JPH0452395B2 - - 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
By changing the positions of a and 6b (control members), the displacement volume, that is, the tilt angle, of the hydraulic pumps 3a and 3b is controlled. 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, 3b
The discharge pressure of the hydraulic pumps 3a, 3b, that is, its own discharge pressure, is supplied to the cylinder chambers 9a, 9b by the pressure reducing valve connected to the cylinder chambers 10a, 10.
The discharge pressure of the hydraulic pumps 3b and 3a, that is, the discharge pressure of other hydraulic pumps, is supplied to the pump b via the pressure reducing valves 11b and 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 set pressure p of b is higher than ₀ , cylinder chamber 1
Pressure p ₀ acts on 0a. Therefore, when the discharge pressure p _db of the hydraulic pump 3a is lower than the set pressure p ₀ , the control cylinder 5a is in a contracted state due to the spring 7a, and the tilting angle of the hydraulic pump 3a is maximum. The discharge flow rate Q of the hydraulic pump 3a is maximum. Then, the discharge pressure p _da is the set pressure p ₀
When the height increases, the control piston 6a moves to the left against the spring 7a, so the tilt angle of the hydraulic pump 3a decreases, the discharge flow rate Q decreases, and the hydraulic pump 3a
The input torque T is 1/2 of the maximum torque of prime mover 1.
is controlled so that the value of T is ₀ . The relationship between the discharge pressure p _db , 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
It is controlled so that 2T ₀ . In this case, the relationship between the discharge pressure p _da , the discharge flow rate Q, and the input torque T is represented by the diagram E in FIGS. 2 and 3. Also, when the discharge pressure p _db is 0.75p ₀ and 0.25p ₀ , the discharge pressure
The relationship between p _da , discharge flow rate Q, and input torque T is
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 at 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 frequently close and close, the noise of the entire apparatus 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 _c of the switching valve 12a,
The switching valve 12a switches to the b position, and the cylinder chamber 1
A discharge pressure p _da higher than the set pressure p _c acts on 0a. 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, and the control piston 6a moves to the left against the 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. Note that this control operation is the same for the hydraulic pump 3b. 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 the valves 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 provides an input control device for a hydraulic pump that does not cause self-excited vibration, has sufficiently fast response, and is capable of stable flow control. The purpose is to

[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 hydraulic pump is lower than the set pressure, the discharge pressure of another hydraulic pump is applied to the control member via the pressure reducing valve. A switching valve is provided that allows the control member to use its own discharge pressure when its own discharge pressure is higher than the set pressure, and a chamber is connected to the pilot port of the switching valve, and a chamber is connected to the upstream side of the chamber in the opposite direction. Two check valves and a throttle 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. 17a, 17b in the figure
are the pilot ports of the switching valves 12a and 12b, 1
3a, 14a, 13b, 14b are hydraulic pumps 3
A, 3b and pilot ports 17a, 17b.
are arranged in opposite directions and in parallel.
16a and 16b are check valves 13 in the pipes.
a, 14a are arranged in parallel with the check valves 13b, 14b; 15a, 15b are the check valves 1;
3a, 14a, throttle 16a, check valve 13
This is a chamber connected to a conduit that connects the pilot ports 17a, 17b and the aperture 16b.

In this input control device, for example, the discharge pressure p _da of the hydraulic pump 3a rises rapidly, and the discharge pressure p _da and the pilot port 17a (chamber 15a
When the differential pressure between the check valve 13a and the pressure inside the check valve 13a exceeds the cracking pressure of the check valve 13a, the check valve 13a
is opened and the discharge pressure of the hydraulic pump 3a is charged to the chamber 15a via the check valve 13a, so the pressure acting on the pilot port 17a rapidly increases until the differential pressure reaches the cracking pressure of the check valve 13a. When the differential pressure reaches the cracking pressure of the check valve 13a, the check valve 13a closes and the hydraulic pump 3a and the pilot port 17a are connected only through the throttle 16a, so the pressure acting on the pilot port 17a is reduced. It gradually asymptotes to the discharge pressure p _da . Therefore, even if the discharge pressure p _da suddenly rises to the set pressure p _c , the pilot port 17
The pressure acting on a is check valve 1 from the set pressure p _c .
The pressure rises rapidly until the pressure is lower by the cracking pressure in 3a, but after that it rises slowly,
The set pressure p _c is reached. Therefore, the switching valve 12a is slowly switched from the a position to the b position, so the discharge flow rate Q of the hydraulic pump 3a is gradually reduced. In this case, as mentioned above, the discharge pressure p _da decreases due to the throttling of the valve, but the discharge flow rate Q
Since the decrease in the discharge pressure p da is gradual, the decrease in the discharge pressure p _da is also gradual, and self-excited vibration does not occur. Conversely, even if the discharge pressure p _da of the hydraulic pump 3a suddenly decreases from the set pressure _pr of the relief valve 30a to the set pressure p _c , the pressure acting on the pilot port 17a of the switching valve 12a will be lower than the set pressure p _c . The pressure rapidly decreases to a level higher than the cracking pressure of the check valve 14a, but then the pressure of the check valve 14a increases.
is closed, hydraulic pump 3a and pilot port 17
Since it is connected to a only through the aperture 16a,
The pressure in the pilot port 17a gradually approaches the set pressure _pc . Therefore, b of the switching valve 12a
Since the switching from the position to the a position is performed slowly, the discharge flow rate Q of the hydraulic pump 3a increases gradually. In this case, as mentioned above, the discharge pressure p _da increases due to the throttling of the valve, but since the increase in the discharge flow rate Q is gradual, the increase in the discharge pressure p _da is also gradual, and self-excited vibration does not occur. do not have. This also applies to the hydraulic pump 3b side.

FIG. 8 shows the switching valve 12a, check valves 13a, 14a, chamber 15a and throttle 1 shown in FIG.
FIG. 6 is a cross-sectional view showing the structure of a valve device in which valves 6a and 6a are combined. In the figure, 18 is the valve body, 19 is the valve body 1
A spool 8 is slidably provided within the valve body 18, and a spring 20 is provided between the valve body 18 and the spool 19. 21 is a poppet, and 22 is a spring provided between the valve body 18 and the poppet 21. The poppet 21 and the spring 22 constitute the check valve 13a. 23 is a poppet; 24 is a spring provided between the valve body 18 and the poppet 23;
3 and the spring 24 constitute a check valve 14a. One end of the check valves 13a, 14a is connected to the hydraulic pump 3a, and the other end is connected to the chamber 15a and the pilot port 17 of the switching valve 12a.
connected to a. 25 is a port connected to the pressure reducing valve 11b, 26 is a port connected to the cylinder chamber 10a, and 27 is a port connected to the hydraulic pump 3a.

In this valve device, the port 27 and the chamber 15a are connected to the check valves 13a, 14a and the throttle 16.
Since the chambers 15a and 15a communicate with each other through the chamber 15a, when the discharge pressure _pda increases, the pressure within the chamber 15a increases.
When the discharge pressure p _da is lower than the set pressure p _c , the pressure inside the chamber 15a is also lower than the set pressure p _c , so that the spool 19 is moved by the spring 20 as shown in the figure.
is pushed to the right, and ports 25 and 26 communicate with each other. Also, when the discharge pressure p _da becomes higher than the set pressure p _c , the pressure inside the chamber 15a increases to the set set pressure.
p _c , the spool 19 moves to the left against the spring 20, and the ports 27 and 26 communicate with each other. In this state, when the discharge pressure p _da becomes lower than the set pressure p _c , the pressure inside the chamber 15a decreases to the set pressure
p _c , the spool 19 moves to the right by the spring 20, and the ports 25 and 26 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, 35c, 35b are pilot ports of servo valves 32a, 32b, pilot ports 34a,
34b is supplied with the discharge pressure of the hydraulic pumps 3a, 3b, that is, their 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
By changing the positions of a and 36b, the hydraulic pumps 3a and 3
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 also 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 15a,
By appropriately selecting the volume of throttle 15b and the throttle ratio of throttles 16a and 16b, 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 make it a value.

〔Effect of the invention〕

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

[Brief explanation of the drawing]

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, 14a, 14b...Check valve, 15a, 15b...Chamber, 16a,
16b... Throttle, 17a, 17b... Pilot port, 31a, 31b... Hydraulic power source, 32a, 32b...
Servo valve, 33a, 33b...Spring, 34a, 34
b...Pilot port, 35a, 35b...Pilot port, 36a, 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. An input control device for a hydraulic pump, characterized in that a chamber is connected to the chamber, and two check valves and a throttle arranged in opposite directions are provided in parallel on the upstream side of the chamber.