JPS60233386A - Input control device for hydraulic pump - Google Patents

Abstract

PURPOSE:To mitigate the increase and decrease of amount of delivery and prevent self-exciting vibration of the input control device by a method wherein a chamber is connected to the pilot port of a changeover valve and two pieces of check valves and chokes, arranged in reverse direction, are provided in parallel at the upstream of the chamber. CONSTITUTION:When the delivery pressure Pda of the hydraulic pump 3a is dropped suddenly to the set pressure Pc of a relief valve, a pressure, operating on the pilot port 17a of the changeover valve 12a, is dropped suddenly to a pressure higher than the set pressure Pc by the cracking pressure of the check valve 14a. Thereafter, the check valve 14a is opened and the hydraulic pump 3 is connected to the pilot port 17a through the choke 16a only, therefore, the pressure of the pilot port 17a closes to the set pressure Pc slowly. According to the approach of the pressure, switching of the changeover valve 12a from a position (b) to the position (a) is effected slowly, therefore, the delivery flow amount Q of the hydraulic pump 3a (same in the side of the same pump 3b) is increased slowly. Accordingly, the increase of the delivery pressure Pda becomes slow and the self-exciting vibration may be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] This invention relates to an input control device for two variable displacement cedar 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 the prime mover, 2 is the transmission,
3a, 3b are variable displacement cedar hydraulic pumps driven by the prime mover 1 via the transmission 2, 4a, 4b are regulators for the hydraulic pumps 3a, 3b, 5a, 5b are control cylinders, 6a, 6b are control pistons, 7a, 7b are springs provided between the control pistons 6a, 6b and the control cylinders 5d, 5b; 8a, 8b are the control cylinders 5a, 5;
With the piston rod b, the displacement amount, that is, the tilt angle, of the hydraulic pumps 3a, 3b is controlled by the displacement amount of the piston rods 8a, 8b, that is, by the displacement amount of the control pistons 6a, 6b (control members). 9a, 9b, 10a,
10b is a cylinder chamber of each of the control cylinders 5a, 5b, which is equal to the pressure receiving area weight of the cylinder chambers 9a, 9b, 10a, 10b b).

11a and llb are pressure reducing valves connected to the hydraulic pumps 3a and 3b, and the cylinder chambers 9a and 9b4 are connected to the hydraulic pump 3a.
, 3b, that is, the own discharge pressure 1 is supplied to the cylinder chambers 10a, 10b, and Lt pressure reducing valve 1.
The discharge pressure of the hydraulic pumps 3b and 3a, that is, the discharge pressure of other hydraulic pumps, is supplied via the hydraulic pumps 1b and 11a.

Then, cylinder chambers 9a, 10a, cylinder chambers 9b, 1
When the total value of pressure acting on the pressure reducing valves 11a, llb becomes twice the set pressure of the pressure reducing valves 11a, llb, the control pistons 6a, 6
Is b resisting springs 7a and 7bk to the left? Te. 30a, 3
0b is a 1-noleaf valve connected to the hydraulic pumps 3a and 3b.

Next, the operation of this input control device will be explained in b).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 pab'h' pressure reducing valve 1 of the hydraulic pump 3b
1b set pressure p. When higher, 1
Pressure Pa acts on 0a. Therefore, the discharge pressure pala of the hydraulic pump 3a is the set pressure p. When it is lower, 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 pda is the set pressure p. When the height increases, the control piston 6a moves to the left against the spring 7a, so 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 reaches the maximum of the prime mover 1. 1 of value torque
/2 value T. Controlled. In this case, the relationship between the discharge pressure pda, the discharge flow rate Q, and the input torque T is
It is represented by diagram A in FIG.

Next, when the discharge pressure Pc1h is the set pressure Pa of 172, pressures o and spo act on the cylinder chamber 10a. Therefore, when the discharge pressure pda is lower than 1.5p, the discharge flow rate Q is maximum, and the discharge pressure pd
When a becomes higher than 1.5po, the discharge flow rate Q is reduced and the input torque T is controlled to be 1.5T.

In this case, the discharge pressure pda, the discharge flow rate Q, and the input torque T
The relationship between the two is represented by line C in FIGS. 2 and 3. Then, when the discharge pressure pdb is zero, the cylinder chamber 1
No pressure acts on 0a.

Therefore, the discharge pressure p1 is 2ρ. When the pressure is lower than 1, the discharge flow rate Q is maximum, and when the discharge pressure Pda becomes higher than 2po, the discharge flow rate Q is controlled to decrease and the input torque T becomes 2T. Discharge pressure P in this case
The relationship between da, discharge flow rate Q, and input torque T is represented by the diagram E in FIGS. 2 and 3. Also, the discharge pressure Pdb is 0
．． 75 po, 0.25 p++, the relationship between the discharge pressure pda, the discharge flow rate Q, and the input torque T is as shown in Fig. 2.
This is represented by diagrams B and D in FIG.

Therefore, the other party's hydraulic pump, for example, hydraulic pump 3
When the input torque of b is less than T0, the hydraulic pump 3a
Since the input torque of the hydraulic pump 3a and the input torque of the hydraulic pump 3b can be increased until the total value of the input torque of the hydraulic pump 3a and the input torque of the hydraulic pump 3b reaches 2T, the output torque of the prime mover 1 can be effectively used, and the hydraulic pump 3a, 3
The total value of the input torques b is the output torque 2T of the prime mover 1.

It never exceeds.

However, the pressure oil discharged by the hydraulic pumps 3a, 3b is not always effectively utilized. For example, when an operating hydraulic cylinder reaches the stroke end, the discharge pressure P aa-pdb increases, and the discharge pressure pcl
a and pdb are the set pressures py of the relief valves 30a and 30b
When it reaches, the relief valves 30a, 30b are opened. For this reason, the power of the prime mover 1 is consumed by the relief valves 30a and 30b, and is not used for effective work. In particular, when the discharge pressure pab of another hydraulic pump, for example, the hydraulic pump 3b, is low, the discharge flow rate Q when the relief valve 30a is opened is
, the input torque T is very large, and the energy loss is extremely large. In addition, since the power consumed by the relief valves 30a and 30b becomes heat, the temperature of the hydraulic oil increases.
It is necessary to increase the capacity of the cooling device, and the hydraulic oil deteriorates quickly. Furthermore, the relief valve 30
Since a-30b is frequently opened and closed, the noise of the entire device increases.

Therefore, an input control device for a hydraulic pump as shown in FIG. 4 has been considered. In the figure, 12a and 12b are pressure reducing valves 11b
, lla and the cylinder chambers 10a, 10b.The setting pressure pc of the switching valves 12a, 12b is slightly lower than the setting pressure p1 of the relief valves 30a, 30b, and the own discharge pressure is the setting pressure. P. When it is lower,
a position, and the discharge pressure of the other hydraulic pumps 3b, 3a is transferred to the cylinder chambers 10a, 10 via the pressure reducing valves tib, 11a.
b, and when its own discharge pressure is higher than the set pressure pc, it is in position b, and its own discharge pressure is applied to the cylinder chambers 10a, 10b.

In this input control device, when the discharge pressures Pda and Pc1b of the hydraulic pumps 3a and 3b are lower than the set pressure pc, the switching valves 12a and 12b are in the a position, similar to the conventional input control device shown in FIG. This operation is performed to effectively utilize the power of the prime mover 1. For example, when the discharge pressure pcla of the hydraulic pump 3a becomes higher than the set pressure pc of the switching valve 12a, the switching valve 12a is switched to position b, and a discharge pressure pda higher than the set pressure pc acts on the cylinder chamber 10''a. In this case, the set pressure pr is 2Po ~
Since the pressure is as high as 3 Pa, 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,
Furthermore, 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 discharge pressure p cl of the pumps 3a, 3b
When a, P clb approaches the set pressure Pr of the relief valves 30a, 30b, the discharge flow rate Q of the hydraulic pumps 3a, 3b is reduced, so the flow rate passing through the relief valves 30a, 30b is significantly reduced.

However, the hydraulic pumps 3a and 3b are normally connected to a valve (not shown) having a throttle such as a directional control valve, and for example, the discharge pressure pda of the hydraulic pump 3a becomes higher than the set pressure pc. The switching valve 12a is in the b position, and the hydraulic pump 3. When the discharge flow rate Q of a decreases, the discharge pressure pda decreases due to the throttle of the valve. Then, the switching valve 12a becomes the a position, the discharge flow rate Q increases, and in this case, the discharge pressure pja 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 applies its own discharge pressure to the control member when its own discharge pressure is higher than the set pressure, and a chamber is connected to the pylon 1 port of the switching valve, and a reverse valve is connected to the upstream side of the chamber. Two check valves and a throttle arranged in parallel are provided in the same direction.

[Embodiments of the invention]

FIG. 7 is a diagram showing an input control device for a hydraulic pump according to the present invention. In the figure, 17a-17b is the switching valve 12a.
, 12b pilot port, 13a, 14a, 13b
, 14b are hydraulic pumps 3a, 3b and pilot port 1
7a, 17b, check valves 13a, 13b and check valve 14a,
14b are arranged in opposite directions and in parallel to each other.

16a, 16b are check valves 13a, 14 in the pipes.
a, a throttle arranged in parallel with the check valves 13b, 14b;
6b and the pilot ports 17a, ], 7b.

In this input control device, for example, the hydraulic pump 3a
When the discharge pressure pda of the hydraulic pump 3a increases rapidly and the differential pressure between the discharge pressure Pda and the pressure in the pilot port 17a (inside the chamber 15a) exceeds the cracking pressure of the check valve 13a, the check valve 13a opens and the pressure of the hydraulic pump 3a increases. Since the discharge pressure is charged into the chamber 15a through the check valve 13a, 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 boat 17a are connected only through the throttle 16a, so the pressure acting on the pilot boat 17a is reduced. Discharge pressure Pc1
It gradually approaches a. Therefore, the discharge pressure Pda
is the set pressure P. Even if it suddenly rises to '2'.

The pressure acting on the pilot boat 17a is the set pressure pc
The pressure rises rapidly until the pressure is lower by the cracking pressure of the check valve 13a, but after that it rises slowly and reaches the set pressure pc. 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, due to the valve throttling, the discharge pressure P
Although Ja decreases, since the decrease in the discharge flow rate Q is gradual, the decrease in the discharge pressure Pda is also gradual, and self-excited vibration does not occur. Conversely, the discharge pressure Pd of the hydraulic pump 3a
a is from the set pressure p7 of the relief valve 30a to the set pressure Pc
Even if the pressure acting on the pilot port 17a of the switching valve 12a suddenly drops to a pressure higher than the set pressure Pc by the cracking pressure of the check valve 14a, the check valve 14a then closes and the hydraulic pressure Pump 3a and pilot port 17a are connected to throttle 16a
Since it is connected only through the pilot port 17a
The pressure gradually approaches the set pressure pc. Therefore, the switching valve 12a is slowly switched from the b position to the a position, so the discharge flow rate Q of the hydraulic pump 3a increases gradually. In this case, as described above, the discharge pressure pda 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 Pda is also gradual, and self-excited vibration does not occur. This also applies to the hydraulic pump 3b side.

Figure 8 shows the switching valve 12a and check valve 13 shown in Figure 7.
FIG. 3 is a cross-sectional view showing the structure of a valve device that combines valve a, 14a, chamber 15a, and throttle 16a. 18 in the figure
19 is a spool slidably provided within the valve body 18; and 20 is a spring provided between the valve body 18 and the spool 19. 21 is the poppet, 22 is the valve body 1
8 and the poppet 21, and the poppet 21 and the spring 22 constitute a check valve 13a.

23 is a poppet, and 24 is a spring provided between the valve body 18 and the poppet 23. The poppet 23 and the spring 24 constitute a check valve 14a. And check valve 1
One end of 3a, 14a is connected to the hydraulic pump 3a, and the other end is connected to the chamber 15a and the pilot boat 17a of the switching valve 12a. , 25 is a boat connected to the pressure reducing valve 11b, 26 is a boat connected to the cylinder chamber 10a, and 27 is a boat connected to the hydraulic pump 3a.

In this valve device, the boat 27 and the chamber 15a communicate with each other via the check valves 13a, 14a and the throttle 16a, so when the discharge pressure pda increases, the pressure within the chamber 15a increases. When the discharge pressure p1 is lower than the set pressure pc, the pressure inside the chamber 15a is also lower than the set pressure pc, so the spool 1
9 is pushed to the right by the spring 20, and the boat 25 and boat 26
The two are connected. Further, when the discharge pressure pda becomes higher than the set pressure pc, the pressure inside the chamber 15a increases to the set pressure pc.
The spool 19 moves to the left against the spring 20, and the boat 27 and the boat 26 communicate with each other. In this state,
When the discharge pressure pda becomes lower than the set pressure p0, the pressure inside the chamber 15a becomes lower than the set pressure Pc, and the spring 2
0 causes the spool 19 to move to the right, and the boat 25 and boat 2
6 is connected.

FIG. 9 is a diagram showing another input control device for a hydraulic pump according to the present invention. In the figure, 31a and 31b are hydraulic power sources;
32a and 32b are hydraulic power sources 3], servo valves connected to a and 31b, 33a and 33b are springs of the servo valves 32a and 32b, and 34a, 34b, 35a and 35b are servo valves 32
At pilot ports a and 32b, pilot boat 3
4a and 34b are supplied with the discharge pressure of the hydraulic pumps 3a and 3b, that is, their own discharge pressure, and the pilot boat 35
The discharge pressure pda and Path are set to the set pressure P by the switching valves 12a and 12b in a and 35b. When the pressure is lower, the discharge pressure of the hydraulic pumps 3b and 3a, that is, the discharge pressure of other hydraulic pumps, is supplied via the pressure reducing valve 11b and Ila,
When the discharge pressure p+1aq'Pclb is higher than the set pressure pc, the discharge pressure of the hydraulic pumps 3a and 3b, that is, their own discharge pressure is supplied.

36a and 36b are servo pistons connected to the servo valves 32a and 32b, and the displacement of the servo pistons 36a and 36b controls the displacement volume, that is, the tilt angle of the hydraulic pumps 3a and 3b.

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

In this input control device, the amount of displacement of the spool 37 (control member) is determined by the force of the spring 33a and the pilot port 34a.
, the total value of the force due to the pressure acting on 35a. For example, 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. By cylinder chamber 4
2 and the 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 amount of displacement of the hydraulic pump 3a has a value corresponding to the amount of displacement of the spool 37, and therefore the tilting angle of the hydraulic pump 3a has a value corresponding to the amount of displacement 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 pilot ports 34a, 3.
5a, and the tilting angle of the hydraulic pump 3a has a value corresponding to the amount of displacement of the spool 37. Therefore, in this input control device, the input control shown in FIG. Similarly to the device, the discharge flow rate Q of the hydraulic pumps 3a and 3b is controlled.

In the above embodiment, if the volumes of the chambers 15a and 15b and the aperture ratios of the apertures 16a and 16b are appropriately selected, the responsiveness when the discharge pressures P da and P db increase, and the discharge pressures p cla and pdb become as follows. It is possible to set the delay time to an appropriate value when the power decreases.

〔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]

Figure 1 is a diagram showing the input control device of a conventional hydraulic pump, and Figure 2 is a diagram showing the discharge pressure p in the case of the input control device shown in Figure 1.
A graph showing the relationship between da and discharge flow rate Q, FIG.
A graph showing the relationship between the discharge pressure P (Ill) and the input torque T in the case of the input control device shown in FIG.
5 is a graph showing the relationship between the discharge pressure Pda and the discharge flow rate Q in the case of the input control device shown in FIG. 4, and FIG. 6 is a graph showing the relationship between the discharge pressure Pda and the discharge flow rate Q in the case of the input control device shown in FIG. A graph showing the relationship with input torque T, FIG. 7 is a diagram showing the input control device for a hydraulic pump according to the present invention, and FIG. 8 is a structure of a valve device combining the switching valve, chamber, etc. shown in FIG. 7. 9 is a sectional view showing another input control device for a hydraulic pump according to the present invention, and FIG. 10 is a sectional view showing the structure of a regulator of the input control device shown in FIG. 9. 1... Prime mover 3a, 3b... Variable capacity cedar hydraulic pump 4a, 4b...
Regulators 5a, 5b...Control cylinders 6a, 6b...Control pistons 7a, 7b...Springs 8a, 8b...Piston ronds 9a, 9b...Cylinder chambers 10a, 10b...Cylinder chamber 11. a, 11 b...pressure reducing valve 12a, 12b-
...Switching valves 13a, 13b, 14a, 14b--Check valves 15a, 15b...Chambers 16a, 1
6b-Aperture 1.7a, 17b...Pilot boat 3
1a, 31b... Hydraulic power source 32a, 32b -
Servo valves 33a, 33b--Springs 34a, 34b--Pilot boats 35a, 35b--Pilot boats 36a, 36b
... Servo piston representative patent attorney Junnosuke Nakamura 11 Fig. 1-2 Fig. 1258175＾ Nagi on the mouth 1 [Force Fn a Spear 3 M Positive pressure on the mouth Pal a, N・4 Fig. 1-8 Fig. Pda Age 9

Claims (1)

[Claims] The displacement of two variable displacement cedar 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 the own discharge pressure and pressure reduction are provided at the other end of the control member. In an input control device for a hydraulic pump that applies the discharge pressure of another hydraulic pump via a valve, an input control device is provided between the pressure reducing valve and the control member, and when the own discharge pressure is lower than the set pressure, the pressure is applied via the pressure reducing valve. A switching valve is provided that causes the discharge pressure of another hydraulic pump to act on 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 chamber is connected to the pilot port of the switching valve. An input control device for a hydraulic pump, characterized in that two check valves and a throttle are connected in parallel and arranged in opposite directions on the upstream side of the chamber.