DE102020105452A1 - Camshaft adjuster with variable pressure ratio - Google Patents

Abstract

The invention relates to a hydraulic camshaft adjuster (1) of the vane cell type for a motor vehicle drive train, with working chambers (4) formed between a stator (2) and a rotor (3) The rotor (3) are subdivided into two sub-chambers (6, 7) which can be acted upon with hydraulic fluid in order to adjust the rotor (3) relative to the stator (2) in opposite directions of action, and an additional working chamber (8) which has an active chamber (9 ) for adjustment by means of liquid supply in the first effective direction and has a passive chamber (10) separated therefrom by a wing (5) of the rotor (3), the active chamber (9) and the passive chamber (10) being connected to supply channels (11), which are arranged in such a way that liquid can be fed to the active chamber (9) during operation and gas can be fed to the passive chamber (10) in a targeted manner.

Description

The invention relates to a hydraulic camshaft adjuster of the vane type for a motor vehicle drive train. The camshaft adjuster is used to adjust the phase position of a camshaft in relation to a crankshaft. The camshaft adjuster has a stator that is rotatably coupled to the crankshaft and a rotor that is rotatably coupled to the camshaft. The camshaft adjuster has working chambers formed between the stator and the rotor, the working chambers each being divided into two sub-chambers by a wing of the rotor. The partial chambers can be acted upon with hydraulic fluid in order to adjust the rotor relative to the stator in opposite effective directions. The camshaft adjuster has an additional working chamber serving as a pressure booster, which has an active chamber for adjustment by means of liquid supply in the first effective direction and a passive chamber separated from it by a wing of the rotor. An active chamber or an active chamber is understood to mean the partial chamber of a working chamber, the volume of which is changed, in particular increased, for adjustment in the assigned effective direction. A passive chamber or a passive chamber is understood to mean the partial chamber of a working chamber, the volume of which is changed, in particular reduced, in order to enable the active chamber to be changed or enlarged.

Such camshaft adjusters deal with the problem that the camshaft torques, which have a strong influence on the adjustment process, are usually asymmetrical due to the friction present in the valve train system. This means that the amplitude of the camshaft torques in one effective direction, in particular in the retarded direction, is greater than in the other effective direction, in particular in the advanced direction, because of the frictional component. This means that, for example, when the cylinder is switched off, only the frictional torques that act on the adjustment in one adjustment direction are reduced. This unequal amplitude can be increased due to the built-in high pressure pump.

In addition, camshaft adjusters are preferably used which have a small pressure ratio and thus require less oil for the adjustment than camshaft adjusters with a large pressure ratio and can achieve faster adjustment speeds.

At a low pump pressure, for example in the lower speed range, with a camshaft adjuster with a small pressure ratio it can happen that the adjustment in the other effective direction, in particular an advance direction, can no longer be adjusted against the frictional torque.

Such camshaft adjusters are already known from the prior art which have a pressure intensification formed by an additional working chamber that can be connected, the pressure intensification being built in for the (early) effective direction. For example, the WO 2018/196 904 A1 a hydraulic camshaft adjuster for adjusting the control times of gas exchange valves of an internal combustion engine, with a stator, which can be rotated synchronously with a crankshaft of the internal combustion engine, and a rotor which is rotatable relative to the stator and which rotates synchronously with a camshaft, with several webs being provided on the stator , which subdivide an annular space between the stator and the rotor into a plurality of pressure chambers, the rotor having a rotor hub and a plurality of vanes extending radially outward from the rotor hub, which divide the pressure chambers into two groups, each with one in a pressure medium circuit Incoming or outflowing pressure medium can be acted upon by working chambers with a different direction of action, as well as with a pressure medium accumulator for supplying the hydraulic pressure medium, the hydraulic camshaft adjuster having an additional, switchable one in at least one direction of action Has pressure intensification with which the rotor can be rotated with respect to the stator, the switchable pressure intensification taking place through the hydraulic connection of at least one further working chamber.

The prior art, however, always has the disadvantage that with these camshaft adjusters, in which the pressure ratio is different depending on the adjustment direction, to reduce the pressure ratio in one (late) effective direction on the pressurization of a (partial) working chamber to the active Adjustment is dispensed with, but this (partial) working chamber must be enlarged or reduced, although it is inactive / passive. This has a negative effect on the speed of the adjustment process.

It is therefore the object of the invention to avoid or at least mitigate the disadvantages of the prior art and to provide a camshaft adjuster which can cope with the increasing complexity in the valve train and the requirement for an oil pressure reduction in the engine. In particular, a camshaft adjuster is to be developed in which high adjustment speeds can be achieved with small pressure ratios and small amounts of hydraulic fluid without the functionality in a speed range being impaired.

In a device of the generic type, this object is achieved according to the invention in that the active chamber and the passive chamber are connected to supply channels which are arranged such that liquid can be supplied to the active chamber during operation and gas can be purposefully fed back to the passive chamber. This means that a supply channel for the passive chamber is designed and arranged in such a way that only or predominantly air is sucked into the passive chamber when the chamber volume is increased.

Accordingly, the invention relates to a hydraulic camshaft adjuster of the vane cell type for adjusting the phase position of a camshaft relative to a crankshaft for a motor vehicle drive train. The camshaft adjuster has a stator rotatably coupled to the crankshaft and a rotor rotatably coupled to the camshaft, preferably arranged radially inside the stator and rotatable relative to the stator. The camshaft adjuster has working chambers formed between the stator and the rotor, each of which is subdivided into two sub-chambers, which are also referred to as the A-chamber and the B-chamber, by a radially protruding wing of the rotor. The sub-chambers can be pressurized with hydraulic fluid in order to adjust the rotor relative to the stator. The sub-chambers each act in opposite directions. This means that the rotor can be adjusted relative to the stator by applying pressure to one sub-chamber in the late direction and can be adjusted in the early direction by applying pressure to the other sub-chamber. When a partial chamber is pressurized, the hydraulic fluid is displaced from the other partial chamber. According to the invention, the camshaft adjuster has an additional working chamber which has an active chamber for adjustment by means of liquid supply in the first effective direction and a passive chamber separated therefrom by a wing of the rotor, the active chamber and the passive chamber being connected to supply channels which are arranged so that during operation liquid can be fed to the active chamber and gas can be fed to the passive chamber in a targeted manner, for example by means of suction, ie can be fed in for refilling. In other words, the passive chamber is filled with air to change or increase its volume.

Because the air has a significantly lower resistance than liquid, such as oil, when it flows in or is displaced, the adjustment process is braked less by the passive chamber than if oil were sucked into the passive chamber. This has the advantage that the problem can be avoided that the adjustment process is slowed down by the passive chamber, since the passive chamber has to enlarge or reduce during the adjustment. In addition, the passive chamber does not require any liquid, in particular oil, in order to enlarge, so that sufficient liquid, in particular oil, can be made available to the active chamber or the sub-chambers adjusting in the effective direction. Thus, the influence of an enlargement of the passive chamber on the adjustment speed is reduced and no or less oil is required from an oil reservoir for the passive chamber.

Advantageous embodiments are claimed in the subclaims and are explained in more detail below.

According to a preferred embodiment, the supply channels can be designed as a first supply channel for the passive chamber and as a second supply channel separate therefrom for the active chamber. In this way, the fluid flows, namely a liquid flow / oil flow and a gas flow / air flow, can be implemented separately from one another.

It is particularly preferred if the first supply channel is connected to a reservoir for storing hydraulic fluid. Alternatively or additionally, it is preferred if the second supply channel is connected to a reservoir, in particular the same reservoir, for storing hydraulic fluid. Hydraulic fluid for adjustment is usually supplied to the sub-chambers from this reservoir by sucking hydraulic fluid into the sub-chamber to be adjusted when there is a negative pressure. For the adjustment, liquid, such as oil, is sucked into the sub-chambers in order to avoid oscillations.

The reservoir can be formed in a cover that is fixed, for example, to the stator. The cover closes the camshaft adjuster in the axial direction. The hydraulic fluid can be fed to the (partial) working chambers via recesses in the axial direction, for example with the interposition of non-return valves.

In an advantageous development, an inlet of the first supply channel in the reservoir can be arranged radially further inward than an inlet of the second supply channel in the reservoir. This has the advantage that, due to the different density and the forces caused by rotation, gas, in particular air, is often present in the radially inner region, and liquid, in particular oil, is often present in the radially outer region.

Furthermore, it is advantageous if, during operation of the camshaft adjuster, the reservoir has a liquid area in which liquid is present and a gas area in which gas is present, the inlet of the first supply channel in the gas area is arranged. In other words, the supply channel for the passive chamber is arranged in such a way that it opens into the area of the reservoir in which there is air. This ensures that only the air and no oil is sucked in by the passive chamber.

It is therefore particularly expedient if the inlet of the first supply channel is arranged in a radially inner third, more preferably in a radially inner quarter, of the camshaft adjuster. This means that the inlet of the first supply channel has the smallest possible radial distance from the axis of rotation in order to allow the passive chamber to communicate with the reservoir at the point where the air is in the reservoir, i.e. below an oil level / oil level of the reservoir.

Furthermore, it is advantageous if the first supply channel is designed and positioned in such a way that when gas located in the passive chamber is returned to the reservoir, leakage fluid that has passed into the passive chamber is forcibly guided into the reservoir. This ensures that the leakage oil, which is pressed out by the passive chamber, ends up in the reservoir again.

In addition, it is preferred if the first supply channel is designed so that it allows a flow of fluid from the reservoir into the passive chamber and from the passive chamber into the reservoir, and / or the second supply channel is designed such that it allows a flow of fluid blocks from the active chamber into the reservoir, for example with the interposition of a check valve. In other words, in contrast to the second supply channel, a flow in both directions of flow is enabled in the first supply channel, since no check valve is provided. This ensures that the air can flow in and can also be pressed out (together with the leakage oil).

According to a preferred embodiment, the first supply channel can have a first channel section which extends radially inward in the rotor from a radially inner side of the passive chamber, and a second channel section which extends in the axial direction in the rotor. The first supply channel is thus formed by two holes, for example bores, in the rotor of the camshaft adjuster. The first channel section starts in the passive chamber and is introduced radially inwards by the rotor, for example drilled. The second channel section is introduced axially, for example drilled, laterally, in particular on an axial side of the reservoir. The radial distance between the second channel section and the axis of rotation is as small as possible that it opens into the reservoir at a point where there is air when the camshaft adjuster rotates.

In a preferred development, the first channel section is formed by a blind hole / blind hole. Alternatively or in addition, the second channel section is formed by a blind hole / blind hole. The two channel sections are arranged so that they cross each other.

In other words, the invention relates to a camshaft adjuster with a pressure intensification that acts as a function of the adjustment direction. The pressure intensification is formed by an additional working chamber, in which a partial chamber (passive chamber) that adjusts in one effective direction is dispensed with, so that the pressure intensification is reduced in this effective direction. According to the invention, a supply channel for this passive chamber is designed and positioned in such a way that when the chamber volume is increased, only air is sucked into the passive chamber from a reservoir, and when the chamber volume is reduced, the oil that has leaked into the passive chamber returns to the reservoir of the camshaft adjuster is supplied.

• 1 eine schematische Längsschnittdarstellung eines erfindungsgemäßen Nockenwellenverstellers,
• 2 eine schematische Querschnittsdarstellung des Nockenwellenverstellers, und
• 3 eine vergrößerte Darstellung eines Ausschnitts aus 2.

The invention is explained below with the aid of drawings. Show it:

• 1 a schematic longitudinal sectional view of a camshaft adjuster according to the invention,
• 2 a schematic cross-sectional view of the camshaft adjuster, and
• 3 an enlarged view of a section 2 .

The figures are merely of a schematic nature and are used exclusively for understanding the invention. The same elements are provided with the same reference symbols.

1 until 3 show a hydraulic camshaft adjuster according to the invention 1 of the vane type for an automotive powertrain. The camshaft adjuster 1 is used to adjust the phase position of a camshaft in relation to a crankshaft. The camshaft adjuster 1 has a stator that is rotatably coupled to the crankshaft 2 and a rotor rotatably coupled to the camshaft 3 . Between the stator 2 and the rotor 3 Chambers of labor 4th educated. Each of the labor chambers 4th is each through a wing 5 of the rotor 3 in two sub-chambers 6th , 7th lower part. A first sub-chamber 6th is usually referred to as the A chamber and a second sub-chamber 7 is usually referred to as the B chamber. The two sub-chambers 6th , 7th are each used to adjust the rotor 3 in relation to the stator 2 hydraulic fluid, in particular oil, can be acted upon in opposite directions of action.

The camshaft adjuster 1 has an additional working chamber 8th on. The additional work chamber 8th is analogous to one of the working chambers 4th built up. The additional work chamber 8th has an active chamber 9 for adjustment by means of liquid supply in the first effective direction and one of them by a wing 5 of the rotor 3 separate passive chamber 10 . For example, the additional working chamber 8th be switched on if necessary in order to increase a pressure boost in the first effective direction. The additional work chamber 8th thus forms a variable pressure ratio. The active chamber 9 and the passive chamber 10 are with supply channels 11 tied together. The supply channels 11 are arranged so that during operation, ie during adjustment, the active chamber 9 Liquid, in particular oil, can be supplied and the passive chamber 10 targeted gas can be tracked. In other words, it can go into the passive chamber 10 Gas, especially air, are sucked in to enlarge the chamber volume.

The supply channel 11 , through the gas into the passive chamber 10 can be fed, has a first channel section 12th and a second channel section 13th on. The supply channel 11 connects the passive chamber 10 with a reservoir 14th in the camshaft adjuster 1 .

The first canal section 12th extends from a radial inside of the passive chamber 10 radially inwards. The first canal section 12th is in the rotor 3 educated.

For example, the first channel section 12th designed as a blind hole / a blind hole opening. The second canal section 13th extends in the axial direction. The second canal section 13th is in the rotor 3 educated. For example, the second channel section 13th designed as a blind hole / a blind hole opening. The first canal section 12th and the second channel section 13th are connected to one another, for example in the manner of an intersection at which the two channel sections meet 12th , 13th cross / intersect. The second canal section 13th is with the reservoir 14th tied together.

The supply channel (not shown in the figures) through the liquid, here oil, into the active chamber 9 can be fed, connects the active chamber 9 and the reservoir 14th with the interposition of a check valve 15th . This allows the oil to enter the active chamber 9 sucked in when there is negative pressure. The reservoir 14th is in a cover of the camshaft adjuster 1 educated. Due to the rotation of the camshaft adjuster 1 the oil is pressed radially outwards. As a result, oil is present in a radially outer region and air is present in a radially inner region. The oil area is defined by the in 1 indicated oil levels 16 limited. An entrance of the supply channel of the active chamber 9 is in the reservoir 14th arranged in the oil area. An entrance of the supply channel 11 the passive chamber is in the reservoir 14th arranged in the air area. The entrance to the active chamber 9 is thus in the reservoir 14th radially further out than the entrance of the passive chamber 10 arranged.

The sub-chambers 6th , 7th are each through a hydraulic channel with the interposition of a non-return valve 17th with the reservoir 14th connected to oil in the sub-chambers 6th , 7th to be able to suck in. An inlet of the hydraulic channels of the sub-chambers 6th , 7th is arranged in the oil area. The entrances to the sub-chambers 6th , 7th are radially further out than the entrance of the passive chamber 10 arranged. For example, the entrance to the passive chamber 10 in a radially inner third of the camshaft adjuster 1 be arranged. This is through the supply channel 11 the passive chamber 10 only or mostly air, ie no or hardly any oil, into the passive chamber 10 sucked in.

An influx / influx 18th into the passive chamber 10 is in 1 indicated with a dashed arrow. The air is therefore from a radially inner area, which is as close as possible to the axis of rotation, into the passive chamber 10 guided. When reducing the volume of the passive chamber 10 can, if necessary, in the passive chamber 10 Any oil, such as leakage oil, from the passive chamber 10 be pushed out and the reservoir 14th are fed. An effluent / expiration 19th from the passive chamber 10 is indicated with an arrow.

List of reference symbols

1

Camshaft adjuster

2

stator

3

rotor

4th

Work chamber

5

wing

6th

first subchamber

7th

second sub-chamber

8th

Additional work chamber

9

Active chamber

10

Passive chamber

11

Supply channel

12th

first channel section

13th

second channel section

14th

reservoir

15th

check valve

16

Oil level

17th

check valve

18th

Inflow / inflow

19th

Downflow / drain

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• WO 2018/196904 A1 [0005]

Claims (10)

Hydraulic camshaft adjuster (1) of the vane type for a motor vehicle drive train, with working chambers (4) formed between a stator (2) and a rotor (3), the working chambers (4) each being supported by a wing (5) of the rotor (3) are divided into two sub-chambers (6, 7), which can be acted upon with hydraulic fluid in opposite directions of action in order to adjust the rotor (3) relative to the stator, and an additional working chamber (8) which has an active chamber (9) for adjustment by means of liquid supply into the first effective direction and a passive chamber (10) separated therefrom by a wing (5) of the rotor (3), characterized in that the active chamber (9) and the passive chamber (10) are connected to supply channels (11) which are arranged in this way that liquid can be fed to the active chamber (9) during operation and gas can be fed to the passive chamber (10) in a targeted manner. Camshaft adjuster (1) Claim 1 , characterized in that the supply channels (11) are designed as a first supply channel (11) for the passive chamber (10) and as a separate second supply channel for the active chamber (9). Camshaft adjuster (1) Claim 2 , characterized in that the first supply channel (11) and / or the second supply channel are connected to a reservoir (14) for storing hydraulic fluid. Camshaft adjuster (1) Claim 3 , characterized in that an inlet of the first supply channel (11) in the reservoir (14) is arranged radially further inward than an inlet of the second supply channel (11) in the reservoir (14). Camshaft adjuster (1) Claim 4 , characterized in that the reservoir (14), when the camshaft adjuster (1) is in operation, has a liquid area in which liquid is present and a gas area in which gas is present, the inlet of the first supply channel (11) in the gas area is arranged. Camshaft adjuster (1) Claim 4 or 5 , characterized in that the inlet of the first supply channel (11) is arranged in a radially inner third of the camshaft adjuster (1). Camshaft adjuster (1) according to one of the Claims 3 until 6th , characterized in that the first supply channel (11) is designed and positioned in such a way that when gas in the passive chamber is returned to the reservoir (14), leakage fluid that has entered the passive chamber is forced into the reservoir (14). Camshaft adjuster (1) according to one of the Claims 3 until 7th , characterized in that the first supply channel (11) is designed so that it allows a flow of fluid from the reservoir (14) into the passive chamber (10) and from the passive chamber (10) into the reservoir (14), and / or the second supply channel is designed such that it blocks a flow of fluid from the active chamber (9) into the reservoir (14). Camshaft adjuster (1) according to one of the Claims 2 until 8th , characterized in that the first supply channel (11) has a first channel section (12) which extends from a radial inside of the passive chamber (10) radially inward in the rotor (3), and a second channel section (13) which extends extends in the axial direction in the rotor (3). Camshaft adjuster (1) Claim 9 , characterized in that the first channel section (12) and the second channel section (13) are each formed by a blind hole, the two blind holes crossing each other.

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