JPH0320369Y2 - - Google Patents

Description

[Detailed description of the invention] This invention raises and lowers the bucket which is pivotally supported at the tip of the lift arm by moving the lift arm up and down using a lift cylinder arranged between the aircraft body and the lift arm. The present invention relates to a bucket actuator for raising, lowering, and rotating the bucket in a front loader or the like that is rotated by a tilt cylinder disposed between the buckets.

This type of bucket actuator is configured with a control valve that switches and controls the supply and discharge of hydraulic pressure to the lift cylinder and another control valve that switches and controls the supply and discharge of hydraulic pressure to the tilt cylinder. In addition to the above-mentioned control valves, it was equipped with a parallel link mechanism for raising and lowering the bucket in a constant position. In other words, when raising and lowering a bucket containing earth, sand, compost, etc., if the bucket is not raised and lowered in parallel, the bucket posture will tilt as it goes up and down, and the earth, sand, compost, etc. will fall out of the bucket. A parallel link mechanism is created by rotatably supporting a bracket that pivots on the lift arm, and providing a rod or plate piece with both ends pivotally connected to the bracket and another bracket on the fuselage that pivots the lift arm. When the lift cylinder is actuated and the lift arm is rotated up and down, the relative attitude of the tilt cylinder to the lift arm is changed by the parallel link mechanism, and conversely, the relative attitude of the bucket to the lift arm is changed. It was designed to maintain a constant level.

By the way, the above-mentioned parallel link mechanism not only spoils the appearance of the front loader etc., but also has to be designed to be strong because it is exposed to the load of turning back. This is also the part that breaks most quickly in front loaders and the like.

The purpose of this invention is to maintain a constant posture of the bucket cart when raising and lowering it using a hydraulic circuit structure instead of using a parallel link mechanism as in the past, and to eliminate the above-mentioned problems. Another object of the present invention is to provide a new bucket actuating device for a front loader, etc., which is designed to simplify the structure of a valve provided in a hydraulic circuit as much as possible.

Regarding the illustrated embodiment, the structure of the bucket actuator according to the present invention will be explained. The first embodiment illustrated in FIGS. - This invention relates to an example in which this invention is implemented in a front loader equipped with a loader mechanism. As shown in Figures 1 and 2, a lift arm 4 is provided with its base end pivoted 3 on a pair of left and right brackets 2 fixed to both sides of the machine body 1, and a bucket 5 is attached to the left and right arms. - The lift arm 4 is provided with a pivot 6 at the tip of the lift arm 4, which is formed by appropriately fixedly connecting the arms. The lift cylinder 7 has its cylinder end pivoted 8 on the bracket 2 described above, and its piston rod end pivoted 9 on the middle of the lift arm 4.
There are one pair on the left and right. lift arm 4
A pair of left and right brackets 10 are fixed 11 and erected in the middle of the lift arm 4, and a pair of left and right rotating plates 12 are pivotally mounted 13 near the tip of the lift arm 4. The tilt cylinders 14 are provided in left and right pairs, with cylinder ends pivoted 15 on the bracket 10 described above and piston rod ends pivoted 16 on the rotation plate 12 described above. The rotating plate 12 described above
11 pairs of left and right operating punches 17 are pivotally connected to the bucket 5 at both ends, and in the case shown, the basket 5 is moved by a tilt cylinder 14,
2 and an operating punch 17.

A bulk device 18, which is also shown in a circuit diagram in FIG. 3, is provided on the tractor body 1. This valve device 18 includes a first control valve 19 that switches and controls supply and discharge of hydraulic pressure to both lift cylinders 7 and a second control valve 20 that switches and controls supply and discharge of hydraulic pressure to both tilt cylinders 14. ing. In Figure 3, 21
2 is an oil tank, 22 is a hydraulic pump, and the first control valve 19 blocks the ends of circuits 23 and 24 connected to both oil chambers 7a and 7b of the lift cylinder 7, respectively, as shown in the figure. 7 and the circuit 23 connected to the extension oil chamber 7a to the hydraulic pump 22,
In addition, the circuit 24 connected to the reduction oil chamber 7b is connected to the oil tank 21, and the lift cylinder 7 is extended at the lifting operation position U, and the circuit 24 is connected to the hydraulic pump 22, and the circuit 23 is connected to the oil tank 21. A lowering action position D, which is connected to the tank 21 and causes the lift cylinder 7 to perform a contraction operation, and both circuits 2
3 and 24 are both connected to the oil tank 21, the lift cylinder 7 is deactivated, and the lift arm 4 is placed in a floating state. On the other hand, the second control valve 20
are both oil chambers 14a and 14b of the tilt cylinder 14.
A neutral position N where the tilt cylinder 14 is stopped by blocking the ends of the circuits 25 and 26 connected to each other.
and the circuit 25 connected to the contraction oil chamber 14b to the hydraulic pump 22, the circuit 26 connected to the expansion oil chamber 14a to the oil tank 21, and the circuit 26 connected to the oil tank 21, respectively. It has a tilt action position 1 where the tilt cylinder 7 is connected to perform a contracting operation, and a dump action position where the circuit 26 described above is connected to the circuit 25 and the hydraulic pump 22 and the tilt cylinder 14 is extended. By connecting the circuits 25 and 26 at the dump action position where the tilt cylinder 14 is to be extended as described above, both oil chambers 1 of the cylinder 14 are connected.
The reason why it was decided to connect between 4a and 14b is as follows. That is, the piston 14 facing the extension oil chamber 14a in the tilt cylinder 14
The pressure receiving area of piston _14c facing the reduction oil chamber 14b is
From the above area S ₁ , the cross-sectional area S ₀ of the piston rod 14d
_The area S ₁ - _{S 0} is obtained by subtracting
The oil in b flows through the circuit 25, the control valve 20, and the circuit 26 to the extension oil chamber 14a, so that the tilt cylinder 14 can quickly extend and the cylinder 4 can perform a quick dump operation. This is what we are trying to achieve. In addition, in the illustrated valve device 18, each control valve 1
9, 20 are additionally provided with pump ports P ₁ , P ₂ and outlet ports A ₁ , A ₂ for one control valve, the first control valve 19 is placed in the neutral position N or the floating position F, and the second control valve 19 is placed in the neutral position N or floating position F. control valve 20
The control valves 19 and 20 are configured so that hydraulic pressure can be taken out to a carry over port 27 provided in the valve device 18 when the control valve is placed in the neutral position N, and the oil pressure taken out from this carry over port 27 can be used to It is designed to be able to operate the hydraulic equipment 28 of. Relief of overload relief valves 29, 30 provided in connection with circuits 23, 26 connected to tank ports on the primary side of each control valve 19, 20 and expansion oil chambers 7a, 14a of each cylinder 7, 14. The port is connected to the carry over port 27, and the tank port and relief port are connected to the oil tank 21 via the carry over port 27 and a control valve 31 for other hydraulic equipment 28. There is. In FIG. 3, 32 is a pressure regulating valve that sets the oil pressure applied to each cylinder 7, 14 and other hydraulic equipment 28, and 33 is a surface passage 25 connected to the reduction oil chamber 14b of the tilt cylinder 14.
The counterbalance valve inserted inside is exposed.

The oil supply circuit led from the discharge port of the hydraulic pump 22 is guided to the primary side of the first control valve 19 by the oil supply circuit 34 and to the primary side of the second control valve 20 by the oil supply circuit 35. These oil supply circuits 34, 35
There are load check valves 42 and 43 that allow oil flow only in the direction of each control valve 19 and 20.
are inserted, and in the case shown, the above-mentioned additional ports of each control valve 19, 20 are inserted.
Carry over port 2 via P ₁ , A ₁ , P ₂ , A ₂
7 is provided in parallel with both the above-mentioned oil supply circuits 34 and 35, but in order to distribute and control the amount of oil supplied to the primary sides of both control valves 19 and 20, the following A flow rate regulating valve 37 is provided.

That is, first, the second control valve 20
The oil supply circuit 35 connected to the primary side of the pump 22 side has a first circuit 35A and a second circuit 35B connected in parallel. The above-described flow rate regulating valve 37 includes a throttle 38 inserted into the oil supply circuit 34 and a first control orifice connected in parallel by being inserted into the first circuit 35A and the second circuit 35B, respectively. 39A and second control orifice 39B
and a pressure compensating valve 40 inserted across both oil supply circuits 34, 35, are combined to form a constant ratio flow dividing valve. And the above-mentioned first control orifice 39A and second control orifice 39B.
Of these, only the second control orifice 39B is
The second control valve 20 is configured to selectively act on the second control valve 20 as follows.

That is, as similarly shown in FIG.
Of the circuits 35A and 35B, the second circuit 35B
is particularly provided to pass through the second control valve 20, and the second control valve 20
As shown in the figure, the second circuit 35 is in the dump action position where the tilt cylinder 14 is extended.
In the tilt action position where B is blocked and the tilt cylinder 14 is compressed, the second circuit 35
The valve is configured to release the block of B. Therefore, when the second control valve 20 is placed in the dumping position, the second circuit 35B is blocked and the flow to the second control valve 20 is only through the first control orifice 39A in the first circuit 35A. When refueling is performed and the second control valve 20 is placed in the tilting position I, the second circuit 35B is unblocked and the first control orifice 39A and the second control orifice 3 are unblocked.
Oil is supplied toward the second control valve 20 via 9B.

Considering the hydraulic circuit structure as described above, if the first control valve 19 is placed in the lifting position U and the second control valve 20 is placed in the dumping position, the lift cylinder 7 will extend and move the bucket 5. is raised, the tilt cylinder 14 is extended and the bucket 5 is rotated for dumping, and at this time, the first control orifice 39A is
The first control valve 19 is placed in the lowering position D and the second control valve 20 is placed in the tilting position I.
If it is set at
for the first and second control orifices 39
While oil is supplied through the valves A and 39B, the flow rate regulating valve 37 distributes and controls the amount of oil supplied to the primary sides of the first and second control valves 19 and 20 as follows.

In other words, when lifting and lowering the bucket 5 by rotating the lift arm 4 using the lift cylinder 7, for example, when lifting the bucket 5 from the position indicated by the two-dot chain line in FIG.
Assuming that the tilt cylinder 14 is not operated at all, as the lift arm 4 rotates upward, the attitude of the bracket 10 on the lift arm 4 is changed so that its upper end side is displaced rearward, so that the tilt cylinder 14 is moved. 14 is pulled in the proximal direction,
As a result, the bucket cart 5 is rotated in the tilt rotation direction via the rotating plate 12 and the operating rod 17, and the relative posture of the bucket cart 5 with respect to the lift arm 4 gradually changes as shown by the dashed line in FIG. The posture becomes tilted in the direction of movement. Conversely, when the lift cylinder 7 rotates the lift arm 4 downward to lower the bucket cart 5, the relative posture of the bucket cart 5 with respect to the lift arm 4 gradually becomes inclined toward the dump rotation direction. On the other hand, when both the control valves 19 and 20 are at the operating positions U, D, and I and the cylinders 7 and 14 are simultaneously expanded and contracted, the flow rate adjustment valve 37 causes the upward movement of the bucket 5 and the dump rotation. While movement or downward movement and rotation can be obtained at the same time, when both cylinders 7 and 14 can be simultaneously obtained in this way, when both cylinders 7 and 14 can be extended and contracted at the same time, the bucket 5 When rising, the bucket 5 is connected to the first control orifice 39A.
The dump is rotated by the tilt cylinder 14, which is supplied with hydraulic oil to the extension oil chamber 14a through the chisel, and the bucket 5 is supplied to the contraction oil chamber 14 through the first and second control orifices 39A, 39B.
The amount of oil supplied to the primary side of each control valve 19, 20 is distributed and controlled so that the bucket 5 is tilted and rotated by the tilt cylinder 14 supplied with hydraulic oil to b, and is raised and lowered while maintaining a substantially constant posture. It is composed of what it does. More specifically, as described above, the second control valve 20 connects the circuits 25 and 26 at its dumping position, and the tilt cylinder 1
The first control valve 19 is moved to the upward action position U, and the first control valve 19 is moved to the upward action position U, and the first control valve 19 is moved to the upward action position U. 2
When moving the control valve 20 to the dumping position to raise the bucket 5, a value commensurate with the supply ratio of hydraulic oil supplied from the contraction oil chamber 14b to the extension oil chamber 14a of the tilt cylinder 14, In order to reduce the supply rate of the hydraulic oil supplied from the hydraulic pump 22 to the extension oil chamber 14a and to rotate the dump truck at a speed commensurate with the lifting speed of the bucket truck 5, the first control orifice is installed when the bucket truck 5 is raised. 35A is intended to act, so that the posture of the bucket cart 5 is maintained substantially constant both when the bucket cart 5 is raised and when it is lowered.

Next, the specific structure of the valve device 18 will be explained in the fourth section.
This will be explained with reference to FIG.

The valve case of the valve device is provided with a pump port 41P opened on the bottom side and a carry over port 27 opened on the top side, as shown in FIGS. 5 and 6, and as shown in FIG. 4. The cylinder port 41 is connected to the extension oil chamber 7a and the contraction oil chamber 7b of the lift cylinder 7.
Cylinder ports 41 and 41 that are connected to the contraction oil chamber 14b and the expansion oil chamber 14a of the tilt cylinder 14 are respectively opened to the side surface. Inside the valve case are a spool 19S constituting the first control valve 19 and a second control valve 2.
The spool 20S constituting 0 and the spool 19
The spool 20S is placed on the lower side, and the spool 20S is placed on the upper side, so that they are parallel to each other.

As shown in FIG. 5-8, the valve case has a hole 45 that communicates with the pump port 41P and extends in a direction transverse to the port 41P, and a hole 45 that is located at the same level as the hole 45 and parallel to the hole 45. A valve installation hole 46 is formed through the valve case. The aperture 38 mentioned above is the hole 4
5 from one end side and screwed onto the valve case.
Each of the second control orifices 39B includes two small holes formed in an orifice-forming metal fitting 48 that fits into the hole 45 from the other end and is screwed onto the valve case. Inside the valve installation hole 46, the pressure compensating valve 40 described above is biased to move in one direction and the other direction by a pair of springs 40a and 40b whose base ends are received by plugs screwed onto both ends of the valve installation hole 46. and it is mated. At one end of this pressure compensating valve 40, the secondary side of the throttle 38 is connected to an oil passage 4.
9, and the other end is connected to the secondary side of the first control orifice 39A through an oil passage 50. A suitable number of small holes 40c and 40d are formed in the pressure compensating valve 40 at appropriate intervals in the axial direction, and the open end of the small hole 40c on the outer peripheral side is connected to an oil passage 51, as clearly shown in FIG. 52, 53
is connected to the front surface of the load check valve 42. The oil passage 53 is opened by the force of the spring 42a.
As shown in FIG. 9, on the secondary side of the load check valve 42, which is configured as a poppet with a blocked end, there is a pair of oil passages that open at appropriate intervals in the axial direction on the circumferential surface of the spool 19S. 54P _1,5
4P ₂ is provided, and the ends of the oil passages 54P ₁ and 54P ₂ are configured as pump ports of the first control valve 19. On the other hand, the outer opening end of the other small hole 40d of the pressure compensation valve 40 is connected to the front surface of the load check valve 43 through oil passages 55, 56, 57 shown in FIGS. 5-8. As shown in FIG. 10, there is a spool 20S on the secondary side of the load check valve 43, which is configured as a poppet that blocks the end of the oil passage 57 by the force of a spring 43a.
A pair of oil passages 58P 1 and 58P 2 are provided on the circumferential surface of the oil passages 58P ₁ and 58P ₂ which are opened at appropriate intervals in the axial direction.
The ends of the oil passages 58P ₁ and 58P ₂ are configured as pump ports of the second control valve 20.

In order to connect the secondary side to the second control orifice 89B formed in the orifice forming metal fitting 48 in the direction of the control valve 20, the valve case has an orifice forming metal fitting 4 as shown in FIGS. 6-10.
8 and an oil passage 59 located on the outer periphery of the oil passage 59.
An oil passage 60 is formed that continues upward from the end, and the end of the oil passage 60 is opened to a slot 61 at the outer circumferential position of the spool 20S, as shown in FIG. Another slot 62 is formed adjacent to the slot 61 at the outer circumferential position of the spool 20S.
As shown in FIG. 10, an oil passage 63 is provided in the valve case that is connected to the slot 62 and extends downward. It communicates with the oil passage 50 located on the secondary side of the control orifice 39A. As shown in FIG. 10, when the second spool 20S is pushed in from the neutral position N shown in the figure by an appropriate amount, it is moved to the tilt action position, and when it is pulled out an appropriate amount, it is moved to the dump action position. However, the spool 20S has the above-mentioned slot 6.
Two lands 20 are arranged at the formation positions 1 and 62.
a and 20b are provided. The oil passage 57 described above passes through the outer periphery of the spool 20S on the side opposite to the groove 62 across the slot 61, but the lands 20a, 20b are located at any position N, on the spool 20. , the groove hole 61 and the oil passage 5
7 is cut off by the land 20a, and the slots 61 and 6 are cut off between the neutral position N and the dump action position.
2 is cut off by the land 20b, and in the tilt action position, it is cut off by the lands 20a, 20b, and in the tilt action position, the land 20a, 20b
The grooves 61 and 62 are arranged so as to communicate with each other at the outer periphery of the small diameter portion between them. Therefore, only when the spool 20S is moved to the tilting position, the oil passages 60 and 63 are communicated with each other, and in this case, the oil passages 60, 61, 62, and 63 are connected from the second control orifice 39B. aisle 63
The oil flows into the oil passage 50 through the oil passage 50, where it joins with the oil from the first control orifice 39A.

The neutral circuit 36 described above with reference to FIG.
The spool 1 extends upwardly from the hole 45 across the hole 45.
Oil passage 6 whose tip is open to the outer circumference of 9S
5, the oil passage 57, and an oil passage 66 that connects the outer circumference of the spool 20S to the carry over port 27. As shown in FIG. 9, when the spool 19S of the first control valve 19 is pushed in a certain amount from the neutral position N shown in the figure, it is moved to the upward action position U, and when it is pulled out a certain amount, it is moved to the downward action position D. When the spool 19S is moved to the floating position F and further pulled out by a certain amount, the spool 19S is moved to the floating position F.
7 and at other positions U, D, F, the oil passage 6
Lands 19a and 19b are provided to cut off the space between 5 and 57. On the other hand, the second control valve 20
The spool 20S is provided with another land 20c adjacent to the land 20a, and at the neutral position N of the spool 20S, an oil passage 5 is formed between the lands 20a and 20c.
The oil passages 57 and 66 communicate with each other, but the land 20a or 20c is designed to block the oil passages 57 and 66 in the tilt position and dump position. From the above, when moving the first control valve 19 or its spool 19S from the neutral position N to the second control valve 20 or its spool 20S to any operating position, the oil passage 56 to the oil passage 57 When the oil flowing into the oil passage 57 joins the oil flowing into the oil passage 57 from the oil passage 65 and the second control valve 20 is operated independently, the oil supply ratio to the tilt cylinder 14 is increased, and the oil flowing into the tilt cylinder 14 is increased. Rapid expansion and contraction of the cylinder 14 is to be achieved.

As shown in FIG. 9, the cylinder port 41
U and 41D are connected to the outer circumference of the spool 19S by oil passages 67U and 67D, and as shown in FIG.
are connected to the outer circumference of the spool 20S by oil passages 68, 68. As shown in FIG. 6, oil passages 69, 70 connect the outer peripheries of both ends of the spools 9S, 20S to the carry over port 27.
is provided in the valve case. The spool 19S of the first control valve 19 is provided with an appropriate number of lands in addition to the lands _19a and 19b.
The ends of P ₂ , 67U, 67D, 69, and 70 are blocked, and the oil passages 54P ₁ and 67 are at the lifting action position U.
U and the oil passages 67D and 70 are communicated with each other, and the ends of the oil passages 54P ₂ and 69 are blocked, and at the lowering position D, the oil passages 54P ₂ and
67D and the oil passages 67U, 69 are communicated with each other, and the ends of the oil passages _54P1 , 70 are blocked, and in the floating position F, the oil passages 67U, 69 are communicated with the oil passages 67D, 70, respectively. oil passages 54P ₁ , 5
4P It is arranged so that _{the two} ends are blocked. Also, the lands 20a, 20b, 20 are attached to the spool 20S of the second control valve 20.
In addition to c, an appropriate number of lands are installed in the oil passages 48P ₁ , 48P ₂ , 68, 68 at the neutral position N shown in the figure.
, 69, 70 ends are blocked, and in the tilting position, between the oil passages 58P ₁ and 68 and the oil passage 68
, 70 are communicated with each other, and the ends of the oil passages 58P ₂ and 69 are blocked, and in the dump operation position, the oil passages 58P ₂ and 68 are communicated with the oil passages 68 and 58P ₁ , respectively, and the oil passages 69 and 69 are communicated with each other. , 70 are arranged so that their ends are blocked. At the dumping position of the spool 20S, the oil passages 68, 5
By communicating between 8P _{and 1} , the oil returned from the reduction oil chamber 14b of the tilt cylinder 14 to the cylinder port 41 flows through the oil passages 68 and 5.
Cylinder port 4 via 8P ₁ , 58P ₂ , 68
1 and flows into the extension oil chamber 14 of the tilt cylinder 14 as described above together with the oil from the hydraulic pump 22.
supplied to a.

Of the overload relief valves 29 and 30 described above with reference to FIG.
9 is disposed between the oil passages 67U and 69 as shown in FIG.
0 is disposed between oil passages 68 and 70 as shown in FIG.

As shown in FIG. 3, the counterbalance valve 33 is connected to the tilt cylinder 14 when the second control valve 20 is moved to the tilt operating position I.
A check valve 71 that allows oil to be supplied to the reduction oil chamber 14b of the tilt cylinder 14 is set to the reduction oil chamber 14b of the tilt cylinder 14 by a relief operation when the second control valve 20 is moved to the dump operation position. A relief valve 72 that applies a back pressure is connected in parallel with each other, and a large load from the bucket 5 and the earth and sand contained therein acts on the bucket 5 in the direction of dump rotation. On the other hand, when the second control valve 20 is moved to the dump action position, the tilt cylinder 14 is moved to the extension action oil chamber 1 due to the above-mentioned large load.
The back pressure established by the relief valve 72 prevents the extension operation at a speed higher than the oil supply rate to 4a. In the illustrated case, the counterbalance valve 33 is constructed as an in-line valve having joint portions at both ends in the axial direction, as shown in FIG. 10.
That is, the check valve 71 having a substantially cylindrical shape is provided in the cylindrical valve case 33a and is biased to move in the direction opposite to the cylinder port 41I by a valve spring 71a.
When the oil passage 58P1 and the cylinder port 41I are slightly displaced in the direction, the oil passage _58P1 and the cylinder port 41I are brought into communication through the groove 71b on the outer peripheral surface. The relief valve 72 is placed inside such a check valve 71,
The valve spring 72a moves toward the cylinder port 41I whose displacement is regulated by the regulating portion 71c of the check valve 71.
The relief valve 72 is provided with a relief oil passage 72b which is normally blocked between the check valve 71 and the inner peripheral surface of the check valve 71. The relief valve 72 is lowered by a slight amount within the check valve 71 whose lowering is prevented by the stepped portion 33a' on the inner peripheral surface of the check valve 33a, and performs a relief operation via the oil passage 71b. The counterbalance valve 33 configured as an in-line valve in this way
can also be used by being attached to the tilt cylinder 14 instead of the valve device 18 as shown.

In FIGS. 6 and 9, 73 is a spring mechanism for automatically returning the spool 19S from each operating position U, D to the neutral position N by releasing the operating force.
A detent means 74 is provided for restraining the body at the floating position F. 6 and 10, 75 indicates the spool 20S at each operating position I,
This is a spring mechanism for automatically returning to the neutral position N when the operating force is released.

The bucket actuator shown in FIGS. 1-10 is configured as described above, and is connected to the base end side of the oil supply circuit 35 that supplies oil to the primary side of the second control bubble 20. The first control orifice 39A and the second control orifice 39B are respectively inserted into the first circuit 35A and the second circuit 35B, which are connected in parallel with each other and which constitute a part of the circuit. The second control orifice 39B can be activated only in the tilting position of the second control valve 20, whereas the second control orifice 39A can be activated in either of the working positions of the second control valve 20. Specifically, as described above, the slots 61 and 62 shown in FIGS. 6 and 10 are brought into communication only when the spool 20S is moved to the tilting position, and the second control orifice shown in FIG. A radial outward flow of oil occurs through 39B, which causes oil flow within oil passageway 50 through first control orifice 39A.
It merges with the oil flow through. Moreover, when an imbalance of oil pressure occurs between the oil passage 49 side and the oil passage 50 side shown in FIG. 7, the pressure compensating valve 40 shown in FIGS. Displaced in the direction, the small hole 4 described above
The opening area of 0c to the oil passage 51 and the opening area of the small hole 40d to the oil passage 55 are changed and controlled in a related manner, and the oil supply circuit 35 and the oil supply circuit 36 shown in FIG.
The flow rate ratio of oil distributed between the two is controlled to be constant at a set value. The flow rate regulating valve 37 distributes and controls the amount of oil supplied to the primary side of each control valve 19, 20 as described above.

Therefore, for example, when the bucket 5 containing earth and sand or fertilizer is raised from a horizontal position on the ground as shown by the two-dot chain line in FIG. 2, by extending the lift cylinder 7, the first control valve If the bucket 5 is raised by moving the second control valve 20 to the dumping position at the same time that the bucket 19 is moved to the raising position U, the bucket 5 supplies hydraulic oil only through the first control orifice 39A. As the dump truck 5 is gradually rotated and raised by the tilt cylinder 14, the bucket truck 5 is raised while maintaining a substantially horizontal position, as shown by the solid line in FIG. No soil or fertilizer will spill out. On the other hand, when lowering the bucket 5 in a horizontal position that accommodates soil or fertilizer, the first
If the second control valve 20 is moved to the tilting position at the same time as the control valve 19 of The tilt cylinder 14 supplied with water is tilted relatively quickly but gradually and lowered, thereby maintaining an almost horizontal attitude and lowering the earth and sand. spillage is prevented. The pressure compensating valve 40 is operated by a pressure difference between the hydraulic pressures acting on both ends of the valve 36 when the load acting on the cylinders 7 and 14 changes or the rotation speed of the hydraulic pump 22 changes. By displacing along the axial direction as described above, the above-mentioned load fluctuations and rotational fluctuations are compensated for, and the ratio of flow rates distributed to both cylinders 7 and 14 is kept constant.

In the illustrated case, since the flow rate adjustment valve 37 and the load check valves 42 and 43 are provided in parallel with the neutral circuit 36, the control valve 1
9 and 20 are both in the neutral position and the hydraulic pressure is extracted from the neutral circuit 36 via the carry over port 27 to operate the other hydraulic equipment 28, the flow rate adjustment valve 3
7 and load check valves 42 and 43, the oil pressure does not drop and there is no oil pressure loss.

Next, the embodiment of FIG. 2 shown in FIG. 11 will be described. In this second embodiment, a valve device 18' having the structure of other parts is completely the same as the valve device 18 in the first embodiment. In this case, instead of the above-described constant ratio flow control valve type flow control valve 37, a constant flow rate control valve 37' is used, that is, the same oil supply circuit 34 as described above has a structure similar to that of a normal relief valve. Flow control valve (bypass type diverter valve) 8
0, and first and second control orifices 39 similar to those described above are provided in the first and second circuits 35A and 35B constituting the front-stage portion of the same oil supply circuit 35 as described above.
A, 39B are inserted, respectively, and a flow rate regulating valve 37' is provided in which the hydraulic pressure of the oil supply circuit 35 on the secondary side of the control orifices 39A, 39B acts on the flow rate control valve 80 as back pressure. and the second
The control valve 20 is constructed in exactly the same manner as described above, and in its dumping position it blocks the second circuit 35B and
In this embodiment, only the control orifice 39A is operated, and at the tilt operation position 1, the second circuit 35B is unblocked so that the first control orifice 39A and the second control orifice 39B are operated together. The flow rate adjustment valve 37' is configured to perform the same oil supply amount distribution control as described for the flow rate adjustment valve 37 in the previous embodiment.

The effect obtained by the second embodiment shown in FIG. 11 is also the same as that described for the first embodiment. In the second embodiment, since the constant volume type flow regulating valve 37' is used, the flow rate ratio with respect to the volume cylinders 7 and 14 is extremely stable at a desired constant value in the actual use range.

As is clear from the description of the embodiments above, the bucket actuator for a front loader or the like according to the present invention has a bucket 5 which is pivotally supported at the tip of the lift arm 4, and a bucket 5 which is disposed between the body 1 and the lift arm 4. In a front loader or the like, in which the lift arm 4 is raised and lowered by a cylinder 7 and rotated by a tilt cylinder 14 disposed between the lift arm 4 and the bucket 5,
A flow rate that distributes and controls the amount of oil supplied to each primary side of the first control valve 19 that switches and controls the supply and discharge of hydraulic pressure to the lift cylinder 7 and the second control valve 20 that switches and controls the supply and discharge of hydraulic pressure to the tilt cylinder 14. Regulating valve 37 or 3
7' and connected in parallel to each other.
A flow regulating valve 37 or 37' including control orifices 39A, 39B is provided, and a circuit 35B in which a second control orifice 39B is inserted into both control orifices 39A, 39B,
The second control valve 20 is provided to pass through the inside of the second control valve 20, and in the dump action position where the tilt cylinder 14 is extended, the circuit 35B is blocked and in the tilt action position where the tilt cylinder 14 is contracted. The valve is configured to unblock the circuit 35B, and the flow rate regulating valve 37 or 37' is configured such that the first control valve 19 and the second control valve 20 are both in the operating position and both the cylinders 7, 14 are operated. When the cylinders 7 and 14 are extended and retracted at the same time, only the first control orifice 39A is applied to the cylinders 7 and 14.
During the contraction operation, the first control orifice 39A
and the second control orifice 39B, the valve is configured to control the oil supply amount so that the bucket 5 can be raised and lowered while maintaining a substantially constant posture. , has the following advantages:

That is, since the bucket actuator of this invention is constructed as described above, when the second control valve 20 is moved to the dump action position, the second control orifice 39B is turned off by the blocking of the circuit 35B. First without being made to act
only the control orifice 39A is activated;
Conversely, when the second control valve 20 is moved to the tilt operating position, the first control orifice 39A and the second control orifice 39B are both activated by unblocking the circuit 35B. valve 20
The selective action of the control orifices 39A, 39B is achieved by the flow regulating valves 37, 3.
Considering that 7' is configured as above,
The first control valve 19 is raised to the operating position U.
Alternatively, when attempting to raise or lower the bucket 5 by moving it to the lowering action position D, if the second control bubble 20 is simultaneously moved to the dumping action position or the tilting action position I, the lift cylinder 7 and The tilt cylinder 14 is simultaneously extended or contracted, and while the bucket 5 is being raised, the bucket 5 is rotated at an appropriate rate, and while the bucket 5 is being lowered, the bucket 5 is tilted at another appropriate rate. The posture of the bucket cart 5 is maintained almost constant as it is moved, and the posture of the bucket cart 5 is maintained when going up and down through the hydraulic circuit structure, which can be called a hydraulic parallel link. Therefore, it produces the following unique effects.

That is, in the conventional case, the brackets 2 and 10 are made larger, and the bracket 10 is pivotally supported on the lift arm 4 at position 11, as shown by the imaginary line in FIG. Then, a rod R (or other link piece) is provided to connect the front and rear brackets 10 and 2 to form a parallel link mechanism as described at the beginning, and the attitude of the bucket 5 is maintained by the parallel link mechanism. Since the parallel link mechanism was intended to be used in this way, the appearance of the front loader etc. is not only spoiled by the parallel link mechanism, but also the parallel link mechanism drives the tilt cylinder 14 to change its attitude when the lift arm 4 is rotated up and down. Damage to the mechanism, especially damage to the rod R, which is subjected to a large compressive force when the bucket lifts, and breakage of its pivot pin occurred relatively early.
The proposed device, which uses a hydraulic circuit structure to maintain the bucket posture, does not have a mechanical posture maintenance mechanism, so it not only has an excellent appearance, but also has a mechanical system that can apply a large amount of force to maintain the posture. It has extremely high durability even though it does not have a mechanism.

Next, as shown in the embodiment, when the dump truck 5 rotates, the tilt cylinder 14 reduces the oil chamber 1.
When configuring the second control valve 20 so that the oil discharged from the tank 4b is supplied to the extension oil chamber 14a to obtain rapid dump rotation of the bucket 5, it is possible to remove dirt, etc. from the bucket 5. The work speed when loading onto a transport vehicle or dumping at a designated location is increased, and soil and sand, which is highly adhesive and tends to stick firmly to the bucket 5, can be removed from the inner surface of the bucket 5 by the rapid dumping rotation of the bucket 5. The adhesion of the bucket is broken and the dump is smoothly discharged from the bucket 5. However, if there is a difference between the dump rotation speed and the tilt rotation speed of the bucket 5, or conversely, the rotation of the lift arm 4 Even in the case where there is a difference between the rising speed and the descending speed of the bucket cart 5, the bucket cart actuating device of this invention provides control that operates when the bucket cart 5 is raised while being rotated in a dump manner and when it is lowered while being rotated in a tilting manner. Orifice 39
Since the flow rate is adjusted by changing the numbers of A and 39B, the desired bucket posture can be maintained without any inconvenience.

The bucket actuator of this invention has a first control orifice 39A which provides the above-mentioned advantages.
Since the second control valve 20 is supposed to selectively operate the control orifices 39A and 39B, the control orifices 39A and 39B are selectively operated. This simplifies the overall valve structure compared to the case where a separate control valve is provided for the control orifice 3.
The selective action of 9A and 39B is achieved not by the long first control valve 19, which is generally a four-position valve with a floating position F, but by the shorter second control valve, which is a three-position valve. Since the control valve 20 of FIG.

[Brief explanation of the drawing]

Fig. 1 is a schematic perspective view of a front loader equipped with the first embodiment of this invention, Fig. 2 is a schematic side view of only the main parts of the front loader, and Fig. 3 is the first embodiment. a circuit diagram showing a hydraulic circuit in;
FIG. 4 is a side view of the valve device provided in the first embodiment, FIG. 5 is a cross-sectional view taken approximately along the - line in FIG. 4, and FIG. 6 is a cross-sectional view taken substantially along the line - in FIG.
7 is a sectional view taken along the line - in FIG. 6, FIG. 8 is a partial view of the section taken along the line - in FIG. 7, and FIGS. 9 and 10 are the - line and - line in FIG. A cross-sectional view along FIG. 11 is the second of this invention.
FIG. 2 is a hydraulic circuit diagram showing an embodiment of the present invention. 1... Airframe, 4... Lift arm, 5... Bucket, 7... Lift cylinder, 12... Rotating plate,
14...Tilt cylinder, 17...Operating rod, 1
8, 18'... Valve device, 19... First control valve, 20... Second control valve, 20S... Spool, 34... Oil supply circuit,
35...Refueling circuit, 35A...First circuit, 35
B...Second circuit, 37, 37'...Flow rate adjustment valve,
38... Throttle, 39A... First control orifice, 39B... Second control orifice, 40...
Pressure compensation valve, 80...flow control valve.

Claims (1)

[Scope of utility model registration request] The bucket is pivoted to the tip of the lift arm,
In front loaders, etc., in which the lift arm is raised and lowered by a lift cylinder placed between the aircraft and the lift arm, and rotated by a tilt cylinder placed between the lift arm and the bucket, the hydraulic pressure applied to the lift cylinder is The first control valve switches and controls the supply and discharge of hydraulic pressure to and from the tilt cylinder, and the second control valve switches and controls the supply and discharge of hydraulic pressure to and from the tilt cylinder. A flow regulating valve including first and second control orifices connected to each other is provided, and a circuit into which the second of the two control orifices is inserted passes through the second control valve. The second control valve is configured to be a valve that blocks the circuit in a dump action position where the tilt cylinder is extended and unblocks the circuit in a tilt action position where the tilt cylinder is contracted. The flow regulating valve is connected to the first control valve and the second control valve.
When both the cylinders are expanded and retracted at the same time with both control valves in the operating position, only the first control orifice is activated during the cylinder extension operation, and both the first control orifice and the second control orifice are activated during the cylinder contraction operation. A bucket actuating device characterized in that it is configured with a valve that controls oil supply amount distribution so that the bucket can be raised and lowered while maintaining a substantially constant posture.