Industrial Vehicles

Abstract

To provide an industrial vehicle which can achieve downsizing of electric motors for traveling and cargo handling while inhibiting shortages of maximum output performance for traveling and cargo handling.SOLUTION: A forklift includes: a cargo handling motor 31 which drives a cargo handling device; and a driving motor 41 which drives driving wheels 10T. The forklift further includes: a cargo handling output path 34 formed between the cargo handling motor 31 and a cargo handling oil pump 32; a traveling output path 44 formed between the driving motor 41 and the driving wheels 10T; an assist motor 51 for assisting the cargo handling motor 31 or the traveling motor 41; assist power paths 57 formed between the assist motor 51 and the cargo handling output path 34 and between the assist motor 51 and the traveling output path 44; and a cargo handling assist switching part 52 and a traveling assist switching part 53 which switch whether power from the assist motor 51 is transmitted to one of the oil pump 32 and the driving wheels 10T through the assist power path 57.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an industrial vehicle. [Background technology]

[0002] Conventionally, as a technology related to industrial vehicles, for example, the technology described in Patent Document 1 is known. Patent Document 1 discloses a battery forklift equipped with a traveling motor for driving the drive wheels and a loading motor provided in an electric hydraulic system device for raising and lowering the forks. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-79637 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, for example, in the technical field of automobiles, electric vehicles that run only on electric motors without an internal combustion engine have been popularized from the viewpoint of environmental protection. Such replacement of internal combustion engines with electric motors is also being considered for application in the technical field of industrial vehicles such as forklifts. However, in industrial vehicles such as forklifts, the output characteristics of the drive sources required for driving and loading are different, while the output characteristics of the internal combustion engine and the electric motor are different. Therefore, simply replacing one internal combustion engine with one electric motor is likely to lead to an increase in size of the electric motor in order to obtain the same performance as the internal combustion engine for driving and loading, and is likely to be inefficient.

[0005] Under these circumstances, it is conceivable to provide a configuration in which one electric motor is provided for each of driving and loading and unloading, as in the above-mentioned conventional technology. However, in such a configuration, in order to obtain the same output performance as a conventional internal combustion engine for both driving and unloading, each electric motor for driving and unloading must have the same output performance, which leads to an increase in the size and cost of each electric motor.

[0006] The present invention aims to provide an industrial vehicle that makes it possible to reduce the size of each electric motor for driving and loading while suppressing insufficiency in maximum output performance for driving and loading. [Means for solving the problem]

[0007] An industrial vehicle according to one embodiment of the present invention is an industrial vehicle equipped with a loading motor that drives a loading device and a traveling electric motor that drives wheels, and is equipped with a loading output path formed between the loading motor and a loading oil pump, a traveling output path formed between the traveling electric motor and the wheels, an assist electric motor for assisting the loading motor or the traveling electric motor, assist power paths formed between the assist electric motor and the loading output path and between the assist electric motor and the traveling output path, and an assist power switching unit that switches whether to transmit power from the assist electric motor to either the oil pump or the wheels via the assist power path.

[0008] In an industrial vehicle according to one aspect of the present invention, when the assist power switching unit switches so that the power from the assist motor is transmitted to the oil pump via the assist power path, the assist motor assists the loading motor. Alternatively, when the assist power switching unit switches so that the power from the assist motor is transmitted to the wheels via the assist power path, the assist motor assists the traveling motor. Depending on the switching of the assist power switching unit, the maximum output performance for traveling and loading can be improved by the assistance of the assist motor, compared to each motor alone. As a result, it becomes possible to select electric motors with lower output as the traveling and loading motors, and therefore it becomes possible to reduce the size of each electric motor. Therefore, it becomes possible to reduce the size of each electric motor for traveling and loading while suppressing a shortage of output performance for traveling and loading.

[0009] In one embodiment, the assist power path includes a first gear pair provided between the output shaft of the assist electric motor and the load output path, and a first planetary gear mechanism provided between the output shaft of the assist electric motor and the traveling output path, and the first planetary gear mechanism may include a fixed first ring gear, a first planetary gear serving as an input section for power from the assist electric motor, and a first sun gear serving as an output section for power to the traveling output path. In this case, the power from the assist electric motor can be output to the traveling output path while reducing the rotation speed by the first planetary gear mechanism.

[0010] In one embodiment, the assist power path includes a second planetary gear mechanism provided between the output shaft of the assist motor and the load output path, and between the output shaft of the assist motor and the running output path, and a second gear pair provided between the second planetary gear mechanism and the load output path. The second planetary gear mechanism includes a second planetary gear journaled on a fixed planetary carrier, a second ring gear serving as an input part of the power from the assist motor, and a second sun gear serving as an output part of the power to the running output path. The outer circumferential surface of the second ring gear may be formed with external teeth that mesh with the gear of the second gear pair on the load output path side. In this case, the power from the assist motor can be output to the running output path while reducing the rotation speed by the second planetary gear mechanism. In addition, since one of the second gear pair is the external teeth formed on the outer circumferential surface of the second ring gear, the axial dimension can be reduced compared to the case where one of the second gear pair is a separately provided gear.

[0011] In one embodiment, the assist power path may have a third gear pair provided between the output shaft of the assist motor and the load output path, and a fourth gear pair provided between the output shaft of the assist motor and the travel output path. In this case, the assist power path can be easily configured by using two gear pairs.

[0012] In one embodiment, the assist power switching unit may have a hub sleeve provided between the assist power path and the load output path, and a hub sleeve provided between the assist power path and the traveling output path. In this case, for example, depending on whether a gear or the like included in the assist power path is engaged with the hub sleeve of the load output path, it is possible to switch whether or not the power from the assist electric motor is transmitted to the oil pump. Also, depending on whether a gear or the like included in the assist power path is engaged with the hub sleeve of the traveling output path, it is possible to switch whether or not the power from the assist electric motor is transmitted to the wheels.

[0013] In one embodiment, the vehicle includes a pressure acquisition unit that acquires the pressure of a lift cylinder for loading and unloading, and a switching control unit that controls the assist power switching unit based on the pressure of the lift cylinder, and the switching control unit may control the assist power switching unit to transmit the power from the assist electric motor to the traveling output path via the assist power path when the pressure of the lift cylinder is less than a predetermined pressure threshold. In this case, since the pressure of the lift cylinder is low enough that the assist of the loading and unloading electric motor is not required, the power from the assist electric motor can be transmitted to the wheels without being transmitted to the oil pump.

[0014] In one embodiment, the vehicle includes a torque acquisition unit that acquires wheel torque that drives the wheels, and a switching control unit that controls the assist power switching unit based on the wheel torque, and the switching control unit may control the assist power switching unit to transmit power from the assist electric motor to the driving output path via the assist power path when the wheel torque is equal to or greater than a predetermined torque threshold. In this case, since the wheel torque is large enough that assistance to the driving electric motor is required, the power from the assist electric motor can be transmitted to the wheels without being transmitted to the oil pump.

[0015] In one embodiment, the vehicle includes a rotation speed acquisition unit that acquires the rotation speed of the wheels, and a switching control unit that controls the assist power switching unit based on the rotation speed of the wheels, and the switching control unit may control the assist power switching unit so as not to transmit the power from the assist electric motor to the loading output path via the assist power path when the rotation speed of the wheels is equal to or higher than a predetermined rotation speed threshold. In this case, since the industrial vehicle is traveling at a certain speed or higher, loading and unloading work that requires assistance from the loading and unloading electric motor is unlikely to be performed. Therefore, a state in which the power from the assist electric motor is not transmitted to the oil pump can be set. Effect of the Invention

[0016] According to the present invention, it is possible to reduce the size of each electric motor for traveling and loading / unloading while suppressing a shortage of maximum output performance for traveling and loading / unloading. [Brief description of the drawings]

[0017] [Figure 1] 1 is a block diagram showing a schematic configuration of an industrial vehicle according to an embodiment; [Diagram 2] 2 is a schematic configuration diagram showing an example of a drive system of the industrial vehicle shown in FIG. 1. [Diagram 3] 3 is a diagram showing a state in which assist power is not transmitted to either the oil pump or the wheels in the drive system of FIG. 2. [Figure 4] 3 is a diagram showing a state in which assist power is transmitted to wheels in the drive system of FIG. 2. [Diagram 5] 3 is a diagram showing a state in which assist power is transmitted to an oil pump in the drive system of FIG. 2. [Figure 6] FIG. 4 is a diagram illustrating an example of a relationship between wheel torque and wheel rotation speed. [Figure 7] FIG. 7 is a diagram for explaining a predetermined travel of the industrial vehicle in FIG. 6. [Figure 8] FIG. 4 is a diagram illustrating an example of a relationship between a flow rate of an oil pump and a discharge pressure of the oil pump. [Figure 9] 2 is a flowchart showing an example of a calculation process performed by the control device of FIG. 1. [Figure 10] FIG. 13 is a schematic diagram showing a modified example of the drive system of the industrial vehicle. [Figure 11] 11 is a diagram showing a state in which the assist power is not transmitted to either the oil pump or the wheels in the drive system of FIG. 10. FIG. [Figure 12] 11 is a diagram showing a state in which assist power is transmitted to wheels in the drive system of FIG. 10. FIG. [Figure 13] 11 is a diagram showing a state in which assist power is transmitted to an oil pump in the drive system of FIG. 10. FIG. [Figure 14] FIG. 13 is a schematic diagram showing another modified example of the drive system of the industrial vehicle. [Figure 15]15 is a diagram showing a state in which the assist power is not transmitted to either the oil pump or the wheels in the drive system of FIG. 14. [Figure 16] 15 is a diagram showing a state in which assist power is transmitted to wheels in the drive system of FIG. 14. FIG. [Figure 17] 15 is a diagram showing a state in which assist power is transmitted to an oil pump in the drive system of FIG. 14. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are designated by the same reference numerals, and duplicated explanations will be omitted.

[0019] FIG. 1 is a block diagram showing a schematic configuration of an industrial vehicle according to an embodiment. FIG. 1 shows a forklift 10 as an example of an industrial vehicle. The forklift 10 is configured as an electric vehicle that runs on a motor. The power source for the motor is, for example, a battery mounted on the machine base (vehicle body). The forklift 10 is not particularly limited, but may be, for example, a relatively large four-wheeled vehicle. The forklift 10 may be of a type in which a motor is mounted on a machine base on which an internal combustion engine is conventionally mounted, instead of an internal combustion engine.

[0020] The forklift 10 includes, for example, a pair of front wheels (wheels) provided at the front and a pair of rear wheels provided at the rear. The front wheels here are driving wheels 10T (see FIG. 2), and the rear wheels (not shown) are steering wheels.

[0021] The forklift 10 is equipped with a loading device. The loading device may be provided in front of the driver's seat. The loading device has a mast, a lift cylinder 10L, a tilt cylinder, and a fork.

[0022] The forklift 10 may include a driver's seat. The driver's seat is provided with, for example, a loading operation lever 11 for loading and unloading operations, an accelerator pedal 12 for forward and backward operation, and a steering wheel 13 for steering operations. The loading operation lever 11 may include a lift lever and a tilt lever. The lift lever is a lever for operating a lift operation that moves the forks in the vertical direction. The tilt lever is a lever for operating a tilt operation that tilts the loading device. When the lift lever is operated, the lift cylinder is driven to extend and retract, causing the mast to slide and retract in the vertical direction, and the forks are raised and lowered in conjunction with this. When the tilt lever is operated, the tilt cylinder is driven to extend and retract, causing the lower part of the mast to move in the front-rear direction, and the tilt angle of the loading device is adjusted.

[0023] The forklift 10 includes a drive system 20. The drive system 20 is a device for transmitting power generated in a motor to wheels, etc. The drive system 20 includes a loading drive system 30, a traveling drive system 40, and an assist drive system 50.

[0024] The cargo handling drive system 30 is a power train that generates a driving force for operating the cargo handling equipment. The cargo handling drive system 30 drives the lift cylinder and the tilt cylinder by supplying hydraulic oil to them. The cargo handling drive system 30 includes a cargo handling motor (electric motor for cargo handling) 31, which is a drive source for driving the cargo handling equipment, and a cargo handling oil pump 32 that pumps hydraulic oil to each of the lift cylinder and the tilt cylinder.

[0025] The oil pump 32 supplies hydraulic oil to the lift cylinder and tilt cylinder via a valve section that controls the supply destination and supply amount. For example, when the driver operates the lift lever, the valve in the valve section that corresponds to the lift cylinder opens to an opening degree according to the amount of operation, and the other valves close. The loading motor 31 rotates at a speed according to the amount of operation, and pumps hydraulic oil. The pumped hydraulic oil is supplied to the lift cylinder via the open valve.

[0026] The lift cylinder 10L is provided with a hydraulic sensor (pressure acquisition unit) 14. The hydraulic sensor 14 detects the pressure of the lift cylinder 10L. The pressure of the lift cylinder 10L corresponds to the load of the forklift, and corresponds to the weight of the load loaded on the forklift 10.

[0027] The traveling drive system 40 is a power train that generates a driving force for driving the driving wheels 10T to travel the forklift 10. The traveling drive system 40 drives the driving wheels 10T by transmitting a rotational force to the driving wheels 10T. The traveling drive system 40 includes a traveling motor (traveling electric motor) 41 that is a drive source for driving the driving wheels 10T.

[0028] When the driver operates the accelerator pedal 12, the traveling motor 41 rotates at a rotation speed corresponding to the amount of operation of the accelerator pedal 12. The traveling drive system 40 also includes a steering mechanism that steers the rear wheels based on the operation of the steering wheel 13.

[0029] The assist drive system 50 is a power train for assisting the cargo handling motor 31 or the traveling motor 41 with an assist motor (assist electric motor) 51. The assist drive system 50 includes an assist motor 51, a cargo handling assist switching unit (assist output switching unit) 52, and a traveling assist switching unit (assist output switching unit) 53. The assist motor 51 is a drive source for assisting the cargo handling motor 31 or the traveling motor 41. The assist motor 51 drives either the oil pump 32 or the driving wheels 10T depending on the states of the cargo handling assist switching unit 52 and the traveling assist switching unit 53. Alternatively, the assist motor 51 does not drive either the oil pump 32 or the driving wheels 10T depending on the states of the cargo handling assist switching unit 52 and the traveling assist switching unit 53.

[0030] Fig. 2 is a schematic diagram showing an example of a drive system of the industrial vehicle of Fig. 1. As shown in Fig. 2, the drive system 20 has a gear box 21. As an example, the gear box 21 has a case 22. The gear box 21 transmits the power input from the loading motor 31 to the oil pump 32. The gear box 21 switches whether to transmit the power input from the assist motor 51 to the oil pump 32 or the driving wheels 10T, or to neither.

[0031] The gearbox 21 is provided with a loading shaft 33 connected to the output shaft of the loading motor 31, an assisted shaft 42 connected to the output shaft of the traveling motor 41, and an assist shaft 54 ​​connected to the output shaft of the assist motor 51. The loading shaft 33, the assisted shaft 42, and the assist shaft 54 ​​are each supported by, for example, a bearing fixed to the case 22 of the gearbox 21.

[0032] As an example, the assisted shaft 42 is disposed adjacent to the loading shaft 33. Here, the assisted shaft 42 is disposed adjacent to and parallel to the loading shaft 33. The loading motor 31 and the traveling motor 41 are attached to the gear box 21 adjacent to each other. The driving torques from the loading motor 31 and the traveling motor 41 can be input to the gear box 21 independently.

[0033] The assist shaft 54 ​​is disposed adjacent to the loading shaft 33. The assist shaft 54 ​​here is disposed adjacent to and parallel to the loading shaft 33. The assist shaft 54 ​​is disposed, for example, on an extension of the assisted shaft 42 so as to be coaxial with the assisted shaft 42. The loading motor 31 and the oil pump 32 are attached to the gear box 21 adjacent to each other. Power from the assist motor 51 (hereinafter also simply referred to as "assist power") can be input to the gear box 21 independently of the loading motor 31 and the traveling motor 41.

[0034] A loading output path 34 is formed between the loading motor 31 and the oil pump 32. The loading shaft 33 is, for example, connected to the output shaft of the loading motor 31 so as to be rotatable together with the output shaft of the loading motor 31. The loading shaft 33 is connected to the input shaft of the oil pump 32 so as to be rotatable together with the input shaft of the oil pump 32. The rotation and torque of the loading motor 31 are transmitted to the oil pump 32 via the loading shaft 33. In other words, a loading output path 34 including the loading shaft 33 is formed between the loading motor 31 and the oil pump 32.

[0035] A traveling output path 44 is formed between the traveling motor 41 and the driving wheel 10T. The traveling motor 41 here is a double-shaft motor, for example. The traveling motor 41 has an output shaft extending to both the gearbox 21 side and the driving wheel 10T side. Here, the assisted shaft 42 on the gearbox 21 side and the traveling shaft 43 on the driving wheel 10T side are connected to the output shaft of the traveling motor 41 so as to be rotatable together with the output shaft of the traveling motor 41. The traveling shaft 43 is connected to the drive shaft of the driving wheel 10T so as to be rotatable together with the driving wheel 10T. That is, a traveling output path 44 including the traveling shaft 43 is formed between the traveling motor 41 and the driving wheel 10T. Note that the assisted shaft 42 on the gearbox 21 side can also be considered as a part of the traveling output path 44 since it can rotate together with the output shaft of the traveling motor 41.

[0036] An assist gear pair (first gear pair) 55 is provided between the loading shaft 33 and the assist shaft 54. The assist gear pair 55 is, for example, a pair of gears 55a, 55b that have a diameter dimension that results in a predetermined gear ratio and are constantly meshed. The gear 55a is fixed to the assist shaft 54 ​​and rotates together with the assist shaft 54. The gear 55b is journaled so as to be rotatable relative to the loading shaft 33 and can rotate independently of the loading shaft 33.

[0037] The assist gear pair 55 is provided with a hub sleeve 56 as the cargo handling assist switching unit 52. The hub sleeve 56 is, for example, splined and fitted to the cargo handling shaft 33, and rotates together with the cargo handling shaft 33. The hub sleeve 56 is capable of moving toward or away from the gear 55b of the assist gear pair 55 along the cargo handling shaft 33. A plurality of protrusions are formed on the gear 55b side of the hub sleeve 56 so as to correspond to a plurality of projections and recesses provided on the side surface of the gear 55b. The hub sleeve 56 is capable of engaging with the side surface of the gear 55b.

[0038] The rotation and torque of the assist shaft 54 ​​is transmitted to the gear 55b as the gear 55a rotates the gear 55b, and is transmitted to the loading shaft 33 via the hub sleeve 56 in a state in which the hub sleeve 56 is engaged with the side surface of the gear 55b. In other words, an assist power path 57 including the assist shaft 54, the assist gear pair 55 (gears 55a, 55b), the hub sleeve 56, and the loading shaft 33 is formed between the assist motor 51 and the loading output path 34.

[0039] When the hub sleeve 56 moves away from the gear 55b and is no longer engaged with the side surface of the gear 55b, it does not transmit rotation and torque from the assist shaft 54 ​​to the loading shaft 33. In other words, when the hub sleeve 56 does not engage with the side surface of the gear 55b, the state is switched to one in which the power from the assist motor 51 is not transmitted to the oil pump 32 via the assist power path 57. In other words, the hub sleeve 56 here is provided between the assist power path 57 and the loading output path 34, and functions as a loading assist switching unit (assist power switching unit) 52 that switches whether or not the power from the assist motor 51 is transmitted to the oil pump 32 via the assist power path 57.

[0040] A planetary gear mechanism (first planetary gear mechanism) 58 is provided between the assist shaft 54 ​​and the assisted shaft 42. The planetary gear mechanism 58 has a ring gear (first ring gear) 58a, a planetary gear (first planetary gear) 58b, and a sun gear (first sun gear) 58c.

[0041] The ring gear 58a is an internal gear having internal teeth formed thereon to mesh with the planetary gears 58b. The ring gear 58a here is fixed to the case 22 of the gear box 21.

[0042] A plurality of planetary gears 58b are provided so as to surround the sun gear 58c. The planetary gears 58b are rotatably supported by the planetary carrier and mesh with the ring gear 58a and the sun gear 58c. The planetary carrier is provided so as to be rotatable with respect to the sun gear 58c. As shown by the thick hook-shaped line in FIG. 2, the planetary carrier here is connected to the assist shaft 54. The planetary carrier may be connected to the assist shaft 54 ​​via the gear 55a of the assist gear pair 55. As a result, the planetary gear 58b serves as an input section for the power from the assist motor 51, and the power from the assist motor 51 is input to the planetary gear mechanism 58 via the planetary carrier.

[0043] The sun gear 58c is journaled so as to be rotatable relative to the assisted shaft 42, and can rotate independently of the assisted shaft 42. The sun gear 58c serves as an output section for power from the planetary gear mechanism 58 to the traveling output path 44, and outputs the power from the assist motor 51 transmitted from the planetary gear 58b to the assisted shaft 42 of the traveling output path 44.

[0044] The sun gear 58c is provided with a hub sleeve 59 as the travel assist switching unit 53. The hub sleeve 59 is fitted to the assisted shaft 42, for example, by a spline, and rotates together with the assisted shaft 42. The hub sleeve 59 is capable of moving toward or away from the sun gear 58c along the assisted shaft 42. A plurality of protrusions are formed on the sun gear 58c side of the hub sleeve 59 so as to correspond to a plurality of irregularities provided on the side surface of the sun gear 58c. The hub sleeve 59 can engage with the side surface of the sun gear 58c.

[0045] The rotation and torque of the assist shaft 54 ​​are transmitted to the planetary gear 58b via the planetary carrier, and are then transmitted to the sun gear 58c by the planetary gear 58b rotating the sun gear 58c. The rotation and torque of the assist shaft 54 ​​are transmitted to the assisted shaft 42 via the hub sleeve 59 in a state in which the hub sleeve 59 is engaged with the side surface of the sun gear 58c. The rotation and torque of the assist shaft 54 ​​transmitted to the assisted shaft 42 are transmitted to the traveling shaft 43 on the driving wheel 10T side via the output shaft of the traveling motor 41, which is a dual-shaft motor. That is, between the output shaft of the assist motor 51 and the traveling output path 44, an assist power path 57 is formed, which includes the assist shaft 54, the planetary gear mechanism 58 (planetary gear 58b, sun gear 58c), the hub sleeve 59, and the assisted shaft 42.

[0046] When the hub sleeve 59 moves away from the sun gear 58c and is no longer engaged with the side surface of the sun gear 58c, it does not transmit rotation and torque from the assist shaft 54 ​​to the assisted shaft 42. In other words, when the hub sleeve 59 does not engage with the side surface of the sun gear 58c, the state is switched to one in which the power from the assist motor 51 is not transmitted to the driving wheel 10T via the assist power path 57. In other words, the hub sleeve 59 here is provided between the assist power path 57 and the traveling output path 44, and functions as a traveling assist switching unit (assist power switching unit) 53 that switches whether or not the power from the assist motor 51 is transmitted to the driving wheel 10T via the assist power path 57.

[0047] The operation of the drive system 20 configured as described above will be described with reference to Figs. 3 to 5. Fig. 3 is a diagram showing a state in which the assist power is not transmitted to either the oil pump or the wheels in the drive system of Fig. 2. In the example of Fig. 3, the hub sleeve 56 is not engaged with the side surface of the gear 55b, and the hub sleeve 59 is not engaged with the side surface of the sun gear 58c. Therefore, the assist power path 57 is switched so that the power from the assist motor 51 is not transmitted to the oil pump 32, and is also switched so that the power from the assist motor 51 is not transmitted to the drive wheels 10T.

[0048] In this case, the load output path 34 and the traveling output path 44 operate without assistance from the assist motor 51. Specifically, the output of the load motor 31 is transmitted to the oil pump 32 via the load shaft 33 without assistance from the assist motor 51. The output of the traveling motor 41 is transmitted to the driving wheel 10T via the traveling shaft 43 from the assisted shaft 42 without assistance from the assist motor 51.

[0049] Fig. 4 is a diagram showing a state in which the assist power is transmitted to the wheels in the drive system of Fig. 2. In the example of Fig. 4, the hub sleeve 56 is not engaged with the side surface of the gear 55b. On the other hand, the hub sleeve 59 is engaged with the side surface of the sun gear 58c. The assist power path 57 is switched so that the power from the assist motor 51 is not transmitted to the oil pump 32, but is switched so that the power from the assist motor 51 is transmitted to the drive wheel 10T.

[0050] In this case, the traveling output path 44 and the assist power path 57 are connected, and the assist motor 51 assists the traveling motor 41. Specifically, the output of the traveling motor 41 is transmitted to the driving wheel 10T via the traveling shaft 43 in the same manner as in the example of FIG. 3. Here, the power of the assist motor 51 is further transmitted to the traveling output path 44 via the assist power path 57. The power of the assist motor 51 is transmitted to the planet carrier of the planetary gear mechanism 58 via the assist shaft 54 ​​and the gear 55a of the assist gear pair 55. The power of the assist motor 51 is transmitted to the planetary gear 58b via the planetary carrier, and the planetary gear 58b rotates the sun gear 58c, thereby transmitting the power to the sun gear 58c. The power of the assist motor 51 is transmitted to the assisted shaft 42 via the hub sleeve 59 engaged with the sun gear 58c, and is transmitted to the traveling output path 44.

[0051] Fig. 5 is a diagram showing a state in which the assist power is transmitted to the oil pump in the drive system of Fig. 2. In the example of Fig. 5, the hub sleeve 59 is not engaged with the side surface of the sun gear 58c. Meanwhile, the hub sleeve 56 is engaged with the side surface of the gear 55b. The assist power path 57 is switched so that the power from the assist motor 51 is not transmitted to the drive wheel 10T, but is switched so that the power from the assist motor 51 is transmitted to the oil pump 32.

[0052] In this case, the load output path 34 and the assist power path 57 are connected, and the assist motor 51 assists the load motor 31. Specifically, the output of the load motor 31 is transmitted to the oil pump 32 via the load shaft 33 in the same manner as in the example of FIG. 3. Here, the power of the assist motor 51 is further transmitted to the load output path 34 via the assist power path 57. The power of the assist motor 51 is transmitted to the gear 55b via the assist shaft 54 ​​and the assist gear pair 55 by the gear 55a rotating the gear 55b. The power of the assist motor 51 is transmitted to the load shaft 33 via the hub sleeve 56 engaged with the gear 55b, and then to the load output path 34.

[0053] Returning to Fig. 1, the forklift 10 has a control device 60 that controls the drive system 20. The control device 60 is a device for controlling the operation of the forklift 10. The control device 60 controls the drive system 20 based on the operation of the cargo handling operation lever 11 and the accelerator pedal 12.

[0054] The control device 60 is an electronic control unit having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. In the control device 60, for example, a program recorded in the ROM is loaded into the RAM, and the program loaded into the RAM is executed by the CPU, thereby realizing various functions. Note that the control device 60 may be composed of multiple electronic units.

[0055] The control device 60 is electrically connected to the cargo handling operation lever 11, the accelerator pedal 12, and the steering wheel 13, and receives operation commands from these. The control device 60 is electrically connected to the hydraulic sensor 14, and receives a detection signal of the hydraulic pressure of the lift cylinder transmitted from the hydraulic sensor 14. The control device 60 is electrically connected to the drive system 20, and transmits a control signal for controlling the drive system 20.

[0056] Next, a description will be given of the functional configuration of the control device 60. The control device 60 has a loading state acquisition unit (pressure acquisition unit) 61, a traveling state acquisition unit (torque acquisition unit, rotation speed acquisition unit) 62, and an output control unit (switching control unit) 63.

[0057] The loading status acquisition unit 61 acquires the status (load) of the loading device. The status of the loading device is obtained by the pressure of the lift cylinder 10L. The loading status acquisition unit 61 acquires the pressure of the lift cylinder 10L based on the detection result of the hydraulic sensor 14, for example.

[0058] The traveling state acquisition unit 62 acquires the state of the driving wheel 10T as the traveling state of the forklift 10. The state of the driving wheel 10T includes the wheel torque and the wheel rotation speed. The traveling state acquisition unit 62 can calculate the wheel torque driving the driving wheel 10T, for example, using a known conversion formula or the like based on the depression amount of the accelerator pedal 12. The wheel torque is an estimated value of the torque equivalent to the driving force of the driving wheel 10T. The value of the wheel torque may change prior to the actual driving torque of the driving wheel 10T, or may represent a target value of the driving force of the driving wheel 10T. The traveling state acquisition unit 62 can calculate the wheel rotation speed, for example, using a known conversion formula or the like based on the detection result of a rotation speed sensor provided in the traveling motor 41.

[0059] The output control unit 63 controls the state of the drive system 20, including the output (power running) of the loading motor 31, the output (power running) of the traveling motor 41, and the output (power running) of the assist motor 51, based on the acquired state of the loading device, the state of the drive wheels 10T, and the operation amount of the loading operation lever 11 and the accelerator pedal 12. The output control unit 63 controls the loading motor 31 so as to have a rotation speed corresponding to the operation amount of the loading operation lever 11, for example, by sending a control signal to the loading motor 31. The output control unit 63 controls the traveling motor 41 so as to have a rotation speed corresponding to the depression amount of the accelerator pedal 12, for example, by sending a control signal to the traveling motor 41.

[0060] The output control unit 63 controls the cargo handling assist switching unit 52 and the driving assist switching unit 53 by sending a control signal to the drive system 20, and switches whether or not to transmit the power from the assist motor 51 to either the oil pump 32 or the driving wheels 10T via the assist power path 57. For example, when the assist motor 51 is capable of driving either the oil pump 32 or the driving wheels 10T, the output control unit 63 sends a control signal to the assist motor 51 to control the rotation speed and torque of the assist motor 51 so as to assist the cargo handling motor 31 or the driving motor 41.

[0061] [Assistance of the traction motor by the assist motor based on wheel torque] The output control unit 63 can control the cargo handling assist switching unit 52 and the driving assist switching unit 53 based on the wheel torque.

[0062] FIG. 6 is a diagram showing an example of the relationship between the wheel torque and the wheel rotation speed. The horizontal axis of FIG. 6 is the wheel rotation speed, which corresponds to the vehicle speed of the forklift 10. The vertical axis of FIG. 6 is the wheel torque, which corresponds to the target value of the driving force of the driving wheel 10T, and in this embodiment, is the torque target value calculated from the depression amount of the accelerator pedal 12. The solid line L1B in FIG. 6 shows the output characteristic of the traveling motor 41. The dashed line L1A in FIG. 6 shows the output characteristic on the traveling shaft 43 of the assist motor 51. The solid line L1C in FIG. 6 shows the output characteristic when the output of the assist motor 51 is added to the output of the traveling motor 41. Each plot in FIG. 6 is a trajectory of the state of the driving wheel 10T when the forklift 10 travels in a predetermined manner. The output characteristic of the traveling motor 41 is set to an output characteristic that includes, for example, a plot on the high vehicle speed side in FIG. 6 so that the forklift 10 can travel against the traveling resistance assumed in the design of the forklift 10.

[0063] Fig. 7 is a diagram for explaining a predetermined traveling of the industrial vehicle in Fig. 6. As an example, the predetermined traveling is assumed to be a driving pattern in which an unloaded forklift 10 is stopped or moving slowly, lifts a load using the loading device, starts with the load lifted, and increases the vehicle speed.

[0064] During a given travel, when an unloaded forklift 10 is stopped or moving slowly and is about to lift a load using the loading device, the forklift 10 is required to drive both the loading device and the drive wheels 10T. In such a situation, the locus (plot) of the state of the drive wheels 10T is likely to exist in the area DR1 surrounded by the dashed line. The area DR1 surrounded by the dashed line corresponds to an area where the wheel rotation speed is less than a predetermined value and the wheel torque is less than a predetermined value. The predetermined value of the wheel torque is, for example, an upper limit torque value that can be taken on the low vehicle speed side of the traveling motor 41. The low vehicle speed side may be, for example, a vehicle speed lower than the maximum vehicle speed of the loading motor 31 (vehicle speed at the right end of the dashed line L1A) aligned with the coordinate system of FIG. 6.

[0065] The output control unit 63 may control the load handling assist switching unit 52 and the traveling assist switching unit 53 so as not to transmit power from the assist motor 51 to the traveling output path 44 via the assist power path 57 when the wheel torque is less than a predetermined torque threshold. The predetermined torque threshold is a wheel torque threshold for determining whether the assist motor 51 assists the traveling motor 41. The torque threshold is set to a value shown as a solid line L1B in FIG. 6, for example. The torque threshold may be set to a value shown as a dashed line Th1 in FIG. 7. By setting such a torque threshold, the region DR1 surrounded by the dashed line is included in the region below the torque threshold.

[0066] 7 is an example of a trajectory of the state of the drive wheels 10T in a driving pattern in which the forklift 10 starts traveling and increases its vehicle speed. Among the dashed dotted line DR2, the dashed dotted line DR2a, which is a portion where the wheel rotation speed rises from the point of 0, corresponds to the time when the forklift 10 starts traveling.

[0067] When the forklift 10, which has lifted a load using the loading device, starts traveling, the driving force of the drive wheels 10T required for the forklift 10 to travel tends to increase according to the weight of the load. In such a situation, as shown by the dashed line DR2a, the wheel torque (target value of the driving force) may be equal to or greater than the torque threshold. In this case, the output control unit 63 may control the load handling assist switching unit 52 and the traveling assist switching unit 53 so that the power from the assist motor 51 is transmitted to the traveling output path 44 via the assist power path 57 when the wheel torque is equal to or greater than the torque threshold. As a result, the drive system 20 is set to a state in which the assist motor 51 assists the traveling motor 41, as shown in FIG. 4. Since the power of the assist motor 51 is transmitted to the traveling output path 44 via the assist power path 57, the driving force of the drive wheels 10T can be realized by adding the power of the assist motor 51 to the output of the traveling motor 41. In the example of FIG. 6 and FIG. 7, the driving force of the driving wheel 10T can be realized within a range up to the solid line L1C.

[0068] In addition, among the dashed-dotted line DR2 in FIG. 7, the dashed-dotted line DR2b on the high vehicle speed side from the apex corresponds to a situation in which the vehicle speed of the forklift 10 is increased when the forklift 10 is lifting a load using the loading device, and the acceleration is gentler than when the forklift 10 starts traveling. Therefore, in the example of FIG. 7, the wheel torque required for traveling is gradually decreased. For example, when the driving force of the drive wheel 10T can be covered by the output of the traveling motor 41, the assist of the traveling motor 41 by the assist motor 51 is released. As shown in FIG. 3, the drive system 20 is set to a state in which the load output path 34 and the traveling output path 44 operate without the assist of the assist motor 51. If the assist of the traveling motor 41 by the assist motor 51 is released during traveling, a sudden deceleration may occur. Therefore, it is preferable to release the assist of the traveling motor 41 by the assist motor 51 only when the wheel torque is less than the torque threshold value.

[0069] [Assistance of the cargo handling motor by the assist motor based on the hydraulic pressure of the lift cylinder] The output control unit 63 can control the cargo handling assist switching unit 52 and the traveling assist switching unit 53 based on the hydraulic pressure (hereinafter, sometimes simply referred to as "pressure") of the lift cylinder.

[0070] FIG. 8 is a diagram showing an example of the relationship between the flow rate of the oil pump and the discharge pressure. The horizontal axis of FIG. 8 is the discharge flow rate of the oil pump 32, which increases or decreases according to the rotation speed of the oil pump 32. The vertical axis of FIG. 8 is the discharge pressure of the oil pump 32, which corresponds to the target value of the pressure of the hydraulic oil supplied to the loading device. The solid line L2A in FIG. 8 shows the output characteristic of the oil pump 32 by the loading motor 31. The dashed line L2B in FIG. 8 shows the output characteristic of the oil pump 32 by the assist motor 51. The solid line L2C in FIG. 8 shows the output characteristic of the oil pump 32 when the output of the assist motor 51 is added to the output of the loading motor 31. The solid line L2A and dashed line L2B are determined by the characteristics of the loading motor 31, the assist motor 51, and the oil pump 32 mounted on the forklift 10. Each plot in FIG. 8 is a trajectory of the discharge pressure of the oil pump 32 when the forklift 10 performs a predetermined loading operation. As an example, the predetermined loading operation is assumed to be a work pattern of the forklift 10. Each plot shows the position of the operating point of the lift operation and / or tilt operation with or without a load relative to the output of the oil pump 32. Area LD1 shows the case where the lift operation is performed with a maximum load. Area LD2 shows the case where the lift operation is performed with an empty load. Area LD3 shows the case where only the tilt operation is performed with a maximum load and with an empty load.

[0071] In Fig. 8, when the load is increased from the region LD2 in an unloaded state, there is a boundary between the region LD2 and the maximum load region LD1, where the output is insufficient with only the cargo motor 31. This boundary is the upper limit pressure value when the oil pump 32 is driven only by the cargo motor 31, and corresponds to the solid line L2A in Fig. 8.

[0072] Therefore, the output control unit 63 sets the pressure of the lift cylinder 10L corresponding to the load shown by the solid line L2A as the pressure threshold. The output control unit 63 may control the cargo handling assist switching unit 52 and the traveling assist switching unit 53 to transmit the power from the assist motor 51 to the cargo handling output path 34 via the assist power path 57 when the pressure of the lift cylinder 10L is equal to or higher than the predetermined pressure threshold. The predetermined pressure threshold is a pressure threshold for determining whether the assist motor 51 assists the cargo handling motor 31. By setting such a pressure threshold, each plot (e.g., area LD1) of the discharge pressure when the lift cylinder 10L is driven under high load is included in a range with the solid line L2C as the upper limit.

[0073] As a result, the drive system 20 is set to a state in which the assist motor 51 assists the cargo handling motor 31, as shown in Fig. 5. Since the power of the assist motor 51 is transmitted to the cargo handling output path 34 via the assist power path 57, the discharge pressure of the oil pump 32 can be realized by adding the output of the assist motor 51 to the output of the cargo handling motor 31. In the example of Fig. 8, the discharge pressure of the oil pump 32 can be realized within a range whose upper limit is the solid line L2C.

[0074] When the pressure of the lift cylinder 10L equal to or greater than the pressure threshold is no longer required, the assist of the load motor 31 by the assist motor 51 is released. As shown in FIG. 3, the drive system 20 is set to a state in which the load output path 34 and the traveling output path 44 operate without the assistance of the assist motor 51.

[0075] In addition, the area LD2 surrounded by the dashed line in FIG. 8 includes a plot of the discharge pressure of the oil pump 32 when driving the lift cylinder 10L with no load, for example. The area LD3 surrounded by the dashed line in FIG. 8 includes a plot of the discharge pressure of the oil pump 32 when driving only the tilt cylinder to tilt the fork. When the pressure of the lift cylinder 10L is less than a predetermined pressure threshold, the output control unit 63 may control the load handling assist switching unit 52 and the traveling assist switching unit 53 so as not to transmit the power from the assist motor 51 to the traveling output path 44 via the assist power path 57. As a result, the drive system 20 is set to a state in which the load handling output path 34 and the traveling output path 44 operate without the assistance of the assist motor 51, as shown in FIG. 3.

[0076] [Limiting the assist of the load handling motor by the assist motor based on the wheel rotation speed] The output control unit 63 can control the cargo handling assist switching unit 52 and the driving assist switching unit 53 based on the wheel rotation speed.

[0077] In the portion of the dashed dotted line DR2 in Fig. 7 on the high vehicle speed side from the apex, when the vehicle speed of the forklift 10 increases, the wheel rotation speed becomes equal to or exceeds the predetermined value Th2. In this manner, when the forklift 10 is traveling at or above the predetermined vehicle speed, it is difficult to carry out a loading operation that performs a lifting operation at maximum load (loading operation that performs a lifting operation to lift up, rather than maintaining the lifted state). Therefore, it is difficult for the discharge pressure to fall within the region LD1.

[0078] Therefore, the output control unit 63 may control the cargo handling assist switching unit 52 and the traveling assist switching unit 53 so as not to transmit the power from the assist motor 51 to the cargo handling output path 34 via the assist power path 57 when the wheel rotation speed is equal to or higher than a predetermined rotation speed threshold. The predetermined rotation speed threshold is a wheel rotation speed threshold for determining whether the assist motor 51 assists the cargo handling motor 31, and may be, for example, the above-mentioned predetermined value Th2. By setting such a rotation speed threshold, when the forklift 10 is traveling at a predetermined vehicle speed or higher corresponding to the rotation speed threshold, the cargo handling motor 31 can be in a state where it is not assisted by the assist motor 51 (a state where cargo handling is restricted).

[0079] [An example of computation processing by the control device 60] Next, a description will be given of an example of the calculation process performed by the control device 60. Fig. 9 is a flow chart showing an example of the calculation process performed by the control device of Fig. 1.

[0080] The process shown in Fig. 9 is executed, for example, while the forklift 10 is in operation. As shown in Fig. 9, in S01, the control device 60 acquires the pressure of the lift cylinder 10L by the load state acquisition unit 61. In S02, the control device 60 determines, by the output control unit 63, the load of the lift cylinder 10L equivalent to the discharge pressure shown as the solid line L2A in Fig. 8, for example, as the pressure threshold value of the lift cylinder 10L.

[0081] In S03, the control device 60 calculates (acquires) the wheel torque by the traveling state acquisition unit 62. The calculation of the wheel torque may take into account the vehicle speed of the forklift 10 and the weight of the load. In S04, the control device 60 determines a torque threshold value by the output control unit 63 based on, for example, characteristics determined from the traveling motor 41 and gear requirements (e.g., gear ratio, etc.), as shown by a solid line L1B in Fig. 6. Alternatively, in S04, the control device 60 may determine a torque threshold value by the output control unit 63, for example, as shown by a dashed line Th1 in Fig. 7.

[0082] In S05, the control device 60 calculates the wheel rotation speed using the driving state acquisition unit 62 based on the detection result of a rotation speed sensor provided in, for example, the driving motor 41. In S06, the control device 60 determines, using the output control unit 63, a wheel rotation speed equivalent to, for example, a predetermined value Th2 shown by a dashed line in Fig. 7, as the rotation speed threshold value.

[0083] In S07, the control device 60 determines whether the wheel rotation speed is equal to or greater than the rotation speed threshold value using the output control unit 63. When the output control unit 63 determines that the wheel rotation speed is equal to or greater than the rotation speed threshold value (S07: YES), in S08, the output control unit 63 controls the cargo handling assist switching unit 52 and the traveling assist switching unit 53 so that the assist motor 51 does not assist the cargo handling motor 31 and the traveling motor 41. The process in S08 corresponds to a cargo handling restricted state when the forklift 10 is traveling at a predetermined vehicle speed or higher corresponding to the rotation speed threshold value. Thereafter, the control device 60 ends the process in FIG. 9 and repeats the process in FIG. 9 after a predetermined calculation period.

[0084] On the other hand, when the output control unit 63 determines that the wheel rotation speed is not equal to or greater than the rotation speed threshold (the wheel rotation speed is less than the rotation speed threshold) (S07: NO), the control device 60 determines in S09 whether the pressure of the lift cylinder 10L is equal to or greater than the pressure threshold. When the output control unit 63 determines that the pressure of the lift cylinder 10L is equal to or greater than the pressure threshold (S09: YES), the control device 60 controls in S10 the load handling assist switching unit 52 and the travel assist switching unit 53 so that the assist motor 51 assists the load handling motor 31. Thereafter, the control device 60 ends the process of FIG. 9 and repeats the process of FIG. 9 after a predetermined calculation period.

[0085] When the output control unit 63 determines that the pressure of the lift cylinder 10L is not equal to or greater than the pressure threshold (the pressure of the lift cylinder 10L is less than the pressure threshold) (S09: NO), the control unit 60 determines in S11 whether the wheel torque is equal to or greater than the torque threshold. When the output control unit 63 determines that the wheel torque is equal to or greater than the torque threshold (S11: YES), the control unit 60 controls in S12 the load handling assist switching unit 52 and the traveling assist switching unit 53 so that the assist motor 51 assists the traveling motor 41. Thereafter, the control unit 60 ends the process of FIG. 9 and repeats the process of FIG. 9 after a predetermined calculation period.

[0086] On the other hand, if the output control unit 63 determines that the wheel torque is not equal to or greater than the torque threshold (the wheel torque is less than the torque threshold) (S11: NO), in S08, the output control unit 63 controls the cargo handling assist switching unit 52 and the traveling assist switching unit 53 so that the assist motor 51 does not assist the cargo handling motor 31 and the traveling motor 41. Thereafter, the control unit 60 ends the process of Fig. 9 and repeats the process of Fig. 9 after a predetermined calculation period.

[0087] [Action and Effects] As described above, in the forklift 10 according to the present embodiment, when the load handling assist switching unit 52 and the travel assist switching unit 53 are switched so that the power from the assist motor 51 is transmitted to the oil pump 32 via the assist power path 57, the assist motor 51 assists the load handling motor 31. Alternatively, when the load handling assist switching unit 52 and the travel assist switching unit 53 are switched so that the power from the assist motor 51 is transmitted to the drive wheel 10T via the assist power path 57, the assist motor 51 assists the travel motor 41. In response to the switching of the load handling assist switching unit 52 and the travel assist switching unit 53, the maximum output performance for traveling and loading / unloading can be improved by the assist of the assist motor 51, compared with the load handling motor 31 and the travel motor 41 alone. As a result, it is possible to select electric motors with lower output as the travel motor 41 for traveling and the load handling motor 31 for loading / unloading, so that the load handling motor 31 and the travel motor 41 can be made smaller. Therefore, it is possible to reduce the size of the travel motor 41 for traveling and the load handling motor 31 for loading / unloading while suppressing a shortage of output performance for traveling and loading / unloading.

[0088] In the forklift 10, the assist power path 57 has a constantly meshing assist gear pair 55 provided between the output shaft of the assist motor 51 and the load output path 34, and a planetary gear mechanism 58 provided between the output shaft of the assist motor 51 and the traveling output path 44. The planetary gear mechanism 58 has a fixed ring gear 58a, a planetary gear 58b serving as an input section for power from the assist motor 51, and a sun gear 58c serving as an output section for power to the traveling output path 44. With this configuration, the power from the assist motor 51 can be output to the traveling output path 44 while reducing the rotation speed by the planetary gear mechanism 58.

[0089] In the forklift 10, the cargo handling assist switching unit 52 and the traveling assist switching unit 53 have a hub sleeve 56 provided between the assist power path 57 and the cargo handling output path 34, and a hub sleeve 59 provided between the assist power path 57 and the traveling output path 44. With this configuration, it is possible to switch whether or not the power from the assist motor 51 is transmitted to the oil pump 32 depending on whether or not the assist gear pair 55 and the hub sleeve 56 of the cargo handling output path 34 are engaged. Also, it is possible to switch whether or not the power from the assist motor 51 is transmitted to the driving wheels 10T depending on whether or not the planetary gear mechanism 58 and the hub sleeve 59 of the traveling output path 44 are engaged.

[0090] The forklift 10 includes a loading state acquisition unit 61 that acquires the pressure of the lift cylinder 10L for loading and unloading, and an output control unit 63 that controls the loading assist switching unit 52 and the traveling assist switching unit 53 based on the pressure of the lift cylinder 10L. When the pressure of the lift cylinder 10L is less than a predetermined pressure threshold, the output control unit 63 controls the loading assist switching unit 52 and the traveling assist switching unit 53 to transmit the power from the assist motor 51 to the traveling output path 44 via the assist power path 57. According to this configuration, since the pressure of the lift cylinder 10L is low enough that the assistance to the loading motor 31 is not required, the power from the assist motor 51 can be transmitted to the driving wheels 10T without being transmitted to the oil pump 32.

[0091] The forklift 10 includes a driving state acquisition unit 62 that acquires the wheel torque that drives the driving wheels 10T, and an output control unit 63 that controls the cargo handling assist switching unit 52 and the traveling assist switching unit 53 based on the wheel torque. When the wheel torque is equal to or greater than a predetermined torque threshold, the output control unit 63 controls the cargo handling assist switching unit 52 and the traveling assist switching unit 53 to transmit the power from the assist motor 51 to the traveling output path 44 via the assist power path 57. According to this configuration, since the wheel torque is large enough to require assistance to the traveling motor 41, the power from the assist motor 51 can be transmitted to the driving wheels 10T without being transmitted to the oil pump 32.

[0092] The forklift 10 includes a traveling state acquisition unit 62 that acquires the rotation speed of the drive wheel 10T, and an output control unit 63 that controls the cargo handling assist switching unit 52 and the traveling assist switching unit 53 based on the rotation speed of the drive wheel 10T. When the rotation speed of the drive wheel 10T is equal to or higher than a predetermined rotation speed threshold, the output control unit 63 controls the cargo handling assist switching unit 52 and the traveling assist switching unit 53 so as not to transmit the power from the assist motor 51 to the cargo handling output path 34 via the assist power path 57. With this configuration, since the forklift 10 travels at a vehicle speed equal to or higher than a certain level, it is difficult to perform cargo handling work that requires assistance from the cargo handling motor 31. Therefore, it is possible to set the state in which the power from the assist motor 51 is not transmitted to the oil pump 32 (loading restriction state).

[0093] [Variations] Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment.

[0094] In the above embodiment, a configuration is illustrated in which the planetary gear mechanism 58 is used with two parallel shafts arranged so that the assist shaft 54 ​​is coaxial with the assisted shaft 42, but the present invention is not limited to this example.

[0095] For example, as shown in Fig. 10 to Fig. 13, the drive system 20A may have a three-axis parallel configuration without using a planetary gear mechanism. In the example of Fig. 10, the assist power path 57A has an assist gear pair (third gear pair) 55A provided between the output shaft of the assist motor 51 and the load output path 34, and an assist gear pair (fourth gear pair) 58A provided between the output shaft of the assist motor 51 and the traveling output path 44A. The assist gear pair 55A is provided with a hub sleeve 56A as the load assist switching unit 52. The assist gear pair 58A is provided with a hub sleeve 59A as the traveling assist switching unit 53.

[0096] The operation of the drive system 20A thus configured will be described with reference to Figs. 11 to 13. Fig. 11 is a diagram showing a state in which the assist power is not transmitted to either the oil pump or the wheels in the drive system of Fig. 10. In the example of Fig. 11, the hub sleeve 56A is not engaged with the side surface of the gear 55Ab of the assist gear pair 55A, and the hub sleeve 59A is not engaged with the side surface of the gear 58Aa of the assist gear pair 58A. Therefore, the assist power path 57A is switched so that the power from the assist motor 51 is not transmitted to the oil pump 32, and the power from the assist motor 51 is not transmitted to the drive wheels 10T.

[0097] In this case, the load output path 34 and the traveling output path 44A operate without assistance from the assist motor 51. Specifically, the output of the load motor 31 is transmitted to the oil pump 32 via the load shaft 33 without assistance from the assist motor 51. The output of the traveling motor 41 is transmitted to the drive wheel 10T via the traveling shaft 43A without assistance from the assist motor 51.

[0098] Fig. 12 is a diagram showing a state in which the assist power is transmitted to the wheels in the drive system of Fig. 10. In the example of Fig. 12, the hub sleeve 56A is not engaged with the side surface of the gear 55Ab of the assist gear pair 55A. On the other hand, the hub sleeve 59A is engaged with the side surface of the gear 58Aa of the assist gear pair 58A. Therefore, the assist power path 57A is switched so that the power from the assist motor 51 is not transmitted to the oil pump 32, but is switched so that the power from the assist motor 51 is transmitted to the drive wheel 10T.

[0099] In this case, the traveling output path 44A and the assist power path 57A are connected, and the assist motor 51 assists the traveling motor 41. Specifically, the output of the traveling motor 41 is transmitted to the drive wheel 10T via the traveling shaft 43A in the same manner as in the example of FIG. 11. Here, the power of the assist motor 51 is further transmitted to the traveling output path 44A via the assist power path 57A. The power of the assist motor 51 is transmitted to the traveling shaft 43A via the hub sleeve 59A that engages with the gear 58Aa of the assist gear pair 58A, and is then transmitted to the traveling output path 44A.

[0100] Fig. 13 is a diagram showing a state in which the assist power is transmitted to the oil pump in the drive system of Fig. 10. In the example of Fig. 13, the hub sleeve 59A is not engaged with the side surface of the gear 58Aa of the assist gear pair 58A. On the other hand, the hub sleeve 56A is engaged with the side surface of the gear 55Ab of the assist gear pair 55A. Therefore, the assist power path 57A is switched so that the power from the assist motor 51 is not transmitted to the driving wheel 10T, but is switched so that the power from the assist motor 51 is transmitted to the oil pump 32.

[0101] In this case, the cargo-unloading output path 34 and the assist power path 57A are connected, and the assist motor 51 assists the cargo-unloading motor 31. Specifically, the output of the cargo-unloading motor 31 is transmitted to the oil pump 32 via the cargo-unloading shaft 33 in the same manner as in the example of FIG. 11. Here, the power of the assist motor 51 is further transmitted to the cargo-unloading output path 34 via the assist power path 57A. The power of the assist motor 51 is transmitted to the cargo-unloading shaft 33 via the hub sleeve 56A that engages with the gear 55Ab of the assist gear pair 55A, and then transmitted to the cargo-unloading output path 34.

[0102] As described above, according to the configuration of the modified example of Figs. 10 to 13, the assist power path 57A can be easily configured by using two gear pairs.

[0103] Alternatively, as shown in, for example, Figs. 14 to 17, the drive system 20B may be configured without using the gear 55a of the assist gear pair 55 in the drive system 20. As shown in Fig. 14, the assist power path 57B has a planetary gear mechanism (second planetary gear mechanism) 58B provided between the output shaft of the assist motor 51 and the load output path 34, and between the output shaft of the assist motor 51 and the traveling output path 44B, and an assist gear pair (second gear pair) 55B provided between the planetary gear mechanism 58B and the load output path 34. The planetary gear mechanism 58B has a ring gear (second ring gear) 58Ba, a planetary gear (second planetary gear) 58Bb, and a sun gear (second sun gear) 58Bc. The planetary carrier of the planetary gear 58Bb is fixed to, for example, the case 22 of the gear box 21. That is, the planetary gear 58Bb is journaled on a fixed planetary carrier. As shown by the thick hook-shaped line in FIG. 14, here, the ring gear 58Ba is connected to the assist shaft 54B. The ring gear 58Ba is an input part of the power from the assist motor 51, and the power from the assist motor 51 is input to the planetary gear mechanism 58B via the ring gear 58Ba. On the outer circumferential surface of the ring gear 58Ba, external teeth 55Ba are formed which mesh with the gear 55Bb of the assist gear pair 55B on the loading output path 34 side. That is, the assist gear pair 55B forms a gear pair in which the external teeth 55Ba of the ring gear 58Ba and the gear 55Bb on the loading output path 34 side are always meshed. The gear 55Bb on the loading output path 34 side of the assist gear pair 55B is provided with a hub sleeve 56B as the loading assist switching part 52. The sun gear 58Bc is provided with a hub sleeve 59B serving as the travel assistance switching unit 53.

[0104] The operation of the drive system 20A thus configured will be described with reference to Figures 15 to 17. Figure 15 is a diagram showing a state in which the assist power is not transmitted to either the oil pump or the wheels in the drive system of Figure 14. In the example of Figure 15, similarly to the example of Figure 3 of the above embodiment, the output of the loading motor 31 is transmitted to the oil pump 32 via the loading shaft 33 without the assistance of the assist motor 51. The output of the traveling motor 41 is transmitted to the driving wheel 10T via the traveling shaft 43 without the assistance of the assist motor 51.

[0105] Fig. 16 is a diagram showing a state in which the assist power is transmitted to the wheels in the drive system of Fig. 14. In the example of Fig. 16, basically similarly to the example of Fig. 4 of the above embodiment, the assist power path 57B is switched so that the power from the assist motor 51 is not transmitted to the oil pump 32, but is switched so that the power from the assist motor 51 is transmitted to the drive wheel 10T.

[0106] In this case, the traveling output path 44B and the assist power path 57B are connected, and the assist motor 51 assists the traveling motor 41. Specifically, the output of the traveling motor 41 is transmitted to the driving wheel 10T via the traveling shaft 43 in the same manner as in the example of FIG. 3 of the above embodiment. Here, the power of the assist motor 51 is further transmitted to the traveling output path 44B via the assist power path 57B. The power of the assist motor 51 is transmitted to the ring gear 58Ba of the planetary gear mechanism 58B via the assist shaft 54B. The power of the assist motor 51 is transmitted to the sun gear 58Bc by the ring gear 58Ba rotating the sun gear 58Bc via the planetary gear 58Bb. The power of the assist motor 51 is transmitted to the assisted shaft 42 via the hub sleeve 59B engaged with the sun gear 58Bc, and is transmitted to the traveling output path 44B.

[0107] Fig. 17 is a diagram showing a state in which the assist power is transmitted to the oil pump in the drive system of Fig. 14. In the example of Fig. 17, basically similarly to the example of Fig. 5 of the above embodiment, the assist power path 57B is switched so that the power from the assist motor 51 is not transmitted to the driving wheel 10T, but is switched so that the power from the assist motor 51 is transmitted to the oil pump 32.

[0108] In this case, the load output path 34 and the assist power path 57B are connected, and the assist motor 51 assists the load motor 31. Specifically, the output of the load motor 31 is transmitted to the oil pump 32 via the load shaft 33 in the same manner as in the example of FIG. 3 of the above embodiment. Here, the power of the assist motor 51 is further transmitted to the load output path 34 via the assist power path 57B. The power of the assist motor 51 is transmitted to the ring gear 58Ba via the assist shaft 54B, and is transmitted to the gear 55Bb by rotating the gear 55Bb on the load output path 34 side with the external teeth 55Ba formed on the outer circumferential surface of the ring gear 58Ba. The power of the assist motor 51 is transmitted to the load shaft 33 via the hub sleeve 56B engaged with the gear 55Bb, and is transmitted to the load output path 34.

[0109] 14 to 17, the power from the assist motor 51 can be output to the traveling output path 44B while reducing the rotation speed by the planetary gear mechanism 58B. In addition, since one of the assist gear pair 55B is the external teeth 55Ba formed on the outer circumferential surface of the ring gear 58Ba, the axial dimension can be reduced compared to when, for example, one of the assist gear pair 55B is a separately provided gear.

[0110] In the above embodiment, a hub sleeve is provided as the cargo handling assist switching unit 52 and the traveling assist switching unit 53, but the present invention is not limited to this example. For example, instead of a hub sleeve, the cargo handling assist switching unit 52 and the traveling assist switching unit 53 may be a wet multi-plate clutch capable of cutting off rotation and torque. In addition, a synchronizer ring of a transmission used in passenger cars or the like may be interposed between the side surface of the hub sleeve and the side surface of the gear 55b or the like. Alternatively, the hub sleeve may be a dog clutch type in which no synchronizer ring is interposed.

[0111] In the above embodiment, the output control unit 63 automatically controls the cargo handling assist switching unit 52 and the traveling assist switching unit 53 by comparing the wheel rotation speed with the rotation speed threshold, the pressure of the lift cylinder 10L with the pressure threshold, and the wheel torque with the torque threshold as shown in Fig. 9, but is not limited thereto. At least one of the comparison of the wheel rotation speed with the rotation speed threshold, the comparison of the pressure of the lift cylinder 10L with the pressure threshold, and the comparison of the wheel torque with the torque threshold may be omitted. Also, instead of comparing the wheel rotation speed with the rotation speed threshold, a vehicle speed threshold may be determined, and when the vehicle speed obtained by the vehicle speed sensor is equal to or higher than the vehicle speed threshold, the cargo handling assist switching unit 52 and the traveling assist switching unit 53 may be controlled so as not to assist the cargo handling motor 31. Also, in the flowchart of Fig. 9, the processes (determination of thresholds) of S02, S04, and S06 do not have to be performed during the operation of the forklift 10. The pressure threshold, the torque threshold, and the rotation speed threshold (vehicle speed threshold) may be determined in advance at the design stage of the forklift 10 and stored in the control device 60. The load handling assist switching unit 52 and the travel assist switching unit 53 may be manually operated, for example, by using a wire that moves the hub sleeve by manual operation of the driver. For example, even if at least one comparison result is obtained from the comparison between the wheel rotation speed and the rotation speed threshold, the comparison between the pressure of the lift cylinder 10L and the pressure threshold, and the comparison between the wheel torque and the torque threshold, the load handling assist switching unit 52 and the travel assist switching unit 53 may be manually operated regardless of the comparison result. In this case, the driver can manually switch between transmitting the power from the assist motor 51 to the oil pump 32 or the driving wheel 10T.

[0112] Incidentally, even if the wheel rotation speed is equal to or higher than the rotation speed threshold value, the cargo handling assist switching unit 52 and the traveling assist switching unit 53 may be controlled to assist the cargo handling motor 31. For example, in Fig. 7, the region where the wheel rotation speed is equal to or higher than the predetermined value Th2 and is less than the maximum rotation speed of the solid line L1B is considered to be divided into a medium speed range and a high speed range, and the cargo handling motor 31 may be assisted in the medium speed range. The upper limit of the range of the medium speed range is not particularly limited as long as it is a rotation speed that is greater than the predetermined value Th2 and less than the maximum rotation speed of the solid line L1B in Fig. 7.

[0113] The assist gear pairs 55, 55A, 55B, 58A are not limited to the constant meshing type.

[0114] In the above embodiment, the forklift 10 is exemplified as an industrial vehicle, but the present invention is not limited to this. The industrial vehicle may be any vehicle that includes a cargo handling motor that drives a cargo handling device and a traveling motor that drives wheels.

[0115] At least some of the embodiments and various modified examples described above may be combined in any desired manner. [Explanation of symbols]

[0116] 10...Forklift (industrial vehicle), 10L...Lift cylinder, 14...Hydraulic sensor (pressure acquisition unit), 31...Loading motor (loading motor), 32...Oil pump, 34...Loading output path, 41...Travel motor (traveling motor), 44, 44A, 44B...Traveling output path, 51...Assist motor (assist motor), 52...Loading assist switching unit (assist power switching unit), 53...Travel assist switching unit (assist power switching unit), 55...Assist gear pair (first gear pair), 55A...Assist gear pair (third gear pair), 55B...Assist gear pair (second gear pair), 55Ba...External teeth, 56, 56A, 56B, 59, 59A, 59B...hub sleeve, 57, 57A, 57B...assist power path, 58...planetary gear mechanism (first planetary gear mechanism), 58A...assist gear pair (fourth gear pair), 58a...ring gear (first ring gear), 58B...planetary gear mechanism (second planetary gear mechanism), 58b...planetary gear (first planetary gear), 58Ba...ring gear (second ring gear), 58Bb...planetary gear (second planetary gear), 58Bc...sun gear (second sun gear), 58c...sun gear (first sun gear), 61...loading state acquisition unit (pressure acquisition unit), 63...output control unit (switching control unit).

Claims

1. An industrial vehicle including a cargo handling motor that drives a cargo handling device and a traveling motor that drives wheels, A loading output path formed between the loading motor and a loading oil pump; a driving output path formed between the driving motor and the wheels; an assisting electric motor for assisting the loading electric motor or the traveling electric motor; an assist power path formed between the assist motor and the load output path and between the assist motor and the travel output path; an assist power switching unit that switches whether power from the assist electric motor is transmitted to either the oil pump or the wheels via the assist power path.

2. the assist power path includes a first gear pair provided between an output shaft of the assist electric motor and the loading output path, and a first planetary gear mechanism provided between the output shaft of the assist electric motor and the traveling output path, 2. The industrial vehicle according to claim 1, wherein the first planetary gear mechanism has a fixed first ring gear, a first planetary gear that serves as an input part for power from the assist electric motor, and a first sun gear that serves as an output part for power to the driving output path.

3. the assist power path includes a second planetary gear mechanism provided between an output shaft of the assist electric motor and the load output path, and between the output shaft of the assist electric motor and the traveling output path, and a second gear pair provided between the second planetary gear mechanism and the load output path, the second planetary gear mechanism includes a second planetary gear journaled on a fixed planetary carrier, a second ring gear serving as an input portion for power from the assist electric motor, and a second sun gear serving as an output portion for power to the traveling output path, 2. The industrial vehicle according to claim 1, wherein an outer circumferential surface of the second ring gear is formed with external teeth that mesh with a gear of the second gear pair on the side of the load output path.

4. 2. The industrial vehicle according to claim 1, wherein the assist power path has a third gear pair provided between an output shaft of the assist motor and the loading output path, and a fourth gear pair provided between an output shaft of the assist motor and the traveling output path.

5. The industrial vehicle according to any one of claims 1 to 4, wherein the assist power switching unit has a hub sleeve provided between the assist power path and the loading output path, and a hub sleeve provided between the assist power path and the driving output path.

6. a pressure acquisition unit that acquires a pressure of a lift cylinder for loading and unloading; a switching control unit that controls the assist power switching unit based on the pressure, The industrial vehicle according to any one of claims 1 to 5, wherein the switching control unit controls the assist power switching unit to transmit power from the assist electric motor to the driving output path via the assist power path when the pressure is less than a predetermined pressure threshold.

7. a torque acquisition unit that acquires a wheel torque that drives the wheel; a switching control unit that controls the assist power switching unit based on the wheel torque, The industrial vehicle according to any one of claims 1 to 6, wherein the switching control unit controls the assist power switching unit to transmit power from the assist electric motor to the driving output path via the assist power path when the wheel torque is equal to or greater than a predetermined torque threshold value.

8. A rotation speed acquisition unit that acquires the rotation speed of the wheel; A switching control unit that controls the assist power switching unit based on the rotation speed, The industrial vehicle according to any one of claims 1 to 7, wherein the switching control unit controls the assist power switching unit so as not to transmit power from the assist electric motor to the loading output path via the assist power path when the rotation speed is equal to or higher than a predetermined rotation speed threshold.

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