Hydraulic camshaft adjuster

Abstract

A hydraulic camshaft adjuster for adjusting the control times of gas exchange valves of an engine is provided. A stator is rotatable synchronously with a crankshaft of the engine. A rotor is arranged so as to be rotatable relative to the stator, and is rotatable synchronously with a camshaft. A plurality of ribs are provided on the stator, dividing an annular chamber between the stator and the rotor into a plurality of pressure chambers. A rotor hub and a plurality of blades extend radially outward from the rotor hub, dividing the pressure chambers into two working chambers having different effective directions. An additional connectable pressure booster is provided at least in an effective direction of the hydraulic camshaft adjuster. The pressure booster can boost the rotor when active.

Claims

1. A hydraulic camshaft adjuster for adjusting timings of gas exchange valves of an internal combustion engine, the hydraulic camshaft adjuster comprising: a stator configured to rotate synchronously with a crankshaft of the internal combustion engine, a rotor arranged within the stator so as to rotate relative to the stator, the rotor configured to rotate synchronously with a camshaft, and a plurality of ribs extending radially inwardly from the stator, the plurality of ribs dividing an annular chamber between the stator and the rotor into a plurality of pressure chambers, wherein the rotor has a rotor hub and a plurality of vanes extending radially outwardly from the rotor hub, the plurality of vanes dividing the plurality of pressure chambers into respective first and second groups of working chambers, which have opposing effective directions and the first and second groups of working chambers are each supplied with a pressure medium flowing in or out in a pressure medium circuit, and having a pressure medium accumulator configured to store the pressure medium, wherein an additional working chamber serves as a selectable pressure boost configured to act on a dedicated vane of the plurality of vanes so as to selectively assist the first group of working chambers in a first direction, in which the pressure medium supplied to the selectable pressure boost rotates the rotor relative to the stator, such that: in a first operating state, the first group of working chambers, excluding the additional working chamber, is configured to receive the pressure medium so as to move the rotor in the first direction, in a second operating state, the additional working chamber, in addition to the first group of working chambers, is configured to receive the pressure medium so as to move the rotor in the first direction, and in a third operating state, the second group of working chambers is configured to receive the pressure medium so as to move the rotor in a second direction, and wherein the hydraulic camshaft adjuster further comprises a single control valve configured to control the first, second, and third operating states.

2. The hydraulic camshaft adjuster as claimed in claim 1, wherein the control valve is a central valve arranged in a central opening of the rotor.

3. The hydraulic camshaft adjuster as claimed in claim 1, wherein the selectable pressure boost is configured to provide an adjusting force in precisely one effective direction oriented counter to an effective direction of drag torques of the camshaft.

4. The hydraulic camshaft adjuster as claimed in claim 1, wherein a volume flow of the pressure medium caused by a pressure medium pump configured to supply the pressure medium is divided by the control valve into a first partial flow and a second partial flow, wherein the first partial flow of the pressure medium is supplied to the first group of working chambers, and the second partial flow is supplied to the selectable pressure boost.

5. The hydraulic camshaft adjuster as claimed in claim 1, wherein the hydraulic camshaft adjuster is connected to a variable valve train of an internal combustion engine.

6. A hydraulic camshaft adjuster comprising: a stator configured to rotate synchronously with a crankshaft of an internal combustion engine, the stator having a plurality of radially inwardly-extending ribs; a rotor arranged within the stator so as to rotate relative to the stator, the rotor configured to rotate synchronously with a camshaft, the rotor having a rotor hub and a plurality of vanes extending radially outwardly from the rotor hub, wherein an annular chamber is defined between the rotor and the stator, and the plurality of radially inwardly-extending ribs divides the annular chamber into a plurality of pressure chambers, and the plurality of vanes divides the plurality of pressure chambers into a plurality of working chambers configured to selectively rotate the rotor relative to the stator when provided with hydraulic pressure via a pressure medium circuit, wherein one working chamber of the plurality of working chambers is a pressure boost working chamber configured to act on a dedicated vane of the plurality of vanes; and a single control valve coupled to the pressure medium circuit, the control valve operable in (i) a first operating state which forces the rotor in a first rotational direction in which a first group of working chambers of the plurality of working chambers, excluding the pressure boost working chamber, is configured to be provided with the hydraulic pressure, (ii) a second operating state which forces the rotor in the first rotational direction in which the pressure boost working chamber, in addition to the first group of working chambers, is configured to be provided with the hydraulic pressure, and (iii) a third operating state in which a second group of working chambers of the plurality of working chambers is configured to be provided with the hydraulic pressure so as to force the rotor in a second rotational direction.

7. The hydraulic camshaft adjuster of claim 6, further comprising a pump configured to provide the hydraulic pressure.

8. The hydraulic camshaft adjuster of claim 6, wherein the control valve is a central valve arranged in a central opening of the rotor.

9. The hydraulic camshaft adjuster of claim 6, wherein in the second operating state, the pressure boost working chamber provides an additional pressure boost so as to apply an adjusting force in precisely one effective direction oriented counter to an effective direction of drag torques of the camshaft.

10. A hydraulic camshaft adjuster comprising: a stator configured to rotate synchronously with a crankshaft of an internal combustion engine, the stator having a plurality of radially inwardly-extending ribs; a rotor arranged within the stator so as to rotate relative to the stator, the rotor configured to rotate synchronously with a camshaft, the rotor having a rotor hub and a plurality of vanes extending radially outwardly from the rotor hub; a plurality of pressure chambers between the stator and the rotor configured to selectively rotate the rotor relative to the stator; an additional pressure chamber serving as a pressure boost chamber configured to act on a dedicated vane of the plurality of vanes so as to selectively rotate the rotor in a first rotational direction relative to the stator; and a single control valve coupled to a pressure medium circuit, the control valve operable in (i) a first operating state which forces the rotor in the first rotational direction in which the plurality of pressure chambers, excluding the pressure boost chamber is configured to receive hydraulic pressure from a pump, (ii) a second operating state which forces the rotor in the first rotational direction in which the pressure boost chamber, in addition to the plurality of pressure chambers, is configured to receive the hydraulic pressure from the pump, and (iii) a third operating state in which the plurality of pressure chambers is configured to receive the hydraulic pressure from the pump so as to force the rotor in a second rotational direction relative to the stator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Various embodiments are explained in greater detail below and the associated drawings. In the figures, components that are the same or components with the same function are denoted by the same reference signs. In the drawings:

(2) FIG. 1 shows an illustrative embodiment of a hydraulic camshaft adjuster in section;

(3) FIG. 2 shows a schematic illustration of a hydraulic camshaft adjuster intended to illustrate the pressure medium supply to the working chambers;

(4) FIG. 3 shows the hydraulic camshaft adjuster in a case of a rotation of the rotor in the “retard” direction;

(5) FIG. 4 shows the hydraulic camshaft adjuster in a case of a rotation of the rotor in the “advance” direction without a pressure booster;

(6) FIG. 5 shows the hydraulic camshaft adjuster in a case of a rotation of the rotor in the “advance” direction with the addition of the pressure booster.

DETAILED DESCRIPTION OF THE DRAWINGS

(7) FIG. 1 shows an illustrative embodiment of a hydraulic camshaft adjuster 1 according to an embodiment for adjusting the valve timings of an internal combustion engine. The hydraulic camshaft adjuster 1 illustrated schematically in FIG. 1 is designed as a vane-type adjuster and comprises a stator 2, which can be driven by a crankshaft (not illustrated) of an internal combustion engine, and a rotor 3, which can be connected for conjoint rotation to a camshaft (likewise not illustrated). The rotor 3 has a rotor hub 4, from which a plurality of vanes 5, 6, 7 extend in a radial direction. The stator 2 has a plurality of ribs 8, 9, 10, which divide an annular chamber 11 between the stator 2 and the rotor 3 into a plurality of pressure chambers 12, 13, 14. The pressure chambers 12, 13, 14 are divided by the vanes 5, 6, 7 of the rotor 3 into working chambers 15, 16, 17, 18, 19, 20. In addition to the working chambers 15, 16, 17, 18, 19, 20 known in the normal operation of the hydraulic camshaft adjuster 1, a working chamber 34 for the pressure boost 23 and a chamber 32 counteracting this additional working chamber 34 are formed between the rotor 3 and the stator. The working chamber 23 for the pressure boost 23 can therefore be referred to as a pressure boost working chamber. The rotor 3 has a pressure medium accumulator 21 for a pressure medium 22 for actuating the hydraulic camshaft adjuster 1, said accumulator being formed substantially in the rotor hub 4. The rotor 3 has a central opening 31, into which a central valve 24 for controlling the pressure medium supply to the working chambers 15, 16, 17, 18, 19, 20, 34 can be inserted. The pressure medium accumulator 21 is connected hydraulically to the working chambers 15, 16, 17, 18, 19, 20. In this case, check valves 33, 35, 36 are arranged in the vanes 5, 6, 7 of the rotor 3 in order to allow additional pressure medium 22 to flow in from the pressure medium accumulator 21 when there is a reduced pressure in one of the working chambers 15, 16, 17, 18, 19, 20.

(8) FIG. 2 illustrates a hydraulic camshaft adjuster 1 having a stator 2 and a rotor 3, which can be switched via actuator 29. Here, the rotor 3 is connected to a camshaft 30 for conjoint rotation therewith and is rotatable relative to the stator 2. In this arrangement, the central valve 24, as control valve 27, is moved in the central opening 31 of the rotor 3 in order in this way to control the pressure medium supply to the working chambers 15, 16, 17, 18, 19, 20. Here, the pressure medium is supplied via a pressure medium pump P (not illustrated) from a reservoir 26. In this case, the pressure medium 22, in particular an oil, is pumped through a feed bore 39 in the camshaft 30 and fed to the central valve 24 via another feed bore 40. Via the corresponding openings 41, 42 in the central valve 24, the oil feed passages in the rotor 3 can then be supplied with pressure medium 22. During this process, both the pressure medium accumulator 21 and the working chambers 15, 16, 17, 18, 19, 20 can be filled. By means of an actuation of the actuator 29, the central valve 24 can be moved along a central axis 43 and thus open or close the oil feed passages.

(9) FIG. 3 illustrates a hydraulic camshaft adjuster 1 in a developed view. The hydraulic camshaft adjuster 1 has a stator 2 and a rotor 3. Working chambers 15, 18 are formed between the stator 2 and the rotor. FIG. 3 illustrates an adjustment of a hydraulic camshaft adjuster 1 according to an embodiment in the “retard” direction. In principle, the angle of rotation of the camshaft 30 with respect to the crankshaft is adjusted in the normal operation of the hydraulic camshaft adjuster 1 by supplying a first group of working chambers 15, 16, 17 with pressure medium and thereby enlarging the volume thereof, while the pressure medium is simultaneously displaced from a second group of working chambers 18, 19, 20 and the volume thereof is reduced. The working chambers 15, 16, 17, the volume of which is respectively increased as a group during this adjusting movement, are referred to in the sense as working chambers 15, 16, 17 of one effective direction, while the working chambers 18, 19, 20, the volume of which is simultaneously reduced, are referred to as working chambers of the opposite effective direction. The enlargement of the volume of working chambers 15, 16, 17 has the effect that the rotor 3 is rotated in the “advance” direction relative to the stator 2. An enlargement of the volume of working chambers 18, 19, 20 has the effect of adjusting the rotor 3 in the “retard” direction. In addition, the hydraulic camshaft adjuster 1 has a pressure boost 23, which comprises an additional working chamber 34 and a chamber 32 which counteracts the additional working chamber 34, said chambers likewise being separated by a vane 6 of the camshaft adjuster 1. In the case of an adjustment in the “retard” direction, this pressure boost 23 is not activated, and therefore the additional working chamber 34 and the oppositely acting chamber 32 are connected by oil supply lines 44, 45 to the reservoir 26. In this case, the central valve 24 is switched in such a way that the pressure medium 22 is delivered by the pressure medium pump 25 exclusively into the second group B of working chambers 18, 19, 20. A check valve 46 is provided between the pressure medium pump 25 and the central valve 24 in order to avoid a return flow of pressure medium 22 into the reservoir 26.

(10) FIG. 4 illustrates an adjustment of a hydraulic camshaft adjuster according to the embodiment in the “advance” direction without the use of the pressure booster 23. In this case, the pressure medium pump 25 is connected to the first group A of working chambers 15, 16, 17 via the central valve 24 and delivers the pressure medium 22 into this first group A of working chambers 15, 16, 17. Here, the volume of the first group A of working chambers 15, 16, 17 is enlarged and, in parallel, the volume of the second group B of working chambers is reduced, as a result of which the rotor is adjusted in the “advance” direction. During this process, the additional working chamber 34 of the pressure boost 23 and the chamber 32 is switched to an unpressurized state, as with an adjustment in the “retard” direction, and is connected by the oil supply lines 44, 45 to the reservoir 26.

(11) FIG. 5 illustrates an adjustment of the rotor 3 counter to the friction and drag torques of the camshaft 30. Here, the pressure boost 23 is configured in such a way that the maximum friction torque to be expected can be overcome to ensure an adjustment in the “advance” direction at the minimum pump pressure of the pressure medium pump 25. As described with respect to FIG. 3, the adjustment in the “retard” direction is generally uncritical since, in this case, the friction torques assist with the adjustment. However, an adjustment in the “advance” direction requires a higher adjusting torque since, in this case, the friction torque has to be overcome in addition. This is especially the case when the internal combustion engine is being operated with a reduced valve travel. For this purpose, a pressure boost 23 is implemented via the central valve 24, with an additional working chamber 34 being supplied with pressure and thus the hydraulically effective area at the vanes 5, 6 of the rotor being enlarged. During this process, the volume flow of the pressure medium 22 is divided by the central valve 24 into a first partial flow and a second partial flow, wherein the first partial flow is fed to the first group A of working chambers 15, 16, 17 via the oil supply passage 47, and the second partial flow is fed to the additional working chamber 34 of the pressure boost 23 via the oil supply passage 44. An additional vane 6 of the rotor 3 is thereby subjected to pressure, as a result of which the adjusting torque in the “advance” direction is increased. Alternatively, it is also possible for a plurality of additional working chambers 34 to be activated by the second partial flow, thereby making possible a corresponding adaptation of the boost ratio of the pressure boost 23.

(12) The selection of the additional working chamber 34, which assists an adjustment in the “advance” direction, is made possible via an additional switching position at the central valve 24. For this purpose, one or more additional openings are required in the central valve. In principle, the counter chamber 32 associated with the additional working chamber 34 is switched to an unpressurized state and connected to the reservoir 26. It represents a compensating volume and does not exert any force on the rotor 3 in normal operation. It is assumed that the hydraulic camshaft adjuster 1 is designed in such a way that an additional pressure boost in the “retard” direction is not necessary and that this is accomplished solely by pressurization of the second group B of working chambers 18, 19, 20.

(13) In the case of a hydraulic camshaft adjuster 1 according to the teachings herein, it is thus possible to adjust the rotor 3 in the “advance” direction counter to the friction and drag torques and using the selectable pressure boost 23, wherein the pressure medium throughput and the associated power dissipation is reduced as compared with the hydraulic camshaft adjusters 1 known from the prior art. It is thereby possible to increase the efficiency of the internal combustion engine and to reduce consumption.

LIST OF REFERENCE SIGNS

(14) 1 hydraulic camshaft adjuster 2 stator 3 rotor 4 rotor hub 5 vane 6 vane 7 vane 8 rib 9 rib 10 rib 11 annular chamber 12 pressure chamber 13 pressure chamber 14 pressure chamber 15 working chamber 16 working chamber 17 working chamber 18 working chamber 19 working chamber 20 working chamber 21 pressure medium accumulator 22 pressure medium 23 selectable pressure boost 24 central valve 25 pressure medium pump 26 reservoir 27 control valve 28 drive toothing 29 actuator 30 camshaft 31 central opening 32 chamber 33 check valve 34 working chamber 35 check valve 36 check valve 37 valve spring 38 valve ball 39 feed bore 40 feed bore 41 opening (in the central valve) 42 opening (in the central valve) 43 central axis 44 oil supply passage 45 oil supply passage 46 check valve 47 oil supply passage 48 oil supply passage