JPS6246711B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a plurality of variable displacement hydraulic pumps driven by one prime mover.

FIG. 1 is a diagram showing a conventional control device for a variable displacement hydraulic pump. In the figure, 1 is the prime mover, 2,
3 is a variable displacement hydraulic pump driven by the prime mover 1, 4 is a transmission that transmits the power of the prime mover 1 to the hydraulic pumps 2 and 3, and 5 and 6 are springs that are displacement control devices for the hydraulic pumps 2 and 3. The displacement amount of the cylinders 5 and 6 controls the displacement of the hydraulic pumps 2 and 3, that is, the tilt angle of the swash plate. 7 and 8 are springs for cylinders 5 and 6,
9 and 10 are cylinder chambers of the cylinders 5 and 6; 11 is a directional switching valve; when the directional switching valve 11 is in the A position, the discharge pressure of the hydraulic pumps 2 and 3, that is, its own discharge pressure is supplied to the cylinder chambers 9 and 10; When the directional control valve 11 is in the B position, the check valve 12 is
is provided, so that the higher discharge pressure of the hydraulic pumps 2 and 3 is applied to the cylinder chambers 9 and 1.
0.

In this control device, the directional control valve 11 is
position, the own discharge pressure is in the cylinder chambers 9, 1.
0, the swash plate tilting angle of the hydraulic pumps 2, 3 is at its maximum until the discharge pressure of the hydraulic pumps 2, 3 reaches a predetermined value, and the discharge flow rate of the hydraulic pumps 2, 3 is at its maximum. However, when the discharge pressure of the hydraulic pumps 2 and 3 exceeds a predetermined value, the cylinders 5 and 6 extend against the springs 7 and 8, and the tilting angle of the swash plate of the hydraulic pumps 2 and 3 becomes smaller, causing the hydraulic pressure to increase. The discharge flow rates of the pumps 2 and 3 are reduced, and the absorption horsepower of the hydraulic pumps 2 and 3 is maintained approximately constant. In addition, the directional control valve 11 is
position, the higher of the discharge pressures of the hydraulic pumps 2 and 3 is supplied to both the cylinder chambers 9 and 10, so even if the discharge pressures of the hydraulic pumps 2 and 3 are different, , the swash plate tilting angles of the hydraulic pumps 2 and 3 become equal, and the discharge flow rates of the hydraulic pumps 2 and 3 become equal. However, in this case, the discharge flow rate of the hydraulic pump with a lower discharge pressure, such as the hydraulic pump 2, decreases in accordance with the discharge pressure of the hydraulic pump 3, which has a higher discharge pressure, so the absorption horsepower of the hydraulic pump 2 decreases. However, the output horsepower of the prime mover 1 cannot be used effectively.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a control device for a variable displacement hydraulic pump that can effectively utilize the output horsepower of a prime mover.

In order to achieve this object, the present invention provides a device for controlling first and second variable displacement hydraulic pumps driven by one prime mover.
first and second displacement control devices for controlling the displacement of a second variable displacement hydraulic pump; the first and second displacement control devices; and the first and second displacement control devices;
First and second pipes connecting the discharge side pipe of the variable displacement hydraulic pump, first and second throttles provided in the first and second pipes, and the first and second pipes. A connecting pipe line is provided that connects the first and second displacement control device sides of the line with respect to the first and second throttles.

FIG. 2 is a diagram showing a control device for a variable displacement hydraulic pump according to the present invention. 13,1 in the figure
4 is a pipe connecting the discharge side pipes of the variable displacement hydraulic pumps 2 and 3 to the cylinder chambers 9 and 10 of the spring-equipped cylinders 5 and 6; 15 and 16 are throttles provided in the pipes 13 and 14; 17 is the orifice 1 of the pipes 13 and 14
A connecting pipe line 18 connects the cylinders 5 and 6 with respect to the cylinders 5 and 6, and 18 is an on-off valve provided in the connecting pipe line 17.

Figure 3 shows cylinder chambers 9 and 10 of cylinders 5 and 6.
3 is a graph showing the relationship between the internal pressure, that is, the control pressure, and the discharge flow rate of the hydraulic pumps 2 and 3. As shown in this graph, the pressure inside the cylinder chambers 9 and 10 is
Until p ₀ is reached, cylinders 5 and 6 are held by springs 7 and 8.
The swash plate tilt angle of the hydraulic pumps 2 and 3 is the maximum, and the discharge flow rate of the hydraulic pumps 2 and 3 is Q _nax , but the pressure in the cylinder chambers 9 and 10 is p ₀ In this case, the cylinders 5 and 6 extend against the springs 7 and 8, so that the swash plate tilt angles of the hydraulic pumps 2 and 3 become small, and the discharge flow rates of the hydraulic pumps 2 and 3 decrease.

In this control device, when the on-off valve 18 is closed, the discharge pressure of the hydraulic pumps 2 and 3 is
5 and 16 to the cylinder chambers 9 and 10. Therefore, the discharge pressure of hydraulic pumps 2 and 3 is
Until p ₀ is reached, the discharge flow rate of hydraulic pumps 2 and 3 is Q _nax , and the discharge pressure of hydraulic pumps 2 and 3 is
When it becomes p ₀ or more, the discharge flow rate of the hydraulic pumps 2 and 3 decreases, and the absorbed horsepower of the hydraulic pumps 2 and 3 is kept almost constant. For example, when the discharge pressures of the hydraulic pumps 2 and 3 are p ₁ and p ₂ , respectively, the discharge flow rates of the hydraulic pumps 2 and 3 are Q ₁ and Q ₂ , respectively, and the absorbed horsepower of the hydraulic pumps 2 and 3 are respectively the prime mover 1. This is about 50% of the output horsepower. When the on-off valve 18 is opened in this state, the pressure introduced into the cylinder chambers 9 and 10 is reduced to the pressure p ₁ by the throttles 15 and 16.
Since the average value _pa of p ₂ is obtained, the discharge flow rate of the hydraulic pumps 2 and 3 becomes the average value Q _a of the discharge flow rates Q ₁ and Q ₂ .
In other words, the discharge flow rate of the hydraulic pump 2 is from Q ₁ to Q _a
The discharge flow rate of the hydraulic pump 3 increases from Q ₂ to Q _a , and the discharge flow rates of the hydraulic pumps 2 and 3 become equal. In this case, the discharge pressures p ₁ and p ₂ of the hydraulic pumps 2 and 3 do not change, so the absorption horsepower of the hydraulic pump 2 decreases and the absorption horsepower of the hydraulic pump 3 increases, for example, the absorption horsepower of the hydraulic pump 2 increases. If the output horsepower of prime mover 1 is 30%, the absorption horsepower of hydraulic pump 3 will be approximately 70% of the output horsepower of prime mover 1.
Nearly 100% of the output horsepower of prime mover 1 can be utilized.

FIG. 4 is a diagram showing another control device for a variable displacement hydraulic pump according to the present invention. In the figure 1
9, 20 are displacement control devices for the hydraulic pumps 2, 3; 21, 22 are hydraulic sources; 23, 24 are servo valves connected to the hydraulic sources 21, 22; 25, 26 are springs for the servo valves 23, 24; Reference numerals 27 and 28 are pilot ports of the servo valves 23 and 24, and the pipe lines 13 and 14 are connected to the pilot ports 27 and 28, respectively. 29 and 30 are servo pistons connected to the servo valves 23 and 24;
The displacement amount of 30 controls the displacement volume of the hydraulic pumps 2 and 3, that is, the swash plate tilt angle.

FIG. 5 is a sectional view showing the structure of the control device 19 shown in FIG. 4. In the figure, 31 is the servo valve 2
3 is the spool, 32 is the sleeve of the servo valve 23,
33 is a feedback lever whose one end is rotatably attached to the valve body of the servo valve 23; 34 and 35 are pins provided on the lever 33;
are engaged with the servo piston 29 and sleeve 32, respectively. 36 and 37 are servo pistons 29
This is a cylinder chamber formed on both sides of the cylinder. Note that the structure of the control device 20 is also similar.

In the control device 19, the amount of displacement of the spool 31 is determined by the force of the spring 25 and the force due to the pressure acting on the pilot port 27. For example, when the spool 31 is displaced to the left from the state shown in FIG.
On the other hand, since the cylinder chamber 37 communicates with the tank, the servo piston 29 moves to the left. At this time, the sleeve 32 is also displaced by the lever 33 according to the displacement of the servo piston 29, so the servo piston 29 moves to the left. When the spool 31 is displaced by an amount corresponding to the amount of displacement, the pressure oil from the hydraulic source 21 is no longer supplied to the cylinder chamber 36 by the sleeve 32, and on the other hand, communication between the cylinder chamber 37 and the tank is maintained by the sleeve 32. Since it is shut off, the servo piston 29 stops. That is, since the displacement amount of the servo piston 29 has a value corresponding to the displacement amount of the spool 31, the swash plate tilting angle of the hydraulic pump 2 has a value according to the displacement amount of the spool 31. in this way,
The amount of displacement of the spool 31 is determined by the force of the spring 25 and the force due to the pressure acting on the pilot port 27, and the tilting angle of the swash plate of the hydraulic pump 2 is determined by the force of the spring 25 and the force due to the pressure acting on the pilot port 27.
The value corresponds to the amount of displacement of 1. In addition, the control device 2
This operation is the same for 0. Therefore, since the control device shown in FIG. 4 controls the discharge amount of the hydraulic pumps 2 and 3 in the same way as the control device shown in FIG. 2, it is possible to utilize nearly 100% of the output horsepower of the prime mover 1. can.

In the above-mentioned embodiment, the on-off valve 18 was provided in the connecting pipe 17, but the control for supplying the discharge pressure of the hydraulic pumps 2 and 3 to the cylinder chambers 9 and 10 and the pilot ports 27 and 28, that is, the own discharge pressure When it is not necessary to perform the control, the on-off valve 18 may be omitted.

As explained above, in the control device for a variable displacement hydraulic pump according to the present invention, when the discharge flow rate of both hydraulic pumps is controlled to be the same, almost the entire output horsepower of the prime mover can be utilized.
In particular, when one hydraulic pump is left unloaded, almost the full output horsepower of the prime mover can be transmitted to the other hydraulic pump, so the oil discharged from the two hydraulic pumps can be combined into one without having to merge through a valve or the like. Almost the entire output horsepower of the prime mover can be transmitted to the actuator. As described above, the effects of this invention are remarkable.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional variable displacement hydraulic pump control device, FIG. 2 is a diagram showing a variable displacement hydraulic pump control device according to the present invention, and FIG. 3 is a diagram showing the relationship between control pressure and discharge flow rate. FIG. 4 is a diagram showing another control device for a variable displacement hydraulic pump according to the present invention, and FIG. 5 is a sectional view showing the displacement control device shown in FIG. 4. 1... Prime mover, 2, 3... Variable displacement hydraulic pump,
5, 6... Cylinder with spring, 7, 8... Spring, 9, 1
0...Cylinder chamber, 13, 14...Pipe line, 15, 16
... Throttle, 17... Connection pipe line, 18... Opening/closing valve, 19,
20... Displacement control device, 23, 24... Servo valve, 25, 26... Spring, 27, 28... Pilot port, 29, 30... Servo piston.

Claims (1)

[Claims] 1. In a device for controlling first and second variable displacement hydraulic pumps driven by one prime mover, first and second displacement control devices that control the displacement of the first and second variable displacement hydraulic pumps. and the first and second displacement control devices, and the first and second displacement control devices;
First and second pipe lines connecting the discharge side pipe line of the second variable displacement hydraulic pump; first and second throttles provided in the first and second pipe lines; A control device for a variable displacement hydraulic pump, comprising: a connecting conduit that connects the first and second displacement control device sides of the two conduits rather than the first and second throttles.