Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
  • F16H61/66—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings
  • F16H61/662—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings with endless flexible members
  • F16H61/66272—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing specially adapted for continuously variable gearings with endless flexible members characterised by means for controlling the torque transmitting capability of the gearing
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B3/00—Intensifiers or fluid-pressure converters, e.g. pressure exchangers; Conveying pressure from one fluid system to another, without contact between the fluids

Definitions

• the invention relates to an automatic transmission for a motor vehicle, in particular a CVT transmission, with a varia ⁇ gate, which has a primary disc set and a secondary disc set with a thrust link belt, the variator being adjustable with a transmission oil provided by an oil pump via an electro-hydraulically controlled pressure supply device.
• hydraulically actuated adjusting devices of the variator are acted upon by an oil pump with the necessary adjusting pressure for setting a gear ratio of the automatic transmission that is matched to the respective operating state of the internal combustion engine or the driving speeds of the motor vehicle.
• the adjustment pressure is set by the amount of transmission oil delivered by the oil pump to the pressure supply device.
• the present invention is therefore based on the object of creating an automatic transmission which, with the smallest possible pump dimensions, has a sufficiently high adjustment dynamic so that a gear ratio which is respectively adapted and required to the driving state is available.
• the inventive design of the automatic transmission or the pressure supply with a pressure adjusting device which according to the invention is equipped with a switching valve and a stepped piston, achieves the advantage of increasing the adjustment dynamics.
• a pressure increase is achieved in the pressure setting device according to the invention, which corresponds to a fictitiously introduced amount of transmission oil, which advantageously does not have to be applied by the oil pump.
• the fictitious amount of gear oil results from the product of the amount of gear oil actually delivered and the value of the diameter ratio between the first
• the present invention thus advantageously ensures that a greater change in the gear ratio can be set in a certain time interval than in the automatic transmissions known from the prior art.
• the required amount of transmission oil can also be achieved with an oil pump that is smaller, less expensive and takes up less space.
• FIG. 3 shows the course of the transmission ratio of an automatic transmission and the corresponding adjustment path of the disk set of the secondary shaft over time as a function of the change in driving state according to FIG. 1 and
• FIG. 1 shows a schematic representation of a pressure setting device 1 in a pressure supply (not shown) of an automatic transmission
• Oil is transferred from the oil pump 3 via the pressure setting device 1 to a secondary disk set 10, which is only symbolically indicated in FIG. 1, and after an upstream one
• Control unit 11 is conveyed to a primary disc set 12, likewise only indicated, of a variator of the automatic transmission, the disc sets 10, 12 being affected by the oil pressure a primary shaft or secondary shaft, not shown, can be axially displaced to set a specific transmission ratio.
• the switching valve 2 can be switched into a blocking position by a solenoid valve 17, so that the pressure line 4 for the oil supply from the oil pump 3 to the variator is interrupted.
• the bypass line 5 branches off from the pressure line 4 in an area between the oil pump 3 and the switching valve 2 and opens into the second cylinder space 16 of the stepped piston 9.
• the stepped piston 9 is designed as a rotationally symmetrical body which has a first section 18 and a second section 19 stepped therefrom, the diameter of the first section 18 being the diameter of the first end face 13 and the diameter of the second section 19 being the diameter corresponds to the second end face 15.
• the stepped piston 9 can be displaced in the axial direction over a maximum adjustment path between the path limiting device 7, which represents a cylinder bottom of the first cylinder chamber 14, and a shoulder 8 serving as a path limiting device, a connection being provided in the area between the first cylinder chamber 14 and the second cylinder chamber 16 an end position of the stepped piston 9 on the cylinder bottom 7 of the first cylinder chamber 14 is opened and is closed in a position of the stepped piston 9 which deviates therefrom.
• the stepped piston 9 has a channel 21 which starts from its first end face 13 and is arranged coaxially to its central axis 20 and extends into the second section 19 of the stepped piston 9 with a smaller diameter.
• the channel 21 is connected to four boreholes 22, which extend radially outward into the peripheral region of the stepped piston 9.
• annular groove is formed in the cylinder housing 6 to form the connection between the cylinder chambers 14, 16
• Connection 23 is provided with a connecting line 24 opening into the bypass line 5.
• bypass line 5 In the bypass line 5 is in the area between its branch from the pressure line 4 and the junction Connection line 24 arranged a pump-effective aperture 25 as a throttle device.
• the mode of operation of the pressure setting device 1 is illustrated by means of a driving course shown by way of example in FIGS. 2 to 4.
• FIG. 2 shows the course of a driving speed v_F of the motor vehicle and the corresponding speed n_M of an internal combustion engine during a braking operation over time t.
• the engine speed n_M has a constant value up to a point in time t_WK.
• t_WK i.e. H. from a fixed vehicle speed
• a converter lock-up clutch of known design is opened to prevent the engine from being "stalled" when the speed is reduced further.
• the engine speed n_M then falls within a short time interval, which at Time t_L has ended, down to the idling speed.
• FIG. 1 the course of a gear ratio i of the automatic transmission and a corresponding adjustment path x of the disk set of the secondary shaft as a function of the course of the driving speed is shown in FIG. 1 over time t.
• the translation i should be set as the optimal translation i_opt according to a control characteristic for the respective operating point, which is optimized with regard to driver behavior and / or consumption.
• a minimally adjustable translation i_min with a so-called ter “Overdrive”, ie the transmission output speed is greater than the transmission input speed.
• the ratio 1 is adjusted by a controller according to an optimal size stored in a map of the transmission control m as a function of several parameters such as driving speed v_F, engine speed n_M and throttle valve position .
• the present example is based on a partial load operation as the operating situation of the internal combustion engine and the automatic transmission, in which the internal combustion engine is operated in a low-speed range that is optimal for consumption and in which the largest driving stage is present, i. H. that the automatic transmission has a minimal translation ⁇ _Mm.
• An adjustment path of the secondary disc set of x corresponds to this minimum translation ⁇ _Mm.
• the transmission ratio I steadily increases up to a maximum transmission ratio ⁇ _max at the time t_3
• the adjustment path x likewise increases up to the maximum adjustment path x_max.
• FIG. 4 shows the course of the required as well as the actual amount of oil required by the oil pump 3, which is required for the adjustment path x of the secondary disk set according to FIG. 3.
• the actual demand quantity V_real has a constant value in the range from t_0 to time t_WK.
• the actual transmission oil requirement quantity V_real abruptly drops to a smaller value.
• This course of the required quantity of gear oil results from the fact that the oil pump 3 is driven by the internal combustion engine w r ⁇ , the speed of the oil pump 3 being the speed of the engine Internal combustion engine corresponds. From the decrease in engine speed n_M at the time the converter lock-up clutch t_WK opens, the drop in the actual amount of transmission oil V_real follows.
• the transmission control recognizes the case described above, e.g. B. by the ratio change exceeding a predefined limit value, then the pressure line 4 of the pressure setting device 1 by means of the switching valve 2 blocked.
• the oil pump 5 then conveys the transmission oil via the bypass line 10 with the orifice 25 into the second cylinder space 16. Due to the quantity of transmission oil supplied, the pressure in the second cylinder space 16 rises such that the stepped piston 9 is axially displaced in the direction of the first end face 13.
• the displacement of the stepped piston 9 in turn has the consequence that the volume of the first cylinder space 14 is reduced in proportion to the adjustment path of the stepped piston 9.
• first end face 13 of the stepped piston 9 is dimensioned larger than the second end face 15, a larger amount of oil is pushed out of the first cylinder chamber 14 with the same adjustment path than is conveyed into the second, smaller cylinder chamber 16 by the oil pump 3.
• connection prevents the oil pressure from rising to a critical range, as a result of which the
• Stepped piston 9 is protected from damage and an additional pressure relief valve is unnecessary.
• the oil pump 3 delivers the transmission oil again via the pressure line 4 into the first cylinder chamber 14 and to the variator. Due to the diameter ratio between the first end face 13 and the second end face 15, the stepped piston 9 is displaced towards the shoulder 8 in the direction of the second end face 15.
• the unidirectional aperture 25 prevents the displacement from exceeding a permissible displacement speed and the adjustment dynamics from the maximum transmission ratio i_max being reduced.
• the volume of the first cylinder chamber 14 is dimensioned such that the oil volume is sufficient for adjustment and the first cylinder chamber 14 serves as an absorber in the end position of the stepped piston 9 on the shoulder 8.
• Control unit 12 consumers, primary disc set

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Control Of Transmission Device (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=7852620

Family Applications (1)

Country Status (5)

Families Citing this family (5)

Family Cites Families (5)

• 1997
  • 1997-12-19 DE DE19756685A patent/DE19756685C2/de not_active Expired - Fee Related
• 1998
  • 1998-12-15 EP EP98965268A patent/EP1040287A1/de not_active Withdrawn
  • 1998-12-15 KR KR1020007006760A patent/KR20010024770A/ko not_active Application Discontinuation
  • 1998-12-15 JP JP2000525698A patent/JP2003517540A/ja not_active Withdrawn
  • 1998-12-15 WO PCT/EP1998/008220 patent/WO1999032806A1/de not_active Application Discontinuation

Non-Patent Citations (1)

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