JP2008082127A - Backhoe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backhoe in which matching during a predetermined concurrent operation such an operation that a swing table is swung while swingingly operating a boom or an arm is improved. <P>SOLUTION: This backhoe comprises the swing table 10 mounted to a traveling body 2 swingingly around the vertical axis. A ground working device 11 having a swingable boom 17 and a swingable arm 18 is attached to the front of the swing table 10. A swing motor 13 for swinging the swing table 10 is formed to be shifted to two high and low speeds. Normally, the swing motor 13 is used in the high speed. When the boom 17 or the arm 18 is swingingly operated, the swing motor 13 is automatically shifted to the low speed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a backhoe in which a turntable equipped with a ground work device is mounted on a traveling body so as to be turnable around an axis in the vertical direction.

Conventionally, as a working machine for excavation work, etc., a swivel is mounted on a traveling body so as to be able to swivel around a vertical axis, and a boom, an arm and a bucket are sequentially connected to the front of the swivel. There is a backhoe equipped with a ground work device (see Patent Document 1).
JP 2006-161510 A

In the backhoe, the boom, arm and the like are swung by a boom cylinder and arm cylinder made of a hydraulic cylinder, and the swivel is swung by a turning motor made of a hydraulic motor. These boom cylinder, arm cylinder and swivel motor Is operated by tilting the operating lever, and the drive speed of the boom cylinder, arm cylinder or swing motor can be changed by the tilting amount of the operating lever (the larger the amount of tilting the operating lever, the larger the boom cylinder, Arm cylinder or swivel motor moves fast).
However, in practice, it is often used in a state (maximum speed) in which the operation lever is tilted to the maximum in terms of work efficiency.

And, for example, when digging up the ground with a bucket and crushing the soil, and placing the soil on the truck bed, the swivel is swiveled while raising the boom, but the swivel speed is Since it is set with emphasis on mobility when turning without work, it turns to the target position before the boom is raised to the target position because the turning speed is too fast for the boom raising operation. There is a problem that the platform turns and the boom raising operation and the turning operation do not match.
Since the swing speed of the boom and the swing speed of the swivel can be changed by tilting the operation lever, the amount of tilt of the operation lever may be adjusted so that the boom raising operation and the swing operation match. In that case, a delicate manual operation by the operator is required, which is troublesome.

In addition, there is a similar problem when the swivel is swung while the arm is operated in the cloud (sticking operation). In addition, when the boom lowering operation and turning, and the arm dumping operation and turning do not match these simultaneous operations. Can be considered.
In view of the above problems, an object of the present invention is to provide a backhoe with improved matching at the time of a predetermined simultaneous operation such as turning a swivel while swinging a boom or an arm.

The technical means taken by the present invention in order to solve the technical problem includes a swivel mounted on a traveling body so as to be able to swivel about an axis in the vertical direction, and a swinging unit is provided at a front portion of the swivel. In a backhoe equipped with a ground work device with a movable boom and arm,
The swivel motor that turns the swivel base is configured to be capable of shifting to high and low speeds. Normally, the swivel motor is used in a high speed state, and the swivel motor is automatically switched to a low speed state when the boom or arm is swung. It is configured as described above.
The swing motor is constituted by a swash plate type variable displacement hydraulic motor, and is switched between a high speed state and a low speed state by switching the swash plate via a swash plate switching actuator, and an actuator control for controlling the swash plate switching actuator. This actuator control valve is switchable between a high speed position for switching the swing motor to a high speed state and a low speed position for switching the swing motor to a low speed state. When the boom or arm is swung, the pilot pressure from the command circuit may be drained to switch to the low speed position.

The control circuit is configured to be switchable between a supply position for sending pilot pressure to the command circuit and a non-supply position for draining pressure oil in the command circuit, and when the boom or arm is swung, the non-supply position is set. A swivel reduction valve configured to be switched may be provided.
The actuator control valve is automatically switched from the high speed position to the low speed position by detecting the pressure of the motor drive circuit that drives the swing motor when the load acting on the swing motor exceeds a predetermined value. Is good.

  According to the present invention, the matching of these operations when the boom or arm and the swivel are operated simultaneously is improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, reference numeral 1 denotes a backhoe. The backhoe 1 is mainly composed of a lower traveling body 2 and an upper revolving body 3 that is mounted on the traveling body 2 so as to be able to swivel around a vertical pivot axis. It is configured.
The traveling body 2 includes a crawler type traveling device 7 configured to circulate around the crawler belt 6 by a traveling motor 5 including a hydraulic motor on both the left and right sides of the track frame 4.

A dozer device 8 is provided at the front portion of the track frame 4, and the blades of the dozer device are moved up and down by expansion and contraction of a dozer cylinder 9 comprising a hydraulic cylinder.
The swivel body 3 includes a swivel base 10 that is mounted on the track frame 4 so as to be rotatable about a swivel axis, a ground work device (excavation work device) 11 that is provided at the front of the swivel base 10, and a swivel base. And a cabin 12 mounted on the vehicle 10.
The swivel base 10 is provided with an engine, a radiator, a fuel tank, a hydraulic oil tank, a battery, and the like. The swivel base 10 is swiveled by a swivel motor 13 composed of a hydraulic motor.

In addition, a swing bracket 15 is provided at the front of the swivel base 10 and is supported on a support bracket 14 provided so as to protrude forward from the swivel base 10 so as to be swingable left and right around the vertical axis. The swing bracket 15 is swung left and right by expansion and contraction of a swing cylinder 16 formed of a hydraulic cylinder.
The ground work device 11 includes a boom 17 whose base side is pivotally connected to the upper portion of the swing bracket 15 so as to be rotatable about a left and right axis, and can swing up and down. The arm 18 is pivotally connected to the arm 18 so as to be swingable back and forth, and the bucket 19 is pivotally connected to the front end side of the arm 18 so as to be pivotable around the left and right axes. And is composed mainly of.

The boom 17 moves up by extending the boom cylinder 21 interposed between the boom 17 and the swing bracket 15 and moves down by contracting the boom cylinder 21.
The arm 18 swings backward by extending the arm cylinder 22 interposed between the arm 18 and the boom 17 to perform a cloud operation (scratching operation), and contracts the arm cylinder 22. Oscillates forward and dumps.
The bucket 19 swings backward by extending the bucket cylinder 23 interposed between the bucket 19 and the arm 18 to perform a cloud operation (crawl operation), and contracts the bucket cylinder 23. Dumps by swinging forward.

The boom cylinder 21, the arm cylinder 22 and the bucket cylinder 23 are each constituted by a hydraulic cylinder.
Next, a hydraulic system for operating various hydraulic actuators installed in the backhoe 1 will be described with reference to FIGS.
In FIG. 2, V1 is a swing control valve that controls the swing motor 13, V2 is a dozer control valve that controls the dozer cylinder 9, V3 is a swing control valve that controls the swing cylinder 16, and V4 is the left travel motor 5. V5 is a right-side travel control valve that controls the right-side travel motor 5, V6 is an arm control valve that controls the arm cylinder 22, and V7 is a bucket control valve that controls the bucket cylinder 23. , V8 is a boom control valve for controlling the boom cylinder 21, and V9 is an SP control valve for controlling a hydraulic attachment such as a hydraulic breaker separately attached to the ground work device 11.

These control valves V1 to 9 are constituted by direct acting spool type switching valves, and are also constituted by pilot operation switching valves that are switched by pilot pressure, and each control valve V1 to 9 is a control valve. It is configured to be moved in proportion to the operation amount of each operation means for operating V1 to V9, and to supply to the hydraulic actuator to be controlled an amount of pressure oil proportional to the amount by which each control valve V1 to 9 is moved. The operation speed of the operation target can be changed in proportion to the operation amount of each operation means.
The left travel control valve V4 is switched by a left travel pilot valve PV1 operated by a left travel lever 24, and the right travel control valve V5 is operated by a right travel pilot valve PV2 operated by a right travel lever 25. The switching levers 24 and 25 and the pilot valves PV1 and PV2 are arranged on the front side of the driver's seat in the cabin 12.

The left and right traveling levers 24, 25 are provided so as to be tiltable back and forth, and when the left and right traveling levers 24, 25 are tilted forward, the traveling motor 5 is driven so that the corresponding traveling device 7 is driven forward, The left and right traveling control valves V4 and V5 are operated so that the traveling motor 5 is driven so that the corresponding traveling device 7 is driven backward when the traveling levers 24 and 25 are tilted rearward.
The turning control valve V1 and the arm control valve V6 are switched by a steering pilot valve PV3 operated by one steering lever 26, and the steering lever 26 is arranged on the left side of the driver's seat.

Further, the bucket control valve V7 and the boom control valve V8 are also switched by the pilot pilot valve PV4 operated by one control lever 27, and the control lever 27 is arranged on the right side of the driver's seat. .
The left and right control levers 26 and 27 are provided so as to be tiltable forward and backward and left and right, respectively. In this embodiment, when the left control lever 26 is tilted left and right, the swivel base 10 pivots left and right, and when tilted back and forth, the arm 18 The corresponding control valves V1 and V6 are operated such that the bucket 19 performs the dump / cloud operation. When the right control lever 27 is tilted left and right, the bucket 19 performs the cloud dump operation, and when it is tilted forward and backward, the boom 17 is lowered and raised. Thus, the corresponding control valves V7 and V8 are operated.

The dozer control valve V2, the swing control valve V3, and the SP control valve V9 are each operated by a pilot valve that is operated by operating means (not shown).
A pump as a pressure oil supply source in this hydraulic system includes a first pump P1, a second pump P2, a third pump P3, and a fourth pump P4. These pumps P1, P2, P3, P4 are It is driven by an engine E mounted on the swivel base 10.
The first pump P1 and the second pump P2 are swash plate type variable displacement axial pumps, and are integrally formed by an equal flow double pump that can obtain an equal discharge amount from two discharge ports, and these first pumps P1. The second pump P2 is mainly used for the traveling motor 5 and the hydraulic cylinder of the ground work device 11.

The third pump P3 and the fourth pump P4 are constituted by constant displacement gear pumps. The third pump P3 is mainly used for the swing motor 13, the dozer cylinder 9 and the swing cylinder 16, and the fourth pump P4 is supplied with pilot pressure. Used for.
The first pump P1 and the second pump P2 may be formed separately.
In this hydraulic system, the discharge amount of the first and second pumps P1, P2 is controlled according to the work load pressure of the boom 17, the arm 18, the bucket 19, etc., and the hydraulic power required for the load is reduced. 1, a load sensing system that can save power and improve operability by discharging from the pumps P1 and P2 is adopted. The load sensing system includes an arm control valve V6, a bucket control valve V7, An after orifice type in which a pressure compensation valve CV is connected after the main spools of the boom control valve V8 and the SP control valve V9 is employed.

The control system circuit of this load sensing system is not shown.
In the figure, V10 is an unload valve in the load sensing system, and V11 is a system relief valve in the load sensing system.
Each section of running, turning, dozer, and swing is configured by an open circuit.
In this hydraulic system, when not running, the pressure oil from the first pump P1 and the second pump P2 is merged to control the boom 17, the arm 18, the bucket 19, and the SP control valves V8, V6, V7. , V9 can be supplied, and during traveling, the pressure oil from the first pump P1 and the second pump P2 is independently supplied to the control valves V4, V5 for the left and right traveling devices 7, and the third pump P3 Can be supplied to the boom 17, the arm 18, the bucket 19, and the control valves V8, V6, V7, and V9 for SP.

A hydraulic circuit configuration for performing this operation will be described with reference to FIGS.
To the discharge circuits 28 and 29 of the first pump P1 and the second pump P2, a traveling self-operating valve V12 constituted by a direct acting spool type pilot operation switching valve is connected.
The running valve V12 joins the discharge circuit 28 of the first pump P1 and the discharge circuit 29 of the second pump P2 to control the boom 17, the arm 18, the bucket 19, and the control valves V8, V6, V7, SP. A merging position 31 to be connected to the working system supply circuit 30 for supplying pressure oil to V9, and a discharge circuit 29 of the first pump P1 to a traveling right supply circuit 32 for supplying pressure oil to the right traveling control valve V5; The discharge circuit 29 of the second pump P2 can be switched to an independent supply position 34 that is connected to a traveling left supply circuit 33 that supplies pressure oil to the left traveling control valve V4, and is switched to a merging position 31 by a spring. It is switched to the independent supply position 34 by the pilot pressure standing in the German switching circuit 35.

The discharge circuit 36 of the third pump P3 is connected with a pressure oil supply passage 37 for supplying pressure oil to the control valves V1, V2, and V3 for turning, dozer, and swing. Are sequentially passed through the turning control valve V1, the dozer control valve V2, and the swing control valve V3, and are connected to the flow path switching valve V13.
Further, a connection circuit 38 is connected to the upstream side of the flow path switching valve V13 and the downstream side of the swing control valve V3 of the discharge circuit 36 of the third pump P3, and this connection circuit 38 is connected to the working system supply circuit 30. The discharge circuit 36 of the third pump P3 and the work system supply circuit 30 are connected by a connection circuit 38. The connection circuit 38 is connected to the discharge circuit side of the third pump P3 from the work system supply circuit 30 side. A check valve V14 for blocking the flow of pressure oil is interposed.

  The flow path switching valve V13 is composed of a direct-acting spool type pilot operation switching valve. By connecting the discharge circuit 36 of the third pump P3 to the drain circuit d, the pressure oil from the third pump P3 is supplied. A non-supply position 39 that does not supply the work system supply circuit 30 (the boom 17, the arm 18, the bucket 19, and the SP control valves V8, V6, V7, and V9), the discharge circuit 36 and the drain circuit d of the third pump P3. Is disconnected from the third pump P3 to the supply position 40 for supplying the working oil supply circuit 30 via the connection circuit 38, and is switched to the non-supply position 39 by a spring. The supply position 40 is switched by the pilot pressure standing in the flow path switching circuit 41.

The pressure oil discharged from the fourth pump P4 is diverted by the first to third discharge circuits 42, 43, and 44. The first discharge circuit 42 is connected to the unload valve V15, and the second discharge circuit. 43 is connected to the traveling second speed switching valve V16, and the third discharge circuit 44 is branched into a valve operation detection circuit 45, a first pilot pressure supply circuit 46, and a second pilot pressure supply circuit 47.
The unloading valve V15 is constituted by an electromagnetic valve, and the pressure oil from the first discharge circuit 42 is supplied to the left and right traveling pilot valves PV1 and PV2, the left and right piloting pilot valves PV3 and PV4, and the dozer control valve V2. A pilot valve (not shown) for operating the pilot valve (not shown) for operating the swing control valve V3, a supply position 48 for supplying the pilot valve (not shown) for operating the SP control valve V9, and the first By draining the pressure oil from the discharge circuit 42, it is possible to switch to the non-supply position 49 that does not supply pressure oil to these pilot valves, and is switched to the non-supply position 49 by a spring and supplied by an excitation signal. 48.

The excitation / demagnetization signal for the unload valve V15 is transmitted by raising / lowering a lock lever disposed on the side of the driver's seat, and demagnetizing the unload valve V15 by lifting the lock lever when getting off the backhoe 1. A signal is transmitted and the unload valve V15 is switched to the non-supply position 49, and after getting on the backhoe 1, an excitation signal is transmitted by depressing the lock lever and the unload valve V15 is switched to the supply position 48.
The traveling second speed switching valve V16 will be described later.

  The valve operation detection circuit 45 includes a throttle 50, a turning control valve V1, a dozer control valve V2, a swing control valve V3, a left traveling control valve V4, a right traveling control valve V5, an arm control valve V6, and a bucket. It is connected to the drain circuit d through the control valve V7 → the boom control valve V8 → the SP control valve V9, and a pressure switch is provided between the throttle 50 of the valve operation detection circuit 45 and the turning control valve V1. When an AI switch 51 is connected and any one of the control valves V1 to V9 is operated from the neutral position, a part of the valve operation detection circuit 45 is cut off and pressure is generated in the valve operation detection circuit 45. It is configured to be detected by the AI switch 51.

If the pressure is not detected by the AI switch 51, the rotational speed of the engine E is automatically reduced to idling rotation, and if the pressure is detected by the AI switch 51, the rotational speed of the engine E is automatically increased to a predetermined rotational speed. Thus, the rotational speed of the engine E is automatically controlled.
The first pilot pressure supply circuit 46 is connected to the valve operation circuit 52 and the traveling switch circuit 35, and upstream of the connection point a of the valve operation circuit 52 and the traveling switch circuit 35 of the first pilot pressure supply circuit 46. A diaphragm 53 is interposed.
In addition, a traveling detection circuit 54 is connected to the traveling switch circuit 35, and this traveling detection circuit 54 is connected to the drain circuit d via the left traveling control valve V4 → the right traveling control valve V5.

The second pilot pressure supply circuit 47 is connected to the downstream side of the right travel control valve V5 and the upstream side of the arm control valve V6 of the valve operation detection circuit 45, and the second pilot pressure supply circuit 47 is connected to the upstream side. Thus, a throttle 55 and a check valve 56 for blocking the flow of pressure oil from the valve operation detection circuit 45 side to the throttle 55 side are sequentially provided.
The flow path switching circuit 41 is connected between the throttle 55 and the check valve 56 of the second pilot pressure supply circuit 47, and the flow path switching circuit 41 is constituted by a direct acting spool type pilot operation switching valve. The flow path switching valve V17 is interposed, and the valve operation circuit 52 is connected to the spool end (pilot port) of the flow path switching valve V17.

The flow path switching valve V17 flows through the flow path switching circuit 41 and the non-operation position 58 where the pilot pressure is not supplied to the flow path switching valve V13 by flowing the pressure oil flowing through the flow path switching circuit 41 to the drain circuit d. The pilot pressure can be switched to the operating position 59 for supplying the flow path switching valve V13, and is switched to the non-operating position 58 by a spring, and is switched to the operating position 59 by the pilot pressure standing in the valve operating circuit 52.
In the case of the above configuration, when the left and right traveling control valves V4, V5 are not operated (when the left and right traveling control valves V4, V5 are in the neutral position), the traveling detection circuit 54, the traveling self-switching Since no pressure is generated in the circuit 35 and the valve operation circuit 52, the traveling valve V12 is set to the merging position 31, the flow switching valve V17 is set to the non-operating position 58, and the flow switching valve V13 is set to the non-supply position. The oil discharged from the first pump P1 and the second pump P2 is merged so that pressure oil can be supplied to the control valves V6, V7, V8, and V9 for the arm 18, bucket 19, boom 17, and SP.

  When the control valves V6, V7, V8, and V9 for the arm 18, bucket 19, boom 17, and SP are operated from the neutral position in this state, the connection point b between the valve operation detection circuit 45 and the second pilot pressure supply circuit 47 is determined. The valve operation detection circuit 45 is shut off on the downstream side, and the pressure oil from the second pilot pressure supply circuit 47 flows to the flow path switching circuit 41, but the flow path switching operation valve V17 is in the non-operation position 58. The pressure oil flowing through the flow path switching circuit 41 flows into the drain circuit d, and no pilot pressure is established at the spool end of the flow path switching valve V13, and the flow path switching valve V13 remains at the non-supply position 39. Thus, the pressure oil from the third pump P3 is not supplied to the control valves V6, V7, V8, and V9 for the arm 18, bucket 19, boom 17, and SP.

On the other hand, when the left and right travel control valves V4 and V5 are operated from the neutral position, a part of the travel detection circuit 54 is cut off, and pressure is generated in the travel detection circuit 54, the travel switching circuit 35 and the valve operation circuit 52. The running valve V12 is switched to the independent supply position 34 and the flow path switching valve V17 is switched to the operating position 59.
As a result, the oil discharged from the first pump P1 is supplied to the right travel control valve V5, and the oil discharged from the second pump P2 is supplied to the left travel control valve V4, from the first and second pumps P1 and P2. Is not supplied to the arm 18, the bucket 19, the boom 17, and the control valve for SP.

  At this time, if the arm 18, the bucket 19, the boom 17, and the SP control valves V6, V7, V8, V9 are not operated, even if the flow path switching valve V17 is switched to the operating position 59, the second Since the pressure oil from the pilot pressure supply circuit 47 flows to the drain circuit d through the check valve 56 → the valve operation detection circuit 45, the flow path switching valve V13 is not switched to the supply position 40 (the non-supply position 39 remains unchanged). However, when the arm 18, bucket 19, boom 17, and SP control valves V6, V7, V8, V9 are operated and the valve operation detection circuit 45 is shut off, the flow path switching valve V17 is moved to the operating position 59. Therefore, a pressure is generated in the flow path switching circuit 41, and this pressure switches the flow path switching valve V13 to the supply position 40, so that the pressure oil from the third pump P3 is transferred to the arm 18, Tsu door 19, each control valve V6 of the boom 17, and SP, V7, V8, can be supplied to the V9.

  And the control valve V4 for driving | running | working in the state which is operating the control valve V6, V7, V8, V9 for the arm 18, the bucket 19, the boom 17, SP, for example, raising the control valve V8 for booms. , V5 when one or both of them are operated, while the pressure oil from the second pilot pressure supply circuit 47 is flowing to the flow path switching circuit 41, the traveling valve V12 is moved to the independent supply position 34. At the same time, the flow path switching valve V17 is switched to the operating position 59, and since the flow path switching valve V17 is switched to the operating position 59, the flow path switching valve V13 is switched to the supply position 40. Although the supply of pressure oil from the first and second pumps P1, P2 to the boom control valve V8 is cut off, the pressure oil from the third pump P3 is supplied to the boom control valve V8. Work is continued.

At this time, if the traveling valve V12 switches earlier than the flow path switching valve V17, the supply of pressure oil to the boom control valve V8 is temporarily interrupted, and the movement of the boom 17 is temporarily stopped. In this embodiment, the flow path switching operation valve V17 is switched to the operating position 59 by the same pilot pressure as that of the traveling self-valve V12, or the flow path switching operation valve V17 is lower than the traveling self-valve V12. The switching pressures of the traveling valve V12 and the flow path switching valve V17 are set so as to switch to the operating position 59 by pressure.
As a result, when the travel control valves V4 and V5 are operated while the boom control valve V8 is raised, the operation of the boom 17 is not temporarily interrupted, and the continuity of the boom 17 raising operation is maintained. It is.

When the travel control valves V4 and V5 are operated while the boom control valve V8 is being lowered or the arm 18, bucket 19 and SP control valves V6, V7 and V9 are being operated. Is the same.
Also, in the conventional hydraulic system, when the traveling device is operated while the ground work device is being operated, the traveling valve is switched so that the flow path switching valve is switched simultaneously with the traveling valve or before the traveling valve. When attempting to adjust the switching pressure between the single valve and the flow path switching valve, if the switching pressure of the flow path switching valve is made too low, the control for the traveling device is caused by various factors when the ground work device is operating. There is a possibility that the flow path switching valve is switched to the supply position even when the valve is not operated, and the switching pressure of the flow path switching valve cannot be made too low. Also, if the switching pressure of the running valve is increased more than necessary, there will be a problem in responsiveness, etc.In conventional hydraulic systems, the flow path switching valve is surely used simultaneously with the running valve or more than the running valve. It is difficult to set to switch first, and when the control valve for the traveling device is operated when the ground work device is used, the traveling valve switches before the flow path switching valve. The problem has arisen.

  On the other hand, in the hydraulic system having the above-described configuration, the flow path switching operation valve V17 is switched to the operating position 59 by the pilot pressure of the same pressure as that of the traveling independent valve V12, or the flow path switching operation valve V17 is driven. The switching pressure of the flow path switching operation valve V17 can be easily set so that the operation position 59 is switched at a pilot pressure lower than that of the independent valve V12, and the hydraulic system can be used for traveling while the ground work device 11 is being used. When the control valves V4 and V5 are operated, the flow path switching valve V13 can be easily configured to switch simultaneously with the traveling valve V12 or before the traveling valve V12.

In this hydraulic system, each of the left and right traveling motors 5 is constituted by a swash plate type variable displacement axial motor that can change speed between high and low speeds. For example, the traveling motor 5 is in a second speed state (high speed state). If the driving force is insufficient when the steering operation is performed or the vehicle gets over an obstacle when the vehicle is traveling straight in a small capacity state, the motor capacity is increased to drive the vehicle. In order to increase the force, a traveling automatic deceleration system that automatically decelerates the traveling motor 5 from the second speed state to the first speed state (low speed state, large capacity state) is provided.
This traveling automatic deceleration system will be described with reference to FIGS.

  Each of the left and right traveling motors 5 includes a pair of motor drive circuits that are driven from the traveling control valves V4 and V5 through one of the pair of pressure oil supply circuits 60 and the counter balance valve V18 by tilting the traveling levers 24 and 25 forward and backward. The pressure oil is supplied to one of the 61 and discharged through the other motor drive circuit 61, the counter balance valve V18 and the other pressure oil supply circuit 60, and the traveling levers 24, 25 are moved forward and backward to fall. Pressure oil is supplied from the control valves V4, V5 to the other of the pair of motor drive circuits 61 via the other of the pair of pressure oil supply circuits 60 and the counter balance valve V18, and the one motor drive circuit 61, counter balance valve The oil is discharged through the V18 and one of the pressure oil supply circuits 60, thereby driving forward and reverse.

The traveling motor 5 is switched between a first speed state and a second speed state by changing the angle of the swash plate by a swash plate switching cylinder (swash plate switching actuator) 62. In the illustrated example, the swash plate switching cylinder 62 is switched. When the motor is not operated, the traveling motor 5 is set to the first speed state, and the traveling motor 5 is switched to the second speed state by operating the swash plate switching cylinder 62 (extending the rod).
The swash plate switching cylinder 62 is connected to a cylinder control valve (actuator control valve) V19 via a cylinder operating circuit 63, and the cylinder control valve V19 is selectively connected from the high pressure side of the pair of motor drive circuits 61 by a shuttle valve V20. An operating pressure supply circuit 64 for supplying pressure oil to the cylinder control valve V19 is connected to the cylinder control valve V19, and the swash plate switching cylinder 62 is operated by the pressure oil from the operating pressure supply circuit 64.

The cylinder control valve V19 is constituted by a direct-acting spool type pilot operation switching valve. The cylinder control valve V19 supplies the hydraulic oil from the operating pressure supply circuit 64 to the swash plate switching cylinder 62 via the cylinder operating circuit 63, and the traveling motor 5 is driven at the second speed. The second speed position 66 is set to the first speed position 67, and the cylinder operating circuit 63 is connected to the drain circuit d so that the operating pressure is not supplied to the swash plate switching cylinder 62 so that the traveling motor 5 is set to the first speed state. Switching is possible, switching to the second speed position 66 by the pilot pressure, and switching to the first speed position 67 by the spring.
The pilot port of the cylinder control valve V19 is connected to the output port e of the traveling second speed switching valve V16 via a pilot circuit 68.

The pilot circuit 68 is branched on the way from the traveling second speed switching valve V16 to the cylinder control valve V19 and connected to the pilot port of the cylinder control valve V19 of the left and right traveling motors 5, and is connected to the left and right cylinder control valves V19. At the same time, the pilot pressure is sent.
The traveling second speed switching valve V16 is constituted by a direct acting spool type electromagnetic valve (electromagnetic switching valve).
The second discharge circuit 43 of the fourth pump P4 is connected to the input port f of the traveling second speed switching valve V16. The traveling second speed switching valve V16 is piloted by a spring when the solenoid is demagnetized. The circuit 68 is switched to the first speed position 69 communicating with the drain circuit d, and the solenoid is energized to switch to the second speed position 70 where the discharge oil of the fourth pump P4 is sent to the pilot circuit 68.

When the traveling second speed switching valve V16 is switched to the first speed position 69, the cylinder control valves V19 of the left and right traveling motors 5 are set to the first speed position 67, and the left and right traveling motors 5 are respectively set to the first speed state. When the traveling second speed switching valve V16 is switched to the second speed position 70, the cylinder control valves V19 of the left and right traveling motors 5 are switched to the second speed position 66, the swash plate switching cylinder 62 is operated, and the left and right traveling motors 5 are simultaneously operated. Switch to 2nd speed.
The traveling second speed switching valve V16 is operated by a traveling second speed operation means 71 such as a push button, a pedal, or a lever, and an operation signal from the traveling second speed operation means 71 is input to the control device 72. The second speed switching command signal (excitation signal) or the first speed switching command signal (demagnetization signal) is transmitted from 72 to the traveling second speed switching valve V16.

The discharge circuit 28 of the first pump P1 and the discharge circuit 29 of the second pump P2 are connected to first and second detection means 74 and 75, respectively, which are pressure sensors for detecting the pressure of the circuit. Detection signals from 74 and 75 are input to the control device 72.
Further, the control device 72 is configured to receive a detection signal of third detection means 75 that detects that the travel levers 24 and 25 are operated.
The third detecting means 75 is composed of a pressure sensor, and is connected to a command circuit 76 for sending pilot pressure from the traveling pilot valves PV1, PV2 to the traveling control valves V4, V5 when the traveling levers 24, 25 are operated. 77, and it is detected that one of the left and right traveling levers 24, 25 has been operated either forward or backward (detects that the traveling independent valve V12 has been switched to the independent supply position 34). .

In the configuration described above, the third detection means 75 detects that the travel control valves V4 and V5 are operated, and the load on the travel motor 5 increases, so that the first detection means 73 and / or Alternatively, when the second detecting means 74 detects a pressure equal to or higher than a predetermined pressure, a deceleration signal (demagnetization signal) is transmitted from the control device 72 and the traveling second speed switching valve V16 is moved from the second speed position 70 to the first speed position 69. It is configured to be switched.
That is, the traveling second speed operation means 71 is operated and a second speed switching command signal is transmitted from the control device 72 (the traveling second speed switching valve V16 is excited), and the traveling motor 5 travels in the second speed state. Even when the load is greater than or equal to a predetermined value, the travel motor 5 is automatically switched to the first speed state by the deceleration signal from the control device 72. When the load acting on the traveling motor 5 becomes larger than a predetermined value, the motor capacity is automatically increased and the driving force of the traveling motor 5 is increased.

When the pressures in the discharge circuits 28 and 29 of the first and second pumps P1 and P2 drop below a predetermined pressure, a return signal (excitation signal) is transmitted and the traveling second speed switching valve V16 is moved to the second speed position 70. In this case, both the first detection means 73 and the second detection means 74 indicate that the pressures of the discharge circuits 28 and 29 of the first and second pumps P1 and P2 are less than a predetermined pressure. When detected, a return signal is transmitted.
Further, a return signal is transmitted with a time lag when the pressure of the discharge circuits 28 and 29 of the first and second pumps P1 and P2 drops below a predetermined pressure and the traveling motor 5 returns to the second speed state.

  That is, while the traveling motor 5 is switched to the second speed state by the traveling second speed operation means 71, a predetermined load or more is applied to the traveling motor 5 and the traveling motor 5 is automatically decelerated to the first speed state. In this case, the response time when the deceleration signal is transmitted to the traveling second speed switching valve V16 after the first and second detection means 73 and 74 detect a pressure higher than a predetermined value is fast, and the first and second pumps P1. , P2 is a response time when a return signal is transmitted to the traveling second speed switching valve V16 to return the traveling motor 5 from the first speed state to the second speed state when the pressure of the discharge circuits 28, 29 drops below a predetermined pressure. By delaying the return to the second speed position 70 of the travel second speed switching valve V16 (by providing a second speed return delay time), the motor drive circuit is switched as the travel motor 5 switches to the large capacity state. 61 negative Even if the pressure decreases, it does not immediately return to the small capacity state, but can maintain the large capacity state of the traveling motor 5 and build a stable system against hunting associated with the capacity change of the traveling motor 5. Can do.

In constructing a stable system against hunting associated with the capacity change of the traveling motor 5,
When the first and second detection means 73 and 74 detect a pressure higher than a predetermined value, a deceleration signal is transmitted to the traveling second speed switching valve V16 to automatically decelerate the traveling motor 5 from the second speed state to the first speed state. The detection pressures of the first and second detection means 73 and 74 are X,
When the pressure of the discharge circuits 28 and 29 of the first and second pumps P1 and P2 drops below a predetermined pressure and a return signal is transmitted to return the traveling motor 5 from the first speed state to the second speed state, If the detection pressure of the detection means 73 and 74 is Y,
The detection pressures of the first and second detection means 73 and 74 are set so that X> Y (that is, the detection pressure when the traveling motor 5 is automatically decelerated is high, and the traveling motor 5 is returned to the second speed state. The detection pressure may be set low).

In addition, the control for providing these second speed return delay times and the control for setting the detection pressure when the traveling motor 5 is returned to the second speed state to be lower than the detection pressure when the traveling motor 5 is automatically decelerated are performed. You may use together.
In addition, it is preferable that the detection pressure setting of the first and second detection means 73 and 74, and the second speed return delay time can be freely changed.
In the traveling automatic deceleration system according to the present embodiment, when a traveling load is applied to the traveling motor 5 while the traveling motor 5 is traveling in the second speed state, the traveling motor 5 is moved to the second speed. The operation at the time of automatically decelerating from the state to the first speed state does not depend on the oil temperature of the pressure oil as in the past.

Further, in the conventional automatic traveling deceleration system, it is necessary to form a step in the spool of the cylinder control valve or to form an input unit for inputting a load detection signal from the high pressure side of the motor drive circuit. Although there is a problem that the valve is complicated, the cylinder control valve V19 can be simplified in the present embodiment.
Further, when a load is applied to the traveling motor 5, the left and right traveling motors 5 can be automatically decelerated simultaneously, and the movement of the actual vehicle can be stabilized.
In the present embodiment, the first and second detection means 73 and 74 are connected to the upstream side of the traveling valve V12, but may be provided downstream of the traveling valve V12. In this case, the third detection means 75 is not necessary.

Further, the third detection means 75 may detect the movement of the travel levers 24 and 25 themselves with a limit switch or the like.
Further, in this hydraulic system, the turning motor 13 is constituted by a swash plate type variable capacity axial motor that can be shifted to high and low speeds, for example, an operation of placing soil sown by a bucket 19 on a truck bed. , The swivel base 10 is swung while the boom 17 is raised, but the swivel speed of the swivel base 10 is set with emphasis on the mobility when swiveling without any work. The swivel base 10 turns to the target position before the boom 17 is raised to the target position because the turning speed is too high for the 17-lifting action (the boom 17 raising action and the turning action are not matched). To solve the problem, the turning motor 13 automatically decelerates the turning motor 13 from the high speed state to the low speed state when the boom 17 or the arm 18 is swung. It is equipped with a fast system.

This turning automatic deceleration system will be described with reference to FIGS.
The turning motor 13 is supplied with pressure oil from the turning control valve V <b> 1 to one of the pair of motor drive circuits 81 by tilting the left control lever 26 to the left or right, and is discharged through the other motor drive circuit 81. When the left control lever 26 is tilted left and right, pressure oil is supplied from the turning control valve V1 to the other of the pair of motor drive circuits 81 and drained via the motor drive circuit 81. Driven in reverse.
Further, the turning motor 13 is switched between a high speed state (small capacity state) and a low speed state (large capacity state) by changing the angle of the swash plate by a swash plate switching cylinder (swash plate switching actuator) 82. However, when the swash plate switching cylinder 82 is not operated, the swing motor 13 is switched to the high speed state by the spring 83, and by operating the swash plate switching cylinder 82 (extending the rod), the swing motor 13 is switched to the low speed state.

The swash plate switching cylinder 82 is connected to an output port g of a cylinder control valve (actuator control valve) V21 through a cylinder operating circuit 84. An input port h of the cylinder control valve V21 is connected to a pair of valves via an operating pressure supply circuit 85. A drain circuit d is connected to the drain port i of the cylinder control valve V21.
The operating pressure supply circuit 85 includes a first oil passage 85a having one end connected to the input port h of the cylinder control valve V21, a shuttle valve 85b having an output connected to the other end of the first oil passage 85a, A second oil passage 85c that communicates one input side of the shuttle valve 85b with one motor drive circuit 81, and a third oil passage 85d that communicates the other input side of the shuttle valve 85b with the other motor drive circuit 81; The pressure oil on the high pressure side of the pair of motor drive circuits 81 is sent to the cylinder control valve V21 as the operating pressure of the swash plate switching cylinder 82.

The cylinder control valve V21 is constituted by a direct-acting spool type pilot operation switching valve, and a high-speed position 86 for bringing the turning motor 13 into a high-speed state by connecting the cylinder operation circuit 84 to the drain circuit d, and an operating pressure supply circuit 85. The pressure oil from is sent to the cylinder operating circuit 84 and the swash plate switching cylinder 82 is operated to switch to the low speed position 87 where the swing motor 13 is in the low speed state.
A spring 88 is provided on one end side of the spool of the cylinder control valve V 21, and a pilot port j on one end side of the spool communicates with the input port h through a pressure detecting circuit 89.

One end side of the command circuit 90 is connected to the pilot port k on the other end side of the spool of the cylinder control valve V21, and the other end side of the command circuit 90 is connected to the output port m of the turning deceleration valve V22.
The turning deceleration valve V22 is constituted by a direct acting spool type pilot operation switching valve, and pressure oil from the fourth pump P4 is inputted to the input port n of the turning deceleration valve V22 via the unloading valve V15.
This turning deceleration valve V22 has a supply position 91 for supplying the pressure oil input to the input port n as a command pressure (pilot pressure) to the cylinder control valve V21 via the command circuit 90, and the command circuit 90 as a drain circuit d. Is switched to a non-supply position 92 that does not supply command pressure to the cylinder control valve V21, is switched to a supply position 91 by a spring 93, and is not supplied by a pilot pressure input to the pilot port s. 92.

A pilot circuit 95 is branched from an arm cloud command circuit 94 for sending pilot pressure from the pilot pilot valve PV3 operated by the left control lever 26 to the cloud operation side of the arm control valve V6. A pilot circuit 97 is branched from a boom raising command circuit 96 for sending pilot pressure from the pilot pilot valve PV4 to be operated to the raising operation side of the boom control valve V8. These pilot circuits 95 and 97 are pilot ports of the turning deceleration valve V22. connected to s.
In the above-described configuration, when the control levers 26 and 27 are not performing the boom raising operation or the arm cloud operation, the turning deceleration valve V22 is switched to the supply position 91 by the spring 93 and is supplied from the fourth pump P4. Since the pressure oil is supplied to the pilot port k on the other end side of the cylinder control valve V21 through the command circuit 90, the cylinder control valve V21 is switched to the high speed position 86 and the cylinder operation circuit 84 communicates with the drain circuit d. The turning motor 13 is in a high speed state.

Therefore, the turning motor 13 is normally used in this high speed state.
When the swivel base 10 is swung, if the load of the swivel motor 13 increases and the pressure of the motor drive circuit 81 becomes higher than a predetermined pressure, the cylinder control valve V21 is moved to the low speed position 87 by the pressure of the pressure detection circuit 89. And the swash plate switching cylinder 82 is operated, and the turning motor 13 is automatically switched from the high speed state to the low speed state.
As a result, the volume of the third pump P3 is not increased more than necessary, and the volume of the third pump P3 can be reduced.

When the control levers 26 and 27 are operated to raise the boom or the arm cloud, the turning deceleration valve V22 is switched to the non-supply position 92 by the pilot pressure from the pilot circuits 94 and 97, and the pressure oil from the fourth pump P4 is commanded. It is drained without being supplied to the circuit 90.
If the pressure from the fourth pump P4 is not supplied to the pilot port k on the other end of the spool of the cylinder control valve V21, the cylinder control valve V21 is switched to the low speed position 87 by the pressure of the spring 88 and the pressure detection circuit 89, and the swash plate The switching cylinder 82 is operated, and the turning motor 13 is automatically switched from the high speed state to the low speed state.

Therefore, for example, when the boom 17 and the swivel base 10 are operated simultaneously, for example, when the swivel base 10 is swung while the boom 17 is lifted, the swing motor 13 is automatically decelerated and the boom 17 is lifted ( The speed of the boom 17 and the turning operation of the turntable 10 (speed of the turntable 10) match.
Further, when the boom 17 or the arm 18 is not operated, the swivel base 10 has good maneuverability because the swivel motor 13 is swung in a high speed state.
Further, there is no inconvenience that the amount of tilting of the control levers 26 and 27 must be adjusted in order to match the raising operation of the boom 17 and the turning operation of the turntable 10.

In this embodiment, the swing motor 13 is automatically decelerated when the boom 17 is raised or the arm 18 is clouded. However, the present invention is not limited to this. The swing motor 13 may be automatically decelerated when the lowering operation or the arm 18 is dumped.
Further, the cylinder control valve V21 and the swing deceleration valve V22 may be configured by electromagnetic valves, and when the cylinder control valve V21 is configured by an electromagnetic valve, the swing deceleration valve V22 is unnecessary.

It is the whole backhoe side view. 1 is an overall hydraulic circuit diagram. FIG. 3 is a hydraulic circuit diagram of an operating system for a traveling valve and a flow path switching valve. It is a hydraulic circuit diagram of a traveling automatic deceleration system. It is a hydraulic circuit diagram of a turning automatic deceleration system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Traveling body 10 Turning table 11 Ground working apparatus 13 Turning motor 17 Boom 18 Arm 81 Motor drive circuit 82 Swash plate switching cylinder (swash plate switching actuator)
86 High-speed position 87 Low-speed position 90 Command circuit 91 Supply position 92 Non-supply position V21 Actuator control valve V22 Turning deceleration valve

Claims (4)

A swivel base (10) is mounted on the traveling body (2) so as to be pivotable about an axis in the vertical direction, and a swingable boom (17) and an arm ( In a backhoe equipped with a ground work device (11) with 18)
The turning motor (13) for turning the turntable (10) is configured to be capable of shifting to high and low speeds, and the turning motor (13) is normally used at a high speed, and the boom (17) or the arm (18) A backhoe characterized in that the swing motor (13) is automatically switched to a low speed state during a swing operation.   The swing motor (13) is constituted by a swash plate type variable displacement hydraulic motor, and is switched between a high speed state and a low speed state by switching the swash plate via a swash plate switching actuator (82). 82) is provided, and the actuator control valve (V21) switches the swing motor (13) to a high speed state (86) and the swing motor (13) to a low speed state. When the boom (17) or the arm (18) is swung while being switched to the low speed position (87) and normally switched to the high speed position (86) by the pilot pressure from the command circuit (90). The pilot pressure from the command circuit (90) is drained to switch to the low speed position (87). Backhoe according to claim 1, characterized in that   It is configured to be switchable between a supply position (91) for sending pilot pressure to the command circuit (90) and a non-supply position (92) for draining pressure oil in the command circuit (90), and the boom (17). The backhoe according to claim 2, further comprising a turning deceleration valve (V22) configured to be switched to the non-supply position (92) when the arm (18) is swung.   When the load acting on the swing motor (13) becomes larger than a predetermined value, the pressure of the motor drive circuit (81) for driving the swing motor (13) is detected and the actuator control valve (V21) is moved from the high speed position (86) to the low speed position. The backhoe according to any one of claims 1 to 3, wherein the backhoe is configured to be automatically switched to (87).

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