JP2001219776A - Hydraulic selector value and pto interlocking device for lifting load deck of dump truck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To speedily and certainly exchange a movable value element from a down position to a neutral position to instantly stop a falling operation of a load deck without being affected by an exchanging failure of a power taking device even when the load deck is intended to be stopped in an emergency, in a hydraulic selector valve and a PTO interlocking device of a dump truck in which an exchanging operation member for exchanging the power taking device to a connection state and a cut off state is interlocked and connected to the movable valve element of the hydraulic selector valve for a load deck lifting operation. SOLUTION: An exchanging time a when the power taking device PTO is shifted from the shut off state to the connection state is set not to coincident with a shifting traversing time from the down position D to the neutral position N of the movable valve element S.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic switching valve / PTO interlocking device for lifting and lowering a cargo box of a dump truck, and more particularly to a power take-out device interposed between a power unit and a hydraulic pump and capable of connecting and disconnecting between the power unit and a hydraulic pump. A hydraulic cylinder for raising and lowering the box, and a hydraulic switching valve interposed between the hydraulic cylinder and the hydraulic pump / oil tank. The hydraulic switching valve transfers hydraulic oil from the hydraulic pump to the hydraulic cylinder. A lifting position for supplying and raising the packing box, a neutral position for stopping the hydraulic oil from the hydraulic cylinder to return to the oil tank and stopping the packing box at an arbitrary tilt position, and a hydraulic oil for transferring the hydraulic oil from the hydraulic cylinder to the oil tank. A movable valve body that can be selectively moved between a lowered position where the packing box is lowered while allowing the return of the cargo box, and a power take-out device includes a switching operation member that switches the state between a connected state and a cutoff state. Have And operatively connected to cause the movable valve body switching operation member, a hydraulic switching valve · PTO interlock device having a structure as a power take-off is placed in a connected state when it is in its movable valve body is raised position.

[0002]

2. Description of the Related Art A hydraulic switching valve PT
The O interlocking device is conventionally known (for example, Japanese Utility Model 2-41362).
Reference).

In a conventional apparatus, as shown in FIG. 5, a switching timing a 'at which the power take-off device PTO switches from a cut-off state to a connected state, that is, a drive provided at a drive-side element and a driven-side element of the power take-off apparatus, respectively The meshing start timing at which the teeth and the driven teeth start to mesh with each other is set so as to come during the switching movement process from the lowered position D of the movable valve body of the hydraulic switching valve to the neutral position N.

[0004]

However, as in the above-described conventional apparatus, the movable valve body is in the process of switching from the lowered position to the neutral position (ie, an intermediate position between the lowered position and the neutral position).
In the configuration in which the power take-off device is switched from the cut-off state to the connected state, when the movable valve body is switched from the lowered position to the neutral position during the lowering operation of the packing box, an emergency stop of the packing box is required. There are the following problems.

For example, in the high-speed rotation state of the power unit, the relative rotation speed of the driving teeth and the driven teeth of the power take-out device is too high to be able to mesh well, so that the power take-out device is smoothly switched from the cut-off state to the connected state. Can not do. Therefore, even when the movable valve element of the hydraulic switching valve, which is interlocked with the switching member of the power take-off device, is moved from the lowered position to the neutral position when the power unit rotates at a high speed, the above-mentioned switching failure of the power take-off device results. As a result, the movable valve element stops in the middle of the stroke (that is, between the lowered position and the neutral position), and it is difficult to completely switch to the normal neutral position. In such a case, once the clutch in the power unit is disengaged, the power take-off device can be switched to the connected state and the movable valve element can be switched, but the series of operations is complicated and quick. , Lacks certainty. Therefore, there is a possibility that a quick and accurate response cannot be taken in an emergency where the lowering operation of the packing box should be stopped immediately.

When the power unit is stopped,
The power take-off device may not switch to the connected state because the drive teeth and driven teeth of the power take-off device do not mesh well with each other depending on their stop positions. At this time, even if an attempt is made to switch the movable valve body of the hydraulic switching valve, which is interlocked with the switching operation member of the power take-off device, from the lowered position to the neutral position, the movable valve body is caused due to the switching failure of the power take-off device. Stops in the middle of the stroke, making it difficult to completely switch to the normal neutral position. Therefore, also in this case, it is necessary to switch the movable valve body by switching the power take-off device to the connected state by disengaging the clutch or starting the power unit.
This also has the same problem as during the high-speed rotation.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and can solve the problem of the above-mentioned conventional device with a simple structure.
It is intended to provide a TO interlocking device.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a power take-out device interposed between a power unit and a hydraulic pump and capable of connecting and disconnecting between the power unit and a hydraulic pump. A hydraulic cylinder, and a hydraulic switching valve interposed between the hydraulic cylinder and the hydraulic pump / oil tank. The hydraulic switching valve supplies hydraulic oil from the hydraulic pump to the hydraulic cylinder to form a packing box. The lifting position, the neutral position where the return of the hydraulic oil from the hydraulic cylinder to the oil tank is stopped, and the packing box stops at an arbitrary tilt position, and the return of the hydraulic oil from the hydraulic cylinder to the oil tank is allowed. The power take-off device has a movable valve body which can be selectively moved between a lowered position for lowering the packing box, and a power take-out device. Movable valve element for member And is interlocked, the movable valve body is a power take-off when in the raises position was to be placed in the connected state, the hydraulic selector valve, for dump truck cargo box lift
The PTO interlocking device is characterized in that the switching timing at which the power take-off device switches from the shut-off state to the connected state is set so as not to coincide with the switching movement timing of the movable valve body from the lowered position to the neutral position.

According to the above feature, the power take-off device is not switched from the shut-off state to the connected state during the switching movement of the movable valve body from the lowered position to the neutral position. Even if is mechanically linked to the switching member of the power take-off device, the movable valve body can be switched from the lowered position to the neutral position at once without being affected by the switching failure of the power take-off device. Therefore, even when an emergency stop is to be performed during the lowering operation of the packing box, the moving valve body is quickly and reliably switched from the lowered position to the neutral position without being affected by the power take-out device, and the lowering operation of the packing box is immediately performed. Can be stopped.

According to a second aspect of the present invention, in addition to the features of the first aspect of the present invention, the movable valve body can be moved to a standby position set on the opposite side of the neutral position with the lowered position interposed therebetween. The movable valve body is configured to allow the return of the hydraulic oil from the hydraulic cylinder to the oil tank and lower the packing box over the entire section from the standby position or the lowering position. The power take-off device is placed in a shut-off state when the valve is in the standby position, and the switching time comes during the valve body moves from the standby position toward the lowered position. I have.

According to this feature, the movable valve body is in the lowered position.
During the switching operation between the neutral position and the raised position,
Since the connection / disconnection switching of the power take-off device is not performed and there is no need to perform any troublesome clutch operation for switching the device from the cutoff state to the connection state, the dumping operation of the packing box becomes simpler.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below based on embodiments of the present invention illustrated in the accompanying drawings.

1 to 3 show a first embodiment of the apparatus of the present invention. In particular, FIG. 1 is an overall vertical sectional view, and FIG. 2 is a power take-out at each operation position. FIG. 3 is an enlarged cross-sectional view showing the relational configuration of the device / hydraulic switching valve, and FIG. 3 is an explanatory diagram showing the relationship between the stroke of the movable valve body and each switching mode of the power take-out device / hydraulic switching valve. FIG. 4 is an explanatory diagram showing the relationship between the stroke of the movable valve body and each switching mode of the power take-out device / hydraulic switching valve in the second embodiment, and FIG. 5 shows the stroke and the power of the movable valve body in the conventional example. It is explanatory drawing of the relationship with each switching mode of an extraction apparatus and a hydraulic switching valve.

First, referring to FIG.
The cargo box 1 mounted on the upper part is pivotally mounted on the vehicle body F so as to be tiltable.
A hydraulic cylinder Cy for raising and lowering the packing box 1 is interposed between the packing box 1 and the vehicle body F. Thus, the packing box 1 swings upward due to the extension of the hydraulic cylinder Cy,
Further, it swings down due to contraction.

The traveling power unit PU mounted on the vehicle body F includes an engine and a transmission interlocked with the engine via a clutch as is well known in the art. A transmission system connected to the wheels is connected. The power unit P also has a hydraulic pump P which takes out the power of the engine at the output side of the clutch as needed.
A power take-out device PTO for driving the motor is provided.

The hydraulic pump P has a suction side connected to an oil tank T, and a discharge side connected to a base oil chamber Ca on the piston side of a hydraulic cylinder Cy via an output oil passage 3. The oil chamber Cb on the piston rod side of the hydraulic cylinder Cy is connected to the oil tank T via the return oil passage 4.

A spool valve V as a hydraulic switching valve is interposed in an oil passage connecting the hydraulic cylinder Cy with the hydraulic pump P and the oil tank T. The spool valve V is formed by fitting a spool valve element S as a movable valve element in a valve hole 5v formed in the housing 5 so as to be slidable in the axial direction. From the hydraulic cylinder Cy to the base oil chamber Ca of the hydraulic cylinder
Raising position U shown in FIG. 2 (see (d) of FIG. 2)
And a neutral position N for stopping the return of the hydraulic oil from the base oil chamber Ca of the hydraulic cylinder Cy to the oil tank T and stopping the packing box 1 at an arbitrary tilting position (see FIG. 2C). When,
Lowering position D for lowering the packing box 1 while allowing the return of the hydraulic oil from the base oil chamber Ca of the hydraulic cylinder Cy to the oil tank T
As shown in FIG. 2 (b), a standby position D 'for lowering the packing box 1 while allowing the return of the hydraulic oil from the base oil chamber Ca of the hydraulic cylinder Cy to the oil tank T (FIG. 1) Can be selectively operated.

The hydraulic pump P is constituted by a conventionally known gear pump or the like and is built in the housing 5. The housing 5 is formed with a suction port 6 and a discharge port 7 which are respectively connected to a suction side and a discharge side of the hydraulic pump P. The suction port 6 communicates with the oil tank T, and the discharge port 7 has a valve hole. Annular groove 8 formed on the inner peripheral surface of 5v
It is open to. Further, the annular groove 8 is provided in the housing 5.
An output port 9 which is always in communication with the suction port 6 via the suction port 6 (ie irrespective of the sliding position of the spool valve element S), and a valve hole at a position deviated to one side and the other side of the annular groove 8 respectively. A discharge port 10 and a return port 11 that are directly opened to 5v are formed.

The output port 9 is communicated with a base oil chamber Ca of the hydraulic cylinder Cy via a check valve Vc built in the housing 5, and the discharge port 10 bypasses the check valve Vc and is connected to the hydraulic cylinder Cy. The return port 11 is always connected to the oil tank T, and is always connected to the base oil chamber Ca. Thus, the suction port 6, the annular groove 8 and the output port 9 constitute a part of the discharge oil passage 3.
Further, the check valve Vc permits only one-way oil flow from the output port 9 to the hydraulic cylinder Cy, and prevents the flow in the opposite direction.

The spool valve element S has a wide and annular oil passage groove straddling the discharge port 10, the output port 9 and the return port 11 on the outer peripheral surface thereof, and an axial direction with the oil passage groove g interposed therebetween. And first and second land portions L1 and L2 slidingly contacting the valve hole 5v. Thus, when the spool valve element S is in the lowered position D shown in FIG.
The return port 11 communicates with the suction port 6 and the discharge port 10 through the oil passage g, so that the discharge oil of the hydraulic pump P is short-circuited to the oil tank T side, while the hydraulic oil in the base oil chamber Ca of the hydraulic cylinder Cy is discharged. The cylinder returns to the oil tank T based on the weight of the cargo box 1 and the load, and the cylinder contracts.

When the spool valve element S is at the neutral position N shown in FIG. 2C, the first land portion L1 is connected to the annular groove 8 (therefore, the output port 9 and the discharge port 7). It is shut off from the discharge port 10 while maintaining the communication state with the return port 11. Accordingly, while the discharge oil of the hydraulic pump P is short-circuited to the oil tank T side, the return of the hydraulic oil from the base oil chamber Ca of the hydraulic cylinder Cy to the oil tank T side is prevented, and the operation of the cylinder is kept stopped. It is.

Further, when the spool valve element S is at the raised position U shown in FIG. 2D, the first land portion L1 moves through the annular groove 8 (accordingly, the output port 9 and the discharge port 7) to the return port 11 and While shutting off from the discharge port 10, the return port 11 and the discharge port 10 are also cut off from each other. Accordingly, the discharge oil of the hydraulic pump P is not short-circuited to the oil tank T side, but is sent to the base oil chamber Ca of the hydraulic cylinder Cy by pressure to extend the cylinder.

The pump shaft Pj of the hydraulic pump P and the power take-off shaft 15 as a driven element of the power take-off device PTO are arranged on the same axis, and are interposed so that they rotate integrally. Are connected and rotatably fitted to and supported by the housing 5. Power take-off shaft 15
A cylindrical slider 16 is spline-fitted 17 so as to be slidable in the axial direction and relatively non-rotatable, and a driven gear 18 as a driven tooth is integrally formed on the outer periphery of one end of the slider 16. Provided. A drive gear 19 as a drive tooth that can mesh with the driven gear 18 is provided integrally with a drive shaft 20 as a drive-side element rotatably supported by the housing 5. The drive unit 19 is operatively connected to a transmission input shaft or output shaft of the power unit PU via a drive gear 19. Therefore, the power unit P
When the U engine is operating and the clutch is in the engaged state, the drive shaft 20 receives the engine output and rotates.

The slider 16 slides a predetermined stroke from the cut-off position (see FIG. 1) where the driven gear 18 is not meshed with the drive gear 19, and slides the two gears 1 by a predetermined stroke.
Connection positions where the gears 8 and 19 are fully engaged (see FIG. 2 (c),
(See (d)). An annular engagement groove 16 a is formed on the outer periphery of the slider 16, and a fork-shaped tip 21 a of a shift fork 21 for driving and controlling the slider 16 is engaged with the engagement groove 16 a. .

The shift fork 21 constitutes a switching operation member of the power take-out device PTO, and its base 21b is formed in a cylindrical shape. An outer peripheral portion of the cylindrical base portion 21b is slidably fitted in a support hole 5a formed in the housing 5, and an inner peripheral portion of the shift shaft 22 slidably fitted and supported in the housing 5 is provided. The outer periphery is slidably fitted.

The shift shaft 22 is coaxially and integrally connected to one end of a spool valve S in the illustrated example. An interlocking mechanism I is interposed between the shift shaft 22 and the shift fork 21 to mechanically interlock the shift shaft 22 and the shift fork 21 therebetween. In the illustrated example, the interlocking mechanism I includes an annular first engagement groove 22a formed on the outer periphery of the shift shaft 22, and an engagement hole 23 formed in the base 21b of the shift fork 21 corresponding to the engagement groove 22a.
And an annular second engagement groove 25 formed in the support hole 5a.
And a ball 24 fitted in the engagement hole 23 and selectively engageable with the first engagement groove 22a or the second engagement groove 25. This ball 24 is shown in FIGS.
As shown in (b), the shift fork 2 is in the first engagement state in which the first fork 2 is engaged across the first engagement groove 22a and the engagement hole 23.
2 restricts the relative movement of the shift shaft 21 and the shift fork 21 in the axial direction while permitting the axial movement with respect to the housing 5, and as shown in FIGS. In the second engagement state in which the shift shaft 21 and the shift fork 21 are moved relative to each other in the axial direction, the shift fork 21 is restricted in the axial direction with respect to the housing 5 in the second engagement state in which the shift shaft 21 and the shift fork 21 are mutually engaged. Slider 1
6 in the connection position.

An operating device Co for selectively switching the switching position of the spool valve element S is connected to an outer end of the spool valve element S via an interlocking rod 27. The operating device Co includes the standby position D ', the lowered position D, and the neutral position N of the spool valve element S.
And an operating lever L having four operating positions d ', d, n, u respectively corresponding to the lifting position U,
A holding mechanism (not shown) that can selectively hold the operation lever L at the four switching positions d ', d, n, and u is connected to the operation lever L.

Next, the operation of the above embodiment will be described with reference to FIG.

While the vehicle is running, the operating lever L is in the first operating position d '. When the operation lever L is at the first operation position d 'and the spool valve element S is at the standby position D', the slider 16 moves the driven gear 18 away from the drive gear 19 as shown in FIG. In the shut-off position, the engine output is not transmitted to the hydraulic pump P, and the pump P is stopped. In this state, the ball 24 is in the first engagement state in which the ball 24 is engaged across the first engagement groove 22a and the engagement hole 23, and the shift fork 21
The axial movement of the shift shaft 21 and the shift fork 21 relative to each other in the axial direction is restricted while allowing the axial movement of the shift shaft 21 with respect to the housing 5.

In this state, the operation lever L is operated toward the second operation position d, and the spool valve S
When the driven gear 18 slides only to reach the first switching position X (see FIG. 2A) just before the lowering position D, the driven gear 18
9 starts to be engaged. This engagement start time corresponds to the switching time a of the power take-off device PTO from the cut-off state to the connected state, and thereafter, the driven gear 18 gradually meshes with the drive gear 19 as it moves to the right, and the power take-out takes place. The device PTO approaches the fully connected state from the incompletely connected state.

When the operating lever L is moved to the second operating position d after passing the first switching position X, the spool valve S
Reaches the lowering position D shown in FIG. 2B, and the normal lowering operation of the packing box 1 is performed at this position. After this position, the opening of the discharge port 10 gradually decreases as the spool valve element S approaches the neutral position N, and this state is an incompletely lowered state.

Further, the operating lever L is operated toward the third operating position n, and the spool valve element S starts sliding from the standby position D 'by the stroke A to reach the second switching position Y before the neutral position N. When it comes, the driven gear 18 and the drive gear 19 are fully engaged with each other, and the power take-off device PTO is completely connected. At this time, the ball 24 is in the first engagement groove 22a.
The shift shaft 21 and the shift fork 21 are allowed to move relative to each other in the axial direction because they are further separated from each other and are brought into the second engagement state in which they are engaged across the second engagement groove 25 and the engagement hole 23. While restricting axial movement of the shift fork 21 with respect to the housing 5. Therefore, after this, shift fork 2
While the power take-off device PTO is kept in a completely connected state with 1 left behind, only the shift shaft 22 and the spool valve element S slide toward the neutral position N.

When the operating lever L has been operated to the third operating position n, the spool valve element S has slid by the stroke B starting from the standby position D ', and the neutral position shown in FIG. At this position, the packing box 1 is held in the up / down stopped state. After this position, the spool valve S
Groove 8 and return port 1 as
The effective cross-sectional area of the communicating portion between the two gradually decreases, and this state is an incompletely raised state.

Further, when the operation lever L is operated to the fourth operation position u, the spool valve element S slides by a stroke C from the neutral position N, and moves to the raised position U shown in FIG. At this position, a normal lifting operation of the packing box 1 is performed at this position.

Thus, the switching timing a at which the power take-off device PTO is switched from the cut-off state to the connected state (incompletely connected state in the illustrated example) is changed from the lowered position D of the spool valve body S as the movable valve body to the neutral position N. The timing is set so as not to coincide with the switching movement time, that is, during the switching movement of the valve body S from the lowered position D to the neutral position N, the power take-off device PTO is not switched from the cut-off state to the incompletely connected state. Since the,
Even if the spool valve element S of the hydraulic switching valve V is mechanically connected to the shift fork 21 which is a switching operation member of the power take-off device PTO, the valve body S is moved from the lowered position D to the neutral position N to take out power. The switching operation can be performed at once without being affected by the switching failure of the device PTO. for that reason,
Even in the event of an emergency stop of the packing box 1 during its lowering operation, the spool valve element S is quickly and reliably switched from the lower position D to the neutral position N without being affected by the power take-off device PTO. The descending operation can be stopped immediately.

In this embodiment, the spool valve S
Can be moved to a standby position D 'specially set on the opposite side of the neutral position N with the lowering position D interposed therebetween, and
Over the entire section from the standby position D 'to the lowered position D,
It is configured to allow the return of the hydraulic oil from the hydraulic cylinder Cy to the oil tank T so that the packing box 1 can be lowered.
When the spool valve element S is at the standby position D ', the power take-off device PTO is placed in the shut-off state, and while the valve element S is moving from the standby position D' toward the lowered position D,
The switching timing a is set such that the power take-out device PTO is switched from the cut-off state to the connected state (incompletely connected state in the illustrated example). Therefore, while the spool valve element S is switched between the lower position D, the neutral position N, and the upper position U,
Since the power take-off device PTO is not switched between connection and disconnection, and there is no need to perform any troublesome clutch operation for switching the device from the disconnected state to the connected state, the dumping operation of the packing box 1 becomes simpler.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the power take-off device PTO
In order to prevent the switching timing a for switching from the shut-off state to the connected state (incompletely connected state in the illustrated example) from being shifted from the lowered position D of the spool valve body S to the neutral position N, the switching timing a The switching timing a is set to the neutral position N of the spool valve element S.
(In the illustrated example, a position immediately after the neutral position N, that is, a position to shift to the incompletely raised state).

Accordingly, in this embodiment, when the spool valve element S is switched from the neutral position N to the raising position U, if the switching cannot be performed smoothly, the power unit PU
The power take-off device PTO is switched from the cut-off state to the disconnected state by, for example, once disengaging the clutch, and then the spool valve element S is switched to the raised position U.

Thus, in this embodiment, basically the same effects as in the first embodiment can be achieved.

The embodiments of the present invention have been described above.
The present invention is not limited to this embodiment, and various embodiments are possible within the scope of the present invention. For example, in the above-described embodiment, the pump shaft Pj of the hydraulic pump P and the power take-off shaft 15 are formed integrally, but in the present invention, they may be formed separately and connected in an interlocking manner. Further, in the above-described embodiment, the spool valve element S as the movable valve element and the shift shaft are formed integrally, but in the present invention, they may be formed separately and interlocked.

[0041]

As described above, according to the first aspect of the present invention,
The timing of switching the power take-off device from the shut-off state to the connected state is not overlapped with the timing of moving the hydraulic switching valve from the lowered position to the neutral position of the movable valve body. Even when the movable valve body is mechanically linked to the switching operation member, the movable valve body can be switched from the lowered position to the neutral position at once without being affected by the switching failure of the power take-off device. Even in the event of an emergency stop during the descent operation, the movable valve body can be quickly and reliably switched from the lowered position to the neutral position without being affected by the power take-off device, and the cargo box can be stopped immediately, thereby ensuring work safety. The performance is improved. In addition, since the above-mentioned effect can be obtained with a simple configuration in which the connection / disconnection switching timing of the power take-out device is simply set as described above, the manufacturing cost can be reduced.

According to the second aspect of the present invention, the movable valve body can be moved to a standby position set on the opposite side to the neutral position with the lowered position interposed therebetween, and the movable valve body can be moved from the standby position to the lowered position. The power take-off device is configured to allow the return of the hydraulic oil from the hydraulic cylinder to the oil tank over the entire section and to be able to lower the packing box, and when the movable valve body is at the standby position. Is placed in the shut-off state, and the switching timing comes during the movement of the valve body from the standby position to the lowering position, so that the movable valve body is moved to the three positions of the lowering position, the neutral position, and the raising position. Since the power take-off device is maintained in the connected state during the switching operation between the two, it is not necessary to perform the troublesome clutch operation for switching the device from the disconnected state to the connected state one by one. Work easier The rate can be improved.

[Brief description of the drawings]

FIG. 1 is an overall longitudinal sectional view showing a first embodiment of the apparatus of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a related configuration of a power take-out device and a hydraulic switching valve at each operation position in the first embodiment.

FIG. 3 is an explanatory diagram showing a relationship between a stroke of a movable valve body and respective switching modes of a power take-out device and a hydraulic switching valve in the first embodiment.

FIG. 4 is an explanatory diagram showing a relationship between a stroke of a movable valve body and each switching mode of a power take-out device and a hydraulic switching valve in a second embodiment.

FIG. 5 is an explanatory diagram showing a relationship between a stroke of a movable valve body and each switching mode of a power take-out device and a hydraulic switching valve in a conventional example.

[Explanation of symbols]

 1 ... packing box 21 ... shift fork (switching operation member) a ... transmission start timing Cy ... hydraulic cylinder D ... lowered position D '... standby position I ...・ Interlocking mechanism N ・ ・ ・ ・ ・ ・ Neutral position P ・ ・ ・ ・ ・ ・ Hydraulic pump PTO ・ ・ ・ ・ Power take-off device PU ・ ・ ・ Power unit S ・ ・ ・ ・ ・ ・ Spool valve (movable valve) T ・ ・ ・ ・ ・ ・ Oil tank U ・... Raised position V ... Spool valve (hydraulic switching valve)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3D043 AA06 BA03 BC09 BC12 BC20 BD02 BE01 3H089 BB15 BB27 CC01 DA02 DB46 DB49 DB75 DB76 GG02 HH07 JJ01

Claims (2)

[Claims] A power take-off device (PTO) interposed between a power unit (PU) and a hydraulic pump (P) and capable of connecting and disconnecting between the power unit (PU) and a hydraulic cylinder (PTO) for raising and lowering a packing box (1). Cy) and a hydraulic switching valve (V) interposed between the hydraulic cylinder (Cy) and the hydraulic pump (P) / oil tank (T). The hydraulic switching valve (V) Hydraulic oil from the pump (P) is supplied to the hydraulic cylinder (Cy) to raise the packing box (1), and a return position (U) for returning the hydraulic oil from the hydraulic cylinder (Cy) to the oil tank (T). Box (1) allowing the return of the hydraulic oil from the hydraulic cylinder (Cy) to the oil tank (T) and the neutral position (N) for stopping the packing box (1) at an arbitrary tilt position by preventing the A movable valve element (S) that can be selectively moved and operated between a lower position (D) for lowering the valve. Power take-off device (PTO)
Has a switching operation member (21) for switching between a connected state and a disconnected state, and has the switching operation member (21).
And a power take-off device (PTO) is placed in a connected state when the movable valve body (S) is at least in the raised position (U). In the hydraulic switching valve / PTO interlocking device for lifting and lowering the packing box, the switching timing (a) at which the power take-off device (PTO) switches from the shut-off state to the connected state is determined by the movable valve body (S) being lowered from the lowered position (D) to the neutral position. (H) The hydraulic switching valve / PTO interlocking device for raising and lowering the cargo box of a dump truck, which is set so as not to overlap with the switching movement time to (N). 2. The movable valve body (S) is in a lowered position (D).
Can be moved to a standby position (D ') set on the opposite side of the neutral position (N) with the interposition therebetween, and over the entire section from the standby position (D') to the lowered position (D), It is configured to allow the return of the hydraulic oil from the hydraulic cylinder (Cy) to the oil tank (T) so that the packing box (1) can be lowered, and the movable valve body (S) is in the standby position ( D '), the power take-off device (PTO) is placed in the shut-off state, and the switching is performed while the valve body (S) moves from the standby position (D') to the lowered position (D). 2. The hydraulic switching valve / PT for lifting / lowering a cargo box of a dump truck according to claim 1, wherein the timing (a) is set to come.
O interlocking device.