Hydraulic valve for a cam phaser

Abstract

A hydraulic valve for a cam phaser, the hydraulic valve including a bushing including a piston that is movable in a bore along a longitudinal direction; a supply connection configured to feed a hydraulic fluid; a first operating connection and a second operation connection; and a first tank drain connection and a second tank drain connection configured to drain the hydraulic fluid; and a first check valve associated with the first operating connection and a second check valve associated with the second operating connection, wherein the first operating connection and the second operating connection are connectable through at least one of the first check valve and the second check valve alternatively with each other or with the supply connection or with one of the first tank drain connection and the second tank drain connection by moving the piston, wherein the hydraulic valve includes five switching positions.

Claims

1. A hydraulic valve for a cam phaser, the hydraulic valve comprising: a bushing including a piston that is movable in a bore along a longitudinal direction; a supply connection configured to feed a hydraulic fluid; a first operating connection and a second operating connection; and a first tank drain connection and a second tank drain connection configured to drain the hydraulic fluid; and a first check valve associated with the first operating connection and a second check valve associated with the second operating connection, wherein the first operating connection and the second operating connection are connectable through at least one of the first check valve and the second check valve alternatively with each other or with the supply connection or with one of the first tank drain connection and the second tank drain connection by moving the piston, wherein the hydraulic valve includes five switching positions, wherein the second operating connection is connected with the supply connection and the first operating connection is connected with the first tank drain connection in a first switching position of the piston and a fluid path from the first operating connection to the second operating connection is openable by the first check valve that is associated with the first operating connection under a pressure that exceeds a threshold value, wherein the second operating connection is connected with the supply connection and a connection between the first operating connection and the first tank drain connection is interrupted in a second switching position of the piston and a fluid path from the first operating connection to the second operating connection is openable by the first check valve that is associated with the first operating connection under the pressure that exceeds the threshold value, wherein a connection between the first operating connection, the second operating connection and the supply connection and the first tank drain connection and the second tank drain connection is interrupted in a third switching position of the piston which is positioned in a center position, wherein the first operating connection is connected with the supply connection and a connection between the second operating connection and the second tank drain connection is interrupted in a fourth switching position of the piston and a fluid path from the second operating connection to the first operating connection is openable by the second check valve that is associated with the second operating connection under the pressure that exceeds the threshold value, wherein the first operating connection is connected with the supply connection and the second operating connection is connected with the second tank drain connection in a fifth switching position of the piston and a fluid path from the second operating connection to the first operating connection is openable by the second check valve that is associated with the second operating connection under the pressure that exceeds the threshold value, wherein the first check valve is arranged at a first piston attachment that envelops the piston and that is connected with the piston in a rigid manner, and wherein the second check valve is arranged at a second piston attachment that envelops the piston and that is connected with the piston in a rigid manner.

2. The hydraulic valve according to claim 1, wherein the first operating connection is associated with the first check valve on an outside of the piston and the second operating connection is associated with the second check valve on the outside of the piston.

3. The hydraulic valve according to claim 1, wherein the first check valve is provided as disc shaped closing element that is preloaded against the first piston attachment by a common compression spring, and wherein the second check valve is provided as disc shaped closing element that is preloaded against the second piston attachment by the common compression spring.

4. The hydraulic valve according to claim 1, wherein the first piston attachment includes two first annular bars which respectively include two first control edges that respectively cooperate with two recesses in the bushing, and wherein the second piston attachment includes two second annular bars which respectively include two second control edges that respectively cooperate with the two recesses in the bushing.

5. The hydraulic valve according to claim 4, wherein the first control edges of the first annular bars and the second control edges of the second annular bars cooperate with the first operating connection and the second operating connection configured as radial recesses in the bushing and with two groove shaped recesses in a portion of the bore, wherein the two groove shaped recesses are arranged in the axial direction respectively between the first operating connection and the associated first tank drain connection and the second operating connection and the associated second tank drain connection.

6. A cam phaser with the hydraulic valve according to claim 1, wherein the hydraulic valve is configured as a central valve.

7. A hydraulic valve for a cam phaser, the hydraulic valve comprising: a bushing including a piston that is movable in a bore along a longitudinal direction between a first end position and a second end position; a supply connection for feeding a hydraulic fluid; a first operating connection and a second operating connection; and a first tank drain connection and a second tank drain connection configured to drain the hydraulic fluid, wherein the first operating connection and the second operating connection are in fluid communication with each other by positioning of the piston, and wherein the piston includes two outer annular bars that are arranged at axially exterior ends of the piston and configured to completely close the second tank drain connection in the first end position and to completely close the first tank drain connection in the second end position, wherein an entirety of a first outer annular bar of the two outer annular bars is arranged in the longitudinal direction between the first operating connection and the first tank drain connection when the first outer annular bar completely closes the first tank drain connection in the second end position, wherein an entirety of a second outer annular bar of the two outer annular bars is arranged in the longitudinal direction between the second operating connection and the second tank drain connection when the second outer annular bar completely closes the second tank drain connection in the first end position, and wherein groove shaped recesses are arranged in the longitudinal direction respectively between the first operating connection and the associated first tank drain connection and between the second operating connection and the associated second tank drain connection wherein an entirety of a first groove shaped recess of the groove shaped recesses is arranged in the longitudinal direction between the first operating connection and the first tank drain connection, wherein an entirety of a second groove shaped recess of the groove shaped recesses is arranged in the longitudinal direction between the second operating connection and the second tank drain connection, wherein the entirety of the first outer annular bar is arranged in the longitudinal direction between the first groove shaped recess and the first tank drain connection when the first outer annular bar completely closes the first tank drain connection in the second end position, wherein the entirety of the second outer annular bar is arranged in the longitudinal direction between the second groove shaped recess and the second tank drain connection when the second outer annular bar completely closes the second tank drain connection in the first end position.

8. The hydraulic valve according to claim 7, wherein the bushing includes two groove shaped recesses in a portion of the bore, and wherein the groove shaped recesses are respectively associated with the outer annular bars.

9. The hydraulic valve according to claim 7, wherein the piston includes two inner annular bars between the two outer annular bars, and wherein the two inner annular bars are respectively associated with the first operating connection and the second operating connection.

10. The hydraulic valve according to claim 7, wherein the piston is movable into a first position where the first tank drain connection and the second tank drain connection are closed by the outer annular bars and the second operating connection is in fluid communication with the supply connection and the first operating connection is in fluid communication with the second operating connection.

11. A hydraulic valve for a cam phaser, the hydraulic valve comprising: a bushing including a piston that is movable in a bore along a longitudinal direction between a first end position and a second end position; a supply connection for feeding a hydraulic fluid; a first operating connection and a second operating connection; and a first tank drain connection and a second tank drain connection configured to drain the hydraulic fluid, wherein the first operating connection and the second operating connection are in fluid communication with each other by positioning of the piston, and wherein the piston includes two outer annular bars that are arranged at axially exterior ends of the piston and configured to completely close the second tank drain connection in the first end position and to completely close the first tank drain connection in the second end position, wherein groove shaped recesses are arranged in the longitudinal direction respectively between the first operating connection and the associated first tank drain connection and between the second operating connection and the associated second tank drain connection, wherein the piston includes two inner annular bars between the two outer annular bars, wherein the two inner annular bars are respectively associated with the first operating connection and the second operating connection, and wherein the piston is movable into a second position where the first tank drain connection and the second tank drain connection are closed by the two outer annular bars and the first operating connection and the second operating connection are respectively closed by the two inner annular bars.

12. The hydraulic valve according to claim 11, wherein the piston is movable into a third switching position where the first tank drain connection and the second tank drain connection are closed by the outer annular bars and the first operating connection is in fluid communication with the supply connection and the first operating connection is in fluid communication with the second operating connection.

13. A method for operating the hydraulic valve according to claim 12 in the first end position, wherein the second tank drain connection is completely closed by a second annular bar of the two outer annular bars, wherein the first tank drain connection is opened by an annular gap between a first annular bar of the two outer annular bars and one of the groove shaped recesses and the first operating connection is fluid flow connected with the second operating connection, and wherein the second operating connection is fluid flow connected with the supply connection.

14. The method for operating the hydraulic valve according to claim 13 in the switching third position, wherein the first tank drain connection is completely closed by the first annular bar of the two outer annular bars and the second tank drain connection is completely closed by the second annular bar of the two outer annular bars, wherein the first operating connection is fluid flow connected with the second operating connection, and wherein the first operating connection is fluid flow connected with the supply connection.

15. The method for operating the valve according to claim 13 in the second end position, wherein the first tank drain connection is completely closed by the first annular bar of the two outer annular bars, wherein the second tank drain connection is opened by an annular gap between the second annular bar of the two outer annular bars and another one of the groove shaped recesses, wherein the first operating connection is fluid flow connected with the second operating connection, and the first operating connection is fluid flow connected with the supply connection.

16. The method for operating the hydraulic valve according to claim 13, wherein the piston is moved between the first end position and the second end position in a continuously variable manner.

17. A method for operating the hydraulic valve according to claim 12 in the first end position, wherein the second tank drain connection is completely closed by a second annular bar of the two outer annular bars, wherein the first tank drain connection is opened by an annular gap between a first annular bar of the two outer annular bars and one of the groove shaped recesses and the first operating connection is fluid flow connected with the second operating connection, wherein the second operating connection is fluid flow connected with the supply connection, wherein the first tank drain connection is completely closed by the first annular bar of the two outer annular bars and the second tank drain connection is completely closed by the second annular bar of the two outer annular bars, wherein the first operating connection is fluid flow connected with the second operating connection, and wherein the second operating connection is fluid flow connected with the supply connection.

18. A method for operating the hydraulic valve according to claim 12 in the first end position, wherein the second tank drain connection is completely closed by a second annular bar of the two outer annular bars, wherein the first tank drain connection is opened by an annular gap between a first annular bar of the two outer annular bars and one of the groove shaped recesses and the first operating connection is fluid flow connected with the second operating connection, wherein the second operating connection is fluid flow connected with the supply connection, wherein the first tank drain connection is completely closed by the first annular bar of the two outer annular bars and second tank drain connection is completely closed by the second annular bar of the two outer annular bars, and wherein the first operating connection is closed for the fluid flow by a first annular bar of the two inner annular bars and the second operating connection is closed for the fluid flow by a second annular bar of the two inner annular bars.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages can be derived from the subsequent drawing description. The drawing figures illustrate an embodiment of the invention. The drawing figures, the description and the claims include several features in combination. A person skilled in the art will also view the features individually and will combine them into other useful combinations, wherein

(2) FIG. 1 illustrates a hydraulic valve configured to adjust a cam phaser according to an embodiment of the invention in a first switching position illustrated in a longitudinal sectional view;

(3) FIG. 2 illustrates the hydraulic valve according to FIG. 1 in a perspective view;

(4) FIG. 3 illustrates a switching diagram of the hydraulic valve according to FIG. 1;

(5) FIG. 4 illustrates a piston assembly of the hydraulic valve according to FIG. 1 in a perspective view;

(6) FIG. 5 illustrates a piston assembly according to FIG. 4 in a longitudinal sectional view;

(7) FIG. 6 illustrates the bushing of the hydraulic valve according to FIG. 1 in a longitudinal sectional view; and

(8) FIG. 7 illustrates the characteristic diagram of the hydraulic valve according to FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

(9) In the drawing figures identical or like components are provided with identical reference numerals. The drawing figures merely show embodiments and do not limit the sprit and scope of the invention.

(10) FIG. 1 illustrates a hydraulic valve 1 for adjusting a non-illustrated cam phaser according to an embodiment of the invention in a first switching position 10 in a longitudinal sectional view. The hydraulic valve 1 includes a bushing 2 with a piston 4 that is movably arranged in a longitudinal direction L in a bore 3. The piston 4 is supported by a compression coil spring 5 at the bushing 2 or supported at a disc 6 that is arranged by a ring 7 in the bushing 2.

(11) The bushing 2 includes a supply connection P for feeding a hydraulic fluid and a first operating connection A and a second operating connection B that are respectively provided as a radial recess or plural radial recesses in the bushing in the sequence A-P-B. The supply connection P is protected against contamination by a screen 8 that is externally arranged at the bushing 2. Furthermore a band check valve 9 is arranged on an interior side of the bushing in a portion of the supply connection in order to prevent a flow back of hydraulic fluid in a direction towards the pump.

(12) The hydraulic valve 1 includes a first and a second tank drain connection T1, T2 for draining the hydraulic fluid wherein both connections are respectively configured axially. The first operating connection A and the second operating connection B are respectively associated with a check valve 15, 16 wherein the first operating connection A and the second operating connection B are alternatively connectable with each other and/or with the supply connection P and/or with one of the tank drain connections T1, T2 through at least one of the check valves 15, 16 by moving the piston 4.

(13) It is feasible according to the invention to provide only a single tank drain T at the valve. Thus, for example the hydraulic fluid that is drained towards the tank can be drained through the piston 4. The described tank drain connections T1 and T2 are interpreted in this case as a tank drain that is associated with the respective operating connection A or B, wherein both are run out of the valve by the only tank drain connection T.

(14) According to the invention the hydraulic valve 1 includes five switching positions 10-14, wherein the second operating connection B is connected through the bore hole 3 and an annular cavity 17 configured therein about the piston 4 with the supply connection P in the first switching position 10 of the piston 4 illustrated in FIG. 1 and the first operating connection A is connected through the bore hole 3 and another fluid path between a first piston attachment 18 and an interior of the bushing with the first tank drain connection T1 as will be described in more detail infra.

(15) An outer annular bar 27 closes a second tank drain opening 22 completely on an opposite side of the piston 4. The first switching position can also be interpreted as a first end position of the piston 4.

(16) When a pressure applied to the first operating connection A exceeds a predetermined threshold value an additional fluid path is openable from the first operating connection A to the second operating connection B through the check valve 15 that is associated with the first operating connection A and the hydraulic fluid is passed through with fast phaser characteristics to the second operating connection B.

(17) In a second switching position 11 of the piston 4 the second operating connection B is connected with the supply connection P and a connection between the first operating connection A and the first tank drain connection T1 is interrupted by the piston attachment 18, in particular by the outer annular bar 25, wherein the fluid path from the first operating connection A to the second operating connection B is openable by the check valve 15 that is associated with the first operating connection in this position. By the same token the tank drain connection T2 is closed by the annular bar 27 which is arranged at the piston attachment 19. In this position the hydraulic valve 1 has pure fast phaser characteristics. This second switching position can also be interpreted as a first position of the piston 4 within the control range of the fast phaser characteristics.

(18) In a third switching position 12 the piston 4 is positioned in a center position in which a connection between the operating connections A, B and the supply connection P and the tank drain connections T1, T2 is completely interrupted. This third switching position can also be interpreted as a second position of the piston 4 within the control range of the fast phaser characteristics.

(19) In a fourth switching position 13 of the piston 4 the first opening connection A is connected with the supply connection P and a connection between the second operating connection B and the second tank drain connection T2 is interrupted by a second piston attachment 19, in particular by the outer annular bar 27. A fluid path from the second operating connection B to the first operating connection A is openable by the check valve 16 that is associated with the second operating connection B through a pressure that exceeds a threshold value. By the same token the tank drain connection T1 is closed by the annular bar 25 that is arranged at the piston attachment 18. This third switching position can also be interpreted as a third position of the piston 4 within the control range of the fast phaser characteristics.

(20) In a fifth switching position the piston 4 is arranged in a second end position where the first operating connection A is connected by the bore hole 3 and an annular cavity 17 configured therein about the piston 4 with the supply connection P and the second operating connection B is connected through the bore hole 3 and a fluid path between the second piston attachment 19 and an inside of the bushing with the second tank drain connection T2 as will be described in more detail infra. On an opposite side of the piston 4 an outer annular cavity 25 completely closes the second tank drain connection T1. The fifth switching position can also be interpreted as a second end position of the piston 4.

(21) When a pressure applied to a second operating connection B exceeds a particular threshold value, a fluid path from the second operating connection B to the first operating connection A is openable through the check valve 16 that is associated with the operating connection B.

(22) As evident in particular from FIG. 5 a respective check valve 15, 16 on the outside of the piston 4 is respectively associated with the first operating connection A and the second operating connection B. The check valves are respectively arranged at the piston attachments 18, 19 which envelop the piston 4 and which are connected in a rigid manner with the piston 4 e.g. by a press fit or by welding. This facilitates a compact configuration of the hydraulic valve and a simple and economical configuration of the piston assembly 20.

(23) The check valves 15, 16 are respectively provided as disc shaped closing elements which are preloaded by a common compression spring 21 against the piston attachments 18, 19 and thus close openings 22, 23 through which hydraulic fluid is conductible through the check valves 15, 16 starting with the pressure threshold value described supra. Thus, a preassembled piston assembly 20 can be advantageously provided which can be installed in the bushing 2 in a simple manner.

(24) Axial protrusions 46, 47 of the check valves 15, 16 facilitate a secure axial movement on the piston 4.

(25) The piston attachments 18, 19 respectively include two inner annular bars 24, 26 and two outer annular bars 25, 27 which respectively include two control edges 28, 29, 30, 31, 32, 33, 34, 35 which cooperate with recesses in the bushing 2. Through the control edges 28-35 the volume flow of the hydraulic fluid can be controlled in an improved manner so that a significant increase of the adjustment speed, in particular in the upper engine speed range and improved force properties can be obtained.

(26) Thus, the control edges 28-35 of the inner and outer annular bars 24-27 cooperate with the operating connections A, B as radial recesses 38, 39 in the bushing 2 and with two groove shaped recesses 36, 37 in the portion of the bore hole 3, wherein the groove shaped recesses 36, 37 are arranged in the axial direction respectively between the operating connection A or B and the associated tank drain connection T1 or T2. The groove shaped recesses 36, 37 facilitate a position dependent opening and closing of the tank drain connections T1, T2 in cooperation with the control edges 28-30 and 33-35 in that a fluid path between the first operating connection A and the second operating connection B or to the first or second tank drain connection T1 or T2 is opened in the switching positions 10 and 14 between the outer annular bars 25 or 27 of the piston attachments 18 or 19 and an inside of the bushing. Thus, the outer annular bar 25 of the first piston attachment 18 is in the portion of the groove shaped recess 36 in the first switching position 10 illustrated in FIG. 1 and a fluid flow between the annular bar 25 and an inner side of the bushing is possible towards the tank drain connection T1. The outer annular bar 27 of the second piston attachment 19, however, is outside of the groove shaped recess 37, so that no fluid flow in a direction towards the tank drain connection T2 is possible through the closed control edges 34, 35.

(27) In the second and in the fourth switching position 11 and 13 of the hydraulic valve 1 the outer annular bars 25 and 27 are arranged outside of the groove shaped recesses 36 and 37 so that no fluid flow is possible in a direction towards the tank drain connections T1 or T2 through the closed control edges 34, 35, 28, 29.

(28) FIG. 7 illustrates a characteristic volume flow diagram of the hydraulic valve 1 plotted over valve travel. The volume flow/valve travel characteristic diagram shows the resulting volume flow as a function of a position of the piston 4 (5 switching positions 10-14).

(29) The lines 40 and 40′ show the volume flow from A-B and the lines 41 and 41′ show the volume flow from P-B during the first and the second switching position 10 and 11.

(30) Approximately after half the total travel the center position 12 is reached where a connection between the operating connections A, and B and the supply connection P and the tank drain connections T1, T2 is completely interrupted.

(31) The lines 42 and 42′ show the volume flow from P to A and the lines 43 and 43′ show the volume flow from B-A in the fourth and the fifth switching position 13 and 14.

(32) It is evident from the lines 44 and 44′ that the connection A to T1 is only open in the first switching position 10. The connection B to T2 is only open in the fifth switching position 14 as illustrated by the lines 45 and 45′.