element 24 to the seat element 20. The shape of the fixing arms 30 follows the contour of the seat element 20, so that the fixing arms 30 are arcuate in the illustrated embodiment.

[0039] The seat element 20 has a support surface on which the closing element 24 rests in a closed position of the check valve 14, thereby covering the opening 22. The shape of the closure plate 26 is adapted to the shape of the opening 22.

[0040] The pressure medium, which is introduced into the control valve 2 through the working port P, enters the pressure medium line 7 and passes through the filter 12. Under the pressure force of the pressure medium, the closure plate 26 lifts off the seat element 20, so that the opening 22 is opened and the pressure medium can flow in the direction of the working ports A, B.

[0041] If a pressure surge occurs against the flow direction or if the pressure medium flows back, the closure plate 26 of the check valve 14 is pressed against the support surface 32 so that the opening 22 is closed and further flow back of the pressure medium through the opening 22 is prevented.

[0042] In the illustrated embodiment, the support surface 34 is made of steel and is formed in one piece with the insert housing 10. The insert housing 10 thus forms the seat element 20 for the check valve 14. A collar 36, which is L-shaped in axial section and provided with openings 38, is formed around the support surface 34. The openings 38 serve to inject a plastic from which the filter frame 18 is formed. The seat element 20 and the filter fabric 16 are overmolded with the material of the filter frame 18. Since the filter frame 18 is an injection-molded part which extends on both sides of the L-shaped collar 36 and is thus inseparably connected to the insert housing 10, the insert housing 10, the filter frame 18, the filter fabric 16 and the seat element 20 of the check valve 14 form a non-disassemblable unit. The prefabricated assembly 40 is completed by also attaching the locking element 24 to the seat element 20.The assembly 40 is then coupled in this form to the valve housing 4.

[0043] The Fig. Figures 6 to 8 describe the functioning of the invention. Fig. 6 shows an arrangement of a check valve 14 and a filter 12 according to the prior art and thus without an additional orifice 21. Pressure waves can act unhindered from the first orifice 20 onto the filter 12 and damage it. Fig. Figure 7 shows an arrangement according to the invention comprising a filter 12, a first aperture 20 with a first aperture 22, and a second aperture 21 with a second aperture 23. Both apertures 22, 23 are arranged offset from one another in the circumferential direction and do not overlap in the axial direction X. The oil flow, visualized by the summation arrow 33, is composed of several individual propagations 35, some of which arise from multiple reflections.

[0044] The first aperture 20 is spaced from the filter 12 by a first distance d1 and from the second aperture 21 by a second distance d2. The distances can be equal, as shown, but do not have to be identical. Preferably, the two apertures 20, 21 are combined with the filter 12 in a common insert housing 10.

[0045] Fig. 8 shows an alternative arrangement to Fig. 7, where the filter 12 is arranged between the two apertures 10, 21.

[0046] The Fig. 9a to 9c describe the detailed structure of a closing element 24 provided for a control valve 2 according to the invention. The closing element 24 is arranged in an insert housing 10 together with the filter 12. The closure plate 26 is connected to the insert housing 10 by a flexible web 28. The closure plate 26 is arranged eccentrically to the central axis M, and the flexible web 28 connects the closure plate 26 to the insert housing in a spiral shape. The spiral shape, instead of the shortest possible connection, allows for a longer spring travel, so that the spring force is reduced. As can be seen from Fig. As can be seen in Figure 9c, the locking element 24 can be connected to the insert housing 10 via fixing arms 30.

[0047] Fig. 10 shows a further control valve 2 according to the invention, which has the configuration shown in the schematic diagram of Fig. 7 shown structure is realized.

[0048] In Fig. Figure 11 shows another variant of an insert housing 10. It accommodates the filter 12, which has a filter frame 18 in which a filter mesh 16 is arranged. The filter frame 18, together with the filter mesh 16, is axially movable within the insert housing 10 to a limited extent, with clamps 39 providing axial security. This mobility allows pressure surges to be partially compensated.

[0049] Fig. Figure 12 shows a schematic diagram of a filter 12 that supports the effect of the invention. The filter 12 has a filter fabric 16 arranged outside the axial plane of the filter frame 18 and has a wave structure. The concentric wave structure, in turn, can compensate for pressure fluctuations within the filter fabric 16 and ensures a softer suspension. List of reference numbers 2 control valve 4 valve housings 5 Central axis 6 control pistons 7 Pressure medium line 8a,8b valve insert 9 spring 10 insert housings 12 filters 14 Check valve 16 filter fabrics 18 filter frames 20 first aperture 21 second aperture 22 first aperture 23 second aperture 24 locking element 26 locking plate 28 Bending bar 30 Fixing arm 33 Sum arrow 34 support surface 35 Single propagation 36 L-shaped collar 38 Opening 39 bracket 40 units A, B working connections d1 first distance d2 second distance P inlet connection T drain connection X axial direction QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 6 382 148 B1

[0013] DE 10 2010 026 853 A1

[0015]

Claims

[1] Control valve (2) with - a valve housing (4), - a control piston (6) arranged in the valve housing (4) and displaceable in an axial direction (X), - a check valve (14) formed by a first orifice (20) with a first orifice opening (22) which can be closed by a closing element (24), - an inlet connection (P) through which the control piston (6) can be pressurised with pressure oil, - a filter (12) arranged between the check valve (14) and the inlet connection (P), characterized by that a second orifice (21) with a second orifice opening (23) is arranged between the first orifice (20) and the inlet connection (P), wherein the second orifice opening (23) is arranged offset in the circumferential direction to the first orifice opening (22). [2] Control valve according to claim 1, characterized bythat the first and second apertures () do not overlap in the axial direction (X). [3] Control valve according to claim 1 or 2, characterized by that the valve housing (4) has a central axis (5) to which the first aperture (22) is arranged eccentrically. [4] Control valve according to claim 1 or 2, characterized by that the check valve (14) is designed as an insert assembly with an insert housing (10) in which the closing element (24), the orifices (20, 21) and the filter (12) are arranged. [5] Control valve according to one of the preceding claims, characterized by that the second aperture (21) is arranged between the first aperture (20) and the filter (12) or that the filter (12) is arranged between the two apertures (20, 21). [6] Control valve according to one of the preceding claims, characterized bythat the filter (12) has a filter fabric (16) which either completely covers only part of the interior of the valve housing (4) and also one of the apertures (22, 23) or which covers the entire interior of the valve housing (4). [7] Control valve according to one of the preceding claims, characterized by that a plurality of second orifices (21), each having at least one orifice opening (23), are arranged between the inlet connection (P) and the first orifice (20). [8] Control valve according to one of the preceding claims, characterized by that the filter (12) is axially movable in the valve housing (4). [9] Control valve according to one of the preceding claims, characterized by that the filter (12) has a filter frame (18) with a profiled filter fabric (16) within the filter frame (18). [10] Camshaft adjuster with a control valve (2) according to one of the preceding claims.

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