Patent Application
20240280147
The disclosure relates to a hydraulic assembly, a friction clutch and a method for operating a friction clutch.
So-called friction clutches are known in the prior art. For example, DE 10 2011 108649 A1 discloses a torque transmission unit having a friction clutch and a hydraulic actuation system, which comprises a stepped piston unit having a stepped piston, which comprises a first piston portion that is movable in a first pressure chamber and has a first, smaller hydraulically active effective area and a second piston portion that is movable in a second pressure chamber and has a second, larger hydraulically active effective area. Here, the first and second pressure chambers are fluidically connected by means of an overflow line, as a function of a position of the first piston portion. According to DE 10 2011 108649 A1, an actuating piston cooperates with the friction clutch to selectively actuate the torque transmission unit.
Furthermore, DE 10 2015 20 4673 B3 discloses a hydraulic assembly for a friction clutch, which comprises a switching unit having an input, having a closable first output and having a closable second output. The switching unit is fluidically connected to the volume flow source via the input by means of the hydraulic supply line, with the lower input pressure being converted into a higher output pressure by means of a pressure intensifier.
However, the aforementioned solutions do not constitute an optimal solution as regards rapid passage through the initially contactless approach phase with very low force up to the bite point and the subsequent contact and force transmission phase with high force application and very little or no change in the position of the working piston.
The object is therefore to provide a hydraulic assembly for a friction clutch that enables these two steps or phases to run better.
For this purpose, a hydraulic assembly having one or more of the features disclosed herein, a friction clutch having one or more of the features disclosed herein and a method having one or more of the features disclosed herein are provided. Advantageous embodiments are set out below and in the claims.
The hydraulic assembly according to the disclosure for driving a friction clutch comprises a hydraulically drivable stepped piston and a pump driving at least the stepped piston, wherein the stepped piston comprises a working piston having a piston chamber, wherein the working piston displaceably, in particular linearly displaceably, arranged in the piston chamber divides this piston chamber into a first working chamber (main chamber) and an auxiliary chamber. In this respect, the auxiliary chamber can be a closed or partially open chamber, this auxiliary chamber in a structurally simple embodiment being merely a guide chamber, for example a cylindrical guide chamber. Such a guide chamber is completely or partially open at the end opposite the working piston. The working piston is moreover mechanically connected to an auxiliary working piston or has a portion which is designed as an auxiliary piston and which can be driven hydraulically via a second working chamber. During flooding and/or pressure build-up in the two working chambers, these drive the stepped piston in a common direction engaging the friction clutch. The inflow of hydraulic fluid and build-up of pressure in the auxiliary chamber act in the opposite direction, i.e. disengaging the friction clutch.
In the present case, “friction clutch” should not be understood as limiting. Rather, “friction clutch” should be understood quite generally as meaning a torque transmission device in the form of a frictional and/or interlocking clutch or brake.
Furthermore, at least one control valve is included, which is arranged in at least one line path between a working chamber of the stepped piston and the pump. A first line path leads via a first supply line from the pump to the second, smaller working chamber; there is no flow through the control valve in this case. A second line path leads from the pump via the first supply line, the control valve and a second supply line to the first, larger working chamber. The stepped piston has a (working) plunger which is guided through the auxiliary chamber and which is likewise moved linearly and by means of which the friction clutch can be acted on mechanically. The first and second line paths are connected via a first line portion of the second supply line, which line portion branches off from the first supply line, and a control valve. The control valve can assume at least two valve positions, with the first line portion of the second supply line being at least partially blocked in at least one of the valve positions.
The advantage here is that, when the piston moves during the approach phase, also called the air travel region, only the smaller volume of the second working chamber of the stepped piston is filled by the pump, such that the working piston can be displaced quickly. Application of the larger volume and thus initiation of a high contact pressure over the large effective area is only initiated on or shortly before or shortly after reaching of the bite point (TP), at which the line path between the pump and the first working chamber (main working chamber) is opened by means of the control valve.
An improved embodiment consists in that, parallel to the control valve, there is a further line connection through a first check valve between the first and the second line path. This can be used to deliver hydraulic fluid from the large, first working chamber, bypassing and/or parallel to the control valve, to the tank during the opening movement of the stepped piston, in particular during negative pressure operation of the pump.
According to a further improved embodiment, the second line path leads from the working chamber, via a second line portion of the second supply line, via a branch node parallel to the control valve and a discharge line, and into a tank. Ideally, a second check valve is arranged in the discharge line between the branch node and the tank and provides a blocking action in the direction of the tank. As a result, the drainage line becomes a pressure equalization line in reverse or suction mode, via which hydraulic fluid can flow into the system if necessary.
According to a further improved embodiment of the hydraulic assembly, the control valve in the second valve position either completely blocks, i.e. interrupts, the first line portion of the second supply line, or establishes a connection with a check valve function that allows a flow from the second line path into the first line path and, in the opposite direction, blocks, in particular blocks in pressure-dependent manner, namely the first line path from the pump to the first working chamber (main working chamber.)
In a further embodiment, the second working chamber is smaller than the working chamber, preferably the second working chamber is at least 10% smaller, in particular more than 20% smaller than the first working chamber (main working chamber) and/or the effective areas of the working chambers are analogously in the ratio of 0.9 or 0.8 to each other.
Advantageously, the control valve is a passive control valve which switches from one valve position to the other valve position when a defined fluid pressure is reached in one of the two supply lines, in particular in the first supply line. In an alternative embodiment, the control valve is an electrically switchable solenoid valve.
In a further advantageous embodiment, a displacement sensor is arranged on or at the working piston of the stepped piston and the displacement sensor information is used to control the control valve. A further improvement consists in the fact that the hydraulic assembly is monitored by evaluating the fluid pressure in the first and/or the second supply line and the data from the displacement sensor on the working piston. Here, TARGET values/ranges are compared with ACTUAL values/ranges, and control and/or warning information is derived for the vehicle or the operator.
According to a further embodiment and/or improvement, at least one pressure sensor is provided in one of the lines or line portions, such that the bite point can be identified and/or determined via a pressure measurement. This determination is made by identifying a pressure gradient and/or an absolute pressure in a line.
In a further embodiment, provision is made for a cooling and lubrication line to branch off from the first supply line and upstream of the control valve, with a (fluid) orifice being arranged in the cooling and lubrication line, via which orifice only a very little fluid flow is guided. An improvement consists in the fact that the free end of the cooling and lubrication line has a diffuser, which is arranged adjacent to a free end of the working piston of the stepped piston, and is directed in particular towards the friction clutch to be engaged and disengaged. The diffuser can in particular be a slit nozzle or a series of individual nozzles.
In a further embodiment, a tank is arranged upstream of the pump, which is used as a hydraulic reservoir and which is connected to the pump via a supply line. The pump is advantageously a double-acting pump that can operate by both pressing and sucking on the first supply line. The tank is advantageously a closed vessel that can be operated under negative pressure of up to 0.8 bar, ideally up to 0.5 bar.
The disclosure further encompasses a friction clutch having an axis of rotation for releasably connecting an output shaft to a consumer, which comprises or has the following
Furthermore, the disclosure includes a method for operating a friction clutch, wherein a pressure plate is moved against a consumer-side friction disk by means of a stepped piston which has effective areas of different sizes. The stepped piston has at least one first working chamber (main working chamber) and an auxiliary chamber. The auxiliary chamber is opposite the first working chamber and moves in the opposing direction when flooded. Furthermore, a second working chamber is included, which acts on the stepped piston in the same direction to the first working chamber when flooded. Here, the propulsion to move the stepped piston and engage the friction clutch takes place in at least two steps.
In the first step, the working piston is driven faster with the same drive power of a drive unit, in particular a pump, than in the second step. For this purpose:
Advantageously, in this respect a hydraulic assembly according to one of the aforementioned variant embodiments is used or operated.
The disclosure is explained by way of example below with reference to the drawings, in which:
In
The first line path leads from the pump 7, parallel to the control valve 6, into the second, smaller working chamber 5.3 of the stepped piston 3. The second supply line path from the pump 7 to the first working chamber 5.1 is divided in two and leads via the first supply line 20 from the pump 7 to a line node, and there via the second supply line 21 to or through the control valve 6, which in the present case is configured as a 2/2-way valve. Downstream of the control valve 6, the second supply line 21 leads to the first working chamber 5.1. A first check valve 17.1 is provided between the first and second line paths, parallel to the control valve 6, which connects the first supply line 20 to the second line portion 21.2 of the second supply line 21. A further, second check valve 17.2 is provided in the discharge line 23, which opens into the second supply line 21 at the line node between the first and second line portions. As can be seen as a dashed line in
The pump 7 is likewise connected to the tank 8 via a suction line 19. Furthermore, a coolant and lubricant line 24, in which an orifice 9 is provided, leads to a diffuser 10, which is arranged opposite the friction clutch 2 and lubricates and cools the friction package 12. The naming of the elements and especially the lines refers to the work step when pressure is built up. This is not intended to be limiting and is only intended to facilitate understanding. Taking the “suction line 19” as an example, it is immediately obvious to a person skilled in the art that in the suction mode of the pump 7, when it is operating with negative pressure on the first supply line 20, the “suction line 19” is operated as a “pressure line”, without it being renamed for this purpose.
In the starting position, with the friction package 12 disengaged, the control valve 6 is biased into and held in the valve position 6.2 by the spring 6.1, as shown in
Feed is very fast due to the quickly filling second, small working chamber. The friction package 12 comes into contact, such that feed largely ends and the switching point 51 (
For disengagement of the friction package 12 through return movement of the working piston 4.1, the pump 7 is put into suction mode such that it applies suction to the first supply line 20 and thus to the entire supply line path, whereby the working piston 4.1 moves to the right and at the same time the auxiliary chamber 5.2 grows and fills with hydraulic fluid from the tank 8. The sequences are analogous to the previous steps. Via the two check valves 17.1 and 17.2, a pressure equalization in the line system can be established in both valve positions 6.1, 6.2 or the targeted return movement of the stepped piston can be initiated by a difference in resistance in the line system. Advantageously, in suction mode, a pressure gradient relative to the first working chamber 5.1 is provided through the direct first line path to the second working chamber 5.3 via the control valve 6 or the check valves 17.1 and 17.2, such that the pump 7 generates a greater negative pressure in the second working chamber 5.3 in suction mode. During normal operation, however, no negative pressures or only very slight negative pressures are built up because the energy stored in the clutch by engagement ensures that the fluid is forced out of the working chambers 5.1, 5.3. The pump 7 is driven substantially in the opposite direction, so that the (hydraulic) fluid can flow in a defined manner, i.e. in the active delivery direction of the pump 7, and the pressure in the line 20 can be reduced in a targeted manner.
In an embodiment which is not shown, the auxiliary chamber 5.2 can be fluidically pressurized for resetting the stepped piston 3, and in an alternative embodiment a spring or an elastomer is arranged in the auxiliary chamber 5.2, such that the working piston 4 is subjected to an opening force.
The embodiment shown in
Finally,
| Number | Date | Country | Kind |
|---|---|---|---|
| 102021120717.7 | Aug 2021 | DE | national |
This application is the U.S. National Phase of PCT Appln. No. PCT/DE2022/100501, filed Jul. 13, 2022, which claims priority to German Patent Application No. 10 2021 120 717.7, filed Aug. 10, 2021, the entire disclosures of which are incorporated by reference herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/DE2022/100501 | 7/13/2022 | WO |
