GB2205632A

GB2205632A - Drive device with a primary energy source, a transmission and a pump

Info

Publication number: GB2205632A
Application number: GB08806460A
Authority: GB
Inventors: Werner-Georg Schroeder; Binio Binev
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 1987-04-03
Filing date: 1988-03-18
Publication date: 1988-12-14
Anticipated expiration: 2008-03-18
Also published as: DE3711233A1; GB9105860D0; FR2613435A1; GB2240836A; GB8806460D0; FR2613435B1; GB2240836B; GB2205632B

Description

2205632 "DRIVE DEVICE WITH A PRIMARY ENERGY SOURCE, A TRANSMISSION AND A

PUMP, AND METHOD OF OPERATION THEREOF."

This invention relates to a drive device with a primary energy source, preferably an internal combustion engine, the adjusting member of which is connected to an output of a controller, and with a transmission driven by this primary energy source, preferably a hydrostatic transmission, and with a further pump used for charging at least one consumer of hydraulic energy, a deliberately actuatable valve being connected between this pump and the consumer, the switching travel of the valve being a signal for the setpoint of the current flowing through the valve.

The drive device is preferably used for driving a vehicle with hydraulic auxiliary drives, particularly a fork lift truck.

The object of the present invention is to create a drive device in which the required drive result is achieved with minimum energy expenditure and minimum constructional expenditure.

According to the present invention, the above- stated object is achieved by the fact that the controller is supplied with a signal for the setpoint of the transmission output speed and a signal for the the actual rotational speed of the primary energy 2 source and a signal for the valve switching travel and by the fact that a device controlling the current flowing through the valve is connected to a second output of the controller.

In the normal cas e, several consumers are con- nected in parallel with one another via one valve each to the delivery line of the pump. The valve is suitably a valve which does not throttle at least in the switch position releasing the current from the pump,to the consumer; that is to say, the valve only has a switching function without current controlling function. If the direction of the current is reversed, a throttling may be required, for example if the consumer charged is a cylinder which is used for lifting a load, in which arrangement the load drops under the action of its own weight in the second position and the rate of dropping is to be controlled by throttling in the valve.

The further pump driven by the primary energy source can be adjustable, the adjusting member of the pump being connected to a further controller output so that the pump is always adjusted in such a manner that it delivers exactly the current which corresponds to the setpoint which is predetermined by the actuating member for the switching valve. This prevents a current of hydraulic pressure medium being 3 unnecessarily delivered against a pressure.

However, adjustable pumps are expensive. To find a different approach avoiding an adjustable pump whilst accepting a slight energy loss, an approach has been proposed in which the device controlling the current flowing through the valve is a current divider which, when not actuated, allows the current delivered by the pump to drain without pressure to a container but when actuated dams up in front of this valve the pressure required for generating the required current at the actuated switching valve. If.the actuated switching valve is a proportional valve, this proportionality occurs between pressure and controlled travel and it must be assumed that the set-point signal for the speed of movement of the consumer driven by means of this valve is given with the distance along which the actuating member of the switching valve is displaced. In the previously used block valves, a pressureless circula tion is provided in the neutral position of the actuating levers and thus of the slide valves and a pressure is dammed up to a deliberate extent by fine control grooves only with a deliberate actuation of the slide valve by means of which the latter is moved out of its neutral position.

It is particularly suitable if the transmission, 4 which is preferably the driving transmission of a vehicle, is a hydrostatic transmission and if the latter is hydraulically controlled in that a branch line, which leads to the adjusting device of the hydrostatic transmission and in which a pressure reducing valve which regulates to constant pressure is arranged which is then followed by the valve by means of which the control pressure acting at the control pressure accepting cylinder of the pump is deliberately adjusted, is connected to the delivery line of the pump. In a suitable further development of this, the actuating member of the adjustable pump is also connected to this line between the pressure reducing valve and the adjusting member of the hydro static transmission via a pressure reducing valve controlled by the controller so that the actuating member of the adjustable pump is supplied with energy through this line and the controller can influence the adjustment.

It is known that a vehicle having a hydrostatic transmission can be braked in travelling drive made by the hydrostatic transmission bei'ng adjusted to a smaller output speed.

The braking energy is then supplied to the primary energy source via the hydrostatic transmission with the consequence that the rotational speed of the primary energy source rises and absorbs this "drag power" at least when the primary energy source is a piston-type internal-combustion engine. It is also known, in this case, to throttle a current delivered by the additional pump in a valve in order to convert braking energy into heat in this valve so that this proportion of energy converted in the valve is not supplied to the primary energy source (see German Offenlegungsschrift No-3,247,335). Such an action can be very easily achieved by means of the drive device according to the invention if, in the braking state, the electric controller in a drive device with hydraulic current divider closes the current divider and uses it as a throttle valve or in a drive device with an adjustable additional pump fully drives the latter so that its current is delivered in opposition to the pressure limiting valve.

In the text which follows, some embodiments of a drive device with a primary energy source, a trans- mission and a pump, and also some embodiments of a method of operating such a device will be explained (by way of example only) with reference to the circuit diagrams shown in the drawings, in which:- Figure 1 shows a drive device with controllable additional pump; and Figure 2 shows a drive device with current 6 dividing device.

Referring firstly to Figure 1, an internal- combustion engine 1 drives, via a shaft 2, a Pump 3 of a hydrostatic driving transmission in which the pump 3 is connected via two lines 4 and 5 in a closed circuit to two hydraulic motors 6 and 7. The shaft 2 also drives an adjustable pump 8 and another non adjustable pump 9 which is only used for charging a steering device 10 of the vehicle.

Valves 12, 13, 14'and 15 are connected in parallel with one another to the delivery line 11 of the pump 8, a line 16 leading to a lifting cylinder coming from the valve 12. Two lines 17 leading to a pair of tilting cylinders are connected to the valve 13.

The valve 14 is connected to a pair of lines 18 which lead to a further consumer of hydrostatic energy and, similarly, two lines 19 leading to a further consumer of hydrostatic energy are connected to the valve 15.

Lifting cylinder, tilting cylinder and other consumers are not further represented in the drawing.

The valves 12, 13, 14 and 15 are provided with deliberately actuatable actuating members 20, 22, 22 and 23, respectively, and said valves 12, 13, 14 and 15 are also connected to a drain line 24 which leads to a container 25.

A pressure limiting valve 26, which, for 7 example, is set to 200 bar in the illustrated embodiment and which protects the line 11 against inadmissible excess pressure, is connected between the lines 11 and 24.

Furthermore, the line 11 is connected to a branch line 27 which leads to a pressure reducing valve 28 which, for example, is set to 18 bar in the illustrated embodiment. To the output of said valve 28, there is connected a line 29 which leads to the electrically driven proportional valve 30 which (Via a second valve 31 provided as safety circuit in each case) charges one of the two pressure spaces in an actuating cylinder 32 in which an actuating piston 33 can be displaced which is mechanically connected to the actuating member of the pump 3. The elements 30, 31, 32, 33 constitute the actuating device of the hydrostatic transmission.

Line 29 is furthermore connected to a feed line 34 which is used for feeding pressure medium via feed valves 35 into one of the two lines 4 and 5 which, in each case, carries the lower pressure in order to compensate the leakage losses in the closed circuit 3, 4, 5, 6, 7.

Line 29 is al so connected to a line 36 which leads via an electrically controlled proportional valve 37 to an actuating cylinder 38 in which an 8 actuating piston 40, which is connected to the actuating member of the pump 8, can be displaced against a spring 39.

The primary energy source 1 is connected to an actual speed valve transmitter 42 which is connected via an electric line 43 to a controller 44. One output of this controller 44 is connected to a line 45 which leads to an electrically drivable adjusting member 46 of the primary energy source 1.

The actuating members 20, 21, 22 and 23 are connected to travel signal transmitters 47, 48, 49 and 50, respectively, and these transmitters are 1 connected to the controller 44 by lines 54, 53, 52 and 51, respectively.

A setpoint signal transmitter 55 is deliberately actuatable and supplies via a line 56 a setpoint signal as reference variable to the controller 44.

An electric signal line 59 which leads to the proportional valve 37 is connected to a further output of the controller 44.

Two lines 60 leading to the two coils of the valve 30 are connected to a further pair of outputs of the controller 44.

The mode of operation of the arrangement described above is as follows:In norma driving mode, the setpoint for the 9 travelling speed is entered via the setpoint trans mitter 55 into the controller 44 which, in turn, drives the adjusting member 46 of the primary energy source 1 and the valve 30 by means of which the adjustment position of the Pump 3 is determined. In this context, the pump 8 is adjusted almost to zero lift position and thus only delivers a small current.

If one of the actuating members 20, 21, 22 or 23 is actuated, a signal is emitted by the respective associated travel signal transmitter 47, 48, 49 or 50 to the controller 44 which, on the basis of this, emits through the line 59 a signal to the valve 37 by means of which the actuating cylinder 38 is then charged in such a manner that the actuating member of the pump 8 is deflected in such a manner that the pump 8 supplies the current required at the respective driven valve 12, 13, 14 or 15.

In the operating conditions in which the valves 12, 13, 14 and 15 are switched to neutral position, that is to say no consumer is driven, the additional pump 8 is adjusted by the controller 44 to such a tilted position that the pressure set by the pressure reducing valve 28 is just maintained in the line.11.

The pressure to which the pressure limiting valve 26 is set is higher than the pressure level controlled by the pressure reducing valve 28 so that the pressure required for charging the actuating pressure spaces in the actuating cylinder 32 and the actuating pressure space in the actuating cylinder 38 is always available in the line 29.

If braking occurs via the hydrostatic transmission 3, 4, 5, 6, 7 and as a result the speed of the internal-combustion engine 1 is driven up, the transmitter 42 provides a signal to the controller 44 which correspondingly provides via the line 59 such a signal to the valve 37 that the valve 37 completely opens and thus the pump 8 is swung out to full delivery current, said pump 8 delivering said full delivery currenL against pressure to which the pressure limiting valve 26 is set, the delivery current draining through this pressure limiting valve 26 into the container 25 with the consequence that the energy converted in the pump 8 to generate the full delive:1,y current against the pressure of the pressure limiting valve 26 is converted as additional braking energy.

The result of the fact that the pressure limiting valve 26 is connected in parallel with the switching valves 12, 13, 14 and 15 is that none of the consumers connected to the lines 16, 17, 18 or 19 can be charged with a higher pressure than the pressure to which the pressure limiting valve 26 is set.

In the embodiment according to Figure 2, three additional pumps 60, 61 and 62, all three of which are constant pumps, are driven by the internal combustion engine 1 via its shaft 2. The pump 61 is only used for charging the actuating device 30, 31, 32, 33 for the transmission Pump 3 via the line 63 to which a pressure limiting valve 69 is connected via the line 34. The pump 62 is only used for charging the hydrostatic auxiliary power steering device 65 via the line 64.

The pump 60 delivers via line 66 to the valves 123 13, 14 and 15. An electrically driven current divider throttle valve 67, which is connected to an output of the controller 44 via the line 68, is connected in parallel with these valves 12, 13, 14 and between the lines 66 and 24.

If none of the consumers is charged (that is to- say, if none of the valves, 12, 13, 14 or 15 is driven), the valve 67 is driven into its "open" position via the line 68 so that the delivery current of the pump 60 drains pressureless via the valve 67 through the line 24 into the container 25. If, however, one of the actuating members 20, 21,225 23 is actuated, said valve 67 is moved into a throttling position and the more the actuating member 20, 21, 22 or 23, respectively, is moved out of its neutral position, the greater the throttling action.

If, in braking mode, the transmitter 42 12 indicates that the internal-combustion engine 1 is R.

driven up to a rotational speed exceeding a prescrib ed limit value, the valve 67 is moved into a throttling position. A pressure limiting valve 70 protecting the line 66 against inadmissibly high pressure is connected between the lines 66 and 24.

Double-action consumers are connected to the pump in each direction of movement via the respective valve 12, 13, 14 or 15. This does not apply to consumers which are only braked in one operating direction, for example the lifting hydraulics in fork lift trucks which are only braked in lowering mode. For such a consumer, it is provided that the respective valve 12, 13, 14,or 15 will only operate in a non-throttling manner in the switch position establishing the connection between pump and consumer and will operate in a throttling manner in the opposite switch position.

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Claims

CLAIMS:

1. Drive device with a primary energy source whose adjusting member is connected to an output of a controller, and with a transmission driven by the latter and with a pump used for charging at least one consumer of hydraulic energy, a deliberately actuatable valve being connected between pump and consumer, the switching travel of the valve being a signal for the setpoint of the current flowing through the valve and the drive device preferably being used for driving a vehicle with auxiliary hydrau lic drives, particularly a fork lift truck,wherein the controller is supplied with a signal for the setpoint of the transmission output speed and a signal for the actual primary energy source speed and a signal for the valve switching travel and wherein a second out put of the controller is connected to a device which controls the current flowing through the valve.

2. Drive device according to Claim 1, wherein said last-mentioned valve is a valve which operates in a nonthrottling manner at least in the switch position releasing the current from the pump to the consumer.

3. Drive device according to Claim 1 or Claim 2, in which the pump is adjustable, the adjusting member of the pump being connected to a further output of the controller.

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4. Drive device according to Claim 1 or Claim 2, wherein the device controlling the current flowing through the valve is a current divider with a current divider throttle valve which is open in the undriven state, is conn6cted at the drain side to a tank drain line and throttles in the driven state.

5. Drive device according to Claim 3, in which the transmission is a hydraulically driven trans mission, preferably a hydrostatic transmission,wherein a branch line, which leads to the actuating device of the hydrostatic transmission and in which a pressure reducing valve which regulates to constant pressure is arranged, is connected to he line between said pump and said lasl-mentioned valve.

6. Drive device according to Claim 5,wherein an actuating cylinder which forms a part of said adjust ing member of the pump is connected to a line between a pressure reducing valve and the actuating device of the hydrostatic transmission via a pressure reducing valve controlled by the controller.

7. Drive device according to Claim 6, wherein another pressure reducing valve, which is set to a higher pressure than that to which said first-mentioned pressure reducing valve is set, is arranged in I parallel with said last-mentioned valve.

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8. Drive device according to Claim 2, wherein at least one of said last-mentioned valves is a valve which throttles a current flowing from the consumer to a drain line in dependence on adjustment.

9. Method for operating a drive device according to Claim 3 in braking mode, wherein, when a limit value of the rotational speed of the primary energy source is exceeded, a signal is supplied to the controller and on the basis of this signal the pump is so controlled as to ensure that it occupies its adjusted position of maximum working volume per revolution.

10. Method for operating a drive device according to Claim 11 in the braking state, wherein,when a limit value of the rotational speed of the primary energy source is exceeded, a signal is supplied to the controller and the current divider throttle valve is adjusted into a severely throttling position by said controller.

11. Drive device with a primary energy source, a transmission and a pump, said drive device being constructed, arranged and adapted to operate substan tially as hereinbefore described with reference.to and as illustrated in Figure 1 or Figure 2 of the accom panying drawings.

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12. Method for operating a drive device as claimed in Claim 11, said method being substantially as hereinbefore described with reference to Figure 1 or Figure 2 of the accompanying drawings.

13. Any features of novelty, taken singly or in combination, of the embodiments of the invention hereinbefore described with reference to the accom panying drawings.

F,ublished 1988 t TIe Patent Officc. tate ljo-,;se. Ce, 71 Hcjbc.-j_. London WGIR 4TP Further copies maybe obtained from The Patent Office, S-e-- Brar ch. S' 11 a::,, C.-ky. Orpington. Kcrt BR5 3RD Printed by Multiplex techniqjes MI. St Mary Cray. Ke,.. Con. 1 87