EP2735726A9 - Hydrostatic motor for starting an internal combustion engine - Google Patents

Abstract

The invention relates to a hydrostatic engine (7) which is designed as an adjusting machine with a continuously variable displacement volume and as a pump and motor operable and with an internal combustion engine (2) is drivingly connected, wherein the engine (7) in pump operation with a suction side pressure medium a motor vehicle (9) sucks and in a to at least one consumer (V) guided delivery line (10) promotes and wherein the engine (7) is formed in engine operation as a hydraulic starter for starting the engine (2), wherein the engine (7) in engine operation on the suction side pressure medium from a pressure medium reservoir (25) can be fed. The engine (7) is provided with a Ausschwenkfeder (55), by means of which the displacer volume of the engine (7) controlling Verdrängervolumenstelleinrichtung (50) is acted upon in the position with maximum displacement volume when the engine is stopped (2), so that a direct starting operation of the internal combustion engine (7) by the engine operation of the engine (7) without immediately prior adjustment of the displacement volume adjusting device (50) of the engine (7).

Description

The invention relates to a hydrostatic engine, which is designed as an adjusting machine with a continuously variable displacement volume and is operable as a pump and motor and drivingly connected to an internal combustion engine, wherein the engine sucks in pumping operation with a suction side pressure medium from a container and in at least one Promotes consumer-led delivery line and wherein the engine is designed in engine operation as a hydraulic starter for starting the engine, wherein the engine in engine operation on the suction side pressure medium from a pressure medium reservoir can be fed.

Such hydrostatic engines, which serve in pump operation, in which the engine is driven by the running internal combustion engine to supply at least one consumer with pressure medium, and serve in engine operation, a hydraulic starter for starting the parked internal combustion engine are in mobile work machines, especially trucks, Agricultural machinery, forestry machinery and construction machinery, such as excavators, wheel and telescopic loaders, tractors, combine harvesters, forage harvesters, sugar beet or potato harvesters used.

In order to reduce fuel consumption during work breaks or work stoppages, a start-stop function is provided for the internal combustion engine, in which the unloaded combustion engine is switched off during work breaks or work stoppages and automatically restarted when a torque request by a work function or the traction drive. With a hydraulic starter, such a start-stop function of the internal combustion engine can be achieved in a robust and reliable manner.

From EP 2 308 795 A1 a generic hydrostatic engine is known, which sucks in pump operation, driven by an internal combustion engine engine with a suction side pressure medium from a container, to supply the load of a working hydraulics with pressure medium and in a motor operation, the Engine on the suction side Pressure medium from a pressure medium reservoir is supplied and the engine is driven by the supplied from the pressure fluid accumulator pressure medium, serves as a hydraulic starter for starting the parked engine.

If the engine is designed as an adjusting machine with a continuously variable displacer volume, the motor for engine operation is to be adjusted to a position with maximum displacement volume to allow the delivery of torque for starting the internal combustion engine. From EP 2 308 795 A1 (FIG. 2), it is known for this purpose to connect an adjusting device of the engine controlling the displacer volume with the accumulator, so that the displacer volume adjuster of the engine can be actuated with the pressure medium from the accumulator when the internal combustion engine is switched off. For this purpose, the pressure fluid reservoir is connected via a pressure reducing valve to a feed pressure circuit which serves to supply the adjusting device of the engine with pressure medium when the internal combustion engine is running. However, such a supply of the adjusting device with pressure medium from the accumulator memory leads to a high construction cost. The feed pressure circuit is downstream of a valve device that controls the engine operation of the engine by a connection of the accumulator with the suction side of the engine, connected to the accumulator so that the displacer volume adjusting means in time immediately before the starting process of the internal combustion engine with the pressure fluid from the accumulator in the position with Maximum displacer volume is adjusted. However, this results in the adjustment of the displacer volume adjusting device at the beginning of the startup process, a time delay during the starting process of the internal combustion engine, which leads to disadvantages in a start-stop function in which the starting process of the combustion engine in a short period of time.

The present invention has for its object to provide a hydrostatic engine of the type mentioned available, which allows for low construction costs, a start of the engine during engine operation of the engine in a short period of time.

This object is achieved in that the operable as a motor and pump engine is provided with a Ausschwenkfeder by means of at a direct start of the engine by the engine operation of the engine without temporally immediately prior adjustment of the displacer volume adjusting device of the internal combustion engine a displacer volume of the engine controlling displacer volume adjusting device is acted upon in the position with maximum displacement volume Engine at the beginning of the starting process of the internal combustion engine takes place. With such a Ausschwenkfeder is achieved with low construction costs, that the displacer volume control device of the engine is automatically acted upon when the engine is turned off in the position with maximum displacer volume. Upon actuation of the suction side of the engine with pressure fluid from the accumulator to the start of the engine is thus achieved that the engine by means of the Ausschwenkfeder at the beginning of the starting process of the engine is already in the position with maximum displacement volume, so that the starting process of the engine directly and no adjustment of the displacer volume adjuster to the maximum displacer volume is required at the beginning of the startup procedure. In conjunction with the Ausschwenkfeder invention thus a starting operation of the parked internal combustion engine during engine operation of the engine is made possible in a simple manner and with low construction costs in a short period of time.

According to an advantageous embodiment of the invention, the engine is designed as a unilaterally adjustable engine and the displacement adjustment means of the engine is adjustable starting from a position with a minimum displacer volume in a direction of adjustment. Such unilaterally adjustable engines are operated in the open circuit and allow for low construction costs and low energy consumption in pump operation, a supply of the connected consumers with pressure medium. With the Ausschwenkfeder such engine designed as a one-sided adjustable pump engine can be operated in a simple manner as a motor, which is driven on the suction side with pressure medium from the accumulator.

In terms of a simple structure, there are advantages if, according to a preferred embodiment of the invention, the Ausschwenkfeder at one with the Displacer volume adjusting device operatively connected actuating piston device of the engine attacks. A hydrostatic engine designed as a variable displacement pump usually has an actuating piston device with which the displacer volume adjusting device can be adjusted and thus the displacer volume can be changed. The Ausschwenkfeder invention can be supplemented such a control piston device in a simple manner.

According to an expedient embodiment of the invention, the actuating piston device can be acted upon by means of a control valve with a control pressure, wherein when the internal combustion engine, the control piston device is relieved of the control pressure. In pump operation can be generated by appropriate actuation of the control valve, a corresponding control pressure for acting on the control piston means and thus for the corresponding adjustment of the displacer volume. The control valve may for example be designed as a load-sensing control valve, which is actuated by the load pressure of the driven consumer, or be designed as an electrically controllable control or regulating valve.

Particular advantages arise when the consumer is designed as a working hydraulic system of a working machine and the engine supplied in pump operation, the working hydraulic system with pressure medium. The existing for the supply of the hydraulic working system variable displacement pump can thus be used in a simple manner as a hydraulic starter for starting the engine to allow a start-stop function of the internal combustion engine.

Preferably, the engine is designed as an axial piston machine in a swash plate design.

The invention further relates to a drive train of a vehicle, in particular a mobile work machine, with a hydrostatic engine driven by an internal combustion engine, wherein the engine forms a hydraulic starter of the engine during engine operation and supplies a working hydraulic system of the working machine with pressure medium in pump operation. With the hydrostatic engine according to the invention can be in a vehicle to simple Way a start-stop function are formed, which has a short start time of the parked engine.

Further advantages and details of the invention will be explained in more detail with reference to the embodiment shown in the schematic figure.

In the figure, a drive train 1 of a non-illustrated mobile work machine, such as a truck or a construction or agricultural machine, with a hydrostatic engine 7 according to the invention is shown in a schematic diagram.

The drive train 1 consists of an internal combustion engine 2, for example a diesel engine, a propulsion drive 3 of the vehicle driven by the internal combustion engine 2 and a working hydraulic system 4 driven by the internal combustion engine 2 as hydraulic consumers V.

The traction drive 3 is formed in the illustrated embodiment as a hydrostatic drive, which consists of an adjustable in the delivery volume drive pump 5, which is in drive connection to the drive with an output shaft 6 of the engine 2. The drive pump 5 is connected to one or more in the intake volume fixed or adjustable, not shown hydromotors in a closed circuit in connection, which are in a manner not shown in operative connection with the driven wheels of the machine.

The traction drive 3 may alternatively be formed as an electric traction drive with an electric generator driven by the internal combustion engine 2 and one or more electric traction motors. In addition, as a drive a mechanical travel drive with a mechanical transmission, such as a multi-step transmission or a power split transmission or a torque converter transmission, can be provided.

The working hydraulic system 4 includes working functions of the working machine, for example, in a truck, a working hydraulics for actuating a lifting device on a lifting mast, or in an example as an excavator trained construction machine the working functions of working equipment trained by a shovel.

To supply the consumer V formed by the working hydraulic system 4 with pressure medium which is designed as an adjusting machine with a continuously variable displacement volume hydrostatic engine 7 is provided, which is preferably designed as an axial piston machine in swash plate design. The engine 7 is operated in the open circuit and is for driving with the output shaft 6 of the internal combustion engine 2 in drive connection.

The engine 7 is the input side with the suction side by means of a suction pipe 8 with a container 9 in connection. An output side connected to the delivery side of the engine 7 in conjunction delivery line 10 is connected to a control valve means, not shown, by means of which the not shown hydraulic consumers of the working hydraulic system 4 are controllable. The control valve device preferably comprises one or more directional control valves for actuating the consumers. In the illustrated embodiment, a priority valve 12 is further shown, with which the preferred supply of a powered by the engine 7 consumer, such as a hydraulic steering device, can be ensured. The priority valve 12 is connected on the input side to the delivery side of the engine 7 and on the output side communicates with the delivery line 10 leading to the working hydraulic system 4 and a delivery line 13 routed to the steering device. The priority valve 12 is controlled by a spring 14 and the pending in a load pressure line 15 load pressure of the steering device.

The drive train 1 further comprises a feed pump 20, which is connected to the drive with the output shaft 6 in connection. The feed pump 20 is formed in the illustrated embodiment as a constant displacement pump with a constant displacement volume, which is operated in the open circuit. For this purpose, the feed pump 20 communicates with the suction side via a suction line 21 to the container 9 and conveys into a feed pressure line 22 connected to the delivery side, to which the corresponding consumers of a feed pressure circuit 23 are connected, for example adjusting devices for adjusting the displacement volume of the drive pump 5 and 5 of the engine 7, a hydrostatic feed device Traction drive, a brake system of the vehicle and pilot valves for the control valves of the working hydraulic system 4. To secure the feed pressure in the feed pressure circuit 23 of the feed pressure line 22 is a pressure limiting device 24, for example, a pressure relief valve assigned.

In the drive train 1 according to the invention, the engine 7 of the working hydraulic system 4 is designed as Zwequadrantentriebwerk, which is operable at the same direction of rotation and the same flow direction of the pressure medium as a pump and motor.

In pump operation, the engine 7 sucks pressure medium from the container 9 via the intake line 8 and delivers the pressure medium via the priority valve 12 into the delivery line 10 of the working hydraulic system 4 or the delivery line 13 of the steering device. In engine operation of the engine 7, in which the engine 7 is designed as a hydraulic starter of a start-stop function for starting the engine 2, the engine 7 is driven at the suction side with pressure medium from a pressure medium reservoir 25.

The accumulator 25 is connected for charging with pressure medium to the guided to the working hydraulic system 4 conveying line 10 of the engine 7 by means of a connecting line 26.

In the delivery line 10, an electrically actuated charging valve 27 is arranged, which is actuated at a control in a throttling the delivery line 10 throttle position for damming a pressure. The charging valve 27 is preferably designed as a retarder valve 28, which is operated in the braking operation of the vehicle in a throttle position to impose an additional, decelerating torque on the output shaft 6 formed by the crankshaft by damming a pressure in the delivery line 10, which is the torque acting on the engine counteracts the drive pump 5 and thus slows down the vehicle. In such a braking operation with throttling retarder valve 28 can also easily be done an energy recovery and the accumulator 25 are loaded, so that for loading the accumulator 25, the kinetic energy of the vehicle during a braking operation is used. The connection line 26 is in this case connected upstream of the charging valve 27 and thus between the charging valve 27 and the priority valve 12 to the delivery line 10.

In the connecting line 26, a check valve 30 is arranged, which is preferably designed as in the direction of the accumulator 25 opening check valve 31. Furthermore, the connecting line 26 between the check valve 30 and the accumulator 25, a pressure relief valve 32 to protect the pressure in the accumulator 25 is assigned. In the connecting line 26, a throttle device 33 is further arranged to limit the loading volume flow of the accumulator 25, which may be designed as a diaphragm or throttle. As shown, the throttle device 33 can be arranged upstream of the shut-off valve 30 or alternatively downstream of the shut-off valve 30.

The connecting line 26 between the check valve 30 and the accumulator 25 is further associated with a pressure sensor 34. The pressure sensor 34 is used to monitor the boost pressure and thus the state of charge of the accumulator 25.

The connection of the accumulator 25 with the suction side of the engine 7 for engine operation of the engine 7 is controlled by means of an electrically actuated control valve 35. The control valve 35 has a blocking position 35a and a flow position 35b, wherein the blocking position 35a is preferably carried out leak-tight with a blocking in the direction of the engine 7 check valve.

The control valve 35 is arranged in a branch line 36, which is guided by the connecting line 26 between the check valve 30 and the accumulator 25 to the guided to the suction side of the engine 7 intake 8.

In the intake passage 8 of the engine 7 a blocking in the direction of the container 9 check valve 37 is arranged, which is preferably designed as a blocking in the direction of the container check valve 38.

An electronic control device 40 is connected to the input side of the pressure sensor 34 and serves to control the charging valve 27 and the control valve 35th

The engine 7 designed as an adjusting machine with a continuously variable displacer volume has a displacer volume adjustment device 50 for adjusting the displacer volume, for example a swashplate of an axial piston machine of swashplate design that is adjustable in inclination. The displacer volume adjusting device 50 can be actuated by means of an actuating piston device 51, which is in operative connection with the displacer volume adjusting device 50. The engine 7 according to the invention is designed as a unilaterally adjustable engine, in which the displacer volume adjusting device 50 is adjustable starting from a position with minimum displacer volume, preferably a position with zero displacement in a direction or pivoting direction to a position with maximum displacement.

The actuating piston device 51 has an actuating pressure chamber 51a acting in the direction of the maximum displacement volume and a control pressure chamber 51b acting in the direction of the minimum displacement volume, the pressurization of which is controllable with a control pressure or its discharge to the vessel 9 by means of a control valve 52. The control valve 52 is connected to the supply of pressure medium and for generating a control pressure in the control pressure chambers 51 a and 51 b via a branch line 53 to the feed pressure line 22 and thus the feed pressure circuit 23. Furthermore, the control valve 52 has a connection to a tank conduit 54 guided to the container. The control valve 52 is preferably electrically actuated. When the internal combustion engine 2, the control pressure chamber 50a, 50b of the control piston device 50 are relieved. In the illustrated embodiment, the control valve 52 is designed as a control valve, wherein a mechanical feedback and feedback 56 of the actual position of the displacement volume control device 50 is provided on the control valve 52.

In order to pressurize the engine 7 for engine operation in the position with maximum displacement volume when the engine is switched off 2, a Ausschwenkfeder 55 is provided according to the invention, which is in operative connection with the control piston 51 and the displacement volume control device 50 with the engine stopped 2 in the position with maximum displacement volume for the engine operation of the engine 7 is applied. The Ausschwenkfeder 55 can be arranged for this purpose in the control pressure chamber 51a of the control piston 51.

With the Ausschwenkfeder 55 is achieved that the operated during engine operation as a hydraulic starter of the engine 2 engine 7 is switched off with the engine 7 in the position with maximum displacement volume. For the starting process of the internal combustion engine 2, the control valve 35 is actuated in the flow position 35b, so that the pressure fluid from the pressure fluid reservoir 25 to the suction side of the engine 7 flowing pressure medium due to the already in the position with maximum displacement volume displacement valve actuator 50 directly to a motor operation and a torque output of the motor operated engine 7 leads into the drive train 1. A directly preceding the starting process of the internal combustion engine 2 adjusting the displacement volume adjusting device 50 of the engine 7 to the maximum displacement volume or adjusting the displacement volume control device 50 of the engine 7 to the maximum displacement volume at the beginning of the starting process of the engine 7 is thus not required, so that the starting process of Internal combustion engine 2 is carried out with the engine 7 according to the invention in a short period of time in a start-stop function.

Claims (7)

Hydrostatic engine (7), which is designed as an adjusting machine with a continuously variable displacer volume and is operable as a pump and motor and drivingly connected to an internal combustion engine (2), wherein the engine (7) in pump operation with a suction side pressure medium from a container (9 The engine (7) is designed in engine operation as a hydraulic starter for starting the internal combustion engine (2), wherein the engine (7) in engine operation at the Suction-side pressure medium from a pressure medium reservoir (25) can be supplied, characterized in that the motor and pump operable engine (7) is provided with a Ausschwenkfeder (55), by means of the switched-off internal combustion engine (2) a displacement volume of the engine (7) controlling displacer volume adjusting device (50) is acted upon in the position with maximum displacer volume, so when the suction side of the engine (7) is pressurized with fluid from the accumulator (25), the engine (7) is directly started by engine operation of the engine (7) without promptly adjusting the displacer volume control means (50) of the engine (7) he follows. Hydrostatic engine according to claim 1, characterized in that the engine (7) is designed as a unilaterally adjustable engine and the displacement volume adjusting means (50) of the engine (7) is adjustable starting from a position with a minimum displacement volume in a direction of adjustment. Hydrostatic engine according to claim 1 or 2, characterized in that the swivel-out spring (55) acts on an actuating piston device (51) of the engine (7) which is in operative connection with the displacer volume adjusting device (50). Hydrostatic engine according to claim 3, characterized in that the actuating piston device (51) by means of a control valve (52) can be acted upon with a control pressure, wherein when the internal combustion engine (2), the control piston device (51) is relieved of the control pressure. Hydrostatic engine according to one of claims 1 to 4, characterized in that the consumer (V) is designed as a working hydraulic system (4) of a working machine and the engine (7) in pump operation, the working hydraulic system (4) supplied with pressure medium. Hydrostatic engine according to one of claims 1 to 5, characterized in that the engine (7) is designed as an axial piston machine in a swash plate design. Drive train of a vehicle, in particular a mobile work machine, with one of an internal combustion engine (2) driven hydrostatic engine (7) according to one of the preceding claims, wherein the engine (7) in engine operation forms a hydraulic starter of the internal combustion engine (2) and in pump operation Working hydraulic system (4) of the working machine supplied with pressure medium.

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