WO2015056423A1

WO2015056423A1 - Hydraulic drive system

Info

Publication number: WO2015056423A1
Application number: PCT/JP2014/005093
Authority: WO
Inventors: 哲弘近藤; 拓也福本; 英泰村岡
Original assignee: 川崎重工業株式会社
Priority date: 2013-10-15
Filing date: 2014-10-07
Publication date: 2015-04-23
Also published as: GB2534518A; JP2015078713A; CN105637228A; JP6088396B2

Abstract

A hydraulic drive system (1A) having first and second multi-control valves (4A, 4B) connected to first and second hydraulic pumps (21, 22). A first regulator (3A) adjusts the tilt angle of the first hydraulic pump (21) such that the discharge flow rate of the first hydraulic pump (21) reduces the higher the discharge pressure of the first hydraulic pump (21) and the power shift pressure. A second regulator (3B) adjusts the tilt angle of the second hydraulic pump (22) such that the discharge flow rate of the second hydraulic pump (22) reduces the higher the discharge pressure of the second hydraulic pump (22) and the first hydraulic pump (21) and the higher the power shift pressure. The power shift pressure is set by a proportional valve (72).

Description

Hydraulic drive system

The present invention relates to a hydraulic drive system for a construction machine having a swing hydraulic motor.

In a construction machine such as a hydraulic excavator, hydraulic fluid is generally supplied from a hydraulic pump driven by an engine to various hydraulic actuators. As the hydraulic pump, a variable displacement pump such as a swash plate pump or a swash shaft pump is used, and the flow rate of hydraulic oil discharged from the hydraulic pump is changed by changing the tilt angle of the hydraulic pump. .

¡The tilt angle of the hydraulic pump is generally adjusted by a regulator. For example, Patent Literature 1 discloses a hydraulic drive system that includes two hydraulic pumps driven by one engine and two regulators that adjust the tilt angles of the hydraulic pumps. In this hydraulic drive system, in order to prevent the engine from being stopped due to overload, horsepower control is performed so that the total horsepower of the individual hydraulic pumps does not exceed the output of the engine.

Specifically, in Patent Document 1, the discharge pressure of the self-side hydraulic pump connected to the regulator and the discharge pressure of the counterpart hydraulic pump connected to the other regulator are led to each regulator. The regulator increases the tilt angle of the self-side hydraulic pump and increases the discharge flow rate of the self-side hydraulic pump as the discharge pressure of the self-side hydraulic pump and the counterpart hydraulic pump increases. That is, the tilt angles of the two hydraulic pumps are always kept at the same angle. In addition, the control pressure is guided to the both regulators from the proportional valve, and the tilt angle of both hydraulic pumps is increased as the control pressure is higher. In this technical field, horsepower control based on the discharge pressures of the self-side hydraulic pump and the counterpart hydraulic pump is sometimes referred to as total horsepower control, and horsepower control based on the control pressure is sometimes referred to as power shift control.

More specifically, each regulator includes a servo cylinder connected to the self-side hydraulic pump, a spool for controlling the servo cylinder, and the self-side hydraulic pump and the counterpart hydraulic pump having higher discharge pressure and control pressure. It includes a horsepower control piston that presses the spool in a direction that increases the discharge flow rate of the hydraulic pump.

The hydraulic drive system disclosed in Patent Document 1 is intended for a hydraulic excavator, and hydraulic oil is supplied from one hydraulic pump to a swing hydraulic motor or the like via a control valve, and from the other hydraulic pump. The hydraulic oil is supplied to the bucket cylinder and the like through the control valve.

JP-A-11-101183

Incidentally, in the hydraulic drive system disclosed in Patent Document 1, it is conceivable to reverse the direction in which the horsepower control piston of the regulator presses the spool. In other words, each regulator is configured to decrease the discharge flow rate of the self-side hydraulic pump as the discharge pressure and control pressure of the self-side hydraulic pump and the counterpart hydraulic pump increase. In this way, when one hydraulic pump is unloaded, there is an advantage that the discharge flow rate of the other hydraulic pump can be increased. For example, in FIG. 9A, the performance characteristics of one hydraulic pump are shown by a solid line A when the same load is applied to the hydraulic pump and the other hydraulic pump, and the one-dot chain line B shows the case where the other hydraulic pump is unloaded. Show. The above merits are effective, for example, in the case of single bucket operation.

However, in the case of a single turning operation, the discharge flow rate increased by the above-mentioned merit becomes excessive at the initial stage of the turning body turned by the turning hydraulic motor. This is because in construction machines, the weight of the revolving structure (strictly speaking, inertia) is large, so that a large flow rate is not necessary at the initial stage of the acceleration of the revolving. Excess hydraulic oil supplied to the swing hydraulic motor at the time of swing acceleration is released from the relief valve of the swing hydraulic motor. Thus, in the case of a single turn operation, energy is wasted when turning acceleration.

Therefore, an object of the present invention is to provide a hydraulic drive system capable of suppressing wasteful consumption of energy during turning acceleration.

In order to solve the above-mentioned problems, a hydraulic drive system according to the present invention is a hydraulic drive system for a construction machine having a swing hydraulic motor, and is driven by an engine to discharge hydraulic oil at a flow rate corresponding to a tilt angle. The first hydraulic pump and the second hydraulic pump, the first multi-control valve connected to the first hydraulic pump and including a swing spool for controlling the swing hydraulic motor, and the second hydraulic pump In accordance with the discharge pressure and power shift pressure of the second multi-control valve and the first hydraulic pump, the tilt angle of the first hydraulic pump is such that the discharge flow rate of the first pump decreases as they increase. According to the first regulator for adjusting the discharge pressure, the discharge pressure of the second hydraulic pump and the first hydraulic pump, and the power shift pressure. The second regulator that adjusts the tilt angle of the second hydraulic pump so that the discharge flow rate of the second pump decreases, and the power shift pressure that is guided to the first regulator and the second regulator is set. And a proportional valve.

According to the above configuration, the discharge flow rate of the first hydraulic pump does not depend on the discharge pressure of the second hydraulic pump and does not change depending on the load state of the second hydraulic pump. Accordingly, the discharge flow rate of the first hydraulic pump does not become excessive during the turning operation, and wasteful consumption of energy during turning acceleration can be suppressed. Moreover, since the discharge flow rate of the second hydraulic pump depends on the discharge pressure of the first hydraulic pump as in the prior art, the discharge flow rate can be increased on the second hydraulic pump side when the first hydraulic pump is unloaded. .

In the hydraulic drive system described above, when only the turning spool is operated, or the turning spool is operated, and one or more spools included in the second multi-control valve are in a direction where the required flow rate is small. The system may further include a controller that controls the proportional valve so that when operated, the power shift pressure increases and the discharge flow rates of the first hydraulic pump and the second hydraulic pump decrease. According to this configuration, wasteful consumption of energy during turning acceleration can be effectively suppressed during a turning operation alone or a similar operation.

The hydraulic drive system includes a spool operation detection line extending across the first multi-control valve and the second multi-control valve so as to pass through the monitoring spool including the turning spool, and the spool operation detection line. A pressure detector for monitoring for detecting the shut-off, and a pressure detector for turning for detecting that a pilot pressure of a pilot circuit for operating the turning spool has been established. The spool may be configured not to block the spool operation detection line even when it is operated. According to this configuration, the turning single operation can be detected with a simple configuration.

Alternatively, the hydraulic drive system includes a spool operation detection line extending over the first multi-control valve and the second multi-control valve so as to pass through a monitoring spool including the turning spool, and the turning spool. The pilot pressure is detected in any one of the turning pressure detector for detecting that the pilot pressure of the pilot circuit for operating the pressure is raised and the pilot circuit for operating the monitoring spool other than the turning spool. And a non-turning pressure detector for detecting, wherein the turning spool may be configured to shut off the spool operation detection line when operated. According to this configuration, it is possible to detect a single turning operation using a turning spool having a normal structure.

The construction machine is a hydraulic excavator including a bucket, an arm, and a boom. The second multi-control valve includes a bucket spool and a boom spool as the monitoring spool, and the bucket spool is a bucket-out spool. The spool operation detection line is configured not to be interrupted even when operated in the direction, and the boom spool is configured not to interrupt the spool operation detection line even when operated in the boom lowering direction. The hydraulic drive system includes a bucket-out pressure detector for detecting that a pilot pressure in a bucket-out line in the pilot circuit that operates the bucket spool is raised, and a pilot that operates the boom spool. Boom lowering circuit A boom-lowering pressure detector for detecting the pilot pressure of the emissions stood, it may further comprise a. According to this configuration, it is possible to detect not only a turning operation but also a bucket-out operation and a boom lowering operation with a small required flow rate. As a result, wasteful energy consumption during turning acceleration is effective for simultaneous operations such as simultaneous turning and boom lowering, simultaneous turning and bucket out, and simultaneous turning and boom lowering and bucket out operations. Can be suppressed.

The construction machine is a hydraulic excavator including a bucket, an arm, and a boom, and the hydraulic drive system includes the first multi-control valve and the second multi-control so as to pass through a monitoring spool including the turning spool. A spool operation detection line extending across the valve may be further provided. Further, either the first multi-control valve or the second multi-control valve includes an arm spool as the monitoring spool, and the second multi-control valve includes a bucket spool as the monitoring spool. A boom spool, wherein the swing spool, the arm spool, the bucket spool, and the boom spool are configured to shut off the spool operation detection line when operated, and the swing spool Each of the pilot circuits for operating the arm spool, the bucket spool, and the boom spool may be provided with a pressure detector for detecting that the pilot pressure of the pilot circuit is established. . According to this configuration, a hydraulic drive system incorporated in an existing construction machine can be modified at low cost into the hydraulic drive system of the present invention.

According to the present invention, wasteful consumption of energy during turning acceleration can be suppressed.

1 is an overall hydraulic circuit diagram of a hydraulic drive system according to a first embodiment of the present invention. It is a hydraulic circuit diagram from the 1st and 2nd multi-control valve in a 1st embodiment to a hydraulic actuator. It is a hydraulic-circuit figure for detecting operation other than turning in 2nd Embodiment of this invention. It is a hydraulic circuit diagram from the 1st and 2nd multi control valve in a 2nd embodiment to a hydraulic actuator. FIG. 5 is an overall hydraulic circuit diagram of a hydraulic drive system according to a third embodiment of the present invention. It is a hydraulic circuit diagram from the 1st and 2nd multi-control valve in a 3rd embodiment to a hydraulic actuator. It is a hydraulic circuit diagram for detecting that operations other than turning, boom lowering, and bucket-out in the third embodiment have been performed. It is a whole hydraulic circuit diagram of the hydraulic drive system concerning a 4th embodiment of the present invention. FIG. 9A is a graph showing the performance characteristics of one hydraulic pump in the conventional hydraulic drive system, and FIG. 9B is a graph showing the performance characteristics of the first hydraulic pump in the first embodiment.

(First embodiment)
1 and 2 show a hydraulic drive system 1A according to a first embodiment of the present invention. FIG. 1 is an overall hydraulic circuit diagram of a hydraulic drive system 1A schematically showing the internal configuration of first and second

multi-control valves

4A and 4B, which will be described later. FIG. 2 shows first and second multi-control valves. FIG. 3 is a hydraulic circuit diagram from

valves

4A and 4B to a hydraulic actuator.

The hydraulic drive system 1A is for a construction machine equipped with a swing hydraulic motor. In this embodiment, the construction machine is a hydraulic excavator. However, the construction machine targeted by the hydraulic drive system 1A is not necessarily a hydraulic excavator, and may be a hydraulic crane, for example.

For example, a self-propelled hydraulic excavator includes a traveling device, a main body including a driver's cab that turns with respect to the traveling device, a boom that rises up and down with respect to the main body, an arm that is swingably connected to the tip of the boom, and a tip of the arm And a bucket that is swingably connected to the bucket. That is, the main body, the boom, the arm, and the bucket are revolving bodies that are revolved by a revolving hydraulic motor 24 described later. In a hydraulic excavator mounted on a ship, the main body is supported by the hull so as to be able to turn.

2, the hydraulic drive system 1A includes a swing hydraulic motor 24, a bucket cylinder 25, a boom cylinder 26, and an arm cylinder 27 as hydraulic actuators. Moreover, the hydraulic drive system 1A includes a first hydraulic pump 21 and a second hydraulic pump 22 that supply hydraulic oil to those hydraulic actuators, as shown in FIG. Hydraulic fluid is supplied from the first hydraulic pump 21 to the swing hydraulic motor 24, the boom cylinder 26, and the arm cylinder 27 via the first multi-control valve 4A, and from the second hydraulic pump 22, the second multi-control valve 4B. Hydraulic oil is supplied to the bucket cylinder 25, the boom cylinder 26, and the arm cylinder 27 via.

More specifically, the first hydraulic pump 21 is connected to the first multi-control valve 4A by the first supply line 11. A first center bleed line 12 that guides hydraulic oil that has passed through the first multi-control valve 4A to the tank extends from the first multi-control valve 4A. Similarly, the second hydraulic pump 22 is connected to the second multi-control valve 4B by the second supply line 15. A second center bleed line 16 that guides hydraulic oil that has passed through the second multi-control valve 4B to the tank extends from the second multi-control valve 4B.

In this embodiment, the discharge flow rate of the first hydraulic pump 21 and the discharge flow rate of the second hydraulic pump 22 are controlled by a negative control (hereinafter referred to as “negative control”) method. That is, a throttle 13 is provided in the first center bleed line 12, and a relief valve 14 is disposed on a passage that bypasses the throttle 13. Similarly, a throttle 17 is provided in the second center bleed line 16, and a relief valve 18 is disposed on a passage that bypasses the throttle 17. The

relief valves

14 and 18 and the

throttles

13 and 17 may be incorporated in the first multi-control valve 4A and the second multi-control valve 4B, respectively.

The first multi-control valve 4A and the second multi-control valve 4B are open center type valves including a plurality of spools. That is, in the multi-control valve (4A or 4B), the amount of hydraulic fluid flowing from the supply line (11 or 15) to the center bleed line (12 or 16) is not limited when all the spools are in the neutral position. When that spool is activated and moved from the neutral position, the amount of hydraulic fluid flowing from the supply line (11 or 15) to the center bleed line (12 or 16) is limited by the spool.

More specifically, as shown in FIG. 2, the first multi-control valve 4A includes a swing spool 41 for controlling the swing hydraulic motor 24, and the second multi-control valve 4B controls the bucket cylinder 25. The bucket spool 44 is included. The first multi-control valve 4A and the second multi-control valve 4B include boom spools 42 and 45 for controlling the boom cylinder 26 and arm spools 43 and 46 for controlling the arm cylinder 27, respectively. . The boom spool 45 of the second multi-control valve 4B achieves a first speed, and the boom spool 42 of the first multi-control valve 4A together with the boom spool 45 realizes a second speed higher than the first speed. belongs to. A check valve 47 is disposed on the line from the boom spool 42, which joins the head side line between the boom spool 45 and the boom cylinder 26. The arm spool 44 of the first multi-control valve 4A achieves a first speed, and the arm spool 46 of the second multi-control valve 4B together with the arm spool 44 realizes a second speed higher than the first speed. belongs to.

Further, each of the first multi-control valve 4A and the second multi-control valve 4B has a central passage 4a that connects the supply line (11 or 15) and the center bleed line (12 or 16) across all spools. A parallel passage 4b that guides hydraulic oil from the central passage 4a to each spool and a tank passage 4c that guides hydraulic oil from each spool (excluding the boom spool 42) to the tank are formed.

It should be noted that the positions of the spools 41 to 46 are not particularly limited and need not be as shown in FIG. For example, the bucket spool 44 may be disposed downstream of the boom spool 45 and upstream of the arm spool 46. In the case of a self-propelled hydraulic excavator, each of the first multi-control valve 4A and the second multi-control valve 4B may include a traveling spool for controlling the traveling hydraulic motor. Furthermore, one or a plurality of optional spools may be included in one or both of the first multi-control valve 4A and the second multi-control valve 4B.

The turning pilot circuit 61 for operating the turning spool 41 includes a right turning line 61A and a left turning line 61B extending from the turning operation valve 51 to the turning spool 41, and the bucket pilot circuit 63 for operating the bucket spool 44 includes: A bucket-in line 63A and a bucket-out line 63B extending from the bucket operation valve 53 to the bucket spool 44 are included. The boom pilot circuit 64 that operates the boom spools 42 and 45 includes a boom raising line 64A extending from the boom operation valve 54 to the boom spools 42 and 45, and a boom lowering extending only from the boom operation valve 54 to the boom spool 45. The arm pilot circuit 62 including the working line 64B and operating the arm spools 43 and 46 includes an arm-in line 62A and an arm-out line 62B extending from the arm operation valve 52 to the arm spools 43 and 46. Each operation valve 51 to 54 includes an operation lever. When the operation lever is tilted, pilot pressure is generated in the pilot lines (61A to 64B) in the direction in which the operation lever in the pilot circuit (61 to 64) is tilted, and the spools (41 to 46) are operated.

The first hydraulic pump 21 and the second hydraulic pump 22 are driven by the engine 10 and discharge hydraulic oil at a flow rate corresponding to the tilt angle. In the present embodiment, a swash plate pump whose tilt angle is defined by the angle of the swash plate 20 is employed as the first hydraulic pump 21 and the second hydraulic pump 22. However, the first hydraulic pump 21 and the second hydraulic pump 22 may be a slant shaft pump whose tilt angle is defined by a slant shaft angle.

The tilt angle of the first hydraulic pump 21 is adjusted by the first regulator 3A, and the tilt angle of the second hydraulic pump 22 is adjusted by the second regulator 3B. When the tilt angle of the hydraulic pump (21 or 22) decreases, the discharge flow rate of the hydraulic pump decreases, and when the tilt angle of the hydraulic pump increases, the discharge flow rate of the hydraulic pump increases.

The first regulator 3A includes a servo cylinder 31 connected to the swash plate 20 of the first hydraulic pump 21, a spool 32 for controlling the servo cylinder 31, a negative control piston 33 and a horsepower control piston for operating the spool 32. 34a.

The small diameter side pressure receiving chamber of the servo cylinder 31 communicates with the first supply line 11. The spool 32 controls the opening area of the line connecting the large diameter side pressure receiving chamber of the servo cylinder 31 and the first supply line 11 and also controls the opening area of the line connecting the large diameter side pressure receiving chamber and the tank. . The servo cylinder 31 reduces the tilt angle of the first hydraulic pump 21 when the large diameter side pressure receiving chamber communicates with the first supply line 11 with a larger opening area, and the large diameter side pressure receiving chamber has a larger opening area with the tank. When communicating, the tilt of the first hydraulic pump 21 is increased. The negative control piston 33 and the horsepower control piston 34 a press the spool 32 in a direction in which the large-diameter pressure receiving chamber of the servo cylinder 31 communicates with the first supply line 11, that is, in a direction in which the discharge flow rate of the first hydraulic pump 21 decreases. To do.

The first regulator 3A is formed with a pressure receiving chamber for causing the negative control piston 33 to press the spool 32. A first negative control pressure Pn1, which is a pressure upstream of the throttle 13 in the first center bleed line 12, is guided to the pressure receiving chamber of the negative control piston 33. The first negative control pressure Pn1 is determined by the degree of restriction of the hydraulic oil flowing through the central passage 4a by the spool. When the first negative control pressure Pn1 increases, the negative control piston 33 advances and the tilt angle of the first hydraulic pump 21 increases. If the first negative control pressure Pn1 is reduced and the negative control piston 33 is retracted, the tilt angle of the first hydraulic pump 21 is increased.

The horsepower control piston 34a is for decreasing the discharge flow rate of the first hydraulic pump 21 as they increase in accordance with the discharge pressure Pd1 and the power shift pressure Ps of the first hydraulic pump 21. Specifically, the first regulator 3A is formed with two pressure receiving chambers for causing the horsepower control piston 34a to press the spool 32. The two pressure receiving chambers of the horsepower control piston 34a are connected to the first supply line 11 and a power shift line 71A, which will be described later, respectively. The pressure receiving chambers are respectively connected to the discharge pressure Pd1 of the first hydraulic pump 21 and A power shift pressure Ps is derived.

The negative control piston 33 and the horsepower control piston 34a are configured so as to press the spool 32 with priority given to the one that restricts the discharge flow rate of the first hydraulic pump 21 (the one that is reduced).

The second regulator 3B has the same configuration as the first regulator 3A except that a horsepower control piston 34b is employed instead of the horsepower control piston 34a. That is, the second regulator 3B adjusts the tilt angle of the second hydraulic pump 22 by the negative control piston 33 based on the second negative control pressure Pn2.

According to the discharge pressure Pd2 of the second hydraulic pump 22, the discharge pressure Pd1 of the first hydraulic pump 21, and the power shift pressure Ps, the horsepower control piston 34b decreases the discharge flow rate of the second hydraulic pump 22 as they increase. Is for. Specifically, the second regulator 3B is formed with three pressure receiving chambers for causing the horsepower control piston 34b to press the spool 32. The three pressure receiving chambers of the horsepower control piston 34b are connected to the second supply line 15, the first supply line 11 and the power shift line 71A, respectively, and the pressure receiving chambers of the second hydraulic pump 22 are respectively connected thereto. The discharge pressure Pd2, the discharge pressure Pd1 of the first hydraulic pump 21, and the power shift pressure Ps are introduced.

Due to the difference between the horsepower control piston 34a and the horsepower control piston 34b, the spring 35a biasing the spool 32 from the opposite side of the horsepower control piston 34a in the first regulator 3A and the horsepower control piston 34b in the second regulator 3B are opposite. The urging forces of the springs 35b that urge the spool 32 from the side are different from each other.

The discharge pressure from the auxiliary pump 23 driven by the engine 10 is supplied as a primary pressure to the proportional valve 72 through the pilot pressure supply line 71. The control pressure from the proportional valve 72 is output to the power shift line 71A, and a pair of branch lines are connected from the power shift line 71A to one of the pressure receiving chambers of the horsepower control piston 34a in the first regulator 3A and the second regulator 3B. Extends to one of the pressure receiving chambers of the horsepower control piston 34b.

The proportional valve 72 is for setting the power shift pressure Ps guided to the first regulator 3A and the second regulator 3B.

The proportional valve 72 is controlled by the controller 8. The controller 8 includes an arithmetic device, a storage device, and the like. In the present embodiment, the controller 8 controls the proportional valve 72 so that the power shift pressure Ps increases and the discharge flow rates of the first hydraulic pump 21 and the second hydraulic pump 22 decrease when only the turning spool 41 operates. To control. Hereinafter, a configuration for the control will be described.

The turning pilot circuit 61 is provided with a turning pressure detector 81 for detecting that the pilot pressure of the turning pilot circuit 61 is raised, in other words, that the operation lever of the turning operation valve 51 is tilted. ing. The turning pressure detector 81 is configured to selectively detect the pilot pressure with the higher pilot pressure among the right turning line 61A and the left turning line 61B, which are a pair of pilot lines. In the present embodiment, a pressure sensor is used as the turning pressure detector 81. However, the turning pressure detector 81 may be a pressure switch that is turned on or off when a pilot pressure is established in the turning pilot circuit 61.

The spool operation detection line 73 branches from the power shift line 71A. The spool operation detection line 73 extends across the first multi-control valve 4A and the second multi-control valve 4B so as to pass through the monitoring spool 40, and is connected to the tank.

In this embodiment, the monitoring spool 40 is the turning spool 41 of the first multi-control valve 4A, the bucket spool 44, the boom spool 45, and the arm spool 46 of the second multi-control valve 4B. However, it goes without saying that the order in which the spool operation detection line 73 passes through the monitoring spool 40 is not particularly limited. Further, as the monitoring spool 40, the boom spool 42 and the arm spool 43 of the first multi-control valve 4A may be employed instead of the boom spool 45 and the arm spool 46 of the second multi-control valve 4B. Good. Further, when the first multi-control valve 4A or the second multi-control valve 4B includes an option spool, the option spool may be included in the monitoring spool 40.

As shown in FIG. 2, the turning spool 41 is configured not to block the spool operation detection line 73 even when it is operated even when it is positioned at the neutral position (when it is moved from the neutral position). On the other hand, the monitoring spool 40 other than the turning spool does not block the spool operation detection line 73 when positioned at the neutral position, but blocks the spool operation detection line 73 when operated (when moved from the neutral position). It is configured. That is, the spool operation detection line 73 is not blocked when only the swing operation valve 51 is operated, but is blocked when any one of the bucket operation valve 53, the boom operation valve 54, and the arm operation valve 52 is operated.

The upstream side of the spool operation detection line 73 is provided with a throttle 74 for preventing the pressure of the pilot pressure supply line 71 from excessively decreasing even when all the monitoring spools are neutral. The spool operation detection line 73 is provided with a monitoring pressure detector 75 between the throttle 74 and the second multi-control valve 4B for detecting that the spool operation detection line 73 is blocked. In the present embodiment, a pressure sensor is used as the monitoring pressure detector 75. However, the monitoring pressure detector 75 may be a pressure switch that is turned on or off when the spool operation detection line 73 is interrupted.

When the turning pressure detector 81 and the monitoring pressure detector 75 determine that only the turning operation valve 51 has been operated, the controller 8 controls the proportional valve 72 so that the power shift pressure Ps is increased. Thereby, the discharge flow rates of the first hydraulic pump 21 and the second hydraulic pump 22 are reduced. As a result, the amount of hydraulic oil supplied to the turning hydraulic motor 24 during turning acceleration can be suppressed, and wasteful consumption of energy can be suppressed. Note that the controller 8 may control the proportional valve 72 so that the power shift pressure Ps is restored after the acceleration period of turning has passed.

Here, in FIG. 9B, the performance characteristic of the first hydraulic pump 21 when the power shift pressure Ps is raised is indicated by a two-dot chain line C. A solid line A in the figure indicates the performance characteristic of the first hydraulic pump 21 when the power shift pressure Ps is low, that is, before the power shift pressure is increased. FIG. 9B shows that the discharge flow rate of the first hydraulic pump 21 can be kept low by increasing the power shift pressure Ps in the case of a single turning operation.

In addition, in the present embodiment, since the turning pressure detector 81 is provided in the turning pilot circuit 61, the above-described effects can be obtained with an inexpensive configuration as compared with the case where the pressure detector is provided in the first supply line 11. Can do. Further, in the present embodiment, since the power shift pressure Ps is used while being superimposed on the horsepower control by the regulator, an increase in the discharge flow rate of the first hydraulic pump 21 is suppressed with simple control logic in the case of a single turning operation. Can be obtained. Furthermore, the load pressure acting on the swing hydraulic motor 24 decreases as it proceeds to the second half of the swing acceleration, and a large flow rate is required to increase the swing speed. In this embodiment, however, the power shift pressure Ps causes the flow rate to increase. Although the discharge flow rate of the first hydraulic pump 21 during the turning single operation is temporarily reduced, in the latter half of the turning acceleration, as the discharge pressure Pd1 of the first hydraulic pump 21 decreases, the horsepower control action by the regulator described above is performed. As a result, the discharge flow rate of the first hydraulic pump 21 automatically increases. As a result, the hydraulic hydraulic motor 24 is supplied with a sufficient amount of hydraulic oil corresponding to the load at each turning stage, so that the feeling of operation during turning is not impaired.

Furthermore, since the spool operation detection line 73 is not cut off even when the turning spool 41 is operated, the turning operation valve is simply provided with a pressure detector in the turning pilot circuit 61 and the spool operation detection line 73. It can be detected that only 51 has been operated. That is, it is possible to detect a single turning operation with a simple configuration.

In this embodiment, since the discharge flow rate of the second hydraulic pump 22 depends on the discharge pressure Pd1 of the first hydraulic pump 21 as in the conventional case, the first hydraulic pump 21 is unloaded on the second hydraulic pump 22 side. In some cases (for example, in the case of single bucket operation), the discharge flow rate can be increased.

<Modification>
In the above embodiment, the proportional valve 72 is controlled so that the power shift pressure Ps is increased when only the turning spool 41 is operated. However, the proportional valve 72 is not controlled even when only the turning spool 41 is operated. In addition, the power shift pressure Ps may be kept constant. That is, in the configuration of the first regulator 3A shown in FIG. 1, the discharge flow rate of the first hydraulic pump 21 does not depend on the discharge pressure Pd2 of the second hydraulic pump 22, and does not change depending on the load state of the second hydraulic pump 22. Absent. In other words, even if the load state of the second hydraulic pump 22 changes, the solid line A in FIG. 9B remains unchanged. For this reason, even if the power shift pressure Ps is kept constant, the discharge flow rate of the first hydraulic pump 21 does not become excessive during the turning operation, and wasteful consumption of energy during turning acceleration can be suppressed. it can. However, if the power shift pressure Ps is increased when only the turning spool 41 is operated as in the above-described embodiment, the wasteful consumption of energy at the time of turning acceleration is effectively suppressed during turning operation alone. Can do. Note that the modification example in which the power shift pressure Ps is kept constant during the turning operation can also be applied to second to fourth embodiments described later.

The spool operation detection line 73 does not necessarily have to pass through the turning spool 41, and the number of ports for the turning spool 41 may be six. In this case, the spool operation detection line 73 may be provided only in the second multi-control valve 4B.

(Second Embodiment)
Next, with reference to FIG. 3 and FIG. 4, the hydraulic drive system which concerns on 2nd Embodiment of this invention is demonstrated. In the present embodiment and third and fourth embodiments to be described later, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

In this embodiment, as shown in FIG. 4, when the turning spool 41 is operated, the spool operation detection line 73 is cut off. That is, the spool operation detection line 73 is shut off regardless of which of the swing operation valve 51, the bucket operation valve 53, the boom operation valve 54, and the arm operation valve 52 (see FIG. 1 for the operation valves 51 to 54). .

Therefore, as a configuration for detecting that only the turning operation valve 51 is operated, as shown in FIG. 3, in any of the pilot circuits 62 to 64 for operating the monitoring spool 40 other than the turning spool 41. A non-turning pressure detector 82 is provided for detecting that the pilot pressure has been established. The non-turning pressure detector 82 is configured to selectively detect the pilot pressure of the highest pilot pressure among all the pilot lines (62A to 64B) of the pilot circuits 62 to 64. In the present embodiment, a pressure sensor is used as the non-turning pressure detector 82. However, the non-turning pressure detector 82 may be a pressure switch that is turned on or off when a pilot pressure is established in any of the pilot circuits 62 to 64.

Also in this embodiment, similarly to the first embodiment, when only the turning spool 41 is operated, the controller 8 increases the power shift pressure Ps and the discharge flow rates of the first hydraulic pump 21 and the second hydraulic pump 22. The proportional valve 72 is controlled so as to decrease. Thereby, the effect similar to 1st Embodiment can be acquired.

Further, in the present embodiment, since the spool operation detection line 73 is cut off when the turning spool 41 is operated, it is possible to detect a turning single operation using a turning spool having a normal structure. it can. In other words, the hydraulic drive system incorporated in the existing construction machine can be modified at low cost to the hydraulic drive system of the present embodiment.

(Third embodiment)
Next, with reference to FIGS. 5 and 6, a hydraulic drive system 1B according to a third embodiment of the present invention will be described. In this embodiment, the structure which can detect not only turning operation but the bucket out operation and boom lowering operation with small required flow volume is employ | adopted. Then, the controller 8 is operated not only when only the turning spool 41 is operated, but also when the turning spool 41 is operated and the bucket spool 44 and / or the boom spool 45 has a smaller required flow rate (bucket out and Also, when operated in the direction of lowering the boom, the proportional valve 72 is controlled so that the power shift pressure Ps increases and the discharge flow rates of the first hydraulic pump 21 and the second hydraulic pump 22 decrease.

More specifically, as shown in FIG. 6, the bucket spool 44 is configured not to block the spool operation detection line 73 even when it operates in the bucket-out direction. Further, the bucket pilot circuit 63 is provided with a bucket-out pressure detector 83 for detecting that the pilot pressure in the bucket-out line 63B has risen. In the present embodiment, a pressure sensor is used as the bucket-out pressure detector 83. However, the bucket-out pressure detector 83 may be a pressure switch that is turned on or off when the pilot pressure of the bucket-out line 63B is raised.

Furthermore, it is configured so that the spool operation detection line 73 is not blocked even when the boom spool 45 is operated in the boom lowering direction. Further, the boom pilot circuit 64 is provided with a boom lowering pressure detector 84 for detecting that the pilot pressure of the boom lowering line 64B has been raised. In the present embodiment, a pressure sensor is used as the boom lowering pressure detector 84. However, the boom lowering pressure detector 84 may be a pressure switch that is turned on or off when the pilot pressure of the boom lowering line 64B is raised.

And the controller 8 controls the proportional valve 72 so that the power shift pressure Ps becomes high in the following four cases. Thereby, the discharge flow rate with respect to the discharge pressure of each of the first hydraulic pump 21 and the second hydraulic pump 22 decreases. As a result, the amount of hydraulic oil supplied to the turning hydraulic motor 24 during turning acceleration can be suppressed, and wasteful consumption of energy can be suppressed. Note that the controller 8 may control the proportional valve 72 so that the power shift pressure Ps is restored after the acceleration period of turning has passed.

The first of the four cases described above is based on the pilot pressure detection by the turning pressure detector 81 and the non-detection of the monitoring pressure detector 75, the bucket-out pressure detector 83, and the boom lowering pressure detector 84. This is a case where it is determined that only the operation valve 51 has been operated. Second, the swing operation valve 51 is operated by the pilot pressure detection by the swing pressure detector 81 and the bucket-out pressure detector 83 and the non-detection of the monitoring pressure detector 75 and the boom lowering pressure detector 84. And it is a case where it determines with the bucket operation valve 53 having been operated in the bucket out direction. Third, the turning operation valve 51 is operated by detecting the pilot pressure by the turning pressure detector 81 and the boom lowering pressure detector 84 and by not detecting the monitoring pressure detector 75 and the bucket-out pressure detector 83. And it is a case where it determines with the boom operation valve 54 having been operated by the boom lowering direction. Fourth, the swing operation valve 51 is operated by the pilot pressure detection by the swing pressure detector 81, the bucket-out pressure detector 83, and the boom lowering pressure detector 84 and the non-detection of the monitoring pressure detector 75. In this case, it is determined that the bucket operation valve 53 is operated in the bucket-out direction and the boom operation valve 54 is operated in the boom lowering direction.

According to the configuration of the present embodiment, not only during turning operation alone, but also frequently performed operations such as simultaneous operation of turning and boom lowering, simultaneous operation of turning and bucket out, and simultaneous operation of turning and boom lowering and bucket out. Also in this case, it is possible to effectively suppress wasteful consumption of energy during acceleration of turning.

<Modification>
Both the bucket-out operation and the boom lowering operation do not necessarily need to be detectable, and either one may be detectable.

Further, if the non-turning pressure detector 82 shown in FIG. 7 is employed as in the second embodiment, the turning spool 41, the bucket spool 44, and the boom spool 45 are replaced with a normal one as shown in FIG. It can be changed to a structure (a structure that shuts off the spool operation detection line 73 when it is operated). In this case, since the bucket-out pressure detector 83 and the boom lowering pressure detector 84 are provided in this embodiment, as shown in FIG. 7, the non-turning pressure detector 82 selectively applies the pilot pressure. The boom lowering line 64B and the bucket out line 63B may be removed from the pilot line to be detected.

(Fourth embodiment)
Next, with reference to FIG. 8, a hydraulic drive system 1C according to a fourth embodiment of the present invention will be described. In this embodiment, all the monitoring spools 40 have a normal structure as shown in FIG. 4 (a structure that shuts off the spool operation detection line 73 when operated).

In this embodiment, in addition to the bucket-out pressure detector 83 and the boom lowering pressure detector 84 described in the third embodiment, the bucket-in pressure detector is connected to the bucket-in line 63A of the bucket pilot circuit 63. 85, a boom raising pressure detector 86 is provided on the boom raising line 64A of the boom pilot circuit 64, and an arm pressure detector 87 is provided on the arm pilot circuit 62 (arm-in line 62A and arm-out line 62B). Is provided. The bucket-in pressure detector 85 is for detecting that the pilot pressure in the bucket-in line 63A has been established, and the boom raising pressure detector 86 has been established in the boom raising line 64A. The arm pressure detector 87 is for detecting that the pilot pressure of the arm pilot circuit 62 (arm-in line 62A and arm-out line 62B) has been established.

In this embodiment, as in the third embodiment, not only a turning operation but also a bucket-out operation and a boom lowering operation with a small required flow rate can be detected. Therefore, the present embodiment can provide the same effects as those of the third embodiment. In this embodiment, since the pressure detectors are provided in the pilot circuits 61 to 64 of all the operation valves 51 to 54, the monitoring spool 40 is a swirl spool 41 having a normal structure, and a bucket spool 44. Even if the boom spool 45 and the arm spool 46 are used, it is possible to detect the turning operation alone. As a result, the hydraulic drive system incorporated in the existing construction machine can be retrofitted to the hydraulic drive system of the present embodiment at a low cost.

In this embodiment, the arm spool 46 of the second multi-control valve 4B is the monitoring spool 40. However, as described in the first embodiment, the arm spool 43 of the first multi-control valve 4A is monitored. Needless to say, the spool 40 may be used.

Further, in the case of detecting only the turning single operation and the simultaneous turning and boom lowering operation, the bucket pilot circuit 63 uses a bucket-in line instead of the bucket-out pressure detector 83 and the bucket-in pressure detector 85. A pressure detector (not shown) configured to selectively detect a pilot pressure having a higher pilot pressure among 63A and the bucket-out line 63B may be provided. Similarly, in the case of detecting only a single turning operation and a simultaneous turning and bucket-out operation, the boom pilot circuit 64 uses a boom raising pressure detector 84 and a boom raising pressure detector 86 instead of the boom raising pressure detector 84. A pressure detector (not shown) configured to selectively detect the pilot pressure with the higher pilot pressure out of the line 64A and the boom lowering line 64B may be provided.

(Other embodiments)
In the first to fourth embodiments, the discharge flow rate control method of the first and second

hydraulic pumps

21 and 22 is not necessarily the negative control method, and may be the positive control method. That is, the first and second regulators 3 </ b> A and 3 </ b> B may have a positive control piston instead of the negative control piston 33. Or the system (what is called an electric positive control) which performs flow control electrically may be used. Further, the control method of the discharge flow rate of the first and second

hydraulic pumps

21 and 22 may be a load sensing method.

The hydraulic drive system of the present invention is useful for various construction machines.

DESCRIPTION OF SYMBOLS 1A-1C Hydraulic drive system 21 1st hydraulic pump 22 2nd hydraulic pump 24 Turning hydraulic motor 3A 1st regulator 3B 2nd regulator 4A 1st multi-control valve 4B 2nd multi-control valve 40 Monitoring spool 41 Turning spool 44

Bucket Spool

42, 45 Boom spool 61-64 Pilot circuit 63B Bucket out line 64B Boom lowering line 72 Proportional valve 73 Spool operation detection line 75 Monitoring pressure detector 8 Controller 81 Swing pressure detector 82 Non-turning pressure Detector 83 Bucket-out pressure detector 84 Boom lowering pressure detector

Claims

A hydraulic drive system for a construction machine having a swing hydraulic motor,
A first hydraulic pump and a second hydraulic pump that are driven by an engine to discharge hydraulic oil at a flow rate according to a tilt angle;
A first multi-control valve connected to the first hydraulic pump and including a swing spool for controlling the swing hydraulic motor;
A second multi-control valve connected to the second hydraulic pump;
A first regulator that adjusts a tilt angle of the first hydraulic pump so that a discharge flow rate of the first pump decreases as they increase according to a discharge pressure and a power shift pressure of the first hydraulic pump;
In accordance with the discharge pressure of the second hydraulic pump and the first hydraulic pump and the power shift pressure, the tilt angle of the second hydraulic pump is adjusted so that the discharge flow rate of the second pump decreases as they increase. A second regulator that
A proportional valve for setting the power shift pressure led to the first regulator and the second regulator;
A hydraulic drive system comprising:
When only the turning spool is operated, or when the turning spool is operated and one or more spools included in the second multi-control valve are operated in a direction where the required flow rate is low, the power 2. The hydraulic drive system according to claim 1, further comprising a controller that controls the proportional valve so that a shift pressure increases and a discharge flow rate of the first hydraulic pump and the second hydraulic pump decreases.
A spool operation detection line extending across the first multi-control valve and the second multi-control valve so as to pass through the monitoring spool including the turning spool;
A monitoring pressure detector for detecting that the spool operation detection line is shut off;
A turning pressure detector for detecting that a pilot pressure of a pilot circuit for operating the turning spool has been established,
The hydraulic drive system according to claim 2, wherein the turning spool is configured not to block the spool operation detection line even when the spool is operated.
A spool operation detection line extending across the first multi-control valve and the second multi-control valve so as to pass through the monitoring spool including the turning spool;
A turning pressure detector for detecting that a pilot pressure of a pilot circuit for operating the turning spool has been established;
A non-turning pressure detector for detecting that a pilot pressure has been established in any of the pilot circuits that operate the monitoring spool other than the turning spool;
The hydraulic drive system according to claim 2, wherein the turning spool is configured to shut off the spool operation detection line when operated.
The construction machine is a hydraulic excavator including a bucket, an arm and a boom,
The second multi-control valve includes a bucket spool and a boom spool as the monitoring spool,
The bucket spool is configured not to interrupt the spool operation detection line even when operated in the bucket-out direction,
The boom spool is configured not to block the spool operation detection line even when operated in a boom lowering direction.
A bucket-out pressure detector for detecting that the pilot pressure of the bucket-out line in the pilot circuit for operating the bucket spool has been established;
A boom lowering pressure detector for detecting that the pilot pressure of the boom lowering line in the pilot circuit for operating the boom spool is raised;
The hydraulic drive system according to claim 3 or 4, further comprising:
The construction machine is a hydraulic excavator including a bucket, an arm and a boom,
A spool operation detection line extending across the first multi-control valve and the second multi-control valve so as to pass through the monitoring spool including the turning spool;
Either the first multi-control valve or the second multi-control valve includes an arm spool as the monitoring spool,
The second multi-control valve includes a bucket spool and a boom spool as the monitoring spool,
The swing spool, the arm spool, the bucket spool, and the boom spool are configured to shut off the spool operation detection line when operated.
Each of the pilot circuits for operating the turning spool, the arm spool, the bucket spool, and the boom spool is provided with a pressure detector for detecting that the pilot pressure of the pilot circuit has been established. The hydraulic drive system according to claim 1.