JP7545863B2 - Work vehicles - Google Patents

Description

The present invention relates to a work vehicle equipped with a continuously variable speed drive system.

Some work vehicles, such as wheel loaders, are equipped with a variable-speed travel drive system that allows for smooth starting and stopping. Known types of variable-speed travel drive systems include the HST (hydraulic static transmission) type or HMT (hydraulic mechanical transmission) type, which converts hydraulic pressure generated by driving a hydraulic pump with the engine into rotational force with a hydraulic motor, and the EMT (electronically mechanical transmission) type, which converts electric power generated by driving a generator with the engine into rotational force with an electric motor.

For example, Patent Document 1 discloses a bulldozer equipped with an HST device as a continuously variable transmission, a controller that controls the speed change of the HST device, a shift switch that changes the gear ratio of the HST device, and a shift mode change switch that changes the mode of speed change by the shift switch between a first mode in which the gear ratio is changed in stages and a second mode in which the gear ratio is changed in stages set in smaller increments than in the first mode.

In this bulldozer, the shift switch is located above the joystick-type travel lever, making it possible to operate the shift switch while operating the travel lever. The shift mode changeover switch is located on the right side of the monitor panel located in front of the driver's seat.

The controller includes a vehicle speed setting section that sets a target vehicle speed based on a gear shift operation signal detected by operating the shift switch and a mode signal indicating the mode detected by switching the shift mode switch. In this vehicle speed setting section, when the shift mode switch is switched to the first mode, a target vehicle speed is set that changes the gear ratio by one step each time the shift switch is operated, and when the shift mode switch is switched to the second mode, a target vehicle speed is set that changes the gear ratio continuously by a value corresponding to the operation time of the shift switch. This allows for rapid, finely tuned, stepless gear changes that take advantage of the characteristics of the HST.

Patent No. 4956001

The bulldozer described in Patent Document 1 has a shift switch located above the travel lever, which allows the operator to easily operate the travel lever and shift switch simultaneously without taking his or her hand off the travel lever. However, there is a possibility that the operator may mistakenly operate the shift switch when operating the travel lever. For example, when a work vehicle equipped with a snow removal attachment enters an intersection, the attachment must be moved from the shoulder of the road toward the center while decelerating. In this case, if the shift switch is mistakenly operated, the vehicle speed cannot be limited at the timing intended by the operator.

The object of the present invention is to provide a work vehicle that can quickly limit the vehicle speed at the timing intended by the operator, regardless of the amount of depression of the accelerator pedal.

In order to achieve the above object, the present invention provides a vehicle body provided with a plurality of wheels, a working implement attached to a frame constituting the vehicle body, a cab mounted on the frame, a working implement operating device provided on one of the left and right sides of the driver's seat in the cab for operating the working implement, an engine mounted on the vehicle body, a variable displacement type traveling hydraulic pump driven by the engine, a variable displacement type traveling hydraulic motor connected in a closed circuit to the traveling hydraulic pump and transmitting the driving force of the engine to the plurality of wheels, and a controller for controlling each of the traveling hydraulic pump and the traveling hydraulic motor. and a mode switching device for switching a mode that limits an upper limit of the traveling speed of the vehicle body, and an upper limit vehicle speed setting device for setting the upper limit of the traveling speed of the vehicle body, wherein when the mode is switched by the mode switching device to a limit mode that limits the upper limit of the traveling speed of the vehicle body and the work implement operation device is operated , the controller controls the displacement volume of the traveling hydraulic pump or the displacement volume of the traveling hydraulic motor so that the upper limit of the traveling speed of the vehicle body becomes the setting value set by the upper limit vehicle speed setting device.

According to the present invention, the vehicle speed can be quickly limited at the timing intended by the operator, regardless of the amount of depression of the accelerator pedal. Problems, configurations, and effects other than those described above will become clear from the description of the embodiment below.

1 is an external side view showing one configuration example of a wheel loader according to each embodiment of the present invention. FIG. FIG. 2 is a top view of the wheel loader with the plow attached. This is a top view of the inside of the cab. FIG. 2 is an enlarged view of the devices arranged in front of the driver's seat. FIG. 4 is a perspective view showing an example of a configuration of a first operating lever and a second operating lever. 1 is a system configuration diagram showing a configuration example of a drive system according to a first embodiment. FIG. FIG. 2 is a functional block diagram showing functions of a controller. 4 is a flowchart showing a flow of processing executed by a controller. FIG. 11 is a system configuration diagram showing a configuration example of a drive system according to a second embodiment. FIG. 13 is a system configuration diagram showing a configuration example of a drive system according to a third embodiment.

Below, as an example of one aspect of a work vehicle according to each embodiment of the present invention, a wheel loader that can perform loading and unloading operations such as digging up work objects such as soil and minerals and loading them into a loading destination such as a dump truck or hopper, as well as snow removal operations such as removing snow that has accumulated on the road surface will be described.

<Overall Configuration of Wheel Loader 1>
First, the overall configuration of a wheel loader 1 will be described with reference to Figs.

Figure 1 is a side view showing the appearance of a wheel loader 1 according to each embodiment of the present invention. Figure 2 is a top view of the wheel loader 1 with a plow 22 attached.

In the following explanation, of the left-right direction of the body of the wheel loader 1, the direction of the left hand of the operator aboard the wheel loader 1 facing forward is referred to as the "left direction", and the direction of the right hand is referred to as the "right direction". Also, in the following explanation, the "left-right direction of the body" may simply be referred to as the "left-right direction", the "front-rear direction of the body" may simply be referred to as the "front-rear direction", and the "up-down direction of the body" may simply be referred to as the "up-down direction".

The wheel loader 1 is an articulated work vehicle that is steered by bending the vehicle body near the center. Specifically, a front frame 1A that constitutes the front part of the vehicle body and a rear frame 1B that constitutes the rear part of the vehicle body are connected by a center joint 10 so that they can rotate freely in the left-right direction, and the front frame 1A bends in the left-right direction relative to the rear frame 1B.

As shown in FIG. 2, the vehicle body is provided with four wheels 11, two of which are front wheels 11A, one on each side of the front frame 1A, and the remaining two wheels 11 are rear wheels 11B, one on each side of the rear frame 1B. Note that, of the four wheels 11, only the left front wheel 11A and rear wheel 11B are shown in FIG. 1.

A hydraulically driven working device 2 is attached to the front of the front frame 1A. The working device 2 has a bucket 21 as a loading and unloading tool used in loading and unloading work or a plow 22 as an attachment replaceable with the bucket 21, a working tool cylinder 23 that drives the bucket 21 or plow 22, a lift arm 24 as an arm member to the tip of which the bucket 21 or plow 22 is attached, two lift arm cylinders 25 that drive the lift arm 24, and a bell crank 26 that is rotatably connected to the lift arm 24 and forms a link mechanism between the bucket 21 or plow 22 and the working tool cylinder 23.

The base end of the lift arm 24 is rotatably attached to the front frame 1A, and as shown in FIG. 1, a bucket 21 is attached to the tip when the wheel loader 1 is performing loading and unloading operations, and as shown in FIG. 2, a plow 22 is attached to the tip when the wheel loader 1 is performing snow removal operations.

The two lift arm cylinders 25 drive the lift arm 24 by supplying hydraulic oil and extending and retracting the rods 250. The lift arm 24 rotates upward relative to the front frame 1A when each rod 250 of the two lift arm cylinders 25 extends, and rotates downward relative to the front frame 1A when each rod 250 contracts. In FIG. 1, only the lift arm cylinder 25 located on the left side of the two lift arm cylinders 25 is shown by a dashed line.

The work tool cylinder 23 drives the bucket 21 or plow 22 by supplying hydraulic oil and extending and retracting the rod 230. The bucket 21 is a work tool used to scoop up soil, minerals, etc. and dump them at a loading site or to level the ground. The extension of the rod 230 of the work tool cylinder 23 causes it to tilt (rotate upward relative to the lift arm 24), and the contraction of the rod 250 causes it to dump (rotate downward relative to the lift arm 24).

On the other hand, the plow 22 is a tool used to push snow to the roadside, and is attached to the tip of the lift arm 24 via a connecting member 220 as shown in FIG. 2. The plow 22 tilts backward when the rod 230 of the tool cylinder 23 extends, and tilts forward when the rod 230 retracts.

The plow 22 shown in Figure 2 is a so-called multi-plow, and has a shaft 221 that is positioned in the left-right center and extends in the up-down direction, a left plate 222 that extends to the left from the shaft 221, and a right plate 223 that extends to the right from the shaft 221. The left plate 222 and the right plate 223 each rotate in the front-rear direction relative to the shaft 221 by an optional cylinder 27 (not shown in Figure 2, see Figure 6) attached to the left and right sides of the connecting member 220, respectively.

Specifically, when the rod 270 of the left optional cylinder 27 extends, the left plate 222 rotates forward about the shaft 221 as the central axis, so that the left end is positioned forward of the shaft 221 and tilts so that it faces diagonally forward to the right. In addition, when the rod 270 of the left optional cylinder 27 retracts, the left plate 222 rotates backward about the shaft 221 as the central axis, so that the left end is positioned rearward of the shaft 221 and tilts so that it faces diagonally forward to the left (the state shown in FIG. 2).

Similarly, when the rod 270 of the right-side optional cylinder 27 extends, the right plate 223 rotates forward around the shaft 221 as the central axis, so that the right end is positioned further forward than the shaft 221 and tilts so that it faces diagonally forward to the left. Also, when the rod 270 of the right-side optional cylinder 27 retracts, the right plate 223 rotates rearward around the shaft 221 as the central axis, so that the right end is positioned further rear than the shaft 221 and tilts so that it faces diagonally forward to the right (the state shown in FIG. 2).

In this way, the plow 22 has left plate 222 and right plate 223 that are driven independently, making it possible to adopt a wider variety of working positions than a plow formed from a single plate. Note that the plow 22 does not necessarily have to be a multi-plow, and may be, for example, an angling plow or a side slide angling plow, and there are no particular limitations on the type of plow.

As shown in FIG. 1, the rear frame 1B is provided with a counterweight 12 that maintains balance with the work device 2 so that the vehicle body does not tilt, a cab 13 in which the operator sits, and a machine room 14 that houses various devices required for driving the wheel loader 1. In the rear frame 1B, the counterweight 12 is located at the rear, the cab 13 at the front, and the machine room 14 between the counterweight 12 and the cab 13.

<Configuration of the operator's cab 13>
Next, the configuration of the operator's cab 13 will be described with reference to FIGS.

Figure 3 is a top view of the inside of the driver's cab 13. Figure 4 is an enlarged view of the devices arranged in front of the driver's seat 31. Figure 5 is a perspective view showing an example of the configuration of the first operating lever 351 and the second operating lever 352.

As shown in FIG. 3, inside the cab 3, a driver's seat 31 where the operator sits is provided in the center. In front of the driver's seat 31 are provided a steering operation device 32 for steering the four wheels 11, a front console 33 on which various devices related to the operation of the wheel loader 1 are attached, and a pedal device 34 for operating and stopping the vehicle body. In addition, a work device operation device 35 for operating the work device 2 is provided to the right of the driver's seat 31.

The driver's seat 31 has a seat surface 311, a backrest 312 that serves as a backrest, a pillow-shaped headrest 313 attached to the top of the backrest 312, a left armrest 314L on which the operator rests his/her left arm, and a right armrest 314R on which the operator rests his/her right arm.

The steering operation device 32 has a steering wheel 321 that is rotatably mounted in front of the driver's seat 31 and steers the four wheels according to the amount of rotation (specifically, the rotation angle), and a steering knob 322 that is mounted on the steering wheel 321 and protrudes toward the driver's seat 31 and rotates together with the steering wheel 321.

The steering knob 322 is an auxiliary tool for operating the steering wheel 321. Therefore, the operator may perform steering operations by holding the steering wheel 321, or may perform steering operations by grasping the steering knob 322.

When the operator rotates the steering wheel 321 or steering knob 322 to the right (clockwise), the vehicle body turns to the right, and when the operator rotates the steering wheel 321 or steering knob 322 to the left (counterclockwise), the vehicle body turns to the left.

In the steering operation device 32 provided on the wheel loader 1, the steering knob 322 and the steering wheel 321 are integrally formed. Note that the steering wheel 321 and the steering knob 322 do not necessarily have to be integrally formed, and for example, the steering knob 322 may be detachably fixed to the steering wheel 321 by bolt fastening or the like. Also, the steering operation device 32 does not necessarily have to be a wheel (handle) type, and may be a lever type.

As shown in FIG. 4, the front console 33 includes a main monitor 331 that displays the vehicle's running status, and a setting panel 332 on which various operation switches, such as switches for changing the vehicle's settings, are attached. The setting panels 332 are provided on both the left and right sides of the main monitor 331, and multiple operation switches are arranged vertically at intervals.

The setting panel 332 on the right side is fitted with an upper limit vehicle speed setting switch 332A at the top as an upper limit vehicle speed setting device for setting the upper limit vehicle speed of the vehicle body. This upper limit vehicle speed setting switch 332A is a dial-type switch that can adjust the upper limit vehicle speed steplessly.

The working equipment operation device 35 has a first operation lever 351 for operating the bucket 21 or plow 22 and the lift arm 24, a second operation lever 352 for operating the left plate 222 and the right plate 223 of the plow 22, and a plurality of operation buttons 353 for performing operations related to the drive of the vehicle body. In FIG. 3, the working equipment operation device 35 is mounted on an operation unit 36 placed on the right side of the driver's seat 31 together with a right armrest 314R. Note that the working equipment operation device 35 does not necessarily have to be provided on the right side of the driver's seat 31, and may be provided on the left side of the driver's seat 31 depending on the specifications of the driver's cab 3.

The first operating lever 351 and the second operating lever 352 are both two-axis joystick levers that can perform operation input by tilting them. Specifically, as shown in FIG. 5, when the operator tilts the first operating lever 351 forward and backward, the lift arm 24 operates, and when the operator tilts the first operating lever 351 left and right, the bucket 21 or the plow 22 operates. When the operator tilts the second operating lever 352 forward and backward, the right plate 223 of the plow 22 operates, and when the operator tilts the second operating lever 352 left and right, the left plate 222 of the plow 22 operates.

When operating the plow 22 to perform snow removal work using the wheel loader 1, the operator operates the first control lever 351 in the left-right direction to adjust the forward and backward tilt of the plow 22, while operating the second control lever 352 to adjust the left plate 222 and the right plate 223. Depending on the shape of the road surface, the operator may operate the first control lever 351 in the front-rear direction to raise or lower the lift arm 24 while operating the plow 22. Therefore, the operator may operate the first control lever 351 and the second control lever 352 simultaneously.

When the plow 22 is an angling plow or a side slide angling plow, the blade angles when the operator tilts the second control lever 352 forward or backward, and the blade slides left or right when the operator tilts the second control lever 352 left or right.

As shown in FIG. 5, a mode changeover switch 352A is provided on the top of the second operating lever 352 as a mode changeover device for changing the mode for limiting the vehicle speed of the vehicle body. There are a normal mode in which the upper limit vehicle speed is not limited, and a limit mode in which the upper limit vehicle speed is limited. This mode changeover switch 352A is an on-off switch that changes to the limit mode when the operator operates (presses) it to the on state. Therefore, when the operator operates the mode changeover switch 352A to the on state, the mode changes from the normal mode to the limit mode, and when the operator operates the mode changeover switch 352A to the off state, the mode changes from the limit mode to the normal mode. In other words, when the mode changeover switch 352A is operated, either the normal mode or the limit mode is selected.

In this way, since the mode changeover switch 352A is provided on the top of the second operating lever 352, the operator can operate the mode changeover switch 352A without taking his or her hand off the second operating lever 352. Therefore, the operator can switch the mode to the restricted mode while operating the plow 22.

In FIG. 5, the mode change switch 352A is provided on the top of the second operating lever 352, but this is not limiting and may be provided, for example, on the side of the second operating lever 352. The mode change switch 352A may also be provided on the top or side of the steering knob 322. In this case, the operator can switch the mode to the restricted mode while operating the steering knob 322.

In addition, a proportional switch 351A is provided on the side of the first operating lever 351 (the side facing the rear) that can be slid to adjust settings and the like in a stepless manner. In Figures 3 and 4, the upper limit vehicle speed setting switch 332A is provided in the setting panel 332 on the right side of the front console 33, but for example, this proportional switch 351A may be the upper limit vehicle speed setting switch 332A. In this case, the upper limit vehicle speed setting switch 332A can be slid to adjust the upper limit vehicle speed in a stepless manner, and can be easily operated by the operator compared to a dial type.

When the wheel loader 1 is performing snow removal work or the like, the vehicle speed is limited and the work equipment 2 is operated while traveling at a low speed. Therefore, by providing the mode change switch 352A and the upper vehicle speed setting switch 332A (at least the mode change switch 352A) on the work equipment operation device 35, the operator can simultaneously limit the vehicle speed and operate the work equipment 2 without taking his or her hands off the work equipment operation device 35 (the first operation lever 351 and the second operation lever 352). The drive system of the wheel loader 1 will be described below for each embodiment.

First Embodiment
The drive system 4 of the wheel loader 1 according to the first embodiment of the present invention will be described with reference to FIGS.

(Configuration of Drive System 4)
First, the configuration of the drive system 4 will be described with reference to FIG.

Figure 6 is a system configuration diagram showing an example configuration of the drive system 4 according to the first embodiment.

The drive system 4 of the wheel loader 1 includes an HST traveling drive device 401 with a closed hydraulic circuit, and a hydraulic loading drive device 402 that drives the work equipment 2.

The HST traveling drive device 401 has an engine 40, an HST pump 41 as a traveling hydraulic pump driven by the engine 40, an HST charge pump 41A that supplies pressurized oil to control the HST pump 41, an HST motor 42 as a traveling hydraulic motor connected in a closed circuit to the HST pump 41 via a pair of pipes 400A, 400B, and a controller 5 that controls the engine 40, the HST pump 41, the HST motor 42, etc.

The HST pump 41 is a variable displacement hydraulic pump of the swash plate type or bent axis type, in which the displacement volume is controlled according to the tilt angle. The tilt angle is adjusted by the pump regulator 410 according to a signal output from the controller 5.

The HST motor 42 is a variable displacement hydraulic motor of the swash plate type or the slanted axis type, in which the displacement volume is controlled according to the tilt angle, and transmits the driving force of the engine 40 to the wheels 11 (front wheels 11A and rear wheels 11B). The tilt angle is adjusted by the motor regulator 420 according to a signal output from the controller 5, as in the case of the HST pump 41.

In the HST traveling drive device 401, when the operator first depresses the accelerator pedal (included in the pedal device 34) provided in the cab 13, the engine 40 rotates according to the amount of depression of the accelerator pedal, and the HST pump 41 is driven by the driving force of the engine 40. Then, the HST motor 42 rotates due to the pressurized oil discharged from the HST pump 41, and the output torque from the HST motor 42 is transmitted to the front wheels 11A and rear wheels 11B via the axles 15, causing the wheel loader 1 to travel.

Specifically, when the accelerator pedal is depressed more, the rotation speed of the engine 40 increases, the discharge flow rate of the HST pump 41 increases, and the flow rate of pressurized oil flowing from the HST pump 41 to the HST motor 42 increases. This increases the rotation speed of the HST motor 42 and increases the vehicle speed. On the other hand, when the accelerator pedal is depressed less, the rotation speed of the engine 40 decreases, the discharge flow rate of the HST pump 41 decreases, and the flow rate of pressurized oil flowing from the HST pump 41 to the HST motor 42 decreases. This decreases the rotation speed of the HST motor 42 and slows the vehicle speed.

In this way, the HST traveling drive device 401 adjusts (changes) the vehicle speed by continuously increasing or decreasing the discharge flow rate of the HST pump 41, enabling the wheel loader 1 to start smoothly and stop with less impact. Note that it is not necessarily necessary to control the vehicle speed by adjusting the discharge flow rate on the HST pump 41 side, and the vehicle speed may be controlled by adjusting the displacement on the HST motor 42 side. Therefore, by controlling the displacement volume of the HST pump 41 or the displacement volume of the HST motor 42 with the controller 5, the vehicle speed can be adjusted regardless of the amount of depression of the accelerator pedal (regardless of the engine 40 speed).

In this embodiment, a speed stage switch 332B is provided for selecting the upper limit vehicle speed from speed stages 1 to 4. This speed stage switch 332B is mainly used for forward travel of the wheel loader 1. Of the speed stages 1 to 4, speed stages 1 and 2 correspond to "low speed stages", and speed stages 3 and 4 correspond to "medium to high speed stages". For example, the "low speed stage" is selected for work in which the work implement 2 is operated while traveling slowly, such as loading work or snow removal work. On the other hand, the "medium to high speed stage" is selected when the wheel loader 1 travels on a road in an unloaded state. The upper limit vehicle speed setting switch 332A described above sets the upper limit vehicle speed value for each of the speed stages 1 to 4.

The loading drive device 402 has a loading hydraulic pump 43 that is driven by the engine 40 to supply hydraulic oil to each of the implement cylinder 23, the lift arm cylinder 25, and the option cylinder 27, a hydraulic oil tank 44 that stores hydraulic oil, a control valve 45 that is provided between each cylinder 23, 25, 27 and the loading hydraulic pump 43 to control the flow (direction and flow rate) of hydraulic oil supplied from the loading hydraulic pump 43 to each cylinder 23, 25, 27, and an electromagnetic proportional valve 46 that controls the control valve 45 according to a command signal output from the controller 5.

Note that in FIG. 6, only one of the two lift arm cylinders 25 and option cylinders 27 is shown. In reality, a control valve 45 is provided for each of the cylinders 23, 25, and 27, and a pair of solenoid proportional valves 46 is provided for each control valve 45, but these are not shown in FIG. 6.

The loading hydraulic pump 43 is a fixed-displacement hydraulic pump that discharges hydraulic oil at a discharge flow rate according to the RPM of the engine 40. The hydraulic oil discharged from the loading hydraulic pump 43 flows into each of the cylinders 23, 25, and 27 via the control valve 45. This causes the rods 230, 250, and 270 of each of the cylinders 23, 25, and 27 to extend and retract. Note that the loading hydraulic pump 43 does not necessarily have to be a fixed-displacement hydraulic pump, and may be a variable-displacement hydraulic pump.

(Configuration of Controller 5)
Next, the configuration of the controller 5 will be described with reference to FIG.

Figure 7 is a functional block diagram showing the functions of the controller 5.

The controller 5 is configured with a CPU, RAM, ROM, HDD, input I/F, and output I/F connected to each other via a bus. Various operating devices such as a mode change switch 352A, an upper limit vehicle speed setting switch 332A, a first operating lever 351, and a second operating lever 352 are connected to the input I/F, and a pump regulator 410 and a motor regulator 420 are each connected to the output I/F.

In this hardware configuration, the CPU reads out a control program (software) stored in a recording medium such as a ROM, HDD, or optical disk, expands it on RAM, and executes the expanded control program, whereby the control program and hardware work together to realize the functions of the controller 5.

In this embodiment, the controller 5 is described as a computer configured by a combination of software and hardware, but this is not limiting. For example, an integrated circuit that realizes the functions of a control program executed on the wheel loader 1 may be used as an example of another computer configuration.

The controller 5 includes a data acquisition unit 51, a mode determination unit 52, an operation determination unit 53, and a signal output unit 54.

The data acquisition unit 51 acquires data relating to the mode switching signal output from the mode switching switch 352A, the operation signals output from each of the first operating lever 351 and the second operating lever 352, and the setting value output from the upper limit vehicle speed setting switch 332A.

The mode determination unit 52 determines whether the mode changeover switch 352A has switched to the restricted mode, i.e., whether it has turned on, based on the mode changeover signal acquired by the data acquisition unit 51.

The operation determination unit 53 determines whether the first operating lever 351 or the second operating lever 352 has been operated, i.e., whether the working device 2 is operating, based on the operation signal acquired by the data acquisition unit 51.

When the mode determination unit 52 determines that the mode changeover switch 352A has been switched to the limit mode and the operation determination unit 53 determines that the first operating lever 351 or the second operating lever 352 has been operated, the signal output unit 54 outputs a limit signal to the pump regulator 410 and the motor regulator 420 so that the upper limit vehicle speed becomes the value acquired by the data acquisition unit 51.

In this way, the controller 5 limits the upper limit vehicle speed only when the two conditions of the mode changeover switch 352A being switched to the limit mode and the first operating lever 351 or the second operating lever 352 being operated are met. Note that even when the upper limit vehicle speed is being limited, the controller 5 controls the engine 40 speed so that the engine target speed remains at the value corresponding to the amount of depression of the accelerator pedal.

For example, when the wheel loader 1 is clearing snow on a road, at an intersection it is necessary to prevent snow from accumulating on the road that intersects the road in the travelling direction. Before approaching the intersection, the wheel loader 1 moves forward with the plow 22 tilted to the left when viewed from above (a position in which the left end of the plow 22 is behind the right end of the plow 22) in order to clear the snow to be cleared to the left side of the vehicle body. Then, when the wheel loader 1 approaches the intersection, the operator operates the plow 22 so that it changes from the above-mentioned state of being tilted to the left when viewed from above to a state where the left and right are parallel when viewed from above.

At this time, the wheel loader 1 needs to operate the plow 22 while limiting the vehicle speed when entering the intersection. If the upper limit vehicle speed were limited simply by turning on the mode changeover switch 352A, the upper limit vehicle speed would be limited even in situations where it is not necessary, leading to reduced efficiency in snow removal work. Furthermore, if the upper limit vehicle speed is not limited at the intersection, by the time the plow 22 becomes parallel to the left and right when viewed from above, the wheel loader 1 will have already passed the intersection.

However, in this embodiment, the controller 5 determines that the second operating lever 352 has been operated to change the plow 22 from a state inclined left as viewed from above to a state parallel to the left as viewed from above, so that the vehicle speed can be quickly limited at the timing intended by the operator suitable for snow removal work. That is, with this wheel loader 1, when working using the working device 2 while traveling, the operator can operate to limit the vehicle speed and increase the driving force of the working device 2 only when necessary, without taking his/her hands off the second operating lever 352 (or the steering knob 322). On the other hand, when working using the working device 2 while traveling, the vehicle speed is not limited in situations where vehicle speed limiting is not necessary. Therefore, the vehicle speed can be limited according to the operator's intended timing and work situation regardless of the amount of depression of the accelerator pedal (without reducing the driving force of the working device 2), leading to improved work efficiency.

In this embodiment, the controller 5 limits the upper vehicle speed by controlling both the pump regulator 410 and the motor regulator 420, but depending on the magnitude of the upper vehicle speed limit, it may control either the pump regulator 410 or the motor regulator 420.

(Processing in Controller 5)
Next, the process executed in the controller 5 will be described with reference to FIG.

Figure 8 is a flowchart showing the flow of processing executed by the controller 5.

First, the data acquisition unit 51 of the controller 5 acquires the setting value set by the upper limit vehicle speed setting switch 332A (step S501). Next, the data acquisition unit 51 acquires the mode switching signal output from the mode switching switch 352A (step S502).

Next, the mode determination unit 52 determines whether the mode changeover switch 352A has switched to the restricted mode based on the mode changeover signal acquired in step S502 (step S503).

If it is determined in step S503 that the mode changeover switch 352A has been switched to the limit mode (step S503/YES), the data acquisition unit 51 acquires the operation signal output from the first operation lever 351 or the second operation lever 352 (step S504). On the other hand, if it is determined in step S503 that the mode changeover switch 352A has not been switched to the limit mode, i.e., that the mode changeover switch 352A is in the OFF state (step S503/NO), the process returns to step S502 and is repeated.

Next, the operation determination unit 53 determines whether the first operating lever 351 or the second operating lever 352 has been operated based on the operation signal acquired in step S504 (step S505).

If it is determined in step S505 that the first operating lever 351 or the second operating lever 352 has been operated (step S505/YES), the signal output unit 54 outputs a limiting signal to the pump regulator 410 and the motor regulator 420 so that the upper limit vehicle speed becomes the value acquired in step S501 (step S506), and the processing in the controller 5 ends.

On the other hand, if it is determined in step S505 that neither the first operating lever 351 nor the second operating lever 352 has been operated, i.e., that the working device 2 is not operating (step S505/NO), the process returns to step S502 and is repeated.

In both cases where the answer is NO in step S503 and where the answer is NO in step S505, the upper limit vehicle speed is not limited, and the upper limit vehicle speed is set to the speed step selected by the speed step switch 332B. Furthermore, the upper limit vehicle speed limit control in the controller 5 is mainly performed when a low speed step (speed step 1 or speed step 2) is selected by the speed step switch 332B.

In FIG. 8, after determining in step S503 whether the mode changeover switch 352A has switched to the limit mode, it is determined in step S505 whether the first operating lever 351 or the second operating lever 352 has been operated. However, this is not limited thereto. For example, it may be determined whether the first operating lever 351 or the second operating lever 352 has been operated, and then it may be determined whether the mode changeover switch 352A has switched to the limit mode, or both may be determined simultaneously in parallel.

Second Embodiment
Next, a drive system 4A of a wheel loader 1 according to a second embodiment of the present invention will be described with reference to Fig. 9. In Fig. 9, components common to those described for the drive system 4 of the wheel loader 1 according to the first embodiment are given the same reference numerals and descriptions thereof will be omitted. The same applies to the third embodiment below.

Figure 9 is a system configuration diagram showing an example configuration of the drive system 4A according to the second embodiment.

The drive system 4A according to this embodiment is configured to include an HMT traveling drive device 401A and a cargo handling drive device 402. The HMT traveling drive device 401A includes an HST traveling drive device 401 in which an HST pump 41 and an HST motor 42 are connected in a closed circuit via a pair of pipes 400A, 400B, and a mechanical transmission unit 80, and the driving force of the engine 40 is transmitted in parallel to the HST traveling drive device 401 and the mechanical transmission unit 80 via a planetary gear mechanism 81.

The planetary gear mechanism 81 has a sun gear 811 fixed to the input shaft 82, a number of planetary gears 812 meshed with the outer periphery of the sun gear 811, a planetary carrier 813 that supports each of the planetary gears 812, a ring gear 814 meshed with the outer periphery of the planetary gears 812, and a pump input gear 815 meshed with the outer periphery of the ring gear 814.

The output torque of the engine 40 is transmitted to the input shaft 82 via a clutch device 83 having a forward hydraulic clutch 83A, a reverse hydraulic clutch 83B, and a clutch shaft 83C, and is then transmitted from the input shaft 82 to the planetary gear mechanism 81.

The planetary carrier 813 of the planetary gear mechanism 81 is fixed to the output shaft 84, which transmits the driving force of the engine 40 to the mechanical transmission unit 80. The driving force of the engine 40 transmitted to the mechanical transmission unit 80 is transmitted to the axle 15 via a propeller shaft 85 connected to the output shaft 84, which drives the multiple wheels 11 (front wheels 11A and rear wheels 11B).

The pump input gear 815 of the planetary gear mechanism 81 is fixed to the rotating shaft of the HST pump 41, and the driving force of the engine 40 is also transmitted to the HST traveling drive device 401. A motor output gear 86 is fixed to the rotating shaft of the HST motor 42, and the motor output gear 86 meshes with a gear 840 of the output shaft 84. Therefore, the driving force of the engine 40 transmitted to the HST traveling drive device 401 is also transmitted to the axle 15 via a propeller shaft 85 connected to the output shaft 84, thereby driving the multiple wheels 11 (front wheels 11A and rear wheels 11B).

In this way, by combining the HST traveling drive device 401 and the mechanical transmission unit 80 to form a transmission, it is possible to improve the transmission efficiency compared to the HST type traveling drive system described in the first embodiment. Note that while FIG. 9 shows an input split type HMT type traveling drive system in which the output from the planetary gear mechanism 81 is input to the HST traveling drive device 401, the present invention is not limited to this, and may also be an output split type HMT type traveling drive system in which the output from the HST traveling drive device 401 is input to the planetary gear mechanism 81.

In this embodiment, the same effects and advantages as those described in the first embodiment can be obtained.

Third Embodiment
Next, a drive system 4B of a wheel loader 1 according to a third embodiment of the present invention will be described with reference to FIG.

Figure 10 is a system configuration diagram showing an example configuration of the drive system 4B according to the third embodiment.

The drive system 4B according to this embodiment includes an EMT travel drive device 401B and a load handling drive device 402. In the EMT travel drive device 401B, a generator 91 is provided instead of the HST pump 41, and an electric motor 92 is provided instead of the HST motor 42 in the above-mentioned HMT travel drive device 401A.

In this embodiment, when the mode changeover switch 352A is switched to the limit mode and the first operating lever 351 or the second operating lever 352 is operated, the controller 5 reduces the rotation speed of the electric motor 92 to limit the upper limit vehicle speed. The rotation speed of the electric motor 92 is adjusted by changing the current value or voltage value to the electric motor 92.

Specifically, in a step corresponding to step S506 shown in FIG. 8, the signal output unit 54 outputs a limit signal (current value or voltage value related to the limit) to the electric motor 92 so that the upper limit vehicle speed becomes the value acquired in step S501. As a result, in this embodiment as well, it is possible to obtain the same actions and effects as those described in the first embodiment.

The above describes an embodiment of the present invention. Note that the present invention is not limited to the above embodiment, and various modified examples are included. For example, the above embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to having all of the configurations described. It is also possible to replace part of the configuration of this embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of this embodiment. Furthermore, it is also possible to add, delete, or replace part of the configuration of this embodiment with other configurations.

For example, in the above embodiment, a wheel loader 1 is described that can perform loading and unloading work by replacing the bucket 21 with a plow 22, which is a work tool other than the bucket 21, but the present invention is not limited to this. Any work vehicle may be used as long as it is capable of performing loading and unloading work and various other tasks by being able to replace the loading tool with an attachment other than the loading tool.

In the above embodiment, the mode changeover switch 352A is switched to the restricted mode by manual operation by the operator, but this is not limiting. For example, a mechanism may be constructed in which position data of the wheel loader 1 is acquired using a GPS sensor attached to the vehicle body, and the mode changeover switch 352A is switched to the restricted mode when the controller 5 determines that the wheel loader 1 is entering an intersection. In this case, the mode changeover switch 352A does not need to be provided in the work equipment operation device 35 or the steering operation device 32.

1: Wheel loader (work vehicle)
1A: Front frame 1B: Rear frame 2: Work device 5: Controller 11: Wheels 13: Cab 21: Bucket (loading and unloading tool)
22: Plow (attachment)
24: Lift arm (arm member)
31: Driver's seat 32: Steering operation device 35: Working device operation device 40: Engine 41: HST pump (hydraulic pump for traveling)
42: HST motor (hydraulic motor for traveling)
91: Generator 92: Electric motor 321: Steering wheel 322: Steering knob 332A: Upper limit vehicle speed setting switch (upper limit vehicle speed setting device)
351: First operating lever 352: Second operating lever 352A: Mode change switch (mode change device)

Claims (7)

A vehicle body having a plurality of wheels;
A working device attached to a frame constituting the vehicle body;
A cab mounted on the frame; and
a working device operation device provided on one of the left and right sides of a driver's seat in the driver's cab for operating the working device;
An engine mounted on the vehicle body;
A variable displacement hydraulic pump for traveling driven by the engine;
a variable displacement hydraulic motor for traveling that is connected in a closed circuit to the hydraulic pump for traveling and transmits the driving force of the engine to the plurality of wheels;
A controller that controls the traveling hydraulic pump and the traveling hydraulic motor,
In a work vehicle equipped with
a mode switching device for switching a mode for restricting an upper limit value of the traveling speed of the vehicle body;
an upper limit vehicle speed setting device for setting the upper limit value of the traveling speed of the vehicle body;
having
The controller:
a displacement volume of the traveling hydraulic pump or a displacement volume of the traveling hydraulic motor is controlled so that, when the mode is switched to a limit mode by the mode switching device which limits the upper limit value of the traveling speed of the vehicle body and the work implement operation device is operated , the upper limit value of the traveling speed of the vehicle body becomes a setting value set by the upper limit vehicle speed setting device. The work vehicle according to claim 1,
A work vehicle, wherein the mode switching device is provided in the work implement operation device. The work vehicle according to claim 2,
The working device is
An arm member to which an attachment can be attached at a tip end thereof,
The working device operation device includes:
A first operating lever for operating the arm member;
a second operating lever for operating the attachment when the attachment is attached to the tip portion of the arm member ;
having
each of the first operation lever and the second operation lever is a joystick lever capable of performing an operation input by tilting,
The mode switching device includes:
A work vehicle comprising an on/off switch provided on an upper portion or a side portion of the second operating lever, the on/off switch being switched to the limit mode when operated to an on state. The work vehicle according to claim 3,
The upper limit vehicle speed setting device is
A work vehicle comprising a switch that is provided on an upper portion or a side portion of the first operating lever and that can adjust the set value steplessly by sliding the switch. The work vehicle according to claim 1,
a steering operation device provided in the driver's cab for steering the plurality of wheels;
A work vehicle, wherein the mode switching device is provided in the steering operation device. The work vehicle according to claim 5,
The steering operation device is
a steering wheel rotatably provided in front of the driver's seat for steering the plurality of wheels in accordance with an amount of rotation of the steering wheel;
a steering knob provided on the steering wheel so as to protrude toward the driver's seat and rotate together with the steering wheel;
having
The mode switching device includes:
A work vehicle characterized in that the on/off switch is provided on an upper portion or a side portion of the steering knob and switches to the limit mode when operated to an on state. A vehicle body having a plurality of wheels;
A working device attached to a frame constituting the vehicle body;
A cab mounted on the frame; and
a working device operation device provided on one of the left and right sides of a driver's seat in the driver's cab for operating the working device;
An engine mounted on the vehicle body;
a generator driven by the engine;
an electric motor connected to the generator and configured to transmit driving force of the engine to the plurality of wheels;
a controller for controlling the engine and the electric motor;
In a work vehicle equipped with
a mode switching device for switching a mode for restricting an upper limit value of the traveling speed of the vehicle body;
an upper limit vehicle speed setting device for setting the upper limit value of the traveling speed of the vehicle body;
having
The controller:
a rotation speed of the electric motor is controlled so that, when the mode is switched by the mode switching device to a limit mode which limits the upper limit value of the vehicle body's traveling speed and the work implement operation device is operated , the upper limit value of the vehicle body's traveling speed becomes a setting value set by the upper limit vehicle speed setting device.

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