Device Reducing Drag Loss in an Automatic Transmission

Abstract

A drag torque reduction device for an automatic transmission includes a hydraulic controller with a diversion for excess cooling oil into an oil sump that is positioned upstream of a radiator relative to a flow of fluid to the radiator. The diversion includes a temperature-dependent, switchable aperture and a switching valve. The temperature-dependent, switchable aperture is configured to close above a temperature threshold. The switching valve is configured to close above a threshold pressure.

Claims

1-4. (canceled)

5. A drag torque reduction device for an automatic transmission, comprising: a plurality of multi-disk shift elements; a hydrodynamic torque converter: a converter clutch; and a hydraulic controller with a radiator, the hydraulic controller operable to control the plurality of multi-disk shift elements, the hydrodynamic torque converter and the converter clutch, the hydraulic controller having a diversion for excess cooling oil into an oil sump, the diversion positioned upstream of the radiator relative to a flow of fluid to the radiator, the diversion comprising a temperature-dependent, switchable aperture and a switching valve, the temperature-dependent, switchable aperture configured to close above a temperature threshold, the switching valve configured to close above a threshold pressure, the diversion configured such that the temperature-dependent, switchable aperture and the switching valve are arranged in a sequence of the temperature-dependent, switchable aperture then the switching valve in series.

6. The drag torque reduction device of claim 5, wherein the hydraulic controller further comprises a constant aperture that is positioned downstream of the switching valve relative to a flow of fluid to the oil sump, the constant aperture configured to adjust a pressure gradient depending upon a volume flow through the constant aperture such that the switching valve is closed when a compressive force acting on a valve slide of the switching valve is greater than a spring force acting on the valve slide of the switching valve, the compressive force arising through a backflow at the constant aperture.

7. A drag torque reduction device for an automatic transmission, comprising: a plurality of multi-disk shift elements; a hydrodynamic torque converter; a converter clutch; and a hydraulic controller with a radiator, a hydraulic controller with a radiator, the hydraulic controller operable to control the plurality of multi-disk shift elements, the hydrodynamic torque converter and the converter clutch, the hydraulic controller having a diversion for excess cooling oil into an oil sump, the diversion positioned upstream of the radiator relative to a flow of fluid to the radiator, the diversion comprising a temperature-dependent, switchable aperture and a switching valve, the temperature-dependent, switchable aperture configured to close above a temperature threshold, the switching valve configured to close above a threshold pressure, the diversion configured such that the temperature-dependent, switchable aperture and the switching valve are arranged in a sequence of the switching valve then the temperature-dependent, switchable aperture in series.

8. The drag torque reduction device of claim 7, wherein a pressure gradient depending on the volume flow and the temperature is adjustable at an end of the switching valve at the temperature-dependent, switchable aperture such that the switching valve is closed when a compressive force acting on a valve slide of the switching valve is greater than a spring force acting on the valve slide of the switching valve, the compressive force arising through a backflow at the temperature-dependent, switchable aperture.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In the following, the invention is more specifically illustrated as an example on the basis of the attached figures. The following is shown:

[0012] FIG. 1: A system pressure/oil temperature diagram to illustrate the areas of minimum lubrication and cooling;

[0013] FIG. 2: A schematic presentation of a first exemplary embodiment of the invention; and

[0014] FIG. 3: A schematic presentation of a second exemplary embodiment of invention.

DETAILED DESCRIPTION

[0015] Reference will now be made to embodiments of the invention, one or more examples of which are shown in the drawings. Each embodiment is provided by way of explanation of the invention, and not as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be combined with another embodiment to yield still another embodiment. It is intended that the present invention include these and other modifications and variations to the embodiments described herein.

[0016] Hydraulic controllers for automatic transmissions comprising a hydrodynamic converter and a converter clutch are well-known to the specialist, such that, within the framework of the following description of figures, only the components relevant to the invention are described and explained.

[0017] FIGS. 2 and 3 show a hydraulic controller for an automatic transmission comprising a hydrodynamic converter 6 and a converter clutch 7. The exemplary embodiments shown differ with respect to the varying arrangements and designs of the device in accordance with aspects of the invention. In FIGS. 2 and 3, a converter clutch valve is designated with WK-V, a converter pressure valve is designated with WD-V, a converter switching valve is designated with SV-WD, a converter base point valve is designated with WK-FP-V and a converter retaining valve is designated with WRH-V. Furthermore, a radiator is shown with 1 and a radiator bypass is shown with 5; it is ensured through these that the oil is not directed through the radiator 1 at low temperatures. Thereby, the converter ring inlet pressure is designated with p_zT, the converter ring outlet pressure is designated with p_vT and the converter clutch pressure is designated with p_WK.

[0018] According to a first exemplary embodiment of the invention and with reference to FIG. 2, a device for reducing the drag torque in an automatic transmission comprising a hydrodynamic converter 6 and a converter clutch 7 is proposed, with which, in the hydraulic controller of the transmission in front of the radiator 1 in the direction of flow to the radiator 1, a diversion of the excess quantity of cooling oil into an oil sump 8 is provided, by a temperature-dependent, switchable aperture that closes above a predetermined temperature threshold Θ_SP and a switching valve 2 that closes above a predetermined pressure threshold p_Sys_SP, which are switched in the sequence of “aperture 3—switching valve 2” in a series.

[0019] At temperatures that fall below this predetermined temperature threshold Θ_SP, the temperature-dependent, switchable aperture 3 is open. Furthermore, at low pressures that fall below the predetermined pressure p_Sys_SP, the switching valve 2 is opened, and is closed above p_Sys_SP, such that, with an open switching valve 2, the deviated oil flows into the oil sump 8.

[0020] The switching valve 2 is opened through the amount of pressure in the inlet at the switching valve 2 coming from the temperature-dependent, switchable aperture 3, that is, if the compressive force acting on the valve slide of the switching valve 2 that arises through such inlet pressure is less than a spring force acting counter to the closing direction of the switching valve 2, which also acts on the valve slide of the switching valve 2.

[0021] At the end of the switching valve 2 at the oil sump 8, a constant aperture 4 is provided, at which a pressure gradient depending on the volume flow is adjusted. The switching valve 2 is closed, if the compressive force acting on the valve slide of the switching valve 2 that arises through the backflow at the constant aperture 4 is greater than the spring force counter to the closing direction of the switching valve 2 that is also acting on the valve slide of the switching valve 2. The switching valve 2 is now held in the closed state by the pressure prevailing in the inlet of the switching valve 2. If the temperature-dependent, switchable aperture 3 now closes, the switching valve 2 has no function, such that the spring force of the valve slide of the switching valve 2 acting counter to the closing direction of the switching valve 2 moves into its “switching valve open” resting position.

[0022] As a result, a minimum lubrication and cooling is achieved at temperatures up to a maximum of Θ_SP or pressures up to a maximum of p_Sys_SP. At temperatures that exceed Θ_SP and pressures that exceed p_Sys_SP, no diversion of oil is achieved; the volume flow to the radiator 1 corresponds to the normal level corresponding to the current system pressure. The temperature-dependent, switchable aperture 3 may be designed, for example, as a bimetal aperture.

[0023] Through the concept in accordance with exemplary aspects of the invention, a minimum lubrication and cooling at low temperatures and low system pressures is ensured, since, at low temperatures that fall below a predetermined temperature threshold Θ_SP, the temperature-dependent, switchable aperture 3 remains open and, at low pressures that fall below a predetermined pressure p_Sys_SP, the switching valve 2 remains open. This is illustrated with reference to FIG. 1.

[0024] It is thereby clear that, at temperatures up to a maximum of Θ_SP and pressures up to a maximum of p_Sys_SP, the minimum lubrication and cooling is provided through the constant aperture 4. At temperatures that exceed Θ_SP, the volume flow increases. Furthermore, at a system pressure that exceeds p_Sys_SP, the oil flow increases, in order to not cause any damages to the transmission components at high transmission loads and low oil temperatures, and in order to ensure a sufficient oil supply of the shift elements for shifting. Preferably, the temperature-dependent, switchable aperture 3 and the switching valve 2 are designed in such a manner that, with a closed temperature-dependent, switchable aperture 3 or with a closed control valve 2, the volume flow to the radiator 1 corresponds to the normal level corresponding to the current system pressure.

[0025] As an alternative to the sequence of “aperture 3—switching valve 2”, the aperture 3 and the switching valve 2 may be arranged in the sequence of “switching valve 2—aperture 3,” as illustrated by FIG. 3. With this arrangement, the temperature-dependent, switchable aperture 3 simultaneously takes over the function of the constant aperture 4 provided in FIG. 2.

[0026] The switching valve 2 is opened through the amount of the inlet pressure of the switching valve 2, that is, if the compressive force acting on the valve slide of the switching valve 2 that arises through such inlet pressure is less than the spring force acting counter to the closing direction of the switching valve 2, which also acts on the valve slide of the switching valve 2.

[0027] The temperature-dependent, switchable aperture 3 is now arranged at the end of the switching valve 2 at the oil sump 8. At the aperture 3, a pressure gradient is adjusted, which depends on both the volume flow and the temperature. The switching valve 2 is closed, if the compressive force acting on the valve slide of the switching valve 2 that arises through the backflow at the constant aperture 4 is greater than the spring force acting counter to the closing direction of the switching valve 2. The switching valve 2 is held in the closed state by the pressure prevailing in the inlet of the switching valve 2. If the temperature-dependent, switchable aperture 3 now closes, the valve slide of the switching valve 2 moves into its “switching valve closed” final position.

[0028] As a result, a minimum lubrication and cooling is also achieved here at temperatures up to a maximum of Θ_SP or pressures up to a maximum of p_Sys_SP. At temperatures that exceed Θ_SP and pressures that exceed p_Sys_SP, no diversion of oil is achieved; the volume flow to the radiator 1 corresponds to the normal level corresponding to the current system pressure. Here as well, the temperature-dependent, switchable aperture 3 may be designed, for example, as a bimetal aperture.

[0029] Modifications and variations can be made to the embodiments illustrated or described herein without departing from the scope and spirit of the invention as set forth in the appended claims.

REFERENCE SIGNS

[0030] 1 Radiator [0031] 2 Switching valve [0032] 3 Temperature-dependent, switchable aperture [0033] 4 Constant aperture [0034] 5 Radiator bypass [0035] 6 Converter [0036] 7 Converter clutch [0037] 8 Oil sump [0038] p_Sys System pressure [0039] p_Sys_SP Pressure threshold [0040] p_vT Converter ring outlet pressure [0041] p_zT Converter ring inlet pressure [0042] θ_Öl Oil temperature [0043] θ_SP Temperature threshold [0044] SV-WD Converter switching valve [0045] WD-V Converter pressure valve [0046] WRH-V Converter retaining valve [0047] WK-FP-V Converter base point valve [0048] WK-V Converter clutch valve