JPS624259B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic pressure control device for controlling the operation of a PTO clutch provided in a mobile agricultural machine such as a tractor for extracting operating power.

When driving the working part of a working machine connected to a mobile agricultural machine, if the working machine is rotary,
It is desirable to supply pressure oil to the clutch cylinder at one time to prevent the so-called half-clutch state when the PTO clutch is connected.
For example, in the case of a working machine such as a mower, which has a large inertia of the working part, it is desirable to gradually connect the PTO clutch so as to maintain the half-clutch state for a while. When connected to the power transmission system, a large impact force acts on the power transmission system due to the large inertia of the working part, causing problems such as the safety pin breaking. Therefore, in this invention, the hydraulic oil for the PTO clutch cylinder is supplied while the hydraulic pressure is gradually increasing, thereby preventing the generation of large impact force and preventing damage to various parts of the power transmission system. The construction of this system will be explained based on one embodiment shown in the drawings. As shown in FIG. is connected to the PTO clutch switching valve 4, and pressure oil is returned to the tank 2 by switching the PTO clutch switching valve 4, or
It is provided so that pressure oil is supplied to the PTO clutch cylinder 5 via a throttle 6.

Therefore, in this invention, as shown in FIG. 2, a pressure increase control valve 7 is connected between the throttle 6 and the PTO clutch cylinder 5. A return port 10 that returns the pressure oil from the oil passage 9 to the tank 2 and a closing part 11 that immediately stops the pressure oil from returning to the tank 2 are provided. The valve chamber 15 on the return prevention side is supplied via the valve chamber 13 on the side and the throttle 14, and the spring 16
The valve body 12 is pushed toward the valve chamber 13 and energized to assist the action of the pressure oil. The pressure oil supplied to this other valve chamber 15 is 1
The valve stem 20 of the hour relief valve 17 is also provided so as to be supplied to the hour relief valve 17 and is pushed by the pressure oil against the spring 19 until it comes into contact with the stopper 18. The position of this stopper 18 is configured to be movable and adjustable by an adjusting screw 22 which is rotated by the rotating operation of an adjusting lever 21.

And when connecting the PTO clutch
If the PTO clutch switching valve 4 is switched to the clutch connection position where pressure oil from the relief valve 3 is supplied to the boost control valve 7 as shown in FIG.
The pressure oil that has passed through is supplied to the return side valve chamber 13 of the boost control valve 7, and at the same time is also supplied to the return prevention side valve chamber 15 and the valve chamber 23 of the one-hour relief valve 17 through the throttle 14. However, since it passes through the throttle 14, the amount of pressure oil flowing into the valve chambers 15 and 23 decreases, and the valve body 12 moves toward the valve chamber 15.
For this reason, the return port 10 opens to the oil passage 9, and most of the pressure oil from the pump 1 returns to the tank 2, so the PTO clutch cylinder 5
A small amount of pressure oil will be supplied to the

Then, after a while, the valve chamber 15 is filled with pressure oil and is energized by the spring 16, pushing the valve body 12 back toward the valve chamber 13, so that the return port 10 is removed from the oil passage 9 and the blocking portion 11 is oil passage 9 and valve chamber 13
The pressure oil from the pump 1 is not returned to the tank 2, but is mainly supplied to the PTO clutch cylinder 5, and some of it is also supplied to the valve chamber 15 via the throttle 14. The oil pressure inside the cylinder 5 will rise. Since the pressure oil having the same pressure as this rising oil pressure also acts on the valve chamber 13 at the same time, the pressure in the valve chamber 13 is greater than the pressure in the valve chamber 15 that is throttled and supplied by the throttle 14. Therefore, the valve body 12 is connected to the valve chamber 15.
, the return port 10 opens to the oil passage 9, and the pressure in the valve chamber 13 begins to decrease rapidly. Then, the pressure in the valve chamber 15 and the spring 16 push the valve body 12 back toward the valve chamber 13, preventing oil from returning to the tank 2 and increasing the pressure of the pressure oil in the PTO clutch cylinder 5. As a result,
In this way, by gradually moving the valve body 12 left and right, a part of the pressure oil from the pump 1 can be released to the tank 2, or while being supplied into the PTO clutch cylinder 5, the pressure in the PTO clutch cylinder 5 can be adjusted to the fourth position. The range of the solid line pressure curve F ₁ in the pressure rise diagram in Fig.
It will rise slowly as shown by R ₁ .

A part of the pressure oil supplied into the valve chamber 15 during this pressure rise is transferred to the valve chamber 23 of the one-hour relief valve 17.
As a result, the force that moves the valve body 12 toward the valve chamber 13 becomes weaker, and the time it takes for the pressure oil in the valve chamber 13 to return to the tank 2 becomes longer. The rate of increase in oil pressure is gradual as in the range _R1 mentioned above. Then, the valve stem 20 of the 1 o'clock relief valve 17 is moved to the stopper 1.
8, the hydraulic pressure in the PTO clutch cylinder 5 reaches the pressure _P1 shown in FIG. Because of this, the PTO
The rate of pressure increase in the clutch cylinder 5 increases as shown in the range _R2 in FIG.

When the pressure inside the PTO clutch cylinder 5 reaches a predetermined pressure _P2 set by the relief valve 3, the relief valve 3 returns the pressure oil from the pump 1 to the tank 2, and from then on, the pressure oil from the pump 1 is returned to the tank 2. _The pressure of
The configuration is such that the rise is gradual in R ₁ and somewhat steep in range R ₂ .

The pressure regulating valve box 24, which houses the above-mentioned pressure increase control valve 7 and one-hour relief valve 17 as shown in FIG. As shown in FIG. 3, the adjusting lever 21 of the one-hour relief valve 17 is mounted jointly and protrudes outside the pressure regulating valve box 24.
By rotating this adjustment lever 21 and adjusting the movement of the stopper 18, the valve stem 20 moves to the stopper 18.
For example, if the elapsed time until contact is made longer, the above-mentioned range R ₁ will increase, the pressure oil in the PTO clutch cylinder 5 will rise more slowly, and the rotational speed of the PTO shaft will also rise. It is rather lenient. Further, in FIG. 3, reference numeral 26 is a switching arm of the PTO clutch switching valve 4, which is switched by a clutch operation lever 27, and the pressure regulating valve box 24 is mounted on the transmission case 28. has been done. Further, as shown in FIG. 1, the pressure oil of the pump 1 is also supplied to the cylinder 31 of the lift mechanism 30 via the control valve 29.

Since the hydraulic pressure control device for the PTO clutch according to the present invention is constructed as described above, when the PTO clutch switching valve 4 is switched to the clutch connection position, the valve body 12 of the boost control valve 7 moves left and right in small increments. Since the operation of moving the pump 1 to release the pressure oil to the tank 2 and the operation of supplying it to the PTO clutch cylinder 5 are repeated alternately, the pressure increase in the PTO clutch cylinder 5 is gradually caused by the release operation to the tank 2. This is the result.

The pressure oil supplied to the valve chamber 15 to interrupt this relief operation is supplied to the 1 hour relief valve 17.
As long as the one-hour relief valve 17 continues to function, the pressure inside the PTO clutch cylinder 5 will rise very slowly, and the pressure rise shown in FIG. control valve 7
When compared with the dotted line pressure curve F ₂ showing the pressure increase in the PTO clutch cylinder 5 when using a conventional flow divider without the 1-hour relief valve 17, the pressure curve when using the inventive device As shown in F ₁ , this PTO
The rotational speed of the PTO shaft to which rotational force is transmitted by the clutch piston 27 of the clutch cylinder 5 is a rotational speed curve S1 using the device of the present invention, compared to a rotational speed curve _S2 using the conventional flow divider shown in _FIG . shows a gradual rise.

Therefore, according to the device of the present invention, by slowing down the rise in the pressure oil supplied to the PTO clutch cylinder when driving the working part of the working machine,
Since the rotation speed of the PTO shaft can be gradually increased, the impact force acting on the power transmission system is sufficiently alleviated when driving a working machine such as a mower, which has a large inertia of the working part. I was able to
We were able to effectively prevent wear and tear on each part.

[Brief explanation of the drawing]

Fig. 1 is a hydraulic circuit diagram of the device according to the invention, Fig. 2 is a vertical sectional view of a pressure regulating valve box used in the above device, Fig. 3 is a side view showing the installation state of the above device, and Fig. 4 is a
Pressure rise diagram of hydraulic pressure in PTO clutch cylinder,
Figure 5 is a diagram showing the increase in rotational speed of the PTO shaft. Explanation of symbols, 1...pump, 2...tank, 3...
...Relief valve, 4...PTO clutch switching valve, 5
...PTO clutch cylinder, 6, 14... Throttle, 7... Boost control valve, 8, 9... Oil passage, 10... Return port, 11... Blocking part, 12
... Valve body, 13, 15, 23 ... Valve chamber, 16, 1
9... Spring, 17... 1 o'clock relief valve, 18... Stopper, 20... Valve stem, 21... Adjustment lever, 2
2... Adjustment screw, 24... Pressure regulating valve box, 25... Flow divider, 26... Switching arm, 27... Clutch operation lever, 28... Mission case,
29...Control valve, 30...Lift mechanism, 31...Cylinder, _F1 , _F2 ...Pressure curve,
P ₁ , P ₂ ... pressure, R ₁ , R ₂ ... range, S ₁ , S ₂ ...
Rotational speed curve.

Claims (1)

[Claims] 1. By introducing the working pressure oil to be supplied to the PTO clutch cylinder into the return side valve chamber of the boost control valve and the return prevention side valve chamber which has a throttle, the pressure on the return side increases as the hydraulic pressure of the pressure oil increases. The pressure increase control valve is configured so that these operations are repeated alternately to return the pressure oil in the valve chamber to the tank or stop this return operation, and the pressure in the PTO clutch cylinder reaches the set value. The PTO clutch hydraulic control system is equipped with a 1-hour relief valve that releases the pressure oil in the valve chamber on the return prevention side until the return is stopped.