JPH0443876A - Output controller in hydraulic device of construction machine - Google Patents

Abstract

PURPOSE:To reduce load fluctuations so as to make effective use of motive power without wasting the same by combining a fixed displacement pump and a variable displacement pump with each other simply by use of a control piston. CONSTITUTION:A control piston 6 slidably inserted into a cylinder 7 is connected to each variable displacement pump 1, 2 via a connecting rod 60 in such a manner that the actuation of fluctuating discharge pressure is carried out by movement of the control piston 6. Each spring 61, 62 for pushing the control piston 6 back in the direction in which to increase the discharge pressure of each variable displacement pump 1, 2 is connected to the control piston 6 and small-diameter plungers 80, 81, 82 provided by a number corresponding to the total number of the variable displacement pumps 1, 2 and fixed displacement pumps 4 which are combined with one another on the opposite side of the connecting rod 60 are connected in parallel, to each other and the cylinder 7 is provided with cylinder portions 71, 72, 73 having respective plungers 80, 81, 82 slidably inserted into their respective end portions each of which is opposite to the connecting rod 60, and pilot circuits 10a, 20a, 40a are connected to the respective cylinder portions 71, 72, 73.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an output control device for controlling the output of a plurality of hydraulic pumps in a hydraulic system of a construction machine such as a power shovel in which a single prime mover drives a plurality of hydraulic pumps. This is related to improvements.

Construction machinery that uses a hydraulic transmission system, such as a power shovel, is configured to have multiple hydraulic pumps driven by a single prime mover, and each hydraulic pump is connected to a separate hydraulic actuator. There are cases.

In this case, in order to minimize the output of the prime mover that drives the hydraulic pump, the hydraulic circuit is configured to drive each hydraulic actuator using two variable displacement pumps, but three In order to improve operability when hydraulic actuators are operated simultaneously, there are two methods: one uses a control valve that divides the pressure oil from two hydraulic variable displacement pumps into three, and the other uses three variable displacement pumps. However, these methods have the problem of increasing costs.

As a countermeasure to this problem, as described in Japanese Patent Publication No. 58-9277, one fixed displacement pump is added to the two variable displacement pumps, and they are assembled using a fixed throttle, a variable throttle, and a control piston. There is a means for controlling the total output (pressure x flow rate) of these three hydraulic pumps to be approximately constant by combining them. However, as shown in FIG.
Three fixed throttles 3 provided at the pilot circuits 10a and 20a, and variable throttles 5 and 5 whose throttle areas increase and decrease in inverse proportion to the discharge pressure of the fixed capacity pump 4 provided in the pilot circuits 10a and 20a,
A control piston 6 which operates to vary the discharge amount of the variable displacement pumps 1 and 2 with the pressure of the pyro-circuits 10a and 20a between the fixed orifices 3 and 5 and the variable orifices 5 and 5 is installed. However, there is a problem that the control means is complicated and the cost is unavoidable.

The present invention has been made in order to solve these problems occurring in conventional means, without using a fixed throttle or a variable throttle whose throttle area increases or decreases in inverse proportion to the discharge pressure of a fixed capacity pump. The purpose of the present invention is to provide a new means capable of controlling a combination of a fixed displacement pump and a variable displacement pump using only a control piston so that fluctuations in the sum of their outputs can be suppressed to less than 50%.

In the present invention, as means for achieving this object, one or more variable displacement pumps and one
One or more fixed displacement pumps are connected so that they are driven at a constant rotation speed by a single common prime mover, and each discharge circuit of the variable displacement pump and fixed displacement pump is provided with a separate pilot circuit. , the variable displacement pump has a control piston that can be slidably inserted into the cylinder.
The control piston is connected via a connecting loft so that the movement of the control piston causes the discharge pressure to vary, and the control piston is connected to a spring that pushes back in a direction to increase the discharge pressure of the variable displacement pump. A number of small diameter plungers corresponding to the total number of the variable displacement pump and fixed displacement pump combined on the side opposite to 2F are connected in parallel, and the cylinder has a connecting rod at the end opposite to the connecting rod. The present invention proposes an output control device for a hydraulic system for construction machinery, which is provided with a cylinder portion into which the plunger is slidably inserted, and the aforementioned pilot circuits are individually connected and communicated with the cylinder portions.

Next, embodiments will be described in detail with reference to the drawings. Note that the same reference numerals in the drawings are used for constituent members having the same effect as those of the previous means.

FIG. 2 is an exploded view of an output control device for a hydraulic pump for construction machinery in which the present invention can be implemented.
Variable displacement pumps 4 are connected in parallel to each other and are driven by the engine E, variable displacement pumps 1 and 2.
In addition, a fixed displacement pump is arranged in parallel to be driven by the engine E, and 6 indicates a control piston connected to the variable displacement pumps 1 and 2 so as to vary the discharge amount of the variable displacement pumps 1 and 2.

The variable displacement pump 1 fist 2 and the fixed displacement pump 4 have a pilot circuit 1 in their respective discharge circuits 10, 20, and 40.
0ae20a*40a is branching.

The control piston 6 is slidably inserted into a cylinder 7 mounted on the body of the construction machine by supporting the variable displacement pump 1.2, and a connecting rod 60 is attached to one end of the control piston 6.
are connected to each other, and the outer end of the connecting rod 60 protruding from the opening opened at the end W170 on one end side of the cylinder 7 is connected to the respective variable operating parts of the variable displacement pumps 1 and 2 described above. The displacement of the variable displacement pumps 1 and 2 is varied by the sliding movement of the control piston 6. The control piston 6 is moved by the springs 61-62 interposed between the control piston 6 and the end wall 70 at one end of the cylinder 7 to move the variable displacement pump 1/2 to the side where its discharge amount increases. It's a boost. Further, the control piston 6 has three plungers 80, 81-82 at the end opposite to the side to which the connecting rod 60 is connected, the axial direction of which is aligned with the axial direction of the control piston 6. With attitude.

It is connected in parallel with the third gear. The cross-sectional areas of these plungers 80, 81, and 82 may be made equal if the capacities of the fixed-capacity pump 4 and variable-capacity pumps 1 and 2 to be combined are not much different, but When using a combination of pumps, engine load fluctuations will be reduced if the cross-sectional area is matched to the pump capacity ratio.

The cylinder 7 into which the control piston 6 is inserted has three plungers 80, 81-82 at the end opposite to the end wall 70 through which the connecting rod 60 is inserted and withdrawn.
Cylinder parts 71 and 72-73 are installed in parallel with the third gear to slidably fit the cylinder 7
A bow) 71 provided on the end wall 74 opposite to the end wall 70 of
The variable displacement pumps 1 and 73a are connected to the boats 71a, 72a, and 73a.
The respective terminals of the pilot circuits 10a, 20a, and 40a of the pumps 2 and 4 are connected and communicated separately.

The embodiment device constructed in this manner operates as follows.

The load W of the engine E is the discharge pressure ('If/J) of the variable displacement pump 1.2 and the fixed displacement pump 4, respectively, P11.
If 1F211F, binding, and discharge amount (jL/win) are respectively Q111Q2 and Q4, W section PIIIQ1+P
2@Q2+P4・Q4. Therefore, in order to keep the load W of the engine E constant, the pressure (P1 + Pz + Pa)
If/cd and discharge amount (Qi +Q2 +Q4) i/
It is sufficient if the relationship with sin changes inversely proportionally as shown in diagram M3. In other words.

The discharge amount (Ql
+92 +94), the load on the engine E can be held constant.

Now, the force (1
If f) are respectively Fl and F26F4, the discharge pressure (Pl +P2+P4) of each hydraulic bomb 2114 is O"
When using SF/CD, double plungers 80, 81, 8
2 acting on the control piston 6 via F, +F2 +
F becomes 0 to f, and the stroke of the control piston 6 becomes 0.
■ Becomes koji (inactive state) (see Figure 4), therefore,
The discharge amount (Q1+92) of the variable displacement pump 1112 reaches its maximum state (see FIG. 5), and this state is the state shown in FIG. 2.

Then, in this condition, due to the increase in load.

The discharge pressure (PI + P2 + P4) increases, and the control piston 6
When the force F1 +F2 +Fa acting on becomes a to f, this force pushes the control piston 6 to the left in Fig. 2, compresses the springs 61 and 62, and then the two plungers The control piston moves until the force acting on the control pistons 80, 81, and 82 (the force acting on the control piston 6 (F1+F2 +F4)) and the load of the springs 61 and 62 are balanced (the stroke position shown in FIG. 4). As a result, the discharge amount (Q1+Q
z) decreases from the maximum state to Cl/sin and the fifth
(See figure), PIIIQl+P2・Qz+P4 dispute Q4 is
The relationship shown in the explanatory diagram of FIG. 6 is obtained and hardly changes.

Therefore, since the discharge amount of the variable displacement pump is reduced by the amount that the pressure has increased, fluctuations in the load of the engine E can be suppressed to a small level.

As explained above, the output control device in the hydraulic system for construction machinery according to the present invention includes one or more variable displacement pumps l-2 and one or more fixed displacement pumps 4.
are connected so as to be driven at a constant rotation speed by a common prime mover E, and pilot circuits 10a and 20a are connected to the discharge circuits 10, 20, and 40 of the variable displacement pump 1-2 and the fixed displacement pump 4, respectively.・The variable displacement pumps 1 and 2 are provided with a control piston 6 that can be slidably inserted into the cylinder 7, and a connecting rod is provided so that the movement of the control piston 6 changes the discharge pressure. 60, and the control piston 6 has springs 61 and 6 that push back in the direction of increasing the discharge pressure of the variable displacement pump l-2.
2, and the variable capacity bomb 2 and the fixed capacity pump 4 are combined on the opposite side to the connecting rod 60.
80 small-diameter plungers corresponding to the total number of
81 and 82 are connected in parallel, and the cylinder 7 has the plunger 8 at the end opposite to the connecting rod 60.
Cylinder part 7 into which 0.81.82 is slidably inserted.
1-72 and 73 are provided, and the aforementioned pilot circuits 10a@20a and 40a are connected and communicated with each of them separately, so the orifice area increases or decreases in inverse proportion to the fixed throttle and the discharge pressure of the fixed capacity pump. By combining a fixed displacement pump and a variable displacement pump with only a control piston, it is now possible to control the discharge amount of the variable displacement pump to decrease by the amount that the pressure increases, without using a variable throttle. To reduce fluctuations in engine load and to effectively utilize engine power without wasting it without increasing costs.

[Brief explanation of the drawing]

FIG. 1 is a developed view of the conventional means, FIG. 2 is a developed view of the embodiment of the present invention, FIGS. 3, 4, 5, and 6.
The figure is an explanatory diagram of the action. Explanation of drawing symbols E...Engine W...Load 1, 2...Variable displacement pump 10, 20...Discharge circuit 10a, 20a...Pilot circuit 3...Fixed throttle 4...Fixed capacity pump 40
...Discharge circuit 40a...Pilot circuit 5.
...Variable aperture 6...Control piston 60...
Connecting rod 61-62...Spring 7...Cylinder 70...-m171, 72, 73...Cylinder part 71a, 72a, 73a...Port 80 Pot 81, 82...Plunger 74...・End wall permission Application: Hito Honeyx Industries Co., Ltd. Figure Piston flow 1; 4 lower 11 Force F1◆F2 Now F4 kg↑ Stroke of piston 6 mm

Claims (1)

[Claims] (1), one or more variable displacement pumps 1 and 2;
One or more fixed displacement pumps 4 are connected to each other so as to be driven at a constant rotation speed by one common prime mover E, and the discharge circuits 10 and 20 of the variable displacement pumps 1 and 2 and the fixed displacement pump 4 are connected.・The pilot circuits 10a, 20a, and 40a are branched and provided in the variable displacement pumps 1 and 2, respectively, and the control piston 6 that can be slidably inserted into the cylinder 7 is controlled by the movement of the control piston 6. The control piston 6 is connected to the control piston 6 with springs 61 and 62 that push it back in the direction of increasing the discharge pressure of the variable displacement pumps 1 and 2. A number of small-diameter plungers 80, 81, and 82 corresponding to the sum of the numbers of the variable displacement pumps 1 and 2 and the fixed displacement pump 4 combined on the opposite side of the cylinder 60 are connected in parallel, and the cylinder 7 is connected in parallel. The aforementioned connecting rod 6
The plungers 80, 81, 82 are attached to the end opposite to 0.
Cylinder parts 71, 72, 73 into which the parts are slidably inserted
are provided, and the above-mentioned pilot circuits 10a and 20 are connected to them.
An output control device for a hydraulic system of a construction machine, which is constructed by separately connecting and communicating a and 40a.