JP2000266004A - Controlling method for hydraulic cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a droop trouble possible to be generated at the time of controlling a single rod type of hydraulic cylinder. SOLUTION: Hydraulic fluid supplied into one of a rod side room 34 and a head side room 36 of a single rod type of hydraulic cylinder 11 from a pump 13 and discharged from the other to a tank 15 is controlled by a bridge circuit 18 formed with two meter-in paths 21 and 22 and two meter-out 23 and 24. Expanding speed of the hydraulic press cylinder 11 are regenerated and increased by remaining the two meter-out paths closed and opening the two meter-in paths 21 and 22. In this case, the meter-in path 22 of the lead side of the hydraulic cylinder 11 is controlled to open proceeding the meter-in path 21 of the rod side in terms of time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic cylinder control method for controlling a single rod type hydraulic cylinder.

[0002]

2. Description of the Related Art FIGS. 12 to 21 show a control circuit having a bridge structure for controlling a conventional single-rod type hydraulic cylinder (hereinafter simply referred to as "cylinder") 11, and characteristic diagrams of respective parts thereof. Note that the characteristic diagrams arranged around the circuit diagram of FIG. 12 show the characteristics of the corresponding portions in the circuit corresponding to the numbers in parentheses attached outside the frames.

In this control circuit, a tank 15 is connected via a bypass passage 14 to a discharge port of a variable displacement pump 13 capable of variably controlling a discharge flow rate by a swash plate 12.
A bridge circuit 18 is connected via a pump line 17 having a check valve 16.

The bridge circuit 18 is formed by two meter-in passages 21 and 22 connected to the pump line 17 and two meter-out passages 23 and 24 connected to the meter-in passages 21 and 22, respectively. ing.

[0005] These meter-out passages 23 and 24 are connected to a tank line 25, and are connected to the respective meter-out passages 23 and 24.
Check valves 24 and 27 for makeup for replenishing the working oil as the working fluid from the tank line 25 to the negative pressure generating portion in the circuit are connected to the 24 in parallel.

A passage 31 drawn out between the meter-in passage 21 and the meter-out passage 23 shown above the bridge circuit 18 is a chamber on the side where the rod 33 is located relative to the piston 32 of the single rod type cylinder 11. (Hereinafter referred to as a “rod side chamber”), and a passage 35 drawn out from between the meter-in passage 22 and the meter-out passage 24 is a cylinder.
It is connected to a chamber 36 (hereinafter, referred to as a “head-side chamber”) located on the head side of the eleventh piston 32.

In the cylinder 11 on one rod side, the pressure receiving area A36 facing the head side chamber 36 is larger by the cross-sectional area of the rod 33 than the pressure receiving area A34 facing the rod side chamber 34 of the piston 32.

The bypass passage 14, the meter-in passage 21,
The throttle opening 22 and the meter-out passages 23 and 24 are provided with variable throttle means such as a spool valve or a poppet valve whose opening area can be variably controlled by electromagnetic means or pilot hydraulic means. In the case of electromagnetic means, control is performed directly by the output electric signal, and in the case of pilot hydraulic means, control is performed by a pilot pressure signal via electro-hydraulic conversion means.

Then, the hydraulic oil supplied from the pump 13 to one of the rod side chamber 34 and the head side chamber 36 of the single rod type cylinder 11 and discharged from the other to the tank 15 is
Control is performed by a bridge circuit 18 formed by the two meter-in paths 21 and 22 and the two meter-out paths 23 and 24.

Normally, to extend the cylinder 11, the bypass passage 14 is closed, the meter-in passage 22 on the head side of the cylinder 11 is opened, and the meter-in passage 21 on the rod side is opened.
Is closed, the rod-side meter-out passage 23 is opened, and the head-side meter-out passage 24 is closed.

Further, in order to contract the cylinder 11, the bypass passage 14 is closed, the meter-in passage 21 on the rod side of the cylinder 11 is opened, and the meter-in passage 22 on the head side is opened.
Is closed, and the meter-out passage 24 on the head side is opened, and the meter-out passage 23 on the rod side is closed.

In such a control system, the two meter-in passages 21 and 22 may be opened while the two meter-out passages 23 and 24 are closed in order to further increase the extension speed of the cylinder 11. This is called a reproduction function.

In the case of this regenerating function, the effective pressure receiving area is reduced to the pressure receiving area difference between the head side and the rod side of the cylinder 11, so that the extension speed of the cylinder 11 is increased. In this case, return oil from the rod side merges with the pump discharge flow rate via the meter-in passage 21 and is further supplied to the head-side chamber 36 of the cylinder 11 via the meter-in passage 22.

For this purpose, the rod-side chamber 34 of the cylinder 11
Must be higher than the pressure P36 on the head side.

[0015]

However, when the cylinder 11 is extended while the two meter-in passages are open in a state where a load such as lifting the load 37 is applied,
A simulation result as shown in FIG. 12 is obtained.

In particular, as can be seen from the opening degree characteristics of the two meter-in passages 21 and 22 shown in FIGS.
Since the two meter-in passages 21 and 22 begin to open at the same timing, the initial closing oil in the head-side chamber 36 reduces the compressibility of oil in the rod-side chamber 34 and the passage 31 and the expansion of the pipeline in the rod-side chamber 34 and the passage 31 which were initially low in pressure. As a result, a blow-through to the low-pressure rod-side chamber 34 occurs, and as shown in FIGS.

The present invention has been made in view of the above points, and has as its object to prevent a droop problem that may occur when controlling a single rod type hydraulic cylinder.

[0018]

According to a first aspect of the present invention, a hydraulic fluid is supplied from a pump to one of a head side and a rod side of a single rod type hydraulic cylinder and discharged to a tank from the other side. With two meter-in passages and two
A hydraulic cylinder control method controlled by a bridge circuit formed by two meter-out passages, wherein the two meter-in passages are closed and two meter-in passages are opened to increase the extension speed of the hydraulic cylinder. In this case, the hydraulic cylinder control method is such that the meter-in passage on the head side of the hydraulic cylinder is opened ahead of the meter-in passage on the rod side of the hydraulic cylinder ahead of time.

Then, the hydraulic fluid discharged from the pump is first supplied to the head side of the hydraulic cylinder, and the hydraulic cylinder is about to expand. At that time, the rod side, which is still closed, suddenly increases from low pressure. Pressure exceeds head side pressure. In this state, since the meter-in passage on the rod side is opened with a time delay, the hydraulic fluid flows from the rod side, which has been on the high pressure side, to the head side on the low pressure side, and the initial confining liquid on the head side blows off to the rod side. Therefore, the occurrence of a droop in which the hydraulic cylinder shrinks is prevented.

According to a second aspect of the present invention, there is provided the hydraulic cylinder control method for controlling the flow rate of the hydraulic fluid discharged from the pump to be low in the hydraulic cylinder control method according to the first aspect.

In combination with the preceding opening of the meter-in passage on the head side, while suppressing the droop of the hydraulic cylinder, a sudden increase in the pressure on the rod side and the head side of the hydraulic cylinder is prevented, and an appropriate pressure is obtained. The life of the hydraulic cylinder is not impaired.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to FIGS.
This will be described with reference to the embodiment shown in FIG. The control circuit of the bridge configuration for controlling the single rod type hydraulic cylinder (hereinafter simply referred to as “cylinder”) 11 is the same as the conventional example shown in FIG. The description is omitted here.

FIG. 1 shows a simulation result of a cylinder control method for solving the conventional problems together with a control circuit similar to the conventional one. Each characteristic diagram arranged around the circuit diagram of FIG. 1 indicates the characteristic of the corresponding portion in the circuit corresponding to the number in parentheses attached outside the frame.

In such a control system, in order to increase the extension speed of the cylinder 11, two meter-out passages 23,
To obtain a regeneration function of increasing the extension speed of the cylinder 11 by opening the two meter-in passages 21 and 22 while keeping the 24 closed, the meter-in passage 22 on the head side of the cylinder 11 is connected to the rod side of the cylinder 11 The meter-in passage 21 is opened earlier in time.

For example, the meter-in passage 21 on the rod side
The meter-in passage 22 on the head side opens at a time of 0.2 seconds as shown in FIG. 5, while the head-side meter-in passage 22 opens at a time of 0.6 seconds as shown in FIG. That is, in this example, the meter-in passage 22 on the head side is 0.6-0.2 = 0.4.
It opens ahead of the meter-in passage 21 on the rod side for seconds. Note that this time difference is not specified, and an optimum value suitable for the system can be selected.

As a result, the hydraulic fluid discharged from the pump 13 as the hydraulic fluid is first supplied to the head side chamber 36 of the cylinder 11, and the cylinder 11 is about to expand. Is suddenly pressurized from a low pressure, and enters into a region exceeding the head side pressure by an amount corresponding to the cross sectional area of the rod 33 where the pressure receiving area of the piston 32 on the rod side is smaller.

In this state, since the meter-in passage 21 on the rod side is opened with a time delay as described above, the hydraulic oil flows from the rod side on the high pressure side to the low pressure head side, and the initial closing oil on the head side. Does not flow through to the rod side, and no droop occurs when the cylinder 11 contracts.

That is, the rod side pressure P34 becomes the head side pressure P
Since it is higher than 36, the oil from the rod side joins the pump supply oil and is supplied to the head side.

In this case, if the flow rate of the hydraulic oil discharged from the pump 13, that is, the pump discharge amount is larger than necessary, FIG.
As shown on the right side, both the rod-side pressure P34 and the head-side pressure P36 generate extremely high pressures, which may shorten the life of the cylinder 11.

To cope with this, in addition to the control method shown in FIG. 1, as shown in FIG.
By controlling the regulator 12 (not shown) to further limit the pump discharge amount as shown in FIG. 6, the pump discharge amount is controlled to be appropriately low.

Then, the meter-in passage on the head side described above.
Combined with the advance of the opening of 22, while suppressing the droop generation of the cylinder 11, the sudden pressure increase on the rod side and the head side of the cylinder 11 is prevented and the pressure is moderated, so that
The life of the cylinder 11 is not impaired.

FIG. 3 shows the change over time in the opening area of the bypass passage 14 shown in FIGS. 1 and 2. FIG. 4 shows the opening area of the rod-side meter-in passage 21 shown in FIGS. FIG. 5 shows the change over time of the opening area of the head side meter-in passage 22 shown in FIGS. 1 and 2, and FIG. 6 shows the change over time of the discharge amount of the pump 13 shown in FIG. FIG. 7 shows the change over time of the discharge pressure of the pump 13 shown in FIG. 2, FIG. 8 shows the change over time of the pressure of the rod side chamber 34 of the cylinder 11 shown in FIG. FIG. 10 shows the change over time in the pressure of the head side chamber 36 of the cylinder 11 shown in FIG. 2, and FIG. 10 shows the piston 11 of the cylinder 11 shown in FIG.
FIG. 11 shows the change over time in the moving speed of the rod 32 and the rod 33.
2 shows the change over time of the strokes of the piston 32 and the rod 33 of the cylinder 11 shown in FIG.

[0033]

According to the first aspect of the invention, since the meter-in passage on the head side of the hydraulic cylinder is opened ahead of the meter-in passage on the rod side of the cylinder in time, the pump is discharged from the pump. The hydraulic fluid is first supplied to the head side of the hydraulic cylinder, and the hydraulic cylinder tries to expand, but the rod side that is closed is suddenly pressurized from a low pressure to exceed the head side pressure, and in this state, Since the meter-in passage on the rod side opens with a delay, the hydraulic fluid flows from the rod side on the high pressure side to the head side on the low pressure side, and the initial closing liquid on the head side does not blow through to the rod side, and the cylinder Can prevent the occurrence of droop.

According to the second aspect of the present invention, by controlling the flow rate of the hydraulic fluid discharged from the pump to be low, the droop generation of the hydraulic cylinder can be prevented in conjunction with the preceding opening of the meter-in passage on the head side. While holding down, it is possible to prevent an abrupt increase in pressure on the rod side and the head side of the hydraulic cylinder and moderate the pressure, thereby preventing the life of the hydraulic cylinder from being shortened.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a hydraulic cylinder control method according to the present invention, and shows a simulation diagram when a head side of two meter-in passages is opened ahead of a rod side together with a control circuit diagram. FIG.

FIG. 2 is a diagram showing a simulation diagram together with a control circuit diagram when horsepower is further limited to pump discharge oil under the conditions shown in FIG. 1;

FIG. 3 is a characteristic diagram showing a change in the opening of a bypass passage 14 in FIGS. 1 and 2;

FIG. 4 is a rod-side meter-in passage 21 in FIGS. 1 and 2;
FIG. 4 is a characteristic diagram showing a change in the aperture of FIG.

FIG. 5 is a head-side meter-in passage 22 in FIGS. 1 and 2;
FIG. 4 is a characteristic diagram showing a change in the aperture of FIG.

FIG. 6 is a characteristic diagram showing a change in a discharge amount of a pump 13 in FIG. 2;

FIG. 7 is a characteristic diagram showing a change in discharge pressure of a pump 13 in FIG.

8 is a characteristic diagram showing a change in rod-side pressure of a cylinder 11 in FIG.

FIG. 9 is a characteristic diagram showing a change in head side pressure of a cylinder 11 in FIG. 2;

FIG. 10 is a characteristic diagram showing a change in speed of a cylinder 11 in FIG.

FIG. 11 is a characteristic diagram showing a change in stroke of a cylinder 11 in FIG.

FIG. 12 is a diagram showing a conventional simulation diagram showing a cylinder droop problem when two meter-in passages are simultaneously opened together with a control circuit diagram.

FIG. 13 is a characteristic diagram showing a change in the opening of a bypass passage in FIG.

FIG. 14 is a characteristic diagram showing a change in the opening of the rod-side meter-in passage 21 in FIG.

FIG. 15 is a characteristic diagram showing a change in the opening of the head side meter-in passage 22 in FIG.

FIG. 16 is a characteristic diagram showing a change in the discharge amount of the pump 13 in FIG.

FIG. 17 is a characteristic diagram showing a change in discharge pressure of a pump 13 in FIG.

FIG. 18 is a characteristic diagram showing a change in rod-side pressure of the cylinder 11 in FIG.

FIG. 19 is a characteristic diagram showing a change in head-side pressure of a cylinder 11 in FIG.

FIG. 20 is a characteristic diagram showing a change in speed of a cylinder 11 in FIG.

FIG. 21 is a characteristic diagram showing a change in stroke of a cylinder 11 in FIG.

[Explanation of symbols]

 11 Hydraulic cylinder 13 Pump 15 Tank 18 Bridge circuit 21, 22 Meter-in passage 23, 24 Meter-out passage 34 Rod side chamber 36 Head side chamber

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Justice Onda 4-10-1, Yoga, Setagaya-ku, Tokyo New Caterpillar Mitsubishi Co., Ltd. F-term (reference) 3H089 AA22 AA23 AA90 BB30 CC01 DA03 DB14 EE31 GG02

Claims (2)

[Claims] A hydraulic fluid supplied from a pump to one of a head side and a rod side of a single rod type hydraulic cylinder and discharged from the other side to a tank passes through two meter-in passages and two meter-out passages. A hydraulic cylinder control method controlled by a formed bridge circuit, wherein the two meter-in passages are closed and two meter-in passages are opened to increase the extension speed of the hydraulic cylinder. A hydraulic cylinder control method characterized in that the head-side meter-in passage is controlled to open earlier in time than the rod-side meter-in passage. 2. The hydraulic cylinder control method according to claim 1, wherein the flow rate of the hydraulic fluid discharged from the pump is controlled to be low.