WO2017221449A1

WO2017221449A1 - Construction machine

Info

Publication number: WO2017221449A1
Application number: PCT/JP2017/002524
Authority: WO
Inventors: 小野純弥; 岡崎耕平; 閑野宏信
Original assignee: ヤンマー株式会社
Priority date: 2016-06-20
Filing date: 2017-01-25
Publication date: 2017-12-28
Also published as: JP2017227231A

Abstract

The present invention relates to a construction machine equipped with: travel-use variable-capacity hydraulic pumps (PL, PR), the discharge volumes of which are modified according to the operation of a travel operation implement (47); travel-use variable-capacity hydraulic motors (ML, MR) in fluid connection with the travel-use hydraulic pumps (PL, PR); a motor capacity selection unit (66) for selecting one motor capacity from among multiple levels for the travel-use hydraulic motors (ML, MR); a motor capacity selection operation implement (Sw) for operating the motor capacity selection unit (66); an operation detection unit (S) for detecting the operation of the travel operation implement (47); and a control unit. When the operation detection unit (S) does not detect the operation of the travel operation implement (47), the construction machine overrides the selection result of the motor capacity selection unit (66) and sets the motor capacity of the travel-use hydraulic motors (ML, MR) to a large capacity gear. As a result, even if the machine body descends on sloped ground due to leakage of hydraulic pressure when the travel-use operation implement (47) is not operated, that is, when the travel operation implement (47) is in the neutral position and the machine body is in a stopped-travel state, the present invention is able to limit the amount of said descent.

Description

Construction machinery

The present invention relates to a construction machine, and more particularly to a construction machine in which the motor capacity of a traveling hydraulic motor is forcibly set to a large capacity stage (low speed stage) in a traveling stop state.

Conventionally, as one form of construction machinery, a variable displacement travel hydraulic pump whose discharge capacity is changed in response to operation of the travel operation tool, and a fluid connection to the travel hydraulic pump, a multistage motor capacity is achieved. Some are equipped with a variable displacement traveling hydraulic motor that can be switched. However, in such a construction machine, when traveling on an inclined ground (especially uphill) is stopped, the machine body descends along the inclined ground due to leakage of hydraulic pressure from a traveling hydraulic pump or traveling hydraulic motor. There is. At this time, if the traveling of the hydraulic motor for traveling is stopped while the motor capacity is set to a small capacity stage (high speed stage), it will descend at the high speed stage during the stop time, so the descending amount will increase accordingly. There is a risk of an unexpected situation. In that regard, Patent Document 1 discloses a technique for preventing reverse running at the time of starting by detecting the amount of inclination of the airframe and switching the traveling hydraulic motor to a low speed when the inclination is large.

JP 2002-39374 A

However, in Patent Document 1, since switching to the low speed stage is determined by detecting the amount of inclination of the aircraft, when traveling on rough terrain where the amount of inclination of the aircraft changes frequently, an unexpected shift of the operator Control can be made and can cause fear to the operator.

In view of this, the present invention provides a high-capacity stage (low speed stage) when the travel operating tool is not operated, that is, when the travel operating tool is in the neutral position and the aircraft is in a travel stop state. It is an object of the present invention to provide a construction machine that can suppress the descending amount even when the machine body descends along the slope due to hydraulic leakage.

The invention described in claim 1
A variable displacement travel hydraulic pump whose discharge capacity is changed in accordance with the operation of the travel operation tool, and a variable displacement travel fluid pump that is fluidly connected to the travel hydraulic pump and can be switched to a multistage motor capacity. A traveling hydraulic motor, a motor capacity selection unit that selects one of the motor capacities of the plurality of stages of the traveling hydraulic motor, a motor capacity selection operation unit that operates the motor capacity selection unit, and an operation of the travel operation tool An operation detection unit for detecting the control unit, and a control unit that connects the operation detection unit and the motor capacity selection operation unit to the input side while connecting the motor capacity selection unit to the output side,
When the operation detection unit does not detect the operation of the travel operation tool, the motor capacity of the travel hydraulic motor is set to a large capacity stage in preference to the selection result of the motor capacity selection unit. .

The invention according to claim 2 is the invention according to claim 1,
When a small capacity stage is selected by the motor capacity selection unit via the motor capacity selection operation unit, the operation detection unit is not detected from the state in which the operation of the travel operation tool is detected. In this case, the motor capacity is stopped while being gradually shifted down from a small capacity stage to a large capacity stage.

Invention of Claim 3 is invention of Claim 1, Comprising:
When a small capacity stage is selected by the motor capacity selection unit via the motor capacity selection operation unit, the operation detection unit has detected a state in which the operation of the travel operation tool is not detected. In this case, the motor capacity is increased while gradually shifting up from a large capacity stage to a small capacity stage.

The invention according to claim 4 is the invention according to any one of claims 1 to 3,
The motor capacity selection operation unit is provided in a travel operation tool, and can be selected by a fingertip of a hand holding the travel operation tool.

According to the present invention, when the travel operation tool is not operated, that is, when the travel operation tool is in the neutral position and the aircraft is in the travel stop state, the motor capacity of the travel hydraulic motor is a large capacity stage (low speed stage). ), The amount of lowering can be suppressed even if the aircraft descends along the slope due to hydraulic leak. Therefore, it is possible to avoid an unexpected situation by the operator recognizing the descent of the aircraft and quickly operating the operation tool for braking the parking brake while the aircraft is descending at a low speed. Can do.

The left view of the construction machine which concerns on one Embodiment of this invention. The front view of the construction machine which concerns on one Embodiment of this invention. The perspective view from the left front of the construction machine which concerns on one Embodiment of this invention. The expansion perspective view from the left front of the operation part with which the construction machine concerning one embodiment of the present invention equips. The arrangement explanatory view of separation type left HST and separation type right HST with which the construction machine concerning one embodiment of the present invention is equipped. The hydraulic circuit diagram with which the construction machine which concerns on one Embodiment of this invention is equipped. The control block diagram with which the construction machine which concerns on one Embodiment of this invention is equipped. The flowchart of the control program with which the construction machine which concerns on one Embodiment of this invention is equipped.

Embodiments according to the present invention will be described below with reference to the drawings. A shown in FIGS. 1 to 3 is a hydraulically driven construction machine according to the present embodiment. In the construction machine A, as shown in FIGS. 1 to 3, a base 11 is installed between a pair of left and right crawler

type traveling units

10 and 10. On the base 11, a cargo bed 13 formed in a rectangular box shape with an upper opening is placed. A dump cylinder 14 is interposed between the base 11 and the loading platform 13, and the loading platform 13 is tilted backward about the tilting fulcrum 12 by the dump cylinder 14 so that the load can be discharged (dumped) backward. Yes. On the base 11, an overhanging machine body frame 15 is provided so as to project forward. On the overhanging machine body frame 15, a floor portion 16 is stretched on the left side, an operation unit 17 is provided on the floor portion 16, and a motor unit 18 is disposed on the right side. A canopy 19 is disposed directly above the operation unit 17 via a canopy support 34.

As shown in FIG. 5, the left traveling unit 10 is provided with a left traveling hydraulic motor ML at the front end portion of the traveling frame 20 extending in the front-rear direction, and a drive wheel 22 on the drive shaft 21 of the left traveling hydraulic motor ML. Is attached. A driven wheel 24 is attached to the rear end of the traveling frame 20 via a driven wheel support shaft 23. A crawler belt 25 is wound between the driving wheel 22 and the driven wheel 24. A rolling wheel 26 is attached to the middle part of the traveling frame 20, and the middle part of the crawler belt 25 is supported by the rolling wheel 26. The right traveling unit 10 is configured in the same manner as the left traveling unit 10, and a right traveling hydraulic motor MR is provided at the front end of the traveling frame 20.

As shown in FIGS. 3 and 4, the operation unit 17 includes a support case 30 at the center of the floor 16, and a reversing case 31 is mounted on the support case 30 so as to be reversible on a horizontal plane. . A driver seat 41 is mounted on the reversing case 31. And the driver's seat 41 can be arranged toward either the front or the rear by inverting the reversing case 31 so that the operator can sit on the driver's seat 41 in the traveling direction. First and

second accelerator pedals

90 and 91 are disposed on the right front portion and the left rear portion of the floor portion 16, respectively. Then, when the operator seated in the driver's seat 41 depresses one of the first and

second accelerator pedals

90 and 91 with the right foot, the rotation speed of the engine E, that is, the speed of the airframe is adjusted. That is, the first and

second accelerator pedals

90 and 91 are operating tools for adjusting the speed of the aircraft.

A left operation case 45 is provided on the left side of the reversing case 31, and a travel lever 47 as a travel operation tool is projected from the upper end of the left operation case 45 toward the front upper side. The travel lever 47 can be tilted in the front-rear and left-right directions, and can be traveled in the tilt direction. Here, the tilting operation of the travel lever 47 is prioritized over the depressing operation of either the first or

second accelerator pedal

90 or 91 described above. That is, even if one of the first and

second accelerator pedals

90 and 91 is depressed, the speed is not adjusted unless the traveling lever 47 is tilted. When the traveling lever 47 is in the neutral position, the traveling of the aircraft is stopped. Further, the traveling lever 47 is automatically returned to the neutral state when the operator who has performed the tilting operation releases the traveling lever 47.

A motor capacity selection switch Sw as a motor capacity selection operation section is provided at the front upper end of the travel lever 47. The motor capacity selection switch Sw is selectable with the fingertip of the left hand that holds the travel lever 47. The position of the motor capacity selection switch Sw in the travel lever 47 is not limited to the present embodiment, and any position that can be operated by the finger of the hand holding the travel lever 47, for example, travel. It may be a side surface portion of the lever 47 for use. In this embodiment, by repeatedly pressing the motor capacity selection switch Sw with the fingertip, the first speed range (for example, 0 to 5.6 m / s) that is the speed adjustment range and the second speed range (for example, 5.7 to 5.7) 12 m / s). The motor capacity selection switch Sw is sequentially set to a stage in which the motor capacity of the left and right traveling hydraulic motors ML and MR is in the first speed range via a control unit C and a motor capacity selection switching valve 66 as a motor capacity selection unit which will be described later. It is configured to repeatedly switch between a (low speed stage) and a second speed range stage (high speed stage), and the motor capacity of either the first speed range stage or the second speed range stage can be selected.

Then, by tilting the travel lever 47, the first and

second accelerator pedals

90, 91 or the first speed range corresponding to the speed adjustment (adjustment of engine rotation) by the accelerator switch 37 described later and 2 The motor capacity can be increased / decreased in any speed adjustment range of the speed range, and the aircraft can be driven at a desired speed. At this time, the speed adjustment in each speed adjustment area of the first and second speed ranges is directly proportional to the tilting operation angle of the traveling lever 47.

A traveling pilot valve 46 (see FIG. 6) is disposed in the upper part of the left operation case 45. As shown in FIG. 6, the traveling pilot valve 46 is fluidly connected to a pilot pump Pp, which will be described later, via a traveling primary pilot pressure passage 50, while left and right

swash plate cylinders

81, 83, which will be described later. The secondary pilot pressure passage 51 for traveling is fluidly connected to the vehicle. In the middle of the primary pilot pressure path 50, a travel cut-off valve 58, which is a two-position switching electromagnetic valve, is provided.

Reference numerals

52a, 52b, and 52c denote first to third drain blocks, and reference numeral 53 denotes a travel return oil passage that fluidly connects the travel pilot valve 46 and the first drain block 52a. A traveling switching valve 48 is interposed in the middle of the secondary pilot pressure path 51. The travel switching valve 48 is provided on the floor 16. The traveling switching valve 48 is switched in conjunction with the reversing operation of the reversing case 31 so that the left and right oil passages are switched.

The traveling pilot valve 46 is linked to the base end portion (lower end portion) of a traveling lever 47 that travels the traveling

portions

10 and 10. On the lower front portion of the left operation case 45, a left-side cutoff / release lever 43 that shuts off / releases a hydraulic circuit K (see FIG. 6), which will be described later, protrudes forward and upward. A lever boot 49 is provided on the upper side of the left operation case 45.

In the middle of the upper surface of the left operation case 45, the left armrest 44 is erected so as to be positioned behind the travel lever 47. The left armrest 44 places the elbow side of the forearm of the operator seated on the driver's seat 41 on the left armrest 44 and holds the traveling lever 47 by manually grasping the upper end grip portion of the traveling lever 47. Tilt operation is possible in the front-rear and left-right directions. Then, the traveling pilot valve 46 is switched and operated by tilting the traveling lever 47 in the front-rear and left-right directions.

More specifically, when the traveling lever 47 is in the neutral position (the position where the tilting operation is not performed), the left and right traveling hydraulic motors ML and MR are stopped. When the hand is released from the traveling lever 47, the traveling lever 47 is held in the neutral position, and the aircraft is stopped.

By tilting the traveling lever 47 in the forward (rear) direction, the left and right traveling hydraulic motors ML and MR are driven to rotate forward (reverse), and the aircraft travels straight in the forward (rear) direction (FIG. 1). Then, it can be run in the left (right) direction.

By tilting the traveling lever 47 forward in the right (left) side, the left (right) traveling hydraulic motor ML (MR) is driven to rotate forward, while the right (left) traveling hydraulic motor MR ( ML) is stopped, and the aircraft can be turned forward (pivot turn) to the right side (left side).

The right (left) side traveling hydraulic motor ML (MR) is driven in reverse by tilting the traveling lever 47 to the right (left) side rearward direction, while the left (right) side traveling hydraulic motor MR (ML) ) Is stopped and the aircraft can be turned backward (pivot turn) to the right side (left side).

By tilting the travel lever 47 in the right (left) direction, the left (right) travel hydraulic motor ML (MR) is driven to rotate forward, and the right (left) travel hydraulic motor MR (ML) is driven. By driving in reverse, the aircraft can be turned rapidly (spin turn) rightward (leftward) on the spot.

A right operation case 55 is provided on the right side of the reversing case 31, and a dump lever 57 is projected from the upper end of the right operation case 55 toward the front upper side. A dump pilot valve 56 (see FIG. 6) is disposed in the upper part of the right operation case 55. As shown in FIG. 6, the dump pilot valve 56 is fluidly connected to the pilot pump Pp via the dump primary pilot pressure path 72. In the middle of the primary pilot pressure path 72, a cargo bed cut-off valve 75, which is a two-position switching type electromagnetic valve, is provided. The dump pilot valve 56 is fluidly connected to the dump switching valve 71 via the dump secondary pilot pressure path 73. The dump pilot valve 56 is fluidly connected to the first drain block 52a via the dump pressure oil return oil passage 74.

In the middle of the upper surface of the right operation case 55, the right armrest 54 is erected so as to be positioned behind the dump lever 57. The right armrest 54 places the elbow side of the forearm of the operator seated on the driver's seat 41 on the right armrest 54 and holds the dump lever 57 by holding the upper end grip portion of the dump lever 57 by hand. Tilt operation in the front-rear direction is possible. Then, the dumping switching valve 71 is switched by way of the dumping pilot valve 56 by tilting the dumping lever 57 in the front-rear direction.

With this configuration, the driver's seat 41 and the left and

right operation cases

45 and 55 are disposed so as to be able to be reversed on a virtual horizontal plane through the reversing case 31. An operator seated in the driver's seat 41 holds the traveling lever 47 protruding from the left operation case 45 with the left hand, while holding the dump lever 57 protruding from the right operation case 55 with the right hand. , 57 can be appropriately operated.

The prime mover 18 is provided with an engine E, a pump group 60 and the like (see FIG. 6) on the right side of the overhanging machine frame 15, and these are covered with a bonnet 33. An operation panel unit 35 is placed inside the ceiling of the bonnet 33. The operation panel 35 is provided with a parking brake switch 36, a volume type accelerator switch 37, and the like.

As shown in FIGS. 5 and 6, the pump group 60 includes a left traveling hydraulic pump PL, a right traveling hydraulic pump PR, a pilot pump Pp, and a dump pump Pd connected in series to the drive shaft 39 of the engine E. It is linked to.

The left traveling hydraulic pump ML is fluidly connected to the left traveling hydraulic pump PL via the left traveling hydraulic passage 61 so that the left hydrostatic continuously variable transmission (separated left HST: HydroHStatic Transmission) TL is configured. Further, a right traveling hydraulic motor MR is fluidly connected to the right traveling hydraulic pump PR via a right traveling hydraulic passage 62, and a right hydrostatic continuously variable transmission (separated type right HST) TR is provided. It is composed. The left and right hydrostatic continuously variable transmissions TL and TR are connected to the driving

wheels

22 and 22 of the left and right traveling

units

10 and 10, respectively, so that the left and right hydrostatic continuously variable transmissions TL and TR are connected. The traveling

units

10 and 10 can be steplessly shifted by TR.

Here, the left and right traveling hydraulic pumps PL and PR are of a variable displacement type in which the discharge capacity is changed according to the operation amount (operation angle) of the traveling lever 47. The left and right traveling hydraulic motors ML, MR are variable displacement types that can be switched to a motor capacity of a plurality of stages (in this embodiment, two stages of a first speed range and a second speed range). The motors ML and MR are respectively provided with left and right

capacity change valves

63 and 64 which are pilot-actuated two-position switching valves. The left and right

capacity change valves

63 and 64 are capacity change pressure passages. It is fluidly connected to the pilot pump Pp via 65.

Reference numerals

65L and 65R denote left and right branch pressure passages formed on the downstream side of the capacity changing pressure passage 65, respectively. A motor capacity selection switching valve 66 that is a two-position switching type electromagnetic valve is provided in the middle of the capacity changing pressure path 65. The motor capacity selection switching valve 66 is electrically connected to the output side of the control unit C, which will be described later, while the motor capacity selection switch Sw is electrically connected to the input side of the control unit C as described above.

The dump pump Pd is fluidly connected to the dump cylinder 14 via a dump hydraulic path 70 as shown in FIG. A dump switching valve 71 which is a three-position switching valve is provided in the middle of the dump hydraulic path 70. The dump switching valve 71 is fluidly connected to the dump pilot valve 56 via the dump secondary pilot pressure path 73. The dump pilot valve 56 is fluidly connected to the pilot pump Pp via the primary pilot pressure passage 72 for dump. A base end portion (lower end portion) of a dump lever 57 for extending and retracting the dump cylinder 14 is interlocked and connected to the dump pilot valve 56.

The parking brake switch 36 disposed on the operation panel 35 is a switch for operating the left and right parking brakes BL and BR (see FIG. 6) for braking the left and right traveling hydraulic motors ML and MR. The left and right parking brakes BL, BR are fluidly connected to the pilot pump Pp via a brake pressure path 68 as shown in FIG. In the middle of the brake pressure path 68, a brake cutoff valve 38, which is a two-position switching type electromagnetic valve, is provided. As shown in FIG. 7, the brake cutoff valve 38 is electrically connected to the output side of the control unit C, while the parking brake switch 36 is electrically connected to the input side of the control unit C.

When the parking brake switch 36 is turned ON, the brake cut-off valve 38 is cut off via the control unit C, and the friction plates provided on the left and right parking brakes BL and BR are moved to the left and right traveling hydraulic motor ML. The brake is braked by being pressed against a friction plate provided on the MR side. When the parking brake switch 36 is turned OFF, the brake cut-off valve 38 is connected and operated via the control unit C, and the friction plates provided on the left and right parking brakes BL and BR are moved to the left and right traveling hydraulic motor ML. , Brake braking is released by being separated from the friction plate provided on the MR side.

The accelerator switch 37 disposed on the operation panel unit 35 is used to adjust the rotation speed of the engine E, that is, to adjust the speed of the aircraft, by manually adjusting the rotation beforehand in advance of traveling the aircraft. This is an adjustment switch.

The hydraulic circuit K shown in FIG. 6 includes a traveling primary pilot pressure path 50, a traveling secondary pilot pressure path 51 including left and right traveling

pilot pressure paths

51L and 51R, and a traveling pressure oil return oil path. 53, left traveling hydraulic path 61, right traveling hydraulic path 62, capacity changing pressure path 65, left / right branching

pressure paths

65L and 65R, brake pressure path 68, dumping primary pilot pressure path 72, dumping Secondary side pilot pressure path 73, dumping pressure oil return oil path 74, hydraulic tank T, and the like.

The left traveling pilot pressure path 51L connects the traveling pilot valve 46 and a double-acting left swash plate cylinder 81 that controls forward rotation of the left pump swash plate 80 of the variable displacement left traveling hydraulic pump PL. is doing. The right traveling pilot pressure path 51R connects the traveling pilot valve 46 and a double-acting right swash plate cylinder 83 that controls forward rotation of the right pump swash plate 82 of the variable displacement right traveling hydraulic pump PR. is doing. In the middle of the left and right traveling

pilot pressure paths

51L and 51R, a traveling switching valve 48, which is a two-position switching solenoid valve, is provided, and the traveling switching valve 48 causes the left and right traveling pilot pressure paths 51L. , 51R can be switched to each other downstream.

A pilot pressure sensor S serving as an operation detecting unit that detects the operation of the travel lever 47 is provided in a portion of the travel secondary pilot pressure path 51 located between the travel pilot valve 46 and the travel switching valve 48. Is provided. The pilot pressure sensor S is a sensor that extracts and detects the pilot pressure output from the forward or reverse side of the traveling pilot valve 46 from the traveling secondary pilot pressure path 51. The pilot pressure sensor S is electrically connected to the input side of the control unit C as shown in FIG. When the detection information of the pilot pressure sensor S is transmitted to the control unit C, the control unit C transmits a control signal to the motor capacity selection switching valve 66 based on the detection information, and the motor capacity selection switching valve 66 is set. Switching control is performed.

More specifically, when the pilot pressure sensor S detects the pilot pressure, the first stage (low speed stage) or the second stage (high speed stage) of the motor capacity selection switching valve 66 by the motor capacity selection switch Sw. ), But if the pilot pressure sensor S does not detect the pilot pressure, the left / right traveling hydraulic pressure has priority over the switching state (selection result) of the motor capacity selection switching valve 66. The motor capacities of the motors ML and MR are forcibly set to a large capacity (first speed range) stage (low speed stage). That is, when the traveling lever 47 is in a neutral state and is not tilted, the motor capacity selection switching valve 66 is in either the first speed range (low speed level) or the second speed range (high speed level). Also, it is forcibly held (fixed) in the first speed range (low speed stage).

The pilot pressure sensor S detects the tilting operation of the travel lever 47 when a small capacity (second speed range) stage (high speed stage) is selected by the motor capacity selection switching valve 66 via the motor capacity selection switch Sw. When the current state is not detected, the motor capacity is gradually shifted down from the small capacity (second speed range) stage (high speed stage) to the large capacity (first speed range) stage (low speed stage). However, the aircraft is stopped. That is, when the travel lever 47 set to the motor capacity in the second speed range (high speed stage) is tilted, the motor capacity is 2 when the travel lever 47 is operated or returned to the neutral position. While changing from the speed range (high speed stage) to the 1st speed range (low speed stage), the aircraft is stopped.

The pilot pressure sensor S detects the tilting operation of the travel lever 47 when a small capacity (second speed range) stage (high speed stage) is selected by the motor capacity selection switching valve 66 via the motor capacity selection switch Sw. When the detected state is changed from the non-operating state, the motor capacity is gradually shifted from the large capacity (first speed range) stage (low speed stage) to the small capacity (second speed range) stage (high speed stage). The speed is increased while being up. That is, when the travel lever 47 set to the motor capacity of the second speed range (high speed stage) is being tilted, once the travel lever 47 is operated or returned to the neutral position, the motor capacity Is forcibly shifted down (changed) to the first speed range (low speed), and then the drive lever 47 is tilted, the motor capacity is automatically set to the second speed range (high speed). Shifted up and restored.

In the construction machine A configured as described above, for example, when the traveling lever 47 is operated or returned to a neutral state on an uphill slope, the motor capacity stops at the first speed range (low speed). Are forcibly held (fixed). Therefore, even if the aircraft descends along the slope due to leakage of the hydraulic pressure of the left and right traveling hydraulic pumps PL and PR and the left and right traveling hydraulic motors ML and MR, the first speed range where the motor capacity is the low speed stage. The lowering amount of the fuselage is suppressed. Therefore, it is possible to avoid an unexpected situation.

At this time, when the travel lever 47 set to the motor capacity of the second speed range (high speed stage) is tilted, the motor capacity is reduced when the travel lever 47 is operated or returned to the neutral position. Since the aircraft stops traveling while changing from the second speed range (high speed) to the first speed range (low speed), the aircraft is smoothly stopped.

Further, when the travel lever 47 set to the motor capacity of the second speed range (high speed stage) is being tilted, once the travel lever 47 is operated or returned to the neutral position, the motor capacity Is forcibly shifted down (changed) to the first speed range (low speed), and then the drive lever 47 is tilted, the motor capacity is shifted up to the second speed range (high speed). Therefore, the aircraft can be smoothly driven at a higher speed, and the operability can be improved.

The left and right traveling hydraulic motors ML and MR change the inclination angle of the left and right motor swash plates 84 and 85 according to the low speed side piston and the high speed side piston so that the motor capacity is increased to a large capacity and a small capacity. Change. When the motor capacity is large, the motor rotational speed decreases and the traveling speed becomes low. When the motor capacity is small, the motor rotational speed increases and the traveling speed becomes high. The low-speed and high-speed pistons are expanded and contracted so as to change the inclination angles of the left and right motor swash plates 84 and 85 by the pressure oil supplied via the capacity changing pressure passage 65. The left and right motor swash plates 84 and 85 are fluidly connected to the capacity changing pressure passage 65 via the left and right

capacity changing valves

63 and 64.

When the motor capacity selection switching valve 66 provided in the middle of the capacity changing pressure passage 65 is selected (switched) by the motor capacity selection switch Sw, the left / right

capacity changing valves

63 and 64 are moved to the first speed range. The stage can be switched to one of the second stage (low speed stage) and the second speed range stage (high speed stage).

The control unit C is configured using a personal computer or the like. As shown in FIG. 7, a pilot pressure sensor S, a motor capacity selection switch Sw, a parking brake switch 36, and an accelerator switch 37 are electrically connected to the input side of the control unit C. On the output side of the control unit C, the following motor capacity selection switching valve 66, which is an electromagnetic valve, a brake cutoff valve 38, a traveling cutoff valve 58, a cargo bed cutoff valve 75, and a traveling switching valve 48 are provided. And are electrically connected.

The control unit C has a built-in control program, and the control program is a program for controlling the solenoid valve by transmitting control information to the solenoid valve based on input information from the sensor, switch, or the like. Has been.

FIG. 8 is a flowchart of the control program. As shown in FIG. 8, when the pilot pressure sensor S detects the neutral state of the traveling lever 47 (S100 YES) and the motor capacity is selected to the first speed range (S110 YES), that is, the motor capacity selection switch When the motor capacity selection switching valve 66 is switched to the first speed range by Sw, the motor capacity selection switching valve 66 is fixed to the first speed range by the control unit C (S120).

The pilot pressure sensor S does not detect the neutral state of the travel lever 47 (S100 NO), detects the tilted state of the travel lever 47 (S130 YES), and the motor capacity is selected to the second speed range ( S140 YES), that is, when the motor capacity selection switch valve 66 is switched to the second speed range by the motor capacity selection switch Sw, the controller C determines whether the travel lever 47 is in a neutral state or in a tilted state. Judgment is made (S150). At this time, when the pilot pressure sensor S detects the neutral state of the traveling lever 47 (YES in S150), the motor capacity selection switching valve 66 is forcibly shifted down to the first speed range by the control unit C ( S160). Thereafter, when the pilot pressure sensor S detects the tilted state of the travel lever 47 (S170 YES), the motor capacity selection switching valve 66 is forcibly shifted up to the second speed range by the control unit C (S180).

When the motor capacity is not selected for the first speed range (S110 NO), it is determined whether the motor capacity is selected for the second speed range (S140). When the pilot pressure sensor S does not detect the tilting state of the traveling lever 47 (S170 NO), it is determined whether the traveling lever 47 is in the standing state or the tilting state (S150).

Thus, when the traveling lever 47 is in the neutral state, the control unit C performs control so that the motor capacity is fixed to the first speed range.

A Construction machine C Control unit E Engine ML Left-side traveling hydraulic motor MR Right-side traveling hydraulic motor PL Left-side traveling hydraulic pump PM Right-side traveling hydraulic pump S Pilot pressure sensor (operation detection unit)
Sw Motor capacity selection switch (Motor capacity selection operation section)
47 Travel lever (travel control tool)
66 Motor capacity selection switching valve (Motor capacity selection part)

Claims

A variable displacement travel hydraulic pump whose discharge capacity is changed in response to the operation of the travel operation tool, and a variable displacement type fluidly connected to the travel hydraulic pump and capable of switching to a plurality of stages of motor capacity. A travel hydraulic motor, a motor capacity selection unit that selects a motor capacity of a plurality of stages of the travel hydraulic motor, a motor capacity selection operation unit that operates the motor capacity selection unit, and an operation of the travel operation tool is detected An operation detection unit, and a control unit that connects the operation detection unit and the motor capacity selection operation unit to the input side, and connects the motor capacity selection unit to the output side,
When the operation detection unit does not detect the operation of the travel operation tool, the motor capacity of the traveling hydraulic motor is set to a large capacity stage in preference to the selection result of the motor capacity selection unit. And construction machinery.
When a small capacity stage is selected by the motor capacity selection unit via the motor capacity selection operation unit, the operation detection unit is not detected from the state in which the operation of the travel operation tool is detected. 2. The construction machine according to claim 1, wherein the traveling is stopped while the motor capacity is gradually shifted down from a small capacity stage to a large capacity stage.
When a small capacity stage is selected by the motor capacity selection unit via the motor capacity selection operation unit, the operation detection unit is in a state of detecting from a state in which the operation of the travel operation tool is not detected. 2. The construction machine according to claim 1, wherein the motor capacity is increased while being gradually shifted up from a large capacity stage to a small capacity stage.
The construction according to any one of claims 1 to 3, wherein the motor capacity selection operation unit is provided in the travel operation tool and is selectable by a fingertip of a hand holding the travel operation tool. machine.