WO2006109571A1

WO2006109571A1 - Hst traveling system of work machine

Info

Publication number: WO2006109571A1
Application number: PCT/JP2006/306468
Authority: WO
Inventors: Makoto Sugaya; Tsukasa Toyooka; Hidetoshi Satake; Kazuhiro Ichimura
Original assignee: Hitachi Construction Machinery Co., Ltd.
Priority date: 2005-04-05
Filing date: 2006-03-29
Publication date: 2006-10-19
Also published as: JP2006290009A; JP4606228B2

Abstract

An HST traveling system of a work machine capable of eliminating the need of a transmission and a propeller shaft and providing speeds and tractive forces suitable for various types of works without using the transmission. The capacities of two hydraulic motors (10) and (20) of an HST transmission device (30) are made equal to each other, and a speed reduction ratio twice that of a rear wheel side speed reducer (21) of a traveling device (12) and (22) is provided to a front wheel side speed reducer (11) of a traveling device (12) to set the ratio of the speed reduction ratio of the front wheel side speed reducer (11) to the speed reduction ratio of the rear wheel side speed reducer (21) to 2:1. The HST transmission device (30) comprises a changeover valve (41), a selector switch (42), and a controller (43), and can be switched between a low-speed four-wheel drive mode for driving both the traveling devices (12) and (22) and a high-speed two-wheel drive mode for driving only the rear wheel side traveling device (22).

Description

HST traveling system for work machines

Technical field

[0001] The present invention relates to an HST traveling system for work machines, and in particular, an HST (Hydro-Static Transmission) in which a hydraulic pump and a traveling motor are connected in a closed circuit, such as a rough terrain lift truck, a wheel loader, and a wheeled hydraulic excavator. It relates to an HST traveling system for work machines with a hydraulic traveling circuit.

Background art

[0002] As described in, for example, Japanese Patent Application Laid-Open No. 5-306768, a conventional HST traveling system has one hydraulic pump and one hydraulic motor connected in a closed circuit, and the traveling device is driven by the one hydraulic motor. It is common to do. In this case, the hydraulic motor is connected to the front and rear wheels via a transmission and a propeller shaft, and simultaneously drives the front and rear wheels by rotating the propeller shaft.

[0003] As another HST traveling system, for example, as described in JP-A-11-166623 and JP-A-11-230333, one hydraulic pump is connected in parallel to two hydraulic motors in a closed circuit, and 2 Some drive the driving device with two hydraulic motors. In this case as well, the two hydraulic motors are connected to the front and rear wheels via a speed reducer and a propeller shaft, and simultaneously drive the front and rear wheels by rotating the propeller shaft. Also, one hydraulic motor is connected to the speed reducer via a clutch, and can be switched between low speed (high torque) mode (clutch ON) and high speed mode (clutch OFF) by controlling the clutch ONZOFF. The machine is unnecessary.

[0004] On the other hand, as another HST traveling system, one hydraulic pump is connected in parallel to two hydraulic motors in a closed circuit, two hydraulic motors are connected to the front wheels and the rear wheels, respectively, and the front wheels and the rear wheels are separated. One driven by a hydraulic motor is known. For example, in the publication of Japanese Laid-Open Patent Publication No. 2000-1127, in a lawn mower HST traveling system, the front and rear wheels are set to high torque at low speeds at low speed, and the front wheels are set to low torque and the rear wheels are set to high torque at high speeds. By using wheel drive, the braking force is transmitted hydraulically to the front wheels when driving, and the rear wheels are driven when turning. The two-wheel drive prevents the front wheels from dragging when turning. In order to change the driving torque of the front wheel hydraulic motor, a constant ratio diversion valve is provided at the oil supply / discharge oil port of the hydraulic pump, a shuttle valve is provided between the main lines on the front wheel side hydraulic motor side, and a high pressure relief valve is provided on the output side of the shuttle valve. A proof valve and a low-pressure relief valve are connected in parallel.

[0005] In GB2136371A, in an agricultural machine HST traveling system, one of two hydraulic motors is configured as a small-capacity auxiliary motor, and this auxiliary motor is connected to the front or rear wheel via a clutch and a speed reducer. An on-off valve is provided between the hydraulic pump and the auxiliary motor, and the connection between the auxiliary motor and the hydraulic pump or the auxiliary motor and the wheel is cut off by simultaneously switching the clutch and the on-off valve.

[0006] Patent Document 1: Japanese Patent Laid-Open No. 5-306768

Patent Document 2: Japanese Patent Laid-Open No. 11-166623

Patent Document 3: Japanese Patent Laid-Open No. 11-230333

Patent Document 4: Japanese Patent Laid-Open No. 2000-1127

Patent Document 5: GB2136371A

Disclosure of the invention

Problems to be solved by the invention

[0007] However, the above-described conventional technique has the following problems.

[0008] In a general HST traveling system described in JP-A-5-306768, a hydraulic motor is connected to front and rear wheels via a transmission and a propeller shaft, and the front and rear wheels are simultaneously rotated by rotating the propeller shaft. Since this is a drive system, a transmission and a propeller shaft are essential as a traveling device. The transmission and the propeller shaft are located on the lower side of the driving type, and the propeller shaft extends back and forth under the engine and the driver's seat and is connected to the front and rear wheels.

. For this reason, it is necessary to install the driver's seat and engine at a position and height that do not interfere with the transmission and the propeller shaft, and the vehicle height (driver's seat height) increases accordingly. However, there is a problem that workability is lowered. Another problem is that the degree of freedom in the layout of the engine, driver's seat, and other equipment is limited by the transmission and propeller shaft.

[0009] Two hydraulic pressures described in JP-A-11 166623 and JP-A-11 230333 The HST traveling system that uses a motor does not require a transmission. A propeller shaft is required, so the problem of vehicle height and layout constraints due to the propeller shaft has not been solved.

[0010] In the HST traveling system described in Japanese Patent Application Laid-Open No. 2000-1127 and GB2136371A, the front wheels and the rear wheels are driven by separate hydraulic motors, so a propeller shaft is unnecessary, and there is a problem of vehicle height and layout constraints due to the propeller shaft. There is no. The GB2136371A can be switched between a four-wheel drive that drives two hydraulic motors simultaneously by a switch operation and a two-wheel drive that drives only one of the hydraulic motors. Can be switched. However, when these conventional technologies are applied to multipurpose work machines such as rough terrain lift trucks, wheel loaders, and wheel-type hydraulic excavators, there is a problem that speeds and traction forces suitable for various working modes cannot be obtained.

[0011] For example, a force with packet work as a typical work performed by a rough terrain lift truck H

In the ST traveling system, the torque distribution (traction distribution) of the front and rear wheels is usually set to 1: 1. In this case, with a work machine with a work implement (packet, etc.) in the front part of the vehicle body, the vehicle weight during bucket work hardly applies any force to the front wheels, so the traction force during packet work is half the maximum traction force of the front and rear wheels combined. Therefore, the traction for packet work is too small. In the HST traveling system described in GB2136371A, it is possible to switch to two-wheel drive that drives only the main hydraulic motor (hydraulic motor that is not an auxiliary motor) during high-speed traveling by switch operation. However, since the capacity of the main hydraulic motor is larger than that of the auxiliary motor, the rotational speed (vehicle speed) is not twice that of the four-wheel drive state, which is insufficient as a vehicle speed for moving the vehicle at high speed.

[0012] An object of the present invention is to provide an HST traveling system for a work machine that does not require a transmission and a propeller shaft and that can obtain speed and traction force suitable for various operations without using a transmission. is there.

Means for solving the problem

(1) In order to achieve the first object, the present invention provides a hydraulic pump, a pressure connected to the hydraulic pump in a closed circuit and connected in parallel to each other, and the pressure discharged from the hydraulic pump. First and second hydraulic motors driven by oil, and a first reduction gear connected to the first hydraulic motor. Connected to the front wheel traveling device, a rear wheel traveling device connected to the second hydraulic motor via a second speed reducer, and a low-speed four-wheel drive mode for driving both the front wheel traveling device and the rear wheel traveling device. And a first control means for switching to a high-speed two-wheel drive mode for driving only the rear wheel travel device, wherein the drive torque of the front wheel travel device is set larger than the drive torque of the rear wheel travel device. To do.

In the present invention configured as described above, the front wheel traveling device and the rear wheel traveling device are driven by separate hydraulic motors, so that a propeller shaft is not required.

[0015] In addition, when the HST traveling system of the present invention is applied to a multi-purpose work machine such as a rough terrain lift truck and the towing work is performed in the low-speed four-wheel drive mode, the front-wheel and the rear-wheel four-wheel drive can be obtained. By setting the maximum traction force appropriately, the maximum traction force necessary for traction work can be obtained.

[0016] When performing packet work with low-speed four-wheel drive, the driving torque of the front wheel traveling device is set to be larger than the driving torque of the rear wheel traveling device, so the vehicle weight is mostly applied to the front wheels. It is larger than half of the maximum traction force in the low-speed four-wheel drive mode (total traction force of the front and rear wheels), and it is possible to obtain traction force suitable for packet work.

[0017] When the high-speed traveling is performed in the high-speed two-wheel drive mode, the driving torque of the front wheel traveling device is set to be larger than the driving torque of the rear wheel traveling device. The flow rate is more than double, and the rotational speed (vehicle speed) is larger than twice that in the low-speed four-wheel drive mode, and the vehicle can move at high speed.

[0018] As described above, the present invention provides a transmission (for example, a two-speed transmission) with the maximum traction force required for traction work, the traction force required for packet work (front and rear wheel traction force distribution), and the traction force required for high-speed travel. Can be achieved without using.

(2) In the above (1), preferably, the ratio of the driving torque of the front wheel traveling device and the driving torque of the rear wheel traveling device is set in a range of 2 to 3: 1.

[0020] As a result, the traction force during packet work, where most of the vehicle weight is applied to the front wheels, is 2Z3 to 3Z4 (67 to 75%) of the maximum traction force (total traction force of the front and rear wheels) in the low-speed four-wheel drive mode. A suitable traction force can be obtained.

[0021] In addition, a flow rate 3 to 4 times that in the low-speed four-wheel drive mode acts on the second hydraulic motor, and the rotational speed The degree (vehicle speed) is 3 to 4 times that of the low-speed four-wheel drive mode, and the vehicle can move at high speed.

[0022] (3) In the above (1), more preferably, the ratio of the driving torque of the front wheel traveling device to the driving torque of the rear wheel traveling device is set to 2: 1.

[0023] As a result, the traction force during packet work where most of the vehicle weight is applied to the front wheels is 2Z3 (about 65%) of the maximum traction force (total traction force of the front and rear wheels) in the low-speed four-wheel drive mode, which is suitable for packet work. Traction can be obtained.

[0024] In addition, a flow rate three times that in the low speed four-wheel drive mode acts on the second hydraulic motor, and the rotational speed (vehicle speed) is three times that in the low speed four-wheel drive mode, allowing the vehicle to move at high speed. .

[0025] (4) Further, in order to achieve the above object, the present invention provides a hydraulic pump and a hydraulic fluid connected to the hydraulic pump in a closed circuit and connected in parallel to each other and discharged from the hydraulic pump. The first and second hydraulic motors to be driven, the front wheel travel device connected to the first hydraulic motor via a first speed reducer, and the second hydraulic motor connected to the second hydraulic motor via a second speed reducer And a first control means for switching between a rear wheel traveling device, a low speed four wheel drive mode for driving both the front wheel traveling device and the rear wheel traveling device, and a high speed two wheel drive mode for driving only the rear wheel traveling device. It is assumed that the capacities of the first and second hydraulic motors are equal, and the reduction ratio of the first reduction gear is larger than the reduction ratio of the second reduction gear.

[0026] As a result, as described in (1) above, the transmission and the propeller shaft are not required, and the speed and traction force suitable for various work modes can be achieved without using a speed changer.

[0027] Further, by making the first and second hydraulic motors have the same capacity, it is possible to share parts and reduce costs.

(5) In the above (4), preferably, the ratio of the reduction ratio of the first reduction gear to the reduction ratio of the second reduction gear is set in a range of 2 to 3: 1.

[0029] As a result, the traction force during packet work where most of the vehicle weight is applied to the front wheels is 2Z3 to 3Z4 (67 to 75%) of the maximum traction force (total traction force of the front and rear wheels) in the low-speed four-wheel drive mode. A suitable traction force can be obtained.

[0030] In addition, the second hydraulic motor has a flow rate 3 to 4 times that in the low-speed four-wheel drive mode, and the rotational speed (vehicle speed) is 3 to 4 times that in the low-speed four-wheel drive mode. Can move The

[0031] (6) In the above (4), more preferably, the ratio of the reduction ratio of the first reduction gear to the reduction ratio of the second reduction gear is set to 2: 1.

[0032] As a result, the traction force during packet work where most of the vehicle weight is applied to the front wheels is 2Z3 (about 65%) of the maximum traction force (total traction force of the front and rear wheels) in the low-speed four-wheel drive mode, which is suitable for packet work. Traction can be obtained.

[0033] In addition, the second hydraulic motor has a flow rate three times that in the low-speed four-wheel drive mode, and the rotational speed (vehicle speed) is three times that in the low-speed four-wheel drive mode, allowing the vehicle to move at high speed. .

(7) Further, in the above (1) or (4), preferably, a switching valve disposed in a closed circuit connecting the hydraulic pump and the first and second hydraulic motors, and the front wheel travel A speed difference between the device and the rear wheel traveling device is detected, and when the speed difference exceeds a predetermined value, the switching valve is switched to switch the speed of the first hydraulic motor and the second hydraulic motor on the side where the rotational speed increases. And second control means for shutting off the supply of pressure oil to the hydraulic motor.

[0035] Thus, when traveling in the low-speed four-wheel drive mode, if any of the front and rear axles is idle due to changes in the road surface condition during work or the change in the axle load distribution of the front and rear wheels, the front wheels that are not idle Alternatively, it is possible to supply pressure oil only to the rear wheel side hydraulic motor, avoiding an open differential state when the wheels are idle in the low-speed four-wheel drive mode, and improving rough road running performance.

[0036] (8) In the above (1) or (4), preferably, the first control means further includes a medium-speed two-wheel drive mode for driving only the front wheel travel device, and the low-speed 4 Switching between wheel drive mode, high-speed two-wheel drive mode, and medium-speed two-wheel drive mode is possible.

[0037] As a result, in the medium-speed two-wheel drive mode, the intermediate speed and traction force can be obtained between the low-speed four-wheel drive mode and the high-speed two-wheel drive mode. Appropriate travel speed and traction force can be obtained, and not only the work efficiency is improved, but also the engine does not operate at high speed, so operator fatigue (noise, vibration) can be reduced. In addition, since work machines such as forks are located at the front of the vehicle body, the weight of the front wheels acts mainly during cargo handling work, and workability is not impaired.

The invention's effect [0038] According to the present invention, a transmission and a propeller shaft are unnecessary, and a speed and traction force suitable for various operations can be obtained without using a transmission.

[0039] Further, according to the present invention, by using the same capacity for the first and second hydraulic motors, it is possible to share parts and reduce costs.

[0040] Further, according to the present invention, it is possible to avoid the state of open def during wheel idling in the low-speed four-wheel drive mode, and to improve rough road running performance.

[0041] Further, according to the present invention, the intermediate speed and traction force between the low-speed four-wheel drive mode and the high-speed two-wheel drive mode can be obtained in the medium-speed two-wheel drive mode. The traction force is obtained and the work efficiency is improved.

Brief Description of Drawings

FIG. 1 is a hydraulic configuration diagram of an HST traveling system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the appearance of a rough terrain lift truck as an example of a work machine equipped with the HST traveling system of the present invention.

FIG. 3 is a hydraulic configuration diagram of the HST traveling system according to the first embodiment of the present invention.

FIG. 4 is a flowchart showing processing contents of the controller.

FIG. 5 is a flowchart showing the processing contents of the controller (low speed control process) when the switch is in the low speed position. Explanation of symbols

[0043] 1 Hydraulic pump

2 Engine

3, 4, 5, 6, 7, 8 Main pipeline

3a, 3b, 3c, 4a, 4b Main pipeline

10 (front wheel side) hydraulic motor

11 Reducer

12 Traveling equipment

13 axles

14 Front wheels

20 (Rear wheel side) Hydraulic motor 21 Reducer

22 Traveling equipment

23 axles

24 Rear wheel

30 HST transmission

41 Switching valve

41 A selector valve

42 selector switch

42A selector switch

43 Controller

43A controller

51, 52 Rotational speed sensor

BEST MODE FOR CARRYING OUT THE INVENTION

[0044] Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a hydraulic configuration diagram showing an HST traveling system for a work machine according to a first embodiment of the present invention.

In FIG. 1, the HST travel system of the present embodiment includes HST transmission 30, front wheel travel device 12, and rear wheel travel device 22.

[0047] The HST transmission 30 includes a main hydraulic pump 1 driven by the engine 2 and two traveling hydraulic motors 10 and 20 driven by pressure oil discharged from the hydraulic pump 1. Hydraulic pump 1 and hydraulic motor 10 are closed circuit connected via main lines 3, 4, 5, 6; hydraulic pump 1 and hydraulic motor 20 are closed circuit connected via main lines 3, 4, 7, 8 The two hydraulic motors 10 and 20 are connected in parallel to the hydraulic pump 1. A charge pump 33 for replenishment is connected to the main pipelines 7 and 8 via check valves 34 and 35, and the pressure of the main pipeline 7 or 8 is set in the relief valve 37 provided in the discharge passage of the charge pump 33. If it becomes lower than that, the discharge oil from the charge pump 33 is supplied to the main pipeline 7 or 8.

[0048] The traveling hydraulic motors 10, 20 are connected to the traveling devices 12, 22, respectively. The front wheel traveling device 12 is connected to a reduction gear 11 to which a traveling hydraulic motor 10 is connected, and to the reduction gear 11. The rear wheel traveling device 22 includes a speed reducer 21 to which a traveling hydraulic motor 20 is connected, and an axle 23 and a rear wheel (wheel) connected to the speed reducer 21. ) 2 and 4 are configured to transmit the driving force to the road surface by wheels 14 and 24, respectively, and drive the vehicle with both driving forces!

[0049] In the HST transmission 30, the capacities of the two hydraulic motors 10, 20 are set equal. Further, in the traveling devices 12 and 22, the front wheel side reducer 11 is set larger than the rear wheel side reducer 21. Specifically, the front wheel side reducer 11 is the rear wheel side reducer 21. The ratio of the reduction ratio of the reduction gear 11 on the front wheel side and the reduction gear 21 on the rear wheel side is 2: 1.

[0050] Note that the reduction ratio ratio of 2: 1 is an example (optimal example), and if the reduction ratio of the reduction gear 11 on the front wheel side is larger than the reduction ratio of the reduction gear 21 on the rear wheel side (preferably, the front wheel side If the ratio of the reduction ratio of the reduction gear 11 and the reduction gear 21 on the rear wheel side is in the range of 2 to 3, the ratio is other than that.

[0051] The HST transmission 30 is also a control means for switching between a low-speed four-wheel drive mode that drives both the traveling devices 12 and 22, and a high-speed two-wheel drive mode that drives only the rear wheel travel device 22. Thus, a two-position switching valve (hereinafter simply referred to as a switching valve) 41 installed in the main pipelines 5 and 6, a switching switch 42 operated by an operator, and a controller 43 are provided.

[0052] The switching valve 41 is an electromagnetic switching valve having a solenoid 41a at one end. When the electrical signal applied to the solenoid 41a is OFF, the switching valve 41 is in the illustrated communication position. When the electrical signal is ON, the position force is blocked. Switch to position. The circuit state when the switching valve 41 is in the illustrated communication position is called the low-speed four-wheel drive mode, and the circuit state when the switching valve 41 is switched to the shut-off position is the high-speed two-wheel drive mode.

[0053] The switching switch 42 can be switched between two positions, low speed and high speed. When the switching switch 42 is in the low speed position, the controller 43 turns off the electrical signal, and the switching switch 42 switches to the high speed position. The controller 43 turns on the electrical signal and outputs it to the switching valve 41.

[0054] The hydraulic pump 1 is provided with a known tilt amount control means (not shown), and the tilt amount (capacity) of the hydraulic pump 1 is increased in accordance with the increase in the rotational speed of the engine 2, thereby smoothly increasing the pump discharge flow rate. Let The increase in the pump discharge flow rate increases the rotational speed of travel motors 10 and 20. And the vehicle speed increases. The rotational speed of the engine 2 is adjusted by operating an accelerator pedal (not shown).

[0055] The traveling motors 10, 20 are provided with a known tilt amount control means (not shown). When the load pressure is lower than the set pressure, the travel motors 10 and 20 are in a small tilt (small capacity), and when the load pressure is higher than the set pressure, the tilt is large. Automatically switches to (large capacity). The set pressure is the same value for the two travel motors 10, 20.

[0056] FIG. 2 is a diagram showing an appearance of a rough terrain lift truck (also called a telescopic handler), which is a typical example of a multi-purpose work machine, as an example of a work machine on which the HST traveling system of the present embodiment is mounted. is there.

In FIG. 2, the rough terrain lift truck includes a vehicle body 41, a cab 42 located on the vehicle body 41, and an extendable boom 43 attached to the vehicle body 41 so that the side portion of the cab 42 can be raised and lowered. And an attachment mounting portion 44 rotatably attached to the tip of the boom 43, and a fork 45 used for cargo handling work, which is one of the attachments attached to the attachment mounting portion 44, The boom 43, the attachment mounting portion 44, and the fork 45 constitute a working device. Although not shown in the drawing, hydraulic actuators are attached to the boom 43, the attachment mounting portion 44, and the fork 45, and each working member is driven by the hydraulic actuator. The vehicle body 41 has a front wheel 14 and a rear wheel 24 attached thereto.

The imaginary line in FIG. 2 shows a state where the boom 43 is raised and a state where the boom 43 is raised and extended. In this case, even if the boom 43 is raised, the fork 45 does not change its position due to the linking action of the attachment mounting portion 44.

Next, the function and effect of the present embodiment configured as described above will be described.

[0060] When the switching switch 42 is in the low speed position and the switching valve 41 is in the illustrated communication position, it is in the low speed four-wheel drive mode, and pressure oil is supplied from the hydraulic pump 1 to the two hydraulic motors 10 and 20. It becomes a state. In this state, equal driving pressure is generated in the two hydraulic motors 10 and 20, and the driving torque of the hydraulic motors 10 and 20 is equal to the capacity and driving pressure. The drive torque generated by the hydraulic motors 10 and 20 is the same because it is expressed as a product. However, since the ratio of the reduction ratio between the front wheel side reducer 11 and the rear wheel side reducer 21 is 2: 1, the torque for driving the vehicle is the front wheel 14 (front wheel drive device 12) for the rear wheel 24 (rear wheel). Run 2 times that of the line device 22). At this time, since the rotational speeds of the front and rear wheels 14 and 24 are the same, a flow rate twice that of the rear wheel side hydraulic motor 20 acts on the front wheel side hydraulic motor 10, resulting in a front and rear 2: 1 ratio. It is possible to run with the traction force distributed.

[0061] When the switching switch 42 is operated to the high speed position and the switching valve 41 is switched to the cutoff position, the high speed two-wheel drive mode is established, and only the hydraulic motor 20 on the rear wheel side is supplied with one hydraulic pump. The pressure oil is supplied. In this state, since all the pressure oil from the hydraulic pump 1 flows into the hydraulic motor 20 on the rear wheel side, a rotation speed (vehicle speed) that is three times that of the low-speed four-wheel drive mode can be obtained. In other words, the speed difference is three times that of the low-speed four-wheel drive mode without using a transmission.

At this time, the main pipelines 5 and 6 of the front wheel side hydraulic motor 10 communicate with each other, so that the front wheel side hydraulic motor 10 rotates as the front wheel 14 rotates. Further, since the traveling drive torque at this time is given only by the hydraulic motor 20 on the rear wheel side, it becomes 1Z3 of the drive torque in the low-speed four-wheel drive mode. In other words, the traction force in the high-speed two-wheel drive mode is 1Z3, which is the traction force (maximum traction force) obtained in the low-speed four-wheel drive mode.

[0063] The rough terrain lift truck is a multi-purpose work machine and can perform various operations such as towing work, packet work, and cargo handling work. Towing work is the work of towing and moving a towed object such as a trailer at the rear of the vehicle body. Packet work is excavation work by exchanging attachments with packets and pressing the packets against the excavated object such as natural ground with running force (traction force). After excavation, raise the packet, move the car body, and release it to the truck. The cargo handling operation is an operation in which a fork 45 shown in the figure is loaded and moved. It is also necessary to travel at high speed when the vehicle is moving.

[0064] According to the present embodiment, the towing operation is performed in the low-speed four-wheel drive mode, and the vehicle movement at high speed is performed in the high-speed two-wheel drive mode. Carrying work is carried out in either low-speed four-wheel drive mode or high-speed two-wheel drive mode depending on the situation at that time.

[0065] Here, in a working machine such as a rough terrain lift truck, generally, the maximum traction force during towing is set to 90 to LOO% of the vehicle body weight ratio, and the traction force at the maximum speed is the vehicle weight ratio. Is set to 20-30%. The conventional HST traveling system uses a transmission (transmission) and a propeller shaft, and drives one or two hydraulic motors simultaneously with one or two hydraulic motors. . In such an HST traveling system, in order to achieve both the maximum traction force at towing and the traction force at the maximum speed, a two-speed transmission with a speed ratio between 3 and 4 is used. Was. When performing towing work or packet work, switch the transmission to the low-speed gear, and switch the transmission to the high-speed gear when moving (running) the vehicle.

[0066] However, in a working machine such as a rough terrain lift truck, the maximum traction force that can be obtained with a low-speed gear is essential for traction work, but the maximum traction force is excessive for packet work. In addition, because high-speed driving is used when moving between work sites, the four-wheel drive system without a center differential for the purpose of improving rough road running performance was inefficient.

[0067] In addition, when the HST traveling system described in Japanese Patent Application Laid-Open No. 2000-1127 and GB2136371A is applied to a work machine such as a rough terrain lift truck, consideration is given to torque distribution (traction force distribution) of the front and rear wheels. Therefore, sufficient traction force cannot be obtained during packet work. In other words, when the torque distribution of the front and rear wheels (traction force distribution) is not considered, the torque distribution of the front and rear wheels is usually set to 1: 1. In this case, with a work machine with a work implement (bucket, etc.) in the front of the vehicle body, the vehicle weight during packet work hardly applies any force to the front wheels, so the tractive force during packet work is half of the maximum tractive force, and packet work The traction force is too small.

[0068] In the present embodiment, as described above, in the low-speed four-wheel drive mode, it is possible to travel in the traction force distribution state of front and rear 2: 1, so that the maximum traction force required by the front and rear wheels 14 and 24 is large in traction work. can get. In addition, in a work machine with a work machine (packet, etc.) in the front part of the vehicle body, the vehicle weight during bucket work hardly applies any force to the front wheels, so it is sufficient that only about 60% of the driving force is generated only on the front wheels ( It is useless to generate driving force on the rear wheels). The driving torque of the front wheel 14 by the hydraulic motor 10 is 2Z3 of the total driving torque of the front and rear wheels by the two hydraulic motors 10, 20, so at least due to the front wheel 14 during packet work where a considerable part of the vehicle weight is applied to the front wheel The traction force is about 65% of the maximum traction force of 2Z3, and both traction work and packet work can be performed with appropriate traction force.

[0069] Further, in the high-speed two-wheel drive mode, it is possible to travel at a speed three times that of the low-speed four-wheel drive mode with only the rear wheels 24, and good traveling performance is obtained. [0070] As described above, according to the present embodiment, the front wheel traveling device 12 and the rear wheel traveling device 22 are driven by the separate hydraulic motors 10, 20, so that a propeller shaft is not required.

[0071] Also, the maximum traction force required for traction work, the traction force required for packet work (front and rear wheel traction force distribution), and the traction force required for high-speed driving without using a transmission (for example, 2-speed transmission) Can be achieved.

[0072] Furthermore, by making the front and rear wheel hydraulic motors 10, 20 have the same capacity, it is possible to share parts and reduce costs.

[0073] As described above, the reduction ratio of the front wheel side reduction gear 11 and the rear wheel side reduction gear 21 is 2

: Not limited to 1, basically, the reduction ratio of the reduction gear 11 on the front wheel side only needs to be set larger than the reduction ratio of the reduction gear 21 on the rear wheel side, and preferably on the front wheel side. The reduction gear 11 has a reduction ratio of 2 to 3 times that of the reduction gear 21 on the rear wheel side, and the ratio of the reduction ratio between the reduction gear 11 on the front wheel side and the reduction gear 21 on the rear wheel side is 2 to 3: 1. It ’s good.

[0074] By setting the reduction ratio of the reducer 11 on the front wheel side to be larger than the reduction ratio of the reducer 21 on the rear wheel side, when performing packet work in the low-speed four-wheel drive mode, the drive torque of the front wheel travel device is Because it is greater than the driving torque of the rear wheel drive device, most of the vehicle weight is applied to the front wheels.The traction force during packet work is greater than half of the maximum traction force, and the front wheel side reducer 11 and the rear wheel side reducer 21 Compared with the 1: 1 reduction ratio ratio, the traction force in packet work is optimized. In addition, when high-speed driving is performed in the high-speed two-wheel drive mode, the flow rate of the rear wheel side hydraulic motor 20 is larger than twice that in the low-speed four-wheel drive mode, and the rotational speed (vehicle speed) is low. Compared to the case where the reduction ratio of the front wheel reducer 11 and the rear wheel reducer 21 is 1: 1, the vehicle travels at a higher speed than in the four-wheel drive mode. It is out.

[0075] Also, by setting the ratio of the reduction ratio of the front wheel side reducer 11 and the rear wheel side reducer 21 to 2 to 3: 1, the traction force during packet work where most of the vehicle weight is applied to the front wheels Is 2Z3 ~ 3Z4 (67 ~ 75%) of maximum traction force in low speed 4 wheel drive mode, compared to the case where the reduction ratio ratio of the reducer 11 on the front wheel side and the reducer 21 on the rear wheel side is 1: 1, The traction of packet work is optimized. In addition, the hydraulic motor 20 on the rear wheel side has a flow rate 3 to 4 times that in the low-speed four-wheel drive mode, and the rotational speed (vehicle speed) is 3 to 4 times that in the low-speed four-wheel drive mode. The vehicle can move at a higher speed than when the reduction gear ratio of the reduction gear 11 and the reduction gear 21 on the rear wheel side is 1: 1.

[0076] As described above, use a transmission (for example, 2-speed transmission) to obtain the maximum traction force required for traction work, the traction force required for packet work (front and rear wheel traction force distribution), and the traction force required for high-speed travel. Can be achieved without.

[0077] A second embodiment of the present invention will be described with reference to Figs. In FIG. 3, members equivalent to those in FIG. 1 are given the same reference numerals.

In FIG. 3, the HST travel system of the present embodiment includes an HST transmission 30A, a front wheel travel device 12, and a rear wheel travel device 22.

[0079] In the HST transmission 30A, the capacities of the two hydraulic motors 10, 20 are set equal. Further, in the traveling devices 12 and 22, the front wheel side reducer 11 is set larger than the rear wheel side reducer 21. Specifically, the front wheel side reducer 11 is the rear wheel side reducer 21. The ratio of the reduction ratio of the reduction gear 11 on the front wheel side and the reduction gear 21 on the rear wheel side is 2: 1. In this case as well, the ratio of the reduction ratio is such that the reduction ratio of the reduction gear 11 on the front wheel side is larger than the reduction ratio of the reduction gear 21 on the rear wheel side (preferably, the reduction gear 11 on the front wheel side and the reduction gear on the rear wheel side) (If the ratio of the reduction ratio of 21 is in the range of 2 to 3: 1), other ratios may be used.

[0080] The HST transmission 30A includes a main pipeline 3a on the hydraulic pump 1 side and separate main pipelines 3b and 3c on the main pipelines 5 and 7 side instead of the main pipeline 3 in FIG. 6 and 8 are provided with main pipelines 4a and 4b connected in parallel to the main pipeline 4, and instead of the switching valve 41 in FIG. 1, between the main pipelines 3a, 4a and 4b and the main pipelines 3b and 3c. Equipped with a 3-position switching valve (hereinafter simply referred to as switching valve) 41A.

[0081] Further, the HST transmission 30A includes a switching switch 42A and a controller 43A in place of the switching switch 42 and the controller 43 in FIG. 1, and the rotational speeds (axle speeds) of the axles 13 and 23 of the traveling devices 12 and 22. ), And the detection signals of the rotation speed sensors 51 and 52 are input to the controller 43A.

[0082] The switching valve 41A is an electromagnetic switching valve having solenoids 41Aa and 4 lAb at both ends. When both electrical signals applied to the solenoids 41Aa and 41Ab are OFF, the switching valve 41A is at the first position A shown in the figure. When the electrical signal applied to the solenoid 41Aa on the right side of the figure is turned ON, the position is switched from the position shown in the figure to the second position B on the right side of the figure, and when the electrical signal applied to the solenoid 41Ab on the left side of the figure is turned ON, the position shown in FIG. Switch to position 3 on the left side of the figure. When the switching valve 41A is in the first position A, the main pipeline 3a communicates with the main pipelines 3b, 3c, and the oil discharged from the hydraulic pump 1 is supplied to the two hydraulic motors 10, 20, and the two hydraulic motors 10 and 20 rotate to drive both front wheel 14 and rear wheel 24. That is, the low-speed four-wheel drive mode is set. When the switching valve 41A switches to the second position B, the main pipe line 3a and the main pipe line 3c communicate with each other, the main pipe line 4a and the main pipe line 3b communicate with each other, and only the hydraulic motor 20 on the rear wheel side is connected to the hydraulic pump 1 When the pressure oil is supplied, only the rear wheel 24 is driven, and the hydraulic motor 10 on the front wheel side rotates with the rotation of the front wheel 14 because the main pipelines 5 and 6 communicate with each other. That is, it becomes a high-speed two-wheel drive mode. When the switching valve 41A switches to the third position C, the main pipe line 3a and the main pipe line 3b communicate with each other, the main pipe line 4b and the main pipe line 3c communicate with each other, and only the hydraulic motor 10 on the front wheel side is connected to the hydraulic pump 1 Pressure oil is supplied, and only the front wheel 14 is driven, and the hydraulic motor 20 on the rear wheel side rotates with the rotation of the rear wheel 24 because the main pipelines 7 and 8 communicate with each other. This state is called the medium-speed two-wheel drive mode.

[0083] Switching switch 42A can be switched to three positions, low speed, high speed, and medium speed, and controller 43A switches switching valve 41A based on the signal from switching switch 42A and the detection signals from rotational speed sensors 51 and 52. To control.

FIG. 4 is a flowchart showing the processing contents of the controller 43A.

[0085] The controller 43A determines the position of the switching switch 42A based on the signal from the switching switch 42A (step S10). When the switching switch 42A is in the low speed position, the controller 43A performs low speed control processing ( (Step S20), when the switching switch 42A switches to the high speed position, the electrical signal applied to the solenoid 41 Aa of the switching valve 41 A is turned ON to switch the switching valve 41 A to the second position B (Step S30), and the switching switch 42A When switching to the medium speed position, the electric signal applied to the solenoid 41Ab of the switching valve 41A is turned ON and the switching valve 41A is switched to the third position C (step S40). In the low speed control process when the switching switch 42A is in the low speed position, the speed difference between the axle 13 of the front wheel traveling device 12 and the axle 23 of the rear wheel traveling device 22 is detected based on the signals from the rotational speed sensors 51 and 52. When this speed difference is below a predetermined value, The electrical signal given to solenoid 41 Aa, 4 lAb of switching valve 41 A is turned OFF, and if the speed difference exceeds a predetermined value, the electrical signal given to either solenoid 41Aa, 41Ab is turned ON, and hydraulic motor 10, Switch the switching valve 41 A between the second position B and the third position C so as to cut off the supply of pressure oil to the hydraulic motor with the higher rotational speed out of 20.

FIG. 5 is a flowchart showing details of the low speed control process.

The controller 43A determines the speed difference AS (ΔS between the rotational speed of the axle 13 of the front wheel travel device 12 and the rotational speed of the axle 23 of the rear wheel travel device 22 based on the signals from the rotational speed sensors 51 and 52. = Front wheel axle speed-rear wheel axle speed) (step S 100), and if this speed difference Δ S is less than or equal to the predetermined value, the process ends (step S120), and the solenoid 41 A a, 4 Turn off all electrical signals applied to the lAb. When the speed difference ΔS exceeds the predetermined value, it is further determined whether the speed difference ΔS is a negative force (that is, whether the rear wheel axle speed is larger than the front wheel axle speed) (Step S130), Yes (That is, if the rear wheel axle speed is greater than the front wheel axle speed), the electrical signal applied to the solenoid 41Ab of the switching valve 41A is turned ON to switch the switching valve 41A to the third position C (step S140). If there is (that is, if the front axle speed is greater than the rear axle speed), the electrical signal applied to the solenoid 41Aa of the switching valve 41A is turned ON to switch the switching valve 41A to the second position B (step S150). In step SI10, an appropriate value close to 0 is set as the predetermined value in consideration of the speed fluctuation of the front and rear wheels during normal driving.

[0088] In the present embodiment configured as described above, the operator operates the switching switch 42A to the medium speed position, so that the medium speed two wheel drive is performed in addition to the low speed four wheel drive mode and the high speed two wheel drive mode. The mode can be selected.

That is, when the switching switch 42A is in the low speed position and the switching valve 41A is in the first position A shown in the figure, the low speed four-wheel drive mode is set, the switching switch 42A is operated to the high speed position, and the switching valve 4 1 When A is switched to the indicated position force 2nd position B, the high-speed two-wheel drive mode is set, and the changeover switch 42A is operated to the medium speed position and the changeover valve 41A is also switched to the 3rd position C. Medium speed two-wheel drive mode.

[0090] In the low-speed four-wheel drive mode, as described above, the ratio of the reduction ratio between the front wheel side reduction gear 11 and the rear wheel side reduction gear 21 is 2: 1. Is the rear wheel hydraulic mode As a result, the vehicle can run with a traction force distribution of 2: 1 front and back. In the high-speed two-wheel drive mode, all the hydraulic fluid from the hydraulic pump 1 flows into the hydraulic motor 20 on the rear wheel side, so the rotational speed (vehicle speed) is three times that of the four-wheel drive state in the low-speed four-wheel drive mode. can get.

[0091] In the medium-speed two-wheel drive mode, all the hydraulic fluid from the hydraulic pump 1 flows into the front-wheel hydraulic motor 10, so it is 1.5 (3Z2) times faster than the low-speed four-wheel drive mode, and the high-speed two-wheel drive mode. The rotation speed (vehicle speed) of 1Z2 can be obtained. Further, since the traveling drive torque at this time is given only by the hydraulic motor 10 on the front wheel side, it becomes 2Z3 of the drive torque in the low-speed four-wheel drive mode. In other words, the traction force in the medium-speed two-wheel drive mode is 2Z3, which is the traction force (maximum traction force) obtained in the low-speed four-wheel drive mode.

As described above, the rough terrain lift truck has various operations such as a towing operation, a packet operation, and a cargo handling operation. When the HST traveling system of this embodiment is applied to a rough terrain lift truck, the towing operation is performed in the low-speed four-wheel drive mode, the vehicle movement at high speed is performed in the high-speed two-wheel drive mode, and the cargo handling operation is performed at the medium speed 2 Perform in wheel drive mode. In this case, in the towing operation, the bucket operation, and the vehicle movement at a high speed, an appropriate traction force and vehicle speed can be obtained in the same manner as described in the first embodiment.

[0093] Also, in the conventional HST traveling system using a two-speed transmission (transmission), when carrying out cargo handling work, it is necessary to select whether the transmission shifts from the low speed gear to the high speed gear. I was strong. However, when low-speed gears were selected, the gear ratio focused on traction force for heavy traction work, so the speed was insufficient, and the engine operated at high speed, resulting in poor efficiency. In addition, when high-speed gears were selected, the maximum speed was emphasized, and conversely, the traction force was insufficient. Therefore, the speed and traction force to drive the machine efficiently could not be obtained.

[0094] In the present embodiment, in the medium-speed two-wheel drive mode in which only the front wheels 14 are driven, the speed and traction force between the low-speed four-wheel drive mode and the high-speed two-wheel drive mode (the low-speed four-wheel drive mode). 3Z2 times, 1Z2 rotation speed (vehicle speed) in the high-speed two-wheel drive mode and 2 Z3 in the low-speed four-wheel drive mode, and twice the traction force in the high-speed two-wheel drive mode). The operator's fatigue (noise and vibration) can be reduced. In addition, because work machines such as forks are located in the front part of the vehicle body, the weight of the vehicle acts mainly on the front wheels during cargo handling work, which may impair workability. With it.

[0095] Also, in this embodiment, when traveling in the low-speed four-wheel drive mode, if any of the front and rear axles is idle due to a change in the road surface condition during work and the axle load distribution of the front and rear wheels, The controller 43 receives the information from the rotational speed sensors 51 and 52, judges the differential state, drives the switching valve 41A, and causes the idling to occur in the hydraulic motor on the front or rear wheel side. Only supply pressure oil. By such switching control of the switching valve 41A, it is possible to avoid an open differential state at the time of wheel idling in the low-speed four-wheel drive mode, and improve rough road running performance.

[0096] As described above, according to the present embodiment, the same effects as those of the first embodiment can be obtained, and the medium-speed two-wheel drive mode can be used in the low-speed four-wheel drive mode and the high-speed two-wheel drive mode. Since almost the intermediate speed and traction force can be obtained, it is possible to obtain an appropriate traveling speed and traction force for cargo handling work, etc., and to improve work efficiency.

[0097] Further, it is possible to avoid the open differential state at the time of wheel idling in the low-speed four-wheel drive mode, and to improve rough road running performance.

In the above embodiment, the capacities of the two hydraulic motors 10 and 20 are made equal, and the reduction ratio of the reduction gear 11 on the front wheel side is larger than the reduction ratio of the reduction gear 21 on the rear wheel side (preferably (2-3: 1, more preferably 2: 1), but the purpose is to obtain an appropriate traction distribution between the front and rear wheels by the hydraulic motor and speed reducer. Other configurations may be adopted as long as they can be set larger than the driving torque of the wheel traveling device. For example, the reduction ratio of the reduction gear 11 on the front wheel side and the reduction ratio of the reduction gear 21 on the rear wheel side are the same (the reduction ratio ratio is 1: 1), and the capacity of the hydraulic motor 10 on the front wheel side is the hydraulic pressure on the rear wheel side. It may be larger than the capacity of the motor 20 (or the reduction ratio ratio is preferably set to 2-3: 1, more preferably 2: 1), and the combination of the selection of the reduction ratio and the selection of the capacity results. Specifically, the driving torque of the front wheel traveling device may be larger than the driving torque of the rear wheel traveling device.

[0099] In the second embodiment, the switching valve 41A is provided when the switching switch 42A has three positions of low speed, high speed, and medium speed, and an open differential at the time of wheel idling in the low speed four-wheel drive mode is provided. However, such control may be applied in the first embodiment. In this case, the switching valve 41 and the controller 43 in FIG. 1 of the first embodiment are switched as shown in FIG. Instead of the valve 41A and the controller 43A, the low speed control process shown in Fig. 5 should be performed when the changeover switch 42 is in the low speed position on the controller 43A!

In the first and second embodiments, the front wheel side hydraulic motor 10 and the speed reducer 11 are directly connected. However, a clutch is provided between the front wheel side hydraulic motor 10 and the speed reducer 11 so that a switching valve is provided. 4 1, 41A can be switched to the position where the hydraulic pump 1 and hydraulic motor 10 are disconnected (disengaged position or second position B) and the clutch can be turned off at the same time. This allows the hydraulic motor 10 to run in high-speed two-wheel drive mode. Since there is no need to move around, the driving load is reduced and energy loss can be reduced.

Claims

The scope of the claims

[1] Hydraulic pump (1),

First and second hydraulic motors (10, 20) connected to the hydraulic pump in a closed circuit and connected in parallel to each other and driven by pressure oil discharged from the hydraulic pump;

A front wheel travel device (12) connected to the first hydraulic motor via a first speed reducer (11), and a rear wheel travel device connected to the second hydraulic motor via a second speed reducer (21) (22), and a first control means for switching between a low-speed four-wheel drive mode for driving both the front-wheel travel device and the rear-wheel travel device and a high-speed two-wheel drive mode for driving only the rear-wheel travel device (41, Four

2,43)

An HST traveling system for a work machine, wherein a driving torque of the front wheel traveling device is set larger than a driving torque of the rear wheel traveling device.

[2] In the HST traveling system for a work machine according to claim 1,

An HST traveling system for a working machine, wherein a ratio between a driving torque of the front wheel traveling device (12) and a driving torque of the rear wheel traveling device (22) is set in a range of 2 to 3: 1.

[3] In the working machine HST traveling system according to claim 1,

A working machine HST traveling system, wherein a ratio of a driving torque of the front wheel traveling device (12) and a driving torque of the rear wheel traveling device (22) is set to 2: 1.

[4] Hydraulic pump (1),

A front wheel travel device (12) connected to the first hydraulic motor via a first speed reducer (11), and a rear wheel travel device connected to the second hydraulic motor via a second speed reducer (21) (22), and a first control means for switching between a low-speed four-wheel drive mode for driving both the front-wheel travel device and the rear-wheel travel device and a high-speed two-wheel drive mode for driving only the rear-wheel travel device (41, 4 2,43)

An HST traveling system for a working machine, wherein the capacities of the first and second hydraulic motors are made equal, and a reduction ratio of the first reduction gear is made larger than a reduction ratio of the second reduction gear.

[5] In the working machine HST traveling system according to claim 4, A working machine HST traveling system, wherein a ratio of a reduction ratio of the first reduction gear (11) and a reduction ratio of the second reduction gear (21) is set in a range of 2 to 3: 1.

[6] In the HST traveling system for the work machine according to claim 4,

A working machine HST traveling system, wherein a ratio of a reduction ratio of the first reduction gear (11) and a reduction ratio of the second reduction gear (21) is set to 2: 1.

[7] In the HST traveling system for a work machine according to claim 1 or 4,

A switching valve (41A) disposed in a closed circuit connecting the hydraulic pump (1) and the first and second hydraulic motors (10, 20);

A speed difference (ΔS) between the front wheel travel device (12) and the rear wheel travel device (22) is detected, and when the speed difference exceeds a predetermined value, the switching valve is switched to switch the first hydraulic motor and A work further comprising a second control means (41A, 43A, 51, 52) for shutting off the supply of pressure oil to the hydraulic motor on the side of the higher rotational speed of the second hydraulic motor. Mechanical HST traveling system.

[8] In the HST traveling system for a work machine according to claim 1 or 4,

The first control means (41, 42, 43) further has a medium-speed two-wheel drive mode for driving only the front wheel travel device (12), and includes the low-speed four-wheel drive mode and the high-speed two-wheel drive mode. An HST traveling system for work machines, which can be switched to either medium speed or two-wheel drive mode.