JPH11132154A - Capacity control device of working machine pump for working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacity control device of a working machine pump for a working vehicle which improves operability of the working machine and simultaneously reduces hydraulic loss, by providing capacity of the working machine pump according to engine speed, load to the working machine, and manipulated variable of a working machine lever. SOLUTION: This capacity control device of a working machine pump for a working vehicle is equipped with a working machine load detecting means 13 for detecting load to a working machine, a high-load and small-capacity control signal generating means 9 which outputs control signals for reducing pump capacity with increasing of the load to the working machine, and a first selecting means 12 for selecting a control signal with larger pump capacity of respective control signals output by the high-load small-capacity control signal generating means 9 and a low-speed small-capacity control signal generating means 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement control device for a working machine pump for a working vehicle.

[0002]

2. Description of the Related Art As shown in FIG. 13, in a work vehicle in which the power of an engine is used for traveling via a torque converter and for a work machine via a work machine pump, the engine speed varies depending on the work machine load. There is a first related art in which the hydraulic consumption torque e (proportional to the load pressure P and the pump displacement V) is controlled to be constant irrespective of the engine speed so as not to cause the problem. Further, there is a second conventional technique which improves the acceleration performance of the engine at low speeds by reducing the oil consumption torque d at low engine speeds at lower speeds (shown by oblique lines) as compared with the first conventional technique. .

A first prior art will be described with reference to FIG. The engine 1 includes a work machine pump 2 and a fixed displacement pump 3
And drive. Pump displacement control means for controlling a pump displacement V (cc / rev), which is a discharge amount per one rotation of the work machine pump 2, includes a servo cylinder 4 and a pump displacement control valve 5. When the load pressure P of the work machine pump 2 increases, the high-load / small-capacity pressure reducing valve 9 moves in the direction of the position a, and becomes constant pressure by the pilot relief valve 7 connected to the discharge pipe of the fixed displacement pump 3. The controlled pilot source pressure is reduced to a high pilot pressure pi and output to the pilot portion of the pump displacement control valve 5. Therefore, the pump displacement control valve 5 moves in the direction of the position b, and the pump displacement V is controlled to be small. When the load pressure P decreases, the high-load / small-capacity pressure reducing valve 9 moves in the direction b, and the pilot source controlled to a constant pressure by the pilot relief valve 7 connected to the discharge pipe of the fixed displacement pump 3. The pressure is reduced to a low pilot pressure pi and output to the pilot section of the pump displacement control valve 5. Therefore, the pump displacement control valve 5 moves in the direction of the position a, and the pump displacement V is controlled to be large.

Referring to FIG. 15, the pump displacement control characteristic of the high load / small displacement pressure reducing valve 9 will be described. Work machine pump 2 on the horizontal axis
And the vertical axis represents the pilot pressure pi output from the high load / small capacity pressure reducing valve 9 and the pump capacity V of the work machine pump 2. The pilot pressure pi is an increasing function of the load pressure P. Since the minimum value Vmin and the maximum value Vmax of the pump displacement V are mechanically set by stoppers (not shown), the pilot pressure pi is lower than the load pressure P1 and higher than the load pressure P2. Therefore, the minimum value Vmin and the maximum value Vmax are constant even if the pilot pressure pi changes. When the load pressure is from P1 to P2, the pump capacity decreases substantially linearly from Vmax to Vmin (indicated by V = aP + b for simplicity) according to the pilot pressure pi. Therefore, when the load pressure is Pi in FIG. 15, the pump displacement is Vi, and the pump discharge amount Q (liter / m) with respect to the engine speed N is plotted with the engine speed N on the horizontal axis in FIG. If the pump discharge amount Q of the machine pump 2 is taken, a straight line (Q = Vi ·
N). As described above, the pump discharge amount Q (liter / m) with respect to the engine speed N is a straight line (Q = Vmin.multidot.V) where the pump displacement Vmin at the time of high load pressure P2 is a proportional constant.
N) to a straight line (Q = Vmax · N) that uses the pump capacity Vmax at the low load pressure P1 as a proportionality constant and changes in accordance with the load pressure P.

Referring to FIG. 17, a second prior art will be described. In FIG. 14, a throttle 6 is interposed between a fixed displacement pump 3 and a pilot relief valve 7, and a low speed / small volume pressure reduction controlled by a differential pressure across the throttle 6 instead of the high load / small volume pressure reducing valve 9. It is the same as the first prior art except that the valve 8 is installed. When the engine speed N is detected by the differential pressure across the throttle 6 and the differential pressure acts on the low-speed / small-capacity pressure reducing valve 8, when the engine speed N is low (the differential pressure across the throttle 6 is small), the engine speed N is reduced. The small-capacity pressure reducing valve 8 moves in the direction of the position b, reduces the pilot source pressure controlled by the pilot relief valve 7 to a constant pressure to a high pilot pressure pi, and outputs it to the pilot portion of the pump displacement control valve 5. Therefore, the pump displacement control valve 5 moves in the direction of the position b, and the pump displacement V is controlled to be small. When the engine speed N is high (the differential pressure across the throttle 6 is large), the low-speed / small-capacity pressure reducing valve 8 moves in the direction of the position a, and the pilot source pressure controlled to a constant pressure by the pilot relief valve 7. Is reduced to a low pilot pressure pi and output to the pilot section of the pump displacement control valve 5. Therefore, the pump displacement control valve 5 moves in the direction of the a position, and the pump displacement V is controlled to be large.

Referring to FIG. 18, the pump displacement control characteristics of the low speed / small displacement pressure reducing valve 8 will be described. Engine speed N on the horizontal axis
The pilot pressure pi output from the low-speed / small-capacity pressure reducing valve 8 and the pump displacement V of the work machine pump 2 are plotted on the vertical axis.
Although the pilot pressure pi is a decreasing function of the engine speed N, the minimum value Vmin and the maximum value Vmax of the pump displacement V are mechanically set by stoppers (not shown).
Below the engine speed N1 and above the engine speed N2, the minimum value Vmin and the maximum value Vmax are constant even if the pilot pressure pi changes, and the engine speeds N1 to N
In 2, the pump capacity V is Vmi according to the pilot pressure pi.
substantially linear from n to Vmax (for simplicity, V
= CN + d). Therefore, the pump discharge amount Q (liter / m) with respect to the engine speed N is shown in FIG.
When the engine speed N is plotted on the horizontal axis and the pump discharge amount Q of the work machine pump 2 is plotted on the vertical axis in FIG. Q = Vmin · N), and when the engine speed exceeds N2, a straight line (Q = Vmax ·
N). Also, from the engine speed N1 to N2,
In FIG. 18, the pump displacement Vi at the engine speed Ni is shown.
Is Vi = cNi + d, so in FIG. 19, the pump discharge amount Qi = Vi · Ni = (c) when the engine speed is Ni.
Ni + d) · N = a ^{(cNi 2 + d · Ni)} . In general, as shown by a thick line m, a quadratic curve (indicated by a straight line m for simplicity) where Q = (cN ² + d · N) is obtained.

As shown in FIG. 20, the working machine driving force is Fv1
From Fh2 to Fv2, the traction force of the vehicle is reduced from Fh1 to Fh2, and the increase in the operation amount of the work implement lever and the decrease amount of the engine speed N match the operator's feeling to improve the operability. As shown in FIG. 21, the hydraulic consumption torque (pump capacity V) is increased from h to i in response to the increase in the operation amount of the work implement lever with respect to the engine torque c, and is matched with the absorption torque a of the torque cock converter. There is a third conventional technique for lowering the engine speed N.

The third prior art will be described with reference to FIG. In FIG. 14 showing the first prior art, a pilot valve selected by a shuttle valve group 21 between the relief valve 7 and the pilot portion of the pump displacement control valve 5 instead of the high load / small displacement pressure reducing valve 9 is shown. It is the same as the first prior art except that a small-operation / small-capacity pressure reducing valve 11 controlled by the maximum pilot pressure among the 16 and 17 pilot pressures is provided. When the operation amount of the pilot valves 16 and 17 is small (the pilot pressure is low), the small operation and small capacity pressure reducing valve 11 is used.
Moves to the position b, reduces the pilot source pressure controlled to a constant pressure by the pilot relief valve 7 to a high pilot pressure pi, and outputs the pilot pressure to the pilot section of the pump displacement control valve 5. Therefore, the pump displacement control valve 5 moves in the direction of the b position, and the pump displacement V is controlled to be small. Also,
When the operation amounts of the pilot valves 16 and 17 are large (the pilot pressure is high), the small operation / small capacity pressure reducing valve 11 moves in the direction of the position a to reduce the pilot base pressure controlled by the pilot relief valve 7 to a constant pressure. The pressure is reduced to a low pilot pressure pi and output to the pilot section of the pump displacement control valve 5. Therefore, the pump displacement control valve 5 moves in the direction of the position a, and the pump displacement V is controlled to be large.

According to FIG. 23, a small operation and small capacity pressure reducing valve 11 is shown.
Will be described. The horizontal axis represents the lever operation amount S, and the vertical axis represents the pilot pressure pi output by the small operation / small capacity pressure reducing valve 11 and the pump displacement V of the work machine pump 2. The pilot pressure pi is a decreasing function of the lever operation amount S. However, since the minimum value Vmin and the maximum value Vmax of the pump displacement V are mechanically set by stoppers (not shown), the pilot operation pi is less than the lever operation amount S1 and the lever operation amount is smaller. Above the quantity S2, the minimum value Vmin and the maximum value Vmax are constant even if the pilot pressure pi changes. Lever operation amount from S1 to S
In 2, the pump capacity is Vmin according to the pilot pressure pi.
From Vmax to Vmax (for simplicity, V =
eS + f). Therefore, when the lever operation amount is Si in FIG. 23, the pump displacement is Vi, and the pump discharge amount Q (liter / m) with respect to the engine speed N is obtained.
In FIG. 24, when the horizontal axis indicates the engine speed N and the vertical axis indicates the pump discharge amount Q of the work machine pump 2, a straight line (Q = Vi · N) having Vi as a proportionality constant is obtained. Thus, from the straight line (Q = Vmin · N) using the pump capacity Vmin at the time of the lever operation amount S1 as a proportional constant, from the straight line (Q = Vmax · N) using the pump capacity Vmax at the time of the lever operation amount S2 as the proportionality constant.
Until N), it changes according to the lever operation amount S.

[0010]

[Problems to be solved by the invention]

(1) In the first prior art shown in FIG. 14, as shown in FIG. 13, the hydraulic consumption torque e becomes constant irrespective of the engine speed, and even if the work equipment load increases in the low engine speed region, the engine margin is increased. The point that the torque can be secured is effective. However, when the excavation work is performed at the matching point A with the absorption torque of the torque converter in the high-speed region of the engine, the hydraulic consumption torque e is constant (P × V = constant). When the bucket lifting force increases, the lifting speed decreases and the matching point A does not decrease, so that the traveling traction force does not decrease. For this reason, as shown in FIG. 20, even if the work implement driving force increases from Fv1 to Fv2, the vehicle traction force becomes Fh1.
From Fh2 to Fh2, and the resultant force acting on the bucket does not follow the angle of repose of the sand pit.

(2) In the second prior art shown in FIG. 17, the pump discharge amount Q with respect to the engine speed N is shown by a thick line in FIG. 19 regardless of the magnitude of the load pressure P of the work machine pump 2. Therefore, there is a problem in that the working machine speed is reduced even when the hydraulic torque is small at the time of light load such as an increase in empty bucket load. Also, since the pump discharge amount Q at low engine speed is small, the rise in the starting pressure at which the work machine starts operating is delayed by the work machine operation valves 19 and 20 having the center bypass bleed-off, and the work machine start point at the low engine speed is reached. There is a problem in that the required dead area of the operation lever increases.

(3) In the third prior art shown in FIG. 22, the pump discharge amount Q with respect to the engine speed N increases or decreases according to the lever operation amount S as shown in FIG.
It is effective to reduce the hydraulic pressure loss by setting the necessary lever operation amount S, but on the other hand, the lever operation amount S is small,
When the engine speed N is low, the pump discharge amount Q is small. Therefore, in the working machine operating valves 19 and 20 of the bleed-off center bypass type as shown in FIG. When the engine is running at a low speed, there is a problem that the dead area of the operation lever required until the starting point of the work machine increases.

The present invention has been made in view of the above problems, and the desired capacity of the working machine pump is determined according to working conditions such as the engine speed, the working machine load, and the operation amount of the working machine lever. To improve work machine operability,
It is an object of the present invention to provide a displacement control device for a working machine pump for a work vehicle, which can reduce the hydraulic pressure loss.

[0014]

In order to achieve the above object, a displacement control device for a working machine pump for a working vehicle according to the first invention of the present application includes a working machine pump driven by an engine and a displacement control device. Pump displacement control means for controlling a pump displacement which is a discharge amount per rotation of a work machine pump, engine revolution detecting means for detecting an engine revolution speed, and control for decreasing the pump displacement as the engine revolution speed decreases. In a displacement control device for a working machine pump for a work vehicle having a low speed / small capacity control signal generating means for outputting a signal, a working machine load detecting means for detecting a working machine load, and a pump capacity increases as the working machine load increases. A high-load / small-capacity control signal generating means for outputting a control signal for reducing the load, a high-load / small-capacity control signal generating means and a low-speed / small-capacity control signal generating means. Among control signals, characterized in that it comprises a first selection means for selecting a control signal towards the pump capacity is large and outputs the pump displacement control means.

According to the first invention, of the control signals output from the high-load / small-capacity control signal generating means and the low-speed / small-capacity control signal generating means, the control signal having the larger pump capacity is the first control signal. The pump displacement control means is controlled by the selection by the selection means. For this reason, FIG. 1 described in the first prior art is used.
6, the pump discharge amount Q larger than the pump discharge amount Q shown by the thick line in FIG. 19 described in the second conventional technique is selected. That is, in FIG. 2, the pump discharge amount Q at the load pressure Pi is the engine speed N
Until Qi at the time of i, it changes on the line of Q = Vi · N (FIG. 1).
6), and changes when the engine speed N exceeds Ni (see FIG. 19). Thus, the engine speed N
Changes the portion shown by the solid line.

Therefore, for example, when the engine speed is N1, the pump discharge amount increases from Q1 to Q2 in accordance with the load pressure P. Work machine speed is ensured.
Further, since the pump discharge amount Q is ensured, even in the directional control valve having the center bypass bleed-off, the start-up pressure rises faster and the dead zone to the work machine start point decreases. Further, when the load pressure P is low, the pump discharge amount uniformly changes over Q = Vmax · N with respect to the engine speed N. Therefore, as in the second prior art shown in FIG. P
Irrespective of the above, a sharp change in the working machine speed with respect to the engine speed N is prevented and the operability is improved as compared with the case where the pump discharge amount Q changes on the thick line.

A displacement control device for a working machine pump for a work vehicle according to a second invention of the present application is a pump for controlling a working machine pump driven by an engine and a pump displacement which is a discharge amount per rotation of the working machine pump. Displacement control means, operation amount detection means for detecting the operation amount of the work implement lever, and small operation / small displacement control signal generation means for outputting a control signal for increasing the pump displacement as the operation amount of the work implement lever increases And a high-speed / small displacement control for outputting a control signal for reducing the pump displacement as the engine speed increases. Of the control signals output by the signal generating means, the high-speed / small-capacity control signal generating means, and the small-operation / small-capacity control signal generating means Characterized in that it comprises a second selecting means for outputting to the pump displacement control means to select the item.

According to the second invention, of the control signals output from the high-speed / small-capacity control signal generating means and the small-operation / small-capacity control signal generating means, the control signal having the larger pump capacity is the second control signal. The pump displacement control means is controlled by the selection by the selection means. For this reason, FIG.
Among the pump discharge amounts Q shown in FIG. 4, a pump discharge amount Q larger than the pump discharge amount Q controlled by the high-speed / small-capacity control signal generating means, which is indicated by a thick line in FIG. 5, is selected. That is, in FIG. 6, the pump speed changes to a pump discharge amount Qi at which the engine speed becomes Ni, and changes on the thick line.
Above i, the pump discharge amount Q at the time of the lever operation amount Si in FIG. In this manner, the pump discharge amount Q with respect to the engine speed N changes at the portion indicated by the solid line.

Therefore, when the operation amount of the work implement lever is increased to increase the pump displacement (hydraulic consumption torque) even in the high engine speed range, as shown in FIG. 7, it matches the absorption torque a of the torque converter. Engine speed N
Therefore, when excavation work is performed in a high-speed region, the vehicle traction force is reduced in response to an increase in the work equipment load (bucket lifting force), and the balance of the scooping operation of the earth and sand is improved.

A displacement control device for a working machine pump for a work vehicle according to a third aspect of the present invention is the first or second aspect, wherein
And a third selection means for selecting a control signal having a smaller pump capacity from the control signal selected by the selection means and the control signal selected by the second selection means and outputting the selected control signal to the pump capacity control means. I do.

According to the third invention, the control signal having the smaller pump capacity is selected by the third selection means from the control signal selected by the first selection means and the control signal selected by the second selection means. To control the pump displacement control means. Therefore, the operation and effect of the first invention in the low engine speed region and the operation and effect of the second invention in the high engine speed region are obtained as shown by oblique lines in FIG.

According to a fourth aspect of the present invention, there is provided a displacement control device for a working vehicle pump for a work vehicle according to the first invention, wherein the engine rotation detecting means is provided in a discharge line of a fixed displacement pump driven by the engine. The low-speed / small-capacity control signal generating means is a pilot source pressure controlled to a constant pressure by a pilot relief valve connected downstream of the throttle,
A low-speed / small-capacity pressure reducing valve that reduces the pressure at high engine speeds and high pressures at low engine speeds. The work implement load detecting means is a discharge pipe of the work implement pump. A high-load, small-capacity pressure reducing valve that reduces the output pressure of a small-capacity pressure reducing valve with a high load on the work machine and a low pressure with a low load on the work machine. And the first selecting means is configured.

According to the fourth aspect of the present invention, the first aspect of the present invention is configured as a fully hydraulic system. The operation and effect are the same as those of the first aspect of the invention, and have hydraulic features such as durability.

According to a fifth aspect of the present invention, there is provided a displacement control apparatus for a working machine pump for a work vehicle according to the second aspect, wherein the engine rotation detecting means is provided in a discharge line of a fixed displacement pump driven by the engine. The high-speed / small-capacity control signal generating means controls the pilot source pressure controlled to a constant pressure by a pilot relief valve connected downstream of the throttle,
A high-speed, small-capacity pressure reducing valve that depressurizes at a high engine speed and lowers at a low engine speed, and the operation amount detection means selects the maximum pilot pressure of the pilot source pressure reduced according to the operation amount of the pilot pressure control valve. Shuttle valve group,
The small-operation / small-capacity control signal generating means is a small-operation / small-capacity pressure-reducing valve that increases the output pressure of the high-speed / small-capacity pressure reducing valve with a small operation of the working machine lever and reduces the output pressure with a large number of working machine levers. The high-speed / small-capacity pressure reducing valve and the small-operation / small-capacity pressure reducing valve are connected in series to constitute a second selecting means.

According to the fifth aspect of the present invention, the second aspect of the present invention is configured as a fully hydraulic system. The operation and effect are the same as those of the second aspect of the invention, and have hydraulic features such as durability.

A displacement control device for a working machine pump for a work vehicle according to a sixth invention of the present application is characterized in that, in the third invention, the third selecting means is a shuttle valve.

According to the sixth aspect of the present invention, the third aspect of the present invention is configured as a fully hydraulic system. The operation and effect are the same as those of the third aspect of the invention, and have the features of a hydraulic type such as durability.

The displacement control apparatus for a working vehicle pump for a work vehicle according to the seventh invention of the present application is the third invention, wherein the pilot pump, a pilot relief valve for controlling the discharge pressure of the pilot pump to a constant pressure, and a pilot pump A proportional electromagnetic control valve for reducing the discharge pressure and outputting it to the pump displacement control means, the engine rotation detection means is a rotation sensor, and the work implement load detection means is a hydraulic sensor for detecting the discharge oil pressure of the work equipment pump. The operation amount detection means is an operation amount selection means for selecting the maximum value of the operation amount detection sensor of the work implement lever.The detection signal of each of these sensors is input, and as the engine speed decreases, the pump capacity is reduced. A low-speed / small-capacity control signal generating means for outputting a control signal for reducing, and a control signal for reducing pump capacity as the work equipment load increases A load and small displacement control signal generating means,
A first selecting means for selecting a control signal having a larger pump capacity from among the control signals output by the low speed / small capacity control signal generating means and the high load / small capacity control signal generating means; Small operation / small displacement control signal generating means for outputting a control signal for increasing the pump displacement as the amount increases, and high speed / small displacement control for outputting a control signal for decreasing the pump displacement as the engine speed increases Signal generating means, and second selecting means for selecting a control signal having a larger pump capacity among the control signals output by the high-speed / small capacity control signal generating means and the small operation / small capacity control signal generating means,
A controller having a third selecting means for selecting a control signal having a smaller pump capacity from among the control signals selected by the first selecting means and the second selecting means and outputting the selected control signal to the proportional electromagnetic control valve. Features.

According to the seventh aspect of the invention, the third aspect of the invention is configured electrically using a controller. The operation and effects are the same as those of the third aspect of the invention, and the cost is reduced by simplifying the configuration which is a characteristic of the electrical type. Reduction can be achieved.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described below in detail with reference to FIGS.

Referring to FIG. 1, a first embodiment of the present invention will be described. In FIG. 17 showing a second prior art diagram, in FIG. 17, a low-speed / small-capacity pressure reducing valve 8 (low-speed / small-capacity control signal generating means)
A high-load / small-capacity pressure-reducing valve 9 (high-load / small-capacity control signal generating means) shown in FIG. 14 showing the first prior art is interposed between a pump and a pump capacity control valve 5 (pump capacity control means). Other than that, the configuration is the same as that of the second related art.

According to the structure of FIG. 1, the operation is as follows.
The pilot pressures pi (control signals) output from the high-load / small-capacity pressure reducing valve 8 and the low-speed / small-capacity pressure reducing valve 9 are generated because the respective pressure reducing valves 8 and 9 are connected in series (first selection means). , The lower pilot pressure pi (the pump displacement V is large) is selected and acts on the pump displacement control valve 5 (pump displacement control means). For this reason, only the pump discharge amount Q larger than the pump discharge amount Q shown by the bold line in FIG. 19 described in the second prior art is selected from the pump discharge amount Q shown in FIG. 16 described in the first prior art. You. That is, in FIG. 2, when the horizontal axis indicates the engine speed N and the vertical axis indicates the pump discharge amount Q, the pump discharge amount Q at the load pressure Pi (see FIG. 15) is equal to the engine discharge speed Ni. Up to Qi, the curve changes on the line of Q = Vi · N (see FIG. 16), and when the engine speed N exceeds Ni, the curve changes on the thick line (see FIG. 19). As described above, the portion of the pump discharge amount Q corresponding to the engine speed N changes in the portion indicated by the solid line according to the load pressure P and the engine speed N.

Therefore, in the low engine speed range, the working machine is operated at a light load (low load pressure) such as an increase in the bucket empty load so that the pump discharge amount increases from Q1 to Q2 according to the load pressure P at the engine speed N1. Speed is ensured. In addition, since the pump discharge amount Q is ensured, even in the directional control valves 19 and 20 having the center bypass bleed-off, the starting pressure rises faster and the dead zone to the work machine starting point decreases. Further, when the load pressure P is low, the pump discharge amount Q changes uniformly over Q = Vmax · N with respect to the engine speed N. Therefore, as shown in the second prior art shown in FIG. Compared to the case where the pump discharge amount Q changes on the bold line regardless of the pressure P, a sharp change in the working machine speed with respect to the engine speed N is prevented, and the operability is improved.

A second embodiment of the present invention will be described with reference to FIG. In FIG. 22, which shows a third conventional technique, a throttle 6 is interposed between a fixed displacement pump 3 and a pilot relief valve 7, and a small operation / small volume reducing valve 11 (small operation / small volume control signal generating means) is provided. A high-speed, small-capacity pressure-reducing valve 10 (high-speed, small-capacity control signal generating means) controlled by the differential pressure across the throttle 6 and having the characteristics shown in FIG. Is the same as that of the third prior art.

First, the high-speed, small-capacity pressure reducing valve 10 shown in FIG.
Will be described. The horizontal axis represents the engine speed N, and the vertical axis represents the pilot pressure pi output from the high-speed / small-capacity pressure reducing valve 10 and the pump displacement V of the working machine pump 2. The pilot pressure pi becomes an increasing function of the engine speed N. The minimum value Vmin and the maximum value Vmax of the pump displacement V
Is mechanically set by a stopper (not shown), the engine speed N1 or less and the engine speed N1
Above 2, even if the pilot pressure pi changes, the minimum value Vmi
n and the maximum value Vmax are constant, and the engine speed N1
And N2, the pump capacity V depends on the pilot pressure pi.
Decreases substantially linearly from Vmax to Vmin (indicated by V = gN + h for simplicity). Therefore, the pump discharge amount Q (liter / m) with respect to the engine speed N
In FIG. 5, the horizontal axis indicates the engine speed N, and the vertical axis indicates the pump discharge amount Q of the work machine pump 2. As shown by the thick line, the proportional constant is Vmax up to the engine speed N1 or less.
(Q = Vmax ・ N), and when the engine speed exceeds N2, a straight line (Q = Vmi
n · N). Further, in the case of the engine speed N1 to N2, the pump displacement Vi at the time of the engine speed Ni in FIG.
= GNi + h, the pump discharge amount Qi = Vi · Ni = (gNi + h) when the engine speed is Ni in FIG.
· Ni = a ^{(gNi 2 + h · Ni)} . Generally, as shown by a thick line n, a quadratic curve (indicated by a straight line n for simplicity) where Q = (gN ² + hN) is obtained.

According to the configuration shown in FIG. 3, the operation is as follows.
The pilot pressures pi (control signals) output from the high-speed / small-capacity pressure reducing valve 10 and the small-operation / small-capacity pressure reducing valve 11 are generated because the respective pressure reducing valves 10 and 11 are connected in series (second selecting means). , The lower pilot pressure pi (pump capacity V is large) is selected and acts on the pump capacity control valve 5 (pump capacity control means). For this reason, only the pump discharge amount Q larger than the pump discharge amount Q shown by the thick line in FIG. 5 is selected from the pump discharge amount Q shown in FIG. 24 described in the third related art. That is, in FIG. 6, when the horizontal axis indicates the engine speed N and the vertical axis indicates the pump discharge amount Q of the work machine pump 2, the pump discharge amount Q when the lever operation amount is Si (see FIG. 23) is Up to Qi at the time of the engine speed Ni, the curve changes on the bold line (see FIG. 24), and when the engine speed exceeds Ni, the curve changes on the line of Q = Vi · N. As described above, the pump discharge amount Q with respect to the engine speed N changes according to the portion indicated by the solid line, the lever operation amount S and the engine speed N.

Accordingly, in FIG. 7, when the engine speed N is plotted on the horizontal axis and the engine torque T is plotted on the vertical axis, the engine speed N at high engine speed higher than the maximum torque point at fine operation and high load is obtained. From the state in which the hydraulic consumption torque p is reduced with the increase, the operation amounts of the work implement levers 15 and 16 are increased to increase the hydraulic consumption torque (pump capacity V) from p to q.
, The engine speed N matching the absorption torque a of the torque converter decreases. Therefore, when excavation work is performed in a high-speed region, as shown in FIG. 20, the work equipment load (bucket lifting force) changes from Fv1 to Fv2.
When it rises, the traveling traction decreases from Fh1 to Fh2, and the direction of these resultant forces changes from F1 to F2,
Since it is controlled substantially in the direction of the angle of repose of the sand pit, the balance of the scooping work of the earth and sand is improved.

In FIG. 8, when the horizontal axis indicates the lever operation amount S and the vertical axis indicates the pump discharge amount Q, the pump discharge amount Q is lower than the working machine lever when the engine speed is N1 or less in FIG. Is a constant discharge amount determined by the engine speed N regardless of the operation amount S. The pump discharge amount Q in the middle and high speeds of the engine exceeding the engine speed N1 is increased when the operation amount of the work implement lever becomes larger than the thick line in FIG. The fixed discharge amount is determined by the engine speed N regardless of the amount S. As described above, the lower the engine speed, the wider the area of the constant discharge amount Q determined by the engine speed N regardless of the operation amount S of the work implement lever.

A third embodiment of the present invention will be described with reference to FIG. In FIG. 1 showing the first embodiment, a low-speed / small-capacity pressure-reducing valve 8 and a high-load / small-capacity pressure-reducing valve 9, connected to a series,
In FIG. 3 showing the second embodiment, a high-speed / small-capacity pressure reducing valve 10 and a small-operation / small-capacity pressure reducing valve 11 connected in series are connected in parallel, and the larger one of the pilot pressures (pump Shuttle valve 22)
The configuration is the same as that of the first embodiment or the second embodiment, except that it is selected by the (third selecting means) and acts on the pump displacement control valve 5.

According to the configuration shown in FIG. 9, the operation is as follows.
The pilot pressure from the low speed / small capacity pressure reducing valve 8 and the high load / small capacity pressure reducing valve 9 of the first embodiment, and the high speed
The larger of the pilot pressure from the small capacity pressure reducing valve 10 and the small operation / small capacity pressure reducing valve 11 (the pump capacity V is small)
Is selected by the shuttle valve 22, and the pump displacement control valve 5 is selected.
To act on. Therefore, in FIG. 10 in which FIG. 2 and FIG. 6 are superimposed, as indicated by hatching, the smaller one of the pump discharge amount Q shown in FIG. 2 and the pump discharge amount Q shown in FIG. Selected. Therefore, the effects of the first and second embodiments can be obtained with a simple device. FIG.
The pump minimum capacity (pump discharge amount Qm) at the engine middle speed (near Nm) is set to be maximum, and the engine torque T is set by substantially matching the engine speed N at which the maximum torque of the engine torque rise occurs. Can be used effectively.

A fourth embodiment of the present invention will be described with reference to FIGS. Portions common to FIGS. 1 to 3 are denoted by the same reference numerals and description thereof is omitted. A proportional electromagnetic force, which is reduced by a signal from the controller 30 to reduce the original pressure, which is controlled by the pilot relief valve 7 at the rear of the throttle 6 installed in the discharge pipe of the pilot pump 3, and acts on the pump displacement control means 5 Type control valve 23, engine rotation sensor 24, hydraulic pressure sensor 25 for detecting the discharge oil pressure of the work equipment pump, operation amount detection sensors 26 and 27 for pilot pumps 15 and 16,
A controller 30 is provided for inputting the detection signal of 27 and outputting a control signal of the proportional electromagnetic control valve 23.

As shown in FIG. 12, as the engine speed N decreases, the controller 30 outputs a low speed / small displacement control signal generating means 31 for outputting a control signal for reducing the pump displacement V, and the work machine load P The pump volume V
Of the high-load / small-capacity control signal generating means 32 for outputting a control signal for reducing the load, and the low-speed / small-capacity control signal generating means 31 and the high-load / small-capacity control signal generating means 32, A first selection means 33 for selecting a control signal having a larger pump capacity V is provided.

Further, as the operation amount S of the work implement lever selected by the operation amount selection means 38 for selecting the larger operation amount of the operation amount detection sensors 26 and 27 of the work implement lever increases, the pump displacement V increases. A small-operation / small-capacity control signal generating means 34 for outputting a control signal to reduce the pump displacement as the engine speed increases; and a high-speed / small-capacity control signal generating means 35 for outputting a control signal for reducing the pump displacement as the engine speed increases. A second selection means 36 is provided for selecting a control signal having a larger pump capacity among the control signals output by the capacity control signal generation means 35 and the small operation / small capacity control signal generation means 34.

Further, of the control signals selected by the first selection means 33 and the second selection means 36, a control signal having a smaller pump displacement V is selected and output to the proportional electromagnetic control valve 23. Means 37 are provided. Further, a control pattern switch 38 for selecting each control signal of the first to third selection means 33, 36, 37 and outputting the selected control signal to the proportional electromagnetic control valve 23 is provided.

According to the configuration of FIGS. 11 and 12, the operation is as follows. When the detection signals of the sensors 24 to 27 are input to the controller 30, the controller 30
Each control signal output from the .about.3 selecting means 33, 36, 37 is calculated. Further, when a command of the control pattern switch 38 is input to the controller 30, the control signals of the first to third selecting means 33, 36, and 37 are selected and output to the proportional electromagnetic control valve 23. The same control as in the third embodiment can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an engine speed N and a pump discharge amount Q in the first embodiment shown in FIG.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing characteristics of a high-speed small-capacity pressure reducing valve.

FIG. 5 shows the engine speed N and the pump discharge amount Q according to FIG.
FIG.

FIG. 6 is a diagram showing a relationship between an engine speed N and a pump discharge amount Q in the second embodiment shown in FIG. 3;

FIG. 7 is a diagram showing a relationship between a lever operation amount S and a hydraulic consumption torque in the second embodiment shown in FIG. 3;

FIG. 8 is a diagram showing a relationship between a lever operation amount S and a pump discharge amount Q in the second embodiment shown in FIG.

FIG. 9 is a diagram showing a third embodiment of the present invention.

FIG. 10 is a diagram showing a relationship between an engine speed N and a pump discharge amount Q according to the third embodiment shown in FIG. 9;

FIG. 11 is a diagram showing a fourth embodiment of the present invention.

FIG. 12 is a diagram showing details of a controller 30 in FIG. 11;

FIG. 13 is a diagram showing engine torque characteristics in the first and second prior arts.

FIG. 14 is a diagram showing a first conventional technique.

FIG. 15 is a graph showing characteristics of a high-load, small-capacity pressure reducing valve.

FIG. 16 is a diagram showing a relationship between an engine speed N of a high-load small-capacity pressure reducing valve and a pump discharge amount Q;

FIG. 17 is a diagram showing a second conventional technique.

FIG. 18 is a diagram showing characteristics of a low-speed / small-capacity pressure reducing valve.

FIG. 19 is a diagram showing a relationship between an engine speed N of a low-speed / small-capacity pressure reducing valve and a pump discharge amount Q.

FIG. 20 is a diagram showing a relationship between a working machine driving force FV and a vehicle traction force FH.

FIG. 21 is a diagram showing a relationship between a lever operation amount and hydraulic consumption torque according to a third conventional technique.

FIG. 22 is a diagram showing a third conventional technique.

FIG. 23 is a view showing characteristics of a small operation / small capacity pressure reducing valve.

FIG. 24 is a diagram showing a relationship between an engine speed N of a small operation / small capacity pressure reducing valve and a pump discharge amount Q.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Engine 2 Work machine pump 3 Fixed displacement pump 4 Servo cylinder 5 Pump displacement control valve 6 Throttle (engine rotation detecting means) 7 Pilot relief valve 8 Low speed / small capacity pressure reducing valve (Low speed / small capacity control signal generating means) 9 High Load / Small capacity pressure reducing valve (High load / Small capacity control signal generating means) 10 High speed / Small capacity pressure reducing valve (High speed / Small capacity control signal generating means) 11 Small operation / Small capacity pressure reducing valve (Small operation / Small capacity control signal) Generating means) 13 Discharge pipeline (work equipment load detecting means) 21 Shuttle valve group (operating amount detecting means) 22 Shuttle valve (third selecting means) 23 Proportional electromagnetic control valve 24 Engine rotation sensor (Engine rotation detecting means) 25 Oil pressure sensor (work equipment load detecting means) 26, 27 Operation amount detecting sensor 30 Controller 31 Low speed / small capacity control signal generating means 32 High load Small capacity control signal generation means 12, 33 First selection means 34 Small operation / small capacity control signal generation means 35 High speed / small capacity control signal generation means 15, 36 Second selection means 37 Third selection means 38 Operation amount selection means ( Operation amount detection means) 39 Control pattern switch

Claims (7)

[Claims] A work machine pump (2) driven by an engine (1), and pump displacement control means (4, 5) for controlling a pump displacement which is a discharge amount per rotation of the work machine pump (2).
And engine rotation detecting means for detecting the engine speed
(6, 24) and a work vehicle pump displacement control having a low speed / small displacement control signal generating means (8, 32) for outputting a control signal for reducing the pump displacement as the engine speed decreases. In the device, a work implement load detecting means (13, 25) for detecting a work implement load, and a high load / small capacity control signal generating means (9) for outputting a control signal for reducing the pump capacity as the work implement load increases. , 31) and means for generating high-load, small-capacity control signals
(9, 31) and the low-speed / small-capacity control signal generating means (8, 32) output a control signal having a larger pump capacity by selecting a control signal having a larger pump capacity. Output to the first
A displacement control device for a working machine pump for a work vehicle, comprising a selection means (12, 33). 2. A work machine pump (2) driven by an engine (1), and pump displacement control means (4, 5) for controlling a pump displacement which is a discharge amount per rotation of the work machine pump (2).
Operation amount detecting means (21, 38) for detecting the operation amount of the work implement lever (15a, 16a); and a control signal for increasing the pump displacement as the operation amount of the work implement lever (15a, 16a) increases. A small operation / small displacement control signal generating means (11, 34) for outputting a work vehicle pump having a small capacity and a small displacement control signal generating means (11, 34).
And a high-speed / small displacement control signal generating means for outputting a control signal for reducing the pump displacement as the engine speed increases
(10,35) and the control signal output by the high-speed / small displacement control signal generation means (10,35) and the small operation / small displacement control signal generation means (11,34) And a second selection means (15, 36) for selecting the control signal and outputting the selected signal to the pump capacity control means (4, 5). 3. The method according to claim 1, wherein
A control signal selected by the selection means (12, 33);
(15, 36) includes third selection means (22, 37) for selecting a control signal having a smaller pump capacity from among the control signals selected by (15, 36) and outputting the selected control signal to the pump capacity control means (4, 5). A displacement control device for a working machine pump for a work vehicle. 4. The engine rotation detecting means (6) according to claim 1, wherein the engine rotation detecting means (6) is a throttle installed in a discharge pipe of a fixed displacement pump (3) driven by the engine (1). The control signal generating means (8) is a low-speed / small-capacity pressure reducing valve that reduces the pilot source pressure controlled by the pilot relief valve (7) connected downstream of the throttle to a constant pressure at a low engine speed and a high pressure at a low engine speed. The work implement load detecting means (13) is a discharge line of the work implement pump (2), and the high load / small capacity control signal generating means (9) detects the output pressure of the low speed / small capacity pressure reducing valve. A high-load, small-capacity pressure-reducing valve that reduces pressure with a high load on the work machine and low with a low load on the work machine. (12) A displacement control device for a working machine pump for a working vehicle, characterized by comprising (12). 5. The engine rotation detecting means according to claim 2, wherein the engine rotation detecting means is a throttle installed in a discharge line of a fixed displacement pump driven by the engine. The small-capacity control signal generating means (10) reduces the pilot source pressure controlled to a constant pressure by the pilot relief valve (7) connected downstream of the throttle at a high engine speed and at a low engine speed to reduce the pilot pressure. The operation amount detection means (21, 38) is a shuttle valve group that selects the maximum pilot pressure, which reduces the pilot source pressure according to the operation amount of the pilot pressure control valves (15, 16). The small-operation / small-capacity control signal generating means (9) increases the output pressure of the high-speed / small-capacity pressure reducing valve with a small operation of the work equipment levers (15a, 16a).
(15a, 16a) is a small-operation, small-capacity pressure-reducing valve that reduces pressure by multiple operations at a low rate. A displacement control device for a working machine pump for a work vehicle, comprising: 6. The method according to claim 3, wherein the third selecting means (22, 3
7) A displacement control device for a working machine pump for a working vehicle, wherein the displacement valve is a shuttle valve. 7. The pilot pump according to claim 3,
(3), a pilot relief valve (7) for controlling the discharge pressure of the pilot pump (3) to a constant pressure, and a pilot pump
And a proportional solenoid control valve (23) for reducing the discharge pressure of (3) and outputting it to the pump displacement control means (4, 5) .The engine rotation detection means (6, 24) is a rotation sensor. The machine load detecting means (13, 25) is a hydraulic pressure sensor for detecting the discharge hydraulic pressure of the work machine pump (2), and the operation amount detecting means (21, 38) is a work amount lever operation amount detection sensor (26, 27). Is the operation amount selection means for selecting the maximum value of the sensors (24, 25, 26, 2
7) Input the detection signal of and output a control signal to reduce the pump capacity as the engine speed decreases.
A small-capacity control signal generating means (32) and a high-load
Among the control signals output by the small capacity control signal generating means (31), the low speed / small capacity control signal generating means (32) and the high load / small capacity control signal generating means (31), First selecting means (33) for selecting the control signal of
Small operation / small displacement control signal generating means that outputs a control signal to increase the pump displacement as the manipulated variable of (15, 16) increases
(34), a high-speed and small-capacity control signal generating means (35) for outputting a control signal for reducing the pump displacement as the engine speed increases, and a high-speed and small-capacity control signal generating means (35) with less operation A second selecting means (36) for selecting a control signal having a larger pump capacity among the control signals output from the small capacity control signal generating means (34); a first selecting means (33); Selection means
Out of the control signals selected by (36), a controller (30) having third selection means (37) for selecting a control signal having a smaller pump capacity and outputting the selected control signal to the proportional electromagnetic control valve (23). A displacement control device for a working machine pump for a working vehicle, comprising: