Displacement unit and hydraulic start-stop system comprising such a displacement unit.

[0001] The present invention relates to a displacement unit and a hydraulic start-stop system comprising such a displacement unit.

[0002] It is well known, mobile work machines that have a respective hydraulic devices for performing work activity can be used. In the hydraulic drive system comprises a controllable or adjustable hydraulic pump preferably in the conveying volume, typically as an internal combustion engine mechanically coupled with a prime mover. The internal combustion engine comprises an electric starter for starting of the internal combustion engine usually here, powered by a battery. In this battery is charged by a generator driven by the internal combustion engine.

[0003] It is known in the art, an internal combustion engine, particularly a diesel engine, by electric starter systems, by electric starter generators, the association of initiator device and generator are in a component, and by hydraulic start-stop systems warmed. An internal combustion engine it is necessary at a tempering operation, its output shaft to rotate, a piston arranged in the internal combustion engine perform the operating cycles.

[0004] The state of the art provides therefor a hydraulic start-stop system from, mechanically coupled with an internal combustion engine wherein a displacement unit not only by the internal combustion engine is driven in the "pump operation", but by use of a displacement unit start the internal combustion engine in "engine operation". The work required for the hydraulic power hydraulic displacement unit is, driven by the mechanical coupling to the engine sucks in a fluid reservoir and a fluid from, typically an oil or the like, and forwards this on the high pressure side to the working hydraulic. Thus it is possible for example hydraulic work, to process a excavator arm or raise the shield a bead.

[0005] In the "engine operating" is provided, by means of the stopped engine that a displacement unit is tempered. The displacement unit connected to the inlet port will, the fluid can toward its engine, the converting a hydraulic power in a rotational power, a up-branching line itself, which is at one end thereof with a fluid reservoir via a one-way valve in communication and by its other end via a switchable valve in communication with an accumulator. The accumulator has a sufficient amount of pressurized fluid, said fluid such can be used, a stationary internal combustion engine warmed. In the path between the accumulator and the engine to the displacement unit arranged closable valve is opened, to permit inflow of pressurized fluid into the displacement unit.

[0006] The pressurized fluid reaches the engine, coupled with the displacement unit leads to a rotation of the output shaft of said engine. This rotation of the output shaft during starting an internal combustion engine necessary by replacing the typical activity of a electric starter system.

[0007] It is the objective of the present invention a stop-start system suitable for hydraulic displacement unit advantageously hone.

[0008] The invention displacement unit, in particular an axial piston machine may represent, comprises a housing, an engine for converting the rotational power into hydraulic power and a suction port for supplying a fluid to the engine. The displacement unit is characterized by a one-way valve, the displacement unit disposed in the housing.

[0009] The arrangement of the one-way valve in the housing of the displacement unit leads to a reduction of the flow resistance between the hydraulic oil storage tank in the pump operation and the operating (also: reservoir of fluid) engine the displacement unit. A lower total flow resistance provides a higher suction limit speed, the characterized an operating state of a pump, wherein a filling defect occurs in a stroke due to vacuum forming, which might lead to reducing the conveying flow of the pump and damaged the pump cavitation erosion by subsequent delivery stroke in. For a high suction limit speed it is advantageous, to keep the flow resistance as low as possible.

[0010] Since the total flow resistance between the hydraulic oil storage tank and the engine (also: reservoir of fluid) from the supply line from the storage tank to the displacement unit for one-way valve and the supply line from the one-way valve until engine results, decreases the overall flow resistance, when the portion of the highest flow resistance, the area around the one-way valve, is arranged in the vicinity of the engine. This is explained, since the cross-section of the intake passage from the suction port toward the displacement unit for engine typically decreases. It can then a constant pressure drop the flow cross-section of the valve (or flow resistance are performed) becomes smaller, the closer this is located on the engine. A check valve is also exported to realize and requires less geometrically smaller cheaper installation space. The art therefore typically outside the housing the displacement unit arranged check valves (also: one-way valves) the aforementioned positive effects can be achieved.

[0011] Further use the displacement unit between the engine and motor is at a high pressure level of the fluid before the one-way valve for. It follows, that the oil connection between these two components must be high-pressure sealing. Would be the one-way valve disposed outside of the housing of the displacement unit, the corresponding hydraulic hose should withstand the high pressure load. According to the invention displacement unit, wherein the one-way valve is arranged in the housing itself, to the suction connection of the displacement unit a hydraulic hose must withstand the low pressure can only guided.

[0012] According to an optional modification of the invention is the one-way valve in the flow path between suction port and arranged engine.

[0013] Is preferably integrated in the housing of the displacement unit the one-way valve.

[0014] According to a further modification of the invention is possible, the one way valve in an intake passage of the displacement unit or a connecting plate cooperates with the connecting plate.

[0015] According to a preferred variation of the invention decreases the cross section of the flow path from the suction port toward engine, preferably this reduction takes place continuously and the one-way valve is arranged at a position in the flow path, the cross section of the flow channel is not at maximum.

[0016] The one-way valve in the flow path from the suction port is preferably arranged spaced toward engine.

[0017] According to an optional modification of the invention is adapted to the one-way valve, the fluid only in the direction of a flow of the fluid flowing in the opposite direction and engine minimize or prevent.

[0018] After a training of the invention is the one-way valve or a spool valve a check valve, preferably a high pressure operated spool valve.

[0019] According to a further extension of the invention comprises a second terminal the displacement unit for delivering a fluid to the engine, wherein the suction port and the second port from the first outgoing flow paths and the one-way valve in the flow path to a common combining region between first suction port and the United common flow path is disposed.

[0020] By providing said second terminal for supplying a fluid to the engine is suitable especially for use in a hydraulic displacement unit the stop-start system. As already explained in the introductory part of the description, the displacement unit with a starting an internal combustion engine mechanically coupled to the motor drive but not used for the operation of the pump and BERT. The fluid stored under pressure in a pressure accumulator is fed for the engine. In order to prevent a flow of the pressurized fluid in the storage tank is provided the one-way valve. The inflow of a fluid to flow from the first suction port is the second port and not possible.

[0021] According to a preferred embodiment of the invention is the one-way valve with a valve seat and flow optimized flow optimized acting together. A flow optimized one-way valve and a flow valve seat minimize turbulence during a fluid inflow along a optimized fluid passage opening at the suction port.

[0022] By the one-way valve closable flow path is preferably a venturi contour, by the one-way valve in the lowest point of a flow cross-section in the region of the valve is closable.

[0023] During inflow of the fluid, for example a hydraulic oil, in pump operation the operating displacement unit at the point of least flow cross-section is achieved the maximum flow rate, which causes a suction effect for the pump mode supporting.

[0024] According to a further extension of the invention has an optimized curvature on the venturi contour, a vortex by the one-way valve to minimize fluid flowing.

[0025] Preferably the suction port is connectable with a flange plate, as a part of a flow path of the suction port with the venturi contour formed is carried out.

[0026] The invention also relates to a hydraulic stop-start system, the one of the previously displayed variants comprises a displacement unit.

[0027] Preferably comprises hydraulic start-stop system further an internal combustion engine, the displacement unit is mechanically coupled with and adapted to, the displacement of the displacement unit and drive unit to be driven, and an accumulator, an outlet port of the displacement unit and a second terminal for supplying a fluid to the engine is connected to the displacement unit, wherein the first suction port is connected with a fluid reservoir.

[0028] According to an optional modification of the hydraulic start-stop system is a pressurized fluid in the fluid storage used, to start an internal combustion engine, in which a fluid flowing from the fluid storage drives the displacement unit and the mechanical coupling between displacer unit and engine for the internal combustion engine exerts a starting movement, wherein preferably for directing the fluid between a first valve and a second valve between the outlet port and the second port fluid storage and a connection to the fluid reservoir are provided.

[0029] The present invention also further relates to a mobile working machine, in particular a mobile excavator, a tracked excavator, a mobile crane, with a hydraulic start-stop system according to one of the above-described variants.

[0030] Further features, details and advantages of the invention are apparent from the detailed discussion of the following Figures.

[0031]

Fig. 1: a schematic representation of a displacement unit of the invention with an integrated rear -

impact valve,

Fig. 2: a schematic representation of a portion of the displacement unit of the invention,

Fig. 3: a schematic representation of the displacement unit according to another embodiment of the invention,

Fig. 4: an enlarged detail view of the further embodiment, and

Fig. 5: a circuit diagram for a hydraulic start-stop system according to the invention.

[0032] Fig. 1 shows a schematic representation of a displacement unit of the invention, for example an axial piston machine, wherein said portion is a suction port 4 the displacement unit 1 is designed in detail. One can see, that a check valve is arranged in the housing 1 2 3 the displacement unit. In the regular operation of the positive displacement pump a fluid through the suction port 4 1 unit flows into the interior of the displacement unit 1, will therefore from the engine (not shown) sucked. The engine is driven via a mechanical coupling with a not shown internal combustion engine. The suction of the engine into its open position and allows fluid communication between the non-return valve 3 mad a storage reservoir and the engine.

[0033] Fig. 2 shows an enlarged representation of the displacement unit 1 in the region of the suction port 4. The housing 2 4 7 and a second terminal on here features an suction port, both of which are adapted to respectively, a fluid in the direction of the engine to the displacement unit 1. The inflow of a fluid into the second terminal 7 from the suction port to flow through the check valve 4 is prevented 3. In the second terminal 7 is therefore a fluid flowing the displacement unit supplied the engine 1. The flow path of the suction port 4 and the flow path of the second terminal 7 downstream to a common flow path combining 8, via the fluid communication to the engine is produced.

[0034] 3 Is slidably mounted in a recess in the check valve, so that upon orientation of the engine or of the second terminal from a closed position of the setback 7 pressure passes. But is due to movement of the engine a suction pressure exerted on the check valve 3, it moves away from its closed position into its open position by the suction port 4 and a fluid can flow in the direction of the engine and the fluid flow holes 13. Further recognized, that a flange plate 6 on the housing 2 the displacement unit, the intake duct has a 5. One can see, that the suction channel 5 towards the position its flow cross-section, the closable by the check valve is, reduced. The so used in a hydraulic displacement unit 1 start-stop system is formed, the suction channel 5 with a fluid reservoir is fluidly connected to a storage tank or. Flow from the storage tank through the check valve 3 in the direction of the engine then takes place at a pump operation of the displacement unit 1 is used but 1st displacement unit, an internal combustion engine temper or on an occasion to support operation, is a fluid at a large flows and the displacement unit 7 at said second terminal used in motor operation. At said second terminal 7 by the inflowing fluid into its closing position the check valve 3 is pushed, a flow of the fluid in the storage tank to prevent. Instead it flows in the direction of the engine, where it causes a movement of the engine, the output shaft of the internal combustion engine in turn, mechanically coupled to the integral with the engine, is converted into a starting movement.

[0035] Fig. 3 shows a flow check valve and a flow valve seat 3 optimized representation of the optimized one recognizes the flow check valve on the slanted surface optimized 9th 3 of the valve piston bears on the valve seat 9 with the wall of a 16th this such flow path in contact, a seal for the fluid that takes place. It is the flow path with an optimized venturi contour shape provided, the speed increasing and reducing a flow vortices and thus lowering the flow resistance obtained. This venturi contour shape is interrupted only at the valve seat, a satisfactory sealing effect in a closed state of the valve to obtain 3. It also recognizes, that the flange plate 6 to the housing 2 in the transition region 14 is an O-ring, to obtain tightness. Another O-ring is in the flow path 14 is also peripherally between the venturi contour shape arranged projecting into the housing 2.

[0036] Fig. 4 shows a enlarged section of Fig. 3 in the region of a valve seat thereto well recognized the 9th optimized, beveled contour of the venturi shape 17, 18, the piston 16 sealingly on the valve seat 9 when the valve closes. The represented with the reference symbol 19 this element corresponds to an undercut.

[0037] Fig. 5 is a schematic representation of the hydraulic 30th one recognizes an internal combustion engine start-stop system 31, via a mechanical coupling with the engine of the displacement unit 1 39 35 is coupled. The characteristic of the invention within the housing 2 also recognized for the displacement unit 1 arranged one-way valve 3, here a check valve. The displacement unit 1 at its suction port 4 is further with a fluid reservoir 34 connected. This 34 serves as a reservoir for the fluid reservoir of fluid.

[0038] The displacement unit 1 also has a second terminal 7 on, is adapted to, in the direction of the engine to a fluid 39. The second terminal 7 via a first valve 36 is in communication with an accumulator 32 here. The fluid memory 32 is designed to, receive a fluid under a high pressure and to store this in itself. At the outlet port 33 is the displacement unit 1 hydraulic working in conjunction. Further communicates with said outlet port 33 a second valve and a third valve 37 38 in conjunction. A flow path between the outlet port 33 and the third valve 38 can the fluid reservoir 34 closing or opening. The second valve closing or opening a connection to the accumulator 32 can 37.

[0039] Fig. 5 is based on the system shown in different operating conditions, the system can occupy, explained. In a first operating state is the working hydraulic fluid supplied. This corresponds to normal operation. The valves 38 are herein, 37 and 36 in a closed state. In normal operation the displacement unit 31 is driven by the diesel engine 1. The displacement unit 1 sucks in the working fluid, for example a hydraulic oil, via the check valve 3 on. The check valve 3 is here constructed so, that this minimal pressure drop along the passage direction results. Depending on the volume flow, i.e. speed and displacement volume of the displacement unit 1 must not be below a certain suction pressure. As a result hence limiting the suction pressure by a conduit. From the outlet port 33 (also: work port) promotes the displacement unit 1 the fluid at the working hydraulic valve slide located in the. The displacement unit 1 is subjected to a load-sensing control here, which ensures, that the displacement unit 1 according to a volume flow request the conveying volume flow adjusts. This is done by adjusting the axial piston machine at a skew angle.

[0040] Fig. 5 shown in a further operating state of the system loads the accumulator 32. The valves 36 and 38 are closed in this state. The valve 37 is in its open position. For charging the pressure accumulator 32, as the hydraulic accumulator may be carried out, by the displacement unit 1 is conveyed fluid into the accumulator 32 promoted.

[0041] As a further operating state can look at the starting of the diesel engine. The diesel engine can start off, this must be in a stopped state. Then all valves 36, 37 and 38 to close. The hydraulic accumulator 32 must further be sufficiently charged in switched-off diesel engine 31, a start requirement to meet. The valves 36 and 38 are opened to initiate the starting operation, whereas the valve 37 remains closed. The pressurized fluid passes from the accumulator 32 via the second terminal 7 to the suction channel of the displacement unit 1. This closes the check valve 3 in accordance with the connection between the accumulator and the pressure ratio there abutting 32 34 the fluid collection tank. The suction channel 7 the displacement unit 1 is therefore under pressure and the displacement unit 1 operates motor. The drive train is accelerated, whereby the starting speed of the motor is exceeded, whereby immediately downstream of the motor to its operating speed is towed launched high. Since the valve 38 is opened, the fluid passes from the working port 33 the displacement unit 1 back into the collection tank 34. During this starting process can not be powered with hydraulic operating hydraulics.

[0042] The stop-start system described above is especially suitable for use hydraulic in a mobile working machine. Here it is possible, that the working machine, wherein optionally via a pump to the internal combustion engine drives one or more hydraulic displacement units transfer case. Here it is possible, in that the power output of the internal combustion engine by means of adjustable displacement hydraulic power unit is reacted. It should be noted, that the at least one displacement unit mechanically connected with the internal combustion engine at any time. Can be further provided, that the at least one displacement unit via a control slide the working hydraulic the mobile working machine, such as a stem cylinder, a bucket cylinder, an arm cylinder and a drive supplied. Typical applications would be for example mobile excavator, crawler excavator, mobile cranes and the like.

[0043] Is preferably use of hydraulic start-stop functionality in meeting the operating temperature of the drive system only use, i.e. as with car start-stop systems known, switching off of the primary drive to achieve the operating temperature only when the motor oil in particular take place. The operating temperature of the internal combustion engine in a mobile work machine concerns not only, but also the hydraulic oil.

[0044] The necessary for starting the internal combustion engine both for cold starting and high towing should always take place preferably in a hot starting the hydraulic system. So that the latter is possible, the shutdown of the internal combustion engine should only be as long as the hydraulic accumulator is fully charged and optionally to be delayed. There are two exceptions in, wherein the first and the second emergency stop detecting a detecting a leak of the pressure accumulator and the only existing hydraulic line for the memory operation.

[0045] Is not yet fully charged pressure accumulator a stopping the engine due to a suppressed, the disconnection of the engine should not only occur, when the accumulator is fully charged already, but the drive system on the basis of the rotating masses (flywheel, gears in the pump transfer case) be taken into account and the energy supplied to the accumulator portion removable therefrom, this further under continuing to load fuel consumption rather than permanently.

[0046] For determining rotational energy to the flywheel of the internal combustion engine serves the remaining existing or a separate speed sensor. To take account of the portion of the rotational energy, the accumulator can be supplied, the present hydraulic oil temperature in said accumulator and accumulator are measured and taken into account this pressure. These three variables are read in a controller. The time is determined taking into account the losses therefrom on the rotational energy for charging the accumulator is full enough. At this time the requested shutdown of the internal combustion engine is released. The map stored in the control device shall be calculated by a with the input parameters: speed, oil temperature, pressure level in the memory. Hence the energy, the standstill of the drive can be supplied to the memory. The characteristic curve is defined for each drive configuration by the results of functional tests.

[0047] Is also conceivable, that conventional starting device still as a back-up for "cold start" hot start and available.

[0048] The hydraulic stop-start system can further support the electric starter operation.

[0049]Atorque acting on the drive train by means of the displacement unit is especially advantageous, if the execution of the internal combustion engine based on at least on its diesel engine - as starting speed accelerated to its operating speed in the range of 1200 min and advantageously^-1 to 2200 min^-1 , preferably from 1400 min^-1 to 1900 min^-1 particularly preferably 1500 min^-1 to 1800 min^-1 .

[0050]Atorque acting on the drive train by means of a displacement unit the down internal combustion engine operating on their starting speed at least PES is thing mode can also be made. Based on the execution of the internal combustion engine is a diesel engine operating speed in the range of 1200 min^-1 to 1500 min^-1 preferably. In another lowering the speed would for converting mechanical in hydraulic power required a correspondingly large hydraulic pump configuration. This would be uneconomical.

[0051] Also there could be a torque acting on the drive train by means of the displacement unit under load already carry out, at least on their starting speed for an internal combustion engine to speed up.

[0052] Wherein the high displacement unit is used for towing of the internal combustion engine output torque proportional to the high pressure at quasi constant pivot angle of the swash plate axial piston machine almost.

[0053] Accumulator as a hydraulic accumulator can, in particular a bubble memory or a piston-type accumulator are used.

[0054] The maximum pressure level in the pressure reservoir is between 100 and 450 bars, preferably 150 of to 300 bar and particularly at 200 bars.

[0055] The accumulator can directly via a power take-off to the engine displacement unit coupled on fixed gear are loaded. The displacement unit on the primary side of the pressure accumulator charging can also transfer pumps are. The accumulator charging unit on the secondary side of the pump displacement can also transfer case are.

[0056] The accumulator charging displacement unit can be provided for charging of the pressure accumulator exclusively. The charging unit for charging the pressure reservoir and the pressure reservoir can displacement for operating auxiliary consumers be provided. In this case it is possible, that the respective displacement unit in a given time interval a) only charges the pressure reservoir, and b) the at least one secondary consumer is used only for operating or c) the accumulator and at least one secondary consumer supplied simultaneously.

[0057] The accumulator charging displacement unit can be provided for charging of the accumulator and for the operation of at least one main consumer, e.g. to the drive. In this case it is possible, that the respective displacement unit in a given time interval a) only charges the pressure reservoir, and b) at least one main is used only for operating the consumer or c) at least one pressure accumulator and the main consumer supplied simultaneously.

[0058] The accumulator charging unit for starting the internal combustion engine identical to the displacement can be high slow displacement unit. The accumulator charging displacement unit can be different than that displacement unit, when starting the internal combustion engine assumes the high towing thereof.

[0059] Delay-free starting of the engine torque demand by the driver or a working immediately after a request that requires high torque, the drive train to speed up in a short time. As a result of the proposed system is a hydraulic start process or the availability of a work function of mobile working machine faster than in today's electric starter systems.

[0060] It can also achieve a fuel economy by stopping the engine, when not required for use of primary power output functions. Primary function as translational movement of the mobile work machine and the actuation of the hydraulic work described. If necessary during the stop operation by the further auxiliary secondary functions such as to be met (e.g. the operation of the air conditioning, the lighting should preferably be fed from the conventional electrical system.

[0061] The invention making it possible to increase comfort and safety by temporary less noise on location during power off of the internal combustion engine.

[0062] The charging of the accumulator is also possible by recuperation power e.g. during braking.

[0063] Loading of the memory is also possible by raising a load point. This is the desired discharge power of the engine selected higher than the aware power required. With the "excess" power is charged the pressure accumulator.

[0064] Is also conceivable point lowering a load. The engine output is reduced then briefly. The required for supplying the consumer "power deficit" is removed from the accumulator.

[0065] The invention also makes possible an active for a brief power provided to the drive the boost increase. This can send out a protection from engine stall also are obtained.