JPH0411753B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an input control device for two variable displacement hydraulic pumps driven by one prime mover.

[Background of the Invention] FIG. 1 is a diagram showing a conventional input control device for a hydraulic pump. In the figure, 1 is a prime mover, 2 is a transmission, 3a and 3b are variable displacement hydraulic pumps driven by the prime mover 1 via the transmission 2, and 4a and 4b are hydraulic pumps 3a and 3b.
regulator, 5a, 5b are control cylinders, 6
a, 6b are control pistons, 7a, 7b are springs provided between the control pistons 6a, 6b and control cylinders 5a, 5b, 8a, 8b are control cylinders 5
With piston rods a and 5b, piston rod 8
In other words, the control piston 6
The displacement amount of the hydraulic pumps 3a and 3b, that is, the tilt angle, is controlled by the displacement amount of the hydraulic pumps a and 6b (control members). 9a, 9b, 10a, and 10b are cylinder chambers of the control cylinders 5a and 5b, respectively, and the pressure receiving areas of the cylinder chambers 9a, 9b, 10a, and 10b are equal. 11a, 11b are hydraulic pumps 3a, 3
A pressure reducing valve connected to cylinder chamber 9a, 9b
are supplied with the discharge pressure of the hydraulic pumps 3a, 3b, that is, their own discharge pressure, and the cylinder chambers 10a, 1
The discharge pressure of the hydraulic pumps 3b, 3a, that is, the discharge pressure of other hydraulic pumps, is supplied to 0b via pressure reducing valves 11b, 11a. And cylinder chamber 9
When the total value of the pressures acting on the cylinder chambers 9b, 10b becomes twice the set pressure of the pressure reducing valves 11a, 11b, the control pistons 6a, 6b move to the left against the springs 7a, 7b. . 30a, 30
b is a relief valve connected to the hydraulic pumps 3a, 3b.

Next, the operation of this input control device will be explained. Since the control operations of the hydraulic pumps 3a and 3b are the same, only the hydraulic pump 3a will be explained.
First, the discharge pressure p _db of the hydraulic pump 3b is
When the pressure P ₀ is higher than the set pressure P 0 of the cylinder chamber 10a, the pressure P ₀ acts on the cylinder chamber 10a. Therefore, when the discharge pressure P _da of the hydraulic pump 3a is lower than the set pressure _p0 , the control cylinder 5a is
is in a reduced state, the tilt angle of the hydraulic pump 3a is the maximum, and the discharge flow rate Q of the hydraulic pump 3a is the maximum. Then, when the discharge pressure p _da becomes higher than the set pressure p ₀ , the control piston 6 a is activated by the spring 7
Since the hydraulic pump 3a moves to the left against the force a, the tilting angle of the hydraulic pump 3a decreases, the discharge flow rate Q decreases, and the input torque T of the hydraulic pump 3a becomes a value T that is 1/2 of the maximum torque of the prime mover 1. Controlled to be ₀ . The relationship between the discharge pressure p _da , the discharge flow rate Q, and the input torque T in this case is represented by the diagram A in FIGS. 2 and 3. Next, when the discharge pressure p _db is 1/2 of the set pressure p ₀ , a pressure of 0.5 p ₀ acts on the cylinder chamber 10a.
Therefore, when the discharge pressure p _da is lower than 1.5p ₀ , the discharge flow rate Q is maximum and the discharge pressure p _da is
When it becomes higher than 1.5p ₀ , the discharge flow rate Q decreases,
The input torque T is controlled to be 1.5T ₀ .
The relationship between the discharge pressure p _da , the discharge flow rate Q, and the input torque T in this case is represented by the diagram C in FIGS. 2 and 3. Then, when the discharge pressure p _db is zero,
No pressure acts on the cylinder chamber 10a. Therefore, when the discharge pressure p _da is lower than 2p ₀ , the discharge flow rate Q is maximum, and when the discharge pressure p _da is higher than 2p ₀ , the discharge flow rate Q decreases and the input torque T becomes 2T _0.
It is controlled so that Discharge pressure in this case
The relationship between p _da , discharge flow rate Q, and input torque T is
This is represented by line E in FIGS. Also, when the discharge pressure p _db is 0.75p ₀ and 0.25p ₀ , the discharge pressure p _da
The relationship between , discharge flow rate Q, and input torque T is shown in Figure 2.
This is represented by diagrams B and D in FIG.

Therefore, when the input torque of the other party's hydraulic pump, for example, hydraulic pump 3b, is less than _T0 ,
The input torque of the hydraulic pump 3a is
_The input torque of the hydraulic pump 3b can be increased until the total value of the input torque of The total value does not exceed the output torque _2T0 of prime mover 1.

However, the pressure oil discharged by the hydraulic pumps 3a, 3b is not always effectively utilized. For example, when the hydraulic cylinder in operation reaches the stroke end, the discharge pressures p _da and p _db rise, and the discharge pressures p _da and p _db increase in the relief valves 30a and 30.
When the set pressure p _r of b is reached, the relief valves 30a,
30b is open. For this reason, the power of the prime mover 1 is consumed by the relief valves 30a and 30b, and does not become effective work. In particular, when the discharge pressure p _db of another hydraulic pump, such as the hydraulic pump 3b, is low, the discharge flow rate Q when the relief valve 30a is opened,
The input torque T is very large, resulting in extremely large energy loss. In addition, relief valves 30a, 30b
Since the power consumed in this process becomes heat, the temperature of the hydraulic oil rises, which necessitates increasing the capacity of the cooling system, and also causes the hydraulic oil to deteriorate more quickly. Furthermore, since the relief valves 30a and 30b open and close frequently, the noise of the entire device increases.

Therefore, an input control device for a hydraulic pump shown in FIG. 4 has been considered. 12a, 12b in the figure
are pressure reducing valves 11b, 11a and cylinder chambers 10a, 1
A switching valve provided between the switching valve 12 and the switching valve 12
The set pressure p _c of a, 12b is the relief valve 30a, 3
0b is slightly lower than the set pressure p _r , and when its own discharge pressure is lower than the set pressure p _c , it is in the a position, and the discharge pressure of the other hydraulic pumps 3b, 3a is reduced to the cylinder chamber via the pressure reducing valves 11b, 11a. 10a,1
0b, and when its own discharge pressure is higher than the set pressure p _c , it is at position b, and its own discharge pressure is applied to the cylinder chambers 10a and 10b.

In this input control device, the hydraulic pump 3
When the discharge pressures p _da and p _db of a and 3b are lower than the set pressure p _c , the switching valves 12 a and 12 b are in the a position, and operate in the same way as the conventional input control device shown in FIG. Make effective use of the power of 1. For example, the discharge pressure of the hydraulic pump 3a
When p _da becomes higher than the set pressure p _dc of the switching valve 12a, the switching valve 12a is switched to position b, and a discharge pressure p _da higher than the set pressure p _c acts on the cylinder chamber 10a. In this case, since the set pressure p _r is as high as 2p ₀ to 3p ₀ , the force acting on the control piston 6a increases,
Control piston 6a moves to the left against spring 7a.
Therefore, as shown in FIG. 5, the discharge flow rate Q decreases, and as shown in FIG. 6, the input torque T also decreases. In addition, this control operation was performed by the hydraulic pump 3b.
It is the same even if it is attached. In this way, the pump 3a,
3b discharge pressure p _da , p _db is the relief valve 30 a, 3
When the pressure approaches the set pressure p _r of 0b, the hydraulic pump 3
Since the discharge flow rate Q of a and 3b is reduced, the flow rate passing through the relief valves 30a and 30b is significantly reduced.

However, a valve (not shown) having a throttle such as a directional control valve is usually connected to the hydraulic pumps 3a and 3b.
When the discharge pressure p _da becomes higher than the set pressure p _c , the switching valve 12a is placed in the b position, and the discharge flow rate Q of the hydraulic pump 3a decreases, the discharge pressure p _da decreases due to the throttle of the valve. Then, the switching valve 12a
position, the discharge flow rate Q increases, and in this case, the discharge pressure p _da increases again due to the throttle of the valve.
This also applies to the hydraulic pump 3b side. As described above, since the input control device causes self-excited vibration, stable flow rate control is impossible.

[Purpose of the invention]

This invention was made to solve the above-mentioned problems, and an object thereof is to provide an input control device for a hydraulic pump that is capable of stable flow control.

[Summary of the invention]

In order to achieve this object, in the present invention, between the pressure reducing valve and the control member, when the discharge pressure of the own hydraulic pump is lower than the set pressure, the control member controls the discharge pressure of another hydraulic pump via the pressure reducing valve. A switching valve is provided that applies its own discharge pressure to the control member when its own discharge pressure is higher than the set pressure, a chamber is connected to the pilot port of the switching valve, and a check valve is installed on the upstream side of the chamber. and a diaphragm are provided in parallel.

[Embodiments of the invention]

FIG. 7 is a diagram showing an input control device for a hydraulic pump according to the present invention. 16a, 16b in the figure
are the pilot ports of the switching valves 12a and 12b, 1
4a, 14b are chambers connected to the pipeline connecting the hydraulic pumps 3a, 3b and the pilot ports 16a, 16b; 13a, 13b are check valves provided upstream of the chamber 14a, 14b in the pipeline; 15a, 15b is check valve 13a, 1
This is a diaphragm provided in parallel with 3b.

In this input control device, for example, when the discharge pressure p _da of the hydraulic pump 3a increases, the pressure within the chamber 14a rapidly increases via the check valve 13a. Therefore, the discharge pressure p _da is the set pressure p _c
When the pressure becomes higher, the pressure inside the chamber 14a becomes higher than the set pressure p _c , the switching valve 12a becomes the position b, and the discharge flow rate Q of the hydraulic pump 3a decreases. In this case, as mentioned above, the discharge pressure p _da decreases due to the throttle of the valve, but the pressure inside the chamber 14a gradually decreases via the throttle 15a, so the switching valve 12a is held at position b. . Then, when the discharge pressure p _da remains lower than the set pressure p _c for a predetermined period of time, the pressure inside the chamber 14a becomes lower than the set pressure p _c , the switching valve 12a becomes the a position, and the discharge flow rate Q increases. . Therefore, self-excited vibration does not occur. This also applies to the hydraulic pump 3b side.

FIG. 8 is a sectional view showing the structure of a valve device that combines the switching valve 12a, check valve 13a, chamber 14a and throttle 15a shown in FIG. In the figure, 17 is the valve body, 18 is a spool slidably provided in the valve body 17, and 19 is the valve body 17.
A spring 20 provided between the valve body 17 and the spool 18 is a chamber provided within the valve body 17, and a chamber 14a is connected to the chamber 20. 21 is spool 1
8, a passage provided in the chamber 20, 22 a poppet provided in the chamber 20, and 23 a valve body 17 and the poppet 22.
A poppet 22 and a spring 23 constitute a check valve 13a. 24 is a port connected to the pressure reducing valve 11b, 25 is a port connected to the cylinder chamber 10a, and 26 is a hydraulic pump 3.
This is the port connected to a.

In this valve device, the port 26 and the chamber 20,
The chamber 14a is connected to the passage 21 and the check valve 13a.
Since the discharge pressure p _da increases, the pressure within the chamber 14a increases. When the discharge pressure p _da is lower than the set pressure pc, the pressure inside the chamber 14a is also lower than the set pressure p _c , so the spool 18 is pushed to the right by the spring 19 as shown in the figure, and the ports 24 and 25 communicate with. Further, when the discharge pressure p _da becomes higher than the set pressure p _c , the pressure inside the chamber 14 a becomes higher than the set pressure p _c , the spool 18 moves to the left against the spring 19 , and the ports 26 and 25 communicate with each other. do. In this state, when the discharge pressure p _da becomes lower than the set pressure p _c , since the chamber 14 a and the chamber 20 communicate with each other via the throttle 15 a, the pressure inside the chamber 14 a gradually decreases, and the pressure inside the chamber 14 a decreases. When the pressure becomes lower than the set pressure p _c , the spring 19 causes the spool 18 to move to the right, and the ports 24 and 25 communicate with each other.

FIG. 9 is a diagram showing another input control device for a hydraulic pump according to the present invention. In the figure, 31a, 3
1b is a hydraulic power source, 32a, 32b are hydraulic power sources 31a,
Servo valves connected to 31b, 33a and 33b are springs of servo valves 32a and 32b, and 34a and 34
b, 35a, 35b are the pilot ports of the servo valves 32a, 32b, and the pilot port 34a3
4b is supplied with the discharge pressure of the hydraulic pumps 3a, 3b, that is, its own discharge pressure, and the pilot ports 35a, 35b are supplied with the switching valves 12a, 12b so that when the discharge pressures _pda , _pdb are lower than the set pressure _pc , The discharge pressure of the hydraulic pumps 3b, 3a, that is, the discharge pressure of other hydraulic pumps, is supplied via the pressure reducing valves 11b, 11a, and when the discharge pressures p _da , p _db are higher than the set pressure p _c , the discharge pressures of the hydraulic pumps 3 a, 3 b are supplied. A discharge pressure, that is, a self-discharge pressure is supplied.
36a and 36b are servo pistons connected to the servo valves 32a and 32b, and the servo piston 36
Hydraulic pumps 3a, 3 depending on the displacement amount of a, 36b
The displacement volume of b, that is, the tilt angle is controlled.

FIG. 10 is a sectional view showing the structure of the regulator 4a of the input control device shown in FIG. 9. In addition,
The structure of the regulator 4b is also similar. In the figure, 37 is a spool of the servo valve 32a, 38 is a sleeve of the servo valve 32a, 39 is a feedback lever whose one end is rotatably attached to the casing, and 40 and 41 are pins provided on the lever 39. 40 and 41 are respectively servo pistons 3
6a, engaged with the sleeve 38. 42,43
are cylinder chambers formed on both sides of the servo piston 36a.

In this input control device, the spool 37
The amount of displacement of the (control member) is determined by the total value of the force of the spring 33a and the force due to the pressure acting on the pilot ports 34a and 35a. For example, the first
When the spool 37 is displaced to the left from the state shown in FIG. At this time, the sleeve 38 is displaced by the lever 39 in accordance with the displacement of the servo piston 36a, and when the servo piston 36a is displaced by an amount corresponding to the displacement amount of the spool 37, the pressure oil of the hydraulic source 31a is transferred to the sleeve 38. As a result, the cylinder chamber 42 is no longer supplied with water, and communication between the cylinder chamber 43 and the tank is cut off by the sleeve 38, so the servo piston 36a stops. That is, the servo piston 3
The displacement amount of the hydraulic pump 3a has a value corresponding to the displacement amount of the spool 37, and therefore the tilting angle of the hydraulic pump 3a has a value according to the displacement amount of the spool 37. In this way, the amount of displacement of the spool 37 is determined by the force of the spring 33a and the total value of the pressures acting on the pilot ports 34a and 35a, and the tilting angle of the hydraulic pump 3a is determined according to the amount of displacement of the spool 37. Therefore, in this input control device, the discharge flow rate Q of the hydraulic pumps 3a, 3b is controlled in the same way as the input control device shown in FIG.

In addition, in the above-mentioned embodiment, the chamber 14a,
If the volume of the throttle valve 14b and the throttle ratio of the throttle valves 15a and 15b are appropriately selected, the responsiveness when the discharge pressures p _da and p _db increase and the delay time when the discharge pressures p _da and p _db decrease can be adjusted appropriately. It is possible to set the value to

〔Effect of the invention〕

As explained above, in the input control device for a hydraulic pump according to the present invention, since self-excited vibration does not occur, stable flow control can be performed. As described above, the effects of this invention are remarkable.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a conventional input control device for a hydraulic pump, Fig. 2 is a graph showing the relationship between discharge pressure p _da and discharge flow rate Q in the case of the input control device shown in Fig. 1, and Fig. 3 is a graph showing the relationship between discharge pressure p _da and input torque T in the case of the input control device shown in FIG. 1, and FIG. 4 is a diagram showing an input control device improved from the input control device shown in FIG. 1. , FIG. 5 is a graph showing the relationship between the discharge pressure p _da and the discharge flow rate Q in the case of the input control device shown in FIG. 4, and FIG. A graph showing the relationship between p _da and input torque T, FIG. 7 is a diagram showing an input control device for a hydraulic pump according to the present invention,
FIG. 8 is a sectional view showing the structure of a valve device combining the switching valve, chamber, etc. shown in FIG. 7, FIG. 9 is a view showing another input control device for a hydraulic pump according to the present invention, and FIG. 10 9 is a sectional view showing the structure of the regulator of the input control device shown in FIG. 9. FIG. DESCRIPTION OF SYMBOLS 1... Prime mover, 3a, 3b... Variable displacement hydraulic pump, 4a, 4b... Regulator, 5a, 5b... Control cylinder, 6a, 6b... Control piston, 7a,
7b...Spring, 8a, 8b...Piston rod, 9
a, 9b...Cylinder chamber, 10a, 10b...Cylinder chamber, 11a, 11b...Pressure reducing valve, 12a, 12b
...Switching valve, 13a, 13b...Check valve, 14
a, 14b...Chamber, 15a, 15b...Aperture,
16a, 16b...Pilot port, 31a, 3
1b...Hydraulic power source, 32a, 32b...Servo valve, 33
a, 33b...Spring, 34a, 34b...Pilot port, 35a, 35b...Pilot port, 3
6a, 36b... Servo piston.

Claims (1)

[Claims] 1 The displacement of two variable displacement hydraulic pumps driven by one prime mover is controlled by the displacement amount of a control member, a spring is provided at one end of the control member, and a self-discharge valve is provided at the other end of the control member. In a hydraulic pump input control device that applies pressure and the discharge pressure of another hydraulic pump via a pressure reducing valve, the pressure reducing valve is connected between the pressure reducing valve and the control member when the own discharge pressure is lower than the set pressure. A switching valve is provided which causes the discharge pressure of another hydraulic pump to act on the control member via the control member, and when its own discharge pressure is higher than the set pressure, causes its own discharge pressure to act on the control member, and a pilot port of the switching valve. 1. An input control device for a hydraulic pump, characterized in that a chamber is connected to the chamber, and a check valve and a throttle are provided in parallel on the upstream side of the chamber.