JPS62156439A - Oil-pressure controller of oil-pressure shovel - Google Patents

Abstract

PURPOSE:To maximize the absorption horsepower and output of a pump by providing a setter by which the revolving number of a prime mover is regulated to a volume suitable for heavy loads in response to detection signals and the capacity of an oil- pressure pump is controlled to a volume smaller than a preset maximum push-off capacity. CONSTITUTION:The oil pressure controller of an oil-pressure shovel is provided with a variable capacity type oil-pressure pump 13 to be driven by a prime mover, an actuator 19 to be driven by the oil pressure from the pump, and a revolving number controller 25 to control the revolving number of the prime mover. Also, a revolving number sensor 31 to send out detection signals when revolving number suitable for light load of the prime mover is exceeded is provided, and a maximum push-off capacity setter 21 to control an oil-pressure pump 13 to a push-off capacity smaller than a preset max. push-off capacity in response to the detection signals is also provided. Furthermore, a revolving number controller 25 is provided to switch the revolving number of the prime mover to a value suitable for a load heavier than revolving number suitable for light load in response to detection signals. The revolving number of the prime move can thus be controlled without changing the speeds of operations during traveling.

Description

[Detailed description of the invention] A. Industrial application field The present invention relates to a hydraulic control device for a hydraulic excavator.

B. Conventional technology The conventional technology will be explained using a wheeled hydraulic excavator as an example.

As shown in FIG. 7, the wheeled hydraulic excavator consists of a lower traveling body 2 having running wheels 1, and an upper rotating body 3 connected to the lower traveling body 2 via a swing ring. The revolving body 3 includes a boom 7 and an arm 8, which are driven by hydraulic cylinders 4 to 6, respectively. A digging attachment consisting of a packet 9 or the like is provided.

Unlike crawler-type hydraulic excavators, this type of wheel-type hydraulic excavator is approved for use on general roads, and is therefore required to run faster than crawler-type hydraulic excavators; however, according to current domestic regulations, the maximum speed is 35
It is regulated to less than 8km. For this reason, it is an absolute requirement for wheeled hydraulic excavators to be able to travel at speeds of up to 35 km.

Against this background, the running drive devices for wheeled hydraulic excavators have traditionally been the so-called mechanical type, which mechanically decelerates the output of the engine mounted on the upper revolving structure to drive the jI axis, or There is a hydraulic type in which a hydraulic pump is driven by an engine, which turns a hydraulic motor to drive an axle, but both have the problems described below.

C1 Problems that the invention seeks to solve Mechanical travel drive devices must mechanically transmit the output of the engine mounted on the upper rotating body to the axle of the lower rotating body, and therefore have a large number of components. It has poor assembly properties and is very expensive.

Further, the conventional hydraulic travel drive device has the following problems.

As mentioned earlier, wheeled hydraulic excavators are allowed to drive on general roads, not just within specific work sites, but general roads include both flat roads and slopes.
Maximum legal speed of 35km under various road conditions
It is preferable to be able to travel at /h.

Therefore, when pitching at a certain required slope, 35 km/h
If we use an engine that can reach speeds of In a wheeled hydraulic excavator, one engine is generally used for both excavation and travel, but the engine horsepower required for excavation work may be smaller than the engine horsepower required for travel. For this reason, setting the engine to high horsepower with emphasis on running performance when climbing is wasteful in terms of fuel consumption, noise, cost, etc. from the perspective of excavation work, and on the other hand,
If the engine is set to a lower horsepower than the former with emphasis on fuel efficiency, noise, and cost during excavation, sufficient running performance will not be obtained when climbing. This will result in poor matching with driving.

To this end, various approaches have been taken in the past, and one representative approach is to satisfy the legally mandated speed of 35 ko/h only when driving on flat roads.

In this case, from the specifications of the traveling hydraulic motor and transmission used, if the required flow rate when traveling on the qi river at 35 km/h is defined as Ql and the required pressure as Pl, then, for example, the 8th
As shown in Figure (a), the required horsepower PS2° of the engine is determined, and from this, the maximum engine speed Nl and the displacement volume q1 of the hydraulic pump are determined, and the engine speed - pump discharge state curve (N-9 curve) is determined. ) is as shown in FIG. 9, for example.

If we consider running uphill in a hydraulic travel drive system having the N-9 curve shown in Figure 9, Figure 8(a)
As shown in Figure 2, when pitching, the pump discharge pressure increases to P2 and the pump tilt angle decreases, so the pump discharge ■
decreases to Q2, and therefore its speed is considerably less than 35km/h (35km/hX Q 2 / Q l )
As a result, satisfactory driving performance cannot be obtained.

Therefore, in determining the specifications of the engine and hydraulic equipment, it is conceivable to set the specifications so that a speed of 35 km/h can be obtained at a preset slope. With this setting, it goes without saying that the speed will be 35 km/h even when driving on a flat road.
The speed of h is reached.

Therefore, as mentioned above, due to the specifications of the hydraulic motor and transmission used, we decided to
The required flow rate when traveling at h is Ql, and the required pressure is P2(
> PL), the required horsepower PS2 of the engine is determined, for example as shown in FIG.
For example, the engine speed-pump discharge amount diagram (N-Q diagram) is as shown in FIG. Assume that the performance of is determined as shown in FIG. The rotation speed-horsepower curve in Fig. 11 (
As can be seen from the N-PS curve, the pump absorption horsepower required to travel at a speed of 35 km on a sloped road is PS2.
If so, that horsepower is obtained when the engine speed is N2. Then, the fuel consumption rate at that time (
g/PS h ) is the rotation speed-fuel consumption rate curve (N-g
It can be seen from the curve) that it is g2. However, the absorption horsepower of the pump when traveling at 35 km/h on a flat road with such a hydraulic traveling drive device is expressed as PS2'(<PS2).
Then, when driving on a flat road with the engine at full throttle, the engine speed at that time is N2° (>N2)
It can be seen that the fuel consumption rate is g2'(>g2). That is, with such settings of the engine and hydraulic system, the engine must be used in a region where its fuel consumption rate is poor in order to travel at 35 km/h on the -[i road, which is not preferable. In addition, in order to use the engine in a range with good fuel consumption, operating the throttle lever to lower the engine speed will reduce the pump discharge and allow you to reach the specified speed (35 km/h). I can't do it.

In addition, in a wheeled hydraulic excavator equipped with a traveling hydraulic drive device, as described above, a single hydraulic pump and an engine mounted on the upper revolving structure are used to drive the excavation actuator and the traveling hydraulic motor. However, the required absorption horsepower PS2 of the hydraulic pump during uphill travel is considerably larger than the required absorption horsepower PS3 of the hydraulic pump during excavation.

Therefore, in an engine having the characteristics shown in Fig. 11, when excavation work is performed with the throttle lever position at the highest engine opening k number N2, if the required absorption horsepower of the hydraulic pump is PS3 (<PS2), then the engine rotational speed is is N3
and the fuel consumption rate becomes g3 (>, g2). If you operate the throttle lever to lower the engine speed, the pump discharge amount will decrease and the working speed will slow down.

The problems of the prior art have been explained above using a wheeled hydraulic excavator as an example, but the relationship between heavy load work and light load work in a crawler type hydraulic excavator is also the same. In other words, setting the engine to high horsepower with emphasis on heavy-load work is wasteful in terms of fuel efficiency, noise, cost, etc. from the perspective of light-load work; If the engine is set to low horsepower, it will not be possible to obtain sufficient digging performance during heavy load work. If the engine is set to high horsepower and the engine speed is lowered during light load work, the pump discharge amount will decrease, making it impossible to obtain the desired work speed.

The purpose of the present invention is to solve these conventional problems and to reduce the rotational speed of the prime mover without reducing the pump discharge amount during light load operations even if the prime mover is set to high horsepower for heavy load operations. The object of the present invention is to provide a hydraulic control device for a hydraulic excavator that can

Means for Solving Problem D1 First Invention C: When the rotational speed of the prime mover controlled by the rotational speed control means constituted by an engine control lever etc. exceeds the optimum rotational speed for a light load of the prime mover. a rotation speed detection means for outputting a detection signal to the detection signal; a rotation speed switching means for switching the rotation speed of the prime mover to a rotation speed optimum for a heavy load which is higher than the rotation speed optimum for a light load in response to the detection signal; In response to the signal, the hydraulic pump is controlled to a maximum displacement that is smaller than a preset maximum displacement within a range where a predetermined discharge amount can be obtained. .

The second invention is a rotation speed detection device that outputs a detection signal when the rotation speed of the prime mover, which is controlled by a rotation speed control means constituted by an engine control lever, etc., exceeds the optimum rotation speed for a light load of the prime mover. means and operates to select between power mode and economy mode;
A mode selection means that outputs a power mode signal when the power mode is selected and an economy mode signal when the economy mode is selected; and a mode selection means that increases the rotation speed of the prime mover to a higher rotation speed than the optimum rotation speed for a light load in response to the detection signal. The rotation speed switching means switches to the optimum rotation speed, and in response to the occurrence of the detection signal and the power mode signal, the hydraulic pump is operated so that the preset maximum displacement is greater than the volume within the range where a predetermined discharge amount can be obtained. The small maximum displacement is provided with a maximum displacement volume setting means for controlling the volume.

80 Effect In the first invention, the pump rotation speed is increased by operating the engine control lever etc. in the driver's seat, and only when the rotation speed of the prime mover exceeds the optimum rotation speed for a light load, the maximum pump displacement is set by the volume setting means. The displacement becomes smaller than the previously set maximum displacement, and the rotation speed switching means changes B: [Motor rotation speed is larger than the optimum rotation speed for light loads. controlled by.

In the second invention, when the mode selection stage is in the power mode and the prime mover rotational speed exceeds the optimum rotational speed for a light load, the same control as in the first invention is performed.

F. Embodiment (first invention) FIG. 1 shows an embodiment of the present invention, in which a variable displacement hydraulic pump 1 driven by an engine 11 constituting a prime mover is shown in FIG.
The discharge boat No. 3 is connected via the control valve 15 to
It is connected to a travel hydraulic motor 17 and an excavation actuator 19 including excavation cylinders (hydraulic cylinders 4 to 6 in FIG. 7) and a swing motor. control valve 15
is controlled by a travel control lever (not shown) and an excavation control lever (not shown).

The variable displacement hydraulic pump 13 has a pump regulator (not shown) that controls its discharge needle by circuit pressure (for example, as shown in the P-Q diagram in FIG. 5). For maximum displacement, a maximum displacement angle control device 21 constituting a volume setting stage is provided, and it is driven and controlled by a hydraulic cylinder 21a for maximum displacement angle setting, so that the maximum displacement per revolution of the pump is determined by the volume. can be controlled in two stages. This hydraulic cylinder 21a is connected to a pressure source 24 and a tank 26 via a solenoid valve 23.

Further, an engine rotation speed control device 25 that constitutes rotation speed switching means is provided in conjunction with a governor (not shown) of the engine 11, and thereby the rotation speed of the engine 11 is controlled as described below. Referring to FIGS. 2(a) to 2(c), the rotation speed control device 25 includes a lever 2 pivotally supported at a predetermined portion.
5a, and a throttle lever 12 connected to a governor is connected to the intermediate point of the lever 25a. death/
A spring 25b is hooked to the tip of <-25a, and the spring 25
The other end of b is hooked to one end of a lever 25c that is pivotally supported at a predetermined location. The other end of the /<-25C is connected to the engine control lever/<-25e in the driver's seat, for example, by a push-pull cable 14. This engine control lever 25e constitutes a rotation speed control means, and can continuously control the engine rotation from idle to NE in a region below the engine rotation speed NE.

Here, the engine speed Nt= is determined so that 35 km/h can be obtained when driving on a road with the minimum horsepower required in accordance with the tilting angle of the pump, and is the optimum speed for a light engine load. It is.

Furthermore, this engine speed control device 25 has a lever 25a.
The actuator 25d controls the rotation angle of the actuator 25d.
5d, it is possible to control the lever 25a to the maximum rotation angle and rotate the engine at the maximum rotational speed Np as shown in FIG. 2(C).

Here, the maximum engine speed Np is determined so that 35 + s/h can be obtained when running uphill on a desired slope with the minimum horsepower required in accordance with the tilting angle of the pump, and the engine is under heavy load. This is the optimum rotation speed.

In addition, Fig. 2 (a) shows the engine idling state, Fig. 2 (
b) A state in which the 4i engine rotational speed is controlled to a predetermined value NE by the engine control lever 25e, Fig. 2 (C
) indicates full throttle condition.

In this embodiment, when the engine control lever 25e is fully pulled, the engine speed exceeds NE.
', so that even if the actuator 25d is driven, the engine control lever 25e does not move. Further, as shown in FIG. 1, the actuator 25d is connected to a pressure source 24 and a tank 26 via a solenoid valve 27.

Referring again to FIG. 1, reference numeral 29 is a controller composed of, for example, a microcomputer, and an engine rotation speed sensor constituting rotation speed detection means provided around the output shaft of the engine is connected to the human power port of the controller. 31 is connected. Furthermore, an output port of the controller 29 is connected to a maximum tilt angle control solenoid valve 23 and an engine rotation speed control solenoid valve 27 . These solenoid valves 23 and 27 are controlled according to the program shown in FIG. 3, which will be described later.
When the engine speed is below the predetermined value NE, both solenoid valves 23
．． 27 is demagnetized (off) and the engine speed is set to a predetermined value N.
When E is exceeded, both electromagnetic valves 23 and 27 are energized (turned on).

Next, the programs stored in advance in the ROM of the controller 29 will be explained with reference to FIG.

First, in step St, the engine speed No. is read based on the signal from the engine speed sensor 31. Proceeding to step S2, the read engine rotation speed NO.
A predetermined value N of the engine speed stored in advance in the ROM
Distinguish the size from EE. If the signal from the sensor 31 indicating the current engine speed No. indicates that it exceeds the optimum speed Na for a light load on the engine, the process advances to step S3, indicating that it is below NE. If so, proceed to step S4. In step S3, the solenoid valve 23
．． 27 are both turned on, and in step S4, the solenoid valves 23.2 and 27 are turned on.
7 are both turned off.

The operation of this embodiment configured in this way will be explained.

(1) When the engine speed is below the optimum speed NE for light loads When the engine speed is below Nrs, the solenoid valve 23.
27 are both turned off, and both the pump maximum tilt angle control actuator 21a and the engine rotation speed control actuator 25d are not energized. Therefore, the maximum pump displacement determined by the pump maximum tilt angle is set to its maximum value qE, and the engine speed is determined by the operation of the engine control lever 25e on the driver's seat, fl
becomes Ill'I corresponding to . In this case, the N-9 curve is shown by the solid line in Figure 4, and when the engine speed is Na, the P-9 curve is shown by the dashed line E in Figure 5.
It will be shown as follows. In addition, P-Q in a conventional hydraulic pump that does not perform maximum tilt angle switching control as in the present invention.
An example of the diagram is shown in FIG.

In the conventional example, when the engine speed is decreased from No to No', the pump discharge amount also decreases from QO to QO°, making it impossible to improve fuel efficiency while maintaining the working speed.

(2) When the engine speed exceeds the optimum speed NE for light loads Engine control RA/< -25e When the engine speed reaches the speed Na' exceeding Nr= by pulling it all the way, the solenoid valve 23. 27 are both turned on, and actuators 21a and 25d are both energized. Therefore, the maximum displacement determined by the maximum pump tilt angle is the volume (LP
(<qE), and as shown in Figure 2 (c), the engine speed is set to the optimum speed N for heavy loads.
p, that is, the maximum rotation speed of the installed engine.

In this case, the N-9 curve is indicated by point P in FIG.
The curve becomes as shown by the solid line P in FIG.

Here, the maximum displacement is the volume (IE l (In determining IP and engine speed Ni, Np, qEX
NEE=qPXNP However, qEE>qP and NIIE<NP.

According to this embodiment, for example, when the wheeled hydraulic excavator starts climbing and the throttle lever is opened and the engine speed exceeds Ni, the actuator 25d
As a result, the engine revs up and its rotational speed becomes Np, and the pump maximum tilting angle becomes smaller than the maximum tilting angle when the rotational speed NU or less, and the maximum displacement becomes equivalent to qp. As a result, the engine output horsepower and the pump absorption horsepower reach their maximum values, and the wheeled hydraulic excavator can climb while maintaining a desired speed, for example, 35 ka/h. On the other hand, when the engine speed is below NE, the maximum displacement determined by the maximum pump tilt angle is qlE.
As a result, it is suitable for light load work such as driving on flat roads and light excavation.

The pump absorbs horsepower and the engine can be operated in an advantageous range of fuel consumption.

To explain in detail with the engine performance curve in Fig. 11, for example, if the required horsepower when driving on a flat road is P52°, that horsepower can be obtained with the engine rotation speed of NaO, and the required horsepower when digging is PS3. Then, the engine speed is N
That horsepower can be obtained with oO, but in this example, in the region where the engine speed is below NEE, the maximum displacement of the pump is made larger than in the high horsepower region where the engine speed exceeds NE. 1. It becomes possible to work in a low fuel consumption area without sacrificing work speed (traveling speed). Furthermore, if the required horsepower when running uphill on a certain slope is PS2, the horsepower can be increased to 17 at engine speed N2, but in this example, in the region where the engine speed exceeds Ng, the engine speed increases. Since the pump maximum displacement is set to a smaller value according to the rotational speed and the pump discharge amount does not increase, the traveling speed will not exceed the legal speed even if the vehicle is driven on a flat road in this state.

As shown in Figure 4, on the wood flow side, the engine speed N
Pump maximum discharge amount QH when H and engine speed N
Since each part was determined so that the pump maximum discharge ff1Qp when p is equal, the maximum displacement determined by the pump maximum tilt angle does not change the working speed or traveling speed even if the volume changes from qa to qP. It is also favorable in terms of driving feeling.

In addition, in the present invention, the above-mentioned pump discharge amounts QH and Q
p may not necessarily be equal.

(Second invention) In the first invention, the engine speed is determined based on the signal from the rotation speed sensor 31, and thereby the engine speed is determined to be NEE.
When it is determined that the maximum displacement of the hydraulic pump is exceeded, the displacement of the hydraulic pump is controlled to qE + qP and the engine speed is controlled to Np at once, but the invention of 0'52 provides a mode selection switch, The same control as described above is performed based on two conditions: the engine speed and the switching position of the mode selection switch.

That is, an economy mode for light-load work and a power mode for heavy-load work are set, and one of the modes is selected by the mode selection switch 33 shown within the two-dot chain line in FIG. This mode selection switch 33 constitutes mode selection means, and outputs a power mode signal when operated to the power mode selection position P, and outputs an economy mode signal 5- when operated to the economy mode selection position E.
) is output.

Then, the pump maximum tilt angle and engine control are performed according to the processing procedure shown in FIG. 6 instead of the processing procedure shown in FIG. Only when the engine speed exceeds NE and the power mode is selected, the pump maximum displacement controls the volume from qE to qp, and the engine speed is controlled to Np to perform power mode operation. Under other conditions, the maximum displacement of the pump is controlled to qE, and the engine speed is controlled according to the operating amount of the engine control lever 25e.

According to such a configuration, by selecting the economy mode, the engine will not be operated in the power mode, that is, the engine speed is Np and the pump maximum displacement is qp, by mistake during light load work. .

Although the present invention has been described above in detail with respect to a wheeled hydraulic excavator, the present invention can also be applied to a crawler type hydraulic excavator.

Further, in the above description, the engine rotation speed was determined according to the program in the controller 29, but the determination may be made using a comparator or the like without depending on the program. Further, instead of the rotation speed sensor 31, the rotation speed detection means is constituted by a switch that is switched when the engine control lever 25e in the driver's seat or the throttle lever on the engine side moves to a position exceeding the engine rotation speed Ni. , the engine speed may be determined indirectly.

Furthermore, although the engine rotational speed is increased by the hydraulic cylinder 25d, it may be increased by an electromagnetic seven-actuator. Further, the maximum tilt angle may be controlled by an electromagnetic actuator as well. In this case, the electromagnetic actuator may be driven in accordance with the output signal of the one rotation speed sensor 31.

Effects of the G2 Invention According to the first invention, in a region where the rotational speed of the prime mover exceeds the optimal rotational speed for light loads, the maximum displacement of the hydraulic pump increases the volume, and the maximum displacement that has been set until now increases. The rotation speed of the prime mover is set to a value smaller than the volume, and the rotation speed of the prime mover is controlled to the optimum rotation speed for heavy loads, which is larger than the optimum rotation speed for light loads. The maximum displacement of the pump is set to a value larger than the volume when the pump is under heavy load.The maximum displacement of the pump is set to a value larger than the volume, so the pump absorption required for light load work can be achieved without sacrificing the working speed or travel speed. In addition to being able to run the hydraulic excavator in a state where the fuel consumption rate is most favorable by reducing the output of the prime mover to increase horsepower, this control is performed by controlling the rotational speed of the prime mover, making operation extremely easy. becomes.

According to the second invention, the above-mentioned control is performed according to whether the rotational speed of the prime mover exceeds the optimum rotational speed for light loads and whether power mode operation is selected.
In addition, if the economy mode is selected, even if the prime mover rotation speed exceeds the optimal rotation speed for light loads, the pump's maximum displacement remains unchanged, and the prime mover rotation speed remains the same. During light load work, the work can be reliably performed in the low horsepower range and at the desired work speed, and is extremely effective in terms of fuel consumption and noise.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 (
a) to (C) are front views showing an example of the engine maximum rotation speed control device shown in FIG. 1, in which FIG. 2(a) shows the throttle lever in the idle position, and FIG. 2(b) shows the throttle lever in the idle position. is engine revolution '1 (position of NI!, Fig. 2)
c) shows the case where the throttle lever is at the full throttle position, FIG. 3 is a flowchart showing an example of the solenoid valve control program in the first invention, and FIG. 4 shows the engine rotation speed N and pump discharge in this embodiment. A graph showing the relationship with the quantity Q, FIG. 5 is a diagram showing a P-Q diagram of the pump in this embodiment, and FIG. 6 is a flowchart showing an example of the program for controlling both valves in 1 in the second invention. Fig. 7 is a side view of an example of a wheeled hydraulic excavator, and Fig. 8 (a) and (b) are two of the conventional P-Q diagrams.
FIG. 9 and FIG. 1θ are graphs showing the relationship between engine rotation speed N and pump discharge amount Q in a conventional wheeled hydraulic excavator, and FIG. 11 is a diagram showing an engine performance curve. FIG. 12 is a diagram showing a P-Qm diagram for a pump of a conventional wheeled hydraulic excavator. 1: Running wheel 2: Lower traveling body 3 Knee-L section revolving body 4-9: Excavation attachment 11: Engine 13: Variable displacement hydraulic pump 15: Control valve! 7: Hydraulic motor 19: Excavation actuator 21: Maximum tilting angle control device 23. 27: Solenoid valve 25: Engine speed control device 25a, 25c Nilever 25b: Spring 25d: Hydraulic cylinder 25e: Engine control lever 29: Controller 31 : Rotation speed sensor 33: Mode selection switch Applicant: Hitachi Construction Machinery Co., Ltd. Representative Patent Attorney Fuyu Nagai Fig. 1 Fig. 2 Fig. 25b Fig. 3 Fig. 4 Fig. 2〉〉〉〉Muslim RN- Fig. 5 Takashi Schiff ° scolding tlノ2 force P Figure 6 Figure 7 Figure 8 PIP2. Meg/Gud 211 Power 189 Figure 10 I > Syn B pN → Figure 11 Month n V Ne 11 Official Book November 20, 1985 To the Commissioner of the Japan Patent Office 7C1, Indication of the case 1985 Patent Application No. 298516 2) Name of the invention Hydraulic control device for hydraulic excavator 3, Person making the amendment Relationship to the case Patent applicant (552) Hitachi Construction Machinery Co., Ltd. 4, Agent 5, Voluntary amendment with [” in the amendment order 6. Number of inventions increased by amendment O7. Subject of amendment 8. Contents of amendment -1 2. Scope of Patent No. 311 sought l) A variable displacement hydraulic pump driven by a prime mover; 4. In a hydraulic control device for a hydraulic excavator comprising an actuator driven by pressure oil discharged from a nuclear hydraulic pump and a rotation speed control means for controlling the rotation speed of the prime mover, the hydraulic control device is controlled by a support plate 5 LL I 7. I゛(motion +
11. A rotation speed detection means that outputs a detection signal when the rotation speed of the prime mover exceeds the light load once, and a rotation speed detection means that outputs a detection signal when the rotation speed of the prime mover exceeds the light load once, and a rotation speed detection means that outputs a detection signal when the rotation speed of the prime mover exceeds the light load. a rotation speed switching means for switching to a heavy load higher than the rotation speed to t=rotation speed; and in response to the detection signal, the hydraulic pump is operated at a preset maximum displacement within a range in which a predetermined discharge amount can be obtained. 1. A hydraulic control device for a hydraulic excavator, comprising a maximum displacement setting means for controlling a maximum displacement smaller than a volume to a volume. 2) In the apparatus according to claim 1, the rotation speed control means includes an engine control lever provided in a driver's seat and connected to a throttle lever of a prime mover, and the rotation speed switching means The rotation speed control means includes an actuator that is provided to drive a throttle lever, and when the rotation speed of the prime mover is less than one rotation speed under the light load, the rotation speed of the prime mover is controlled from the idle rotation speed to the light load. m rotation speed is continuously controlled, and when the prime mover rotation speed exceeds 5 to 2 rotation speeds for the light load by the rotation speed control means, the prime mover rotation speed is discontinuously controlled by the actuator up to U rotation speed for the heavy load. A hydraulic control device for a hydraulic excavator. 3) In the device according to claim 1 or 2, the maximum displacement is determined by the displacement setting means to determine the maximum displacement as the hydraulic pump discharge amount when the prime mover rotation speed is the light load and t=rotation speed. A hydraulic control device for a hydraulic excavator, characterized in that the maximum displacement is controlled so that the displacement of the hydraulic pump when the heavy load is applied and the rotation speed is to the left is approximately the same. 4) Hydraulic pressure of a hydraulic excavator including a variable displacement hydraulic pump driven by a prime mover, an actuator driven by pressure oil discharged from the hydraulic pump, and a rotation speed control means for controlling the rotation speed of the prime mover. In the control device, the 5 moves made 1 no 1' with Nao-e-sara Gochiben LE [
1f is a rotational speed detection means that outputs a detection signal when the rotational speed exceeds m during the light load of the prime mover, and a rotational speed detection means that operates to select either the power mode or the economy mode, and when the power mode is selected, the power mode is selected. mode selection means for outputting a signal and outputting an economy mode signal when an economy mode is selected; and in response to the detection signal, the rotation speed of the prime mover is changed to a heavy load higher than the light load at t=rotation speed; and a rotation speed switching means for switching the rotation speed to a rotation speed, and in response to the occurrence of the detection signal and the power mode signal, the hydraulic pump is operated so that a preset maximum displacement is smaller than the volume within a range in which a predetermined discharge amount can be obtained. 1. A hydraulic control device for a hydraulic excavator, characterized in that the maximum displacement is controlled to a volume, and the maximum displacement is a volume setting means. 5) In the apparatus according to claim 4, the rotation speed control means includes an engine control lever provided in a driver's seat and connected to a throttle lever of a prime mover, and the rotation speed switching means The rotation speed of the prime mover is controlled by the rotation speed control means to change the rotation speed of the prime mover from the idle rotation speed to the light load when the rotation speed of the prime mover is lower than or equal to the light load t=rotation speed. = rotational speed is continuously controlled until the motor rotational speed reaches the light load by the rotational speed control means.
A hydraulic control device for a hydraulic excavator, characterized in that when the number of revolutions exceeds t, the actuator discontinuously controls the heavy load up to the number of revolutions t. 6) In the device according to claim 4 or 5, the maximum displacement setting means is configured to set a hydraulic pump discharge amount when the prime mover rotation speed is 2 rotations after returning to the light load. A hydraulic control device for a hydraulic excavator, characterized in that the maximum displacement is controlled so that the displacement of the hydraulic pump and the displacement of the hydraulic pump at a rotation speed suitable for the heavy load are approximately the same.

Claims (1)

[Claims] 1) A variable displacement hydraulic pump driven by a prime mover;
A hydraulic control device for a hydraulic excavator comprising an actuator driven by pressure oil discharged from the hydraulic pump and a rotation speed control means for controlling the rotation speed of the prime mover, wherein the rotation speed is optimal for a light load of the prime mover. rotation speed detection means that outputs a detection signal when the rotation speed exceeds the rotation speed, and a rotation speed that changes the rotation speed of the prime mover to a rotation speed that is higher than the rotation speed that is optimal for the light load and is optimal for the heavy load in response to the detection signal. the hydraulic pump in response to the detection signal;
A hydraulic control device for a hydraulic excavator, comprising: a maximum displacement volume setting means for controlling a maximum displacement volume to a smaller maximum displacement volume than a preset maximum displacement volume within a range in which a predetermined discharge amount can be obtained. 2) In the apparatus according to claim 1, the rotation speed control means includes an engine control lever provided in a driver's seat and connected to a throttle lever of a prime mover, and the rotation speed switching means An actuator is provided to drive a throttle lever, and when the rotational speed of the prime mover is below the optimum rotational speed for the light load, the rotational speed control means changes the rotational speed of the prime mover from the idle rotational speed to the optimum rotational speed for the light load. Continuously controlled rotation speed up to
A hydraulic control device for a hydraulic excavator, characterized in that when the rotational speed of the prime mover exceeds the optimum rotational speed for the light load by the rotational speed control means, the actuator discontinuously controls the rotational speed to the optimum rotational speed for the heavy load. . 3) In the device according to claim 1 or 2, the maximum displacement setting means determines a hydraulic pump discharge amount when the prime mover rotation speed is an optimal rotation speed for the light load; A hydraulic control device for a hydraulic excavator, characterized in that the maximum displacement volume is controlled so that the discharge amount of the hydraulic pump at the optimum rotation speed for the heavy load is approximately the same. 4) a variable displacement hydraulic pump driven by a prime mover;
A hydraulic control device for a hydraulic excavator comprising an actuator driven by pressure oil discharged from the hydraulic pump and a rotation speed control means for controlling the rotation speed of the prime mover, wherein the rotation speed is optimal for a light load of the prime mover. A rotation speed detection means that outputs a detection signal when the rotation speed exceeds the specified speed, and operates to select either power mode or economy mode, outputs a power mode signal when power mode is selected, and outputs an economy mode signal when economy mode is selected. mode selection means for outputting the detection signal; rotation speed switching means for switching the rotation speed of the prime mover to a rotation speed optimal for a heavy load that is higher than the rotation speed optimal for the light load in response to the detection signal; and maximum displacement setting means for controlling the hydraulic pump to a maximum displacement smaller than a preset maximum displacement within a range in which a predetermined displacement can be obtained in response to the occurrence of a power mode signal. A hydraulic control device for a hydraulic excavator, characterized by comprising: 5) In the apparatus according to claim 4, the rotation speed control means includes an engine control lever provided in a driver's seat and connected to a throttle lever of a prime mover, and the rotation speed switching means An actuator is provided to drive a throttle lever, and when the rotational speed of the prime mover is below the optimum rotational speed for the light load, the rotational speed control means changes the rotational speed of the prime mover from the idle rotational speed to the optimum rotational speed for the light load. Continuously controlled rotation speed up to
A hydraulic control device for a hydraulic excavator, characterized in that when the rotational speed of the prime mover exceeds the optimum rotational speed for the light load by the rotational speed control means, the actuator discontinuously controls the rotational speed to the optimum rotational speed for the heavy load. . 6) In the device according to claim 4 or 5, the maximum displacement setting means sets a hydraulic pump discharge amount when the prime mover rotation speed is an optimal rotation speed for the light load; A hydraulic control device for a hydraulic excavator, characterized in that the maximum displacement volume is controlled so that the discharge amount of the hydraulic pump at the optimum rotation speed for the heavy load is approximately the same.