This application claims priority from German patent application serial no. 10 2010 039 350.9 filed Aug. 16, 2010.
The invention relates to a method for operating a hydraulic apparatus of a transmission device.
A hydraulic system of a transmission for a vehicle having a variable displacement pump designed with a variable output is known from DE 10 2004 008 611 A1; a pilot pressure can be applied to the adjustment device of the pump in order to vary the output, and the pump can generate a changeable flow of hydraulic fluid for the appropriate supply of different consumers of the transmission. Furthermore, the hydraulic system is designed with at least two pressure circuits arranged on the discharge side of the variable displacement pump that are prioritized differently regarding the supply of hydraulic fluid by the pump. Hydraulic fluid is applied directly by the variable displacement pump to a primary pressure circuit with higher priority. In order to limit the pressure of the primary pressure circuit, a pressure control valve that is able to connect the secondary pressure circuit is provided between the discharge side of the variable displacement pump and a lower-priority secondary pressure circuit. In order to control the output of the variable displacement pump as a function of the operating status, a pressure return is configured between the discharge side of the variable displacement pump and the adjusting device of the variable displacement pump.
If a change in the operating status in the transmission device is required because a greater volume of hydraulic fluid is needed in the transmission device than is currently being provided by the variable displacement pump in the area of the primary pressure circuit and/or the secondary pressure circuit, the pressure decreases in the primary pressure circuit and/or the secondary pressure circuit, and the variable displacement pump is adjusted to provide greater output by the overall force component impinging on the region of the adjusting device.
Disadvantageously, however, the adjustment of the output of the variable displacement pump does not occur until during the change of the operating condition; therefore, the transmission device cannot be operated with the desired spontaneity.
The object of the present invention is therefore to provide a method for operating a hydraulic device of the transmission by means of which a transmission device may be actuated with the desired degree of spontaneity.
During the method according to the invention for operating a hydraulic device of a transmission having a variable displacement pump that can be supplied with a hydraulic pressure to vary the output in the area of an adjusting device, and having at least two pressure circuits that may be connected to the discharge side of the variable adjustment pump and that are assigned different priorities regarding the supply of hydraulic fluid by the pump, with a pressure control valve being provided between a higher-priority pressure circuit and a lower-priority pressure circuit that is able to connect the lower-priority pressure circuit for the purpose of limiting the pressure of the higher-priority pressure circuit, with a pressure return being provided downstream of the discharge side of the variable displacement pump in the direction of the adjustment device of the variable displacement pump in order to adjust the output of the variable displacement pump as a function of the operating status, if a change in the operating status of the transmission is needed that requires increasing the output of the variable displacement pump relative to the current output, the pressure applied in the region of the adjusting device by the pressure return is correspondingly modified before the change to the operating status.
When the operating state needs to change in the transmission device, the output of the variable displacement pump is increased to a specific level using the method according to the invention before changing to the operating state characterized by a need for a greater volume of hydraulic fluid, whereby the transmission device is supplied during the entire change of the operating state with the volume of hydraulic fluid necessary to change the operating state without delay, and the transmission device can be operated with the desired high level of spontaneity.
The features indicated in the claims as well as the features indicated in the following exemplary embodiments of the subject matter of the invention are suitable for developing the subject matter of the invention by themselves or in any combination with each other. The combination of a given set of features does not represent a restriction on the development of the subject matter of the invention and is only essentially representative in nature.
Additional advantages and advantageous embodiments of the subject matter of the invention can be found in the claims and subsequent exemplary embodiments, the principle of which is described with reference to the drawing; for the sake of clarity, the same reference characters are used for components with the same design and function in the description of the different embodiments.
They show:
In order to adjust the output of the variable displacement pump 2 as needed, a pressure return 5 is provided downstream of the discharge side of the variable displacement pump 2 that branches toward the adjusting device 3 of the variable displacement pump 2 in the area of the pressure control valve 4. Furthermore, a valve 6 is provided downstream of the pressure control valve 4, in the region of which a flow q_KS of a third pressure circuit TK, or cooling and lubricating fluid circuit may be adjusted.
The variable displacement pump 2 is designed in the present case as a vane pump whose adjusting ring 7 can be supplied in the region of an effective area 26 with the pressure p_B that is applied via the pressure return 5 and resisted by a spring device 8 acting on another effective area 26. Depending on the current application, the variable displacement pump 2 can also have another suitable pump design with an adjustable displacement volume.
The spring force of the spring device 8 is applied to the adjusting ring 7 of the variable displacement pump 2 such that the variable displacement pump 2 is pivoted toward high outputs when the hydraulic pressure p_B of the pressure return 5 is low, with the variable displacement pump 2 or its output being increasingly reduced against the spring force of the spring device 8 when the values of the hydraulic pressure p_B are high.
Upstream of the variable displacement pump 2, a line L1 branches from the pressure return 5 toward a valve device 9 of the adjusting device 3, the pressure return 5 being connected, via the line L1, to a low-pressure area 12 via a first aperture 10 or a second aperture 11 depending on a switch position of the valve device 9, the low-pressure area being upstream of the fluid pan for the transmission device. The valve device 9 designed as a switching valve 9 in the embodiment of the hydraulic device 1 according to
If the valve device 9 or its valve spool 27 is moved proceeding by the pilot pressure p_VS15 of the pressure adjuster 15 from its first switching position into its shifted second switching position against the spring device 14, the line L1 is connected, via the second aperture 11, to the low-pressure area 12. The aperture diameter of the first aperture 10 is greater in the present case than the aperture diameter of the second aperture 11, whereby a larger leakage flow flows out of the pressure return 5 through line L1 toward the low-pressure area 12 when the first aperture 10 is open than is the case when the second aperture 11 is opened on the valve device side.
In order to operate a transmission device designed with the hydraulic device 1 according to
During a dynamic change of the operating state during which a high flow volume of hydraulic fluid is provided via the hydraulic device 1 or its variable displacement pump 2 within a short time, the valve device 9 is moved into the switching position shown in
With a relatively simple design, a dynamic adjustment of the flow of the variable displacement pump 2 is thus achieved as a function of the operating state, and a minimum output of the variable displacement pump 2 is achieved during static operation that only marginally restricts the efficiency of a transmission device, and the transmission device can be operated with an overall high degree of efficiency.
The hydraulic device 1 fundamentally maximizes potential economy since only a very small leakage flow arises the area of the pressure return 5 when a transmission device is in static mode, i.e., in particular when the output shaft is at a constant rotational speed, when the main pressure p_PK in the primary pressure circuit PK is substantially constant, when the transmission device is in a mode where it is not shifted, or during an operating state of the vehicle drivetrain in which basically no actions occur in the transmission device that generate a strong need for a high volume of hydraulic fluid. Consequently, when the necessary primary and secondary pressure levels are reached, the variable displacement pump 2 switches to the position in which the output flow is reduced.
The pump input power is optimally reduced by minimizing the demand in the area of the secondary pressure circuit SK of the hydraulic device 1 in addition to the demand for leakage fluid originating from the pressure return 5 toward the low-pressure area 12. This is the case, for example, when the amount of cooling and lubricating fluid required in the third pressure circuit TK is minimal at low transmission loads.
In order to limit the hydraulic pressure p_B applied to the adjusting device 3 via the pressure return 5 to a maximum above which the functioning of the variable displacement pump 2 would be irreversibly damaged under certain circumstances, a pressure control valve 16 is provided upstream from the variable displacement pump 2 or the adjusting ring 7, the pressure limiting valve being designed in the present case as a check valve and opening upon a preset pressure threshold, with the pressure return 5 being connected to the low-pressure area 12 in a unrestricted fashion in this region when the pressure-control valve 16 is open.
Both the pressure control valve 4 and the valve 6 designed as a combination of a pressure control valve and pressure-reducing valve can be fed a pilot pressure p_VS15 in the manner shown in
In addition to switching the valve device 9, the output of the variable displacement pump 2 can also be varied in the hydraulic system 1 according to
The pilot pressure p_VS15 or p_VS17 is elevated at a time at which the increased hydraulic fluid flow demand does not yet exist in the transmission device, although such demand is highly probable given the need for changing the operating state.
Alternately or additionally, in other versions of the above-described procedure for increasing the output of the variable displacement pump 2 in the exemplary embodiments of the hydraulic device 1 shown in the drawing depending on its present use, a hydraulic fluid consumer is activated in one of the pressure circuits PK, SK, and/or TK and/or a leakage fluid flow is activated in one of the pressure circuits, or simultaneously in a plurality of pressure circuits PK, SK and/or TK, preferably by supplying a consumer, such as a pressure adjuster with leakage, with hydraulic fluid, by elevating a flow of cooling fluid of a startup clutch or a double clutch system or the like, which reduces the flow of hydraulic fluid in the pressure return 5 as well as the pressure p_B.
Once the change of the operating state is instigated in the transmission device, the previous need for a greater volume of hydraulic fluid is reduced, for example, by deactivating the consumer that was additionally activated beforehand and/or by reducing the previously increased leakage flow, whereby the elevated delivery rate in the region of the variable displacement pump 2 is fully available for immediately implementing the change in operating state characterized by a need for a greater volume of hydraulic fluid, such as a gear shift during which a hydraulically actuatable shift element within a flow of force in the transmission device is connected by being fed pressure coming from the primary pressure circuit PK.
A second embodiment corresponding to
The hydraulic device 1 according to
In the third embodiment of the hydraulic device 1 shown in
The valve device 9 designed with seven control edges 91 to 97 is coupled to the intake side 23 of the variable displacement pump 2 in the region of the fourth control edge 94, and to the discharge side 24 of the variable displacement pump 2 in the region of the control edges 92 and 96. The effective surface 25 of the adjusting ring 7 of the variable displacement pump 2 against which the spring device 8 also impinges can be supplied with pressure via the fifth control edge 95 of the valve device 9, whereas in the area of the other effective surface 26 of the adjusting ring 7 a pressure counteracting the spring device 8 can be applied to the adjusting ring 7 of the variable displacement pump 2 via the third control edge 93 of the valve device 9.
Depending on the overall force component that is applied to the valve spool 27 of the valve device 9 and is adjusted depending on the actuating pressure p_B applied to the first effective surface 19, the throttled pressure p_B21 applied to the second effective surface 22, and the spring force of the spring device 20, the third control edge 93 is either connected to the second control edge 92 or the fourth control edge 94, and the fifth control edge 95 is connected to the sixth control edge 96 or fourth control edge 94. This means that, depending on the position of the valve spool 27, the effective surface 25 of the adjusting ring 7 is either supplied with the pressure from the intake side 23 or the pressure from the discharge side 24 of the variable displacement pump 2, whereas the pressure from the discharge side 24 or pressure from the intake side 23 is applied to the effective surface 26 of the adjusting ring 7.
In contrast to the two embodiments of the hydraulic device 1 shown in
In the third embodiment of the hydraulic device 1 shown in
The pressure p_SK of the secondary pressure circuit SK is thus lowered in the above-described manner when there is a need to change the operating state in the transmission device for which an increase is anticipated in the volume of hydraulic fluid required from the amount currently provided by the variable displacement pump 2, by correspondingly actuating an additional valve unit 29 downstream of the additional pressure control valve 28 originating from a pressure adjuster 30 assigned to the valve unit 29 with pilot pressure p_VS30, and by means of the associated increase in the lubrication and coolant flow q_KS in the third pressure circuit TK, whereby the variable displacement pump 2 is adjusted toward higher displacement volumes due to the reduced pressure p_B in the pressure return 5 and corresponding actuation of the valve device 9.
The hydraulic device 1 according to
In the exemplary embodiment of the hydraulic device 1 shown in
In comparison to the hydraulic device 1 according to
In the embodiments of the hydraulic device 1 according to
The pressure p_B applied via the pressure return 5 in the hydraulic devices 1 according to
When a change to the operating state in the transmission device is needed that can only be accomplished to the desired degree with a hydraulic fluid requirement that is elevated in comparison to the hydraulic fluid flow for the current output of the variable displacement pump, the pressure p_B applied to the adjusting ring 7 via the pressure return 5 is suitably reduced before the operating state changes in the manner described in
Number | Date | Country | Kind |
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10 2010 039 350.9 | Aug 2010 | DE | national |