JPS6026569Y2 - Three-point hit device for agricultural tractors - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a three-point hit device for an agricultural tractor.

The three-point hitch device that supports the agricultural machinery of an agricultural tractor and raises and lowers it is shown in Figure 1 and consists of two left and right lower rings a and b and one top link C. Agricultural machinery such as subsoilers and plows attached to the three-point hit device is raised and lowered by rotating the lift lever d connected to a and b with the lifting cylinder device e in the vertical direction. .

However, in the hydraulic circuit of the conventional three-point hit device, as shown in Figure 2, a fixed throttle valve g is inserted into the hydraulic circuit leading to the lifting cylinder device, which prevents overspeeding due to the weight of the agricultural machine when lowering it. However, the weight of the agricultural machinery to which it is attached is not constant, so depending on the agricultural machinery, the vehicle speed and
There were problems with the lowering speed of floating the control valve being inconsistent, resulting in a large shock when descending, or the descending speed after touching the ground surface was slow.

Furthermore, in Fig. 2, f is the main switching valve, which has "upper",
``Hold'', ``Bottom'', and ``Float'' positions f□9 '2. f39
There is f4.

In addition, the hydraulic circuit of the elevating/lowering silling device e in the conventional three-point switch device is as shown in Fig. 2, and the hydraulic circuit is as shown in Fig. 2. f3. f4
Each state is controlled by lever operating the operating valve f, which has a Therefore, if there is an obstacle while working with a subsoiler, plow, etc. with the control valve f set to the "hold" position f2, it will be pushed up by these agricultural machinery, placing a large load on the agricultural machinery and lifting equipment, which may cause malfunctions. Become.

The present invention was developed in consideration of the above-mentioned issues, and by interposing a lift response control device with a variable throttle valve in the hydraulic circuits on the lowering and raising sides of the lifting cylinder device, the lifting speed of the agricultural machine can be controlled by the weight of the agricultural machine. It can be set arbitrarily according to the situation, etc., and can prevent shocks and delays in descending speed when raising and lowering agricultural machinery, and can also be used when operating subsoilers, plows, etc. with the main switching valve in the "Hold" position. A three-point hit device for agricultural tractors that protects the agricultural machinery by lifting it up with its uplifting force and preventing large loads from acting on it, even if there is an obstacle during work with the agricultural machinery. This is what we are trying to provide.

The configuration will be explained below based on the embodiment shown in FIG.

In FIG. 3, 1 in the figure is a lifting cylinder, and this lifting cylinder 1 has a piston rod 3 connected to a lift lever 2.
The piston has a double-acting double-piston type having a first pin 4 having a cylindrical shape, and a second piston 5 which is freely fitted to the bottom side of the first piston 4.

The intermediate chamber 6 between the first piston 4 and the second piston 5 is constantly drained through an oil hole 7 provided in the piston rod 3.

The rod side chamber 8 and bottom side chamber 9 of the lifting cylinder 1 are
Each position 10a = 10b, 10 of the jounin “Ko” and “Uki”
It is connected to a hydraulic power source 11 via a main switching valve 10 having a valve 10c.

The "up" position 10a of the main switching valve 10 communicates between the hydraulic power source 11 and the bottom chamber 9, and the drain circuit and the rod side chamber 8, and the "hold" position 10b closes the bottom chamber 9. At the same time, the rod side chamber 8 is connected to the hydraulic power source 11 and the drain circuit, and the "floating" position 10c connects the rod side chamber 8 and the bottom side chamber 9 to the hydraulic power source 11.
1 and the drain circuit.

Further, in the bottom side circuit 12 connecting the bottom side chamber 9 and the hydraulic pressure source 11, a lowering switching valve 13 is installed in parallel with the main switching valve 10 and having a "lower" position 13a and a "drain" position 13b. It is.

The main switching valve 10 and the lowering switching valve 13 may be of either a solenoid valve configuration or a manual type.

A check valve 14a1 and a variable throttle valve 1 are installed in the bottom side circuit 12.
A lift response control valve 14 consisting of 4b is interposed.

The "lower" position 13a of this lowering switching valve 13 communicates the bottom side circuit 12 with the drain circuit, and closes the drain circuit from the main switching valve 10.
Position 13b closes the bottom side circuit 12 and communicates with the drain circuit from the main switching valve 10.

The lowering switching valve 13 is normally in the "drain" position 13.
b, and when the main switching valve 10 is in the "hold" position 10b, it can be switched to the "down" position 13a.

15 is a three-point hitch installed at the rear of the tractor and raised and lowered by the lift lever 2; 16 is a lower link;
17 is a top link, 18 is an adjustment link, and 19 is a plow that is an example of an agricultural machine attached to the three-point hitch 15.

In the above configuration, the agricultural machine is raised and lowered by switching the main switching valve 10, but when the main switching valve 10 is in the "floating" position, that is, in the case of descending, the lifting cylinder device 1 is in a free state over the entire stroke, and the agricultural machine descends due to its own weight.

On the other hand, when the main switching valve 10 is set to "Hold", the lifting cylinder device 1
The bottom side chamber 9 is closed to stop the movement of the second piston 5 toward the bottom, and the second piston 25 determines the end of the stroke of the first piston 4 in the downward direction.

Therefore, the lowering position of the agricultural machine is determined by the position of the second piston 5, and the plowing depth remains constant.

Also, in this state, the first piston 4 is in a free state between the second piston 5 and the cylinder rond side, so
If an upward force greater than a downward force due to its own weight is applied to the agricultural machine due to an obstacle or the like during work, the machine is upwardly moved by the stroke of the first piston 4, thereby being able to escape the excessive traction force.

Further, when the lowering switching valve 13 is set to the "lower" position 13a while the main switching valve 10 is in the "hold" position 10b, the lifting cylinder 1 is forcibly shortened and the agricultural machine is forcibly lowered.

When the agricultural machine is raised or lowered by the expansion and contraction of the lifting cylinder 1, the bottom side circuit 1 of the lifting cylinder device 1
By adjusting the variable throttle valve 14b of the lift response control valve 14 in the control valve 2, the rising or falling speed of the agricultural machine is adjusted.

Since the present invention is as described above, by adjusting the variable throttle valve 14b, the raising and lowering speed of the agricultural machine can be set arbitrarily according to the weight of the agricultural machine, etc., thereby preventing the generation of shock when raising and lowering the agricultural machine and the delay in the lowering speed. can be prevented.

Further, when the main switching valve 10 is set to the "hold" position 10b, the first piston 4 of the lifting cylinder device 1 is in a free state between the second piston 5 and the cylinder rond side, and the second piston 5 As a result, the end of the stroke in the shortening direction is determined, and as a result, the agricultural machine becomes free upward from the predetermined plowing depth position determined by the position of the second piston 5.

Therefore, even if there is an obstacle during work with agricultural machinery such as a subsoiler or plow with the main switching valve 10 set to the "hold" position 10b, the agricultural machinery will be lifted by the uplifting force and will be prevented from being subjected to a large load. Agricultural machinery can be protected.

[Brief explanation of the drawing]

Figure 1 is a side view showing the three-point hit device of an agricultural tractor;
FIG. 2 is a conventional hydraulic circuit diagram, and FIG. 3 is a hydraulic circuit diagram showing an embodiment of the present invention. 1 is a lifting cylinder device, 2 is a lift lever, 14b is a variable throttle valve, 16 is a lower link, 17 is a top link,
18 is an adjustment link.

Claims (1)

[Scope of utility model registration request] In a three-point hit device for an agricultural tractor, which is made up of a lower link 16, a top link 17, and an adjustment link 18, and is raised and lowered via a lift lever 2 by telescoping the raising and lowering cylinder device 1, the above-mentioned raising and lowering cylinder The device 1 has a first piston 4 having a piston rod 3 connected to a lift lever 2, and a second piston 5 which is located in a free state on the bottom side by this first piston 4. An intermediate chamber 6 between the two pistons 5 is always connected to the tank side, and between the lifting cylinder device 1 and the hydraulic pressure source 11, the hydraulic source 11 and the bottom side chamber 9 of the lifting cylinder device 1 are connected. The "upper" position 10a communicates the drain circuit with the rod side chamber 8, and the bottom side chamber 9 is closed, and the rod side chamber 8 is connected to the hydraulic source 11.
The main switching valve 10 has a "hold" position 10b in which the rod side chamber 8 and the bottom side chamber 9 communicate with each other and a drain circuit, and a "float" position 10c in which the rod side chamber 8 and the bottom side chamber 9 communicate with the hydraulic power source 11 and the drain circuit.
interposed, and the bottom side chamber 9 of the lifting cylinder device 1
A bottom side chamber 9 is provided between the hydraulic power source 11 and the drain circuit.
and a "lower" position 13a that communicates the drain circuit with the main switching valve 10 and closes the drain circuit from the main switching valve 10, and a "drain" position 13b that closes the bottom side chamber 9 and communicates the drain from the main switching valve 10. A three-point hitch for an agricultural tractor, characterized in that a lowering switching valve 13 is interposed therein, and an elevating response control device using a variable throttle valve 14b is further interposed in the circuit of the bottom side chamber 9 of the elevating cylinder device 1. Device.