JP3076153B2 - Pump output control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling the output of a piston pump.

[0002]

2. Description of the Related Art When a pump whose discharge amount is variably controlled is driven by an engine, the relationship between the pump discharge flow rate and the pressure is controlled so as not to exceed a certain value, thereby maximizing the efficiency of the engine driving horsepower. It is known that it is frequently used (for example, JP-A-2-104993).

FIG. 8 shows an example of this. The discharge amount of a main pump 2 driven by an engine 1 changes according to the tilt angle of a swash plate (not shown).

In order to control the swash plate tilt angle, a regulator cylinder 3 is provided, and a piston 4 drives a lever 5 which is linked to the swash plate. The discharge pressure P is directly guided from the discharge passage 6 of the pump 2 to one oil chamber 3A of the cylinder 3, and the pressure Pc adjusted via the regulator valve 8 is guided to the other oil chamber 3B. The piston 4 is displaced to a position where these pressures are balanced, and the tilt angle of the swash plate is controlled in accordance with the discharge pressure.

The regulator valve 8 is composed of two serially arranged plungers 1 responsive to a control pressure Pr from a proportional pressure reducing valve 9.
The pressure Pc is controlled by reducing the pressure from the discharge passage 6 by controlling the pressure from the discharge passage 6 to a position that balances the control springs 11A and 11B for feeding back the actual tilt angle of the swash plate.

The proportional pressure reducing valve 9 reduces the discharge pressure from the sub-pump 13 driven in the same manner as the pump 2 in accordance with the discharge pressure P of the main pump 2. As shown in FIG. A pressure Pr that is linearly proportional to the pressure Pr. For this reason, the pilot plunger 14 of the proportional pressure reducing valve 9
The discharge pressure P is guided to the sub-pump 13, and the discharge pressure of the sub-pump 13 is reduced in accordance with this pressure.

When the pressing force from the plungers 10A and 10B responsive to the control pressure Pr becomes larger than the spring reaction force of the control springs 11A and 11B, the regulator valve 8 switches to the B position, and the pressure in the oil chamber 3B is discharged from the pump. Increase to pressure P. Regarding piston 4,
Since the pressure receiving area of the oil chamber 3B is larger than that of the oil chamber 3A, when the two chambers have the same pressure, the piston 4 moves in the extending direction to change the tilt angle of the swash plate, thereby changing the pump discharge amount. Decrease Q.

At the same time, the movement of the piston 4 compresses the control springs 11A and 11B and increases the reaction force of the springs. When this coincides with the pressing force of the plungers 10A and 10B, the regulator valve 8 is switched to the neutral C position.
The position is switched to the position, and the swash plate tilt angle is maintained.

On the other hand, plungers 10A and 10B
When the pressing force from the swash plate decreases, the regulator valve 8 is switched to the A position by the repulsive force of the control springs 11A and 11B pushed by the swash plate drive lever 5, and the oil chamber 3
Release the pressure of B to the tank side. Then, the piston 4 is pushed back in the contracting direction to the opposite side to the above, thereby changing the tilt angle of the swash plate and increasing the pump discharge amount Q.

Therefore, as shown in FIG. 10, as the control pressure Pr increases, the pump discharge amount Q decreases.

The control pressure Pr for pressing the plungers 10A and 10B is proportional to the pump discharge pressure P as shown in FIG.
The characteristic that the discharge amount Q decreases is obtained.

In this case, the plungers 10A, 10A
Control springs 11A and 11B for repelling B
After one control spring 11A is compressed by a certain amount, the other control spring 11B is set to work for the first time. Therefore, the spring reaction force of the control springs 11A and 11B with respect to the control pressure Pr is halfway. The linear characteristic will bend, which results in PQ =
The pump output characteristic approximates to a constant, that is, a hyperbolic characteristic with a constant horsepower.

[0013]

Incidentally, in order to actually adjust the initial load in addition to the control springs 11A and 11B, another control spring 11C is interposed, and according to the load of the control spring 11C, FIG.
Can be adjusted.

That is, the relative spring reaction force changes according to the strength of the control spring 11C, and the spring 1
The position of the point C1 moves in relation to the control pressure Pr in accordance with the initial load of 1C.

In FIG. 10, the position of the characteristic bending point C2 is determined by the control springs 11A and 11B.
The position is adjusted by adjusting the spring seat so that the contact position with respect to the lever 5 is adjusted.

However, since the output characteristics are adjusted by matching the positions of the plurality of springs due to repetition of trial and error, the adjustment is very troublesome and troublesome.

When the pump discharge amount is controlled by using the external pressure, the control springs 11A and 11B are used.
As shown in FIG. 11, the discharge amount Q has a characteristic of being bent on the way to the external signal pressure Pnc as shown in FIG. It becomes difficult.

In FIG. 13, the ideal characteristic of the output horsepower of the pump shifts in the direction passing through the origin as shown by the broken line. However, even if the external pressure Pm guided to the proportional pressure reducing valve 9 is changed, Since the pump output horsepower characteristic of FIG. 15 can move only in the horizontal axis direction of FIG. 15, as shown in FIG.
The deviation from the ideal characteristic becomes very large. In the configuration of FIG. 8, the control pressure Pr with respect to the external pressure Pm is the same as that in FIG.
In the direction of the vertical axis.

Therefore, the present invention facilitates the adjustment of the required output horsepower of the pump, makes the characteristic of the pump discharge amount with respect to the external pressure an ideal straight line, and increases the approximation accuracy in the output horsepower change control. With the goal.

[0020]

A first aspect of the present invention provides a regulator cylinder for adjusting a tilt angle of a swash plate, a regulator valve for controlling a pressure guided to the regulator cylinder, and a control pressure corresponding to a pump discharge pressure. A pump that responds and presses a regulator valve, and a control spring that feeds back the amount of displacement of a regulator cylinder to the regulator valve, has a predetermined initial pressure in a pump that increases and decreases the pump discharge amount according to the pump discharge pressure. A first proportional pressure reducing valve that reduces the pump discharge pressure at a predetermined pressure reducing ratio, and a first proportional pressure reducing valve that has a predetermined initial pressure different from the first proportional pressure reducing valve and that also reduces the pump discharge pressure. The pressure is reduced by the second proportional pressure reducing valve that reduces the pressure at different predetermined pressure reducing ratios, and by the first and second pressure reducing valves. A low-pressure selection valve that selects the lower of the forces, a plunger that presses the regulator valve in response to the pressure of the low-pressure selection valve, and a control in which the spring constant that pushes the regulator valve back against the plunger is constant. And a spring.

According to a second aspect of the present invention, in the first aspect, the first
And a spring for initial pressure adjustment of the second proportional pressure reducing valve.

According to a third aspect of the present invention, in the first aspect, the first
And a pilot plunger for adjusting the output of the second proportional pressure reducing valve with respect to the external pressure.

According to a fourth aspect, in the third aspect, the first aspect is provided.
And the second proportional pressure reducing valve, a pilot plunger responsive to the pump discharge pressure and a pilot plunger for adjusting the pressure reducing valve output with respect to the external pressure act from the same or opposite directions.

According to a fifth aspect of the present invention, in the first aspect, the plunger comprises a plurality of serially arranged plungers, and a pressure chamber for introducing external pressure is formed between the two plungers.

[0025]

The two proportional pressure reducing valves have different initial pressures and the pump discharge pressures are reduced at different pressure reducing ratios. The lower pressure selected by the two pressure reducing valves is selected by the low pressure selecting valve. Then, the smaller of the two control pressures is used as the control pressure, and a pressure having a linear waveform that bends halfway with respect to the pump discharge pressure can be created.

When the regulator valve is pressed by a plunger which is bent in the middle and has a linear characteristic pressure, and the regulator valve is pushed back by a control spring having a constant spring constant, the horsepower is kept constant as in the prior art. Thus, a pump output characteristic approximate to the hyperbolic characteristic is obtained.

In this case, in the figure where the vertical axis indicates the pump discharge amount and the horizontal axis indicates the pump discharge pressure, the point at which the pump discharge amount falls is adjusted by the proportional pressure reducing valve (for example, The adjustment of the bending point in the middle can be performed independently by the first proportional pressure reducing valve (second proportional pressure reducing valve) having another initial pressure.

As described above, if the adjustment can be made independently at the two initial pressures, the adjustment to the required output characteristics of the pump becomes easy, and the trial and error becomes unnecessary.

According to the second aspect of the present invention, when the initial pressure is adjusted by the spring, the setting of the initial pressure is facilitated, and the configuration is simplified.

According to the third aspect of the present invention, the external pressure is guided to the pilot plunger for adjusting the output of the proportional pressure reducing valve with respect to the external pressure, whereby the output horsepower of the pump can be changed.

In this case, when the external pressure is changed, the pressure coming out of the low pressure selection valve is taken on the vertical axis and the pump discharge pressure is taken on the horizontal axis. In FIG. 5, each of the first and second pressure reducing valves is shown. If the output sensitivity to the external pressure is changed, the linear characteristic that bends in the middle can move in an oblique direction.

In FIG. 6, the vertical axis indicates the pump discharge amount and the horizontal axis indicates the pump discharge pressure.
The pump output characteristics shift diagonally. That is, by independently adjusting each sensitivity of the pressure reduced by the pressure reducing valve to the external pressure, the bending point of the pump output characteristic moves in the direction passing through the origin. This greatly reduces the amount of deviation from the ideal horsepower diagram.

In the fourth aspect of the present invention, when the pilot plunger for adjusting the output of the pressure reducing valve against the external pressure acts on the pilot plunger responding to the pump discharge pressure in the same direction or the opposite direction, the external pressure is increased. The pump output can be freely changed in the increasing direction and the decreasing direction.

In the fifth invention, the plunger of the first invention is constituted by two plungers connected in series, and when a pressure chamber for introducing an external pressure is formed between the two plungers, an external output is generated. Since the control spring has a constant spring constant, the pump discharge amount changes linearly with respect to the external output.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, in this example, two proportional pressure reducing valves 21 and 22 are provided in parallel. A spring 23 that works in the same direction as the pump discharge pressure P is attached to the first proportional pressure reducing valve 21 on the same side as the pilot plunger 22 that responds to the pump discharge pressure P. This spring 2
Since the force of 3 is applied even when there is no pump discharge pressure P,
The control pressure Pr1 generated by the proportional pressure reducing valve 21 has a predetermined value (initial pressure) Pi1 even when the pump discharge pressure P is zero.

The second proportional pressure reducing valve 31 also has the same configuration as the above-described proportional pressure reducing valve 21. The pump discharge pressure P from the same side as the pilot plunger 32 responding to the pump discharge pressure.
Spring 33 acting in the same direction as
Has an initial pressure Pi2 as the control pressure Pr2 created by

However, this initial pressure Pi2 is larger than the above-mentioned initial pressure Pi1, and the pressure reduction ratio β (the value obtained by dividing the pressure difference of Pr2 by the pressure difference of P) β of the proportional pressure reducing valve 31 is the first proportional pressure reduction. It is smaller than the pressure reduction ratio α of the valve 21.

The two proportional pressure reducing valves 21 and 31 provide different control pressures Pr1 and Pr proportional to the pump discharge pressure P.
2 are made as shown in FIGS.

In the proportional pressure reducing valves 21 and 31, pilot plungers 24 and 34 for adjusting the pressure reducing valve output with respect to the external pressure Pm are provided on the opposite side to the pilot plungers 22 and 32 which respond to the pump discharge pressure P. Is provided. In this case, when the external pressure Pm is changed, the proportional characteristics of the control pressures Pr1 and Pr2 move in the vertical axis direction in FIGS. 2 and 3, and the amount of movement is determined by the pressure receiving areas of the pilot plungers 24 and 34.

The low pressure selection valve 41 includes two proportional pressure reducing valves 2
The lower one of the pressures Pr1 and Pr2 depressurized at 1, 31 is selected. As shown in FIG. 4, while the pump discharge pressure P is small, the first value is determined from Pi2> Pi1.
The control pressure Pr1 from the proportional pressure reducing valve 21 is selected, and as the discharge pressure P increases, the pressure Pr1 increases more steeply than the pressure Pr2. Therefore, after the magnitude relationship between Pr1 and Pr2 is reversed, the second The pressure Pr2 from the proportional pressure reducing valve 31 is selected.

In response to the pressure Pr from the low-pressure selection valve 41, only two plungers 10A and 10B in series press the regulator valve 8, and only one plunger is provided to feed back the actual tilt angle of the swash plate. Control spring 4
3 pushes the regulator valve 8 back against the plungers 10A, 10B. 44 is a control spring for adjusting the initial load.

In the other components, the same parts as those of the conventional example are denoted by the same reference numerals, and description thereof will be omitted.

Here, the operation of this example will be described.

In this example, there is only one control spring (43) for feeding back the actual tilt angle of the swash plate, but it is bent halfway between the two plungers 10A and 10B which press the regulator valve 8. When the pressure Pr of the linear characteristic in FIG. 4 is derived, as shown by the solid line in FIG. 6, a pump output characteristic approximate to a hyperbolic characteristic with a constant horsepower is obtained.

In this case, the point C1 in FIG. 6 is adjusted by the control pressure Pr1, ie, the initial load of the control spring 23 of the first proportional pressure reducing valve 21, and the point C2 is adjusted by the control spring 33 of the proportional pressure reducing valve 31. Can be performed independently with the initial load of That is, if the C2 point is shifted,
Under such influence, the C1 point does not shift.

If the points C1 and C2 can be adjusted independently as described above, the adjustment to the required output characteristics of the pump becomes easy, and the time required for the adjustment can be shortened.

Further, in this case, since the initial pressure is adjusted by the spring, the setting of the initial pressure is easy and simple.

Also, the two plungers 10A, 1 in series
0B, the external pressure P
When the pump discharge amount is controlled by introducing nc, since only one control spring 43 opposes the external pressure Pnc, the pump discharge amount Q changes linearly with respect to the external pressure Pnc in FIG. Ideal characteristics can be obtained. In this case, the inclination of the pump discharge amount is determined by the spring constant of the control spring 43, and the spring constant of the control spring 44 for adjusting the initial load does not influence.

Further, when the output horsepower of the pump is controlled to be changed using another external pressure Pm, the external pressure P
When m is changed, as shown in FIG. 5 (an example in which Pm is changed to a larger side), the straight line characteristic that bends in the middle shifts in a diagonally downward direction indicated by an arrow. As shown in FIGS. 2 and 3, the moving directions of the pressures Pr1 and Pr2 are both ordinate when viewed alone, but move obliquely when viewed from the overall characteristics.

Since the pump output characteristic having the bending point C2 in the same way shifts not in the horizontal axis direction but in the diagonal direction as shown in FIG. 6 due to the oblique movement of the straight line characteristic that is bent in the middle, the external pressure Pm Control pressure Pr
By independently adjusting the sensitivities of 1 and Pr2 (the amount of movement in the vertical axis direction in FIG. 5), the bending point C2 can be moved in the direction passing through the origin in FIG.

As a result, the amount of deviation from the ideal horsepower diagram can be greatly reduced.

Since the above sensitivities are determined by the pressure receiving areas of the pilot plungers 24 and 34, setting of the sensitivities is easy.

In FIG. 1, two plungers 10A,
Two pressures, ie, the control pressure Pr and the external signal pressure Pnc, are led to 10B, but they may be interchanged and led. The control springs 23 and 33 are provided on the opposite sides of the pilot plungers 22 and 32 responsive to the pump discharge pressure P, and the pilot plungers 24 and 34 for adjusting the pressure reducing valve output with respect to the external pressure are provided on the same side as the pilot plungers 22 and 32. Can also be provided.

In the embodiment, the feedback method for the regulator valve 8 has been described by the force feedback, but the present invention can also be applied to the position feedback. Further, not only the horsepower control of the single pump, but also a plurality of pilot plungers responsive to the pump discharge pressure P or a multi-stage plunger shown in FIG. 7 enables the total horsepower control of a plurality of pumps.

[0055]

According to the first aspect of the invention, a regulator cylinder for adjusting the tilt angle of the swash plate, a regulator valve for controlling the pressure guided to the regulator cylinder, and a control pressure corresponding to the pump discharge pressure. A plunger that presses the regulator valve by pressure and a control spring that feeds back the displacement amount of the regulator cylinder to the regulator valve. A first proportional pressure reducing valve for reducing the pressure by a predetermined pressure reducing ratio, and a predetermined initial pressure different from that of the first proportional pressure reducing valve, and the pump discharge pressure is also different from the first proportional pressure reducing valve. A second proportional pressure reducing valve for reducing pressure at a predetermined pressure reducing ratio, and a pressure reducing pressure reduced by the first and second pressure reducing valves. A low pressure selection valve that selects the lower one of the pressures, a plunger that presses the regulator valve in response to the pressure of the low pressure selection valve, and a control spring with a constant spring constant that pushes the regulator valve back against the plunger. As a result, the pump output characteristic approximated to the hyperbolic characteristic with a constant horsepower as in the related art is obtained, and the adjustment of the point where the pump discharge rate falls in the pump output characteristic diagram is performed by using one of the two proportional pressure reducing valves. In addition, the adjustment of the bending point in the middle can be performed independently by the other pressure reducing valve, so that the adjustment to the required output characteristic of the pump becomes easy and the time required for the adjustment can be shortened.

According to the second invention, the first invention is the first invention.
And a spring for adjusting the initial pressure of the second proportional pressure reducing valve. In addition to the effects of the first invention, the setting of the initial pressure is facilitated and the configuration is simplified.

In the third invention, the first invention
And a pilot plunger for adjusting the output of the second proportional pressure reducing valve with respect to the external pressure. In addition to the effect of the first aspect, the bending point of the pump output characteristic is directed in a direction passing through the origin of the pump output characteristic diagram. The deviation from the ideal horsepower diagram can be greatly reduced.

According to the fourth aspect, the first aspect of the third aspect is provided.
And the second proportional pressure reducing valve, the pilot plunger responsive to the pump discharge pressure and the pilot plunger for adjusting the pressure reducing valve output with respect to the external pressure act from the same direction or the opposite direction. The output can be freely changed in the increasing direction and the decreasing direction.

According to a fifth aspect of the present invention, in the first aspect, the plunger includes a plurality of plungers connected in series, and a pressure chamber for introducing an external signal pressure is formed between the two plungers. The control spring against the output is a control spring having a constant spring constant, and the pump discharge amount can be changed linearly with respect to the external signal output.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of one embodiment.

FIG. 2 is a characteristic diagram of a control pressure Pr1.

FIG. 3 is a characteristic diagram of a control pressure Pr2.

FIG. 4 is a characteristic diagram of a control pressure Pr.

FIG. 5 is a characteristic diagram of a control pressure Pr with respect to an external pressure Pm.

FIG. 6 is a characteristic diagram of the output horsepower of the pump with respect to the external pressure Pm.

FIG. 7 is a sectional view of a multi-stage pilot plunger according to another embodiment.

FIG. 8 is a conventional hydraulic circuit diagram.

FIG. 9 is a characteristic diagram of a conventional control pressure Pr.

FIG. 10 is a conventional pump output characteristic diagram.

FIG. 11 is a characteristic diagram of a pump discharge amount with respect to a conventional external pressure Pnc.

FIG. 12 is a characteristic diagram of an ideal pump discharge amount with respect to an external pressure Pnc.

FIG. 13 is an output horsepower characteristic diagram of a pump for explaining the operation of the conventional example.

FIG. 14 is a characteristic diagram of a control pressure Pr with respect to a conventional external pressure Pm.

FIG. 15 is a characteristic diagram of the output horsepower of the pump with respect to the conventional external pressure Pm.

[Explanation of symbols]

2 Main Pump 3 Regulator Cylinder 8 Regulator Valve 10A, 10B Plunger 21 First Proportional Pressure Reducing Valve 22 Pilot Plunger 23 Controls, Pulling 24 Pilot Plunger (for Adjusting Reducing Valve Output to External Pressure) 31 Second Proportional Pressure Reducing Valve 32 Pilot Plunger 33 Control spring 34 Pilot plunger (for adjusting pressure reducing valve output against external pressure) 41 Low pressure selecting valve 43 Control spring 45 Pressure chamber

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F04B 49/00 341 F04B 1/26

Claims (5)

(57) [Claims] 1. A regulator cylinder for adjusting a tilt angle of a swash plate, a regulator valve for controlling a pressure guided to the regulator cylinder, and a plunger for pressing the regulator valve in response to a control pressure corresponding to a pump discharge pressure. A regulator valve having a control spring that feeds back a displacement amount of a regulator cylinder, and a pump that increases or decreases a pump discharge amount in accordance with a pump discharge pressure. A first proportional pressure reducing valve for reducing the pressure, and a predetermined initial pressure different from that of the first proportional pressure reducing valve, and the pump discharge pressure is similarly reduced by a predetermined pressure reducing ratio different from that of the first proportional pressure reducing valve. A second proportional pressure reducing valve and a pressure which is lower of the pressures reduced by the first and second pressure reducing valves , A plunger that presses the regulator valve in response to the pressure of the low pressure selection valve, and a control spring with a constant spring constant that pushes the regulator valve back against the plunger. Pump output control device. 2. The apparatus according to claim 1, further comprising a spring for adjusting an initial pressure of the first and second proportional pressure reducing valves.
3. The output control device for a pump according to 1. 3. The output control device for a pump according to claim 1, further comprising a pilot plunger for adjusting an output of the first and second proportional pressure reducing valves with respect to an external pressure. 4. The first and second proportional pressure reducing valves are such that a pilot plunger responsive to a pump discharge pressure and a pilot plunger for adjusting the pressure reducing valve output with respect to the external pressure act in the same direction or in opposite directions. The pump output control device according to claim 3, characterized in that: 5. The pump according to claim 1, wherein the plunger comprises a plurality of plungers in series, and a pressure chamber for introducing an external pressure is formed between the plungers. Output control device.