This disclosure is directed to the field of proportional directional valves, which can be used as control valves, especially for controlling camshaft adjusters. Camshaft adjusters are used to control the operation of a combustion engine by specifically affecting the charge exchange: an adjustment of the phase position of the camshaft changes its position in relation to the phase position of the crankshaft; as a result, it is possible to move the opening and closing times of the gas exchange valves to an earlier or later point in time of the continuous cycle. Control valves have multiple switching positions, by adjusting the course of the pressure medium path between inlet and outlet, and depending on the switching position, the pressure medium flow exerts a force on the camshaft adjuster, causing an adjustment to a certain position.
DE 10 2012 201 567 A1 shows a control valve for a camshaft adjuster having a control valve housing designed in the form of a central screw, which has a screw shaft, a tubular section and a screw head, as well as a hollow cylindrical control piston that can be moved inside a valve housing. Inside the piston cavity there is a hydraulically unlockable check valve releasing a first pressure medium line in flow direction, which check valve has a closing section with a sealing surface, and the inlet opening can be closed in reverse direction. Via the inlet connection and a channel formed axially on the valve housing, the pressure medium flows into one of the supply ports A or B, which supply the working chambers of a hydraulic camshaft adjuster with pressure medium.
The discharge of the pressure medium from the supplied working chambers of the camshaft adjuster is initially also carried out via the supply ports A and B into a respective first and second control groove formed on the control piston. The discharge is carried out either directly via the first control groove or indirectly via the second control groove, the piston cavity and the first control groove. With the pressure medium discharged via the outlet connection, a volume accumulator is fed, which is integrated in the camshaft adjuster.
It is the objective of this disclosure to improve a control valve and a camshaft adjuster with such a control valve.
Accordingly, this disclosure provides a control valve for a camshaft adjuster, in which control valve includes a valve sleeve having one or more inlet openings, two supply openings and an outlet opening and a control piston guided in the valve sleeve, and the piston, together with the valve sleeve and control edges arranged on the control piston, forms three annular ducts. A fluid-conducting connection between an inlet opening P and a supply opening A can be controlled via an annular channel A; a fluid-conducting connection between an inlet opening P or a further inlet opening, which is axially spaced from the inlet opening P, and a supply opening B can be controlled via an annular channel B. The annular channel A and the annular channel B enclose a central annular channel, via which a fluid-conducting connection between the supply opening A and the outlet opening C, as well as between the supply opening B and the outlet opening C, can be controlled.
Outlet openings provide a controllable connection between the supply openings and the surrounding area of the control valve. In this way, the pressure medium is returned to the hydraulic fluid circuit of the combustion engine. Usually, the discharge of the pressure medium is carried out via separate outlet openings of the control valve, each of which is attached to one of the supply openings. Alternatively, the pressure medium flowing from multiple supply openings can be discharged via a mutual outlet opening. However, the pressure medium path described requires in well-known manner a mutual pressure medium line through the piston cavity, which therefore can no longer be used for other purposes.
According to an embodiment, a mutual outlet opening can be achieved without having to guide the discharging pressure medium via the piston cavity: the discharge can be carried out directly via a mutual, central annular channel via the arrangement of the outlet opening between the supply openings. In an embodiment, it is possible to produce a direct connection between the supply openings A and B to the outlet opening C. Thus, the discharge of the pressure medium is only subject to minor pressure losses.
Outlet opening, inlet opening(s) and supply openings are respectively arranged at an axial position. At each respective axial position, multiple openings can be arranged along the circumference.
In an embodiment, the control piston comprises a piston cavity, wherein the central annular channel can be directly connected with the outlet opening C, the annular channel A can be directly connected with the supply opening A, and the annular channel B can be directly connected with the supply opening B. One of the annular channels A or B can be directly connected with the inlet opening P, wherein the other one of the annular channels A or B can be indirectly connected via the cavity of the control piston with the inlet opening P (indirect connection). Via the proposed embodiment, it is possible to implement a control valve, which shows advantages especially with a view to the axial space requirements.
In an embodiment, the indirect connection occurs via an annular supply channel formed in the piston cavity. Said annular supply channel is indirectly connected via piston openings A and B with the annular channel A and the annular channel B. In this way, a connection can be produced in a constructively simple manner between the annular channels A and B, which are separated by the central annular channel.
In an embodiment, the annular supply channel is formed between the inside surface of the control piston and the outside surface of a tubular piston insert. The proposed further development allows for a cost-effective production of the control piston.
In an embodiment, the piston insert basically seals the annular supply channel toward the surrounding area. At the same time, a space formed between valve sleeve and control piston is connected with the surrounding area via a channel formed in the piston insert. For example, in an embodiment, the channel allows for ventilation of the space, which is enclosed by the floor of the control piston and the inside surface of the valve sleeve. In addition, it is possible that pressure medium, which has entered said space due to leakage, is released to the surrounding area.
In a further embodiment, the valve sleeve is designed in the form of a central screw. In this way, it is possible to produce a connection between the control valve and a camshaft as receiving component. In addition, the control valve can also be used to attach further components to the camshaft, for example, the rotor of a hydraulic camshaft adjuster.
In an embodiment, the valve sleeve comprises a plastic injection molding. Via the plastic injection molding, a guide for the pressure medium can be implemented, for example, by providing longitudinal channels between valve sleeve and a component receiving the valve sleeve. Therefore, the axial position of inlet openings, outlet openings and supply openings does not have to correspond to the axial position of openings, which give access to further pressure medium lines on the receiving component.
In a further embodiment, the valve sleeve is arranged in a central screw. At the same time, the plastic-coated valve sleeve is accepted by the central screw. Preferably, the inlet opening is connected via an axial channel formed in the plastic injection molding with an inlet connection formed on the central screw. As a result, pressure medium can be supplied via a camshaft bearing and the camshaft, in that pressure medium enters the central screw in axial or radial manner via the inlet connection, passes in axial direction through a check valve and then flows via the axial channel and via the inlet opening into the annular channel. In addition, a design in the form of a central screw shows the above-mentioned advantages.
The objective is also achieved by a camshaft adjuster having a stator, a rotor and a control valve in one of the embodiments described above. The control valve is designed in the form of a central valve, wherein the supply opening A is connected with a working chamber A formed between stator and rotor, and the supply opening B is connected with a working chamber B formed between stator and rotor. The outlet opening C is connected with a volume accumulator, wherein the volume accumulator can be connected with working chamber A, working chamber B and via an outlet connection with the surrounding area.
The main components of a camshaft adjuster in the design of a vane cell adjuster involves a stator and a rotor. The Stator can be connected in torque-proof manner with a drive wheel and driven via a traction drive by the crankshaft. The rotor forms the drive element. Rotor and stator include a pressure chamber, which is divided via a wing formed on the rotor in working chambers A and B. Working chamber A and B can be connected with the supply ports A and B of a control valve: pressurization via a pressure medium results in a relative rotation of the rotor in relation to the stator.
A volume accumulator, which is supplied via the outlet connection C, can be arranged in the camshaft adjuster or in an area between camshaft adjuster and control valve. If low pressure occurs in one of the working chambers, pressure medium can flow from the volume accumulator via check valves into the working chamber and offset the low pressure. The volume accumulator can have a further outlet connection to a reservoir (tank).
Various embodiments are now described in more detail with reference to the drawings. Functionally equivalent elements of the embodiments described are marked with the same reference signs.
The control piston 4 is guided inside a valve sleeve 13. The valve sleeve 13 comprises an internal component 14 and an external component 15. The internal component 14 is produced from a metallic material and is surrounded by an external plastic component. 15. Both components are designed in the form of a sleeve or hollow cylinder. The external sleeve-shaped component 15 is produced as an injection-molded part and the internal sleeve-shaped components 14 as an insert, which is overmolded during the injection molding process of the external component.
On its outside surface, the control piston 4 has four sections with expanded diameter, which include three sections with a reduced diameter. Together with the inside surface of the valve sleeve 13, said sections form an annular channel A 16, an annular channel B 17 and a central annular channel 18. To control a camshaft adjuster, the control piston 4 can assume two switching positions, which are marked by the actual course of possible pressure medium paths.
A switching position is implemented via a setting device (not shown), which usually involves an electromagnetic actuator. A push rod connected to an anchor of the electric magnet is brought in contact with an actuation surface at the front end of the control piston 4. As a result, the force exerted on the anchor is transferred via the push rod to the control piston 4, thus causing an axial movement against the force of a spring 19: the annular channel A 16 can be moved into the axial position of the supply opening A 20. Therefore, the annular channel B 17 can be brought into the axial positions of the supply opening B 21 and the inlet opening P 22. The central annular channel 18 can be brought into the axial positions of the supply opening A 20 and the supply opening B 21.
In this way, the first switching position shown in
Therefore, the annular supply channel 26 is formed between the inside surface of the control piston 4 and the outside surface of a tubular piston insert 25. In this way, it is possible to produce an indirect connection via an annular supply channel 26 formed in the piston cavity 28. The annular supply channel 26 is directly connected via the piston openings A and B 27, 24 with the annular channel A 16 and the annular channel B 17. In addition, the piston insert 27 basically seals the annular supply channel 26 toward the surrounding area, wherein a space 28 formed between valve sleeve and control piston is connected with the surrounding area via a channel 29 formed in the piston insert 27.
In addition, the volume accumulator 38 can be brought in fluid-conducting connection with the working chamber A 36 and the working chamber B 37. For this purpose, hydraulic channels are located in the chamber walls 33 of the stator. Check valves are used to prevent pressure medium from flowing from one of the working chambers 36, 37 to the volume accumulator. The volume accumulator 38 also has an outlet, which has the purpose of supplying hydraulic fluid to a reservoir (tank).
Number | Date | Country | Kind |
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102015218072.7 | Sep 2015 | DE | national |
This application is a continuation of U.S. application Ser. No. 15/759,392 filed Mar. 12, 2018, which is a U.S. National Phase of PCT/DE2016/200409 filed Sep. 1, 2016, which claims priority to DE 102015218072.7 filed Sep. 21, 2015, the entire disclosures of which are incorporated by reference herein.
Number | Date | Country | |
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Parent | 15759392 | Mar 2018 | US |
Child | 16526249 | US |