JPS62160326A - Boom cylinder driver for oil-pressure shovel - Google Patents

Abstract

PURPOSE:To save energy by reducing the amount of oil to be supplied by a method in which a connection switch valve to switch the oil path of each boom cylinder to a parallel connection and a serial connection is provided, and at the time of boom lowering operation, each cylinder is switched to serial connection. CONSTITUTION:A connection switch valve 208 for boom cylinder is switched to serial connection, and an oil path switch control valve 201 for boom cylinder is operated to the direction of X. Hereupon, working oil of an oil-pressure pump 300 flows through a control valve 201 into the rod side pressure chamber of the boom cylinder to push out oil as many as two-fold from the head side pressure chamber. The oil so pushed out flows by 1/2 each through a switch valve 208 into cylinders 11a and 13a, and oil as many as two-fold is returned through the control valve 201 from the head side pressure chamber to an oil tank 301. Three cylinders 11a, 11b, and 11c are integrally contracted and the lowering operation is made by 1/3 necessary horsepower. The switch valve can thus be miniaturized.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a plurality of boom cylinders that are mechanically connected and driven in parallel, a hydraulic pump, and an oil path from the hydraulic pump to each boom cylinder. The present invention relates to a boom cylinder drive device for a hydraulic excavator, which has a boom cylinder oil passage switching control valve that switches between.

(Prior Art) The hydraulic circuit of a conventional hydraulic excavator with front loader specifications is explained with reference to Fig. 4. (100) is the hydraulic excavator body, (101) is the boom, (102) is the arm, and (103) is the bucket. I”+ (la) is the boom cylinder installed between the hydraulic excavator main body (100) and the boom (101), (2a) is the boom (1)
01) and the arm (102).

(3a) is the arm (102) and the packet (10).
3) Packet cylinder installed between (300)
is the hydraulic pump, (301) is the oil tank, (20
1) is a boom cylinder oil passage switching control valve provided in a hydraulic circuit between the hydraulic pump (300) and the oil tank (301) and the boom cylinder (1a);
(202) is an arm cylinder oil passage switching control valve provided in a hydraulic circuit between the hydraulic pump (300) and the oil tank (301), and the arm cylinder (2a); (203) is the hydraulic pump (2a); 300) and the oil tank (301) and the packet cylinder (3
Excavation with a hydraulic excavator with a loader/front specification is mainly performed using the oil passage switching control valve for the arm cylinder (
202), the hydraulic oil from the hydraulic pump (300) is supplied to the head side pressure chamber of the arm cylinder (2a), the arm cylinder (2a) is operated in the extension direction, and the arm (102) is moved in the forward direction. This is done by operating the In excavation by independent operation of this arm (102), the packet (1
The trajectory of the tip of the arm (102) and the boom (1)
The tip of the packet (103) is excavated in an arc centered at the joint with the packet (103).

(Problems to be Solved by the Invention) However, in actual excavation or loading work using a hydraulic excavator with a loader front specification, the tip of the bucket (103) is often moved linearly. Like this packet (
In order to linearly move the tip of the arm cylinder (103), switch the arm cylinder oil passage switching control valve (202) to transfer hydraulic oil from the hydraulic pump (300) to the arm cylinder (2a).
The same arm cylinder (2) is supplied to the head side pressure chamber of
At the same time, the boom cylinder oil passage switching control valve (201) is switched, and the hydraulic pump (300) is operated in the extension direction.
Supply hydraulic oil from the cylinder to the rod side pressure chamber of the boom cylinder (1a).

It is necessary to operate the boom cylinder (1a) in the retraction direction (to lower the boom (101)). In addition, if necessary, the packet cylinder oil passage switching control valve (203) is switched to supply hydraulic oil from the hydraulic pump (300) to the head side pressure chamber of the packet cylinder (3a). It is also necessary to operate in the direction of contraction.

The lowering operation of the boom (101) includes (■) interlocking with the operation of the arm (102) for linear excavation as described above, and (■) the next operation after dump loading/unloading. There are three cases: (1) returning the packet to the excavation position, and (2) causing the tip of the packet to cut deeply into the ground. Among these, case (■) requires generating a large downward force using large pressure, but (I)
In the case of (If).

Although a sufficient amount of oil is required, the weight of the front section provides sufficient descending speed, and almost no pressure is required.

Now, if the cross-sectional area of the rod side pressure chamber of the boom cylinder (1a) shown in Fig. 5 is (S, ), and the maximum speed of the piston rod (1c) is (V, a, ), then the rod of the boom cylinder (1a) is The flow rate Q of oil flowing into the side pressure chamber is.

Q=S, ・V□8. Also hydraulic pump (300
) is the discharge pressure (Po), then the horsepower required for lowering the boom (101) is:

(Required horsepower) = P0 ・Q...■. In the above equation 0, Q is the piston rod (1
If the speed of c) is constant, it is constant and does not change, but P
o varies greatly depending on operating conditions, which causes the required horsepower to vary significantly. That is, when the boom (101) operates independently, the discharge pressure P0 of the hydraulic pump (300) decreases to almost zero, resulting in a small required horsepower. When excavating by moving the boom (101) and lowering the boom (101),
Hydraulic pump (
300), and reduce this discharge pressure P0 to approximately zero due to the pressure loss of the boom cylinder oil passage switching control valve (201), and supply it to the rod pressure chamber of the boom cylinder (1a). , the required horsepower becomes extremely large. This, combined with the fact that the cross-sectional area of the boom cylinder (1a) is larger than the cross-sectional areas of other cylinders, leads to an increase in unnecessary horsepower and an increase in the size of the hydraulic equipment, making it difficult to save energy.

Conventionally, the following three countermeasures have been proposed to address the above problems, but each has the following drawbacks.

The first is an independent pump system in which a dedicated hydraulic pump is placed in each hydraulic system for the boom cylinder, arm cylinder, and packet cylinder so that the discharge pressure of the hydraulic pump corresponds to the required pressure of each cylinder independently. . With this independent pump system.

Optimal horsepower distribution can be achieved in both independent and linked operations, but the disadvantage is that three large hydraulic pumps with large horsepower generation capacity are required to obtain maximum horsepower during independent operation. There is.

The second is 2. For example, as shown in FIG. 6, a valve (204) is provided in the piping that bypasses the rod side pressure chamber and head side pressure chamber of the boom cylinder (1a), and the head side pressure chamber of the boom cylinder (1a) is A valve (205) is installed in the pipe connecting the chamber and the oil tank, and when the boom is lowered, the valves (204) and (205) are opened while the boom cylinder oil path switching control valve (201) is held in the neutral position. ,
Floating type with boom that can be lowered freely
It is a system. In this floating system,
Since the amount of descent of the boom is controlled by the balance with the reaction force on the bottom of the packet, there was a drawback that necessary control was not possible when excavating in wetlands or when excavating while floating in the air.

Part 3 is configured in the same way as 1, for example, in Figure 6.

When the boom is lowered, the boom cylinder oil passage switching control valve (2
This control system controls the descending speed of the boom by opening the valve (204) and changing the opening area of the valve (205) while holding the boom (01) in the neutral position. This control system is specifically shown in Figure 7 (I), where the boom cylinder (1a)
A switching control valve (207) is provided in the piping that bypasses the rod side pressure chamber and the head side pressure chamber. The same switching control valve (2
07) has the opening characteristics shown in FIG. 7(n) 1 and has a size 9 that allows the maximum flow rate Qmax=Vmax −3a to flow.
That is, the main boom cylinder oil passage switching control valve (20
1) It has the same size as . In this control system, the switching control valve (207) is enlarged. Moreover, it is necessary to select which switching control valve to operate depending on the operating state, which has the disadvantage of complicating the operation.

(Means for Solving the Problems) The present invention addresses the above-mentioned problems, and includes: (1) a plurality of boom cylinders that are mechanically connected and driven in parallel; a hydraulic pump; A boom cylinder drive device for a hydraulic excavator includes a boom cylinder oil passage switching control valve that switches an oil passage to the boom cylinder,
The present invention relates to a boom cylinder drive device characterized by comprising a boom cylinder connection switching valve that switches the oil passages of each boom cylinder between parallel connection and series connection.

The objective is to provide an improved boom cylinder drive device that can achieve energy savings without increasing the size of hydraulic equipment or reducing controllability and operability.

(Function) The boom cylinder drive device of the present invention is configured as described above, and when the boom is lowered, each boom cylinder is connected in series, and the amount of oil supplied from the hydraulic pump is reduced, and the boom is lowered. Achieve time energy savings. Further, the operation control at this time is performed by the main boom cylinder oil passage switching control valve.

(Example) Next, the boom cylinder drive device of the present invention will be explained using an example shown in FIG. 1 (1). (lla) (12a
(13a) are three boom cylinders, each boom cylinder (11a) (12a (13a) having the same length.

One end portion is mechanically connected to the rod-shaped member (15) via the bottle. Also (llb) (12b(13b
) is the same for each boom cylinder (ILa) (12a (13
The piston of a), (llc) (12c (13c) is the piston rod of each boom cylinder (lla) (12a (13a), the same piston rod (llc) (12
c (13c) is also mechanically connected to the rod-shaped member (14) via a pin in the same manner as above. Also (201)
is the oil passage switching control valve for the boom cylinder, (201a) is the operating lever of the oil passage switching control valve (201), (300
) is the hydraulic pump, (301) is the oil tank, (3
a) is a high-pressure oil passage extending from the hydraulic pump (300) to the boom cylinder oil passage switching control valve (201);
3b) is the oil passage switching control valve (201) for the same boom cylinder.
a low pressure oil passage extending from the oil tank (301);
(208) is the connection switching valve for the boom cylinder, and the A port of the boom cylinder connection switching valve (208) is the oil path (3
d) through the boom cylinder oil passage switching control valve (2).
01), and the B boat of the boom cylinder connection switching valve (208) is connected to the F port of the boom cylinder oil passage switching control valve (201) via the oil passage (3e).
They are connected to each other. (208a) is the operation lever of the connection switching valve (208), and (16a) is the oil that connects the rod side pressure chamber of the boom cylinder (1la) and the D port of the boom cylinder connection switching valve (20B). an oil passage (16b) connecting the head side pressure chamber of the boom cylinder (lla) and the oil passage (3d);
17a) is an oil passage connecting the rod side pressure chamber of the boom cylinder (12a) and the oil passage (3e);
) is an oil passage connecting the head side pressure chamber of the boom cylinder (12a) and the C port of the boom cylinder connection switching valve (20B), and (18a) is the oil passage connecting the rod side pressure chamber of the boom cylinder (13a). An oil passage that connects with the oil passage (16a).

(18b) is an oil passage connecting the head side pressure chamber of the boom cylinder (13a) and the oil passage (16b).

Next, the operation of the boom cylinder drive device shown in FIG. 1(I) will be specifically explained. First, the boom lowering action during normal operation will be explained with reference to FIG.

The boom cylinder connection switching valve (20B) is kept in the illustrated parallel connection state, and the boom cylinder oil passage switching control valve (201) is operated. At this time, the three boom cylinders (lla) (12a (13a) operate in parallel in the extending or retracting direction. At this time, the amount of oil flowing into the boom cylinder connection switching valve (208) is as follows. Each boom cylinder (lla) (12a (13
If the total cross-sectional area of the rod pressure chambers in a) is Sa, the total cross-sectional area of the head-side pressure chambers is sb, and 5a=Sb, then each boom cylinder (lla) (12a) (13a) each rod-side pressure chamber, and What is the cross-sectional area of the head side pressure chamber?

1/3 S a , l/3 S b =2/3 S
Become a. For this reason.

For maximum cylinder operating speed Vmax.

What is the flow rate between A and C ports?

Q+ max = 1/3 S b ・Vmax = 2/
3 S a-VmaX ・・・・・・・・・・・・■ The flow rate between the B-D ports is.

Qz wax =2 XI/3 Sa −Vmax
=2/3 S a −Vmax・・・・・・・・・・・・
■ Become.

Next, the boom lowering action during energy-saving operation will be explained using Fig. 3. First, the boom cylinder connection switching valve (20
B) in the direction shown, and then operate the boom cylinder oil passage switching control valve (201) in the X direction. As a result, the hydraulic oil from the hydraulic pump (300) flows from the G-F port of the boom cylinder oil passage switching control valve (201) through the oil passage (17a) into the rod side pressure chamber of the boom cylinder (12a). Then, the piston (12b) and the piston rod (12c) move to the right (in the direction of contraction), and 5b=Sa is removed from the head side pressure chamber of the boom cylinder (12a).
twice that amount of oil is pushed out. This oil flows through the oil line (
17b) to the other boom cylinder (lla
) 1/2 of the oil flows into the rod side pressure chamber of (13a), and twice as much oil is pushed out from the head side pressure chamber of each boom cylinder (lla) (13a). This oil returns to the oil tank (301) from the oil passages (16b) and (18b) through the E port and H port of the boom cylinder oil passage switching control valve (201).

This results in three boom cylinders (lla) (12
a (13a) are integrally operated in the retracting direction by the required length to lower the boom. At this time, the amount of oil supplied from the hydraulic pump (300) is relative to the maximum boom cylinder speed Vmax.

Q:+max=1/3 Sa-Vmax...
・−・・■ Therefore, the required horsepower is.

(Required horsepower) = Po ・Qa max = 1/3
Po. Moreover, in this case, the amount of oil flowing between ports C and D of the boom cylinder connection switching valve (208) is as follows.

Q4 max = 2 ・1/3 Sa ・Vmax =
2/3 Sa ・vIIIaxI11φ... Becomes 1 pot ■. According to the above formula 000, the maximum flow rate of the connection switching valve (208) for the boom cylinder is + 2/3 Sa
The conventional switching control valve (20
Compared to 7), the switching valve can be made smaller and the 0N
-OFF operation is possible, and from this point of view, miniaturization and structural simplification can be further promoted.

Also, the operability and controllability of the boom cylinder drive device will be explained. During normal operation and energy saving operation,
ON-OF of boom cylinder connection switching valve (208)
The boom can be operated by F operation, improving operability and controllability. In addition, the boom cylinder connection switching valve (208) is not only a manual operation system, but also a manual operation system.
It can also be applied to automatic operation systems with computers, etc., and is effective in realizing energy-saving hydraulic excavators that can be automatically controlled.

(Effects of the Invention) The boom cylinder drive device of the present invention is configured as described above, and when the boom is lowered, each boom cylinder is switched to a series connection state to reduce the amount of oil supplied from the hydraulic pump. Furthermore, since the operation control at this time is performed by the main boom cylinder oil passage switching control valve, energy saving can be achieved without increasing the size of the hydraulic equipment or reducing controllability and operability.

[Brief explanation of drawings]

FIG. 1(I) is a hydraulic circuit diagram showing an embodiment of the boom cylinder drive device according to the present invention, FIG. 1(II) is an explanatory diagram showing the opening characteristics of the boom cylinder connection switching valve, and FIG. Fig. 3 is an explanatory diagram of the operation of the boom cylinder drive device during normal operation, Fig. 3 is an explanatory diagram of the operation during energy-saving operation, Fig. 4 is a side view showing the basic configuration of the hydraulic excavator, and Fig. 5 is the boom of a conventional hydraulic excavator. A hydraulic circuit diagram showing a cylinder drive device, Fig. 6 is a hydraulic circuit diagram showing another conventional example, and Fig. 7 (1
) is a hydraulic circuit diagram showing yet another conventional example. FIG. 7 (II) is an opening characteristic diagram of the switching control valve used in the boom cylinder drive device. (lla) (12a) (13a)...Boom cylinder, (201)...Oil passage switching control valve for boom cylinder, (208)...Connection switching valve for boom cylinder, (300)...Hydraulic pressure pump. Sub-Agent Patent Attorney Okamoto (2 persons) Figure 2 Figure 3 Figure 5 Figure 6 1 Mountain 1a. Figure 7 (1)

Claims (1)

[Claims] A boom for a hydraulic excavator having a plurality of boom cylinders that are mechanically connected and driven in parallel, a hydraulic pump, and a boom cylinder oil passage switching control valve that switches oil passages from the hydraulic pump to each boom cylinder. A boom cylinder drive device, characterized in that the boom cylinder drive device includes a boom cylinder connection switching valve that switches oil passages of each boom cylinder between parallel connection and series connection.