JP2022056577A - Work vehicle - Google Patents

Abstract

To realize a work vehicle provided with a lever pattern change technology and an automatic shift technology upon turning in a simple mechanism and in low cost.SOLUTION: A controller 140 of a work vehicle 1 determines whether a first traveling device 11 travels forward or backward based on pressure values detected with a third pressure sensor 83 and a fourth pressure sensor 84 arranged in a pilot oil line in communication with a first travel hydraulic pump 26L, and determines whether a second traveling device 12 travels forward or backward based on presence or absence of application of specific pressure detected with a first pressure switch 91 and a second pressure switch 92 arranged in the pilot oil line in communication with a second travel hydraulic pump 26R, so as to change a transmission mechanism from a high speed mode to a low speed mode without interlocking a first control lever 171 and a second control lever 172 in either case of a state where the first traveling device 11 travels forward and the second traveling device 12 travels backward, and a state where the first traveling device 11 travels backward and the second traveling device 12 travels forward.SELECTED DRAWING: Figure 3

Description

The present invention relates to a work vehicle in which an attachment is attached to an arm to perform a predetermined work.

Conventionally, an HST (Hydro-Static Transmission: hydrostatic continuously variable transmission), which is a drive mechanism including a traveling hydraulic pump and a traveling hydraulic motor, has been known. A crawler loader (truck loader) is known as an example of a work vehicle that drives a traveling device by this HST (see Patent Document 1: Japanese Patent Application Laid-Open No. 2012-215274).

Generally, in a crawler loader, for example, an arm that can swing up and down is attached to a vehicle body that is configured to be able to run, and an attachment such as a bucket is attached to the tip of this arm so that it can swing up and down. Has been done. In addition, a pair of left and right operating levers are provided in the cockpit provided on the vehicle body, and by tilting the operating levers back and forth and left and right, the hydraulic actuator is operated according to the tilting direction and the amount of tilting. The vehicle body can be moved back and forth, and the arm and attachment can be swung up and down.

Here, the combination of the tilting operation for the operation lever in the crawler loader and the hydraulic actuator operated in response to this tilting operation (hereinafter, may be referred to as "operation pattern") may differ depending on the manufacturer, for example. Yes, it is not completely unified. Therefore, in the work vehicle exemplified in Patent Document 1, a technique (hereinafter, may be referred to as "lever pattern change technique") that allows an operator to select two operation patterns has been realized.

Japanese Unexamined Patent Publication No. 2012-215274 Japanese Unexamined Patent Publication No. 2004-340259

By the way, in a work vehicle such as a crawler loader, which travels with a crawler in particular, the following problems may occur when the operation lever is operated to make a turn. Specifically, when a so-called spin turn operation is performed in which the traveling devices provided on the left and right sides of the vehicle body are rotated in opposite directions to change the direction while traveling in a high-speed mode with a small torque, the oil supplied from the traveling hydraulic pump is performed. There is a problem that the rotation speed of both the left and right traveling hydraulic motors is remarkably lowered due to the insufficient torque caused by the decrease in the amount, the movement of the spin turn becomes slow, and the operability is deteriorated.

In order to solve this problem, as exemplified in Patent Document 2, when a turn operation such as a spin turn is performed while traveling in a high-speed mode with a small torque, a low-speed mode with a large torque is automatically performed. (Hereinafter, it may be referred to as "automatic shift technology at turn") has been realized.

Against this background, if a work vehicle equipped with both "lever pattern change technology" and "automatic shift technology at turn" can be realized, workability can be significantly improved. However, for that purpose, it is assumed that the mechanism and the hydraulic circuit will be complicated and the equipment cost will rise, and it has not been realized yet.

The present invention has been made in view of the above circumstances, and realizes a work vehicle equipped with both "lever pattern change technology" and "automatic transmission technology at turn" at low cost with a simple mechanism and hydraulic circuit. The purpose.

The present invention solves the above-mentioned problems by means of solutions as described below.

The work vehicle according to the present invention is a work vehicle in which an attachment is attached to an arm to perform a predetermined work, and is a drive source, a first traveling hydraulic pump and a second traveling hydraulic pump driven by the drive source. , And a pair of a first traveling hydraulic motor and a second traveling hydraulic motor driven by the pressure oil supplied from the first traveling hydraulic pump and the second traveling hydraulic pump, respectively, are provided on the left and right sides of the vehicle body. The first traveling device and the second traveling device driven by the first traveling hydraulic motor and the second traveling hydraulic motor, respectively, and the pilot hydraulic pump to the first traveling hydraulic pump, the second traveling hydraulic pump, and the arm. Controls the operation of the pilot oil passage that communicates with the operation control valve to supply pilot oil, the control room on which the operator boarded and controls, the arm, the first traveling device, and the second traveling device. A first operating lever and a second operating lever are provided in the control room, and the first operating lever moves forward and backward of the first traveling device and the second traveling device. The first operation pattern for lowering and raising the arm by the second operating lever, and the second operating lever for moving forward and backward of the first traveling device and lowering and raising the arm by the first operating lever. A lever pattern switching mechanism having a selector valve for switching the pilot hydraulic pump so as to correspond to a second operation pattern for moving forward and backward of the second traveling device, and a traveling mode of high speed mode and low speed mode. Further equipped with a speed change mechanism for switching, as the pilot oil pump, the first pilot hydraulic pump communicating with the arm lowering input port of the arm operation control valve and the arm raising input port of the arm operation control valve are provided. A second pilot oil passage communicating with the second pilot oil passage, a third pilot oil passage communicating with the forward input port of the first traveling hydraulic pump, and a fourth pilot oil passage communicating with the reverse input port of the first traveling hydraulic pump. The first pilot oil passage has a fifth pilot oil passage communicating with the forward input port of the second traveling hydraulic pump and a sixth pilot oil passage communicating with the reverse input port of the second traveling hydraulic pump. The pilot oil passage is provided with a first pressure sensor that detects the pressure value of the pilot oil to be supplied, and the second pilot oil passage is a second that detects the pressure value of the pilot oil to be supplied. 2 Pressure pump An sensor is provided, and the third pilot oil passage is provided with a third pressure sensor that detects the pressure value of the pilot oil to be supplied, and the fourth pilot oil passage is supplied. A fourth pressure sensor for detecting the pressure value of the pilot oil is provided, and a first pressure switch for detecting whether or not a predetermined pressure is applied by the supplied pilot oil is provided in the fifth pilot oil passage. A second pressure switch for detecting whether or not a predetermined pressure is applied by the supplied pilot oil is provided in the sixth pilot oil passage, and the control device includes the third pressure sensor and the third pressure sensor. 4 It is determined whether the first traveling device is in the forward state or the reverse state based on the pressure value detected by the pressure sensor, and is based on the presence or absence of application of the predetermined pressure detected by the first pressure switch and the second pressure switch. It is determined whether the second traveling device is in the forward state or the reverse state, and when the first traveling device is in the forward state and the second traveling device is in the reverse state, and when the first traveling device is in the reverse state and the second traveling device is in the reverse state. When the traveling device is in the forward state, it is required to control the speed change mechanism from the high speed mode to the low speed mode without interlocking with the first operation lever and the second operation lever. And.

According to the present invention, a work vehicle equipped with both "lever pattern change technology" and "automatic transmission at turn technology" can be realized at low cost with a simple mechanism and hydraulic circuit.

It is a perspective view which shows the example of the work vehicle which concerns on embodiment of this invention. It is a perspective view which shows the structural example of the cockpit part of the work vehicle shown in FIG. It is a schematic diagram of the hydraulic circuit system of the work vehicle which concerns on 1st Embodiment of this invention (the 1st operation pattern correspondence figure). It is a schematic diagram of the hydraulic circuit system of the work vehicle which concerns on 1st Embodiment of this invention (second operation pattern correspondence figure). It is a schematic diagram which shows the structural example of the selector valve of the work vehicle which concerns on embodiment of this invention. It is a flowchart which shows the control example (automatic shift technique at the time of turn) by the control device of the work vehicle which concerns on 1st Embodiment of this invention. It is a flowchart which shows the control example (float technique) by the control device of the work vehicle which concerns on 1st Embodiment of this invention. It is a schematic diagram of the hydraulic circuit system of the work vehicle which concerns on 2nd Embodiment of this invention (second operation pattern correspondence figure). It is a flowchart which shows the control example (automatic transmission technique at the time of a high load) by the control device of the work vehicle which concerns on 2nd Embodiment of this invention.

(First Embodiment)
Hereinafter, the first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view (a perspective view from above the rear portion) showing an example of the work vehicle 1 according to the present embodiment. Further, FIG. 2 is a perspective view showing an example of the internal configuration of the cockpit 16 of the work vehicle 1 according to the present embodiment. Further, FIG. 3 is a schematic diagram (circuit diagram) of the hydraulic circuit system (state set in the first operation pattern described later) of the work vehicle 1 according to the first embodiment. Further, FIG. 4 is a schematic diagram (circuit diagram) of the hydraulic circuit system (state set in the second operation pattern described later) of the work vehicle 1 according to the first embodiment. Further, FIG. 5 is a schematic view showing a configuration example of the selector valve 50 of the work vehicle 1 according to the present embodiment. In all the drawings for explaining the embodiment, the members having the same function may be designated by the same reference numerals, and the repeated description thereof may be omitted.

First, the overall configuration of the work vehicle 1 will be described. Here, a crawler loader (truck loader) that travels with a crawler will be described as an example, but the description is not limited to this.

As shown in FIG. 1, the work vehicle 1 has traveling devices 11 and 12 at the lower left and right sides, a work device 14 at the front, a cockpit 16 at the center, an engine 20 at the rear, and the like with respect to the vehicle body 10. It is configured to include an engine room 18 in which the vehicle is housed and an arm post 152 to which the arm 154 is mounted. As an example, the traveling device (the first traveling device 11 and the second traveling device 12) is configured by pairing left and right with a crawler (trackless crawler) 22 and the like. However, the present invention is not limited to this, and may be configured to run with a pair of left and right tires (referred to as "skid steer loader") (not shown).

First, the working device 14 includes a pair of left and right arms 154 swingably pivoted to the arm post 152, and a bracket 162 swingably pivoted to the tip of the arm 154. It is configured to include an attachment 164 detachably attached to the bracket 162. Here, a pair of left and right arm cylinders 156 are provided straddling the arm post 152 and the arm 154, and a pair of left and right attachment cylinders (commonly known as "bucket cylinders") are provided straddling the bracket 162 and the arm 154. (Not shown).

According to this configuration, the arm 154 can be swung up and down with respect to the vehicle body 10 by expanding and contracting the arm cylinder 156. Further, by expanding and contracting the attachment cylinder, the bracket 162, that is, the attached attachment 164 can be oscillated up and down with respect to the arm 154.

In the present embodiment, a configuration including a bucket as the attachment 164 is given as an example. However, the attachment 164 is not limited to this configuration, and the attachment 164 is appropriately selected and mounted according to the work application. As another example, a hydraulically driven attachment such as a concrete cutter or a trencher can be attached (not shown). The attachment 164 is configured to be replaced by itself or as a set with the bracket 162. Alternatively, there is also a configuration in which the bracket and the attachment are integrated (not shown). The work vehicle 1 is provided with a service oil passage for supplying pressure oil (hydraulic oil of a predetermined pressure) to the attachment driven by hydraulic pressure (not shown).

Next, the engine room 18 is provided in the rear part of the vehicle body 10 (rear position of the cockpit 16), and the engine 20 as a drive source, the equipment described later, and the like are mounted therein in a form accommodated therein. .. As an example, the engine 20 uses, but is not limited to, a water-cooled diesel engine. The traveling devices 11 and 12 and the working device 14 described above are configured to be driven by receiving pressure oil sent from each hydraulic pump driven by the engine 20. The drive source may be configured to use a battery instead of the engine 20 or together with the engine 20 (not shown).

The work vehicle 1 according to the present embodiment is configured to travel with an HST (Hydro-Static Transmission). More specifically, as an example of the configuration for driving the traveling devices 11 and 12, the variable displacement traveling hydraulic pump 26 (first traveling hydraulic pump 26L, second traveling hydraulic pump 26R) driven by the engine 20 as a drive source. , And a traveling hydraulic motor 27 (first traveling hydraulic motor 27L, second traveling hydraulic motor 27R) driven by pressure oil supplied from the traveling hydraulic pump 26 (first traveling hydraulic pump 26L, second traveling hydraulic pump 26R). It is equipped with. Further, a pilot hydraulic pump 21 driven by the engine 20 to generate pilot hydraulic pressure, a traveling hydraulic pump 26 (first traveling hydraulic pump 26L, second traveling hydraulic pump 26R) from the pilot hydraulic pump 21, and a control valve for arm operation. It is provided with a pilot oil passage (details will be described later) that communicates with 28 and the like and applies pilot hydraulic pressure. Further, an engine control that controls the engine 20 based on a command from the control device 140 that controls the operation of the drive mechanism, the traveling devices 11, 12, the arm 154, the attachment 164, and the like of the work vehicle 1, and the control device 140. A unit (ECU) 142 is provided.

Here, the work vehicle 1 according to the present embodiment is provided with a speed change mechanism that switches between at least a "high speed mode" and a "low speed mode". Specifically, the speed change mechanism is configured to include a speed change control valve 24, and is a mechanism for switching the traveling mode based on a command from the control device 140. For example, the "high-speed mode" is a traveling mode in which the rotation speed of the traveling hydraulic pump 26 is high and the driving torque is small. On the other hand, the "low speed mode" is a traveling mode in which the rotation speed of the traveling hydraulic pump 26 is low and the driving torque is large. As a modification, a configuration having other traveling modes may be used in combination.

Next, as shown in FIG. 2, the cockpit 16 is the first operation for operating the seat 170 on which the operator (operator) sits and the traveling devices 11, 12, the arm 154, the attachment 164, and the like. It includes a lever 171 (as an example, a lever on the left side) and a second operating lever 172 (as an example, a lever on the right side). Further, a float switch for float operation of the arm 154 (details of the operation will be described later), various operation switches for operating the operation of each mechanism, and the like are provided, and these are arranged on the operation panel 174 and the like. A cluster 176 that displays vehicle information may be provided, and the cluster 176 may be configured to display an operation switch for operation.

Here, the first remote control valve unit 39 provided in conjunction with the first operation lever 171 has four pilot valves (first pilot valve 31, second pilot valve 32, third pilot valve 33, fourth pilot valve 34). ), And based on the pressure oil supplied from the pilot hydraulic pump 21 driven by the engine 20, a pilot pressure according to the tilting operation direction and the tilting amount with respect to the first operating lever 171 is generated. It is configured in. On the other hand, the second remote control valve unit 49 provided in conjunction with the second operation lever 172 has four pilot valves (fifth pilot valve 42, sixth pilot valve 44, seventh pilot valve 43, eighth pilot valve 41). Is configured to generate a pilot pressure according to the tilting operation direction and the tilting amount with respect to the second operating lever 172 based on the pressure oil supplied from the pilot hydraulic pump 21.

The work vehicle 1 according to the present embodiment is provided with a lever pattern switching mechanism for switching the configuration of the pilot oil passage by switching the selector valve 50. According to this, a technique (lever pattern change technique) that allows an operator to select two operation patterns is realized. As a general rule, as shown in the operation pattern diagram of FIG. 3A, the first operation lever 171 advances and reverses the first traveling device 11 and the second traveling device 12, and the second operating lever 172 causes the arm 154 to move forward and backward. The first operation pattern of descending and ascending is realized. The hydraulic circuit configuration (main part centered on the pilot oil passage) at that time is shown in FIG. 3 (b). Further, as shown in the operation pattern diagram of FIG. 4A, the first operation lever 171 advances and reverses the first traveling device 11 and the arm 154 lowers and ascends, and the second operating lever 172 second travels. A second operation pattern for moving the device 12 forward and backward is realized. The hydraulic circuit configuration (main part centered on the pilot oil passage) at that time is shown in FIG. 4 (b).

As described above, by realizing the lever pattern change technology, it becomes possible for the operator to select an operation pattern that is easy to maneuver, and it is possible to improve workability. Hereinafter, the case where the first operation pattern is set and the case where the second operation pattern is set will be described in detail.

First, the case where the first operation pattern is set will be described with reference to FIGS. 3 and 5. When the first operating lever 171 is tilted forward, pilot pressure is generated in the second pilot valve 32 and the third pilot valve 33, and pilot oil is supplied to the following pilot oil passages. That is, the pilot pressure generated by the second pilot valve 32 passes through the second input oil passage 32a and the fifth output oil passage (fifth pilot oil passage) 62a, and the forward input port 26c of the second traveling hydraulic pump 26R. Is supplied to. Further, the pilot pressure generated by the third pilot valve 33 passes through the third input oil passage 33a and the third output oil passage (third pilot oil passage) 63a, and the forward input port 26a of the first traveling hydraulic pump 26L. Is output to. As a result, the second traveling hydraulic motor 27R is rotationally driven to the forward side, and the second traveling device 12 is driven forward. Further, the first traveling hydraulic motor 27L is rotationally driven to the forward side, and the first traveling device 11 is driven forward. At this time, the work vehicle 1 travels forward.

When the first operating lever 171 is tilted backward, pilot pressure is generated in the first pilot valve 31 and the fourth pilot valve 34, and pilot oil is supplied to the following pilot oil passages. That is, the pilot pressure generated by the first pilot valve 31 passes through the first input oil passage 31a and the fourth output oil passage (fourth pilot oil passage) 61a, and the reverse input port 26b of the first traveling hydraulic pump 26L. Is supplied to. Further, the pilot pressure generated by the 4th pilot valve 34 passes through the 4th input oil passage 34a and the 6th output oil passage (6th pilot oil passage) 64a to the reverse input port 26d of the 2nd traveling hydraulic pump 26R. Is supplied to. As a result, the second traveling hydraulic motor 27R is rotationally driven to the reverse side, and the second traveling device 12 is driven backward. Further, the first traveling hydraulic motor 27L is rotationally driven to the reverse side, and the first traveling device 11 is driven backward. At this time, the work vehicle 1 travels backward.

When the first operating lever 171 is tilted to the right, pilot pressure is generated in the third pilot valve 33 and the fourth pilot valve 34, and pilot oil is supplied to the following pilot oil passages. That is, the pilot pressure generated by the third pilot valve 33 passes through the third input oil passage 33a and the third output oil passage (third pilot oil passage) 63a, and the forward input port 26a of the first traveling hydraulic pump 26L. Is supplied to. Further, the pilot pressure generated by the 4th pilot valve 34 passes through the 4th input oil passage 34a and the 6th output oil passage (6th pilot oil passage) 64a to the reverse input port 26d of the 2nd traveling hydraulic pump 26R. Is supplied to. As a result, the second traveling hydraulic motor 27R is rotationally driven to the reverse side, and the second traveling device 12 is driven backward. Further, the first traveling hydraulic motor 27L is rotationally driven to the forward side, and the first traveling device 11 is driven forward. At this time, the work vehicle 1 makes a turn (right spin turn) toward the front right.

When the first operating lever 171 is tilted to the left, pilot pressure is generated in the first pilot valve 31 and the second pilot valve 32, and pilot oil is supplied to the following pilot oil passages. That is, the pilot pressure generated by the first pilot valve 31 passes through the first input oil passage 31a and the fourth output oil passage (fourth pilot oil passage) 61a, and the reverse input port 26b of the first traveling hydraulic pump 26L. Is supplied to. Further, the pilot pressure generated by the second pilot valve 32 passes through the second input oil passage 32a and the fifth output oil passage (fifth pilot oil passage) 62a, and the forward input port 26c of the second traveling hydraulic pump 26R is used. Is supplied to. As a result, the second traveling hydraulic motor 27R is rotationally driven to the forward side, and the second traveling device 12 is driven forward. Further, the first traveling hydraulic motor 27L is rotationally driven to the reverse side, and the first traveling device 11 is driven backward. At this time, the work vehicle 1 makes a turn (left spin turn) toward the left front.

The first pilot valve 31 when the first operating lever 171 is tilted to the rear left side, the second pilot valve 32 when tilted to the front left side, the third pilot valve 33 when tilted to the front right side, and the rear right side. When tilted to, a pilot pressure is generated in each of the fourth pilot valves 34, and pilot oil is supplied to the following pilot oil passages. That is, when the first operating lever 171 is tilted to the rear left side, only the first pilot valve 31 is pressed by the first operating lever 171 and the pilot pressure generated by the first pilot valve 31 is the first traveling hydraulic pressure. It is supplied to the reverse input port 26b of the pump 26L. As a result, the first traveling hydraulic motor 27L is rotationally driven to the reverse side, and only the first traveling device 11 is driven backward. At this time, the work vehicle 1 makes a turn toward the right rear (right rear pivot turn). Similarly, when the first operation lever 171 is tilted forward and to the left, only the second traveling device 12 is driven forward, and the work vehicle 1 makes a turn toward the left front (left front pivot turn). .. Further, when the first operation lever 171 is tilted to the rear right side, only the second traveling device 12 is driven backward, and the work vehicle 1 makes a turn toward the left rear (left rear pivot turn), and the second When the 1 operation lever 171 is tilted forward and to the right, only the first traveling device 11 is driven forward, and the work vehicle 1 makes a turn toward the right front (right front pivot turn).

Next, when the second operating lever 172 is tilted forward, a pilot pressure is generated in the sixth pilot valve 44, and pilot oil is supplied to the following pilot oil passages. That is, this pilot pressure is supplied to the arm lowering input port 28a of the arm operation control valve 28 via the sixth input oil passage 44a and the first output oil passage (first pilot oil passage) 66a. As a result, the arm cylinder 156 is reduced and the arm 154 is swung downward.

When the second operating lever 172 is tilted backward, a pilot pressure is generated in the fifth pilot valve 42, and pilot oil is supplied to the following pilot oil passages. That is, this pilot pressure is supplied to the arm raising input port 28b of the arm operation control valve 28 via the fifth input oil passage 42a and the second output oil passage (second pilot oil passage) 65a. As a result, the arm cylinder 156 is extended and the arm 154 is swung upward.

When the second operating lever 172 is tilted to the right, a pilot pressure is generated in the eighth pilot valve 41, and pilot oil is supplied to the following pilot oil passages. That is, this pilot pressure is supplied to the attachment lowering input port 23a of the attachment operation control valve 23 via the eighth input oil passage 41a. As a result, the attachment cylinder is extended and the attachment (as an example, the bucket) 164 is swung downward.

When the second operating lever 172 is tilted to the left, a pilot pressure is generated in the seventh pilot valve 43, and this pilot pressure is used to raise the attachment of the attachment operation control valve 23 via the seventh input oil passage 43a. It is supplied to the input port 23b. As a result, the attachment cylinder is reduced and the attachment (as an example, the bucket) 164 is swung upward.

Subsequently, the case where the second operation pattern is set will be described with reference to FIGS. 4 and 5. When the first operating lever 171 is tilted forward, pilot pressure is generated in the second pilot valve 32 and the third pilot valve 33, and pilot oil is supplied to the following pilot oil passages. That is, these pilot pressures are input to the input ports 52 and 53 of the selector valve 50. Of the pilot pressures input to the input ports 52 and 53, the high pressure pilot pressure is the first via the second shuttle valve 72, the output port 63, and the third output oil passage (third pilot oil passage) 63a. It is supplied to the forward input port 26a of the traveling hydraulic pump 26L. As a result, the first traveling hydraulic motor 27L is rotationally driven to the forward side, and only the first traveling device 11 is driven forward. At this time, the work vehicle 1 makes a turn toward the right front (right front pivot turn).

At this time, a part of the pilot pressure generated by the second pilot valve 32 and input to the input port 52 of the selector valve 50 is the first shuttle valve 71, the output port 65, and the second output oil passage (the second output oil passage). It is supplied to the arm raising input port 28b of the arm operation control valve 28 via the second pilot oil passage) 65a. Further, a part of the pilot pressure generated by the third pilot valve 33 and input to the input port 53 of the selector valve 50 is the third shuttle valve 73, the output port 66, and the first output oil passage (first pilot). It is supplied to the arm lowering input port 28a of the arm operation control valve 28 via the oil passage) 66a. Since the pilot pressures input to the arm raising input port 28b of the arm operating control valve 28 and the arm lowering input port 28a of the arm operating control valve 28 are almost the same, the arm operating control valve 28 The spool is held in a neutral position.

When the first operating lever 171 is tilted backward, pilot pressure is generated in the first pilot valve 31 and the fourth pilot valve 34, and pilot oil is supplied to the following pilot oil passages. That is, these pilot pressures are input to the input ports 51 and 54 of the selector valve 50. Of the pilot pressures input to the input ports 51 and 54, the high pressure pilot pressure is the first via the fourth shuttle valve 74, the output port 61, and the fourth output oil passage (fourth pilot oil passage) 61a. It is supplied to the reverse input port 26b of the traveling hydraulic pump 26L. As a result, the first traveling hydraulic motor 27L is rotationally driven to the reverse side, and only the first traveling device 11 is driven backward. At this time, the work vehicle 1 makes a turn toward the right rear (right rear pivot turn).

At this time, a part of the pilot pressure generated by the first pilot valve 31 and input to the input port 51 of the selector valve 50 is the first shuttle valve 71, the output port 65, and the second output oil passage (the second output oil passage). It is supplied to the arm raising input port 28b of the arm operation control valve 28 via the second pilot oil passage) 65a. Further, a part of the pilot pressure generated by the fourth pilot valve 34 and input to the input port 54 of the selector valve 50 is the third shuttle valve 73, the output port 66, and the first output oil passage (first pilot). It is supplied to the arm lowering input port 28a of the arm operation control valve 28 via the oil passage) 66a. Since the pilot pressures input to the arm raising input port 28b of the arm operating control valve 28 and the arm lowering input port 28a of the arm operating control valve 28 are almost the same, the arm operating control valve 28 The spool is held in a neutral position.

When the first operating lever 171 is tilted to the right, pilot pressure is generated in the third pilot valve 33 and the fourth pilot valve 34, and pilot oil is supplied to the following pilot oil passages. That is, these pilot pressures are input to the input ports 53 and 54 of the selector valve 50. Of the pilot pressures input to the input ports 53 and 54, the high pressure pilot pressure operates the arm via the third shuttle valve 73, the output port 66, and the first output oil passage (first pilot oil passage) 66a. It is supplied to the arm lowering input port 28a of the control valve 28. As a result, the arm cylinder 156 is reduced and the arm 154 is swung downward.

At this time, a part of the pilot pressure generated by the third pilot valve 33 and input to the input port 53 of the selector valve 50 is the second shuttle valve 72, the output port 63, and the third output oil passage (the third output oil passage). It is supplied to the forward input port 26a of the first traveling hydraulic pump 26L via the third pilot oil passage) 63a. Further, a part of the pilot pressure generated by the fourth pilot valve 34 and input to the input port 54 of the selector valve 50 is the fourth shuttle valve 74, the output port 61, and the fourth output oil passage (fourth pilot). It is supplied to the reverse input port 26b of the first traveling hydraulic pump 26L via the oil passage) 61a. The pilot pressures input to the forward input port 26a of the first traveling hydraulic pump 26L and the reverse input port 26b of the first traveling hydraulic pump 26L are almost the same, and the first traveling hydraulic pumps 26L to the first. The pressure oil is not supplied to the traveling hydraulic motor 27L, and the first traveling hydraulic motor 27L is not rotationally driven.

When the first operating lever 171 is tilted to the left, pilot pressure is generated in the first pilot valve 31 and the second pilot valve 32, and pilot oil is supplied to the following pilot oil passages. That is, these pilot pressures are input to the input ports 51 and 52 of the selector valve 50. Of the pilot pressures input to the input ports 51 and 52, the high-pressure pilot pressure operates the arm via the first shuttle valve 71, the output port 65, and the second output oil passage (second pilot oil passage) 65a. It is supplied to the arm raising input port 28b of the control valve 28. As a result, the arm cylinder 156 is extended and the arm 154 is swung upward.

At this time, a part of the pilot pressure generated by the first pilot valve 31 and input to the input port 51 of the selector valve 50 is the fourth shuttle valve 74, the output port 61, and the fourth output oil passage ( It is supplied to the reverse input port 26b of the first traveling hydraulic pump 26L via the fourth pilot oil passage) 61a. Further, a part of the pilot pressure generated by the second pilot valve 32 and input to the input port 52 of the selector valve 50 is the second shuttle valve 72, the output port 63, and the third output oil passage (third pilot). It is supplied to the forward input port 26a of the first traveling hydraulic pump 26L via the oil passage) 63a. The pilot pressures input to the reverse input port 26b of the first traveling hydraulic pump 26L and the forward input port 26a of the first traveling hydraulic pump 26L are almost the same, and the first traveling hydraulic pumps 26L to the first. The pressure oil is not supplied to the traveling hydraulic motor 27L, and the first traveling hydraulic motor 27L is not rotationally driven.

Further, when the first operating lever 171 is tilted to the rear left side, the first pilot valve 31, when tilted to the front left side, the second pilot valve 32, and when tilted to the front right side, the third pilot valve 33, When tilted to the rear right, pilot pressure is generated in the fourth pilot valve 34, and pilot oil is supplied to the following pilot oil passages. That is, when the first operating lever 171 is tilted to the rear left side, only the first pilot valve 31 is pressed by the first operating lever 171 and the pilot pressure generated by the first pilot valve 31 is the first traveling. It is supplied to the reverse input port 26b of the hydraulic pump 26L and the arm raising input port 28b of the arm operation control valve 28. As a result, the first traveling hydraulic motor 27L is rotationally driven to the reverse side, only the first traveling device 11 is driven backward (performing a right rear pivot turn), the arm cylinder 156 is extended, and the arm 154 is moved upward. Is rocked. Similarly, when the first operating lever 171 is tilted forward and to the left, only the first traveling device 11 is driven forward (performing a right front pivot turn), the arm cylinder 156 is extended, and the arm 154 is extended. It is swung upward. Further, when the first operating lever 171 is tilted to the rear right side, only the second traveling device 12 is driven backward (performing a left rear pivot turn), the arm cylinder 156 is reduced, and the arm 154 is moved downward. It is rocked. Further, when the first operation lever 171 is tilted forward and to the right, only the second traveling device 12 is driven forward (performs a left front pivot turn), the arm cylinder 156 is reduced, and the arm 154 is moved downward. It is rocked.

When the second operating lever 172 is tilted forward, a pilot pressure is generated in the sixth pilot valve 44, and pilot oil is supplied to the following pilot oil passages. That is, this pilot pressure is supplied to the forward input port 26c of the second traveling hydraulic pump 26R via the input port 56, the output port 62, and the fifth output oil passage (fifth pilot oil passage) 62a. As a result, the second traveling hydraulic motor 27R is rotationally driven to the forward side, and only the second traveling device 12 is driven forward. At this time, the work vehicle 1 makes a turn toward the left front (left front pivot turn).

When the second operating lever 172 is tilted backward, a pilot pressure is generated in the fifth pilot valve 42, and pilot oil is supplied to the following pilot oil passages. That is, this pilot pressure is supplied to the reverse input port 26d of the second traveling hydraulic pump 26R via the input port 55, the output port 64, and the sixth output oil passage (sixth pilot oil passage) 64a. As a result, the second traveling hydraulic motor 27R is rotationally driven to the reverse side, and only the second traveling device 12 is driven backward. At this time, the work vehicle 1 makes a turn toward the left rear (left rear pivot turn).

It should be noted that when the second operation lever 172 is tilted to the right and when the second operation lever 172 is tilted to the left, it is the same as when the first operation pattern is set. The repetitive description is omitted.

In this way, for each of the first operating lever 171 and the second operating lever 172, the combination of the tilting operation and the hydraulic actuator (control valve) that operates in response to the tilting operation, that is, the configuration of the pilot oil passage (connection pattern). ) Is set in a plurality of ways (two ways in the present embodiment), and the configuration (connection pattern) is switched via the selector valve 50. As an example, the selector valve 50 is switched by using the switching lever 59 provided in the cockpit 16, but the switching is not limited to this, and the switch provided in the operation panel 174, the cluster 176, or the like. And an actuator (solenoid valve or the like) connected to the selector valve 50 may be used (not shown).

Here, the work vehicle 1 makes it possible to realize the "lever pattern change technology" as described above. Furthermore, if it becomes possible to realize "automatic transmission technology at the time of turn", workability can be significantly improved.

As mentioned above, "automatic shift technology at turn" means that when a turn operation such as a spin turn is performed while driving in a high-speed mode with a small torque, the mode is automatically switched to a low-speed mode with a large torque. It is a technology. Therefore, it is necessary to determine the state in which a turn operation such as a spin turn has been performed.

Here, in the work vehicle 1 according to the present embodiment, in order to realize the "lever pattern change technology" at the same time, a plurality of (here, two) pilot hydraulic circuits that are switched by the selector valve 50 are provided. It is configured to be prepared. Therefore, according to the conventional design concept, if a plurality of shuttle valves are provided downstream of the selector valve 50 and a pressure switch is provided in each pilot oil passage, the traveling devices 11 and 12 are in the forward state or the reverse state. It is not impossible to judge whether it is a state or not. However, if a plurality of shuttle valves are provided, the mechanism / hydraulic circuit is naturally complicated, which leads to an increase in equipment cost.

Therefore, in the present embodiment, by devising the following configuration, it is aimed to realize it at low cost with a simple mechanism / hydraulic circuit.

First, as an apparatus configuration, the first pilot oil passage 66a is, for example, at a position downstream of the selector valve 50 and upstream of the arm lowering input port 28a, without interposing a complicated determination circuit. A first pressure sensor 81 for detecting the pressure value of the pilot oil supplied to the first pilot oil passage 66a is provided. Further, in the second pilot oil passage 65a, for example, at a position downstream of the selector valve 50 and upstream of the arm raising input port 28b, the second pilot oil is provided without a complicated determination circuit. A second pressure sensor 82 for detecting the pressure value of the pilot oil supplied to the passage 65a is provided. Further, in the third pilot oil passage 63a, as an example, a complicated determination circuit is interposed at a position downstream of the selector valve 50 and at a position upstream of the forward input port 26a of the first traveling hydraulic pump 26L. Instead, a third pressure sensor 83 for detecting the pressure value of the pilot oil supplied to the third pilot oil passage 63a is provided. Further, in the fourth pilot oil passage 61a, for example, at a position downstream of the selector valve 50 and upstream of the reverse input port 26b of the first traveling hydraulic pump 26L, without interposing a complicated determination circuit. A fourth pressure sensor 84 for detecting the pressure value of the pilot oil supplied to the fourth pilot oil passage 61a is provided. Each pressure value detected by these pressure sensors (first pressure sensor 81 to fourth pressure sensor 84) is transmitted to the control device 140.

As described above, the first pressure sensor 81, the second pressure sensor 82, the third pressure sensor 83, and the fourth pressure sensor 84 are arranged at positions downstream of the selector valve 50 in the pilot oil passage provided therein. Since the processing routine for detecting / detecting can be simplified by the provided configuration, the processing speed in the control device 140 can be improved.

Next, in the fifth pilot oil passage 62a, for example, at a position downstream of the selector valve 50 and upstream of the forward input port 26c of the second traveling hydraulic pump 26R, no complicated determination circuit is interposed. Is provided with a first pressure switch 91 that detects whether or not a predetermined pressure is applied by the pilot oil supplied to the fifth pilot oil passage 62a, that is, whether or not a predetermined pressure is applied. Further, in the sixth pilot oil passage 64a, for example, at a position downstream of the selector valve 50 and upstream of the reverse input port 26d of the second traveling hydraulic pump 26R, without interposing a complicated determination circuit. A second pressure switch 92 is provided to detect whether or not a predetermined pressure is applied by the pilot oil supplied to the sixth pilot oil passage 64a, that is, whether or not a predetermined pressure is applied. The presence / absence of application of each pressure detected by these pressure switches (first pressure switch 91, second pressure switch 92) is transmitted to the control device 140 as a signal.

Next, the flowchart of FIG. 6 shows an outline of the operation control (here, the control related to the “automatic transmission at the time of turn”) performed by the control device 140 according to the present embodiment.

First, the control device 140 carries out a step of determining whether or not the traveling mode is the "high-speed mode" (step A1). Here, if it is determined that the traveling mode is the "high-speed mode", it may be necessary to control the automatic transmission, so the process proceeds to the following steps. On the other hand, when it is determined that the traveling mode is not the "high-speed mode", it is not necessary to control the automatic transmission, so that the processing flow reaches the end.

Next, the control device 140 carries out a step of determining whether the first traveling device 11 is in the forward state or the reverse state (step A2). In the present embodiment, on the downstream side of the selector valve 50 and on the upstream side of the forward input port 26a and the reverse input port 26b of the first traveling hydraulic pump 26L, without interposing a complicated determination circuit. , The determination is made possible by using the pressure value detected by the third pressure sensor 83 and the fourth pressure sensor 84. Specifically, when the pressure value of the third pressure sensor 83> the pressure value of the fourth pressure sensor 84, the first traveling device 11 determines that the traveling device 11 is in the forward state. On the other hand, when the pressure value of the third pressure sensor 83 <the pressure value of the fourth pressure sensor 84, the first traveling device 11 determines that the vehicle is in the reverse state.

At the same time, the control device 140 carries out a step of determining whether the second traveling device 12 is in the forward state or the reverse state (step A3). In the present embodiment, on the downstream side of the selector valve 50 and on the upstream side of the forward input port 26c and the reverse input port 26d of the second traveling hydraulic pump 26R, without interposing a complicated determination circuit. , The determination is made possible by using the signal of the presence / absence of application of the predetermined pressure detected by the first pressure switch 91 and the second pressure switch 92. Specifically, when the signal applied by the first pressure switch 91 to the predetermined pressure is "Yes" (the signal applied by the second pressure switch 92 is "None" due to the circuit configuration), the second run is performed. The device 12 determines that it is in the forward state. On the other hand, when the signal applied by the second pressure switch 92 to the predetermined pressure is "Yes" (the signal applied by the first pressure switch 91 is "None" due to the circuit configuration), the second traveling device 12 Is determined to be in the reverse state.

Next, in the control device 140, when the first traveling device 11 is in the forward state and the second traveling device 12 is in the reverse state, and when the first traveling device 11 is in the reverse state and the second traveling device 12 is in the forward state. If there is, a step of determining that the "spin turn" operation has been performed by any of the above is performed (step A4).

Next, when the control device 140 determines that the above-mentioned "spin turn" operation has been performed, the control device 140 sets the speed change mechanism to the "high-speed mode" without interlocking with the first operation lever 171 and the second operation lever 172. A step of performing control for switching from "to" to "low speed mode" is performed (step A5).

As a modification, the first operation lever 171 and the second operation lever 172 are not interlocked with each other even when the "pivot turn" operation is performed in addition to the state where the "spin turn" operation is performed. The speed change mechanism may be configured to carry out a step of performing control for switching from the “high speed mode” to the “low speed mode” (not shown). In that case, when the first traveling device 11 is in the forward or backward state and the second traveling device 12 is in the stopped state, and when the first traveling device 11 is in the stopped state and the second traveling device 12 is in the forward state. Alternatively, in the case of the reverse state, a step of determining that the "pivot turn" operation has been performed by falling under any of the above is performed.

As described above, according to the work vehicle 1 according to the present embodiment, both the "lever pattern change technology" and the "automatic shift technology at the time of turn" can be realized by a simple mechanism / hydraulic circuit, in particular. It is possible without providing a complicated determination circuit in which a plurality of shuttle valves are interposed on the downstream side of the selector valve 50 and on the upstream side of each input port. In addition to this, it is also possible to realize the "float technology" shown below in such a simple mechanism / hydraulic circuit.

Here, the "float technology" means that the pressure oil supplied to the arm cylinder 156 that raises and lowers the arm 154 is discharged to a hydraulic oil tank (not shown) to lower the arm 154 and attach the attachment 164. It refers to a technology (function) that makes the ground so that it can follow the ground (float state).

The work vehicle 1 according to the present embodiment includes a float switching mechanism having a float operation control valve 29 that switches between the float state and the float release state with respect to the arm 154.

Here, an outline of the operation control (here, the control related to the “float technique”) performed by the control device 140 according to the present embodiment is shown in the flowchart of FIG.

First, the control device 140 carries out a step of determining whether the float switch is in the on state or the off state (step B1). Here, if it is determined that the float switch is in the ON state, the process proceeds to the following steps toward the float operation. On the other hand, when it is determined that the float switch is in the off state, the processing flow reaches the end.

Next, the control device 140 carries out a step of determining whether the arm 154 is in the descending operation state or the ascending operation state (step B2). In the present embodiment, a complicated determination circuit is interposed on the downstream side of the selector valve 50 and on the upstream side of the arm lowering input port 28a and the arm raising input port 28b of the arm operation control valve 28. Instead, the pressure value detected by the first pressure sensor 81 and the second pressure sensor 82 can be used for the determination. Specifically, when the pressure value of the first pressure sensor 81> the pressure value of the second pressure sensor 82, it is determined that the arm 154 is in the lowering operation state. On the other hand, when the pressure value of the first pressure sensor 81 <the pressure value of the second pressure sensor 82, it is determined that the arm 154 is in the ascending operation state.

Next, the control device 140 carries out a step of determining that the operation for executing the float operation has been performed when the float switch is on and the arm 154 is in the descending operation state (step B3). ).

Next, when the control device 140 determines that the operation for executing the float operation is performed, the control device 140 performs a step of controlling the float switching mechanism to be switched to the float state (step B4). Specifically, the control valve 29 for float operation is controlled to switch to a circuit that is in a float state.

As described above, according to the work vehicle 1 according to the present embodiment, all of the "lever pattern change technology", "automatic transmission at turn technology", and "float technology" are realized by a simple mechanism / hydraulic circuit. It is possible.

(Second embodiment)
Subsequently, the work vehicle 1 according to the second embodiment of the present invention will be described. The work vehicle 1 according to the present embodiment has the same basic configuration as the first embodiment described above, but has a difference in particular regarding the configuration of the pilot oil passage and the control by the control device 140. Hereinafter, the present embodiment will be described with a focus on the differences.

A schematic diagram (circuit diagram) of the hydraulic circuit system of the work vehicle 1 according to the present embodiment is shown in FIG. 8 (a diagram corresponding to FIG. 4, where FIG. 8 (a) is an operation pattern and FIG. 8 (b) is hydraulic pressure. The circuit configuration) is shown. Unlike the first embodiment described above, in the fifth pilot oil passage 62a, for example, at a position downstream of the selector valve 50 and upstream of the forward input port 26a of the first traveling hydraulic pump 26L. At the position, a fifth pressure sensor 85 is provided to detect the pressure value of the pilot oil supplied to the fifth pilot oil passage 62a without interposing a complicated determination circuit. Further, in the sixth pilot oil passage 64a, for example, at a position downstream of the selector valve 50 and upstream of the reverse input port 26b of the first traveling hydraulic pump 26L, without interposing a complicated determination circuit. A sixth pressure sensor 86 for detecting the pressure value of the pilot oil supplied to the sixth pilot oil passage 64a is provided. The respective pressure values detected by the fifth pressure sensor 85 and the sixth pressure sensor 86 are the same as the respective pressure values detected by the first pressure sensor 81 to the fourth pressure sensor 84 described above. It is transmitted to 140.

Further, as a difference in the processing flow of the operation control performed by the control device 140 according to the present embodiment (here, the control related to the "automatic transmission at the time of turn"), instead of the step A3 in the first embodiment described above, Step C1 shown below is executed. Specifically, as the step C1, the control device 140 carries out a step of determining whether the second traveling device 12 is in the forward state or the reverse state. In the present embodiment, on the downstream side of the selector valve 50 and on the upstream side of the forward input port 26c and the reverse input port 26d of the second traveling hydraulic pump 26R, without interposing a complicated determination circuit. , The determination is made possible by using the pressure value detected by the 5th pressure sensor 85 and the 6th pressure sensor 86. Specifically, when the pressure value of the fifth pressure sensor 85> the pressure value of the sixth pressure sensor 86, the second traveling device 12 determines that the traveling device 12 is in the forward state. On the other hand, when the pressure value of the fifth pressure sensor 85 <the pressure value of the sixth pressure sensor 86, the second traveling device 12 determines that the vehicle is in the reverse state.

As described above, the same effect as that of the above-mentioned first embodiment can be obtained by this embodiment as well.

Here, in the present embodiment, the pressure sensors are arranged in the fifth pilot oil passage 62a and the sixth pilot oil passage 64a. Therefore, it can be a factor that increases the equipment cost as compared with the above-mentioned first embodiment in which the pressure switch is arranged in the oil passage. However, on the other hand, the following techniques (functions) unique to this embodiment can be realized.

Specifically, a technology that automatically switches to a high-torque low-speed mode when the running load (engine load) becomes high while driving in a low-torque high-speed mode (hereinafter, "automatic at high load"). (Sometimes referred to as "shift technology") can be realized. Therefore, as compared with the first embodiment described above, the operational burden on the operator can be reduced, and the workability can be further improved.

First, as a device configuration that enables the realization of the technology, a rotation speed sensor (not shown) for detecting the rotation speed of each of the first traveling hydraulic motor 27L and the second traveling hydraulic motor 27R is provided. Each detected value (that is, rotation speed) detected by the rotation speed sensor is transmitted to the control device 140.

Here, the flowchart of FIG. 9 shows an outline of the operation control (here, the control related to the “automatic transmission technique at high load”) performed by the control device 140 according to the present embodiment.

First, the control device 140 carries out a step of determining whether or not the traveling mode is the "high-speed mode" (step D1). Here, if it is determined that the traveling mode is the "high-speed mode", it may be necessary to control the automatic transmission, so the process proceeds to the following steps. On the other hand, when it is determined that the traveling mode is not the "high-speed mode", it is not necessary to control the automatic transmission, so that the processing flow reaches the end.

Next, in the control device 140, at least one pressure value exceeds a predetermined value for each pressure value detected by the third pressure sensor 83, the fourth pressure sensor 84, the fifth pressure sensor 85, and the sixth pressure sensor 86. A step of determining whether or not the pressure is present is performed (step D2).

Next, the control device 140 carries out a step of determining whether or not the rotation speed detected by the rotation speed sensor exceeds a predetermined value (step D3).

Next, when the control device 140 determines in step D1 that the pressure value exceeds the predetermined value, and when it determines in step D2 that the rotation speed does not exceed the predetermined value, "high load". The step of determining that the vehicle is in the traveling state of "" is carried out (step D4).

Next, when the control device 140 determines that the traveling state is the above-mentioned "high load", the speed change mechanism is changed from the "high speed mode" to "high speed mode" without interlocking with the first operation lever 171 and the second operation lever 172. A step of performing control for switching to the "low speed mode" is performed (step D5).

As described above, according to the work vehicle 1 according to the second embodiment, all of the "lever pattern change technology", "turn automatic transmission technology", "float technology", and "high load automatic transmission technology". Is made possible by a simple mechanism and hydraulic circuit.

As described above, according to the present invention, a work vehicle having at least both "lever pattern change technology" and "automatic shift technology at turn" and also having "float technology" and the like is provided with a simple mechanism and hydraulic pressure. The circuit can be realized at low cost.

The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the present invention. In particular, the explanation has been given by taking a crawler loader as an example of a work vehicle, but the description is not limited to this, and for example, other work vehicles such as a skid steer loader, a crawler carrier, and a power shovel are also used. It goes without saying that it can be applied in the same way.

1 Work vehicle 10 Body 11, 12 Traveling device 14 Working device 16 Control room 20 Engine 21 Pilot hydraulic pump 22 Crawler 24 Speed change control valve 26 Traveling hydraulic pump 27 Traveling hydraulic motor 28 Arm operation control valve 29 Float operation control valve 50 Selector valves 61a to 66a Pilot oil passages 81 to 86 Pressure sensors 91, 92 Pressure switch 140 Control device 142 Engine control unit (ECU)
154 Arm 164 Attachments 171, 172 Operating lever

Claims (6)

A work vehicle with an attachment attached to the arm to perform predetermined work.
With the drive source
The first traveling hydraulic pump, the second traveling hydraulic pump, and the pilot hydraulic pump driven by the drive source,
A first traveling hydraulic motor and a second traveling hydraulic motor driven by the pressure oil supplied from the first traveling hydraulic pump and the second traveling hydraulic pump, respectively.
A pair of first traveling device and second traveling device provided on the left and right sides of the vehicle body and driven by the first traveling hydraulic motor and the second traveling hydraulic motor, respectively.
A pilot oil passage that supplies pilot oil from the pilot hydraulic pump through the first traveling hydraulic pump, the second traveling hydraulic pump, and the control valve for arm operation.
The cockpit where workers board and control,
The arm, the first traveling device, and a control device for controlling the operation of the second traveling device are provided.
The cockpit is provided with a first operation lever and a second operation lever.
A first operation pattern in which the first operating device and the second traveling device are moved forward and backward by the first operating lever, and the arm is lowered and raised by the second operating lever, and the first operating lever. The pilot oil corresponds to a second operation pattern in which the first traveling device is moved forward and backward and the arm is lowered and raised, and the second traveling device is moved forward and backward by the second operating lever. A lever pattern switching mechanism with a selector valve that switches the path,
It is further equipped with a transmission mechanism that switches the driving mode between high-speed mode and low-speed mode.
As the pilot oil passage, a first pilot oil passage communicating with the arm lowering input port of the arm operation control valve, a second pilot oil passage communicating with the arm raising input port of the arm operation control valve, and the first pilot oil passage. The third pilot oil passage that communicates with the forward input port of the 1-travel hydraulic pump, the 4th pilot oil passage that communicates with the reverse input port of the 1st traveling hydraulic pump, and the forward input of the 2nd traveling hydraulic pump. It has a fifth pilot oil passage that communicates with the port and a sixth pilot oil passage that communicates with the reverse input port of the second traveling hydraulic pump.
The first pilot oil passage is provided with a first pressure sensor that detects the pressure value of the supplied pilot oil.
The second pilot oil passage is provided with a second pressure sensor that detects the pressure value of the supplied pilot oil.
The third pilot oil passage is provided with a third pressure sensor that detects the pressure value of the supplied pilot oil.
The fourth pilot oil passage is provided with a fourth pressure sensor that detects the pressure value of the supplied pilot oil.
The fifth pilot oil passage is provided with a first pressure switch that detects whether or not a predetermined pressure is applied by the supplied pilot oil.
The sixth pilot oil passage is provided with a second pressure switch that detects whether or not a predetermined pressure is applied by the supplied pilot oil.
The control device is
Based on the pressure values detected by the third pressure sensor and the fourth pressure sensor, it is determined whether the first traveling device is in the forward state or the reverse state.
Based on the presence or absence of application of the predetermined pressure detected by the first pressure switch and the second pressure switch, it is determined whether the second traveling device is in the forward state or the reverse state.
In either case, the first traveling device is in the forward state and the second traveling device is in the reverse state, and the first traveling device is in the reverse state and the second traveling device is in the forward state. A work vehicle characterized in that the speed change mechanism is controlled to be switched from a high-speed mode to a low-speed mode without interlocking with the first operation lever and the second operation lever. The first aspect of claim 1, wherein the first pressure sensor, the second pressure sensor, the third pressure sensor, and the fourth pressure sensor are arranged at positions downstream of the selector valve. Work vehicle. Further provided with a float switching mechanism having a control valve for float operation that switches between the float state and the float release state with respect to the arm.
The cockpit is provided with a float switch for the float operation of the arm.
The control device is
It is determined whether the float switch is on or off, and it is determined.
Based on the pressure values detected by the first pressure sensor and the second pressure sensor, it is determined whether the arm is in the lowering operation state or the ascending operation state.
The work vehicle according to claim 1 or 2, wherein when the float switch is on and the arm is in the descending operation state, the float switching mechanism is controlled to switch to the float state. The control device is
Based on the pressure values detected by the third pressure sensor and the fourth pressure sensor, it is determined whether the first traveling device is in the forward state, the reverse state, or the stopped state.
Based on the presence or absence of application of the predetermined pressure detected by the first pressure switch and the second pressure switch, it is determined whether the second traveling device is in the forward state, the reverse state, or the stopped state.
When one of the first traveling device and the second traveling device is in the forward or reverse state and the other is in the stopped state, the speed change mechanism is moved at high speed without interlocking with the first operation lever and the second operation lever. The work vehicle according to any one of claims 1 to 3, wherein the control for switching from the mode to the low speed mode is performed. A work vehicle with an attachment attached to the arm to perform predetermined work.
With the drive source
The first traveling hydraulic pump, the second traveling hydraulic pump, and the pilot hydraulic pump driven by the drive source,
A first traveling hydraulic motor and a second traveling hydraulic motor driven by the pressure oil supplied from the first traveling hydraulic pump and the second traveling hydraulic pump, respectively.
A pair of first traveling device and second traveling device provided on the left and right sides of the vehicle body and driven by the first traveling hydraulic motor and the second traveling hydraulic motor, respectively.
A pilot oil passage that supplies pilot oil from the pilot hydraulic pump through the first traveling hydraulic pump, the second traveling hydraulic pump, and the control valve for arm operation.
The cockpit where workers board and control,
The arm, the first traveling device, and a control device for controlling the operation of the second traveling device are provided.
The cockpit is provided with a first operation lever and a second operation lever.
A first operation pattern in which the first operating device and the second traveling device are moved forward and backward by the first operating lever, and the arm is lowered and raised by the second operating lever, and the first operating lever. The pilot oil corresponds to a second operation pattern in which the first traveling device is moved forward and backward and the arm is lowered and raised, and the second traveling device is moved forward and backward by the second operating lever. A lever pattern switching mechanism with a selector valve that switches the path,
It is further equipped with a transmission mechanism that switches the driving mode between high-speed mode and low-speed mode.
As the pilot oil passage, a first pilot oil passage communicating with the arm lowering input port of the arm operation control valve, a second pilot oil passage communicating with the arm raising input port of the arm operation control valve, and the first pilot oil passage. The third pilot oil passage that communicates with the forward input port of the 1-travel hydraulic pump, the 4th pilot oil passage that communicates with the reverse input port of the 1st traveling hydraulic pump, and the forward input of the 2nd traveling hydraulic pump. It has a fifth pilot oil passage that communicates with the port and a sixth pilot oil passage that communicates with the reverse input port of the second traveling hydraulic pump.
The first pilot oil passage is provided with a first pressure sensor that detects the pressure value of the supplied pilot oil.
The second pilot oil passage is provided with a second pressure sensor that detects the pressure value of the supplied pilot oil.
The third pilot oil passage is provided with a third pressure sensor that detects the pressure value of the supplied pilot oil.
The fourth pilot oil passage is provided with a fourth pressure sensor that detects the pressure value of the supplied pilot oil.
The fifth pilot oil passage is provided with a fifth pressure sensor that detects the pressure value of the supplied pilot oil.
The sixth pilot oil passage is provided with a sixth pressure sensor that detects the pressure value of the pilot oil to be supplied.
The control device is
Based on the pressure values detected by the third pressure sensor and the fourth pressure sensor, it is determined whether the first traveling device is in the forward state or the reverse state.
Based on the pressure values detected by the fifth pressure sensor and the sixth pressure sensor, it is determined whether the second traveling device is in the forward state or the reverse state.
In either case, the first traveling device is in the forward state and the second traveling device is in the reverse state, and the first traveling device is in the reverse state and the second traveling device is in the forward state. A work vehicle characterized in that the speed change mechanism is controlled to be switched from a high-speed mode to a low-speed mode without interlocking with the first operation lever and the second operation lever. Further equipped with a rotation speed sensor for detecting the rotation speed of each of the first traveling hydraulic motor and the second traveling hydraulic motor.
The control device is
When the pressure value detected by the third pressure sensor, the fourth pressure sensor, the fifth pressure sensor, and the sixth pressure sensor exceeds a predetermined value.
Moreover, when the rotation speed detected by the rotation speed sensor does not exceed a predetermined value,
The work vehicle according to claim 5, wherein the gear shifting mechanism is controlled to switch from a high-speed mode to a low-speed mode without interlocking with the first operation lever and the second operation lever.

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