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
  • F16H47/00—Combinations of mechanical gearing with fluid clutches or fluid gearing
  • F16H47/02—Combinations of mechanical gearing with fluid clutches or fluid gearing the fluid gearing being of the volumetric type
• • 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
  • F16H47/00—Combinations of mechanical gearing with fluid clutches or fluid gearing
  • F16H47/02—Combinations of mechanical gearing with fluid clutches or fluid gearing the fluid gearing being of the volumetric type
  • F16H47/04—Combinations of mechanical gearing with fluid clutches or fluid gearing the fluid gearing being of the volumetric type the mechanical gearing being of the type with members having orbital motion
• • 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
  • F16H61/38—Control of exclusively fluid gearing
  • F16H61/40—Control of exclusively fluid gearing hydrostatic
  • F16H61/4043—Control of a bypass valve

Definitions

• the invention relates to a device for a hydrostatic drive operated in a closed circuit with a hydraulic pump, a hydraulic motor and a downstream powershift transmission.
• a hydrostatic four-wheel drive is known from DE-OS 25 35 762, which has a device for harmonizing the torque balance. With such drives there is first the difficulty that the energy of the system is wasted when a wheel slips, and the other wheel motors can then no longer develop torque. A harmonization of the torque balance was achieved in the known drive, inter alia, by flow limiting devices. However, this solution cannot be applied to a transmission control device because the pressure conditions change too quickly, caused by the corresponding transmission shift processes. From DE-OS 27 10 055 a hydraulic gear change transmission with automatic oil pressure control is known. In this transmission, a closed circuit is also used as a pressure source for other devices, e.g. B. a power steering, a brake booster, etc. used.
• an oil pressure regulating device which works hydraulically. This known device is able to maintain a constant oil pressure for the other devices. Pump and hydraulic motor cannot be kept completely free of pressure changes by this device.
• a drive for land vehicles is known from DE-OS 28 55 573.
• a vehicle is equipped with two hydraulic pumps and several hydraulic motors. When cornering on the hydraulic motors assigned to different sides of the vehicle, liquid quantities and pressures of different sizes are generated, which are completely compensated by a compensating line.
• An electromagnetically operated shut-off valve that is switched into the compensating line can be operated from the driver's cab of the vehicle. With this drive, manual control is required to compensate for pressure surges. It follows from this that this known device cannot be used in conjunction with a transmission, which often switches automatically, because the operator could not react quickly enough.
• the present invention has for its object to provide a device for a hydrostatic drive operated in a closed circuit with a hydraulic pump and a downstream powershift transmission, the shift quality should be improved and switching work should be reduced.
• the object is achieved by the features listed in the characterizing part of claim 1.
• the invention has the advantages over the known that pressure surges in the hydrostatic system are automatically avoided reliably and reliably. Because the device for compensating pressure surges is actuated synchronously with the upshifting or downshifting of the transmission, pressure pads are avoided, the shifting quality is improved and the shifting work is reduced.
• FIG. 1 schematically shows the device according to the invention in connection with a powershift transmission
• FIG. 2 shows a circuit of a hydraulic bypass valve unit belonging to the device according to FIG. 1,
• Fig. 3 shows another embodiment of a bypass valve unit with electrical control and deceleration.
• a transmission 1 (FIG. 1), preferably a powershift transmission, is preceded by a hydrostat consisting of a hydraulic pump 2 adjustable in the exemplary embodiment and a hydraulic motor 3. This is from a drive motor 4, z. B. an internal combustion engine. Hydraulic lines 10, 11 establish the connection between the hydraulic pump 2 and the hydraulic motor 3.
• a device known per se for forward and reverse travel can be provided, e.g. B. a directional valve. This can be controlled from the control device.
• a further pump 30 is driven, which offers pressure medium conveyed from a container 39 as a control medium via a line 31.
• the hydraulic pump 2 is assigned a controller 32 which receives pressure medium from a control pump 40 via a control line 34 and is influenced by an electronic control device 5 via an electrical line 33.
• a travel switch 7 operates on the electronic control device 5.
• the electronic control device 5 also actuates solenoid valves (not shown in the drawing) in a control valve unit 6 which belongs to the transmission 1.
• the electrical connections between the electronic control device 5 and the control valve unit 6 are made via electrical lines 19, 20, 21.
• Corresponding signals from the movement of wheels 29 of the vehicle are passed to the electronic control device 5 via a speed sensor 22 via a line 23. In this way, a downshift lock known per se can be controlled.
• the electronic control device 5 draws its current from supply lines 8, 9.
• a bypass valve unit 12 is located via lines 14, 15 (FIG. 1). This is controlled by the electronic control device 5 via a line 16 and is connected to ground via a further line 17.
• the bypass valve unit 12 is able to connect the two pressure medium-carrying lines 10, 11, if necessary, via a control line 18 it is possible to activate a timing element in the bypass valve unit 12, the timing element can again via a return line 28 leading to the container 39 be returned to the initial state.
• bypass valve unit 12 Each time the transmission 1 is actuated, the bypass valve unit 12 is to set up an auxiliary branch, that is to say to connect the two lines 10, 11 carrying pressure medium to one another. This happens by a bypass valve 13 (Fig. 2) upstream directional valve 27 which is actuated via the electrical lines 16, 17 and is switched from the rest position shown in the drawing to its other position. As a result, pressure medium passes via the control line 18 without delay via a check valve 24, which opens here, to the control input of the bypass valve 13. Via lines 14, 15, the two lines 10 and 11 are connected to one another. A branch lying parallel to the hydraulic pump 2 and hydraulic motor 3 thus has a low flow resistance.
• the bypass valve 13 is retained after the check valve 24 closes automatically in that the directional valve 27 is brought back into the rest position shown in FIG. 2 by the electronic control device 5.
• the hydraulic pressure at the control input of the bypass valve 13 wants to flow back to the tank 39.
• a flow control valve 25 allows a pressure medium flow that can be preset at it to pass and can flow back to the container 39 via the directional control valve 27.
• the bypass valve 13 closes with a delay in accordance with the flow rate set on the flow control valve 25.
• bypass valve 13 is provided with a bypass valve unit 12A (FIG. 3) open quickly and electrically in the same way hesitates to close again.
• an electromechanical or electronic switching device 35 is used, which is connected via a line 37 to one supply line 9 and via another line 38 to ground and thus to the other supply line 8 for the purpose of power supply.
• the switching device 35 receives its signal from the electronic control device 5 to open the bypass valve 13.
• a signal later supplied via the control line 26 of the switching device 35 causes the switching device 35 to close the bypass valve 13 again with a delay.
• the delay time for the closing of the bypass valve 13 can be set at an adjustable resistor 41 on the switching device 35.
• the hydraulic pump and / or hydraulic motor can be adjustable.
• a pressure switch 42 connected to line 10 or 11 (FIG. 1) ensures that the bypass valve 13 in the bypass valve unit 12 is not opened in the event of an extreme incline. In this way, the bypass valve 13 is blocked above a certain pressure threshold.
• control valve unit 26 control line

Landscapes

• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Fluid-Pressure Circuits (AREA)
• Control Of Fluid Gearings (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=6174401

Family Applications (1)

Country Status (3)

Families Citing this family (7)

Family Cites Families (5)

• 1983
  • 1983-05-11 WO PCT/EP1983/000120 patent/WO1984001419A1/de unknown
  • 1983-05-11 EP EP83901403A patent/EP0120021A1/de not_active Withdrawn
  • 1983-06-07 IT IT21494/83A patent/IT1163469B/it active

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events