JPS6326441Y2 - - 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 achieved by rotatably supporting a bracket 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 operated and the lift arm is rotated up and down, the relative posture of the tilt cylinder with respect to the lift arm is changed by the parallel link mechanism, and conversely, the relative posture of the bucket with respect to the lift arm is changed. He was trying to maintain a constant posture.

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 repeated loads. This was the part that was most likely to break on front loaders, etc. Furthermore, when the bucket is moved upward, a large compressive force is applied to the rod or plate connecting the two brackets.
Shock waves or surge pressure tend to occur in the hydraulic circuit, and it is also necessary to provide an overload relief valve in the hydraulic circuit to protect members by releasing such shock waves or surge pressure.

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 create a front panel that eliminates the above-mentioned problems. An object of the present invention is to provide a novel bucket actuation device for a loader or the like.

The configuration of the bucket actuator according to the invention will be explained with reference to the illustrated embodiment.This embodiment is used in a front loader in which a loader mechanism is attached to the front part of the body 1 of a tractor as shown in FIG. This relates to an example in which the idea was implemented. 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 arm portions. The lift arm 4 is provided with a pivot 6 at the tip of the lift arm 4 which is fixedly connected between the two. The lift cylinders 7 are provided in pairs on the left and right, with cylinder ends pivotally supported 8 on the above-mentioned bracket 2, and piston rod ends pivoted 9 midway through the lift arm 7. A pair of left and right brackets 10 are fixedly provided 11 in the middle of the lift arm 4, and a pair of left and right rotating plates 1 are provided near the tip of the lift arm 4.
2 is pivotally mounted at 13. The tilt cylinder 14 is
The cylinder end is pivoted 15 to the bracket 10 described above.
A pair of left and right piston rods are provided with the ends of the piston rods pivotally connected to the above-mentioned rotating plate 12 at 16.
A pair of left and right operating rods 17 are provided which are pivotally connected at both ends to the rotating plate 12 and the bucket 5 described above. 17.

A valve 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 both cylinders 7,
The first control valve 19 and the second control valve 20 are particularly connected in series in this order in the oil supply direction. That is, the first
The hydraulic oil is supplied to the primary side of the control valve 19 of the first control valve 19, and the hydraulic oil is supplied from the secondary side of the first control valve 19 to the primary side of the second control valve 20 through the oil supply circuit 24. The tank ports 19T and 20T on the primary side of each control valve 19 and 20 are connected to the oil tank 2.
The oil drain circuit 25 connected to the control valve 1 is shared by both control valves 19 and 20. The first control valve 19 has two pump ports 19P ₁ and 19P ₂ connected to the oil supply circuit 23 on the primary side, and an expansion oil chamber 7a and a contraction oil chamber 7a of the lift cylinder 7 on the secondary side. Circuit 2 in chamber 7b
In addition to two cylinder ports 19C ₁ and 19C ₂ connected via ports 6 and 27, one outlet port 19A is provided.
The base end of the oil supply circuit 24 led toward the control valve 20 is connected to the outlet port 19A.

The first control valve 19 described above has a pump port 19P ₁ , a tank port 19T, and cylinder ports 19C ₁ and 19C ₂ in the neutral position N.
The lift cylinder 7 is maintained in a stopped state by blocking the flow, and at the same time, the pump port _19P1 and the outlet port 19A are communicated with each other to supply oil in the direction of the second control valve 20. Also, the first control valve 19
connects pump port 19P ₁ to cylinder port 19
Pump port 19P is connected to C ₁ to extend the lift cylinder 7, and pump port 19P is connected to cylinder port 19C ₂ to extend the lift cylinder ₇ .
In particular, the cylinder port 19C 2 is connected to the cylinder port 19C ₂ in the above-described upward movement position U, and the cylinder port 19C 1 is connected to the cylinder port 19C ₁ in the downward movement position D.
A, and is configured to supply return oil from the lift cylinder 7 to the oil supply circuit 24 and, therefore, to the second control valve 20 at each operating position U, D. In addition, the pump port _19P2 and the tank port 19T are supposed to be blocked at each of the above working positions U and D.
The first control valve 19 also has one other floating position F, in which both cylinder ports 19C ₁ and 19C ₂ are communicated with the tank port 19T, and the lift arm 4 and bucket 5 are in flow. In this case, the pump port _19P2 is communicated with the outlet port 19A so that oil can be supplied in the direction of the second control valve 20.

Next, the second control valve 20 has two pump ports 20P ₁ connected to the oil supply circuit 24,
20P ₂ on the primary side, and two cylinder ports 20C ₁ and 20 connected to the contraction oil chamber 14b and expansion oil chamber 14a of the tilt cylinder 14 via circuits 28 and 29, respectively, on the secondary side.
In addition to C ₂ , it is configured to have one outlet port 20A, which is connected by a circuit 31 to a carry-over port 30 provided in the valve device 18. In addition to the neutral position N where the second control valve 20 blocks the pump port 20P ₁ , tank port 20T, and cylinder ports 20C ₁ and 20C ₂ to maintain the tilt cylinder 14 in a stopped state,
Pump port 20P ₁ to cylinder port 20C ₁ ,
Also, cylinder port 20C ₂ and tank port 20
A tilt action position in which the tilt cylinder 14 is contracted by communicating with T, and a tilt action position in which the pump port 20P ₁ is communicated with the cylinder port 20C ₂ and the cylinder port 20C ₁ is also communicated with the cylinder port 20C ₂ to extend the tilt cylinder 14. In particular, it is configured to include throttle oil passages 32A, 32B connecting the pump port _P1 to the tank port 20T in each of the above-mentioned operating positions. In addition, at neutral position N, pump port 20
P ₂ is in communication with outlet port 20A, and at each working position, pump port 20P ₂ and outlet port 20A are blocked.

As mentioned above, in the dump action position of the second control valve 20, not only the pump port 20P ₁ but also the cylinder port 20C ₁ is connected to the cylinder port 2.
The reasons why it was decided to communicate with _0C2 are as follows. That is, in the tilt cylinder 14, the pressure receiving area of the piston 14c facing the expansion oil chamber 14a is _S1 , whereas the piston 14c faces the contraction oil chamber 14b. The pressure-receiving area of the piston 14c is the area S ₁ −S ₀ obtained by subtracting the cross-sectional area S ₀ of the piston rod 14d from the above-mentioned area S ₁ , and the pressure-receiving area difference ₁ S ₁ −S ₀ at the dump action position is
As a result, the oil in the contraction oil chamber 14b flows through the circuit 28, the control valve 20, and the circuit 29 to the extension oil chamber 14a, which causes the tilt cylinder 14 to quickly expand and cause the cylinder 4 to quickly dump. We are trying to make sure that it works.

In FIG. 3, 33 is a pressure regulating valve that sets the hydraulic pressure applied to both cylinders 7 and 14;
Reference numerals 4 and 35 indicate check valves that are inserted into respective connection circuits to the pump ports 19P ₁ and 20P ₁ of the oil supply circuits 23 and 24 to prevent backflow of oil from the direction of each cylinder 7 and 14, and 36 and 37 indicate Each is a connection port for an oil pressure gauge.

In the circuit structure shown in FIG. 3, the first control valve 19 is placed in the neutral position N or the floating position F, and the second control valve 2
0 to the neutral position N, the oil supply circuits 23 and 24
Hydraulic pressure can be taken out to the carry over port 30 via the circuit 31 and the hydraulic pressure can be used to operate other hydraulically operated equipment, and when the second control valve 20 is in the neutral position N, the first control valve 19 can be selectively moved to each operating position U or D to selectively extend or contract the lift cylinder 7, and therefore to selectively raise or lower the bucket 5, and the first With the control valve 19 in the neutral position N, the second control valve 20 is selectively moved to each operating position or positions to perform a contraction or extension operation of the tilt cylinder 7, and therefore a tilt or dump operation of the bucket belt 5. Although the operation can be performed selectively, the first control valve 19 is placed in the upward action position U, and the second control valve 20 is
When the control valve 20 is placed in the dumping position, and when the first control valve 20 is placed in the lowering position D and the second control valve 20 is placed in the tilting position, the following will occur.

That is, when 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 is extended and the bucket 5 is raised, and the tilt cylinder 14 is extended and the dumping rotation of the bucket 5 is obtained, but at this time, the tilt cylinder 14 uses the oil from the reduction oil chamber 7b of the lift cylinder 7 and the tilt cylinder 1.
The bunched oil from the contraction oil chamber 14b of No. 4 is supplied to the expansion oil chamber 14a for the expansion operation, and a part of such return oil is drained through the restriction oil passage 32B. Ru. When the first control valve 19 is placed in the lowering position D and the second control valve 20 is placed in the tilting position, the lift cylinder 7 is compressed to lower the bucket 5 and the tilt cylinder 14 is The tilting movement of the bucket 5 is obtained by the reduction operation, but at this time, the tilt cylinder 14
The return oil from the expansion oil chamber 7a of the lift cylinder 7 is supplied to the contraction oil chamber 14b to perform the contraction operation, and a part of such return oil is passed through the throttle oil passage 32A. Drained.
In this way, when both cylinders 7 and 14 are expanded and contracted at the same time, part of the oil supplied to the oil chamber 14a or 14b of the tilt cylinder 14 is drained via the throttle oil passage 32B or 32A. The ratio of the expansion/contraction speed of the lift cylinder 7 and the expansion/contraction speed of the tilt cylinder 14 depends on the ratio of oil drain through the throttle oil passages 32B, 32A, whereas The oil flow cross-sectional area is set as follows.

That is, when lifting the bucket 5 by moving the lift arm 4 using the lift cylinder 7, for example, when raising and lowering the bucket 5 from the position indicated by the two-dot chain line in FIG.
If the tilt cylinder 14 is not operated at all, as the lift arm 4 rotates upward, the bracket 10 on the lift arm 4 changes its posture so that its upper end side is displaced rearward, thereby causing the tilt cylinder 14 to change its position. The entire body is pulled proximally,
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, each throttle oil passage 32B, 32A is connected to both cylinders 7, 1 with both control valves 19, 20 at operating position U or D, as described above.
If cylinders 4 and 4 are extended and retracted at the same time, the bucket belt 5 can be raised and dumped, or lowered and tilted, but when both cylinders 7 and 14 are extended and contracted simultaneously, the bucket When the bucket 5 is raised, some of the oil is squeezed and released from the oil passage 32B, while the tilt cylinder 14, which supplies hydraulic oil to the extension oil chamber 14a, rotates the dump. The tilt cylinder 14 is tilted and rotated by the tilt cylinder 14, which supplies hydraulic oil to the reduction oil chamber 14b while allowing the throttle oil passage 32A to escape, so that the bucket 5 can be raised and lowered while maintaining a substantially constant posture. Each oil chamber 14
It is formed to have an oil flow cross-sectional area that controls the oil supply ratio to a and 14b. More specifically, as described above, the second control valve 20 connects the circuits 28 and 29 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. 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 expansion oil chamber 14a of the tilt cylinder 14, The rate of supply of hydraulic oil from the contraction oil chamber 7b of the lift cylinder 7 to the expansion oil chamber 14a is lowered, and the bucket 5 is raised so that the dumper is rotated at a speed commensurate with the lifting speed of the bucket 5. The oil flow cross-sectional area of the throttle oil passage 32B that is set to be applied when the bucket 5 is lowered is the same as that of the throttle oil passage 3 that is set to be applied when the bucket 5 is lowered
Make it considerably larger than the oil flow cross section of 2A,
Both when the bucket 5 goes up and when it goes down, the bucket 5
The posture is maintained almost constant.

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 device 18 is
Multiple housing units 39A, 39B, 3
9C and 39D are stacked in this order from the top in the drawing and are connected by an appropriate number of connecting screws 40 to form a stack valve. As clearly shown in FIG. 4, a pump port 41P connected to the hydraulic pump 22 and a tank port 41T connected to the oil tank 21 are respectively provided in the housing unit 39A, and Both cylinder ports 19C ₁ , 1 of control valve 19
_9C2 is provided in the housing unit 39B,
Further, both cylinder ports 20C ₁ and 20C ₂ of the second control valve 20 described above are provided in the housing unit 39C, and the carry over port 30 is provided in the housing unit 39D.
It is set in. A spool 19S constituting the first control valve 19 is attached to the housing unit 39B.
Spools 20S constituting the second control valve 20 are supported in parallel to each other on 9C. As clearly shown in FIG. 7, the pressure regulating valve 33 is configured in the shape of a balanced piston, and is connected to an air space formed in the housing unit 39A so as to connect the pump port 41P and the tank port 41T. It is installed in the tank port 41T side in the tank port 42.

As shown in FIGS. 6-8, an oil passage 43 is formed in the housing unit 39B and communicates with the cavity 42 in the housing unit 39A, in which the pump port 41P of the valve device 18 is opened. The pump port _19P2 is formed by opening the end of the oil passage 43 at the center of the axial direction of the spool 19S on the outer circumference of the spool 19S. Also, an oil passage 4 connected to the oil passage 43
4, 45, 46 are formed in the housing unit 39B, the check valve 34 is inserted into the oil passage 46, and the oil passage 4 is inserted from the secondary side of the check valve 34.
6 is branched into two oil passages, which are opened at two locations on the outer periphery of the spool 19S at appropriate intervals in the axial direction of the spool 19S, and the open ends are connected to pump ports 19P _1a and 1 corresponding to the pump port 19P ₁ .
It is configured in 9P _1b . Cylinder port 19C ₁ ,
19C ₂ is connected to each pump port 19P _1a , 1 by means of an oil passage formed in the housing unit 39B.
An opening is made to the outer circumference of the spool 19S at a position outside the side of 9P _1b . Housing unit 39C, 39
As shown in FIG. 6, oil passages 47, 48, and 49 arranged vertically are formed in B and 39A.
An oil passage 49 is communicated with a tank port 41T of the valve device 18 within the housing unit 39A. The tank port 19T connects the oil passage 48 in the housing unit 39B to the outer periphery of the spool 19S at an outer position on each side of the cylinder ports 19C ₁ and 19C ₂ by means of other oil passages 50A and 50B in the unit 39B. Open it in a certain place,
It is divided into two tank ports 19Ta and 19Tb. Furthermore, the outlet port 19
A is spool 1 on both sides of pump port 19P ₂
Two outlet ports 19 are opened at the outer circumference of 9S.
It is divided into Aa and 19Ab.

Port 19 of first control valve 19
P _1a , 19P _1b , 19P ₂ , 19Ta, 19Tb, 19
C ₁ , 19C ₂ , 19Aa, and 19Ab are provided as described above, whereas the spool 19S of the first control valve 19 has four lands 19
a, 19b, 19c, and 19d, and two oil passage holes 19 along the axial direction inside.
The oil passage holes 19e and 19f are opened toward the outer periphery of the spool 19S at two locations spaced apart appropriately in the axial direction of the spool 19S. A check valve 51 is inserted into the oil passage hole 19e on the tip side and allows oil to flow only inward from the cylinder port _19C1 .

As described above, the spool 19S achieves the oil flow path switching of the first control valve 19 explained with reference to FIG. 3 in the following manner. That is, when the spool 19S is pushed in a certain amount from the illustrated neutral position N, it is displaced to the upward action position U, and conversely, when it is pulled out a certain amount from the neutral position N, it is displaced to the downward action position D. , is supposed to be displaced to the floating position F when it is further pulled out by a certain amount, but in the neutral position N shown in the figure, the pump ports 19P _1a , 19P _1b
are blocked by lands 19a and 19d, respectively, tank ports 19Ta and 19Tb are blocked by lands 19a and 19d, respectively, and tank port 19Ta is blocked by lands 19a and 19d, respectively.
9b, and tank port 19Tb is connected to land 1.
9d, the relationship is blocked.
Pump port 19P ₂ is land 19b, 19c
between the outlet port 19Aa and the land 19c,
19d are communicated with the outlet port 19Ab, respectively, and communicated with the outlet port 19A.

At the raising action position U where the spool 19S is pushed in, the pump port _19P2 is disconnected from the outlet port 19Aa by the land 19c and disconnected from the outlet port 19Ab by the land 19d, resulting in a blocked relationship. It is said that In addition, the pump port 19P _1a has both opening ends of the oil passage hole 19e at the port 19P _1a and 19C ₁ positions.
The cylinder port 19 is connected to the cylinder port 19 through the oil passage hole 19e.
It is made to communicate with _C1 . Further, the cylinder port 19C ₂ is brought into communication with the outlet port _19Ab , and thus with the outlet port 19A, via the oil passage 19f, by bringing both open ends of the oil passage hole 19f to the positions of the ports 19C 2 and 19Ab. Note that both tank ports 19Ta and 19Tb are in a blocked relationship as in the neutral position N.

In the descending position D, where the spool 19S is pulled out from the neutral position N by a small amount, the pump port _P2 is disconnected from the outlet port 19Aa by the land 19b, and is connected to the outlet port 1 by the land 19c.
Communication with 9Ab is cut off and the relationship is considered blocked. Further, the pump port 19P _1b is communicated with the cylinder port C ₂ via the oil passage hole 19f by bringing both open ends of the oil passage hole 19f to the port 19P _1b and 19C ₂ positions. Further, the cylinder port C ₁ is communicated with the outlet port 19Aa and therefore the outlet port 19A via the oil passage hole 19f by bringing both open ends of the oil passage hole 19e to the port 19C ₁ and 19Aa positions. ,
At this time, the check valve 51 in the oil passage hole 19e is operated so that oil is forcibly drained from the expansion oil chamber 7a based on the contraction operation of the cylinder 7 due to the hydraulic pressure acting on the contraction oil chamber 17b of the lift cylinder 7. ,
Forced to open up. In addition, both tank ports 19Ta,
19Tb is in the same blocked relationship as at the neutral position N.

In the floating position F, where the spool 19S is pulled out a little further from the lowering position D, the pump port _19P2 is connected to the outlet port 19Aa between the lands 19b and 19c, and therefore the outlet port 19
It is made to communicate with A. Pump port 19P _1a
is due to the land 19b and the pump port 19
P _1b is in a blocked relationship between lands 19c and 19d. Cylinder port 19
C ₁ is communicated with the tank port 19Ta between the lands 19a and 19b. Further, the cylinder port 19C ₂ is communicated with the tank port 19Tb via the oil passage hole 19f by bringing both open ends of the oil passage hole 19f to the positions of the ports 19C ₂ and 19Tb.

As described above, at the upward action position U of the spool 19S, the cylinder port _19C2 is connected to the outlet port 19.
By being communicated with A, the lift cylinder 7
The return oil from the oil chamber 7b is connected to the outlet port 1.
Brought to 9A. Further, at the downward action position D of the spool 19S, the cylinder port _19C1 is communicated with the outlet port 19A, so that return oil from the extension action oil chamber 7a of the lift cylinder 7 is brought to the outlet port 19A.

Next, to explain the specific structure of the second control valve 20, as shown in FIGS. 6 and 7, an oil passage 53 connected to the outlet port 19A formed in the housing unit 39B is connected to the housing unit 39C. The end of the oil passage 53 is opened at the center of the axial direction of the spool 20S on the outer periphery of the spool 20S, thereby forming the pump port _20P2 . In addition, the oil passage 53
Oil passages 54, 55, and 56 are formed in the housing unit 39C, and the check valve 35 is inserted and installed in the oil passage 56.
The oil passage 56 is branched into two oil passages from the secondary side and opened at two locations on the outer periphery of the spool 20S at appropriate intervals in the axial direction of the spool 20S, with the opening ends corresponding to the pump port 20P ₁ . Pump ports 20P _1a and 20P _1b are configured. As shown for the cylinder port 20C ₁ in FIG. 5, the cylinder ports 20C ₁ and 20C ₂ are located outside the pump ports 20P _1a and 20P _1b at the outer periphery of the spool 20S by means of oil passages formed in the housing unit 39C. It is opened to In addition, the oil passage 47 (FIG. 6) in the housing unit 39C, which is connected to the tank port 41T of the valve device 18, is connected to the other oil passage 57 in the unit 39C.
Accordingly, the tank port 20T is divided into two tank ports 20Ta and 20Tb by opening at two locations on the outer periphery of the spool 20S at the outer positions on each side of the cylinder ports 20C ₁ and 20C ₂ . Furthermore, the outlet port 20A is opened toward the outer periphery of the spool 20S on both sides of the pump port _20P2 , and divided into two outlet ports 20Aa and 20Ab. The outlet port 20A is connected to the carry over port 30 by an oil passage 58 in the housing unit 39D.

Port 20 of second control valve 20
P _1a , 20P _1b , 20P ₂ , 20Ta, 20Tb, 20
C ₁ , 20C ₂ , 20Aa, and 20Ab are provided as described above, whereas the spool 20S of the second control valve 20 has six lands 20
a, 20b, 20c, 20d, 20e, and 20f, and the throttle oil passages 32A, 32B have one end connected to tank ports 20Ta, 20Tb, respectively, as shown in FIGS. It also consists of a slot formed on the outer peripheral surface of the spool 20S so as to be open at all times.

As described above, the spool 20S achieves the oil flow path switching of the second control valve 20 explained with reference to FIG. 3 in the following manner. That is, when the spool 20S is pushed in a certain amount from the neutral position N shown in the figure, it is displaced to the tilt action position, and conversely, when it is pulled out a certain amount from the neutral position N, it is displaced to the dump action position. However, at the neutral position N shown in the figure,
Pump port 20P _1a is blocked between lands 20b and 20c, pump port 20P _1b is blocked by land 20e, and tank ports 20Ta and 20Tb are blocked between lands 20a and 20c, respectively.
Blocked by 0f. pump port 20
P ₂ is the exit port 2 between lands 20c and 20d.
It is connected to 0Aa and land 20d,
20e communicates with the outlet port 20Ab, which in turn communicates with the outlet port 20A.

In the tilting position where the spool 20S is pushed in, the pump port 20P ₂ is disconnected from the outlet port 20Aa by the land 20c and disconnected from the outlet port 20Ab by the land 20d, so that the pump port 20P ₂ and the outlet are disconnected from each other. port 2
The relationship with 0A is blocked. The pump port 20P _1a is communicated with the cylinder port 20C ₁ between the lands 20a and 20b, and the cylinder port 20C ₁ is connected to the spool 20C.
Tank port 20 via throttle oil passage 32A on S
It is also connected to cylinder port 2.
_0C2 is communicated with the tank port 20Tb between the lands 20e and 20f.

Next, in the dump operation position where the spool 20S is pulled out, the pump port 20P ₂ is disconnected from the outlet port 20Aa by the land 20d and disconnected from the outlet port 20Ab by the land 20e, so that the pump port 20P ₂ is disconnected from the outlet port 20Ab by the land 20e. The outlet port 20A is in a blocked relationship. And pump port 20P _1b is land 20e, 20f
The cylinder port 20C ₂ is connected to the tank port _20Tb via the throttle oil passage 32B on the spool 20S, and the cylinder port 20C ₁ is connected between the lands 20a and 20b. It is communicated with tank port 20Ta.

As described above, in the tilting position of the spool 20S, the cylinder port _20C1 , which is communicated with the pump port _20P1 , is connected to the throttle oil passage 32A.
By communicating with the tank port 20Ta through the spool 20S, part of the oil is drained and the reduction operation oil chamber 14b of the tilt cylinder 14 is refilled, and when the spool 20S is in the dump operation position, it is connected to the pump port _20P2 . By communicating the cylinder port _20C2 with the tank port 20Tb through the throttle oil passage 32B, some of the oil is drained and the extension oil chamber 14a of the tilt cylinder 14 is refilled with oil. Yes, throttle oil passage 32 on spool 20S
The oil flow cross-sectional areas of A and 32B are set as described above.

As shown in FIGS. 7 and 8, the spools 19S and 20S are located at respective operating positions at the tip of the spool 19S of the first control valve 19 and the tip of the spool 20S of the second control valve 20, respectively. A return spring mechanism 59, 60 is provided with springs 59a, 60a which are compressed when the spools 19S, 20S are compressed when the spools 19S, 20S are compressed when the operating force is released. , is arranged. Further, the tip of the spool 19S of the first control valve 19 is provided with a ball 61c that plunges into the detent slot 61b by the force of the spring 61a when the spool 19S is displaced to the floating position F. A detent mechanism 61 for restraining the position of the floating position F is also provided.

Since the illustrated embodiment is constructed as described above, the bucket 5 for storing soil or fertilizer is placed in a horizontal position on the ground as shown by the two-dot chain line in FIG. When lifting the bucket 5 by extending it, if the first control valve 19 is moved to the lifting position U and the second control valve 20 is simultaneously moved to the dumping position to raise the bucket 5, then the bucket 5 is raised. 5 is raised while being gradually dumped and rotated by the supplied tilt cylinder 14 while a part of the oil brought from the direction of the first control valve 19 is throttled and drained from the oil passage 32B. Then, as shown by the solid line in FIG. 2, the bucket 5 is raised while maintaining a substantially horizontal position, and dirt and fertilizer do not spill out from inside the bucket 5. Conversely, when lowering the bucket 5 in a horizontal position that accommodates soil or fertilizer, move the second control valve 19 to the lowering position D and at the same time move the second control valve 20 to the tilting position. Bucket 5 is the first control valve 1
A portion of the oil brought in from nine directions is squeezed and drained from the oil passage 32A, while being gradually tilted and rotated by the supplied tilt cylinder 14 and lowered, thereby maintaining an almost horizontal posture. As I was forced to descend,
Similarly, spilling of earth and sand, etc., is prevented.

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 first control valve 19 that switches and controls the supply and discharge of hydraulic pressure to the lift cylinder 7 and a second control valve 20 that switches and controls the supply and discharge of hydraulic pressure to the tilt cylinder 14 are connected in series in this order in the oil supply direction. The first control valve 19 is configured as a valve that supplies the return oil from the lift cylinder 7 toward the second control valve 20 at each of its operating positions U and D, and the second control valve 20 is configured to:
At each of its working positions, the pump port 20
P ₁ is configured as a valve including throttle oil passages 32A, 32B connected to the tank port 20T, and the throttle oil passages 32A, 32B are configured such that the first control valve 19 and the second control valve 20 are both in the operating position. The tilt cylinder 14 is formed with an oil flow cross-sectional area that controls the oil supply ratio to the tilt cylinder 14 so that the bucket 5 can be raised and lowered while maintaining a substantially constant posture when both cylinders 7 and 14 are expanded and contracted simultaneously. It has the following advantages:

That is, since the bucket actuator of this invention is configured as described above, the bucket belt 5 can be raised or lowered by moving the first control valve 19 to the raising action position U or the lowering action position D. If the second control valve 20 is moved to the dump action position or the tilt action position at the same time, the lift cylinder 7 and the tilt cylinder 14 are simultaneously extended or contracted. In this case, the attitude of the bucket cart 5 is maintained almost constant by rotating the bucket cart 5 at an appropriate rate, and tilting the bucket cart 5 at an appropriate rate during the descent of the bucket cart 5. Since the attitude of the bucket cart 5 is maintained during elevation and descent by the hydraulic circuit structure, which can be called a hydraulic parallel link, the following unique effects are produced.

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 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 breakage of the rod R, which is subjected to a large compressive force when the bucket lifts, and breakage of its pivot pin, occur relatively early, and the high compressive force that is applied to the rod R, as described above, causes hydraulic pressure. Whereas an overload relief valve was installed to relieve the surge pressure generated in the circuit, the proposed device, which uses a hydraulic circuit structure to maintain the bucket posture, has a mechanical posture maintenance mechanism. Not only does it have an excellent appearance, but it also has extremely high durability.Also, it does not have a mechanical mechanism that can apply large forces to maintain its posture, and it does not have the ability to withstand surge pressure to counter such forces. Since this does not occur in the hydraulic circuit, the conventional overload relief valve is not required.

Furthermore, the bucket actuator of this invention conventionally has a first control valve 19 and a second control valve as described above.
In contrast, the first and second control valves 19 and 20 are connected in series in the oil supply direction, and the first control valve 19 and the second control valve 20 are connected in parallel in the oil supply direction. At each operating position, the return oil from the lift cylinder 7 is supplied to the second control valve 20 direction. A valve is configured to drain part of the oil supplied to the cylinder ₁ from the throttle oil passages 32A and 32B and supply it to the tilt cylinder 14, so as to maintain the bucket posture hydraulically as described above. The throttle oil passages 32A and 32B that control the oil supply ratio are connected to the second control valve 2.
0, compared to a case where such an oil supply ratio control mechanism, that is, a flow rate adjustment valve mechanism, is provided separately outside the control valve.
The valve structure and oil passage structure are simplified, and as shown in the embodiment, the dumping and tilting speeds for maintaining the attitude can be changed when the bucket is raised and lowered. Also, a pair of throttle oil passages 32A, 32B are provided as in the embodiment, and the throttle oil passages 32A, 32B provided in the second control valve 20 itself are connected to the valve 20.
It is designed to be easy to switch so that one of them acts alternatively by displacement.

[Brief explanation of the drawing]

Fig. 1 is a schematic perspective view of a front loader equipped with an embodiment of this invention, Fig. 2 is a schematic side view of only the main components of the front loader section, and Fig. 3 is a hydraulic circuit in the same embodiment. FIG. 4 is a front view of the valve device provided in the same embodiment, FIG. 5 is a vertical side view of the same valve device, and FIG.
Figure 7 is a vertical cross-sectional view taken along the - line in Figure 6, Figure 8 is a vertical cross-sectional view taken along the - line in Figure 6.
A cross-sectional view along a line FIG. 9 is a cross-sectional view of one member. 1... Airframe, 4... Lift arm, 5... Bucket, 7... Lift cylinder, 12... Rotating plate,
14...Tilt cylinder, 17...Operating rod, 18
... Valve device, 19 ... First control valve, 19P ₁ , 19P ₂ ... Pump port, 19
T...tank port, 19C ₁ , 19C ₂ ... cylinder port, 19A... outlet port, 19S...
Spool, 20...second control valve,
20P ₁ , 20P ₂ ... pump port, 20T ...
Tank port, 20C ₁ , 20C ₂ ... Cylinder port, 20A ... Outlet port, 20S ... Spool, 23 ... Oil supply circuit, 24 ... Oil supply circuit, 25
...Drainage circuit, 26, 27...Circuit, 28, 29
...Circuit, 32A, 32B... Squeezing oil passage.

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 A first control valve for switching and controlling supply and discharge of hydraulic pressure to and from the tilt cylinder and a second control valve for switching and controlling supply and discharge of hydraulic pressure to and from the tilt cylinder are connected in series in this order in the oil supply direction, and the first control valve is connected in series in the oil supply direction. , configured as a valve that supplies return oil from the lift cylinder in the direction of the second control valve in each of its working positions, and a throttle oil that connects the second control valve with the pump port to the tank port in each of its working positions. The throttle oil passage is configured as a valve including a passage, and when the first control valve and the second control valve are both in the operating position and both cylinders are simultaneously expanded and contracted, the bucket moves up and down while maintaining a substantially constant posture. It is noted that the tilt cylinder is formed with an oil flow cross-sectional area that controls the oil supply ratio to the tilt cylinder.
A bucket actuation device is a feature.