Control valve for a camshaft adjuster

Abstract

A control valve (4) for controlling pressure medium flows of a camshaft adjuster which includes a substantially hollow cylindrical valve housing (6), a control piston (12), which is guided axially displaceably inside the valve housing (6), and a non-return valve (22) which can be hydraulically released. In a region of a pressure medium inlet, the valve housing (6) includes a housing shaft (28) with an axial inflow bore (30) which widens in funnel-like manner towards the inlet side.

Claims

1. A control valve for controlling flows of pressurized medium of a camshaft adjuster, said control valve comprising: an essentially hollow cylindrical valve housing, a guided control piston movable in an axial direction inside the valve housing, a non-return valve that is releasable hydraulically; and a filter, the valve housing including, in an area of a pressurized medium supply, a housing shaft with an axial supply hole that includes a funnel portion formed by a sidewall that gradually widens in a funnel shape toward an inlet of the axial supply hole, wherein the filter is disposed entirely in the axial supply hole, wherein a base of the filter is positioned adjacent to the non-return valve, wherein the funnel portion abuts the base of the filter and extends past an outermost end of the filter, and wherein the filter extends coaxially with the axial supply hole and is spaced from the sidewall in a radial direction such that a gap is formed between the filter and the sidewall, and wherein the gap extends along an entire distance of the filter such that the filter does not contact the sidewall.

2. The control valve according to claim 1, further including a thread on an axial end of the housing shaft, and wherein a wall thickness of the housing shaft is decreased in an axial region between the non-return valve and the thread by a reduction of an outer diameter.

3. The control valve according to claim 1, further comprising a hollow pressurized medium guide insert positioned in a hollow space of the valve housing.

4. The control valve according to claim 3, wherein an outer diameter of the pressurized medium guide insert is adapted to an inner diameter of the valve housing hollow space.

5. The control valve according to claim 3, further comprising a hollow cylindrical control sleeve arranged inside the pressurized medium guide insert.

6. The control valve according to claim 5, wherein the guided control piston is positioned inside the hollow cylindrical control sleeve.

7. The control valve according to claim 6, further comprising a securing ring arranged in a groove of the valve housing, the securing ring preventing an axial sliding of the control piston the control sleeve, or the pressurized medium guide insert.

8. The control valve according to claim 1, wherein the guided control piston is shifted against the force of a spring element that is supported on a spring bearing.

9. The control valve according to claim 1, further comprising first and second work connections and a discharge connection formed in the valve housing.

10. The control valve according to claim 9, wherein a supply connection is connected to the first or second work connection and the other of the first and second work connections is connected to the discharge connection as a function of the position of the guided control piston.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention are explained in more detail below with reference to a drawing. Shown are:

(2) FIG. 1 in a schematic representation, a control valve arranged in a camshaft, and

(3) FIG. 2 a control valve in an alternative embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(4) In FIG. 1, an embodiment of a control valve 4 arranged in a camshaft 2 is shown. The control valve 4 is constructed in the form of a central valve and can be inserted for its use in a central hole of a camshaft adjuster (not shown).

(5) The control valve 4 here comprises an essentially hollow cylindrical valve housing 6 that is constructed in the form of a central screw according to the form of the control valve 4 as a central valve. In the housing hollow space, a hollow pressurized medium guide insert 8 made from plastic is inserted. Here, the outer diameter of the pressurized medium guide insert 8 is adapted to the inner diameter of the housing hollow space. Inside the pressurized medium guide insert 8, a hollow cylindrical control sleeve 10 is arranged whose outer diameter is adapted to the inner diameter of the pressurized medium guide insert 8. Inside the control sleeve 10 there is a control piston 12 formed as a hollow piston that can move in the axial direction.

(6) The control piston 12 can be shifted against the spring force of a spring element 14 that is supported on a spring bearing 16. For this purpose, an actuator, for example, an electromagnet with a plunger, can contact the axially outer end side of the control piston 12. An axial sliding of the control piston 12, control sleeve 10, and/or pressurized medium insert 8 from the valve housing 6 caused, in particular, by the spring force of the spring element 14 is prevented by a securing ring 20 arranged in a groove 18 of the valve housing.

(7) Inside the valve housing 6 there is also a hydraulically releasable non-return valve 22 whose closing body 24 is loaded with an axial force by a spring 26 that is supported on the spring bearing 16. In a housing shaft 28 of the valve housing 6 there is also a supply hole 30 in which a filter element 32 is arranged coaxially. The use of the filter element 32 prevents contaminating particles from reaching into the control valve 4 with the pressurized medium entering into the control valve 4, wherein, in particular, the control valve 4 is protected from functional disruptions.

(8) In the valve housing there are also work connections A, B for the pressurized medium chambers of the camshaft adjuster working in opposite directions and also a discharge connection T. Via a radial hole 34 in the camshaft, pressurized medium is fed to the control valve 4 as needed via a supply connection P not shown in more detail for a pressurized medium, for example, oil, wherein a supply direction of the pressurized medium is indicated with the arrow P. Thus, the pressurized medium is supplied to the inlet region of the control valve 4 from a radial direction, wherein the pressurized medium then flows via the axially directed supply hole 30 of the housing shaft 28 into the control valve 4. As a function of the position of the axially guided control piston 12, the supply connection P is connected to one of the work connections A, B, while the other work connection A, B is connected to the discharge connection T.

(9) To improve the pressurized medium supply into the control valve 4 and therefore to achieve overall an increased pressurized medium volume flow, the supply hole 30 is expanded in a funnel shape toward the pressurized medium inlet side. Therefore, the pressurized medium flowing from the radial direction through the radial hole 34 does not have to be deflected by 90 for entry into the supply hole 30 of the control valve 4. This arrangement permits an optimized pressurized medium supply into the control valve 4. Furthermore, additional space for the pressurized medium is created by the increased hole diameter in the region of the funnel-shaped expansion.

(10) In addition, the housing shaft 28 has, on its axial end, a thread 36 that is constructed as an external thread and by means of which the control valve 4 is screwed to the camshaft 2. Through a narrowing of the outer diameter of the housing shaft 28 in the axial region between the non-return valve 22 and thread 36, a waisted shank 38 is formed in this region. The funnel shaped expansion abuts the base of the filter element 32, and extends past an outermost end of the filter 32 to the supply inlet hole 30. Therefore, the valve housing has increased elasticity, wherein, by being screwed in with pretensioning, an increased elastic change in length is possible. Time varying changes in force and length occurring during operation can also be absorbed by an elastic elongation of the waisted shank. This has an overall positive effect on the durability of the screw connection.

(11) FIG. 2 shows a control valve 4 in an alternative embodiment. The control valve 4 shown here corresponds to the valve shown in FIG. 1 and differs only in that the supply hole 30 is widened in the shape of a funnel essentially in a region from the non-return valve 22 up to the inlet side of the pressurized medium. In other words, here the funnel-shaped expansion of the supply hole 30 extends essentially in a region from the non-return valve 22 up to the axially outer end of the housing shaft 28. In this way, additional space can be provided for the pressurized medium and this also leads to the fact that pressurized medium comes into the filter element 32 over the biggest area possible.

LIST OF REFERENCE NUMBERS

(12) 2 Camshaft 4 Control valve 6 Valve housing 8 Pressurized medium insert 10 Control sleeve 12 Control piston 14 Spring element 16 Spring bearing 18 Groove 20 Securing ring 22 Non-return valve 24 Closure body 26 Spring 28 Housing shaft 30 Supply hole 32 Filter element 34 Radial hole 36 Thread 38 Waisted shank A, B Work connection T Discharge connection P Supply connection