JP2003221842A - Excavator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excavator which has a revolving body arranged on a traveling portion, and has an excavating portion such as an arm, a boom, and a bucket arranged on the revolving body, wherein the excavator is improved in workability thereof in a groove lateral side abutting excavation. <P>SOLUTION: According to the excavator, two hydraulic pumps P1, P2 for driving an excavating portion and a traveling portion are made variable in capacity, and a hydraulic pump P3 for driving a hydraulic motor for rotating the revolving body 8 is also made variable in capacity. Then, the hydraulic pumps P1, P2 have a control section 58 and the hydraulic pump P3 has a control section 57, whereby the flow rates of the respective hydraulic pumps P1, P2, P3 are controlled by the pressure of the hydraulic pump P3. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic mechanism used in an excavating work machine.

[0002]

2. Description of the Related Art An excavator is composed of a traveling section, a turning section and an excavating section. The traveling unit has a crawler traveling device driven by a hydraulic motor. The swivel unit is arranged on the traveling unit and is configured to be swivelable with respect to the traveling unit by a hydraulic motor or the like. The excavation section is composed of a boom, an arm, a bucket, etc., and is arranged on the turning section. The boom, arm and bucket are driven by hydraulic cylinders. Excavator
A hydraulic pump is disposed in the hydraulic motor that turns the turning portion, and the hydraulic pump is driven by the engine together with the hydraulic pump that drives the traveling portion and the excavating portion. As such a technique, the technique disclosed in Japanese Patent Laid-Open No. 4-216725 and the technique disclosed in Japanese Patent Laid-Open No. 57-133940 are known. FIG. 23 (a) is a schematic diagram showing the configuration of three hydraulic pumps, and FIG. 23 (b) is a diagram showing the relationship between the hydraulic pressures of the first pump and the second pump and the pressure oil flow rate. In the technique shown here, as shown in FIG. 23 (a), three hydraulic pumps (first pump P1, second pump P2, third pump P3) are driven by the prime mover. Two of these hydraulic pumps (P1 and P2) are variable displacement hydraulic pumps, and the remaining one hydraulic pump (P3) is a hydraulic pump for turning work. At least the swing cylinder and the swing motor are driven by this hydraulic pump (P3). The hydraulic pump (P3) that supplies pressure oil to the swing motor is a fixed displacement type, and the movable swash plates of the two hydraulic pumps (P1 and P2) are controlled by the pressure of the hydraulic pump (P3). That is, as shown in FIG. 23B, the output of the hydraulic pumps (P1, P2) is reduced as the pressure of the hydraulic pump (P3) rises.

[0003]

FIG. 24 (a) is a diagram showing a situation of excavation work, and FIG. 24 (b) is a diagram showing a situation in which the position of the bucket is displaced by the hard ground. Figure 24 (a)
As shown in (1), when excavating a trench by an excavator, if the ground is hard, it is necessary to perform trench lateral excavation. As shown in FIG. 24 (b), the horizontal groove excavation is to excavate while pushing the bucket against the inner surface of the groove when straight ground cannot be excavated due to hard ground. In order to press the bucket against the groove for excavation, the bucket is always swung. As a result, the hard ground is dug straight down. However, the turning is performed by the turning motor, and when performing the horizontal groove excavation, the turning motor only generates a force for laterally pressing and does not rotate. Therefore, the pressure oil supplied by the hydraulic pump (P3) driving the swing motor is relieved by the relief valve. For this reason, energy loss becomes large when performing horizontal groove excavation.

Further, the structure of the control circuit is complicated, the number of parts is large, and the cost is high. Along with this, a lot of labor is required for work such as adjustment. Further, as shown in FIG. 23 (b), when the output of the hydraulic pumps (P1 and P2) is reduced as the pressure of the hydraulic pump (P3) rises, the driving speed of the arm and the bucket is significantly reduced and the work efficiency is increased. Will be reduced.

FIG. 25 is a diagram showing the relationship between the total input of the three pumps and the pump pressure. In the figure, the z-axis indicating the height direction indicates the input, and the x-axis and the y-axis respectively indicate the pressure of the third pump P3, the first pump P1 and the second pump P2.
It shows the pressure of. In FIG. 25, when the horizontal groove excavation is performed, the pressure of the third pump P3 is maximum. That is, as shown in FIG. 25, PL is input to the third pump P3, resulting in energy loss. The remaining PU is input to the first pump P1 and the second pump P2. The input PU drives the arm and the bucket. That is, in the above-mentioned technique, the input to the hydraulic pumps (P1 and P2) is reduced, and the work efficiency is reduced.

[0006]

In order to solve the above problems, the present invention uses the following means. The first and second variable displacement hydraulic pumps drive the excavation section, the third hydraulic pump drives the swing motor, and the first and second variable displacement hydraulic pumps are driven. The drive pressure of the swing motor is used for the flow rate control mechanism, and the third hydraulic pump has a variable displacement type.

As described in claim 2, the capacities of the first and second variable displacement hydraulic pumps are controlled by a common swash plate,
A hydraulic mechanism for performing subtraction control via the plunger by the driving pressure of the third hydraulic pump is configured.

According to a third aspect of the present invention, the first and second variable displacement hydraulic pumps are one-cylinder, two-flow hydraulic pumps.

According to a fourth aspect of the present invention, the third variable displacement hydraulic pump for driving the swing motor is controlled to have a constant output by self pressure.

According to a fifth aspect of the present invention, the self-pressure of the third variable hydraulic pump is connected to the plunger that controls the common swash plate of the first and second variable displacement hydraulic pumps for subtraction.

According to a sixth aspect of the present invention, the input increase amount of the third variable displacement hydraulic pump and the first variable displacement hydraulic pump within the pressure range until the flow rate of the third variable displacement hydraulic pump starts decreasing.
And the control force of the plunger is set so that the second variable displacement pump input reduction amount is substantially the same.

[0012] As described in claim 7, the first and second
A variable stopper is provided to limit the tilt angle of the swash plate.

As described in claim 8, the first and second
The swash plate tilt angle restriction position of the variable displacement pump of No. 1 is such that the first and second variable displacement pumps have the maximum pressure and the flow rate of the third variable displacement pump has reached the pressure at which the reduction starts. The tilt angles of the swash plates of the first and second variable displacement pumps at the time point were taken.

According to a ninth aspect of the present invention, a limiting device for regulating the pressure is provided between the plunger of the fifth aspect and the self pressure of the third variable displacement pump.

According to a tenth aspect of the present invention, the pressure regulation value between the connection between the plunger of the fifth aspect and the self-pressure of the third variable displacement pump is reduced by the flow rate of the third variable displacement pump. The pressure was set to start.

According to the eleventh aspect, the pressure limiting device according to the ninth aspect is a pressure reducing valve.

According to a twelfth aspect, the sum of the inputs of the first hydraulic pump, the second hydraulic pump and the third hydraulic pump is made substantially constant.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. 1 is an overall view of an excavator, FIG. 2 is a schematic diagram showing the configuration of a hydraulic pump, FIG. 3 is a diagram showing the configuration of pressure / flow rate / input of the first and second pumps, and FIG. 4 is a diagram of the third pump. FIG. 5 is a diagram showing the configuration of pressure / flow rate / input, and FIG. 5 is a diagram showing the configuration of pressure and input of the first, second, and third pumps. FIG. 6 is a diagram showing an example of the configuration of the first and second pumps, FIG. 7 is a diagram showing the configuration of the plunger barrel and the valve plate in another example of the configuration of the first and second pumps, and FIG. 8 is the first and second examples. It is a figure which shows the other example of a structure of a pump. FIG. 9 is a schematic diagram showing the configuration of self-pressure control of the third pump, and FIG. 10 is a schematic diagram showing the displacement control configuration of the first and second pumps and the third pump. FIG. 11 is a schematic diagram showing a configuration in which a stopper is provided in the displacement control configuration of the first and second pumps and the third pump,
FIG. 12 is a diagram showing the pressure / flow rate / input configuration of the first and second pumps with the stopper provided, and FIG. 13 is the first and second pumps and the third pump with the stopper provided.
FIG. 14 is a diagram showing the configuration of pressure / input of the pump, and FIG. 14 is a diagram showing the configuration of pressure / flow rate of the first and second pumps and the third pump when the stopper position is adjusted. FIG. 15 is a diagram showing a configuration in which the control units of the first and second pumps are controlled via the pressure control device, and FIG. 16 is a diagram showing the pressures of the first and second pumps and the third pump when the pressure control device is provided. FIG. 17 is a diagram showing the configuration of the flow rate, FIG. 17 is a diagram showing the configuration of the pressure and input of the first and second pumps when the pressure control device is provided, and FIG. 18 is the first and second pumps and the first pump when the pressure control device is provided. Three
It is a figure which shows the structure of the pressure and the input which were synthesize | combined of a pump.
FIG. 19 is a diagram showing a configuration in which the control units of the first and second pumps are controlled via the pressure reducing valve. 20 is a side sectional view showing the first embodiment of the first and second pumps and the third pump, FIG. 21 is a side sectional view showing the second embodiment of the first and second pumps and the third pump, FIG. FIG. 6 is a side sectional view showing a third embodiment of the first and second pumps and the third pump.

[Overall Configuration] The overall configuration of the excavating work machine used in the present invention will be described. In FIG. 1, the excavating work machine includes a swivel bearing 7 in the upper center of the crawler type traveling device 1.
Is disposed, and the swivel bearing 7 supports the swivel body 8 so that the swivel body 8 can swivel left and right. At the front and rear ends of the crawler type traveling device 1, an earth discharging plate 10 is arranged so as to be vertically rotatable.

Above the revolving structure 8, a hood 9 for covering the engine and a cabin 21 are arranged. Revolving structure 8
The lower end of the boom 6 is pivotally supported in a vertically rotatable manner on a boom bracket 12 which is rotatably attached to the front end of the boom 6. The revolving structure 8 is provided with an engine and a hydraulic pump, and the hydraulic pump is driven by the engine. Further, a hydraulic motor is arranged on the revolving structure 8, and the revolving structure 8 is rotated with respect to the crawler traveling device 1 by the hydraulic motor. The base of the arm 5 is pivotally supported at the tip of the boom 6, and one end of the bucket mounting portion 11 is pivotally supported at the tip of the arm 5. An attachment device such as the bucket 4 is mounted on the bucket mounting portion 11. The lower end of the boom cylinder 23 is rotatably supported by the boom bracket 12, and the boom 6 is expanded and contracted to rotate the boom 6 with respect to the boom bracket 12. An arm cylinder 25 is provided above the boom 6, and the arm 5 rotates with respect to the boom 6 when the arm cylinder 25 extends and contracts. A bucket cylinder 24 is disposed at the base of the arm 5, and the tip of the bucket cylinder 24 is connected to the connecting device 1 via a link mechanism.
1 is connected. The connecting device 11 is rotatably supported at the tip of the arm 5 and rotates with respect to the arm 5 when the bucket cylinder 24 extends and contracts.

[Overall Structure of Hydraulic Pump] As shown in FIG. 2, in an excavating work machine, an engine E drives three hydraulic pumps (P1, P2, P3). Pressure oil is supplied to the crawler traveling device 1, the bucket cylinder 24, the arm cylinder 25, and the like by the first hydraulic pump P1 and the second hydraulic pump P2. The first hydraulic pump P1 and the second hydraulic pump P2 are variable hydraulic pumps. The third hydraulic pump P3 is also a variable hydraulic pump, and the pressure oil is supplied to the turning hydraulic motor by the third hydraulic pump.

[Structure 1] Next, an example of the structure of the hydraulic pump arranged in the excavator will be described with reference to FIGS. 3 to 5. FIG. 3A is a diagram showing the relationship between the pressure and the flow rate of the hydraulic oil output from the first pump and the second pump, and FIG. 3B is the input to the first pump and the second pump and the pressure of the third pump. It is a figure which shows the relationship of. Driving force is input to the hydraulic pump, and the input energy is converted into a flow rate and pressure of hydraulic oil by the hydraulic pump and output. Therefore, the input to the hydraulic pump and the output from the hydraulic pump are substantially the same. The first pump P1 and the second pump P2 are variable pumps, and as shown in FIG. 3A, the total output of the first pump P1 and the second pump P2 is maintained within a fixed output. The total input to the first pump P1 and the second pump P2 is configured to decrease as the hydraulic oil pressure supplied from the third pump P3 increases. That is, the input to the first pump P1 and the second pump P2 is controlled by controlling the discharge amount of the hydraulic oil from the first pump P1 and the second pump P2 by the pressure of the third pump P3. . Inputs to the first pump P1 and the second pump P2 are as shown in FIG.
As shown in, the pressure of the third pump P3 decreases in proportion to the increase of the pressure.

FIG. 4A shows the relationship between the pressure and flow rate of the hydraulic oil output from the third pump, and FIG. 4B shows the input to the third pump and the pressures of the first pump and the second pump. It is a figure which shows a relationship. The third pump P3 is a variable pump, and as shown in FIG. 4A, the output of the third pump P3 is maintained within a constant output. Third pump P
By the pressure of 3, the first pump P1 and the second pump P2
By controlling the discharge amount of hydraulic oil, the input to the third pump P3 is controlled. As shown in FIG. 4B, when the pressure of the third pump P3 is higher than a certain pressure, the input to the third pump P3 becomes constant.

As a result, when the pressure of the hydraulic oil rises in the third pump P3, the input to the third pump P3 is limited. As shown in FIG. 5, the input to the third pump on the high pressure side of the third pump P3 is limited. Then, the hydraulic oil flow rate of the third pump is reduced during the horizontal groove excavation. By making the third pump P3 a variable displacement hydraulic pump, it is possible to limit the pressure rise of the hydraulic oil and suppress energy loss during lateral groove excavation. That is, the loss amount PL during lateral groove excavation can be reduced, and the energy loss can be significantly reduced. Then, the energy efficiency of the excavator is improved.

[Structure 2] Next, the first pump P1 and the second pump P1
The configuration of the first embodiment of the pump P2 will be described. Figure 6
As shown in, the first pump P1 and the second pump P2 are arranged in one pump case and share the movable swash plate 34. The pump case is the pump case 31.
It is composed of 32. The pump case 31 is the first
The pump P1 and the second pump P2 are mounted, and the pump case 32 covers the opening side of the pump case 31. The pump case 31 is provided with an oil passage for the first pump P1, and the pump case 32 is provided with an oil passage for the second pump P2.

An input shaft 33 is fitted in the first pump P1 and the second pump P2. The input shaft 33 is rotatably supported by pump cases 31 and 32. Further, the input shaft 33 has a first pump P1 and a second pump P2.
A swash plate 34, which is a movable swash plate, is inserted between and. An arm 35 is provided on the swash plate 34, and the abutment body of the adjusting portion 36 and the plunger 37 are in contact with the arm 35. The adjuster 36 is mounted on the pump case 32 and adjusts the spring force of the swash plate 34. And
The plunger 37 is in contact with the swash plate 34 so as to face the contact body of the adjusting portion 36.

The plunger 37 is slid toward the swash plate 34 by the pressure of the third pump P3. The third pump P3 is connected to one end of the plunger 37 via an oil passage.
Is transmitted, and the other end contacts the swash plate 34.
Therefore, the plunger 37 rotates the swash plate 34 to the neutral side as the pressure of the third pump P3 increases. As a result, the swash plate 37 is tilted and the flow rate is reduced.

The above-mentioned adjusting portion 36 urges the swash plate 34 so as to maintain the swash plate 34 at a constant angle.
The plunger 34 is connected to the first pump P1 and the second pump P1.
In order to reduce the capacity of the pump P2, the pressure of the third pump P3 urges the swash plate 34 toward the neutral side, that is, the flow rate reducing side. With this configuration, it is possible to easily adjust the capacities of the first pump P1 and the second pump P2. Then, the structure for adjusting the capacity of the first pump P1 and the second pump P2 by the pressure of the third pump P3 can be simplified.

[Structure 3] Next, the first pump P1 and the second pump P1
The configuration of the second embodiment of the pump P2 will be described with reference to FIGS. 7 and 8. As shown in FIG. 7, the first pump P
The first and second pumps P2 are composed of one hydraulic pump. By using a one-cylinder two-flow hydraulic pump as the hydraulic pump, one hydraulic pump is used as the first pump P1 and the second pump P2.

A piston 42 is housed in the cylinder barrel 43, and the tip of the piston 42 is in contact with the swash plate 41. The cylinder barrel 43 is provided with two types of ports. The port provided on the outside is the first pump P
1 port, and the port provided inside is the second pump P
2 ports. A valve plate 44 is arranged on the side of the cylinder barrel 43 where the port is provided. The valve plate 44 is provided with a discharge port 46 serving as a discharge port of the first pump P1 and a discharge port 47 serving as a discharge port of the second pump P2. Further, the valve plate 44 is provided with a common suction port 45. Hydraulic oil is introduced into the cylinder barrel 43 from the suction port 45. The hydraulic oil discharged from the discharge port 46 acts as hydraulic oil from the first pump P1, and the hydraulic oil discharged from the discharge port 47 acts as hydraulic oil from the second pump P2.

This hydraulic pump is arranged in a pump case 47 and is connected to an oil passage provided in an oil passage base 48.
The cylinder barrel 43 has an input shaft 49 inserted therein and is connected to an oil passage base 48 via the valve plate 44. The oil passage board 48 is provided with an adjusting portion 50, and one end of the swash plate 41 is in contact with the adjusting portion 50. Adjuster 5
0 is configured to urge the swash plate 41 in a direction in which the swash plate 41 is maintained at a constant angle.

The pump case 47 includes a plunger 51.
Has been inserted. The plunger 51 is slidably arranged parallel to the extending direction of the input shaft 49. One end of the plunger 51 is in contact with the swash plate 41. An oil passage is connected to the plunger 51 insertion portion of the pump case 47. The oil passage is connected to the hydraulic oil discharge side of the third pump P3. As a result, when the pressure in the third pump P3 rises, pressure is applied to the end portion of the plunger 51, causing the plunger 51 to slide toward the swash plate 41 side. With this configuration, the first pump P
It is possible to easily adjust the volumes of the first and second pumps P2. And the first by the pressure of the third pump P3
The structure for adjusting the capacity of the pump P1 and the second pump P2 can be simplified.

[Structure 4] Next, the structure of the constant output control of the third pump P3 will be described with reference to FIG. In FIG. 9, the hydraulic pump 55 is a pump that constitutes the first pump P1 and the second pump P2. And the third pump P3
The discharge amount of the hydraulic oil is controlled by the self pressure of the third pump. The control unit 57 is connected to the movable swash plate of the third pump P3. The control unit 57 is connected to an oil passage on the hydraulic oil supply side of the third pump P3. And the third pump P3
The hydraulic oil supply pressure controls the movable swash plate in the direction in which the hydraulic oil discharge amount decreases. The third pump P3
A spring 56 is connected to the movable swash plate and urges the movable swash plate to return to a preset angle. In this way, the third pump P3 is controlled by the pressure of the hydraulic oil discharged by the third pump P3, so that the configuration is simplified and reliable operation can be performed.

[Structure 5] Next, a structure in which the output control of the first pump P1, the second pump P2, and the third pump P3 is performed by the third pump P3 will be described with reference to FIG. In FIG. 10, the hydraulic pump 55 is the first pump P1.
And a pump that constitutes the second pump P2. Then, the hydraulic oil discharge amounts of the first pump P1, the second pump P2, and the third pump P3 are controlled by the self-pressure of the third pump. The control unit 57 is connected to the movable swash plate of the third pump P3. The control unit 57 is connected to an oil passage on the hydraulic oil supply side of the third pump P3. And the third pump P
With the hydraulic oil supply pressure of 3, the movable swash plate is controlled in the direction in which the hydraulic oil discharge amount decreases. Further, a control unit 58 is connected to the oil passage on the hydraulic oil supply side of the third pump P3. The controller 58 controls the amount of hydraulic oil discharged from the movable swash plate of the hydraulic pump 55.

The control section 58 is composed of a plunger and a spring. Due to the increase of the hydraulic oil supply pressure of the third pump P3, the plunger pushes the movable swash plate of the hydraulic pump 55, and the hydraulic oil discharge amount is reduced. Then, the spring of the control portion 58 urges the movable swash plate of the hydraulic pump 55 so as to return to the preset angle. In this way, the first pump P1, the second pump P2, and the third pump P3 are controlled by the pressure of the hydraulic oil discharged by the third pump P3, so that the configuration is simplified and reliable operation can be performed. .

Further, by adjusting the diameter of the plunger used in the controller 58 with respect to the diameter of the plunger used in the controller 57, the total input to the first pump P1, the second pump P2 and the third pump P3 can be calculated. Can be constant. Within the pressure range until the flow rate of the variable displacement hydraulic pump of the third pump P3 starts decreasing, the third pump P3
Input increase amount and the first pump P1 and the second pump P2
The control force of the plunger is set so that the input decrease amount of is approximately the same. By adjusting the force of pushing the movable swash plate of the plunger used in the control units 58 and 57 and the restoring force of the spring, the input increase amount of the third pump P3 and the input of the first pump P1 and the second pump P2 are adjusted. The amount of decrease and the amount of decrease can be adjusted respectively. Then, by making the input increase amount and the input decrease amount substantially the same, while making the total of the inputs to the first pump P1, the second pump P2, and the third pump P3 constant, excavation such as lateral groove digging is performed. Work efficiency can be improved. Further, it is possible to configure an excavating machine having a simple structure, high productivity, stable operability, and low manufacturing cost.

[Structure 6] Next, the first pump P1 and the second pump P1
A configuration for reducing the hydraulic oil supply amount of the pump P2 within a certain range will be described with reference to FIGS. 11 to 13. In this configuration, the control unit 5 that controls the swash plate of the hydraulic pump 55
8 is provided with a stopper. Then, the flow rates of the hydraulic oils of the first pump P1 and the second pump P2 are secured.
The hydraulic pump 55 includes a first pump P1 and a second pump P2.
Is a pump that constitutes. Then, the hydraulic oil discharge amounts of the first pump P1, the second pump P2, and the third pump P3 are
It is controlled by the self-pressure of the third pump. Third pump P3
A control unit 57 including a plunger and a spring is connected to the movable swash plate. A control unit 58 is connected to the movable swash plate of the hydraulic pump 55.

The control section 57 and the control section 58 are connected to an oil passage on the hydraulic oil supply side of the third pump P3. The hydraulic oil supply pressure of the third pump P3 controls the movable swash plates respectively connected in the direction in which the hydraulic oil discharge amount decreases. The controller 58 is provided with a stopper 59. The stopper 59 limits the rotation of the movable swash plate in the discharge amount decreasing direction by the plunger of the control unit 58. That is, the amount of rotation of the movable swash plate is limited due to the increase in the hydraulic oil supply pressure of the third pump P3. This ensures the amount of hydraulic oil discharged from the first pump P1 and the second pump P2.

The relationship between the flow rate and the pressure of the hydraulic oil of the first pump P1 and the second pump P2 will be described with reference to FIG. FIG. 12A is a diagram showing the relationship between the pressure and the flow rate of the hydraulic oil output from the first pump and the second pump.
(B) is a figure which shows the relationship between the input to a 1st pump and a 2nd pump, and the pressure of a 3rd pump. The first pump P1 and the second pump P2 are variable pumps, and as shown in FIG. 12A, the total output of the first pump P1 and the second pump P2 is maintained within a fixed output.
Then, the total input to the first pump P1 and the second pump P2 is configured to decrease as the hydraulic oil pressure supplied from the third pump P3 increases. However, due to the stopper 59 described above, even if the hydraulic oil pressure of the third pump P3 is high on the low flow rate side, the first pump P1 and the second pump P3
The supply pressure of 2 does not decrease.

That is, by the pressure of the third pump P3,
The discharge amounts of the first pump P1 and the second pump P2 are controlled, and in the first pump P1 and the second pump P2, a constant flow rate is secured by a stopper 59. Thereby, the first pump P1 and the second pump P
As shown in FIG. 12B, the input to the second pump 2 can ensure the input to the first pump P1 and the second pump P2 in a certain region even when the third pump P3 has a high pressure.

Then, as shown in FIG. 13, when performing horizontal groove excavation, the PU input to the first pump P1 and the second pump P2 is changed to the PL input to the third pump P3.
Can be increased. That is, even in the lateral groove excavation work, it is possible to reduce the decrease in the excavation speed due to the bucket, the arm, etc., and improve the work efficiency.

[Structure 8] Further, by setting the position of the stopper 59, the inputs to the three pumps can be kept constant while maintaining the maximum pressures of the first pump P1 and the second pump P2. FIG. 14A is a diagram showing the relationship between the pressure and the flow rate of the first pump and the second pump, and FIG. 14B is a diagram showing the relationship between the pressure and the flow rate of the third pump. At the pressure at the point where the flow rate of the third pump P3 decreases due to the increase in pressure, the stopper 5 is placed at the swash plate position where the maximum pressure of the constant output curve indicated by the first pump P1 and the second pump P2 is reached.
By providing 9, the inputs to the three pumps can be kept constant while maintaining the maximum pressures of the first pump P1 and the second pump P2. In the third pump P3, the pressure at which the flow rate starts decreasing is referred to as the pressure Ps. And the third
The first pump P when the pressure of the pump P3 is the pressure Ps
The curve indicating the relationship between the pressure and the flow rate of the first and second pumps P2 is referred to as curve F. Further, the flow rate when the curve F shows the maximum pressure is defined as the flow rate Vs.

In this case, the stopper 59 is provided so as to operate at the position where the angle of the movable swash plate becomes the flow rate Vs, so that the three pumps are maintained while maintaining the maximum pressures of the first pump P1 and the second pump P2. The input of can be kept constant. By setting the stopper 59 in this way, it is possible to reduce the load on the engine or the like that drives the hydraulic pump. Then, the excavation work can be performed while preventing the engine stall.

[Structure 9] Next, the first pump P1 and the second pump P1
Another example of the swash plate control configuration of the pump P2 will be described with reference to FIGS. 15A is a schematic diagram of a swash plate control mechanism of a hydraulic pump to which a pressure limiting device is connected, FIG.
FIG. 15B is a diagram showing a pressure change at point A, and FIG.
FIG. 6 is a diagram showing a pressure change at a point B. FIG. 15 (a)
As shown in FIG. 5, a control unit 58 that controls the swash plate of the hydraulic pump 55 that constitutes the first pump P1 and the second pump P2.
And the pressure limiting device 60 is arranged in the oil passage connecting the hydraulic oil discharge side of the third pump P3. Then, the pressure applied to the control unit 58 is set to a certain value or less by the pressure limiting device 60. It is assumed that the pressure increases at a point A between the pressure limiting device 60 and the third pump P3, as shown in FIG. 15 (b). In this case, the pressure at the point B between the pressure limiting device 60 and the control unit 58 is maintained at a constant pressure Pd as shown in FIG. 15 (c). Pressure limiting device 60
Does not work when the pressure applied to the control unit 58 is lower than the pressure Pd, and transmits the pressure of the third pump P3 to the control unit 58. When the pressure of the third pump P3 is higher than the pressure Pd, the pressure applied to the controller 58 is maintained at the pressure Pd.

FIG. 16 (a) is a diagram showing the relationship between the pressure and the flow rate of the first pump and the second pump in the configuration without the pressure limiting device, and FIG. 16 (b) is the first pump in the configuration having the pressure limiting device. It is a figure which shows the pressure of a 2nd pump, and the relationship of a flow volume. As shown in FIG. 16 (b), since the pressure above a certain level is not transmitted to the control unit 58, the output control of the first pump and the second pump due to the pressure increase of the third pump P3 is not performed. That is, the lower limits of the outputs of the first pump and the second pump are increased. Accordingly, the input to the first pump and the second pump is as shown in FIG.
The characteristics shown in are. Then, by combining with the third hydraulic pump P3 that controls the input by self-pressure having the characteristic shown in FIG. 4, as shown in FIG. 18, the first pump and the second pump in the state where the pressure of the third hydraulic pump P3 is high. Can take large input to. For this reason, it is possible to reduce the decrease in the excavation speed and improve the efficiency of the lateral groove excavation work.

[Structure 10] In the structure using the pressure limiting device 60, by adjusting the pressure applied to the controller 58, the total input of the first pump P1, the second pump P2, and the third pump P3 is made constant. Can be The pressure Pd which is the limit value of the pressure limiting device 60 is set to the third
The pressure is matched with the pressure at which the flow rate of the pump P3 starts to decrease. That is, the pressure at which the pressure applied to the control unit 58 is limited and the pressure at which the flow rate is reduced by the control unit 57 are matched. This makes it possible to make the inputs of the first pump P1 and the second pump P2 constant at the timing when the flow rate of the third pump P3 decreases and the input to the third pump P3 becomes constant. And the first pump P
The total input of the first, second pump P2 and third pump P3 is constant.

[Structure 11] In the structure using the pressure limiting device 60 described above, as shown in FIG.
A pressure reducing valve 61 can be used as the zero embodiment.
19A is a schematic diagram of a swash plate control mechanism of a hydraulic pump to which a pressure limiting device is connected, FIG. 19B is a diagram showing a pressure change at a point A, and FIG. 19C is a pressure change at a point B. FIG. As shown in FIG. 19A, an oil passage that connects the control unit 58 that controls the swash plate of the hydraulic pump 55 that constitutes the first pump P1 and the second pump P2, and the hydraulic oil discharge side of the third pump P3. The pressure reducing valve 61 is provided in the. Then, the pressure reducing valve 61 sets the pressure applied to the control unit 58 to a certain value or less. At point A, the pressure is
When rising as shown in (b), the pressure at point B becomes
The pressure reducing valve 61 maintains a constant pressure Pd as shown in FIG. The pressure reducing valve 61 does not operate when the pressure applied to the controller 58 is lower than the pressure Pd. When the pressure of the third pump P3 is higher than the pressure Pd, the pressure applied to the controller 58 is maintained at the pressure Pd. This makes it possible to increase the input to the first pump and the second pump when the pressure of the third hydraulic pump P3 is high.

[Structure 12] Next, a first embodiment of three hydraulic pumps will be described. In FIG. 20, the first pump P1 and the second pump P2 are configured by one hydraulic pump 62. The hydraulic pump 62 has two cylinders.
It is composed of a flow type hydraulic pump, and one hydraulic pump is used as the first pump P1 and the second pump P2. The third pump P3 is composed of a hydraulic pump P3. The hydraulic pump 62 and the hydraulic pump 63 are connected by the connecting portion 64.

In the hydraulic pump 62, the piston 42 is housed in the cylinder barrel 43.
The tip of 2 is in contact with the swash plate 41. Cylinder barrel 4
3 has two types of ports. The port provided on the outer side becomes the port of the first pump P1, and the port provided on the inner side becomes the port of the second pump P2. On the side where the port of the cylinder barrel 43 is provided, the valve plate 44
Is provided. The valve plate 44 has a first pump P
Discharge port to be the first discharge port and the second pump P2
Is provided as a discharge port. Further, the valve plate 44 is provided with a common suction port. The hydraulic oil is introduced into the cylinder barrel 43 from the suction port of the valve plate 44. The hydraulic oil is supplied to the discharge port of the first pump P1 and the second pump P2.
Is discharged from the discharge port.

The hydraulic pump 62 is disposed in the pump case 47 and is connected to the oil passage provided in the oil passage base 48.
The cylinder barrel 43 has an input shaft 49 inserted therein and is connected to an oil passage base 48 via the valve plate 44. The oil passage board 48 is provided with an adjusting portion 50, and one end of the swash plate 41 is in contact with the adjusting portion 50. Adjuster 5
0 is configured to urge the swash plate 41 in a direction in which the swash plate 41 is maintained at a constant angle.

The pump case 47 includes a plunger 51.
Has been inserted. The plunger 51 is slidably arranged parallel to the extending direction of the input shaft 49. One end of the plunger 51 is in contact with the swash plate 41. An oil passage 81 is connected to the plunger 51 insertion portion of the pump case 47. The oil passage 81 is connected to the hydraulic oil discharge side of the hydraulic pump 63 that constitutes the third pump P3. As a result, when the pressure in the third pump P3 rises, pressure is applied to the end portion of the plunger 51, causing the plunger 51 to slide toward the swash plate 41 side.

The hydraulic pump 63 is disposed in the pump case 77 and is connected to the oil passage provided on the oil passage board 78.
The input shaft 79 is inserted into the cylinder barrel 73. The input shaft 79 is connected to the input shaft 49 of the hydraulic pump 62 and rotates integrally with the input shaft 49. The cylinder barrel 73 is connected to the oil passage board 78 via the valve plate 74. An adjusting portion 80 is provided on the oil passage board 78, and one end of the swash plate 71 is in contact with the adjusting portion 80. The adjusting unit 80 is configured to bias the swash plate 71 in a direction that maintains the swash plate 71 at a constant angle.

The hydraulic pump 62 and the hydraulic pump 63 are connected by a connecting portion 64. The hydraulic pump 62,
An oil passage 81 is provided in the connecting portion 64 and the hydraulic pump 63. The oil passage 81 is connected to the discharge-side oil passage of the hydraulic pump 63,
It connects with the plunger 51 provided in the hydraulic pump 62. The oil passage 81 is the oil passage board 7 of the hydraulic pump 63.
8, the pump case 77, the connecting portion 64, the oil passage board 48 of the hydraulic pump 62, and the pump case 47.

As a result, the pressure on the discharge side of the hydraulic pump 63, which is the third pump P3, is transmitted to the plunger 51,
The swash plate 41 of the hydraulic pump 62 constituting the first pump P1 and the second pump P2 can be controlled. Since the control case of the movable swash plate is provided in the pump case of the hydraulic pump, the oil passage board, and the connection portion 64, a simple structure can be obtained. With this configuration, it is possible to easily adjust the capacities of the first pump P1 and the second pump P2. And the third pump P3
The structure for adjusting the capacities of the first pump P1 and the second pump P2 by the pressure can be simplified. Also,
The cost can be reduced and a highly reliable hydraulic pump can be configured.

[Structure 13] Next, a second embodiment of the three hydraulic pumps will be described. In FIG. 21, the first pump P1 and the second pump P2 are constituted by one hydraulic pump 62. The hydraulic pump 62 has two cylinders.
It is composed of a flow type hydraulic pump, and one hydraulic pump is used as the first pump P1 and the second pump P2. The third pump P3 is composed of a hydraulic pump P3. The hydraulic pump 62 and the hydraulic pump 63 are connected by the connecting portion 64.

In the hydraulic pump 62, the piston 42 is housed in the cylinder barrel 43.
The tip of 2 is in contact with the swash plate 41. Cylinder barrel 4
3 has two types of ports. The port provided on the outer side becomes the port of the first pump P1, and the port provided on the inner side becomes the port of the second pump P2. On the side where the port of the cylinder barrel 43 is provided, the valve plate 44
Is provided. The valve plate 44 has a first pump P
Discharge port to be the first discharge port and the second pump P2
Is provided as a discharge port. Further, the valve plate 44 is provided with a common suction port. The hydraulic oil is introduced into the cylinder barrel 43 from the suction port of the valve plate 44. The hydraulic oil is supplied to the discharge port of the first pump P1 and the second pump P2.
Is discharged from the discharge port.

The hydraulic pump 62 is disposed in the pump case 47 and is connected to the oil passage provided in the oil passage base 48.
The cylinder barrel 43 has an input shaft 49 inserted therein and is connected to an oil passage base 48 via the valve plate 44. The oil passage board 48 is provided with an adjusting portion 50, and one end of the swash plate 41 is in contact with the adjusting portion 50. Adjuster 5
0 is configured to urge the swash plate 41 in a direction in which the swash plate 41 is maintained at a constant angle.

The pump case 47 includes a plunger 51.
Has been inserted. The plunger 51 is slidably arranged parallel to the extending direction of the input shaft 49. One end of the plunger 51 is in contact with the swash plate 41. An oil passage 81 is connected to the plunger 51 insertion portion of the pump case 47. The oil passage 81 is connected to the hydraulic oil discharge side of the hydraulic pump 63 that constitutes the third pump P3. As a result, when the pressure in the third pump P3 rises, pressure is applied to the end portion of the plunger 51, causing the plunger 51 to slide toward the swash plate 41 side.

The hydraulic pump 63 is arranged in the pump case 77 and is connected to the oil passage provided in the oil passage board 78.
The input shaft 79 is inserted into the cylinder barrel 73. The input shaft 79 is connected to the input shaft 49 of the hydraulic pump 62 and rotates integrally with the input shaft 49. The cylinder barrel 73 is connected to the oil passage board 78 via the valve plate 74. An adjusting portion 80 is provided on the oil passage board 78, and one end of the swash plate 71 is in contact with the adjusting portion 80. The adjusting unit 80 is configured to bias the swash plate 71 in a direction that maintains the swash plate 71 at a constant angle.

The hydraulic pump 62 and the hydraulic pump 63 are connected by a connecting portion 64. The hydraulic pump 62,
An oil passage 81 is provided in the connecting portion 64 and the hydraulic pump 63. The oil passage 81 is connected to the discharge-side oil passage of the hydraulic pump 63,
It connects with the plunger 51 provided in the hydraulic pump 62. The oil passage 81 is the oil passage board 7 of the hydraulic pump 63.
8, the pump case 77, the connecting portion 64, the oil passage board 48 of the hydraulic pump 62, and the pump case 47.

Further, the hydraulic pump shown in the second embodiment is provided with a limiting stopper 82. The limit stopper 82 limits the amount of rotation of the swash plate 41. As a result, the lower limit of the capacity of the hydraulic pump 62 is determined. The limiting stopper 82 is provided on the pump case 47 above the swash plate 41, and is fixed to the inner surface of the pump case 47. The limit stopper 82 is provided on the opposite side of the plunger 51 with respect to the input shaft 49. As a result, the swash plate 41 in the capacity decreasing direction by the plunger 51
It is possible to regulate the rotation of the and keep the lower limit of the capacity.

As a result, the input to the first pump P1 and the second pump P2 can be ensured to be the input to the first pump P1 and the second pump P2 in a certain region even when the third pump P3 has a high pressure. It is possible. Then, when performing horizontal groove excavation, the input to the first pump P1 and the second pump P2 can be increased with respect to the input to the third pump P3. Also in the lateral groove excavation work, it is possible to reduce the decrease in the excavation speed due to the bucket, the arm, and the like, and improve the work efficiency.

[Structure 14] Next, a third embodiment of the three hydraulic pumps will be described. In FIG. 22, the first pump P1 and the second pump P2 are constituted by one hydraulic pump 62. The hydraulic pump 62 has two cylinders.
It is composed of a flow type hydraulic pump, and one hydraulic pump is used as the first pump P1 and the second pump P2. The third pump P3 is composed of a hydraulic pump P3. The hydraulic pump 62 and the hydraulic pump 63 are connected by the connecting portion 64.

In the hydraulic pump 62, the cylinder barrel 43 is provided with two types of ports. The port provided on the outer side becomes the port of the first pump P1, and the port provided on the inner side becomes the port of the second pump P2. Correspondingly, the valve plate 44 is provided with a discharge port that serves as a discharge port of the first pump P1 and a discharge port that serves as a discharge port of the second pump P2.

The hydraulic pump 62 is arranged in the pump case 47 and is connected to the oil passage provided in the oil passage base 48.
The cylinder barrel 43 has an input shaft 49 inserted therein and is connected to an oil passage base 48 via the valve plate 44. The oil passage board 48 is provided with an adjusting portion 50, and one end of the swash plate 41 is in contact with the adjusting portion 50. Adjuster 5
0 is configured to urge the swash plate 41 in a direction in which the swash plate 41 is maintained at a constant angle.

The pump case 47 includes a plunger 51.
Has been inserted. The plunger 51 is slidably arranged parallel to the extending direction of the input shaft 49. One end of the plunger 51 is in contact with the swash plate 41. An oil passage 81 is connected to the plunger 51 insertion portion of the pump case 47. The oil passage 81 is connected to the hydraulic oil discharge side of the hydraulic pump 63 that constitutes the third pump P3. As a result, when the pressure in the third pump P3 rises, pressure is applied to the end portion of the plunger 51, causing the plunger 51 to slide toward the swash plate 41 side.

The hydraulic pump 63 is arranged in the pump case 77 and is connected to the oil passage provided in the oil passage board 78.
The input shaft 79 is inserted into the cylinder barrel 73. The input shaft 79 is connected to the input shaft 49 of the hydraulic pump 62 and rotates integrally with the input shaft 49. The cylinder barrel 73 is connected to the oil passage board 78 via the valve plate 74. An adjusting portion 80 is provided on the oil passage board 78, and one end of the swash plate 71 is in contact with the adjusting portion 80. The adjusting unit 80 is configured to bias the swash plate 71 in a direction that maintains the swash plate 71 at a constant angle.

The hydraulic pump 62 and the hydraulic pump 63 are connected by a connecting portion 64. The hydraulic pump 62,
An oil passage 81 is provided in the connecting portion 64 and the hydraulic pump 63. The oil passage 81 is connected to the discharge-side oil passage of the hydraulic pump 63,
It connects with the plunger 51 provided in the hydraulic pump 62. The oil passage 81 is the oil passage board 7 of the hydraulic pump 63.
8, the pump case 77, the connecting portion 64, the oil passage board 48 of the hydraulic pump 62, and the pump case 47.

Further, the hydraulic pump shown in the third embodiment is equipped with a pressure limiting device 83. The pressure limiting device 83 is provided on an oil passage connecting the hydraulic oil discharge side of the hydraulic pump 63, which is the third pump P3, and the plunger 51, which is disposed in the hydraulic pump 62, which is the first pump P1 and the second pump P2. It is provided. The pressure in the hydraulic oil discharge side oil passage of the hydraulic pump 63 is transmitted to the plunger 51 via the pressure limiting device 83. This allows
The upper limit of the pressure applied to the plunger 51 can be adjusted by the pressure control device 83. Then, it is possible to obtain a large input to the first pump and the second pump when the pressure of the third hydraulic pump P3 is high. For this reason, it is possible to reduce the decrease in the excavation speed and improve the efficiency of the lateral groove excavation work.

[0070]

According to the first aspect of the present invention, the excavation section is driven by the first and second variable displacement hydraulic pumps, and the swing motor is driven by the third hydraulic pump. The drive pressure of the swing motor is used for the flow rate control mechanism of the displacement hydraulic pump, and the third hydraulic pump is of the variable displacement type, so energy loss can be reduced when performing horizontal groove excavation, and efficient work is possible. Can be done.

As described in claim 2, the capacities of the first and second variable displacement hydraulic pumps are controlled by a common swash plate,
Since the hydraulic mechanism for performing the subtraction control via the plunger by the driving pressure of the third hydraulic pump is configured, the structure is simple and the productivity is good, the operation is reliable, and the manufacturing cost can be reduced.

Since the first and second variable displacement hydraulic pumps are 1-cylinder, 2-flow hydraulic pumps, the structure is simple, the productivity is good, the operation is reliable, and the manufacturing cost is high. Can be reduced.

According to the fourth aspect of the present invention, the third variable displacement hydraulic pump for driving the swing motor is subjected to constant output control by self pressure, so that the structure is simple and the productivity is good, the operation is reliable, and the manufacturing cost is high. Can be reduced.

As described in claim 5, since the plunger for performing the subtraction control of the common swash plate of the first and second variable displacement hydraulic pumps is connected to the self pressure of the third variable hydraulic pump, the structure is simple. The productiveness is good, the operation is reliable, and the manufacturing cost can be reduced.

As described in claim 6, within the pressure range until the flow rate of the third variable displacement hydraulic pump starts decreasing, the input increase amount of the third variable displacement hydraulic pump and the first variable displacement hydraulic pump
Since the control force of the plunger is set so that the second variable displacement pump input reduction amount and the second variable displacement pump input reduction amount are substantially the same, the structure is simple and the productivity is good, the operation is reliable, and the manufacturing cost can be reduced.

As described in claim 7, first and second
Since the limit stopper for regulating the tilt angle of the swash plate of the variable displacement pump is provided, it is possible to reduce the decrease in excavation speed.

As described in claim 8, the first and second
The swash plate tilt angle restriction position of the variable displacement pump of No. 1 is such that the first and second variable displacement pumps have the maximum pressure and the flow rate of the third variable displacement pump has reached the pressure at which the reduction starts. Since the swash plate tilt angle of the first and second variable displacement pumps at the time point is set, the engine stall can be prevented and the drop in the excavation speed can be reduced.

As described in claim 9, since the restriction device for restricting the pressure is provided between the plunger of claim 5 and the self-pressure of the third variable displacement pump, the excavation speed is prevented from decreasing. Can be reduced.

According to the tenth aspect, the pressure regulation value between the connection between the plunger according to the fifth aspect and the self-pressure of the third variable displacement pump is set so that the flow rate of the third variable displacement pump is reduced. It is possible to reduce the decrease in excavation speed over a wide range up to the limit of starting pressure and stalling.

According to the eleventh aspect, since the pressure limiting device according to the ninth aspect is the pressure reducing valve, the structure is simple and the productivity is good, the operation is reliable, and the manufacturing cost can be reduced.

As described in claim 12, since the sum of the inputs of the first hydraulic pump, the second hydraulic pump and the third hydraulic pump is made substantially constant, the structure is simple, the productivity is good, and the operation is good. Certainly, the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is an overall view of an excavation work machine.

FIG. 2 is a schematic diagram showing a configuration of a hydraulic pump.

FIG. 3 is a diagram showing a configuration of pressure / flow rate / input of first and second pumps.

FIG. 4 is a diagram showing a configuration of pressure, flow rate, and input of a third pump.

FIG. 5 is a diagram showing a configuration of pressures and inputs of first and second pumps and a third pump.

FIG. 6 is a diagram showing an example of a configuration of first and second pumps.

FIG. 7 is a diagram showing a configuration of a plunger barrel and a valve plate in another configuration example of the first and second pumps.

FIG. 8 is a diagram showing another configuration example of the first and second pumps.

FIG. 9 is a schematic diagram showing the configuration of self-pressure control of a third pump.

FIG. 10 is a schematic diagram showing a displacement control configuration of first and second pumps and a third pump.

FIG. 11 is a schematic diagram showing a configuration in which stoppers are provided in the displacement control configurations of the first and second pumps and the third pump.

FIG. 12 is a diagram showing a first and a second configuration in which a stopper is provided.
The figure which shows the structure of pressure, flow volume, and input of a pump.

FIG. 13 is a diagram showing a pressure / input configuration of the first and second pumps and the third pump in a configuration provided with a stopper.

FIG. 14 shows the first and second positions when the stopper position is adjusted.
The figure which shows the structure of the pressure and flow volume of a pump and a 3rd pump.

FIG. 15 is a diagram showing a configuration in which the control units of the first and second pumps are controlled via a pressure control device.

FIG. 16: First and second with pressure control device
The figure which shows the structure of the pressure and flow volume of a pump and a 3rd pump.

FIG. 17: First and second case with pressure control device
The figure which shows the structure of pump pressure and input.

FIG. 18: First and second case with pressure control device
The figure which shows the structure of the pressure and the input which the pump and the 3rd pump combined.

FIG. 19 is a diagram showing a configuration in which the control units of the first and second pumps are controlled via a pressure reducing valve.

FIG. 20 is a side sectional view showing a first embodiment of the first and second pumps and the third pump.

FIG. 21 is a side sectional view showing a second embodiment of the first and second pumps and the third pump.

FIG. 22 is a side sectional view showing a third embodiment of the first and second pumps and the third pump.

FIG. 23 is a schematic diagram showing the configuration of three conventional hydraulic pumps.

FIG. 24 is a view showing the structure of a horizontal groove excavation work.

FIG. 25 is a diagram showing the relationship between the total input of three pumps and the pump pressure.

[Explanation of symbols]

P1 first pump P2 second pump P3 3rd pump 41 Swash plate 42 piston 43 cylinder barrel 44 valve plate 47 pump case 48 oil roadbed 50 Control unit 51 Plunger 55 hydraulic pump 56 spring 57 control unit

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2D003 AA01 AB01 AB02 AB03 AB04                       AC09 BA01 BA05 CA05 DA03                       DB02                 3H070 AA01 BB04 CC13 DD39 DD43                       DD55                 3H084 AA08 AA16 AA45 BB12 CC32                       CC48 CC64

Claims (12)

[Claims] 1. A flow rate control mechanism for the first and second variable displacement hydraulic pumps, wherein an excavation unit is driven by the first and second variable displacement hydraulic pumps, and a swing motor is driven by a third hydraulic pump. The excavator is characterized in that the drive pressure of the swing motor is used for the third hydraulic pump and the third hydraulic pump is of a variable displacement type. 2. A hydraulic mechanism for controlling the displacements of the first and second variable displacement hydraulic pumps by a common swash plate, and performing subtraction control via the plunger by the drive pressure of the third hydraulic pump. The excavating work machine according to claim 1, which is characterized in that. 3. A first variable displacement hydraulic pump and a second variable displacement hydraulic pump.
The excavator according to claim 2, wherein the hydraulic pump is a cylinder 2 flow type hydraulic pump. 4. The excavating work machine according to claim 1, wherein the third variable displacement hydraulic pump for driving the swing motor is subjected to constant output control by self pressure. 5. The self-pressure of the third variable hydraulic pump is connected to a plunger for performing subtractive control on the common swash plate of the first and second variable displacement hydraulic pumps. Excavator work machine. 6. The input increase amount of the third variable displacement hydraulic pump and the first and second variable displacement types within a pressure range until the flow rate of the third variable displacement hydraulic pump starts decreasing. The control force of the plunger is set such that the pump input reduction amount is substantially the same as the pump input reduction amount.
The excavating work machine according to any one of 1. 7. The excavating work machine according to claim 1, further comprising a limit stopper for regulating a tilt angle of the swash plate of each of the first and second variable displacement pumps. . 8. The swash plate tilt angle restriction positions of the first and second variable displacement pumps are set so that the first and second variable displacement pumps have the maximum pressure and the third variable displacement pump has the maximum pressure. The excavating work machine according to claim 7, wherein the swash plate tilt angles of the first and second variable displacement pumps are set at the time when the flow rate reaches a pressure at which the flow rate starts to decrease. 9. A limiting device for regulating pressure is provided between the plunger of claim 5 and the self-pressure of the third variable displacement pump. The excavating work machine according to claim 1. 10. The pressure regulation value between the connection between the plunger according to claim 5 and the self pressure of the third variable displacement pump is set to a pressure at which the flow rate of the third variable displacement pump starts to decrease. The excavating work machine according to claim 9, wherein 11. An excavating work machine comprising the pressure limiting device according to claim 9 as a pressure reducing valve. 12. The excavation according to claim 9, wherein a sum of inputs of the first hydraulic pump, the second hydraulic pump, and the third hydraulic pump is made substantially constant. Working machine.