Camshaft phaser having non-return valves

Abstract

The disclosure relates to a camshaft phaser for adjusting a phase position between a crankshaft and a camshaft of a motor vehicle. The camshaft phaser comprises a stator, a rotor which is rotatable in relation thereto, and working chambers which are formed between the stator and the rotor and each of which are subdivided by a blade of the rotor into a first sub-chamber and a second sub-chamber. For storage of the hydraulic fluid, the camshaft phaser has a reservoir which is connected to the sub-chambers via one non-return valve each, in order that when a negative pressure prevails in one of the sub-chambers, hydraulic fluid is fed from the reservoir to this sub-chamber. The non-return valves are preloaded in such a way that they only open when a pressure within an associated sub-chamber falls below a predetermined negative pressure.

Claims

1. A camshaft phaser for adjusting a phase position between a crankshaft and a camshaft of a motor vehicle, the camshaft phaser comprising: a stator, a rotor configured to rotate relative to the stator, the rotor including a plurality of blades, a plurality of working chambers formed between the stator and the rotor, the plurality of blades respectively dividing each working chamber into a first sub-chamber and a second sub-chamber which are configured to receive hydraulic fluid so as to rotate the rotor relative to the stator, and a reservoir configured to store the hydraulic fluid, the reservoir fluidly connected to: i) each first sub-chamber via a respective first non-return valve so as to feed the hydraulic fluid to each first sub-chamber when a negative pressure is present in each first sub-chamber, and p2 ii) each second sub-chamber via a respective second non-return valve so as to feed the hydraulic fluid to each second sub-chamber when a negative pressure is present in each second sub-chamber, wherein selected non-return valves are preloaded, the selected non-return valves including: each first non-return valve being preloaded so as to remain closed until the negative pressure in each first sub-chamber decreases below a predetermined negative pressure thereby opening each first non-return valve, and/or each second non-return valve being preloaded so as to remain closed until the negative pressure in each second sub-chamber decreases below the predetermined negative pressure thereby opening each second non-return valve, wherein the predetermined negative pressure corresponds to a saturation pressure of the camshaft phaser.

2. The camshaft phaser according to claim 1, wherein the saturation pressure is between 0.15 bar and 1 bar.

3. The camshaft phaser according to claim 2, wherein the saturation pressure is 0.8 bar.

4. The camshaft phaser according to claim 1, further comprising a non-return valve plate on which each non-return valve is formed, wherein each non-return valve includes a connecting region resiliently attached to the non-return valve plate, and wherein the selected non-return valves are preloaded via a plastic deformation at the connecting region.

5. The camshaft phaser according to claim 4, wherein the connecting region of each selected non-return valve is heat-treated so as to reduce stresses caused by the plastic deformation.

6. The camshaft phaser according to claim 4, wherein the selected non-return valves are plastically deformed in a direction away from an open position so as to be pressed into a closed position when the camshaft phaser is assembled.

7. The camshaft phaser according to claim 6, wherein the reservoir is formed in a cover configured to press the selected non-return valves into the closed position.

8. The camshaft phaser according to claim 7, further comprising a phaser return spring disposed within the cover.

9. The camshaft phaser according to claim 1, wherein the selected non-return valves each include a separate spring configured to counteract an opening of the selected non-return valve.

10. The camshaft phaser according to claim 9, wherein the stator includes a plurality of recesses configured to respectively receive the separate spring of each selected non-return valve.

11. The camshaft phaser according to claim 10, wherein the separate spring of each selected non-return valve is configured to counteract the opening of the selected non-return valve via a respective preload pin.

12. The camshaft phaser according to claim 1, further comprising a central valve fluidly connected to each sub-chamber, the central valve configured to control a flow of the hydraulic fluid which rotates the rotor relative to the stator.

13. The camshaft phaser according to claim 12, wherein the feeding of the hydraulic fluid to each first sub-chamber or each second sub-chamber occurs when the central valve is in a holding position.

14. A camshaft phaser for adjusting a phase position between a crankshaft and a camshaft of a motor vehicle, the camshaft phaser comprising: a stator, a rotor configured to rotate relative to the stator, the rotor including a plurality of blades, a plurality of working chambers formed between the stator and the rotor, the plurality of blades respectively dividing each working chamber into a first sub-chamber and a second sub-chamber which are configured to receive hydraulic fluid so as to rotate the rotor relative to the stator, and a reservoir configured to store the hydraulic fluid, the reservoir fluidly connected to: i) each first sub-chamber via a respective first non-return valve so as to feed the hydraulic fluid to each first sub-chamber when a negative pressure is present in each first sub-chamber thereby opening each first non-return valve, and ii) each second sub-chamber via a respective second non-return valve so as to feed the hydraulic fluid to each second sub-chamber when a negative pressure is present in each second sub-chamber thereby opening each second non-return valve, wherein selected non-return valves are plastically deformed in a direction away from an open position prior to an assembly of the camshaft phaser, the selected non-return valves including each first non-return valve and/or each second non-return valve.

15. The camshaft phaser according to claim 14, wherein the selected non-return valves are plastically deformed such that: each first non-return valve is preloaded so as to remain closed until the negative pressure in each first sub-chamber decreases below a predetermined negative pressure thereby opening each first non-return valve, and/or each second non-return valve is preloaded so as to remain closed until the negative pressure in each second sub-chamber decreases below the predetermined negative pressure thereby opening each second non-return valve.

16. The camshaft phaser according to claim 14, wherein the selected non-return valves are pressed to a closed position after the assembly of the camshaft phaser.

17. The camshaft phaser according to claim 14, further comprising a non-return valve plate on which each non-return valve is formed.

18. A camshaft phaser for adjusting a phase position between a crankshaft and a camshaft of a motor vehicle, the camshaft phaser comprising: a stator, a rotor configured to rotate relative to the stator, the rotor including a plurality of blades, a plurality of working chambers formed between the stator and the rotor, the plurality of blades respectively dividing each working chamber into a first sub-chamber and a second sub-chamber which are configured to receive hydraulic fluid so as to rotate the rotor relative to the stator, and a reservoir configured to store the hydraulic fluid, the reservoir fluidly connected to: i) each first sub-chamber via a respective first non-return valve so as to feed the hydraulic fluid to each first sub-chamber when a negative pressure is present in each first sub-chamber thereby opening each first non-return valve, and ii) each second sub-chamber via a respective second non-return valve so as to feed the hydraulic fluid to each second sub-chamber when a negative pressure is present in each second sub-chamber thereby opening each second non-return valve, wherein each non-return valve is resiliently formed on a common non-return valve plate, and wherein a group of selected non-return valves each include a separate spring configured to counteract an opening of the selected non-return valve, the group of selected non-return valves comprising each first non-return valve and/or each second non-return valve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure is explained below with the aid of drawings. In the figures:

(2) FIG. 1 shows a schematic representation of a camshaft phaser,

(3) FIG. 2 shows a perspective view of a part of the camshaft phaser,

(4) FIGS. 3 to 6 show different schematic representations of a part of the camshaft phaser in a first embodiment,

(5) FIGS. 7 to 9 show different schematic representations of a part of the camshaft phaser in a second embodiment,

(6) FIG. 10 shows a graph showing a pressure curve over time in sub-chambers of the camshaft phaser, and

(7) FIG. 11 shows a graph showing the relationship between a preload force acting on the non-return valves of the camshaft phaser and the pressure required to open the non-return valves.

DETAILED DESCRIPTION

(8) The figures are merely schematic in nature and serve solely for understanding the disclosure. Identical elements are provided with the same reference symbols. The features of the individual embodiments can be interchanged.

(9) FIG. 1 shows a schematic representation of a camshaft phaser 1 according to the disclosure. The camshaft phaser 1 is used to adjust a phase position between a crankshaft and a camshaft of a motor vehicle. The camshaft phaser 1 has a stator 2. In particular, the stator 2 can be rotationally coupled or rotationally couplable to the crankshaft. The camshaft phaser 1 has a rotor 3. In particular, the rotor 3 can be rotationally coupled or rotationally couplable to the camshaft. The rotor 3 is rotatable relative to the stator 2 and can be arranged radially within and concentric to the stator 2. The camshaft phaser 1 has working chambers 4 which are formed between the stator 2 and the rotor 3 which are each subdivided by a blade of the rotor 3 into a first sub-chamber 5 (A chamber) and a second sub-chamber 6 (B chamber). Hydraulic fluid can be applied to the sub-chambers 5, 6 in order to adjust the rotor 3 relative to the stator 2.

(10) For storage of the hydraulic fluid, the camshaft phaser 1 has a reservoir 9 which is connected to the sub-chambers 5, 6 via one non-return valve 7, 8 each in order that when a negative pressure prevails in one of the sub-chambers 5, 6, the hydraulic fluid is fed from the reservoir 9 to this sub-chamber 5, 6. Thus, hydraulic fluid is fed to the first sub-chamber 5 from the reservoir 9 via the first non-return valve 7 when a negative pressure prevails in the first sub-chamber 5, and hydraulic fluid is fed to the second sub-chamber 6 from the reservoir 9 via the second non-return valve 8 when a negative pressure prevails in the second sub-chamber 6.

(11) For oil pressure actuated adjustment, the two sub-chambers 5, 6 are each connected to a central valve 12 via a working channel 10, 11. Thus, depending on the switching position of the central valve 12, the first sub-chamber 5 is connected to a pump for pressurization or to a tank for pressure relief via the first working channel 10, and, depending on the switching position of the central valve 12, the second sub-chamber 6 is connected to the pump for pressurization or to the tank for pressure relief via the second working channel 11.

(12) According to the disclosure, the non-return valves 7, 8 are preloaded in such a way that they only open when the pressure in the associated sub-chamber 5, 6 falls below a predetermined negative pressure. This means that the non-return valves 7, 8 are preloaded with a certain preload force against their opening direction, which only allows the non-return valves 7, 8 to open when the pressure drops below the predetermined negative pressure, i.e., when the negative pressure in the associated sub-chamber 5, 6 is sufficiently high.

(13) FIG. 2 shows a perspective view of a part of the camshaft phaser 1. The reservoir 9 is formed in a cover 13 of the camshaft phaser 1 so that the hydraulic fluid can be fed axially via the two non-return valves 7, 8 into the corresponding sub-chambers 5, 6. In addition, a return spring 14 is arranged in the cover 13.

(14) The camshaft phaser 1 has a non-return valve plate 15 on which the non-return valves 7, 8 are formed. The non-return valves 7, 8 are resiliently mounted via a connecting region 16 so that they can be (elastically) bent in their opening direction in order to allow hydraulic fluid to flow from the reservoir 9 into the corresponding sub-chamber 5, 6.

(15) FIGS. 3 to 6 show a first embodiment of the camshaft phaser 1. In order to introduce the preload to the non-return valves 7, 8, the connecting region 16 of each non-return valve 7, 8 is plastically deformed, in particular against the opening direction. The punched non-return valves 7, 8 in the non-return valve plate 15 are bent at the connecting region 16 up to their plastic range (FIG. 4). After bending, the non-return valve plate 15 is thermally treated in order to eliminate and/or reduce the stresses caused by the deformation, so that the connecting region 16 remains stress-free (FIG. 5). During assembly, the non-return valve plate 15 is mounted (between the stator 2 and the cover 13) so that it rests against the cover 13, so that the preload is generated during assembly (FIG. 6).

(16) FIGS. 7 to 9 show a second embodiment of the camshaft phaser 1. In order to introduce the preload to the non-return valves 7, 8, preload springs 17 are installed in the camshaft phaser 1, which apply the preload to the non-return valves 7, 8, in particular against their opening direction. In particular, the preload springs 17 are installed in the stator 2. For this purpose, the stator 2 has (axial) recesses 18. A preload pin 19 is arranged in each of the recesses 18, which is arranged between the associated non-return valve 7, 8 and the associated preload springs 17 in such a way that it transmits the spring force of the preload spring 17 to the non-return valve 7, 8 (detailed view IX in FIG. 9).

(17) FIG. 10 shows a graph 20 which shows a course over time of the pressure in the first sub-chamber 5 using a curve 21 and the pressure in the second sub-chamber 6 using a curve 22 during controlled operation of the camshaft phaser 1. It can be seen here that the pressure in the two sub-chambers 5, 6 drops below an ambient pressure 23 in an alternating manner. The predetermined negative pressure can be selected such that it is not reached during controlled operation of the camshaft phaser 1.

(18) FIG. 11 shows a graph 24 which shows a relationship between a preload force acting on the non-return valves 7, 8 and the pressure required to open the non-return valves 7, 8. As the (negative) pressure increases, the opening of the non-return valve 7, 8 increases. A first curve 25 shows a relationship of a non-return valve to which a preload force of 0.2 N is applied, wherein the non-return valve opens when a negative pressure of approximately 0.15 bar is reached. A second curve 26 shows a relationship of a non-return valve to which a preload force of 0.4 N is applied, wherein the non-return valve opens when a negative pressure of approximately 0.35 bar is reached. A third curve 27 shows a relationship of a non-return valve to which a preload force of 0.6 N is applied, wherein the non-return valve opens when a negative pressure of approximately 0.55 bar is reached. A fourth curve 28 shows a relationship of a non-return valve to which a preload force of 0.8 N is applied, wherein the non-return valve opens when a negative pressure of approximately 0.7 bar is reached. A fifth curve 29 shows a relationship of a non-return valve to which a preload force of 1.0 N is applied, wherein the non-return valve does not yet open when a negative pressure of approximately 0.85 bar is reached. A sixth curve 30 shows a relationship of a non-return valve to which a preload force of 1.2 N is applied, wherein the non-return valve does not yet open when a negative pressure of approximately 0.85 bar is reached.

(19) In example embodiments, the predetermined negative pressure can be between 0.15 bar and 1 bar, between 0.35 bar and 0.95 bar, between 0.55 bar and 0.9 bar, or between 0.7 bar and 0.85 bar. The selection of the predetermined negative pressure as 0.8 bar has proven to be suitable. In particular, the predetermined negative pressure can essentially correspond to a saturation pressure of the camshaft phaser 1.

List of Reference Symbols

(20) 1 Camshaft phaser 2 Stator 3 Rotor 4 Working chamber 5 First sub-chamber 6 Second sub-chamber 7 First non-return valve 8 Second non-return valve 9 Reservoir 10 First working channel 11 Second working channel 12 Central valve 13 Cover 14 Return spring 15 Non-return valve plate 16 Connecting region 17 Preload spring 18 Recess 19 Preload pin 20 Graph 21 Oil pressure curve 22 Oil pressure curve 23 Ambient pressure 24 Graph 25 Preload force curve 26 Preload force curve 27 Preload force curve 28 Preload force curve 29 Preload force curve 30 Preload force curve