JPH069080Y2 - Hydraulic control circuit for dozer device blade - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to a hydraulic circuit for actuating a dozer blade mounted in front of a body of a hydraulic excavator.

2. Description of the Related Art Conventional dozer devices that are attached to the front of the machine body of earthmoving machines are called straight dozers, angle dozers, tilt dozers, etc., depending on the angle the cutting edge of the dozer blade makes with respect to the direction of travel of the machine body or the ground. However, due to the needs of the times, one machine is required to support all formats. As an example of the hydraulic operation of the dozer device that meets this requirement, there is a crawler type hydraulic excavator equipped with a dozer device in front of the traveling frame as shown in FIGS. 2, 3, and 4. The side view, FIG. 3 is a plan view, and FIG. 4 is a front view. It goes without saying that the blade is operated up and down by operating the hydraulic switching valve in the operator's cab. It is possible to freely select and use one of the three forms and the combination form thereof. In this figure, the upper revolving structure 60 in which the front attachment 62 is mounted on the upper surface of the traveling frame 63 around which the crawler belt is wound via the revolving bearing. Is mounted, and a dozer device D is provided in the forward direction of the traveling frame 63 and in the forward direction.

The dozer device D is roughly composed of a blade 9, a dozer frame 32, a lift cylinder 6, an angle cylinder 7, a tilt cylinder 8 and parts connecting them. Straight, angle, tilt and ascend / descend.

This will be described in detail with reference to the drawings. In FIGS. 5 and 6, the base portion of the dozer frame 32 is rotatably supported by a pin 34 on a bracket 36 fixed to the lower traveling frame 63. A bracket 41 is fixed to the central portion of the tip of the dozer frame 32, and a bracket 42 fixed to the back surface of the blade 9 is pivotally supported by a pin 40. However, the blade 9 is inclined at a predetermined angle with respect to the ground. It has a ball joint connection so that it can be
As shown in the figure, a turnbuckle 33 is assembled with pins 50, 50 between the bracket 51 on the upper center of the blade 9 and the bracket 52 on the dozer frame 32. The excavation angle is kept constant. A lift cylinder 6 is pivotally supported by pins 35, 35 between a bracket 43 fixed on the lower traveling frame 63 at a position higher than the bracket 36 and a bracket 44 fixed on the dozer frame 32. And 2 on the left and right of the back of the blade 9
The angle cylinder 7 is connected by the pins 37, 37 via the universal joints 39, 39 between the bracket 38 fixed at the position and the bracket 45 fixed on the side surface of the dozer frame 32.

Next, FIGS. 7 and 8 show a side surface of a partial cross section of a tilt mechanism for tilting the blade 9 with respect to the ground and the tilt cylinder 8.
7 is a plan view taken along the line XX in FIG. 7, showing a mounting state of the bracket, in which 46 is a bracket fixed to the front surface of the bracket 52 on the dozer frame 32, and 47 is the blade 9.
A tilt cylinder 8 that is a dedicated bracket fixed to the back surface and is connected between both brackets 46 and 47 via a universal joint 49 with pins 48 and 48.
Is a bracket 4 fixed to the front end of the dozer frame 32.
Bracket 4 away from the center of 1 by distance L
The positions of 6, 47 are set.

In the dozer device having the above configuration, when the lift cylinder 6 is expanded and contracted, the dozer frame 32 swings around the pin 34, so that the blade 9 mounted by the bracket 41, 42 pin 40, etc. Along with this, the angle cylinder 7 and the tilt cylinder 8 move up and down. Next, when the upper angle cylinder 7'is contracted and the lower angle cylinder 7 is extended in FIG.
Angle cylinder 7'to the right of the traveling direction
When is extended and contracted 7, it rotates to the left. Next, when the tilt cylinder 8 is expanded and contracted in FIGS. 7 and 8, the blade 9 is locked to the dozer frame 32 by the ball joint connection of the brackets 41 and 42 pins 40, and L
Since the operating force of the tilt cylinder 8 is applied at a certain distance, the blade 9 swings in a predetermined angle range with respect to the ground.

The connecting portions such as the pins 40, 48 and 50 for locking the dozer frame 32 and the blade 9, the tilt cylinder 8 and the bracket 47, and the turnbuckle 33 and the brackets 51 and 52 are mutually connected by boss portions such as the bracket or the cylinder. Not only the pin pivots about the shaft center, but also it is necessary to swing on a plane including the shaft, although it is small, as the blade 9 operates. An example is shown in FIG. That is, if the brackets at the respective positions are E and F and the pin is G, the pin G is loosely inserted in the inner diameter, and the outer peripheral portion is pinned through a spherical ball bush H centered on the center point O of the pin G. G and bracket E,
F is connected.

An embodiment of a conventional hydraulic circuit for operating the dozer device D having the above structure is as shown in FIG. 10. Reference numeral 1 denotes a hydraulic pump which is a hydraulic source for operating the dozer device D, and its discharge oil is an oil passage. The hydraulic pressure switching valve 2 for the lift cylinder 6, the hydraulic pressure switching valve 3 for the angle cylinder 7, and the hydraulic pressure switching valve for the tilt cylinder 8 in the switching valve group 55 after being regulated by the relief valve 5 to a prescribed pressure. In parallel to 4
When the hydraulic pressure switching valves are not operated, they return to the tank 22 through the center bypass passage and the oil passage 24.

To lower or raise the blade 9, the hydraulic switching valve 2
Is operated to switch from the C position to the A or B position, the pressure oil from the hydraulic pump 1 expands and contracts the lift cylinder 6 through the A or B position passage, the swivel joint 64, the oil passage 26 or 27, and the angle cylinder. It is realized by moving the dozer frame 32 up and down together with 7, 7'and the tilt cylinder 8. Next, operate the hydraulic pressure switching valve 3 to C
When the position is switched to the position A, the pressure oil passes through the oil passage 28 to extend the angle cylinder 7 and rotate the blade 9 to the right in the figure. As a result, the angle cylinder 7'contracts,
Return oil from the oil chamber returns to the tank 22 through the oil passage 29, the A position passage of the hydraulic pressure switching valve 3 and the oil passage 24.
Conversely, when the hydraulic pressure switching valve 3 is set to the B position, the angle cylinder 7'expands, the blade 9 rotates counterclockwise, and the angle cylinder 7 contracts. Moreover, the hydraulic pressure switching valve 4 is moved from the C position to the A position.
Alternatively, when the position is switched to the B position, the tilt cylinder 8 expands or contracts to tilt the blade 9 to the right or left with respect to the center point O of the pin 40 as described above.

Among the operations of the blade 9, the lift cylinder 6 and the angle cylinders 7 and 7'can be smoothly expanded and contracted independently or independently of the other cylinders. Although the expansion and contraction of the angle cylinders is slightly performed, the expansion and contraction of the angle cylinders 7 and 7'will be accompanied. That is, as is clear from FIGS. 5 and 6, although there are some differences depending on the structure of the dozer device D, the pin 37, which is the position where the angle cylinders 7 and 7'are attached to the back surface of the blade 9, is generally Since the blade 9 is located two-dimensionally away from the center point O of the pin 40, which is the center of rotation when the blade 9 leans to the left or right, the angle cylinders 7 and 7'are forced to move.
Is automatically expanded and contracted as the tilt cylinder 8 is expanded and contracted. For example, in the dozer device having the configuration shown in FIG. 6, when the tilt cylinder 8 extends and the blade 9 tilts to the right, the angle cylinder 7 contracts and the angle cylinder 7'needs to expand. It is difficult to artificially fine-tune 3 and 4 at the same time. Therefore, as shown in FIG.
The safety suction valve 6 is provided on the branch oil passage of the oil passages 28 and 29.
5, 66 are provided to relieve the excess oil caused by the contraction of the acgle cylinder 7 when the pressure exceeds a specified pressure, and replenish the insufficient oil caused by the extension of the angle cylinder 7'from the relief oil or the oil passage 25 leading to the tank. Was.

Problems to be Solved by the Invention When the conventional hydraulic circuit for operating a dozer device as described above is used in an earthmoving machine such as a hydraulic excavator having an upper swing body and a dozer device in a lower traveling frame,
Since each operating cylinder is mounted on the lower traveling frame side and the hydraulic power source and hydraulic switching valve are provided on the upper revolving structure side, the oil passages that communicate with each other must pass through the swivel joint, so keep the blades in place. If an external force acts when the tilt cylinder is operated, the tilt cylinder is operated, and the relief pressure of the safety suction valve is generated in the oil path of the angle cylinder for a long time regardless of the blade load. However, since it directly joins the swivel joint, it shortens the life of the swivel joint and cannot keep the position of the blade due to mutual leakage between the oil passages.
Also, when the tilt cylinder is operated, the angle cylinder is reduced against the relief pressure in the safety suction valve, so the angle cylinder and tilt cylinder must be larger than the external force applied to the blade, and the blade is also more than necessary. It is required to have high rigidity.

Means for Solving the Problems In order to solve the above problems, the present invention has the following hydraulic circuit configuration. That is, a. A pilot check valve that forms a free passage in the oil passage that communicates with the hydraulic fluid chamber of the lift cylinder blade riser, the hydraulic fluid chamber of the angle cylinder, and the tilt cylinder, and that allows reverse flow when pilot pressure acts. To provide.

B. The pilot oil chamber of the pilot check valve provided in the lift cylinder operating oil passage communicates with the oil passage communicating with the blade descending oil chamber.

C. The pilot oil chamber of the pilot check valve provided in each oil passage of the tilt cylinder expansion / contraction operation is communicated with the oil passage communicating with the oil chamber for the opposite operation.

D. In addition, the pilot oil chamber of the pilot check valve provided in the oil passage that communicates with the hydraulic oil chamber of the angle cylinder on the side that contracts when the tilt cylinder is actuated independently has the oil that communicates with the hydraulic oil chambers of other angle cylinders. The outlet port of the shuttle valve that selects the higher pressure of the passage or the oil passage leading to the hydraulic oil chamber of the tilt cylinder that tilts the blade in that direction.

Function When the blade hydraulic switching valve is switched to the position where the lift cylinder contracts, the pressure oil passes through the free passage of the pilot check valve and flows into the rod cylinder oil chamber of the lift cylinder, and the oil in the head oil chamber is the above hydraulic switching valve. After passing through, the blade rises against its own weight. To lower the blade, supply pressure oil to the head-side oil chamber of the lift cylinder, and the return oil from the rod-side oil chamber is once blocked by the pilot check valve. Rises to open the pilot check valve, so as long as the pressure oil is continuously supplied to the head side oil chamber, the lift cylinder extends and lowers the blade. Also, when the hydraulic pressure switching valve is in the neutral position, the pressure of the rod side oil chamber of the lift cylinder rises due to the weight of the blade, but the pilot check valve blocks the flow and the oil passage downstream of the pilot check valve is blocked. No pressure is generated on.

When pressure oil is supplied to one of the head side oil chambers of the left and right angle cylinders by operating the angle hydraulic switching valve, the angle cylinder on that side expands and the operating pressure causes the heads of other angle cylinders to expand. Since the pilot check valve provided in the oil passage leading to the side oil chamber is opened, this angle cylinder can be freely shrunk. When the angle hydraulic switching valve is in the neutral position, if one of the angle cylinders tries to contract due to the external force applied to the blade, the pressure in the head side oil chamber rises, but the pilot check valve causes the oil passage Since the flow is blocked, the blade opposes the external force and the pressure in the oil passage downstream of the pilot check valve does not rise.

When the tilt hydraulic pressure switching valve is switched and pressure oil is supplied to the head side or rod side oil chamber of the tilt cylinder, the pilot check valve provided in the oil passage communicating with the oil chamber on the opposite side is opened, so the tilt cylinder does not interfere. Although the blade expands and contracts and the blade tries to tilt, the load is generated in the angle cylinder because the hydraulic switching valve for the angle is not operated. Correspondingly, the oil passage leading to the working oil chamber of the tilt cylinder is branched to the pilot oil chamber of the pilot check valve provided in the oil passage leading to the head-side oil chamber of the angle cylinder on the side that must contract. Since the valves are communicated with each other through the valve, expansion and contraction of the tilt cylinder is not hindered even if the angle hydraulic switching valve is not operated. When the tilt hydraulic switching valve is in the neutral position, even if external pressure is applied to the tilt cylinder and the pressure rises, the pilot check valve closes the high pressure side oil passage, so No high pressure is generated at
The swivel joint is protected.

Embodiment An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, in which 1 is a hydraulic pump for operating the dozer device D, 55
Holds the pressure oil supplied through the lift cylinders 6 and 6 for operating the dozer 9, the angle cylinders 7 and 7 ', the hydraulic switching valves 2 and 3 and 4 for expanding and contracting the tilt cylinder 8 and the oil passage 23 at a specified value. It is a hydraulic switching valve group including a relief valve 5. The ports of the hydraulic pressure switching valves 2, 3 and 4 are respectively connected to the oil passage 2
6, 27, 28, 29, 30, 31 and the swivel joint 64 and communicates with the working-side oil chamber of each hydraulic cylinder. The dozer is provided in the middle of the oil passages 26, 28, 29, 30, 31. When actuating 9, the throttle check valves 10, 11, 12 are used to prevent the hydraulic cylinder from expanding and contracting more rapidly than necessary and to facilitate fine control.
Nos. 13 and 14 are provided, and a pilot check valve 17 is provided between the lift cylinder 6 rod-side oil chamber to which the own weight of the blade 9 is applied and the throttle check valve 10.
The pilot oil chamber of the pilot check valve 17 communicates with the oil passage 27 through the pilot oil passage, and the pilot oil chamber is connected between the head-side oil chambers of the angle cylinders 7 and 7'and the throttle check valves 11 and 12, respectively. Check valves 18 and 19 are provided, and the pilot oil chamber of the pilot check valve 18 is operated by the oil passage 29 and the tilt cylinder 8 via the shuttle valve 16 so that the angle cylinder 7 is forcibly contracted. An oil passage communicating with the chamber, for example, an oil passage 31 is communicated with the pilot oil chamber of the pilot check valve 19 via the shuttle valve 15 in the same manner as above.
A pilot check valve 20 in communication with the oil passages 28 and 30 is provided between the head-side oil chamber of the tilt cylinder 8 and the throttle check valve 13, and a pilot oil chamber is in communication with the oil passage 31. A pilot check valve 21 is provided between the chamber and the throttle check valve 14, and the pilot oil chamber communicates with the oil passage 30.

The working oil chamber of the angle cylinders 7 and 7'is only on the head side. However, since a general-purpose double-acting hydraulic cylinder is generally used, the rod-side oil chamber has the oil passage 25 and the swivel joint 64. After that, it is communicated with the tank 22. The hydraulic switching valve 3 is an angle cylinder 7 or 7 '.
In order to prevent the head cylinder from being forcibly expanded with the expansion and contraction of the tilt cylinder 8 to form a gap in the head side oil chamber, a center open type is used and the head side oil chamber and the tank 22 are connected by an oil passage.

The operation of the blade 9 in the above hydraulic circuit will be described.

When the hydraulic pressure switching valve 2 is switched to the A position, the pressure oil of the hydraulic pump 1 flows through the oil passage 23, the A position passage of the hydraulic switching valve 2, the oil passage 26,
At the same time as passing through the swivel joint 64, the check valve of the throttle check valve 10 and the pilot check valve 17 into the rod side oil chamber of the lift cylinders 6 and 6 to contract the lift cylinders 6 and 6 and raise the blade 9,
Return oil in the head-side oil chamber passes through the oil passage 27, the swivel joint 64, the A position passage of the hydraulic switching valve 2, the oil passage 24, and returns to the tank 22. When the hydraulic pressure switching valve 2 is set to the B position, the flow of pressure oil goes down the dozer 9 through the route opposite to the above.
Since the pilot check valve 17 does not open unless the pressure in the oil passage 27 rises, the lift cylinder 6 does not extend in advance due to the weight of the blade 9, and the return oil from the head side oil chamber is not returned to the throttle check valve 10. Since it passes through the narrowed portion, no sudden extension occurs. When the hydraulic pressure switching valve 2 is in the C position, the pressure in the oil passage 27 is reduced, so the pilot check valve 17 is closed to prevent the lift cylinder from naturally descending and reducing due to external force.

When the hydraulic pressure switching valve 3 is set to the A position, the pressure oil passes through the oil passage 28, the swivel joint 64, the throttle check valve 11 and the pilot check valve 18 and flows into the head side oil chamber of the angle cylinder 7 to extend the angle cylinder 7. Then, the left end of the blade 9 is pushed forward and the reaction force tries to contract the angle cylinder 7 ', so that the pressures in the oil passage 28 and the branched pilot oil passage also rise and the shuttle valve 15
Since it reaches the pilot oil chamber of the pilot check valve 19 via the, the pilot check valve 19 is opened, and the return oil from the head side oil chamber of the angle cylinder 7'is returned to the oil passage 29,
It flows into the tank 22 through the throttle portion of the throttle check valve 12, the swivel joint 64, the A position passage of the hydraulic pressure switching valve 3, and the oil passage 24. When the hydraulic pressure switching valve 3 is set to the B position,
The flow reverse to the above, the angle cylinder 7'expands and the contracts 7, and the return oil returns to the throttle check valve because the pressure oil in the oil passage 29 acts through the shuttle valve 16 to open the pilot check valve 18. It passes through the squeezing part of 11.
When the hydraulic pressure switching valve 3 is in the C position, the oil passages 28 and 29 both become the pressure of the tank 22, so the pilot check valve 1
8 and 19 are closed to maintain the grade 9 position, and even if an external force is applied, no pressure is generated in the oil passages 28 and 29 on the downstream side of the pilot check valves 18 and 19.

When the hydraulic switching valve 4 is set to the A position, the pressure oil flows into the head side oil chamber of the tilt cylinder 8 through the oil passage 30, the throttle check valve 13 and the pilot check valve 20, and the branch oil passage of the oil passage 30 is pilot checked. Since the pilot check valve 21 acts on the pilot oil chamber of the valve 21, the tilt cylinder 8 extends, the blade 9 is tilted, and the return oil of the rod side oil chamber of the tilt cylinder 8 is returned to the pilot check valve 21 and the oil. It returns to the tank 22 through the passage 31, the throttle portion of the throttle check valve 14, the swivel joint 64, the A position passage of the hydraulic pressure switching valve 4, and the oil passage 24.
With the extension of the tilt cylinder 8, the angle cylinder 7 ′ is slightly contracted due to the structural link motion of the dozer device D, and 7 is extended, but the oil passage 30 is branched to the pilot oil chamber of the pilot check valve 19. Since the pilot oil passage communicates with the oil passage and the shuttle valve 15, the angle cylinder 7'reduces without any obstruction, and the oil passage 28 communicates with the oil passages 29 and 24 at the C position of the hydraulic switching valve 3. Even if the angle cylinder 7 is forcibly extended, the oil supply is complete. When the hydraulic pressure switching valve 4 is set to the B position, the flow directions of the pressure oil and the return oil are completely opposite, and the tilt cylinder 8 is contracted. Further, when the hydraulic pressure switching valve 4 is in the C position, as in the case where the other hydraulic pressure switching valves are in the C position, the pilot check valve 2
Even if an external force acts on the blade 9 due to the action of 0 or 21, the throttle check valves 13 and 14, no high pressure is generated in the oil passage 30 or 31 downstream of the pilot check valves 20 and 21, and the operation is smooth. .

Effect of the Invention In the hydraulic circuit according to the present invention, when the tilt cylinder is expanded and contracted, the structure of the dozer device allows the angle cylinder, which is unavoidably caused by link motion, to expand and contract, so the link mechanism, hydraulic cylinder, blade, etc. Does not require an extra load, does not require extra capacity, and when the operating hydraulic switching valve of each cylinder is in the neutral position,
Even if an external force is applied to the blade and the hydraulic oil chamber becomes high in pressure, high pressure oil is blocked by the pilot check valve provided in the oil passage, so high pressure does not occur in the oil passage downstream from the pilot check valve. Protect the swivel joint,
At the same time, it has a large blade position holding ability.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of this invention, FIG. 2, FIG. 3, FIG.
The drawings are side views, plan views, front views, FIG. 5 and FIG. 6 of the crawler type hydraulic excavator equipped with a dozer device, respectively, from the appearance, and FIG. FIG. 7 is a side view showing a tilt cylinder operating mechanism, FIG. 7 is a side view showing details of a tilt cylinder mounting portion, and FIG. 9 is a sectional view showing an example of a ball joint. FIG. 10 is a hydraulic circuit diagram showing an embodiment of the prior art. 6 ... Lift cylinder 7, 7 '... Angle cylinder 8 ... Tilt cylinder 32 ... Dozer frame 33 ... Turnbuckle 55 ... Hydraulic switching valve group 60 ... Upper revolving structure 63 ... Lower traveling frame 64 ... Swivel joint

Claims (1)

[Scope of utility model registration request] 1. A hydraulic operating circuit for supplying pressure oil from a hydraulic switching valve to a lift cylinder, an angle cylinder and a tilt cylinder via a swivel joint to operate a dozer device in front of a traveling frame, a hydraulic chamber for a blade rising side,
Angle cylinder and tilt cylinder A pilot check valve that forms a free passage toward the working oil chamber is provided in the middle of the oil passage, and the pilot check valve in the lift cylinder blade rising side oil passage becomes the blade lowering side oil chamber. In the oil passage communicating with the oil passage of the two angle cylinders, the pilot check valve provided in the oil passages of the two angle cylinders is connected to the oil passage of the angle cylinder on the other side via the shuttle valve, and the tilt cylinder is operated. Pilot oil chamber of the pilot check valve of the oil passage leading to each hydraulic oil chamber of the tilt cylinder and the oil passage on the side that forcibly reduces each angle cylinder due to the operation of the oil passage leading to the oil chamber Is connected to the oil passage that communicates with the hydraulic oil chamber on the other side. Hydraulic control circuit equipped with dozer device blade.