WO2020201234A1

WO2020201234A1 - Hydraulic system and method for actuating same

Info

Publication number: WO2020201234A1
Application number: PCT/EP2020/059013
Authority: WO
Inventors: Christian Anzt
Original assignee: Magna Pt B.V. & Co. Kg
Priority date: 2019-04-04
Filing date: 2020-03-30
Publication date: 2020-10-08
Also published as: DE102019204858A1

Abstract

The invention relates to a hydraulic system (1) comprising two hydraulic actuators (A1, A2) for actuating clutches (K1, K2) in a dual clutch transmission, wherein the actuators (A1, A2) are connected to an oil tank (3) arranged separately from the oil sump (2) via respective pump assemblies (10, 20), and the clutches (K1, K2) are cooled out of the oil sump (2) via a separate pump assembly (30). Each pump path (14, 24) to the actuators (A1, A2) is connected to the pump path (34) of the cooler by means of a respective non-return valve (40, 41).

Description

Hydraulic system and method for controlling the same

The invention relates to a hydraulic system with a valve arrangement and a method for controlling the system for transmissions with pump actuators and with a separate oil tank.

State of the art

Double clutch transmissions are preferably used in passenger cars. A dual clutch transmission generally has two coaxially arranged transmission input shafts, each of which is assigned to a sub-transmission. A clutch is assigned to each of the transmission input shafts, via which the transmission input shaft of the respective sub-transmission can be non-positively coupled to the output of a motor, an internal combustion engine of a motor vehicle and / or an electrical machine.

While driving, one of the sub-transmissions is typically active, which means that the transmission input shaft assigned to this sub-transmission is coupled to the engine via the clutch assigned to it. A gear is engaged in the active sub-transmission that provides a current transmission ratio. A control determines whether the next higher or next lower gear should be engaged depending on the driving situation. This gear, which is likely to be used next, is engaged in the second, inactive sub-transmission. For a gear change, the clutch of the inactive sub-transmission is closed while the hitch of the active sub-transmission is opened. It is preferred if the opening of the clutch of the active sub-transmission and the closing of the clutch of the inactive sub-transmission overlap in such a way that there is no or only a slight power flow interruption from the engine to the drive shaft of the motor vehicle. As a result of the gear change, the previously active partial transmission becomes inactive, while the previously inactive partial transmission becomes the active partial transmission. Then in the the gear that is likely to be required next can now be engaged.

The clutches are usually cooled by a fixed displacement pump driven by an internal combustion engine. At least one control or regulating valve is used for needs-based clutch cooling. The accuracy of the volume flow used to cool the clutch depends heavily on the control valve used. The hydraulic medium conveyed by the pump is usually cooled by a cooler and then fed to a cooling system assigned to the clutches, so that only one volume flow of cooling medium is available for both clutches. The joint cooling of the clutch deteriorates the control quality of the clutches.

From DE 10 2011 100 836 A1 a cooling is known in which the volume control valve supplies the hydraulic medium flow to a first cooling associated with the clutches in at least one first switching state and a second cooling associated with the clutches in at least one second switching state. The pump has an electric drive and is operated at a variable speed.

Regardless of the cooling tasks of the hydraulic circuit, the two sub-transmissions must perform coupling tasks for which they are each provided with an actuator. These actuators are each connected to an electric pump, so that the number of pumps and the required electric drives increases. In addition there is an electrically driven pump, which is provided for connecting an electric drive machine.

A hydraulic system is known from DE 10 2014 114 770 A1, which is used to actuate a dual clutch transmission and a KERS accumulator.

Such a hydraulic arrangement must operate the actuators of the dual clutch transmission reliably and ensure that the clutches are cooled.

For this purpose it is known from the prior art to use a separate oil tank in addition to an oil sump, which is generally sealed against the oil sump. The oil level in the oil tank must be kept above the oil level in the oil sump during normal operation, with the oil tank having an overflow to the oil sump.

As shown schematically in FIG. 1, oil thrown off by the clutch is returned to the oil tank in suitable devices.

A series process-safe hermetic sealing of the separate oil tank to the oil sump is complex and expensive or requires at least one additional component.

If the oil tank is not hermetically sealed to the oil sump, the oil level in the oil tank sinks over time due to oil leaks and adapts to the oil level in the oil sump. Depending on the geometric arrangement of the position of the suction filter opening of the actuators and depending on the inclination of the gearbox, it is possible that at least one pump of an actuator for clutch actuation cannot suck in any oil.

The process of filling the oil tank also becomes problematic if the coupling does not turn and no longer spins off oil and thus feeds it into the return line.

Another problem arises from the proportions of air contained in the hydraulic system. After the vehicle is parked, the oil drains from all components except for the oil level in the separate oil tank, so that air flows in through leakage gaps, especially at the rotary unions of the clutch. This air must be displaced from the clutch piston and the oil lines when the engine is restarted before the next clutch, which leads to initial delays. Furthermore, incomplete ventilation of the clutch pistons and the oil lines leads to reduced hydraulic stiffness and thus to persistent dynamic losses in the hydraulic control and also to worsened control accuracy, since the air content is not determined in practice and depends on the control parameters does not react accordingly.

It is therefore the object of the invention to create a hydraulic system which is designed for actuators actuation and cooling of clutches and coupling-related components and can be easily vented and filled with oil. Description of the invention

The object is achieved with a hydraulic system with at least one hydraulic actuator (A1, A2) for actuating at least one clutch element, the at least one actuator being connected via a pump arrangement to an oil tank arranged separately from the oil sump, and the clutch element via a separate pump arrangement is cooled out of the oil sump, the pump path to the at least one actuator being connected to the pump path of the cooling with a check valve.

The object is also achieved with a hydraulic system with two hydraulic actuators for actuating the clutches in a dual clutch transmission, where the actuators are connected via respective pumps to an oil tank separated from the oil sump, and the clutches from a separate pump assembly are cooled out of the oil sump, wherein the pump paths to the actuators are each connected to the pump path of the Küh treatment with a check valve.

The design of the hydraulic system prevents any loss of function due to a lack of oil in the oil tank.

The object is also achieved with a method for operating the hydraulic system. In normal operation, the pump paths of the actuators are subjected to a higher pressure than the pump path of the cooling system, with the non-return valves remaining closed. Normal operation is the state of the hydraulic system in which the actuators actively operate a clutch element and the clutch elements are cooled.

A particular advantage is shown when the hydraulic system is vented by activating the pump arrangement for cooling and the two further pump paths of the actuators being acted upon with displaced air from the clutch, with the check valves being opened. The procedure allows active venting without initial delays. The good ventilation means that there are no dynamic losses due to reduced hydraulic rigidity in the hydraulic system. Additional leaks such as covers for ventilation are no longer required.

The oil tank can be filled when the pump assemblies of the actuators slowly reverse and transport air into the oil tank via suction filters. The oil tank can always be kept full to the maximum so that the oil level in the oil sump can be reduced. This reduces churning losses in the couplings.

In the method, a control for filling is used, with a pump path to an actuator and the pump path for cooling being activated and the passive pump path being supplied with oil via the associated open check valve, which is fed into the oil tank.

Example of the invention

An embodiment of the invention is shown in the figures and is described below.

Figure 1 shows a Flydraulik system in the prior art,

Figure 2 shows a hydraulic system according to the invention in normal operation,

Figure 3 shows the hydraulic system during venting,

Figure 4 shows the hydraulic system when filling the oil tank,

Figure 5 shows a hydraulic system during venting for a planetary gear unit,

FIG. 6 shows a hydraulic system during the venting for a manual transmission with a hydraulic clutch.

Figure 1 shows a hydraulic system 1 shown schematically. Clutches K1 and K2 are operated by actuators A1 or A2, respectively. The actuators are each hydraulically connected to a pump arrangement 10 or via pump connections 14, 24 20 connected. The pump arrangements 10, 20 each contain an electrically operated pump 11 or 21. The electric pumps 11, 21 suck in oil via filters 12, 22 from an oil tank 3. The pumps 11, 21 apply pressure to the piston in the actuators A1, A2 and thus actuate the clutches K1, K2.

The oil is fed back into the oil tank 3 in the pump arrangements 10, 20 via additional leaks and diaphragms 13, 23 arranged in parallel.

There is a further pump arrangement 30 for cooling the clutch, which also contains an electrically driven pump 31. The pump 31 sucks oil from the oil sump 2 via a filter 32 and conveys oil via the pump path 34 to a clutch stator in the double clutch. The oil is thrown abge when the double clutch rotates and partially collected by an oil return device and passed to the oil tank 3.

The arrangement according to the invention is shown in FIG. Between the pump path 14 of the pump arrangement 10 and the pump path 34 of the pump arrangement 30 for cooling, a check valve 41 is arranged which opens when the pressure on the side of the pump path for cooling is greater than the pressure in the pump path 34 of the pump arrangement 10 .

The second pump arrangement 20 is provided with a check valve 40 in the same way between the pump path 24 and the pump path 34 of the cooling system.

Figure 2 shows the position of the check valves in normal operation. The pump arrangement 30 for cooling pumps oil from the oil sump 2 to cool the clutch K1,

K2. In the area of the check valves 40, 41, that is, close to the clutches K1, K2, the pump path 34 is almost pressureless, since centrifugal forces throw the oil out of the clutch in the following oil path.

As a result, the pressure in the pump paths 14, 24 is higher than in the pump path 34 of the cooling and the check valves 40, 41 remain closed. For this purpose, the inactive clutch is also subjected to a minimum pressure via the pump path so that the check valves remain closed. In Figure 3, the situation is shown when the hydraulic system is vented.

For venting, only the electric pump 31 of the pump assembly 30 of the Küh treatment is operated, which sucks oil from the oil sump 2.

The other two pumps 11 and 22 are inactive. Due to the increased pressure in the pump path 34 compared to the pump paths 14 and 24, the check valves 40 and 41 open.

The air in the pump paths 14 and 24 is displaced in the direction of the pump assemblies 10 and 20. Both electric pumps 11 and 21 rotate slowly backwards and convey air out of the paths in the direction of the oil tank 3. The rotation of the two pumps can be generated passively by the injected air or it can take place actively by controlling the pumps.

Bleeding takes place when the hydraulic system starts.

FIG. 4 shows the situation when the oil tank is filled. In this example, the pump arrangement 10 is activated for the clutch K1. At the same time, the pump arrangement 30 is operated for cooling. The check valve 41 remains closed because the pressure in the pump path 14 is higher than in the pump path 34 of the cooling. Since the pump arrangement 20 is not active, the check valve 40 is open for cooling because of the higher pressure of the pump arrangement 30. As a result, oil flows from the pump arrangement 30 for cooling through the pump arrangement 20 and the filter 22 into the oil tank 3.

The oil tank 3 is filled in the same way via the other pump arrangement 20 for the clutch K2.

In Figure 5, a further embodiment of the hydraulic system is shown, which is provided for a planetary gear set KP for internal combustion engine and / or electric drive machines with at least one hydraulically actuated and hydraulically cooled clutch K1 and at least one hydraulically actuated and hydraulically cooled brake. These components are summarized in the application under coupling elements. As an alternative, further structural designs are conceivable that allow a transition from one gear to another, such as the use of two brakes or two clutches. However, this list of design configurations is not intended to be exhaustive.

The functions “venting” and “filling oil tank” are possible in the same way as in the double clutch transmission described so far.

Another possible application is shown in FIG. 6 and relates to manual transmissions with at least one hydraulically actuated and hydraulically cooled clutch KE, which is regulated by a transmission control.

It is possible to use the method according to the invention for the functions “venting” and “filling oil tank”. One possibility of use is in driving situations in which the actuation pressure of the E-Clutch is less than the cooling oil pressure, e.g. Immediately after starting the engine as long as the clutch is supplied with cooling oil but not yet activated.

Claims

Expectations

1. Hydraulic system (1) with at least one hydraulic actuator (A1, A2) for actuating at least one coupling element (K1, K2, KP, KE), the at least one actuator (A1, A2) via a pump arrangement (10, 20 ) is connected to an oil tank (3) arranged separately from the oil sump (2),

and the coupling element (K1, K2, KP, KE) being cooled from the oil sump (2) via a separate pump duct (30),

wherein the pump path (14, 24) to the at least one actuator (A1, A2) is connected with a check valve (40, 41) to the pump path (34) of the cooling.

2. Hydraulic system (1) with two hydraulic actuators (A1, A2) for the actuation of clutches (K1, K2) in a double clutch transmission, the actuators (A1, A2) via respective pump assemblies (10, 20) with one of the oil sump ( 2) separated oil tank (3) are connected,

and wherein the clutches (K1, K2) are cooled from the oil sump (2) via a separate pump arrangement (30),

the pump paths (14, 24) to the actuators (A1, A2) being connected to the pump path (34) of the cooling system, each with a check valve (40, 41).

3. A method for operating a hydraulic system (1) according to claim 1 or 2, characterized in that, in normal operation, the at least one pump path (14, 24) of the at least one actuator (A1, A2) is subjected to a higher pressure than the pump path ( 34) the cooling and the at least one Rückschlagven valve (40, 41) remains closed.

4. The method for operating a hydraulic system (1) according to claim 1, characterized in that the hydraulic system (1) is vented by activating the pump assembly (30) for cooling and the two further pump paths (14, 24) of the actuators (A1, A2) or the one pump path (14) with displaced air from the Clutch (K1, K2) or the coupling elements (KP, KE) are acted upon, the check valves (40, 41) or the one check valve (41) being open.

5. The method for operating a hydraulic system (1) according to claim 1 or 2, characterized in that the pump arrangements (10, 20) of the actuators (A1, A2) or the one pump arrangement (10) slowly run backwards and air through at least one suction filter ( 12, 22) into the oil tank (3).

6. The method for operating a hydraulic system (1) according to claim 1, characterized in that a control for filling is used, a pump path (14, 24) to an actuator (A1, A2) and the pump path (34) to the cooling treatment is activated and the passive pump path (14, 24) is supplied with oil via the associated open check valve (40, 41), which is fed into the oil tank (3).