CN218708945U - Industrial transportation vehicle and drive system thereof - Google Patents

Abstract

The present application discloses a drive system for an industrial handling vehicle, comprising: a motor; a plunger pump configured to provide hydraulic power to a walking device of the industrial handling vehicle, the plunger pump and the walking device being within a first hydraulic circuit; a gear pump configured to provide hydraulic power to a braking device and/or a steering device and/or handling equipment of the industrial handling vehicle, the gear pump, the braking device and/or the steering device and/or the handling equipment being within a second hydraulic circuit isolated from the first hydraulic circuit, the motor being in simultaneous operative connection with the plunger pump and the gear pump to drive the plunger pump and the gear pump in operation.

Description

Industrial transportation vehicle and drive system thereof

Technical Field

The present application relates generally to drive systems and methods for industrial handling vehicles, such as fork lift trucks.

Background

In industrial handling vehicles, such as fork lift trucks, the drive system typically employs hydraulic power to drive the traveling equipment of the industrial handling vehicle and the operation of the handling equipment. For this purpose, in industrial transport vehicles of this type, corresponding hydraulic actuating systems are associated with the running gear and the transport gear. Different motors are provided as drive sources for the hydraulic pumps in these hydraulic operation systems. These different electric machines must then be provided with respective electric control devices, thus causing the wiring of the electric control harnesses to be exceptionally complex in industrial handling vehicles.

In addition, the presence of a plurality of electric motors and electric control devices leads to a tendency to generate heat accumulation during the actual operation of the industrial handling vehicle, and since the industrial handling vehicle itself, such as a forklift truck, is small in size, it is not easy to ensure sufficient heat dissipation through a decentralized arrangement, and thus the electric motors and/or electric control devices are liable to cause overheat shutdown protection, thereby affecting the operational reliability of the industrial handling vehicle. In addition, the electromagnetic interference among different electric control devices also affects the working reliability, and in order to avoid the electromagnetic interference, an additional electromagnetic shielding component is often required to be added, so that the manufacturing cost of the whole vehicle is increased.

SUMMERY OF THE UTILITY MODEL

In view of the above problems, there is a need for an improved driving system, which can be used in an industrial transportation vehicle to drive the traveling equipment and the transportation equipment simultaneously, but can solve the heat dissipation problem and improve the operational reliability of the entire vehicle.

According to one aspect of the present application, there is provided a drive system for an industrial handling vehicle, comprising:

a motor is arranged on the base plate and is provided with a motor,

a plunger pump configured to provide hydraulic power to a walking device of the industrial handling vehicle, the plunger pump and the walking device being within a first hydraulic circuit;

a gear pump configured to provide hydraulic power to a braking device and/or a steering device and/or a handling apparatus of the industrial handling vehicle, the gear pump, the braking device and/or the steering device and/or the handling apparatus being within a second hydraulic circuit isolated from the first hydraulic circuit,

the motor is simultaneously operatively connected with the plunger pump and the gear pump to drive the plunger pump and the gear pump to operate.

Optionally, the motor is an ac synchronous motor and the gear pump is a dual gear pump.

Optionally, two ends of the rotating shaft of the motor are respectively coaxially and fixedly connected with the rotating shaft of the plunger pump and the rotating shaft of the gear pump.

Optionally, the plunger pump is a variable plunger pump, the walking device comprises a hydraulic motor, and in the first hydraulic circuit, the variable plunger pump and the hydraulic motor form a closed hydraulic subsystem.

Optionally, a fluid replacement pump is provided in the second hydraulic circuit, which fluid replacement pump is integrated in the plunger pump and is driven by the rotary shaft of the plunger pump, via which fluid replacement pump the hydraulic fluid circulating in the closed hydraulic subsystem is first pumped in the second hydraulic circuit from a second hydraulic fluid reservoir.

Optionally, a control valve is provided in the second hydraulic circuit, which control valve is located in the hydraulic line between the plunger pump and the fluid replacement pump, by means of which control valve the hydraulic fluid pumped by the fluid replacement pump is selectively returned to the second hydraulic fluid reservoir or fed to the plunger pump.

Optionally, a multi-way valve arrangement is provided in the first hydraulic circuit, via which the outlet of the gear pump is fluidly connected to the braking device and/or the steering device and/or the handling apparatus, in order to ensure that sufficient hydraulic fluid is always provided to the braking device and/or the steering device via the multi-way valve arrangement when the electric machine is running.

Optionally, within the first hydraulic circuit, the braking device, the steering device and the handling apparatus are each circulated to a first hydraulic fluid storage vessel via a separate hydraulic circuit.

Optionally, the electric machine is a variable speed electric machine and the hydraulic motor is a variable displacement hydraulic motor.

Optionally, a filter device is provided in the hydraulic fluid return line of the second hydraulic fluid storage vessel, and the second hydraulic fluid storage vessel and the first hydraulic fluid storage vessel are in fluid communication with each other.

According to another aspect of the present application, there is also provided an industrial handling vehicle comprising a walking device;

a braking device;

a steering device;

a handling device; and

the aforementioned drive system, said drive system configured to selectively provide hydraulic power to said walking apparatus, said braking device, said steering device, and said handling apparatus.

Optionally, the industrial handling vehicle is a forklift.

According to another aspect of the present application, there is also provided a control method for an industrial handling vehicle, wherein the work vehicle is provided with the aforementioned drive system, the method comprising:

in a case where the industrial transport vehicle is in a non-traveling state, before a transport facility of the industrial transport vehicle is operated, the motor of the drive system is caused to operate at least at a first predetermined rotational speed, which is a minimum rotational speed of a rotating shaft of the motor necessary for a brake device of the industrial transport vehicle to maintain a braking function thereof.

Optionally, before the industrial handling vehicle is expected to travel, operating the motor of the drive system at least at a second prescribed rotational speed, the second prescribed rotational speed being higher than the first prescribed rotational speed, and the second prescribed rotational speed being a minimum rotational speed of a rotating shaft of the motor necessary for the traveling apparatus of the industrial handling vehicle to maintain normal operation.

Alternatively, in a case where the industrial handling vehicle is in a running state, if an accelerator pedal of the industrial handling vehicle is depressed within a predetermined limit, the displacement of the hydraulic motor of the drive system is directly set to maximum and the displacement of the plunger pump of the drive system is adjusted from maximum to minimum or in a trend from maximum to minimum as the accelerator pedal is depressed.

Optionally, the predetermined limit is any percentage between 30% and 70% of the extent to which the accelerator pedal is depressed; and/or the first prescribed speed is between 700RPM and 2100RPM, the second prescribed speed is between 1500RPM and 2100 RPM.

Optionally, if the accelerator pedal of the industrial handling vehicle is depressed beyond the predetermined limit and the fluid pressure of the plunger pump is less than or equal to a predetermined first pressure threshold, the displacement of the plunger pump is set directly to maximum and the displacement of the hydraulic motor is adjusted from maximum to minimum or in a trend from maximum to minimum as the accelerator pedal is depressed.

Optionally, if an accelerator pedal of the industrial handling vehicle is depressed beyond the predetermined limit and the fluid pressure of the plunger pump is greater than a predetermined first pressure threshold, the displacement of the plunger pump is adjusted from maximum to minimum or in a trend from maximum to minimum as the accelerator pedal is depressed and the displacement of the hydraulic motor is adjusted from minimum to maximum or in a trend from minimum to maximum as the accelerator pedal is depressed.

Optionally, if an accelerator pedal of the industrial handling vehicle is depressed beyond the predetermined limit and the fluid pressure of the plunger pump is greater than a predetermined second pressure threshold, the displacement of the plunger pump is adjusted from minimum to maximum or in a trend from minimum to maximum as the accelerator pedal is depressed and the displacement of the hydraulic motor is adjusted from maximum to minimum or in a trend from maximum to minimum as the accelerator pedal is depressed, wherein the predetermined second pressure threshold is less than the predetermined first pressure threshold.

Optionally, the predetermined first pressure threshold is 24Mpa.

Optionally, the predetermined first pressure threshold is 24Mpa and the predetermined second pressure threshold is 20Mpa.

Optionally, the industrial handling vehicle is a forklift. By adopting the technical means, the operation of the driving system on the walking equipment and the carrying equipment of the industrial carrying vehicle can be simultaneously met by utilizing a single motor, the wiring difficulty of the electric control wire harness is obviously simplified, the possible heating points of the industrial carrying vehicle are reduced, the driving system is easily dispersed and arranged, the heat dissipation is improved, the electromagnetic interference generated by the electric control device is reduced, and the working reliability of the industrial carrying vehicle is improved. In addition, the drive system of the present application is easily upgradeable in existing industrial handling vehicles. In addition, the single motor effectively reduces the manufacturing cost of the whole vehicle.

In addition, adopt the fork truck of the technical means design or transformation of this application, can ensure fork truck at the in-process safe and reliable of operation. This is because the prior art uses a drive system with a plurality of low power motors, which therefore need to be overpowered for a short period of time when an industrial handling vehicle, such as a forklift truck, is performing a handling operation requiring a large load. This would significantly reduce the operational reliability of the industrial handling vehicle from a long-term operational perspective. However, the driving system of the application adopts a single motor with larger power, so that when the same carrying operation with larger load requirement is completed, the driving motor of the application does not need to be operated in an overpower mode, even can be operated in a low-power mode aiming at the carrying operation with the same load requirement, and therefore, the long-term reliability of the running of the whole vehicle is greatly increased.

Drawings

The principles and aspects of the present application will be more fully understood from the following detailed description, taken in conjunction with the accompanying drawings. It is noted that the drawings may not be to scale for clarity of illustration and will not detract from the understanding of the present application. In the drawings:

FIG. 1 schematically illustrates a block diagram of a drive system for an industrial handling vehicle according to one embodiment of the present application;

fig. 2 schematically shows an external view of a part of a drive system according to an embodiment of the present application;

FIG. 3 schematically illustrates an overall hydraulic circuit diagram of a drive system according to an embodiment of the present application;

FIG. 4A schematically illustrates a hydraulic circuit diagram of a portion of the drive system of FIG. 3;

FIG. 4B schematically illustrates a hydraulic circuit diagram of another portion of the drive system of FIG. 3;

FIG. 5 schematically illustrates an example of a control method for an industrial handling vehicle according to one embodiment of the present application; and

fig. 6 schematically shows a sub-process in the control method of fig. 5.

Detailed Description

In the various figures of the present application, features that are structurally identical or functionally similar are denoted by the same reference numerals.

FIG. 1 shows a schematic block diagram of a drive system 100 for an industrial handling vehicle according to one embodiment of the present application. Although in the context of the present application, the industrial handling vehicle is primarily described in the context of a forklift truck, it should be clear to a person skilled in the art that the drive system 100 of the present application can be applied in other similar industrial vehicles having a running gear and a handling gear or similar handling gear than a forklift truck.

As shown, the drive system 100 includes a single motor 200. For example, the single motor may be an ac synchronous motor. In a preferred embodiment, the motor 200 may be an AC variable speed synchronous motor. The drive system 100 further includes a plunger pump 300 and a gear pump 400. According to a preferred embodiment, the plunger pump 300 is in particular a closed circuit variable plunger pump, and the gear pump 400 is a double gear pump. The motor 200 is operatively connected to the plunger pump 300 and the gear pump 400. In the context of the present application, the operative connection of the motor 200 with the plunger pump 300 and the gear pump 400 means that rotation of the rotational shaft of the motor 200 can simultaneously drive the plunger pump 300 and the gear pump 400 to operate. In one example, for example, both ends of the rotation shaft of the motor 200 are fixedly connected to the rotation shaft of the plunger pump 300 and the rotation shaft of the gear pump 400, respectively, so that the rotation of the rotation shaft of the motor 200 can operate the plunger pump 300 and the gear pump 400 at the same time. The shaft-shaft fastening can be effected here, for example, by threading the two concentric rotary shafts to be fastened via suitable bushings and then threading screws transverse to the axis of rotation between the bushings and the respective rotary shafts. Of course, it should be clear to a person skilled in the art that any mechanical fixing means by which two shafts can be fixed concentrically so that they can rotate about the same axis of rotation between them can be used in the solution of the present application. According to the technical scheme of the application, the design that the plunger pump 300 and the gear pump 400 are synchronously driven by two ends of the rotating shaft of the motor 200 is utilized, so that the layout design of internal parts of the whole vehicle is simplified.

In addition, the drive system 100 also includes a running gear 500, the running gear 500 being hydraulically powered by the plunger pump 300 to propel an industrial handling vehicle, such as a forklift. The drive system 100 further comprises a handling apparatus 700, which handling apparatus 700 is hydraulically powered by the gear pump 400 to effect relevant handling operations of the forklift such as lifting, tipping, adjustment of the fork arms, etc. In addition, the drive system 100 includes a braking device 600 and a steering device 800 for the industrial handling vehicle, which are also provided with hydraulic power by the gear pump 400 for performing respective braking and steering actions of the vehicle. The plunger pump 300 is in fluid communication with a plunger pump hydraulic fluid storage vessel 310 and the gear pump 400 is in fluid communication with a gear pump hydraulic fluid storage vessel 410. Although the hydraulic fluid storage container 310 for the plunger pump and the hydraulic fluid storage container 410 for the gear pump may store the same hydraulic fluid, the hydraulic fluid storage container 310 for the plunger pump and the hydraulic fluid storage container 410 for the gear pump are isolated from each other. That is, the hydraulic circuits in which the plunger pump 300 and the traveling apparatus 500 are located and the gear pump 400 and the hydraulic circuits in which the brake device 600, the steering device 800, and the carrying apparatus 700 are located are isolated from each other.

Since the fluctuation of the hydraulic output of the plunger pump 300 is smoother with respect to the gear pump 400, it is more suitable for the driving of the walking device 500. Further, during the operation of the handling apparatus 700, the brake device 600, and the steering device 800 of the industrial handling vehicle, it is difficult to avoid that the quality of the hydraulic fluid is affected due to impurities entrained in the hydraulic fluid due to the respective action elements being exposed during the operation. The gear pump 400 requires less hydraulic fluid quality during operation than the plunger pump 300 and is therefore more suitable for providing hydraulic power to the handling apparatus 700, the brake device 600, and the steering device 800.

In an alternative embodiment, a filter device may also be provided in the hydraulic fluid return line of the gear pump hydraulic fluid reservoir 410 to filter out impurities in the returned hydraulic fluid, so that in this case the plunger pump hydraulic fluid reservoir 310 and the gear pump hydraulic fluid reservoir 410 may be in fluid communication with each other.

In addition, the drive system 100 further includes an electronic control device 210, which is configured to support the operation of the motor 200, for example, and includes a controller, a motor driver, a feedback sensor, and the like. Since the drive system 100 of the present application employs only a single motor 200, the electrical control device 210 of the motor 200 can be conveniently wired within the forklift as desired. Compared with the prior art, the method omits fussy wiring design, saves wiring wires and can obviously save the manufacturing cost of the forklift. Meanwhile, due to the adoption of a single motor, the distribution of radiating points can be reduced, and the radiating effect in the running process of the whole vehicle is correspondingly improved.

The drive system 100 further comprises a control unit 10, which may for example comprise a computer and a memory in which a computer program is stored that can be called up to be executed by the computer. The control unit 10 can be connected to the electronic control device 210, the controller of the plunger pump 300, the corresponding components in the hydraulic circuit in which the traveling apparatus 500 is located, the controller of the gear pump 400, and the corresponding components in the hydraulic circuit in which the braking device 600, the steering device 800, and the handling apparatus 700 are located, so as to control them according to the stored computer programs. For example, the control unit 10 may be designed to adjust the rotational shaft operating speed of the motor 200, the displacement of the plunger pump 300, the displacement of a hydraulic motor (described below), and the like accordingly.

Fig. 2 schematically shows an external view of a part of the drive system 100 according to an embodiment of the present application. As can be seen from the figure, the rotating shaft of the motor 200 (hidden by the end cap) is designed to be coupled at both ends to the rotating shafts of the gear pump 400 and the plunger pump 300, respectively. Therefore, when the motor 200 is operated, the gear pump 400 and the plunger pump 300 are simultaneously operated. Further, the gear pump 400 is fluidly connected to a multi-way hydraulic valve device 900 via hydraulic lines, and the hydraulic fluid pressurized and supplied by the gear pump 400 can selectively drive and operate the brake device 600, the steering device 800, and the carrying apparatus 700 via the multi-way hydraulic valve device 900. For example, the braking of the forklift is controlled by the brake valve device 610 of the brake device 600, the brake valve device 610 is fluidly connected downstream of the multiplex valve device 900, and when braking is required, a user may press a brake pedal to operate the brake valve device 610, so that hydraulic power-assisted braking is achieved. In addition, the plunger pump 300 is fluidly connected to a hydraulic motor 510 via hydraulic lines. The hydraulic motor 510 is operatively connected to the wheels of the industrial handling vehicle, for example as part of the running gear 500, to power the rotation of the wheels to propel the engineering handling vehicle. In the preferred embodiment, the hydraulic motor 510 is a variable displacement hydraulic motor.

Fig. 3 schematically shows an example of a simplified hydraulic circuit diagram of a drive system 100 according to the present application. FIG. 4A schematically illustrates an example of a portion of the hydraulic circuit diagram in FIG. 3. It should be clear to a person skilled in the art that the hydraulic circuit diagram/example shown in the figures is only intended as an illustrative and non-limiting illustration of the solution of the present application. Other arrangements of hydraulic circuits that enable operation of the drive system 100 of the present application may also be employed in the subject application.

The two inputs of the double gear pump 400 are connected to a hydraulic fluid reservoir 410 via hydraulic lines in series with filters. The multi-way hydraulic valve arrangement 900 is provided with two input ports P1 and P2, and a plurality of output ports. Inside the multi-way hydraulic valve arrangement 900, a plurality of hydraulic switching valves, e.g. valves 910, 920, 930, 940, 950, etc., are arranged between the input ports P1, P2 and the respective output ports. The valve 950 is configured to communicate with the input port P1, and the valve 950 is a priority valve, in particular, a two-position three-way priority valve. The priority valve is configured to provide priority to hydraulic fluid to the brake valve assembly 610 and the steering gear assembly 810 without the need for electrical control. For example, the priority valve 950 is configured to be fluidly connected to the brake valve arrangement 610 capable of acting on the brake arrangement 600 of the industrial handling vehicle and the steering assembly 810 capable of acting on the steering arrangement 800 of the industrial handling vehicle, respectively, via the output ports CF and Ls of the multi-way hydraulic valve arrangement 900. In the context of the present application, a fluid connection between two features means that the two features are connected to each other in a way that enables the transfer of fluid, for example via a fluid line. Since braking and steering are the most preferred operational requirements during travel of the industrial handling vehicle, the priority valve 950 is configured such that whichever gear input port P1 it is in communication with the hydraulic fluid input ports of the brake valve device 610 and the steering gear assembly 810, so that when the dual gear pump 400 is operated by the motor 200, there will always be a sufficient flow of hydraulic fluid provided to the brake valve device 610 and the steering gear assembly 810 via the multiplex hydraulic valve device 900 to ensure reliable operation of the brake device 600 and the steering gear assembly 810 of the industrial handling vehicle.

In addition, the other valves 910, 920, 930, 940 disposed in multi-way hydraulic valve arrangement 900 may be manual valves to facilitate manual operation by a user of the industrial handling vehicle as desired. For example, in the example shown, these manual valves may be three-position, eight-way valves configured in parallel with input port P2 of multi-way hydraulic valve arrangement 900. For example, as shown, these manual valves 910, 920, 930, 940 may be respectively fluidly connected to a lift cylinder module 710, a tilt cylinder module 720, and a pitch cylinder module 730 as part of the handling apparatus 700, which may be used to effect lifting, tilting, and pitching of the mast of a forklift, respectively, for example. The multiplex hydraulic valve arrangement 900 is configured to be capable of selectively supplying hydraulic fluid to the brake valve arrangement 610 and the steering gear assembly 810 via an input port P1, and selectively supplying hydraulic fluid to the lift cylinder module 710, the tilt cylinder module 720 and the pitch cylinder module 730 via an input port P2, the supply of hydraulic fluid being independent of each other.

These manual valves 910, 920, 930, 940 are configured such that when they are each positioned in the neutral position of the valve, hydraulic fluid is supplied from the input port P2 to the multi-way hydraulic valve arrangement 900 through the gear pump 400, and then discharged through the output port T1 of the multi-way hydraulic valve arrangement 900 to be returned to the hydraulic fluid storage tank 410 through the hydraulic fluid radiator 1010. At this time, the handling apparatus 700 is in an idle state, i.e., the modules are not operated, for the lift cylinder module 710, the tilt cylinder module 720, and the distance cylinder module 730, since no hydraulic fluid is supplied.

Taking the manual valve 910 as an example only, if the manual valve 910 is operated to the down position as shown in the figure with the manual valves 920, 930, 940 still in the neutral position, the hydraulic path from the input port P2 to the point A1 is conducted, and at this time, the hydraulic fluid supplied through the gear pump 400 can be delivered to the lift cylinder module 710 through the conducted hydraulic path, so that, for example, the lift of the forklift mast can be achieved, which corresponds to the "+" position in column A1 in table 1, for example. When the manual valve 910 is operated in the up position as shown and the manual valves 920, 930, 940 are still in the neutral position, then the hydraulic path from the B1 point to the hydraulic fluid radiator 1010 is open and the lift cylinder module 710 may effect the lowering of the forklift mast, which corresponds to the "+" position in column B1 in table 1, for example. By analogy, table 1 schematically illustrates the corresponding operation of the handling device 700 that can be achieved via the multi-way hydraulic valve arrangement 900 when the gear pump 400 is operating.

TABLE 1 corresponding operating/Hydraulic Path of a handling device realized by means of a Multi-way Hydraulic valve arrangement

As shown in fig. 3, in the embodiment of the present application, it is preferable to use a plunger pump 300, in particular, a closed-circuit bidirectional variable plunger pump 300, and a hydraulic motor 510 as a part of the traveling apparatus 500 to form a closed hydraulic subsystem, that is, a liquid inlet and a liquid outlet of the variable plunger pump 300 are connected to a liquid inlet and a liquid outlet of the hydraulic motor 510 via hydraulic lines. The closed circuit variable displacement piston pump 300 is well suited for driving the hydraulic motor 510 in the solution of the present application, since it is provided with special actuating elements to regulate the flow rate of the pump (e.g. from zero to maximum) and/or the direction of the hydraulic fluid pumped. An output shaft of the hydraulic motor 510 is operatively connectable to the wheels to drive the wheels in rotation. Depending on the direction of the hydraulic fluid, the fluid inlet and outlet ports of the variable displacement piston pump 300 and the hydraulic motor 510 may be changed to a fluid inlet port and a fluid outlet port, respectively, or vice versa.

Fig. 4B schematically illustrates an example of another portion of the hydraulic circuit in fig. 3 including the variable displacement piston pump 300. As shown, to avoid hydraulic fluid leakage in the closed hydraulic subsystem, resulting in reduced operating efficiency, the variable displacement plunger pump 300 is provided with a fluid replacement pump 320. The fluid replacement pump 320 may be integrated with the variable displacement plunger pump 300 and share a rotation shaft of the variable displacement plunger pump 300. The hydraulic fluid reservoir 310 is connected via a hydraulic line to an inlet of the substitution pump 320, and an outlet of the substitution pump 320 is fluidly connected via a hydraulic line to the variable displacement piston pump 300. Meanwhile, the liquid inlet and outlet of the variable displacement plunger pump 300 and the liquid inlet and outlet of the hydraulic motor 510 are fluidly connected via hydraulic lines, respectively. A control valve 330, for example, an electromagnetic control valve, is provided in the hydraulic line between the replenishment pump 320 and the variable displacement plunger pump 300. The regulating valve 330 can be actuated accordingly under the command of the control unit 10. The regulator valve 330 is a three-position, four-way valve. The regulator valve 330 may be commanded to the left or right position as shown, depending on the direction of hydraulic fluid delivered by the variable displacement piston pump 300. For example, in this example, when the regulator valve 330 is commanded to the right as shown, the variable displacement piston pump 300 is operated such that hydraulic fluid is first drawn from the hydraulic fluid reservoir 310 via the make-up pump 320 and then fed to the variable displacement piston pump 300, pressurized and discharged to the hydraulic motor 510, driving its operation. At the same time, the variable displacement pump 300 may adjust its output displacement, for example, from zero to a nominal maximum output displacement, to adjust the hydraulic motor 510 action as needed.

While the motor 200 is operating, it may sometimes be necessary to stop the industrial truck from traveling, if desired, but to operate the handling apparatus 700 at the same time. In this regard, in the illustrated example, the regulator valve 330 may be switched to the neutral position as shown, such that while the motor 200 is running, the variable displacement plunger pump 300 and the make-up pump 320 may be in communication with point L at the same time due to the housing design of the variable displacement plunger pump 300 itself, such that hydraulic fluid may be correspondingly returned from point L to the hydraulic fluid reservoir 310 via the hydraulic line and then the hydraulic fluid radiator 1020.

The combination of the hydraulic circuit portions as shown in fig. 4A and 4B can ensure that any one of the traveling apparatus 500, the carrying apparatus 700, the brake device 600, and the steering device 800 can be switched between the non-operating state and the operating state as needed during the operation of the motor 200. Thus, although the present application employs a single motor 200 to drive both the variable displacement piston pump 300 and the gear pump 400, the various functions of the industrial handling vehicle are not affected at all.

Taking a 10-ton forklift as an example, if the forklift is designed by adopting the prior art scheme, under the condition that the hydraulic circuit still adopts the scheme shown in fig. 3, the inventor calculates that a 35 kilowatt motor and a frequency converter for walking equipment are needed to be adopted, and two 26 kilowatt motors for carrying the equipment are needed to be adopted; in contrast, if the forklift is designed by the technical scheme of the application, only a single 75 kilowatt motor is needed. Compared with the prior art, the design scheme of the application not only enables the whole vehicle to obviously reduce weight, but also reduces wiring length and difficulty, reduces heating points when the whole vehicle works, is beneficial to the heat dissipation design of the whole vehicle, and can obviously reduce the manufacturing cost of the whole vehicle.

Although a double gear pump is used in the described examples or embodiments, it should be clear to those skilled in the art that the solution of the present application can also use a single gear pump design to provide hydraulic power to the braking device 600, the steering device 800, and the handling device 700. When the design of a single gear pump is adopted, the multi-path hydraulic valve device needs to be redesigned, so that the multi-path hydraulic valve device only has one hydraulic fluid input port; in addition, in the multi-path hydraulic valve device, the hydraulic power input through the input port can be independently transmitted to the brake device 600, the steering device 800 and the carrying device 700 as required by the design of the hydraulic circuit. The specific design is preferably any that can be implemented by a person skilled in the art.

In the example shown in fig. 4B, a closed hydraulic subsystem is formed by the variable displacement piston pump 300 and the hydraulic motor 510. It will be apparent to those skilled in the art that other forms of plunger pump and hydraulic motor 510 may be used in alternative embodiments to form an open hydraulic subsystem. In such a case, it will be clear to those skilled in the art that the hydraulic circuit portion shown in fig. 4B needs to be redesigned so that actuation of the hydraulic actuators ensures that the pump remains inoperative while the motor is running (i.e., although hydraulic fluid may still be drawn from the hydraulic fluid reservoir 310, the drawn hydraulic fluid is returned directly to the hydraulic fluid reservoir 310 via dedicated hydraulic lines.

Fig. 5 shows an example of a method of drive control of an industrial handling vehicle such as a forklift for the drive system of the present application. It will be clear to a person skilled in the art that the relevant control methods/procedures/sub-procedures may be stored as computer programs in the memory of the drive system 100 and invoked for execution by the control unit 10 as required. Further, while the control method of the present application is described below in the context of a forklift, it should be clear to one skilled in the art that the control method shown in FIG. 5 may be applied to the drive system and other suitable industrial handling vehicles involved in any of the embodiments and/or preferences and/or alternatives described above in the present application.

As shown in fig. 5, in step S10, the forklift performs a related self-test and/or preparation work before work. Then, in step S20, it is detected whether or not the forklift is in the parking state. In the context of the present application, "parked state" means that the hand brake of an industrial handling vehicle, such as a forklift, has been operated (e.g. pulled up), so that the industrial handling vehicle is rendered incapable of travelling. This can be determined, for example, by a sensor that detects the hand brake state of the forklift. The purpose of this step S20 is mainly to determine whether the forklift is currently in a stationary state. The parked state may be a precondition for the industrial transport vehicle to perform the relevant transport operation. Of course, it should be clear to those skilled in the art that the industrial handling vehicle may perform a handling operation with the precondition that it is not just a parked state. If the determination result at step S20 is yes (Y), it may go to step S70, otherwise (N) may go to step S30.

According to the example of the control method of the present application, if it has been determined that the forklift is in the parking state and a corresponding carrying operation with the forklift is still required (e.g., the operation of the mast and/or the fork arms, etc.), the motor 200 of the drive system 100 is regulated at step S70 such that the rotation speed of the rotation shaft of the motor 200 is substantially maintained at a first prescribed rotation speed. The first predetermined rotation speed is the minimum rotation speed of the rotation shaft of the motor 200 necessary for the forklift brake device 600 to maintain its basic braking function. For example, the first prescribed rotational speed may be 700 RPM. The reason for the first prescribed rotational speed is because the motor of the drive system of the present application simultaneously drives the gear pump and the plunger pump, wherein the gear pump supplies hydraulic power to the brake device 600, the steering device 800, and the handling apparatus 700 of the forklift. In the case where the motor 200 is operated, the forklift already in the parked state must ensure that the brake device 600 can operate normally in order to brake reliably. Thus, in the parking state of the forklift, the hydraulic power necessary for braking the entire vehicle to the brake device 600 should be maintained even if any carrying operation has not been performed — the motor 200 is maintained to operate at the first prescribed rotation speed.

Then, in step S80, the motor 200 may be commanded to adjust its speed according to the user' S corresponding input device on the forklift, such as the operating handle, etc., so as to correspondingly increase or decrease the displacement of the supplied hydraulic fluid, for example, so that the rotation axis of the motor 200 is changed between 700RPM and 2100RPM as desired. At the same time, the user may cause the manual valves 910, 920, 930, 940 to change states accordingly to accomplish the desired handling operation (see table 1).

In step S30, it is determined whether the forklift is performing a traveling operation. In the context of the present application, in addition to carrying out a carrying operation in a parked state, an industrial carrying vehicle such as a forklift may also carry out a carrying operation as long as it is in a state of not walking. This may be achieved, for example, by detecting relevant gear signals in the cab of the truck, such as monitoring whether a forward gear of the truck is engaged, etc. Alternatively, the determination may be made based on detection signals from respective sensors attached to the forklift. For example, whether or not the forklift is in a non-traveling state is determined by signals related to an acceleration sensor, a brake sensor, and the like of the forklift. In addition, it is also possible to monitor whether the accelerator pedal in the cab of the forklift is pressed. If the forward gear of the forklift is engaged and the accelerator pedal is pressed at the same time, it is regarded that the forklift is about to perform a walking operation. According to the control method of the present application, the priority of the traveling operation of the forklift is higher than the priority of the carrying operation of the forklift. For example, if the displacement of the plunger pump is adjusted to zero, the hydraulic motor will not work due to the self-locking characteristic of the closed hydraulic subsystem, and the forklift truck will be in a state of being unable to walk at the moment.

Therefore, if the determination result of step S30 is yes, the flow goes to step S40. In step S40, the motor 200 of the drive system 100 is adjusted such that the rotational speed of the rotating shaft of the motor 200 is substantially maintained at a second predetermined rotational speed, which is higher than the first predetermined rotational speed. The second predetermined rotation speed is the minimum rotation speed of the rotation shaft of the motor 200 necessary for the traveling device 500 of the forklift to maintain a normal operation. For example, the second prescribed speed may be 1500RPM. Since the second predetermined rotational speed is higher than the first predetermined rotational speed, it is possible to ensure normal operation of both the braking device and the traveling apparatus when the motor 200 is operated at the second predetermined rotational speed.

Then, in step S50, the rotation speed of the motor, the steering device, and the like may be controlled and operated according to the corresponding walking operation of the user in the cab of the forklift, such as acceleration, steering, and the like.

If the judgment result of the step S30 is no, the process goes to the steps S70 and S80, so that the user can carry out the carrying operation of the carrying apparatus accordingly.

According to the drive system of the present application, the displacement of the plunger pump and/or the displacement of the hydraulic motor and/or the rotational speed of the electric machine may be adjusted separately or simultaneously as desired. Especially for the traveling operation of the forklift, for example, when ascending a slope or climbing an obstacle, the user excessively steps on the accelerator pedal to increase the rotation speed of the rotation shaft of the motor 200 does not necessarily lead to the power output of the hydraulic motor being optimized. Fig. 6 thus schematically shows an example that can be employed in a respective walking operation (e.g. at step S50) as a sub-process of the control method.

In step S510, it is determined whether the accelerator pedal is pressed within a predetermined limit. For example, the predetermined limit may be set to 70%, 60%, 50%, 40%, 30%, or any percentage between 30% and 70% of the maximum extent to which the accelerator pedal is depressed.

If the accelerator pedal is judged to be pressed within the predetermined limit (i.e., the judgment result of step S510 is yes), it is considered that there is a speed increase demand for normal traveling of the forklift at this time. Therefore, go to step S520. In step S520, the displacement of the hydraulic motor 510 is directly set to maximum. Then, in step S530, the displacement of the plunger pump 300 may be adjusted from the maximum to the minimum or according to this trend according to the degree of pressing the accelerator pedal by the user, so as to ensure that the displacement change relationship of the plunger pump 300 and the hydraulic motor 510 corresponds to the actual demand of the user.

If the accelerator pedal is judged to have been depressed equal to or beyond the predetermined limit (i.e., no in step S510), then it is considered that there is (1) a demand for acceleration for normal travel or (2) a need to climb a slope or climb over an obstacle. Since the two requirements (1) and (2) are completely different from the control requirements of the plunger pump and the hydraulic motor, the former needs to increase the rotation speed of the hydraulic motor, and the latter needs to increase the torque of the hydraulic motor. When the forklift needs to climb or turn over an obstacle, the rotation speed of the motor 200 is correspondingly increased along with the pressing of the accelerator pedal by the user. At the same time, if the truck is not traveling, the fluid pressure at the plunger pump 300 (or simply, the fluid pressure of the plunger pump) will rise accordingly. For example, data (e.g., fluid pressure) relating to the plunger pump 300 may be detected and transmitted to the control unit 10 in real time.

Therefore, a first pressure threshold may be set for the plunger pump 300 in advance. If the measured value of the fluid pressure at the plunger pump 300 is greater than the first pressure threshold value, it is considered that the torque of the traveling device is mainly increased for the travel of the forklift at this time. For example, the first pressure threshold may be 24Mpa or any other suitable value, which may be pre-factory set or post-modified by the forklift.

Therefore, in step S540, it is determined whether the current fluid pressure of the plunger pump 300 exceeds the first pressure threshold. If the result of the determination in step S540 is negative, it is considered that the current travel control request of the forklift mainly increases the rotation speed of the hydraulic motor. Thus, at step S580, the displacement of the plunger pump 300 is directly set to minimum. In step S590, the displacement of the hydraulic motor 510 is adjusted from maximum to minimum or according to this trend, depending on the degree to which the user presses the accelerator pedal, thereby ensuring that the displacement change relationship of the plunger pump 300 and the hydraulic motor 510 corresponds to the demand of the forklift control.

If the determination result in step S540 is yes, it is considered that the current travel control request of the forklift mainly increases the torque of the traveling device. In step S550, the displacements of the plunger pump 300 and the hydraulic motor 510 may be adjusted simultaneously or sequentially according to the degree of pressing the accelerator pedal by the user, such that the displacement of the plunger pump 300 is adjusted from maximum to minimum or according to this trend, and the displacement of the hydraulic motor 510 is adjusted from minimum to maximum or according to this trend. This ensures that the running gear operates predominantly in a manner that increases the torque.

Then, it is determined at step S560 whether the current fluid pressure of the plunger pump 300 is less than a second pressure threshold that is slightly less than the first pressure threshold to achieve the setting. For example, the second pressure threshold may be 20MPa or other suitable value less than the first pressure threshold. The purpose of the second pressure threshold value setting is to judge whether the operation mode of increasing the torque output of the walking equipment is still mainly used for judging whether the forklift moves; while avoiding changing the operating tendency of the truck too frequently (e.g., frequently switching between predominating at increasing hydraulic motor speed output and predominating at increasing traction device torque output). If the result of the determination at step S560 is no, it goes to step S550. If the result of the determination in the step S560 is yes, it is determined that the current operation demand of the forklift is mainly based on increasing the torque output of the traveling apparatus, and is mainly based on increasing the rotational speed output of the hydraulic motor. Therefore, as the user presses the accelerator pedal, the displacements of the plunger pump 300 and the hydraulic motor 510 may be adjusted simultaneously or sequentially, such that the displacement of the plunger pump 300 is adjusted from minimum to maximum or according to this trend, and the displacement of the hydraulic motor 510 is adjusted from maximum to minimum or according to this trend, at step S570. This ensures that the running gear operates predominantly in such a way that the rotational speed can be increased.

By adopting the control method, the operation safety of the forklift in the parking state can be ensured, and in addition, the operation of an accelerator pedal of the forklift in the walking state also meets the actual requirements of a user on speed and torque.

Although specific embodiments of the present application have been described herein in detail, they have been presented for purposes of illustration only and are not to be construed as limiting the scope of the application. Further, it should be clear to those skilled in the art that the various embodiments described in this specification can be used in combination with each other. Various substitutions, alterations, and modifications may be conceived without departing from the spirit and scope of the present application.

Claims (12)

1. A drive system for an industrial handling vehicle, comprising:

a motor (200) is arranged on the base,

a plunger pump (300) configured to provide hydraulic power to a walking device (500) of the industrial handling vehicle, the plunger pump (300) and the walking device (500) being within a first hydraulic circuit;

a gear pump (400) configured to provide hydraulic power to a braking device (600) and/or a steering device (800) and/or a handling apparatus (700) of the industrial handling vehicle, the gear pump (400), the braking device (600) and/or the steering device (800) and/or the handling apparatus (700) being within a second hydraulic circuit isolated from the first hydraulic circuit, characterized in that,

the motor (200) is simultaneously and operatively connected with the plunger pump (300) and the gear pump (400) to drive the plunger pump (300) and the gear pump (400) to operate.

2. The drive system of claim 1, wherein the motor (200) is an ac synchronous motor and the gear pump (400) is a dual gear pump.

3. The drive system according to claim 2, wherein both ends of the rotary shaft of the motor (200) are coaxially and fixedly connected to the rotary shaft of the plunger pump (300) and the rotary shaft of the gear pump (400), respectively.

4. A drive system according to claim 3, characterized in that the piston pump (300) is a variable piston pump and the walking device (500) comprises a hydraulic motor (510), and in the first hydraulic circuit the variable piston pump and the hydraulic motor (510) form a closed hydraulic subsystem.

5. The drive system according to claim 4, characterized in that a fluid replacement pump (320) is provided in the second hydraulic circuit, the fluid replacement pump (320) being integrated in the plunger pump (300) and being driven by the rotational shaft of the plunger pump (300), the hydraulic fluid circulating in the closed hydraulic subsystem being first pumped in the second hydraulic circuit by a second hydraulic fluid storage container (310) via the fluid replacement pump (320).

6. The drive system according to claim 5, characterized in that a regulating valve (330) is provided in the second hydraulic circuit, the regulating valve (330) being in the hydraulic line between the plunger pump (300) and the make-up pump (320), by means of which regulating valve (330) the hydraulic fluid pumped by the make-up pump (320) is selectively returned to the second hydraulic-fluid storage container (310) or delivered to the plunger pump (300).

7. The drive system according to claim 6, characterized in that a multiplex valve device (900) is provided in the first hydraulic circuit, via which multiplex valve device (900) the outlet opening of the gear pump (400) is fluidly connected with the brake device (600) and/or the steering device (800) and/or the handling apparatus (700), in order to ensure that sufficient hydraulic fluid is always provided to the brake device (600) and/or the steering device (800) via the multiplex valve device (900) when the electric motor (200) is running.

8. A drive system according to claim 7, characterized in that in the first hydraulic circuit the braking device (600), the steering device (800) and the handling apparatus (700) each communicate via a separate hydraulic circuit to a first hydraulic fluid storage container (410).

9. The drive system of any of claims 4 to 8, wherein the electric machine is a variable speed electric machine and the hydraulic motor (510) is a variable displacement hydraulic motor.

10. The drive system of claim 8, wherein a filter device is provided in the hydraulic fluid return line of the second hydraulic fluid reservoir (310), and the second hydraulic fluid reservoir (310) and the first hydraulic fluid reservoir (410) are in fluid communication with each other.

11. An industrial handling vehicle comprising

A walking device (500);

a braking device (600);

a steering device (800); and

a handling device (700);

characterized in that it further comprises a drive system according to any one of claims 1 to 10, configured to selectively provide hydraulic power to said walking device (500), said braking means (600), said steering means (800) and said handling device (700).

12. The industrial handling vehicle of claim 11, wherein the industrial handling vehicle is a forklift.

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