JP3535951B2 - Hydraulic excavator hydraulic drive - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive system for a hydraulic excavator, and more particularly to a start acceleration of each structural part of the hydraulic excavator regardless of changes in posture, position, load condition, and inertia. The present invention relates to a hydraulic drive system capable of significantly improving the characteristics at time or during deceleration stop.

[0002]

2. Description of the Related Art Generally, hydraulic cylinders and hydraulic motors are known as hydraulic actuators for hydraulic excavators. The present invention can be applied to any of the actuators described above, and here, the most typical swing motor will be described.

However, in the hydraulic excavator, since the swing brake angle of the upper swing body changes depending on the posture of the working machine and the load state of the bucket, the swing stop position is predicted in advance to start the swing stop instruction, that is, the swing lever. Need to be returned to the neutral position, and the operator initiates the turning stop instruction depending on the amount of earth and sand scooped into the bucket.
It is difficult to operate, requires skill, and fatigue increases during long-term work. Further, an unskilled operator has a difficulty in the operation, and if the instruction to start turning stop is late, the upper turning body collides with the dump truck or the like beyond the turning stop position, which is a safety problem.

From such a point of view, conventionally, as a hydraulic circuit for controlling the turning stop of a revolving structure driven by a hydraulic motor such as a hydraulic excavator, in particular, an upper revolving structure caused by a posture of a working machine and a load state of a bucket is used. A hydraulic circuit of a hydraulic excavator has been proposed that allows even an unskilled person to stop at a predetermined position without being affected by changes in the moment of inertia (JP-A-9-13429).

The hydraulic circuit of the hydraulic excavator according to the above-mentioned proposal includes a working machine including a boom, an arm and a bucket attached to an upper revolving structure, and a directional control valve for revolving which controls the direction of pressure oil discharged from a hydraulic pump. And a hydraulic circuit of a hydraulic excavator equipped with a relief valve in a pipeline branching from a downstream pipeline of the turning directional control valve, and a holding pressure generated in a bottom pipeline of a boom cylinder that drives the boom. It comprises a detecting means for detecting and a control device for outputting a command signal to the relief valve in response to a signal from the detecting means to make the set pressure variable.

That is, in this conventional technique, the feeling at the time of turning stop changes due to the change of the inertia moment of the upper swing body caused by the expansion / contraction state of each cylinder of the hydraulic excavator, particularly the boom cylinder, and the load state of the bucket. (In particular, shock occurs when inertia is small)
As a method for improving the above, there is disclosed a method in which the load pressure of the boom cylinder is used to make the set pressure of the relief valve attached to the swing motor (actuator) variable.

Further, it is possible to reduce the impact at the time of starting and stopping the hydraulic actuator, and further to improve the operability, reduce the operator's feeling of fatigue, and improve the durability. In a directional control valve drive hydraulic circuit including a directional control valve for controlling the drive of a large hydraulic actuator and a pilot valve for operating the directional control valve, a pilot valve is connected between the pilot valve and the directional control valve. A first port, a second port that communicates with the direction switching valve, a spool that opens and closes between the first port and the second port, and the first port that is integrally configured with the spool. And a second port, which are interposed in the flow path and move the spool by the pressure difference on both sides thereof, and an opening whose area is controlled by the movement of the spool. Hydraulic circuit is interposed between the pressure compensated flow control valve that is has been proposed (real fair 3-272
No. 2).

In the directional control valve drive hydraulic circuit having the above-mentioned structure, the flow control valve with pressure compensation is interposed in both pilot lines connecting the pilot valve and the directional control valve, so that the traveling motor is stopped. It is possible to reduce the impact, improve the operability and durability, and reduce the operator's fatigue.

[0009]

However, in the above-mentioned prior art, in the former hydraulic circuit of the hydraulic excavator, the operability at the time of deceleration of the upper revolving superstructure is improved by changing the inertia moment of the hydraulic excavator.・ The set pressure of the relief valve that controls braking is adjusted, but in this case, the structure of the relief valve is relatively complicated, and the working pressure is practically about 200 kgf / cm 2 or more. Moreover, it is difficult to make fine adjustments. As a result, there is a limit to further improving the fine operability and combined operability of hydraulic excavators, which are required with the construction of urban construction machinery in the future.

Further, in the latter directional switching valve drive hydraulic circuit, when this is applied to turning, it cannot be applied at the time of starting and accelerating the upper revolving structure, and further deceleration and turning.
Even at the time of stop, there is a drawback that the neutral return characteristic of the switching valve can be adjusted only by one predetermined characteristic. Further, when the electric signal to the flow rate / pressure adjusting means is interrupted due to a failure or the like, there is a problem in ensuring the safety of operation.

Therefore, an object of the present invention is to respond the change speed of the spool of the switching valve for controlling the swing actuator to the change of the moment of inertia of the upper swing body in the process of returning to the neutral position after the actuator is operated. It is an object of the present invention to provide a hydraulic drive system for a hydraulic excavator that can overcome the above-mentioned problems and can significantly improve the feeling when the revolving structure is stopped as compared with the conventional method by performing the adjustment.

[0012]

In order to achieve the above-mentioned object, a hydraulic drive system for a hydraulic excavator according to the present invention includes an arm, a boom, a bucket, a swing, a run, and other structural parts of the hydraulic excavator in each structural part. Driven by the attached hydraulic actuators, each switching actuator is provided with each switching valve to supply the pressure oil of the hydraulic pump and to discharge the return oil from the hydraulic actuator to the tank.
A hydraulic drive system for a hydraulic excavator configured to control the operation of the switching valve by a hydraulic pilot pressure from a pilot valve, wherein the hydraulic operating unit of the pilot valve (26) and the switching valve (14) of at least one actuator. And a pilot pump (36) for supplying pressure oil to the pilot valve, and an opening degree of the flow rate / pressure adjusting means. A control unit (96) for generating an electric signal for receiving the pressure oil from the pilot pump (36), and in response to the electric signal from the control unit (96), the flow rate / pressure adjusting means ( 34A) to generate a pressure oil signal for adjusting the opening degree, and
An electromagnetic proportional pressure reducing valve (3 supplied to the pressure adjusting means (34A))
8) and the flow rate / pressure adjusting means (3
4) is configured as a variable pressure reducing valve that reduces the secondary pressure in response to an increase in the pressure oil signal given from the electromagnetic proportional pressure reducing valve (38). In that case, the variable pressure reducing valve constituting the flow rate / pressure adjusting means (34A) forms an opening connected to the hydraulic operation section (14A) of the switching valve (14) at one end side, and the inside of the variable pressure reducing valve. A first hole (54) following the opening and a second stepped hole (58) that is formed in the axial direction of the first hole (54) and is larger in diameter than the first hole (54). , 60) forming a valve body (5
0), the first hole (54) and the second stepped hole (5)
A first spool (52) and a second spool (56) slidably disposed on the first and second spools, respectively.
Is located between the first spool (52) and the second spool (56) in the hole (54) of the first spool (5).
2) a first spring (62) for biasing the second spool (56) in the second stepped hole (58, 60)
And a second spring (which is disposed between the valve body (50) and the other end of the valve body (50) and has a larger elastic force than the first spring (62) and urges the second spool (56). 64), and the first spring (62) is disposed in the first spool (52) through a diaphragm (66) formed at one end side thereof to communicate with the opening and at the other end side thereof. A passage communicating with the oil chamber (76) is formed, and the passage is formed in the valve body (50).
Is formed so as to communicate with the lateral hole (71) that receives pilot pressure from the pilot valve (26), and the second spool (56) has the oil chamber (76) and the second spool (56). A passage communicating with the oil chamber (78) in which the spring (64) is arranged is formed, and the oil chamber (7) is provided between the step portion of the valve body (50) and the outer peripheral portion of the spool.
2) is formed, and the oil chamber (72) has a valve body (5).
0) through the lateral hole formed in the electromagnetic proportional pressure reducing valve (3
8) may be configured to receive the pressure oil signal provided by 8). Further, in that case, the variable pressure reducing valve constituting the flow rate / pressure adjusting means can be configured integrally with the hydraulic pressure operation unit (14A) of the switching valve (14). Furthermore, the variable pressure reducing valve that constitutes the flow rate / pressure adjusting means (34A ') stores the end of the spool (84) of the hydraulic operating portion (14A) of the switching valve (14) in a liquid-tight manner on one end side. Forming a concave portion and an opening communicating with the concave portion, and forming a first hole inside the concave portion and a first hole formed in the axial direction of the first hole following the first hole. A valve body (50 ') having a second stepped hole (58, 60) having a diameter larger than that of the hole and the first hole (54) and the second stepped hole (58, 60) are slid respectively. A first spool (52) and a second spool (56) movably arranged, and between the first spool (52) and the second spool (56) in the first hole (54). A first spring (62) disposed and biasing the first spool (52), and the second stepped hole (58, Said at 0) the second spool (5
6) and the other end side of the valve body (50 '), which has a larger elastic force than the first spring (62) and urges the second spool (56). Springs (64)
And an oil chamber in which the first spring (62) is arranged in the first spool (52) through a throttle (66) having one end communicating with the opening and formed at the other end. (76)
Is formed in the valve body (50 ') and communicates with a lateral hole (71) that receives pilot pressure from the pilot valve (26). The spool (56) has
A passage communicating between the oil chamber (76) and the oil chamber (78) in which the second spring (64) is arranged is formed, and the stepped portion of the valve body (50 ') and the spool outer peripheral portion are formed. An oil chamber (72) is formed therebetween, and the oil chamber (72) receives a pressure oil signal given from the electromagnetic proportional pressure reducing valve (38) through a lateral hole formed in the valve body (50 '). Can be configured. Furthermore, in that case, a detection signal corresponding to the pilot pressure from the pilot valve (26) and the operating state of the hydraulic actuator operated by the pilot pressure is input to the control unit (96). And configured to generate the electrical signal based on the detection signal.

In this case, the hydraulic actuator provided with the flow rate / pressure adjusting means may be composed of a swing motor.

Also, the external signal may be a signal associated with the angle of the boom with respect to the upper swing structure.

Alternatively, the external signal may be a signal associated with the load pressure on the holding side of the boom cylinder.

Furthermore, the flow rate provided in the pilot oil passage
The pressure adjusting means can be composed of a flow rate adjusting valve with pressure compensation in which the amount of oil passing through decreases in response to an increase in an external signal.

Further, the flow rate / pressure adjusting means provided in the pilot oil passage may be constituted by a variable pressure reducing valve whose secondary pressure decreases in response to an increase in an external signal.

Further, the flow rate / pressure adjusting means provided in the pilot oil passage reduces the pressure oil flow from the pilot valve to the switching valve, and controls the pressure compensating flow rate of the oil discharged from the switching valve to the pilot valve. It can also be configured as follows.

The flow rate / pressure adjusting means can be integrated with the hydraulic operating portion of the switching valve.

Further, the flow rate / pressure adjusting means may be constituted by an electromagnetic pressure reducing valve whose output secondary pressure decreases as the input current increases.

[0021]

Embodiments of the hydraulic drive system for a hydraulic excavator according to the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a hydraulic circuit diagram showing an embodiment of a hydraulic drive system for a hydraulic excavator according to the present invention. However, in FIG. 1, reference numeral 10 indicates a part of a control valve for operating the hydraulic excavator. In the control valve 10, a turning switching valve 14 for operating the turning motor 12, an arm switching valve 16 and the like are incorporated.

For the control valve 10,
A hydraulic pump 18 is connected to each of the switching valves 14,
When 16 is in the neutral position, the pressure oil discharged from the hydraulic pump 18 to the pressure oil supply passage 20 is transferred to the switching valves 14 and 16 respectively.
It is discharged to the tank 22 through the center bypass passage 21 and the discharge oil passage 23. Further, the pressure oil supply passage 20 and the discharge oil passage 23 are connected to each other by a bypass passage 25 having a relief valve 24.

Further, the turning switching valve 14 has hydraulic operating portions 14A and 14B at both ends thereof.
For A and 14B, the operation signal pressure from the hydraulic pilot valve 26 is introduced through signal passages 27 and 31, 28 and 32, respectively. The signal pressure from the pilot valve (not shown) is also introduced to the hydraulic pressure operation section for each switching valve other than the turning.

However, flow rate / pressure adjusting means 34A, 34B are provided on the operation signal line of the turning switching valve 14, and the flow rate / pressure adjusting means 34A, 34B are further provided.
Is a valve that appropriately converts a required electric signal into a required hydraulic signal based on pilot pressure oil from the pilot hydraulic pump 36, for example, a signal pressure obtained by an electric / oil conversion means 38 such as an electromagnetic proportional pressure reducing valve. The opening is adjusted.

The pilot pressure oil from the pilot hydraulic pump 36 is supplied to the hydraulic pilot valve 26 via the pilot pressure oil supply passage 29, and the discharge oil is appropriately discharged from the tank 22 via the discharge oil passage 30. It is configured to be discharged to.

Further, the turning means 40 equipped with the turning motor 12 has check valves 41, 41 and a relief valve 42, respectively in the hydraulic circuits connected to the turning switching valve 14.
And 42 are provided. Furthermore, the arm switching valve 16
An arm cylinder 44 is connected to the load circuit of.

FIG. 2 shows an embodiment of the flow rate / pressure adjusting means 34A. In FIG. 2, reference numeral 5
Reference numeral 0 denotes a valve body, in which the first spool 52 is provided for the hole 54 and the second spool 56 is provided.
Are slidably and liquid-tightly incorporated in the stepped holes formed by the holes 58 and 60, respectively.
Further, a first spring 62 is provided between the spools 52 and 56, and a second spring 64 is provided at the other end of the second spool 56 via the second spool 56. It is provided so as to face the first spring 62.

The load of the second spring 64 is set sufficiently larger than the load of the first spring 62. First
One end of the spool 52 is opened to the signal passage 31 of FIG. 1, while the other end is connected to the tank line 68 via a throttle 66 provided in the first spool 52.
Then, the groove 70 provided on the outer peripheral portion of the first spool 52 and the groove 70 and the signal passage 31 are connected to each other by the first spool 5
2 is connected through a passage provided inside. This allows
Signal passage 27 derived from the hydraulic pilot valve 26
And the signal passage 31 communicating with the hydraulic operating portion 14A of the turning switching valve 14 are connected to each other.

The secondary pressure from the electromagnetic proportional pressure reducing valve 38 is supplied to the oil chamber 72 formed by the stepped portion of the second spool 56 and the stepped hole of the valve body 50. . The pressure oil from the pilot hydraulic pump 36 is
The hydraulic pilot valve 26 and the electromagnetic proportional pressure-reducing valve 38 are respectively supplied with the original pressure, and the secondary pressure of the pilot valve 26 and the electromagnetic proportional pressure-reducing valve 38 is
Outputs having the characteristics shown in FIGS. 3 and 4 are obtained.
Further, oil chambers 74, 76, 78 are formed in front of and behind the first spool 52 and the second spool 56, respectively.

Next, the operation of the hydraulic drive system for the hydraulic excavator having the above-described structure according to this embodiment will be described.

In FIG. 1, when the hydraulic pilot valve 26 is first operated, the secondary (pilot) pressure shown in FIG. 3 is output to the signal passages 27 and 28 thereof. Therefore, for example, when the pilot pressure is output to the signal passage 27, the pilot pressure is introduced into the hydraulic pressure operation portion 14A of the turning switching valve 14 via the flow rate adjusting means 34A and the signal passage 31.

FIG. 5 shows an example of the construction of the hydraulic operating section 14A. That is, in FIG. 5, the signal path 3
The pilot signal pressure oil that has flowed into the oil chamber 80 of the hydraulic operating unit 14A from the first position resists the elastic force of the spring 82 and thus the spool 84.
Can be moved to the right within the range of the required stroke S.

At this time, when the signal pressure is not applied to the oil chamber 72 shown in FIG. 2 as an external signal to the flow rate / pressure adjusting means 34A having the structure shown in FIG. Sufficiently compresses the first spring 62 through the spool 56 of the first spring 62,
The spool 52 is pressed to the left in the figure. Also,
In this state, the elastic force of the first spring 62 is set sufficiently large so that the first spool 52 does not move to the right in the drawing depending on the pressure difference between the pressure in the oil chamber 74 and the pressure in the oil chamber 76. Therefore, the groove 70 of the first spool 52 and the lateral hole 71 formed in the valve body 50 are sufficiently open to each other, whereby the pressure oil from the signal passage 27 is discharged by the flow rate / pressure adjusting means 34A. Is transmitted to the signal path 31 without any action.

Also, in the process of returning the hydraulic pilot valve 26 to the neutral state after the hydraulic pilot valve 26 is operated toward one end,
Similarly to the above, the pressure oil in the hydraulic pressure operation portion 14A of the swing switching valve 14 is discharged from the signal passage 31 to the signal passage 27 without being affected by the flow rate / pressure adjusting means 34A.

Here, in a state in which the hydraulic pilot valve 26 is operated to activate and accelerate the upper swing body, in FIG. 2, an external (electromagnetic proportional pressure reducing valve 3
When a predetermined signal pressure is applied from 8), this signal pressure acts on the second spool 56 to compress the second spring 64 and move it to the right in the figure by a predetermined amount. As a result, the load of the first spring 62 acting on the first spool 52 is reduced, and the pressure oil in the oil chamber 74 is transferred to the first spool 5
The first spool 52 is moved to the right in the figure by the load reduction amount of the first spring 62 with respect to 2.

Therefore, the left end of the groove 70 of the first spool 52 closes a part of the lateral hole 71 and reduces the opening degree of the lateral hole 71. Therefore, the pressure in the oil chamber 74 is determined by the inflow amount from the lateral hole 71 whose opening is limited and the discharge amount from the throttle 66 provided in the first spool 52.
The pressure in 4 is a pressure that balances the elasticity of the first spring 62. In the range lower than the pressure of the signal passage 27, this pressure is the first pressure regardless of the pressure of the signal passage 27.
Is adjusted by the load of the spring 62, that is, a predetermined signal pressure from the outside to the oil chamber 72.

Therefore, when activating and accelerating the upper swing body, if appropriate signal pressure corresponding to the change in the moment of inertia of the upper swing body is applied to the flow rate / pressure adjusting means 34A, switching as shown in FIG. Since the acceleration from the neutral position N of the valve 14 'to the intermediate position M between the stroke ends E can be adjusted respectively, the hydraulic pilot valve 2
Even when 6 is suddenly operated, it is possible to achieve the turning start / acceleration operation with extremely excellent operability.

On the other hand, when the swing hydraulic pilot valve 26 is operated to drive the upper swing body and then the pilot valve 26 is returned to the neutral state in order to stop the same, the flow rate / pressure adjusting means 34A is the same as above. When a signal pressure is applied to the oil, the oil that is about to return from the hydraulic pressure operation portion 14A of the turning switching valve 14 to the signal passage 27 through the signal passage 31 passes through the flow rate / pressure adjusting means 34A and is then stored in the oil chamber. 74
As described above, since the load of the first spring 62 on the first spool 52 is relatively small as described above, the oil in the oil chamber 74 becomes Since the spool 52 of No. 1 is moved rightward and the left end of the groove 70 limits the opening to the lateral hole 71, discharge of the return oil from the signal passage 31 to the signal passage 27 is limited. Therefore, even if the pilot valve 26 is suddenly returned or the moment of inertia of the upper swing body changes depending on the position of the boom and the load condition of the bucket, pressure signals corresponding to the respective conditions are supplied to the flow rate / pressure adjusting means. By giving the hydraulic drive unit 34A, it is possible to obtain a hydraulic drive system having extremely excellent deceleration characteristics.

In the above embodiments, the case where both the start / acceleration and the deceleration / stop of the upper revolving superstructure are applied has been described. However, in actually applying the hydraulic drive system for the hydraulic excavator according to the present invention, Of course, this can be applied only to the operation of deceleration / stop depending on the situation.

Further, in the hydraulic drive system of this embodiment, an electromagnetic proportional pressure reducing valve 38 is provided in order to give a signal to the flow rate / pressure adjusting means 34A, 34B. However, as shown in FIGS. 7A and 7B, the electromagnetic proportional pressure reducing valve 38 is displaced at the mounting portion 92a of the boom 92 mounted on the revolving structure 91 of the hydraulic excavator 90. The boom angle θ is detected by the angle sensor 94, or the load pressure (Ph) on the holding side 93a of the boom cylinder 93 is detected by the pressure sensor 95, and these detection signals are transmitted to the control unit 96. Therefore, the control unit 96 further selects a predetermined target value S1 and the output signal pressure of the hydraulic pilot valve 26 with the high pressure selection valve 46, and the signal detected by the pressure sensor 48 (see FIG. 1) and other information. Signal Sn is input, calculation is performed, and the obtained result is output as a supply current i for instructing the electromagnetic proportional pressure reducing valve 38. Then, in the electromagnetic proportional pressure reducing valve 38, the secondary pressure output according to the characteristic shown in FIG. 4 is transmitted to the flow rate / pressure adjusting means 34A, 34B, and the hydraulic pilot valve 26 of the switching valve 14 is transmitted as described above. It is possible to control the pressure increase characteristic of the operation signal pressure to the hydraulic pressure operation units 14A and 14B and to control the amount of return oil discharged from the hydraulic pressure operation units 14A and 14B.

Therefore, in this case, the supply current i to the electromagnetic proportional pressure reducing valve 38 with respect to the secondary pressure (Pp) of the hydraulic pilot valve 26 is set by the control unit 96 so as to have the characteristic shown in FIG. Even if the electric signal is interrupted due to a failure or the like, the flow rate / pressure adjusting means 34
Since A and 34B can always maintain the state in which the output signal of the hydraulic pilot valve 26 is transmitted to the hydraulic operating portions 14A and 14B of the switching valve 14, it is also effective in ensuring safety.

In FIG. 7A, reference numeral 9
Reference numeral 8 is an arm, 99 is an arm cylinder, 100 is a bucket, and 101 is a bucket cylinder.

Further, in the hydraulic drive system of this embodiment, the flow rate / pressure adjusting means 34A and 34B are, for example, as shown in FIG.
As shown in FIG.
A very compact structure can be achieved by integrating with. That is, in FIG. 9, in the composite means 34A 'of one flow rate / pressure adjusting means and the corresponding hydraulic operating portion of the switching valve, the right side of the figure shows the flow rate / pressure adjusting means, and the left side of the figure shows The hydraulic operation part is shown. The flow rate / pressure adjusting means has the same structure as that of the flow rate / pressure adjusting means 34A shown in FIG. 2, and the same components are designated by the same reference numerals and detailed description thereof will be omitted. . On the other hand, the hydraulic operating section has the same basic configuration as the hydraulic operating section 14A shown in FIG. 5 described above, but in this embodiment, the oil chambers 74 of the adjacent flow rate / pressure adjusting means are arranged. The pilot signal pressure oil flowing into the oil chamber 80 ′ communicating with the spring 82 is communicated with the spring 82.
The spool 84 is configured to move to the left against the elasticity of the.

Furthermore, in the hydraulic drive system of this embodiment, as the flow rate / pressure adjusting means 34A and 34B, the electromagnetic pressure reducing valve 102 having the structure shown in FIG. 10 is used instead of the embodiment shown in FIG. can do. That is, in FIG. 10, the electromagnetic pressure reducing valve 102 basically has a spool 106 slidably mounted in a housing 104, and one end of the spool 106 is used for adjusting a secondary pressure. The signal pressure to the signal passage 31 is set at the balance position of the spool 106 by applying the adjusting pressure Fvs of the spring 108 and the acting force Fvp of the signal pressure to the signal passage 31 on the other end side. Is configured to.

Further, a large diameter flange portion 106a is formed on one end side of the spool 106 where the secondary pressure adjusting spring 108 is provided, and a piston 110 extending parallel to the spool 106 is formed on the flange portion 106a. The pressure receiving portion at the other end of the piston 110 is formed as a secondary pressure chamber 112 communicating with the signal passage 31 while protruding.

In this case, when the signal pressure from the signal passage 27 is applied while the spool 106 is moving to the position shown in the figure by the adjusting pressure Fvs of the spring 108,
This signal pressure is guided to the secondary pressure chamber 112 from the passages 114a and 114b, outputs a predetermined signal pressure to the signal passage 31, and opposes the pressure adjustment Fvs of the spring 108 in the secondary pressure chamber 112. The acting force Fvp is generated. The passage 114c is an exhaust oil passage that communicates with the tank 22. Further, in the above structure, the proportional solenoid 116 for generating the thrust Fm opposite to the pressure adjusting spring force Fvs is provided at the end of the spool 106 on the side where the secondary pressure p acts (on the right side in the drawing).

According to the electromagnetic pressure reducing valve 102 thus constructed, the secondary pressure p transmitted from the signal passage 27 to the signal passage 31 from the signal passage 27a to the signal passage 31 is the secondary pressure p. In the pressure chamber 112, an acting force Fvp that opposes the regulating pressure Fvs of the spring 108 is generated and reduced according to the cross-sectional area of the secondary pressure chamber 112, and the drive current of the proportional solenoid 116 is increased. As the thrust force Fm is increased, the spool 106 is moved to the left in the drawing to increase the adjusting pressure Fvs of the spring 108, whereby the acting force Fvp generated in the secondary pressure chamber 112 is further reduced. Therefore, the signal pressure output to the signal passage 31 can be gradually reduced.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and many design changes can be made without departing from the spirit thereof. For example, in the above-described embodiment, the swing single operation of the hydraulic excavator has been described, but other than this, for example, in the simultaneous operation of the boom and the bucket cylinder, if the device of the present invention is applied to the bucket cylinder operation switching valve, Since the operating pressure supplied from the pilot valve to the hydraulic operating part of the switching valve can be adjusted to a predetermined value or less, even when the boom and bucket operating pilot valves are fully operated, the bucket cylinder operating switching valve The spool is held in the intermediate position shown in FIG.
Therefore, since the supply of the pressure oil to the bucket cylinder is limited, both the boom cylinder and the bucket cylinder can be operated simultaneously. Further, in this case, the boom operating pilot pressure can be used as the external signal applied to the flow rate / pressure adjusting means provided on the bucket operating pilot line.

[0050]

As described above, the hydraulic drive system for a hydraulic excavator according to the present invention is a hydraulic actuator in which the arm, boom, bucket, turning, traveling, and other structural parts of the hydraulic excavator are attached to each structural part. Each of these hydraulic actuators is provided with a switching valve to supply the pressure oil of the hydraulic pump, and the return oil from the hydraulic actuator is discharged to the tank.The switching valve is operated from the pilot valve. A hydraulic drive device for a hydraulic excavator configured to be controlled by a hydraulic pilot pressure, wherein a pilot valve (2
6) and a flow rate / pressure adjusting means (34A) arranged in a pilot oil passage between the switching valve (14) and a hydraulic operation portion of the switching valve (14),
A pilot pump (36) for supplying pressure oil to the pilot valve, a control section (96) for generating an electric signal for adjusting the opening of the flow rate / pressure adjusting means, and a pressure from the pilot pump (36). While receiving the supply of oil, a pressure oil signal for adjusting the opening of the flow rate / pressure adjusting means (34A) is generated in response to an electric signal from the control section (96), and the pressure oil signal is generated. Adjusting means (34
A proportional pressure reducing valve (38) for supplying the secondary pressure to the flow rate / pressure adjusting means (34) in response to an increase in a pressure oil signal given from the proportional proportional pressure reducing valve (38). As it is configured as a variable pressure reducing valve that can be lowered, it has excellent operability regardless of changes in the moment of inertia of the upper revolving structure of the hydraulic excavator, and in spite of sudden operation of the pilot valve during acceleration or deceleration. Even when the supply current i to the proportional pressure reducing valve (38) is cut off due to a failure or the like, the flow rate / pressure adjusting means can maintain the state in which the output signal of the hydraulic pilot valve is always transmitted to the hydraulic operating portion of the switching valve. Therefore, it is possible to obtain a hydraulic drive device for a hydraulic excavator that is effective in ensuring safety.

That is, according to the hydraulic drive system of the present invention, in the process in which the spool of the switching valve for controlling the swing actuator returns to the neutral position after the actuator is operated, the return speed is set to the inertia moment of the upper swing body. By adjusting according to the change, it is possible to significantly improve the feeling when the revolving structure is stopped as compared with the conventional method.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of a hydraulic drive system for a hydraulic excavator according to the present invention.

FIG. 2 is a schematic configuration diagram showing an embodiment of flow rate / pressure adjusting means in the hydraulic drive system shown in FIG.

3 is a characteristic diagram of a hydraulic pilot valve in the hydraulic drive system shown in FIG.

4 is a characteristic diagram of an electromagnetic proportional pressure reducing valve in the hydraulic drive system shown in FIG.

5 is a schematic configuration diagram showing an embodiment of a hydraulic operating portion of a switching valve in the hydraulic drive system shown in FIG.

FIG. 6 is an explanatory diagram showing a neutral position, a stroke end, and an intermediate position of the switching valve applicable to the hydraulic drive system according to the present invention.

FIG. 7 shows an example of application of the hydraulic drive system shown in FIG. 1 to a hydraulic excavator, in which (a) is detection of a boom angle in a hydraulic excavator, pressure detection on a holding side of a boom cylinder, and control means. It is explanatory drawing which shows an input-output relationship, (b) is a principal part enlarged view in the Y part of (a).

8 is an explanatory diagram showing a setting example of a secondary pressure of a hydraulic pilot valve and an output current characteristic to an electromagnetic proportional pressure reducing valve in the hydraulic drive system shown in FIG.

FIG. 9 is a schematic configuration diagram showing an embodiment of combined means in which the flow rate / pressure adjusting means and the hydraulic operating portion of the switching valve, which are applied to the hydraulic drive system according to the present invention, are integrated.

FIG. 10 is a flow rate applied to the hydraulic drive system according to the present invention.
It is a schematic block diagram which shows the Example of the electromagnetic pressure reducing valve which can be used as a pressure adjusting means.

[Explanation of symbols]

10 Control Valve 12 Swing Motor 14 Swing Switching Valves 14A, 14B Hydraulic Operation Section 14 'Switching Valve 16 Arm Switching Valve 18 Hydraulic Pump 20 Pressure Oil Supply Passage 21 Center Bypass Passage 22 Tank 23 Discharge Oil Passage 24 Relief Valve 25 Bypass Passage 26 hydraulic pilot valve 27, 28, 31, 32 signal passage 29 pilot pressure oil supply passage 30 discharge oil passage 34A, 34B flow rate / pressure adjusting means 34A 'combined means of flow rate / pressure adjusting means and hydraulic operating section 36 pilot hydraulic pump 38 Electric / oil conversion means (electromagnetic proportional pressure reducing valve) 40 Swirling means 41 Check valve 42 Relief valve 44 Arm cylinder 46 High pressure selection valve 48 Pressure sensor 50, 50 'Valve body 52 First spool 54 Hole 56 Second spool 58 , 60 hole 62 first spring 64 second spring 66 diaphragm 68 Tank line 70 Groove 71 Horizontal hole 72 Oil chamber 74, 76, 78 Oil chamber 75 Communication means 80, 80 'Oil chamber 82 Spring 84 Spool 90 Hydraulic excavator 91 Revolving body 92 Boom 92a Attachment portion 93 Boom cylinder 93a Holding side 94 Angle sensor 95 pressure sensor 96 control unit 98 arm 99 arm cylinder 100 bucket 101 bucket cylinder 102 electromagnetic pressure reducing valve 104 housing 106 spool 108 secondary pressure adjusting spring 110 piston 112 secondary pressure chambers 114a, 114b passage 114c discharge oil passage 116 proportional solenoid

Claims (5)

(57) [Claims] 1. An arm, boom, bucket, turning, traveling, and other structural parts of a hydraulic excavator are driven by hydraulic actuators attached to the respective structural parts, and these hydraulic actuators are provided with respective switching valves to provide a hydraulic pump. Is a hydraulic drive device for a hydraulic excavator, which is configured to supply the pressure oil from the hydraulic actuator and discharge the return oil from the hydraulic actuator to the tank, and to control the operation of the switching valve by the hydraulic pilot pressure from the pilot valve. And a flow rate / pressure adjusting means (34A) arranged in a pilot oil passage between the pilot valve (26) of at least one actuator and the hydraulic operating portion of the switching valve (14).
A pilot pump (36) for supplying pressure oil to the pilot valve, a control unit (96) for generating an electric signal for adjusting the opening of the flow rate / pressure adjusting means, and the pilot pump (36) Pressure oil is supplied from the control unit (96), and in response to an electric signal from the control unit (96), a pressure oil signal for adjusting the opening of the flow rate / pressure adjusting means (34A) is generated, and the pressure oil signal is generated. An electromagnetic proportional pressure reducing valve (38) for supplying pressure to the pressure adjusting means (34A), and the flow rate / pressure adjusting means (34) according to an increase in a pressure oil signal given from the electromagnetic proportional pressure reducing valve (38). A hydraulic drive device for a hydraulic excavator, characterized in that it is configured as a variable pressure reducing valve that lowers the secondary pressure. 2. The variable pressure reducing valve constituting the flow rate / pressure adjusting means (34A) has an opening formed at one end side thereof, the opening being connected to the hydraulic operating portion (14A) of the switching valve (14), A first hole (54) following the opening, and a second stepped hole that is formed in the axial direction of the first hole (54) and that is larger than the first hole (54) and that is larger in diameter than the first hole (54). (58, 60) formed valve body (5
0) and the first hole (54) and the second stepped hole (58, 60)
The first spool (5
2) and a second spool (56) and a first spool (52) in the first hole (54)
A first spring (62) disposed between the second spool (56) and the first spool (52) and biasing the second spool in the second stepped hole (58, 60). A second spring disposed between the spool (56) and the other end of the valve body (50) and having a larger elastic force than the first spring (62) and biasing the second spool (56); And a second spring (64), wherein the first spool (52) is provided with a first spring (62) through a diaphragm (66) having one end communicating with the opening and the other end. Is formed in the valve body (50) and communicates with a lateral hole (71) that receives pilot pressure from the pilot valve (26). The second spool (56) has the oil chamber (76) and Said valve body together with the passage communicating between the arranged by the oil chamber (78) the serial second spring (64) is formed (5
0) has an oil chamber (72) formed between the step portion and the outer peripheral portion of the spool. The oil chamber (72) is connected to the electromagnetic proportional pressure reducing valve (38) through a lateral hole formed in the valve body (50). The hydraulic drive system for a hydraulic excavator according to claim 1, wherein the hydraulic drive system is configured to receive a supplied pressure oil signal. 3. The hydraulic excavator according to claim 1, wherein the variable pressure reducing valve forming the flow rate / pressure adjusting means is integrally formed with the hydraulic operating portion (14A) of the switching valve (14). Hydraulic drive. 4. The variable pressure reducing valve constituting the flow rate / pressure adjusting means (34A ') is liquid-tight at one end of a spool (84) end of a hydraulic operating portion (14A) of the switching valve (14). To form a concave portion to be accommodated in the concave portion and an opening communicating with the concave portion, and to internally form a first hole following the opening and a first hole formed in the axial direction of the first hole. A valve body (50 ') having a second stepped hole (58, 60) larger in diameter than the first hole; and the first hole (54) and the second stepped hole (58, 60)
The first spool (5
2) and a second spool (56) and a first spool (52) in the first hole (54)
A first spring (62) disposed between the second spool (56) and the first spool (52) and biasing the second spool in the second stepped hole (58, 60). It is arranged between the spool (56) and the other end of the valve body (50 ') and has a larger elastic force than the first spring (62) and urges the second spool (56). A second spring (64) is provided, and the first spool (52) is provided with a first spring (62) through an aperture (66) having one end communicating with the opening and the other end. Is formed in the valve body (50 ') and communicates with a lateral hole (71) that receives pilot pressure from the pilot valve (26). The second spool (56) is formed in the oil chamber (76). It said valve body together with the passage communicating between the arranged by the oil chamber (78) of said second spring (64) is formed with (5
The oil chamber (72) is formed between the step portion (0 ') and the outer peripheral portion of the spool, and the oil chamber (72) is provided with the solenoid proportional pressure reducing valve (38) through a lateral hole formed in the valve body (50'). 2.) A hydraulic drive system for a hydraulic excavator according to claim 1, wherein the hydraulic drive system is configured to receive a pressure oil signal provided from the hydraulic excavator. 5. The control unit (96) receives a pilot pressure from the pilot valve (26) and a detection signal corresponding to an operating state of the hydraulic actuator operated by the pilot pressure, and these pilot pressures are input. 5. The hydraulic drive system for a hydraulic excavator according to claim 1, wherein the electric signal is generated based on the detection signal.