Work machine

Abstract

A working machine includes: a hydraulic actuator driven by hydraulic oil from a hydraulic pump; a fully open center directional control valve disposed in an intermediate bypass line and controlling the flow of hydraulic oil supplied to the hydraulic actuator; a CB shutoff valve disposed in the intermediate bypass line between the directional control valve and a hydraulic oil tank; and a machine controller that controls the opening of the CB shutoff valve. The machine controller reduces the opening of the CB shutoff valve when an operation on the hydraulic actuator is in a micro-operation state within a predetermined range representing a micro-operation region, and this micro-operation state continues for more than a predetermined period. Otherwise, the CB shutoff valve is fully opened.

Description

Technical Field

[0001] The present invention relates to a working machine, and more particularly to a working machine that uses a fully open-center directional control valve to control driving of a hydraulic actuator. Background Art

[0002] Hydraulic excavators, wheel loaders, cranes, and other work machines typically use a system that supplies hydraulic oil from a hydraulic pump driven by a prime mover to a hydraulic actuator. The hydraulic actuator is driven by a directional control valve that controls the direction and flow rate of hydraulic oil supplied from the hydraulic pump to the hydraulic actuator.

[0003] One type of directional control valve is a fully open center type. This directional control valve has an inlet throttle passage that directs the hydraulic oil from the hydraulic pump to the hydraulic actuator and a bypass throttle passage that returns the hydraulic oil to the working oil tank. The opening areas of the two passages vary. When no operation is performed on the hydraulic actuator, the opening area of the bypass throttle passage is at its maximum, while the inlet throttle passage is closed. As a result, the entire amount of hydraulic oil discharged from the hydraulic pump flows into the working oil tank via the bypass throttle passage of the directional control valve. In contrast, when an operation is performed on the hydraulic actuator, the opening area of the bypass throttle passage decreases according to the amount of operation, while the opening area of the inlet throttle passage increases. As a result, some or all of the hydraulic oil discharged from the hydraulic pump flows into the hydraulic actuator via the inlet throttle passage of the directional control valve.

[0004] The fully open center directional control valve is constructed in such a way that the opening area of its two passages is determined by the movement (stroke) of the spool, which serves as the valve body. This movement (spool stroke) is adjusted by operating the operating device. By operating the operating device, the operator can control the position and speed of the hydraulic actuator through the directional control valve, enabling various operations such as excavation and land leveling.

[0005] When precise operation is required, the operator performs smaller operations, reducing the spool stroke of the directional control valve. In this operating range, the opening area of the bypass throttle passage is larger than the opening area of the inlet throttle passage to prevent the flow rate of hydraulic oil flowing into the hydraulic actuator from changing dramatically with the amount of operation. This reduces the shock during hydraulic actuator startup, ensuring smoother actuator operation and facilitating speed adjustment.

[0006] On the other hand, when the operator wants to operate the hydraulic actuator at high speed, he or she performs a large amount of operation, which increases the spool stroke of the directional control valve accordingly. In this operating range, the opening area of the bypass throttle passage decreases, while the opening area of the inlet throttle passage increases relatively, allowing a large amount of hydraulic oil from the hydraulic pump to flow into the hydraulic actuator.

[0007] The hydraulic oil that returns to the working oil tank through the bypass throttling passage of the directional control valve loses energy (bypass throttling loss), so it is preferably smaller from the perspective of energy saving. Therefore, a technology that can achieve energy saving while suppressing the discomfort caused by the operation of the working machine has been proposed (see patent document 1). In the working machine described in patent document 1, a bypass throttling flow control valve is arranged in the bypass throttling pipeline that connects the actuator flow control valve (directional control valve) of the fully open center type to the oil tank, and the opening of the bypass throttling flow control valve is controlled according to the operation amount of the operating device. When the operation amount of the operating device is small, the opening (bypass throttling opening area) of the bypass throttling flow control valve becomes larger, and accordingly, the bypass throttling flow rate becomes larger. As the operation amount becomes larger, the opening of the bypass throttling flow control valve becomes smaller, and accordingly, the bypass throttling flow rate becomes smaller.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: International Publication No. 2014 / 061741 Summary of the Invention

[0011] Problems to be solved by the invention

[0012] However, in recent working machines, by changing the relationship between the valve core stroke of the directional control valve that controls the drive of each hydraulic actuator and the opening area of each passage, energy consumption can be improved within a range that does not impair operability. In particular, in the area of small operating volume where the proportion of bypass throttling loss increases, energy consumption can be improved by changing this relationship. Specifically, a valve core with a smaller opening area of the bypass throttling passage when the valve core stroke is smaller is used. In other words, the area where the opening area of the bypass throttling passage is close to 0 is expanded only from the area with a larger valve core stroke (the area of full operation) to an area smaller than it (the area of half operation). As a result, the bypass throttling loss is suppressed in the area of half operation as well as the area of full operation.

[0013] However, improvements to the spool structure of such directional control valves (the relationship between spool stroke and the opening area of each passage) have reached a limit in reducing bypass flow losses. This is because, as mentioned above, in the region of small spool stroke (a micro-operation region), a relatively large bypass flow passage opening area is required to ensure operability during startup and slow speeds of the hydraulic actuator. Therefore, further reduction of the bypass flow passage opening area is difficult in this region.

[0014] Therefore, it is studied whether it is possible to reduce the bypass throttling loss by using the bypass throttling flow control valve described in Patent Document 1, rather than improving the valve core structure of the directional control valve. However, in the technology described in Patent Document 1, the opening degree (bypass throttling opening area) of the bypass throttling flow control valve is controlled according to the operation amount of the operating lever, so the bypass throttling flow rate is determined according to the operation amount. Therefore, when the micro-operation of the hydraulic actuator is continuously performed, the bypass throttling flow rate always increases, except when the hydraulic actuator is started, even during the operation after starting. That is, even if the technology described in Patent Document 1 is used, the effect of reducing the energy consumption (bypass throttling loss) during micro-operation is small.

[0015] The present invention has been made based on the above circumstances, and an object of the present invention is to provide a working machine capable of achieving both operability and energy saving during micro-manipulation of a hydraulic actuator.

[0016] Means for solving problems

[0017] The present application includes multiple means for solving the above-mentioned problems. As an example, it includes: a hydraulic pump, which is driven by a prime mover; a hydraulic actuator, which is driven by hydraulic oil supplied from the hydraulic pump; an intermediate bypass line, one side of which is connected to the discharge side of the hydraulic pump and the other side is connected to the working oil tank; a center-fully-open directional control valve, which is arranged on the intermediate bypass line and controls the flow of hydraulic oil supplied from the hydraulic pump to the hydraulic actuator; an intermediate bypass stop valve, which is arranged between the directional control valve and the working oil tank on the intermediate bypass line; and a control device, which controls the opening of the intermediate bypass stop valve, wherein the control device reduces the opening of the intermediate bypass stop valve when the operation of the hydraulic actuator is in a micro-operation state within a predetermined range of the area representing the micro-operation and the micro-operation state continues for more than a predetermined period, and fully opens the intermediate bypass stop valve in other cases.

[0018] Effects of the Invention

[0019] According to the present invention, during the initial stage of a micro-manipulation of the hydraulic actuator, the intermediate bypass stop valve does not reduce the bypass flow rate, thereby preserving the operability of the hydraulic actuator. Furthermore, after a predetermined period of micro-manipulation has elapsed, the intermediate bypass stop valve is opened to reduce the bypass flow rate, thereby achieving energy savings. In other words, both operability and energy savings can be achieved during micro-manipulation of the hydraulic actuator.

[0020] Other problems, structures, and effects than those described above will become clear from the following description of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a perspective view showing a hydraulic excavator according to a first embodiment of a working machine to which the present invention is applied.

[0022] Figure 2 This is a circuit diagram showing a main configuration of a hydraulic system in a first embodiment of a working machine according to the present invention.

[0023] Figure 3 This is a characteristic diagram showing changes in the meter-out opening area and the meter-in opening area relative to the valve body stroke of the directional control valve constituting a part of the first embodiment of the working machine of the present invention.

[0024] Figure 4 This is a block diagram showing the functional configuration of a controller constituting a part of the first embodiment of the working machine according to the present invention.

[0025] Figure 5 This is a flowchart showing an example of a control procedure of a controller constituting a part of the first embodiment of the working machine according to the present invention.

[0026] Figure 6 This is a diagram showing an example of temporal behavior of each component of the hydraulic system in the first embodiment of the working machine according to the present invention during full operation.

[0027] Figure 7 This is a diagram showing an example of temporal behavior during micro-manipulation of each component of the hydraulic system in the first embodiment of the working machine according to the present invention.

[0028] Figure 8 This is a block diagram showing the functional configuration of a controller constituting a part of a modified example of the first embodiment of the working machine according to the present invention.

[0029] Figure 9 This is a diagram showing an example of temporal behavior of each component of the hydraulic system during micro-manipulation in a modified example of the first embodiment of the working machine according to the present invention.

[0030] Figure 10This is a block diagram showing the functional configuration of a controller constituting a part of the second embodiment of the working machine according to the present invention. DETAILED DESCRIPTION

[0031] Hereinafter, an embodiment of a working machine of the present invention will be described using the drawings. In this embodiment, a hydraulic excavator will be described as an example of a working machine.

[0032] [First embodiment]

[0033] First, use Figure 1 The structure of a hydraulic excavator as a first embodiment of a working machine according to the present invention will be described. Figure 1 This is a perspective view showing a hydraulic excavator according to a first embodiment of a working machine to which the present invention is applied. The description will be made using a view from an operator seated on a driver's seat of the hydraulic excavator.

[0034] exist Figure 1 In the figure, a hydraulic excavator as a working machine is composed of a multi-articulated front working device 1 for performing excavation work and a machine body 2 to which the front working device 1 is mounted. The machine body 2 is composed of a freely movable lower traveling body 3 and an upper rotating body 4 rotatably mounted on the lower traveling body 3.

[0035] The front working device 1 is provided at the front of the upper rotating body 4 so as to be capable of pitching and descending. The front working device 1 is composed of, for example, a boom 6, an arm 7, and a bucket 8 serving as a working tool. The base end side of the boom 6 is rotatably supported at the front of the upper rotating body 4. The base end of the arm 7 is rotatably mounted to the front end of the boom 6. The base end of the bucket 8 is rotatably mounted to the front end of the arm 7. The boom 6, arm 7, and bucket 8 are driven by a boom cylinder 9, an arm cylinder 10, and a bucket cylinder 11, respectively, which serve as hydraulic actuators.

[0036] The lower traveling structure 3 has crawler-type traveling devices 13 on the left and right. The left and right traveling devices 13 are driven by traveling hydraulic motors 13a (only one is shown) serving as hydraulic actuators.

[0037] The upper revolving structure 4 is rotated relative to the lower traveling structure 3 by a revolving hydraulic motor (not shown) serving as a hydraulic actuator. The upper revolving structure 4 is configured to include: a cab 15, which is installed on the front left side of a revolving frame (not shown) serving as a supporting structure; a counterweight 16, which is installed at the rear end of the revolving frame; and a machine room 17, which is installed between the cab 15 and the counterweight 16. The cab 15 is provided with a driver's seat (not shown) for the operator, operating devices 41 and 42 described later, and an engine control dial 43 (see later). Figure 2) etc. The counterweight 16 adjusts the weight balance with the front working device 1. The machine room 17 accommodates the engine 21 and the hydraulic pump 22 (see the following) Figure 2 ) and other equipment.

[0038] The movement of the boom 6, arm 7, bucket 8 and upper rotating structure is instructed by an operation signal from an operating lever device (not shown). The movement of the lower traveling structure is instructed by an operation signal from an operating pedal device (not shown).

[0039] Next, use Figure 2 and Figure 3 A description will be given of a main configuration of a hydraulic system in a first embodiment of a working machine according to the present invention. Figure 2 This is a circuit diagram showing a main configuration of a hydraulic system in a first embodiment of a working machine according to the present invention. Figure 3 This is a characteristic diagram showing changes in the bleed-off opening area and the meter-in opening area relative to the spool stroke of a directional control valve constituting a part of the first embodiment of the working machine of the present invention.

[0040] Figure 2 The hydraulic system 20 shown has a hydraulic pump 22 driven by an engine 21 as a prime mover; a first hydraulic actuator 23 and a second hydraulic actuator 24 driven by the hydraulic oil discharged from the hydraulic pump 22; and a first directional control valve 25 and a second directional control valve 26 of a fully open center type, which control the flow (direction and flow rate) of the hydraulic oil supplied from the hydraulic pump 22 to the first hydraulic actuator 23 and the second hydraulic actuator 24, respectively. In addition, Figure 2 This figure shows a typical circuit diagram for driving two hydraulic actuators. Figure 2 The circuit parts of the other multiple hydraulic actuators not shown in the figure are also connected to Figure 2 The circuit parts shown are constructed in the same way.

[0041] The engine 21 is mechanically connected to the rotary shaft of the hydraulic pump. The engine 21 includes an injection device 21a for injecting fuel. The engine controller 58 described later adjusts the fuel injection amount of the injection device 21a to control the rotation speed of the engine 21.

[0042] The hydraulic pump 22 is a variable displacement pump having a variable displacement mechanism including a swash plate or a slanted shaft. The hydraulic pump 22 includes a regulator 22a that adjusts the pump capacity by controlling the tilt of the swash plate or slanted shaft of the variable displacement mechanism. The regulator 22a adjusts the pump capacity based on a command signal from a machine controller 60 (described later). The hydraulic pump 22 is connected to a first directional control valve 25 and a second directional control valve 26 via a discharge line 27.

[0043] The first hydraulic actuator 23 and the second hydraulic actuator 24 are composed of the above-mentioned boom cylinder 9, arm cylinder 10, bucket cylinder 11, and left and right travel hydraulic motors 13a (all refer to Figure 1 ), any one of the rotary hydraulic motors. Figure 2 , a hydraulic cylinder is illustrated by way of example.

[0044] A first directional control valve 25 and a second directional control valve 26, both fully open in center, are arranged in sequence from the hydraulic pump 22 side toward the hydraulic tank 28 on an intermediate bypass line 29 that guides hydraulic oil discharged from the hydraulic pump 22. The intermediate bypass line 29 extends through the neutral positions of the first and second directional control valves 25, 26, connecting the upstream first directional control valve 25 and the downstream second directional control valve 26 in series. One end (upstream) of the intermediate bypass line 29 is connected to a discharge line 27, serving as the discharge side of the hydraulic pump, and the other end (downstream) is connected to the hydraulic tank 28. The first and second directional control valves 25, 26 are connected in parallel with the hydraulic pump 22 via, for example, a hydraulic oil supply line 30.

[0045] The first and second directional control valves 25 and 26 are hydraulically pilot-operated valves, each with a valve spool that moves according to the magnitude of the applied pilot pressure. The valve spools of each directional control valve 25 and 26 are provided with meter-in passages 25a and 26a, meter-out passages 25b and 26b, and a meter-out passage (not shown). The meter-in passages 25a and 26a of each directional control valve 25 and 26 connect the discharge line 27 to the meter-in side of each hydraulic actuator 23 and 24. The opening area of the meter-in passages 25a and 26a of each directional control valve 25 and 26 is referred to as the meter-in opening area. The meter-out passages 25b and 26b of each directional control valve 25 and 26 connect the discharge line 27 to the intermediate bypass line 29. The opening area of the meter-out passages 25b and 26b of each directional control valve 25 and 26 is referred to as the meter-out opening area. The meter-out passages of each directional control valve 25 or 26 connect the meter-out side of each hydraulic actuator 23 or 24 to the hydraulic oil tank 28. The opening area of the meter-out passages of each directional control valve 25 or 26 is referred to as the meter-out opening area. In each directional control valve 25 or 26, the ratio of the three opening areas—the meter-in opening area, the meter-bypass opening area, and the meter-out opening area—changes as the valve spool moves. The ratio of these three opening areas in each directional control valve 25 or 26 changes according to the valve spool stroke, thereby distributing the discharge flow rate of the hydraulic pump 22 to each hydraulic actuator 23 or 24 and the hydraulic oil tank 28, thereby adjusting the driving (direction, position, speed, etc.) of each hydraulic actuator 23 or 24. Specifically, each hydraulic actuator 23 or 24 is driven at a speed proportional to the flow rate of hydraulic oil passing through the meter-in passages 25a or 26a of each directional control valve 25 or 26. The hydraulic oil that has passed through the throttle-bypass passages 25 b and 26 b of the directional control valves 25 and 26 is not supplied to the hydraulic actuators 23 and 24 but is returned to the hydraulic oil tank 28 .

[0046] The first directional control valve 25 and the second directional control valve 26 are operated by a first operating device 41 and a second operating device 42, respectively. The first operating device 41 and the second operating device 42, respectively, instruct the operation of the first hydraulic actuator 23 and the second hydraulic actuator 24 through operator operation, and include, for example, operating levers 41a and 42a for the operator to operate. The first operating device 41 and the second operating device 42 are configured, for example, to function as pressure reducing valves that reduce the hydraulic pressure of a pressure source (a pilot pump not shown) to generate an operating pilot pressure corresponding to the amount of operation. The operating pilot pressure corresponding to the amount of operation generated by each operating device 41 and 42 acts on the valve spool of each directional control valve 25 and 26, thereby generating a valve spool stroke of each directional control valve 25 and 26 corresponding to the magnitude of the operating pilot pressure.

[0047] The relationship between the inlet meter-out opening area and the bypass meter-out opening area and the valve core stroke of each directional control valve 25, 26 is as follows: Figure 3 As shown in the characteristic diagram. Figure 3 In FIG. 1 , the horizontal axis S represents the valve core stroke of the directional control valves 25 and 26 , and the vertical axis A represents the meter-in opening area and the throttle-bypass opening area of the directional control valves 25 and 26 .

[0048] When the operating levers 41a and 42a are in neutral, that is, when the amount of operation of the operating levers 41a and 42a is zero, the valve spool stroke of the directional control valves 25 and 26 is zero (the valve spools are in the neutral position). At this time, the bypass meter-out opening area of the directional control valves 25 and 26 is maximum (the bypass meter-out passages 25b and 26b are fully open), while the meter-in opening area is zero (the meter-in passages 25a and 26a are fully closed). Therefore, the hydraulic actuators 23 and 24 corresponding to the directional control valves 25 and 26 are not driven.

[0049] In the range where the operating amount of the operating levers 41a and 42a is small, the valve spool stroke also decreases in accordance with the operating amount. In accordance with the valve spool stroke (operation amount), the meter-out opening area decreases, while the meter-in opening area increases. Consequently, a portion of the hydraulic oil from the hydraulic pump 22 flows into the hydraulic actuators 23 and 24 via the meter-in passages 25a and 26a of the directional control valves 25 and 26, while the remaining hydraulic oil returns to the hydraulic oil tank 28 via the meter-out passages 25b and 26b.

[0050] When the operating levers 41a and 42a are operated to their maximum value (full operation), the valve spool stroke reaches its maximum value based on the maximum operating value. At this point, the meter-in opening area is zero (meter-in passages 25b and 26b are fully closed), while the meter-in opening area is at its maximum value. Consequently, the entire amount of hydraulic oil from the hydraulic pump 22 flows through the meter-in passages 25a and 26a to the hydraulic actuators 23 and 24, while the flow rate of hydraulic oil returning to the hydraulic oil tank 28 is zero.

[0051] A central bypass cut valve (hereinafter referred to as a CB cut valve) 31 is provided between the second directional control valve 26 at the far downstream end of the intermediate bypass line 29 and the hydraulic oil tank 28. The CB cut valve 31 is capable of continuously changing its opening area and is comprised of, for example, a proportional solenoid valve. The opening (opening area) of the CB cut valve 31 is controlled by control commands from the machine controller 60. Together with the first directional control valve 25 and the second directional control valve 26, the CB cut valve 31 regulates the flow rate of hydraulic oil flowing from the hydraulic pump 22 through the intermediate bypass line 29 to the hydraulic oil tank 28, a so-called bypass throttling flow rate.

[0052] A first stroke sensor 51 and a second stroke sensor 52 are provided on the first hydraulic actuator 23 and the second hydraulic actuator 24, respectively. The first stroke sensor 51 and the second stroke sensor 52 detect the stroke of the first hydraulic actuator 23 and the stroke of the second hydraulic actuator 24, respectively, and output detection signals corresponding to the detected strokes of the first hydraulic actuator 23 and the second hydraulic actuator 24 to the machine controller 60.

[0053] The operating pilot pressures generated by the first operating device 41 and the second operating device 42 are detected by a first pressure sensor 53 and a second pressure sensor 54, respectively. The first pressure sensor 53 and the second pressure sensor 54 output detection signals corresponding to the detected operating pilot pressures to the machine controller 60. The first pressure sensor 53 and the second pressure sensor 54 function as operation amount detectors that detect the operation amounts of the first operating device 41 and the second operating device 42, respectively. A third pressure sensor 55 is provided in the discharge line 27 to detect the discharge pressure of the hydraulic pump 22. The third pressure sensor 55 outputs a detection signal corresponding to the detected discharge pressure to the machine controller 60.

[0054] The engine 21 is provided with a rotation speed sensor 56 that detects the actual rotation speed of the engine 21. The rotation speed sensor 56 outputs a detection signal corresponding to the detected actual rotation speed to the engine controller 58.

[0055] The engine controller 58 is configured to be able to communicate with the machine controller 60. The engine controller 58 receives the target speed of the engine 21 from the machine controller 60 and transmits the actual speed of the engine 21 input from the speed sensor 56 to the machine controller 60. The engine controller 58 calculates a command value for the fuel injection amount so that the actual speed of the engine 21 detected by the speed sensor 56 matches the target speed from the machine controller 60, and outputs the resulting command value to the injection device 21a.

[0056] The machine controller 60 is electrically connected to an engine control dial (hereinafter referred to as an EC dial) 43. The EC dial 43 indicates a set speed of the engine 21 according to an operator's operation and outputs an instruction signal of the set speed to the machine controller 60.

[0057] The machine controller 60 determines the target speed of the engine 21 based on the speed setting from the EC dial 43, the operation of the operating devices 41 and 42, and the like, and outputs the determined target speed to the engine controller 58. Specifically, the machine controller 60 controls the speed of the engine 21 via the engine controller 58. Furthermore, the machine controller 60 controls the opening (opening area) of the CB shutoff valve 31 and the pump capacity (discharge flow rate) of the hydraulic pump 22 based on the state of operation of the first hydraulic actuator 23 and the second hydraulic actuator 24.

[0058] Next, use Figure 4 The hardware configuration and functional configuration of the machine controller constituting the first embodiment of the working machine according to the present invention will be described. Figure 4 This is a block diagram showing the functional configuration of a controller constituting a part of the first embodiment of the working machine according to the present invention.

[0059] The control of the opening degree (opening area) of the CB cutoff valve 31 and the control of the pump capacity (discharge flow rate) of the hydraulic pump 22 by the machine controller 60 are based on the following viewpoints.

[0060] In recent years, improvements in the spool structure (the relationship between the spool opening area and the spool stroke) of fully open-center directional control valves in working machinery have reached a limit in reducing throttle losses. This is because, in the micro-operation range (the operating range where the operating device's operating amount is small), where the spool stroke is small, a relatively large throttle opening area is required to ensure operability during startup and slow speeds of the hydraulic actuator. Therefore, further reductions in the throttle opening area are difficult in this micro-operation range, hindering further reductions in throttle losses.

[0061] Therefore, first, consider dividing the period during which micro-manipulations of the hydraulic actuator are performed into a first period, a transition period during which the hydraulic actuator's driving state transitions from a static state to a start-up state, resulting in an unstable state, and a second period after the first period, during which the hydraulic actuator's driving state remains stable and in smooth motion. During the first period, factors that negatively impact operability, such as shock and stick-slip during the hydraulic actuator's startup, must be considered. Therefore, prioritizing operability requires a relatively large bypass flow rate. In contrast, during the second period, the hydraulic actuator has already begun moving and reached a stable driving state, reducing the impact of these factors that negatively impact operability. Therefore, a relatively large bypass flow rate is not necessarily required.

[0062] The control of the CB shutoff valve 31 by the machine controller 60 incorporates the above-mentioned concept. In brief, during the second period of micro-manipulation of the hydraulic actuators 23 and 24, the throttle flow rate is reduced by narrowing (decreasing) the opening (opening area) of the CB shutoff valve 31. This reduces throttle losses. Meanwhile, during the first period of this micro-manipulation, the opening (opening area) of the CB shutoff valve 31 is not narrowed but remains fully open, maintaining the throttle flow rate as before. This prevents a reduction in operability.

[0063] Specifically, in Figure 4 The hardware configuration of the machine controller 60 includes, for example, a storage device 61 composed of a RAM, a ROM, or the like, and a processing device 62 composed of a CPU, an MPU, or the like. The storage device 61 pre-stores various information, including programs required for controlling the CB shutoff valve 31 and the hydraulic pump 22. The processing device 62 appropriately reads the programs and various information from the storage device 61 and executes processing according to the programs, thereby realizing various functions, including the following functions.

[0064] The machine controller 60 includes, as functions executed by the processing device 62 , a micro-operation period determination unit 71 , a shutoff valve control unit 72 , and a pump capacity control unit 73 .

[0065] The micro-operation period determination unit 71 determines whether the operation of the first or second hydraulic actuator 23, 24 is a micro-operation within a predetermined range representing a micro-operation region, and whether the micro-operation continues for a predetermined period. This determination targets the hydraulic actuator 23, 24, or the second hydraulic actuator that has performed a relatively large operation; the hydraulic actuator that has performed a relatively small operation is not considered. The predetermined micro-operation period corresponds to the first period described above, which assumes the transition period when the first or second hydraulic actuator 23, 24 transitions from a static state to an activated state due to the initiation of the micro-operation, resulting in an unstable driving state. On the other hand, the period during which the micro-operation continues for a period exceeding the predetermined period corresponds to the second period described above, which assumes the period during which the first or second hydraulic actuator 23, 24 is smoothly driven and in a stable driving state after being activated.

[0066] Specifically, the micro-operation period determination unit 71 first determines whether the operation of the hydraulic actuators 23 and 24 is a micro-operation state. For example, this determination is made based on whether the amount of operation of the first operating device 41 or the second operating device 42 is within a predetermined range indicating a micro-operation. Specifically, the micro-operation period determination unit 71 determines whether the pilot pressure P1 of the first operating device 41 or the pilot pressure P2 of the second operating device 42 (the amount of operation of the first operating device 41 or the second operating device 42) detected by the first pressure sensor 53 or the second pressure sensor 54 (the amount of operation of the first operating device 41 or the second operating device 42) is within a predetermined range indicating a micro-operation. This determination is made based on whichever pilot pressure (the amount of operation) is greater, detected by the first pressure sensor 53 or the second pressure sensor 54. The predetermined range indicating a micro-operation state is, for example, a range greater than a predetermined first threshold value Pt1 and less than a predetermined second threshold value Pt2 (Pt2>Pt1). The first threshold value Pt1 and the second threshold value Pt2 are pre-stored in the storage device 61 and are, for example, 0.5 [MPa] and 2.5 [MPa], respectively. The first threshold value Pt1 is set to eliminate the insensitive region where the hydraulic actuators 23 and 24 are not driven even when the operating devices 41 and 42 are operated. The second threshold value Pt2 is the operating pilot pressure (operation amount) that defines the upper limit of the micro-operation region and is, for example, approximately 40% to 50% of the maximum operating pilot pressure (operation amount) during full operation of the operating devices 41 and 42.

[0067] Furthermore, when the micro-operation period determination unit 71 determines that the operation (operation amount) of the first operating device 41 or the second operating device 42 is in a micro-operation state within a predetermined range representing a micro-operation region, it measures the elapsed time t during which the micro-operation state has persisted and determines whether the measured elapsed time t exceeds a predetermined period (time threshold T0). The time threshold T0 is pre-stored in the storage device 61 and is, for example, 2 seconds. The micro-operation period determination unit 71 outputs the determination result of whether the elapsed time (duration) t of the micro-operation exceeds the time threshold T0 to the shutoff valve control unit 72 and the pump capacity control unit 73.

[0068] The shutoff valve control unit 72 controls the opening (opening area) of the CB shutoff valve 31 based on the determination result of the micro-operation period determination unit 71. Specifically, if the determination result of the micro-operation period determination unit 71 is "No," the shutoff valve control unit 72 outputs a valve control instruction to the CB shutoff valve 31 to fully open the CB shutoff valve 31. On the other hand, if the determination result of the micro-operation period determination unit 71 is "Yes," the shutoff valve control unit 72 outputs a valve control instruction to the CB shutoff valve 31 to gradually reduce (reduce) the opening (opening area) of the CB shutoff valve 31 over time, ultimately fully closing the CB shutoff valve 31. The rate of reduction in the opening area of the CB shutoff valve 31 is set from the perspective of preventing a decrease in the operability of the hydraulic actuators 23 and 24 during micro-operations due to a sudden decrease in the bypass throttle flow rate caused by the full closure of the CB shutoff valve 31.

[0069] The pump capacity control unit 73 controls the pump capacity of the hydraulic pump 22 based on the determination result of the micro-operation period determination unit 71. Specifically, the pump capacity control unit 73 pre-stores a table of reference pump capacities for operational pilot pressures, for example, and calculates reference pump capacities corresponding to the operational pilot pressures P1 and P2 of the first and second operating devices 41 and 42, respectively, as detected by the first and second pressure sensors 53 and 54, according to this table. If the determination result of the micro-operation period determination unit 71 is "No," the pump capacity control unit 73 outputs a pump control command to the regulator 22a, setting the calculated reference pump capacity as the target pump capacity.

[0070] On the other hand, if the determination result of the micro-operation period determination unit 71 is "yes," the pump capacity control unit 73 calculates a correction volume for reducing the pump capacity based on the decrease in the opening area of the CB shutoff valve 31 by the shutoff valve control unit 72. Furthermore, the pump capacity control unit 73 sets a target pump capacity such that the calculated base pump capacity is gradually reduced based on the calculated correction volume, and outputs a pump control command for the set target pump capacity to the regulator 22a.

[0071] Specifically, the pump capacity control unit 73 calculates the throttle flow rate Q when the CB cut valve 31 is fully opened based on the following relational expressions (1) and (2).

[0072]

[0073]

[0074] Here, Ab1 represents the throttle opening area of the first directional control valve 25, Ab2 represents the throttle opening area of the second directional control valve 26, As represents the combined opening area of the throttle openings of the first and second directional control valves 25, 26 connected in series with the intermediate bypass line 29, C represents the flow coefficient, P represents the discharge pressure of the hydraulic pump 22, and ρ represents the density of the fluid. The throttle opening areas Ab1 and Ab2 of the first and second directional control valves 25, 26 can be estimated based on the detection values (operating pilot pressures P1 and P2) detected by the first and second pressure sensors 53, 54, respectively. The discharge pressure P of the hydraulic pump 22 can be estimated using the detection value P3 detected by the third pressure sensor 55. The flow coefficient C and the density ρ of the fluid are preset constants.

[0075] Next, the pump capacity control unit 73 calculates a correction capacity by dividing the calculated throttle flow rate Q by the speed of the hydraulic pump 22, calculated based on the actual speed N of the engine 21 detected by the speed sensor 56. The throttle flow rate Q corresponds to the throttle flow rate reduced by switching the CB shutoff valve 31 from fully open to fully closed, and the calculated correction capacity corresponds to the pump capacity unnecessary when the CB shutoff valve 31 is switched to fully closed. During the switching time of the CB shutoff valve 31 from fully open to fully closed, which is set by the shutoff valve control unit 72, the pump capacity control unit 73 sets a target pump capacity that reduces the base pump capacity by the calculated correction capacity. Specifically, the pump capacity control unit 73 reduces the pump flow rate by an amount corresponding to the throttle flow rate Q reduced by the switching control of the CB shutoff valve 31 from fully open to fully closed. In particular, the pump capacity control unit 73 gradually reduces the pump capacity of the hydraulic pump 22 in conjunction with the shutoff valve control unit 72 gradually reducing the opening area of the CB shutoff valve 31.

[0076] Next, use Figure 5 A description will be given of a control process of the CB cutoff valve 31 and the hydraulic pump 22 by the machine controller constituting the first embodiment of the working machine according to the present invention. Figure 5 This is a flowchart showing an example of a control procedure of a controller constituting a part of the first embodiment of the working machine according to the present invention.

[0077] Figure 5 The machine controller 60 shown repeatedly controls the CB cutoff valve 31 and the hydraulic pump 22 (steps from start to return) at, for example, a predetermined control cycle Δt. This control process is started, for example, by turning on a key switch (not shown) to instruct the start of the hydraulic excavator.

[0078] First, the machine controller 60 (micro-operation period determination unit 71) determines whether the elapsed time t is 0 (t=0) (step S10). The elapsed time t is the time that has passed since the start of the micro-operation of the hydraulic actuators 23 and 24. The presence or absence of micro-operation is determined in step S30, which will be described later. The elapsed time t≠0 means that the operation on the hydraulic actuators 23 and 24 is a micro-operation state. On the other hand, the elapsed time t=0 means that no operation is being performed or that the operation exceeds the range of micro-operation. The elapsed time t at the beginning of the control cycle is set to 0.

[0079] If the determination in step S10 is "Yes" (elapsed time t = 0), the machine controller 60 (shutoff valve control unit 72) outputs a valve control command to the CB shutoff valve 31 to fully open the CB shutoff valve 31 (step S20), and the process proceeds to step S30. This causes the CB shutoff valve 31 to switch to a fully open state or maintain the fully open state. On the other hand, if the determination in step S10 is "No" (elapsed time t ≠ 0), the machine controller 60 skips step S20 and proceeds to step S30.

[0080] Next, the machine controller 60 (micro-operation period determination unit 71) determines whether the operation (operation amount) of the first operating device 41 or the second operating device 42 is within a predetermined range representing a micro-operation region (step S30). Specifically, it determines whether the pilot pressure of the first operating device 41 or the second operating device 42 detected by the first pressure sensor 53 or the second pressure sensor 54 is within a range greater than a first threshold value Pt1 and less than a second threshold value Pt2. This determination is made using the larger of the pilot pressures P1 and P2 detected by the first pressure sensor 53 or the second pressure sensor 54 (the operation amount of the first operating device 41 or the second operating device 42).

[0081] If the micro-operation period determination unit 71 determines "No" in step S30, that is, if the operation on the hydraulic actuators 23 and 24 is not a micro-operation, the process proceeds to step S100, where the elapsed time t is set to 0 (t=0). After executing step S100, the process returns to the beginning by returning to step S10 and executing step S30 again via steps S20. On the other hand, if the determination in step S30 is "Yes," that is, if the operation on the hydraulic actuators 23 and 24 is a micro-operation, the process proceeds to step S40.

[0082] In step S40 , the micro-operation period determination unit 71 starts or continues measuring the elapsed time t. Specifically, the elapsed time t is increased by one control cycle Δt. In other words, the micro-operation is continued during one control cycle Δt.

[0083] Next, the micro-operation period determination unit 71 determines whether the elapsed time t has reached the time threshold T0 (step S50). The elapsed time t reaching the time threshold T0 corresponds to the passage of the first period during the micro-operation described above. In other words, it is assumed that the hydraulic actuators 23 and 24 performing the micro-operation have transitioned from the unstable driving state at startup to a stable driving state. If the micro-operation period determination unit 71 determines "yes" in step S50, the process proceeds to step 60. On the other hand, if the determination is "no," step S60 is not executed and the process proceeds to step S70.

[0084] In step 60, the machine controller 60 (pump capacity control unit 73) calculates a correction capacity, and the process proceeds to step S70. As described above, this correction capacity is the pump displacement corresponding to the pump flow rate that is no longer required due to the reduction in the throttle flow rate Q caused by the switching of the CB cutoff valve 31 from fully open to fully closed. As described above, the correction capacity can be calculated based on the above-mentioned relationship equations (1) and (2) and the rotation speed of the hydraulic pump 22 (the rotation speed N of the engine 21).

[0085] Next, the machine controller 60 (micro-operation period determination unit 71) determines whether the elapsed time t exceeds the time threshold T0 (step S70). If the determination in step S70 is "No," the process returns to the beginning, and in step S10, it is again determined in step S30 whether the pilot pressure (operation amount) of the operating devices 41 and 42 is within the predetermined range indicating the micro-operation region (i.e., whether the operation of the hydraulic actuators 23 and 24 is a micro-operation state). While the micro-operation of the hydraulic actuators 23 and 24 continues, the machine controller 60 repeatedly executes steps S10, S30, S40, S50, and S70 in sequence. If the elapsed time t exceeds the time threshold T0, the determination in step S70 is "Yes," and the process proceeds to step S80.

[0086] In step S80, the machine controller 60 (shutoff valve control unit 72) outputs a valve control command to the CB shutoff valve 31 to reduce the opening area of the CB shutoff valve 31 by a predetermined amount during one control cycle Δt. The amount of reduction in the opening area of the CB shutoff valve 31 is calculated assuming that the CB shutoff valve 31 will switch from fully open to fully closed within a fixed period. Specifically, the shutoff valve control unit 72 gradually reduces the opening area of the CB shutoff valve 31 as the elapsed time t of the micro-operation of the operating devices 41 and 42 (micro-operation of the hydraulic actuators 23 and 24) increases.

[0087] Next, the machine controller 60 (pump capacity control unit 73) outputs a pump control command to the regulator 22a to reduce the base pump capacity of the hydraulic pump 22 (the capacity corresponding to the pilot pressures P1 and P2 of the first and second operating devices 41 and 42) by a predetermined amount during the control period Δt (step S90). This command gradually reduces the pump capacity of the hydraulic pump 22 in conjunction with a decrease in the opening area of the CB shutoff valve 31. The amount of pump capacity reduction is set so that the base pump capacity is reduced by the correction capacity calculated in S60 during the period (a fixed period) when the CB shutoff valve 31 switches from fully open to fully closed. After executing step S90, the machine controller 60 returns to the start.

[0088] If the micro-operation of the operating devices 41 and 42 (micro-operation of the hydraulic actuators 23 and 24) continues for a predetermined period (time threshold T0), the machine controller 60 repeatedly executes steps S10, S30, S40, S50, S70, S80, and S90. This causes the CB shutoff valve 31 to gradually switch from fully open to fully closed, maintaining this fully closed state until the micro-operation is completed. Furthermore, the pump flow rate of the hydraulic pump 22 gradually decreases in response to the switching control of the CB shutoff valve 31 to fully close, ultimately reaching a flow rate that is reduced by the bypass throttle flow rate when the CB shutoff valve 31 is fully open, and this state is maintained until the micro-operation is completed.

[0089] use Figures 5 to 7 The behavior of the directional control valve, CB stop valve, and hydraulic pump during full operation and micro-operation in the first embodiment of the working machine of the present invention will be described. Figure 5 as well as Figure 6 Describes the behavior of each device during full operation. Figure 6 This is a diagram showing an example of temporal behavior of each component of the hydraulic system in the first embodiment of the working machine according to the present invention during full operation.

[0090] Figure 6 The top diagram shows the operating devices 41 and 42 (see Figure 2) is continued for a certain period of time. The operation amount (operation) of the operating devices 41, 42 reaches a maximum value (full operation) that significantly exceeds the second threshold value Lt2 after exceeding the first threshold value Lt1 from 0 when stopped to time tf1. The full operation is maintained for a certain period of time and ends at a time point that exceeds time tf2. The first threshold value Lt1 represents the upper limit of the insensitive zone, and corresponds to the first threshold value Pt1 of the operating pilot pressure. When the operation amount of the operating devices 41, 42 is below the first threshold value Lt1, the hydraulic actuators 23, 24 are not driven even if the operating devices 41, 42 are operated. In addition, the second threshold value Lt2 represents the upper limit of the area of micro-operation related to the operation amount of the operating devices 41, 42, and corresponds to the second threshold value Pt2 of the operating pilot pressure.

[0091] At this time, the directional control valves 25 and 26 (see Figure 2 ) The valve core is moved to the maximum by the operating pilot pressure generated corresponding to the full operation of the operating devices 41 and 42. Figure 6 As shown in the middle diagram of , the throttle opening area of the directional control valves 25 and 26 is reduced from the maximum value when the operation stops to 0. When the full operation is completed, the valve core returns to the neutral position, whereby the throttle opening area returns to the maximum value.

[0092] On the other hand, during the full operation, the CB shutoff valve 31 (see Figure 2 ) is maintained fully open by the machine controller 60. Figure 6 As shown in the middle section of the figure, the bypass throttling opening area of the CB stop valve 31 is maintained at the maximum value. This is based on the subsequent control processing of the body controller 60. When the operating devices 41 and 42 are fully operated, the operating pilot pressure detected by the pressure sensors 53 and 54 is greater than the second threshold value Pt2 mentioned above. Therefore, the body controller 60 Figure 5 In the control process shown, if a "No" is determined in step S30, the CB shutoff valve 31 is fully opened in step S20 after passing through steps S100 and S10. While the full operation is in progress, the machine controller 60 repeats steps S30, S100, S10, and S20 in sequence, so that the CB shutoff valve 31 remains fully open.

[0093] In addition, if Figure 6 As shown in the bottom diagram, the hydraulic pump 22 (refer to Figure 2 ) increases from the minimum pump flow rate when the operation is stopped to the pump flow rate corresponding to the full operation of the operating devices 41, 42. This pump flow rate is maintained during the continuation of the full operation.

[0094] Next, use Figure 5 as well as Figure 7 The behavior of each device during micro-operation is explained. Figure 7This is a diagram showing an example of temporal behavior during micro-manipulation of each component of the hydraulic system in the first embodiment of the working machine according to the present invention.

[0095] Figure 7 The upper diagram shows the operating devices 41 and 42 (see Figure 2 ) continues for a certain period. The operation amounts of the operating devices 41 and 42 are maintained within a range exceeding the first threshold value Lt1 and less than the second threshold value Lt2 from 0 when the operation stops until time tm1, and are terminated at a time point exceeding time tm4. When the operation amounts of the operating devices 41 and 42 are within a range exceeding the first threshold value Lt1 and less than the second threshold value Lt2, the operation of the operating devices 41 and 42 corresponds to a micro-operation of the hydraulic actuators 23 and 24.

[0096] At this time, the directional control valves 25 and 26 (see Figure 2 ) The valve core is moved according to the operating pilot pressure generated by the micro-operation of the operating devices 41 and 42. Figure 7 As shown in the middle section of the figure, the bypass throttling opening area decreases according to the movement of the valve core. If the micro-operation ends, the valve core returns to the neutral position accordingly, and the bypass throttling opening area returns to the maximum value.

[0097] On the other hand, Figure 7 As shown in the middle section of the figure, CB stop valve 31 (refer to Figure 2 ) The opening area is controlled by the body controller 60 according to the elapsed time of the micro-operation.

[0098] Specifically, from time tm1 to time tm2, the CB shutoff valve 31 is maintained fully open as when the operation is stopped. The period from time tm1, which corresponds to the start time of the micro-operation (the time when the operation amount of the operating devices 41 and 42 reaches the first threshold value Lt1, that is, the time when the operation pilot pressure detected by the pressure sensors 53 and 54 reaches the first threshold value Pt1) to time tm2 corresponds to Figure 5 The time threshold T0 in steps S50 and S70 of the control process shown is used. This period assumes an unstable driving state when the hydraulic actuators 23 and 24 are started. During this period, if the hydraulic oil flows rapidly into the hydraulic actuators 23 and 24, the operator may sometimes feel the shock of the hydraulic actuators 23 and 24 starting up. In addition, stick-slip caused by friction may have a significant impact on operability. Therefore, during this period, the CB shut-off valve 31 is maintained fully open to ensure a relatively large bypass throttling flow rate. During this period, the bypass throttling opening area on the intermediate bypass line 29 is determined only by the bypass throttling opening area of the first directional control valve 25 and the bypass throttling opening area of the second directional control valve 26.

[0099] If the micro-operation continues even after time tm2, the opening area of the CB shut-off valve 31 decreases, and the CB shut-off valve 31 eventually switches from fully open to fully closed. Thereafter, the CB shut-off valve 31 remains fully closed until time tm4, when the micro-operation ends. After time tm2, it is assumed that the driving state of the hydraulic actuators 23 and 24 that have undergone the micro-operation is a state that reduces the adverse effects on operability during startup. Therefore, even if the opening of the CB shut-off valve 31 is reduced, the bypass throttling flow rate can be reduced without compromising the operability of the hydraulic actuators 23 and 24. However, the opening area of the CB shut-off valve 31 (the bypass throttling opening area) gradually decreases during a fixed period ΔTc from time tm2 to time tm3. This is to prevent a sudden change in the bypass throttling flow rate due to the reduction in the opening area of the CB shut-off valve 31, thereby preventing discomfort such as shock.

[0100] This is the next control process by the machine controller 60. The machine controller 60 Figure 5 In the control process shown, a "Yes" determination is made in step S30, a "Yes" determination is made in step S70, and a valve command is output to the CB shutoff valve 31 in step S80 to reduce the opening area of the CB shutoff valve 31. The machine controller 60 repeats steps S30, S70, and S80 multiple times per control cycle, thereby executing control to reduce the opening area of the CB shutoff valve 31.

[0101] Thus, during the micro-operation period from time tm2 to time tm4, the throttle opening area of the CB shutoff valve 31 decreases, thereby reducing the throttle flow rate accordingly. Consequently, throttle losses are reduced during the period from time tm2 to time tm4, achieving energy savings compared to the period from time tm1 to time tm2. Furthermore, when the CB shutoff valve 31 switches to fully closed during the fixed period ΔTc from time tm2 to time tm3, the opening of the CB shutoff valve 31 gradually decreases, thereby preventing a sudden decrease in the throttle flow rate caused by the closing of the CB shutoff valve 31. In other words, while the throttle flow rate is reduced by closing the CB shutoff valve 31, the operability of the hydraulic actuators 23 and 24 is not impaired.

[0102] However, if the throttle flow rate decreases due to the full closure of the CB shutoff valve 31, the discharge flow rate from the hydraulic pump 22 will flow into the hydraulic actuators 23 and 24 accordingly. In this case, even if the operation amount of the operating devices 41 and 42 is the same, the driving speed of the hydraulic actuators 23 and 24 will increase. Therefore, in order to maintain the same driving speed of the hydraulic actuators 23 and 24 during the reduction control of the CB shutoff valve 31, the operator needs to adjust the operation amount of the operating devices 41 and 42.

[0103] Therefore, if Figure 7 As shown in the lower figure, the hydraulic pump 22 (refer to Figure 2 ) is controlled to decrease in accordance with the decrease in the opening area of CB shutoff valve 31. Specifically, during a fixed period ΔTc from time tm2 to time tm3, the pump flow rate decreases from the flow rate corresponding to the micro-operation of operating devices 41 and 42 in conjunction with the decrease in the opening area of CB shutoff valve 31. From the time tm4 at which the micro-operation ends, the pump flow rate is maintained at the flow rate obtained by subtracting the throttle flow rate Q (calculated value of the aforementioned relational equation (1)) from the flow rate corresponding to the micro-operation.

[0104] This is the next control process by the machine controller 60. The machine controller 60 Figure 5 In the control process shown, if a "Yes" determination is made in step S30 and a "Yes" determination is made in step S70, a pump control command is output to the regulator 22a in step S90 to gradually reduce the pump capacity of the hydraulic pump 22. The amount of reduction in pump capacity is calculated based on the correction capacity calculated in step S60. The machine controller 60 executes the reduction control of the pump capacity of the hydraulic pump 22 by repeating steps S30, S70, and S80 multiple times in a control cycle.

[0105] In this way, at the same timing as the reduction control of the CB shutoff valve 31, the pump capacity of the hydraulic pump 22 is reduced by the amount of throttle flow caused by the reduction of the CB shutoff valve 31. Therefore, during micro-operations, the speeds of the hydraulic actuators 23 and 24 can be maintained substantially constant without changing the operation amounts of the operating devices 41 and 42. In other words, while achieving energy savings during micro-operations, a decrease in operability can be prevented.

[0106] As described above, the hydraulic excavator (working machine) of the first embodiment of the present invention includes: a hydraulic pump 22, which is driven by an engine 21 (prime mover); hydraulic actuators 23, 24, which are driven by hydraulic oil supplied from the hydraulic pump 22; an intermediate bypass line 29, one side of which is connected to the discharge side of the hydraulic pump 22 and the other side is connected to the working oil tank 28; center-fully-open directional control valves 25, 26, which are arranged on the intermediate bypass line 29 and control the flow of hydraulic oil supplied from the hydraulic pump 22 to the hydraulic actuators 23, 24; a CB shut-off valve 31, which is arranged between the directional control valve 26 on the intermediate bypass line 29 and the working oil tank 28; and a body controller 60 (control device) which controls the opening of the CB shut-off valve 31. The body controller 60 (control device) reduces the opening of the CB stop valve 31 when the operation of the hydraulic actuators 23 and 24 is in a micro-operation state within a predetermined range of the area representing the micro-operation and the micro-operation state continues for more than a predetermined period (T0). In other cases, that is, when the operation of the hydraulic actuators 23 and 24 is in a micro-operation state within a predetermined range of the area representing the micro-operation and the micro-operation state is less than a predetermined period (T0), the CB stop valve 31 is fully opened.

[0107] According to this configuration, during the initial stage of a micro-operation of the hydraulic actuators 23 and 24, the CB shutoff valve 31 does not reduce the throttle flow rate, thereby preserving the operability of the hydraulic actuators 23 and 24. Furthermore, after a predetermined period of micro-operation has elapsed, the throttle flow rate is reduced by reducing the opening of the CB shutoff valve 31, thereby achieving energy conservation. In other words, both operability and energy conservation can be achieved during micro-operation of the hydraulic actuators 23 and 24.

[0108] The hydraulic excavator (working machine) of the first embodiment also includes operating devices 41 and 42 for operating the hydraulic actuators 23 and 24. Furthermore, the machine controller 60 (control device) determines that the operation of the hydraulic actuators 23 and 24 is a micro-operation when the pilot pressure (operation amount) of the operating devices 41 and 42 is greater than a predetermined first threshold value Pt1 (Lt1) and less than a predetermined second threshold value Pt2 (Lt2). This configuration allows the determination of micro-operations of the hydraulic actuators 23 and 24 based on the pilot pressure (operation amount) of the operating devices 41 and 42 without providing a new detector. This avoids complicating the structure associated with controlling the CB shutoff valve 31 during micro-operations.

[0109] Furthermore, in this embodiment, when reducing the opening of the CB cutoff valve 31, the machine controller 60 (control device) gradually reduces the opening so that the CB cutoff valve 31 switches to a fully closed state over a fixed period ΔTc. This configuration prevents a sudden decrease in the throttle flow rate when controlling the reduction of the CB cutoff valve 31, thereby suppressing a decrease in the operability of the hydraulic actuators 23 and 24.

[0110] Furthermore, in this embodiment, the hydraulic pump 22 is configured with a variable pump capacity, and the machine controller 60 (control device) is configured to reduce the pump capacity of the hydraulic pump 22 in conjunction with the reduction in the opening of the CB shutoff valve 31. This configuration allows the speeds of the hydraulic actuators 23 and 24 to be maintained substantially constant without changing the amount of operation of the operating devices 41 and 42, even when energy is saved during micro-operations.

[0111] [Modification of the First Embodiment]

[0112] Next, use Figure 5 、 Figure 8 、 Figure 9 A modified example of the first embodiment of the working machine of the present invention will be described. Figure 8 This is a block diagram showing the functional configuration of a controller constituting a part of a modified example of the first embodiment of the working machine according to the present invention. Figure 9 1 is a diagram showing an example of the time-dependent behavior of each component of the hydraulic system during micro-operation in a modified example of the first embodiment of the working machine of the present invention. Figure 8 as well as Figure 9 In, with Figures 1 to 7 The same symbols are used to designate the same parts, and therefore their detailed description is omitted.

[0113] The modification of the first embodiment of the working machine of the present invention is different from the first embodiment in that: Figure 8 The micro-operation period determination unit 71A of the machine controller 60A shown in the figure has a different determination method. The other configurations are the same as those of the first embodiment.

[0114] As a method for determining whether an operation on the hydraulic actuators 23 and 24 is a micro-operation, the micro-operation period determination unit 71A of this modified example determines whether the drive speed of the first hydraulic actuator 23 or the second hydraulic actuator 24 is within a predetermined speed range representing a micro-operation. Specifically, for example, the micro-operation period determination unit 71A determines whether the drive speed of the first hydraulic actuator 23 or the second hydraulic actuator 24, determined based on the stroke S1 of the first hydraulic actuator 23 or the stroke S2 of the second hydraulic actuator 24 detected by the first stroke sensor 51 or the second stroke sensor 52, is within a predetermined speed range representing a micro-operation. The micro-operation period determination unit 71A receives the strokes S1 and S2 detected by the stroke sensors 51 and 52 for each control cycle and determines the temporal change in stroke, i.e., the actuator drive speed, based on the stroke during the most recent control cycle. This determination is made using the time-varying amount of stroke (drive speed) detected by the first stroke sensor 51 and the second stroke sensor 52, whichever has the larger detected value. The predetermined speed range representing the micro-operation region is, for example, a range greater than a predetermined first threshold value Vt1 and less than a predetermined second threshold value Vt2 (Vt2 > Vt1). The first and second threshold values Vt1 and Vt2 are pre-stored in the storage device 61 and are, for example, 10 mm / s and 100 mm / s, respectively. The first threshold value Vt1 is set to exclude stationary states of the hydraulic actuators 23 and 24. The second threshold value Vt2 is the drive speed of the hydraulic actuators 23 and 24 that defines the upper limit of the micro-operation region. In this modified example, the first and second stroke sensors 51 and 52 function as detectors for detecting information related to the drive speeds of the first and second hydraulic actuators 23 and 24, respectively.

[0115] The control procedure of the machine controller 60A with such a functional structure for the CB cutoff valve 31 and the hydraulic pump 22 is different from the control procedure of the machine controller 60 of the first embodiment in that: Figure 5 The control process shown is different in step S30 , but the processes in other steps are the same as those in the first embodiment.

[0116] exist Figure 5In step S30 shown, it is determined whether the operation on the hydraulic actuators 23 and 24 is in a micro-operation state. In the first embodiment, as one processing method for this determination, a method is used to determine whether the operation (operation amount) of the operating devices 41 and 42 is within a predetermined range of the area representing the micro-operation. In detail, the micro-operation period determination unit 71 determines whether the operation pilot pressures P1 and P2 of the operating devices 41 and 42 detected by the pressure sensors 53 and 54 are within a range greater than the first threshold value Pt1 and less than the second threshold value Pt2. In contrast, in this modified example, as another processing method for this determination, a method is used to determine whether the driving speed of the first hydraulic actuator 23 or the second hydraulic actuator 24 is within a predetermined speed range of the area representing the micro-operation. Specifically, the micro-operation period determination unit 71A determines whether the time variation of the stroke S1 or S2 of the first hydraulic actuator 23 or the second hydraulic actuator 24 detected by the first stroke sensor 51 or the second stroke sensor 52 (driving speed) is within a range greater than a first threshold value Vt1 and less than a second threshold value Vt2. This determination is made using the value of the relatively larger time variation of the stroke S1 or S2 of the first hydraulic actuator 23 or the second hydraulic actuator 24 detected by the first stroke sensor 51 or the second stroke sensor 52.

[0117] The behavior of the CB cutoff valve 31 and the hydraulic pump 22 during micro-operation in this modification differs from that of the first embodiment in the following points. The start timing of the reduction control of the opening degree (opening area) of the CB cutoff valve 31 is not from the start timing of the operating devices 41 and 42 (see Figure 2 ) reaches the first threshold value Lt1, a predetermined period (time threshold value T0) has passed since the time tm1 (refer to the time tm2 of the operation amount). Figure 7 ), but rather Figure 9 As shown in FIG. 1 , the time tm2a is changed to the time tm1a when the predetermined period (time threshold T0) has passed since the time tm1a when the driving speed of the hydraulic actuators 23 and 24 reaches the first threshold value Vt1. The start time of the reduction control of the pump flow rate of the hydraulic pump 22 is also changed to the time tm2a in accordance with the change in the start time of the reduction control of the CB shutoff valve 31. In addition, the end time of closing the CB shutoff valve 31 is not the time tm4 (see FIG. 1 ) when the operation amount of the operating devices 41 and 42 decreases to the first threshold value Lt1. Figure 7 ), but rather Figure 9 As shown, the time tm4a at which the driving speed of the hydraulic actuators 23 and 24 decreases to the first threshold value Vt1 is changed.

[0118] According to the modified example of the first embodiment described above, similar to the first embodiment, the CB cutoff valve 31 does not reduce the throttle flow rate during the initial stage of a micro-operation of the hydraulic actuators 23 and 24. Therefore, the operability of the hydraulic actuators 23 and 24 is not impaired. Furthermore, the throttle flow rate is reduced by reducing the opening of the CB cutoff valve 31 after a predetermined period of micro-operation has elapsed, thereby achieving energy conservation. In other words, both operability and energy conservation can be achieved during micro-operations of the hydraulic actuators 23 and 24.

[0119] The hydraulic excavator (working machine) according to the modified example of the first embodiment further includes stroke sensors 51 and 52 (detectors) that detect the stroke (information related to the drive speed) of the hydraulic actuators 23 and 24. Furthermore, the machine controller 60A (control device) determines that the operation on the hydraulic actuators 23 and 24 is a micro-operation when the temporal change in the stroke (drive speed) of the hydraulic actuators 23 and 24, obtained based on the stroke (information) detected by the stroke sensors 51 and 52 (detectors), is greater than a predetermined first threshold value Vt1 and less than a predetermined second threshold value Vt2. This configuration determines whether the operation on the hydraulic actuators 23 and 24 is a micro-operation based on the actual drive speed of the hydraulic actuators 23 and 24. This makes it possible to reliably detect the unstable drive state of the hydraulic actuators 23 and 24, i.e., the start-up period.

[0120] [Second embodiment]

[0121] Next, use Figure 10 A second embodiment of the working machine of the present invention will be described. Figure 10 1 is a block diagram showing the functional structure of a controller constituting a part of the second embodiment of the working machine of the present invention. Figure 10 In, with Figures 1 to 9 The same symbols are used to designate the same parts, and therefore their detailed description is omitted.

[0122] The second embodiment of the working machine of the present invention is different from the first embodiment in that Figure 10 As shown, the hydraulic excavator further includes a control mode selection device 45, and the machine controller 60B cannot execute the above-mentioned control of the CB cutoff valve 31 and the hydraulic pump 22 according to the output (instruction signal) of the control mode selection device 45. The other structures are the same as those of the first embodiment.

[0123] Specifically, the control mode selection device 45 selects, based on an operator's operation, either a first control mode in which the machine controller 60 of the first embodiment can execute control of reducing the opening of the CB shutoff valve 31 and reducing the pump volume of the hydraulic pump 22, or a second control mode in which the first control mode cannot be executed. The control mode selection device 45 is, for example, located in the cab 15 and can be comprised of a switch for selecting either the first control mode or the second control mode. Alternatively, it can be comprised of a touch panel that allows selection of the first control mode or the second control mode via an interface on a display screen. The control mode selection device 45 is electrically connected to the machine controller 60B and outputs an instruction signal to the machine controller 60B instructing it to execute either the first control mode or the second control mode selected by the operator's operation.

[0124] As described above, the first control mode aims to balance operability and energy conservation during micro-operations. On the other hand, the second control mode prioritizes operability during micro-operations. In the first control mode, the throttle flow rate is reduced by closing the CB shutoff valve 31 during micro-operations, potentially impacting operability slightly. Furthermore, depending on the operation, operability may be prioritized over improved energy conservation. In such cases, the operator's selection of the second control mode disables the execution of the first control mode.

[0125] The machine controller 60B of the second embodiment is configured to execute a selected control mode between the first and second control modes based on an instruction signal from the control mode selection device 45. The first control mode is similar to the control of the opening of the CB cutoff valve 31 and the pump capacity of the hydraulic pump 22 executed by the machine controller 60 of the first embodiment described above. On the other hand, the second control mode disables the execution of the first control mode and maintains the CB cutoff valve 31 fully open at all times. Specifically, during the execution of the second control mode, even if the micro-operation of the hydraulic actuators 23 and 24 continues for more than a predetermined period, the CB cutoff valve 31 is not closed.

[0126] According to the second embodiment, when the machine controller 60B executes the first control mode, similar to the first embodiment, both operability and energy saving can be achieved during micro-manipulation of the hydraulic actuators 23 and 24 .

[0127] The hydraulic excavator of this embodiment further includes a control mode selection device 45 that selects either a first control mode or a second control mode based on an operator's operation. Furthermore, the machine controller 60B (control device) is configured to execute, based on the selection made by the control mode selection device 45, either a first control mode that allows for narrowing the opening of the CB shutoff valve 31 or a second control mode that prevents the first control mode and maintains the CB shutoff valve 31 fully open. This configuration allows the operator to select a control mode based on the situation, thereby choosing between balancing energy saving and operability or prioritizing operability.

[0128] [Other embodiments]

[0129] In addition, the present invention is not limited to this embodiment and includes various modifications. The above-mentioned embodiment is an embodiment described in detail to easily explain the present invention and is not limited to having all the structures described. A part of the structure of a certain embodiment can be replaced with the structure of another embodiment, and the structure of another embodiment can be added to the structure of a certain embodiment. In addition, for a part of the structure of each embodiment, other structures can also be added, deleted, or replaced.

[0130] For example, in the above-described embodiment, an example in which the present invention is applied to a hydraulic excavator is shown, but the present invention can be widely applied to various working machines such as hydraulic cranes and wheel loaders having a fully open center directional control valve.

[0131] In the above-described embodiment, the first and second operating devices 41 and 42 are hydraulically configured. However, the first and second operating devices can also be electrically configured. Electrical operating devices detect the direction and amount of operation using a potentiometer or the like and output electrical signals corresponding to the detected values to the machine controllers 60, 60A, and 60B. In other words, the operating devices function as operation amount detectors that detect the amount of operation of the operating devices. In this case, the machine controllers 60 and 60B of the first and second embodiments are configured to determine whether the operation of the hydraulic actuators 23 and 24 is a micro-operation based on the amount of operation detected by the operating devices, rather than the pilot pressure detected by the pressure sensors 53 and 54. Specifically, this determination is made based on whether the amount of operation detected by the operating devices is within a range greater than a first threshold value Lt1 and less than a second threshold value Lt2.

[0132] Furthermore, in the modified example of the first embodiment described above, the machine controller 60A illustrates an example configuration in which the machine controller 60A determines whether the operation on the hydraulic actuators 23 and 24 is a micro-operation based on the time variation in stroke (the drive speed of the hydraulic actuators 23 and 24) obtained based on the strokes S1 and S2 detected by the stroke sensors 51 and 52. However, instead of using the stroke sensors, the drive speeds of the hydraulic actuators, such as the boom cylinder 9, arm cylinder 10, and bucket cylinder 11, that drive the boom 6, arm 7, and bucket 8 constituting the front working device 1, can be calculated based on the posture information of the front working device 1 detected by angle sensors attached to the boom 6, arm 7, and bucket 8. In other words, the machine controller can calculate the drive speeds of the hydraulic actuators based on the posture information of the front working device 1 detected by the angle sensors, and determine whether the operation on the hydraulic actuators 23 and 24 is a micro-operation based on this drive speed.

[0133] In addition, in the above embodiment, for simplicity of description, the case where two directional control valves are connected in series on the intermediate bypass line 29 is described. In this case, the relatively larger value among the detection values detected by the two pressure sensors 53 and 54 or the stroke sensors 51 and 52 is used to determine whether the operation of the hydraulic actuators 23 and 24 is a micro-operation. In addition, the combined opening area As of the bypass throttle opening area is calculated using the above-mentioned relational expression (2). In contrast, when the number of directional control valves connected in series on the intermediate bypass line 29 is three or more, the maximum value among the multiple detection values detected by the multiple sensors is used to determine the micro-operation. In addition, the combined opening area As of the bypass throttle opening area can be calculated by adding the respective terms of the bypass throttle opening area Abn of each directional control valve, similar to relational expression (2).

[0134] Explanation of symbols

[0135] 21 Engine (prime mover), 22 Hydraulic pump, 23 First hydraulic actuator (hydraulic actuator), 24 Second hydraulic actuator (hydraulic actuator), 25 First directional control valve (directional control valve), 26 Second directional control valve (directional control valve), 28 Working oil tank, 29 Intermediate bypass line, 31 Intermediate bypass stop valve, 41 First operating device (operating device), 42 Second operating device (operating device), 45 Control mode selection device, 51 First stroke sensor (detector), 52 Second stroke sensor (detector), 60, 60A, 60B Machine body controller (control device).

Claims

1. A working machine, characterized in that: have: a hydraulic pump, which is driven by the prime mover; a hydraulic actuator driven by hydraulic oil supplied from the hydraulic pump; an intermediate bypass line having one side connected to the discharge side of the hydraulic pump and the other side connected to the working oil tank; a fully open-center directional control valve disposed on the intermediate bypass line and controlling the flow of hydraulic oil supplied from the hydraulic pump to the hydraulic actuator; an intermediate bypass shutoff valve disposed between the directional control valve and the working oil tank on the intermediate bypass line; and A control device controls the opening of the intermediate bypass stop valve, The control device performs the following control: When the hydraulic actuator is operated in a micro-operation state within a predetermined range indicating a micro-operation, i.e., a region in which the valve spool stroke is small, and this micro-operation state continues beyond a period in which the hydraulic actuator transitions from a stationary state to an activated state and the driving state of the hydraulic actuator is a smooth and stable state, the opening of the intermediate bypass shutoff valve is reduced; as well as When the operation of the hydraulic actuator is in a micro-operation state within a predetermined range of the area representing the micro-operation and the micro-operation state is in a transition period in which the hydraulic actuator is in an unstable state from a stationary state to a started state, the intermediate bypass shut-off valve is fully opened.

2. The working machine according to claim 1, characterized in that: The working machine further comprises: an operating device for operating the hydraulic actuator; The control device determines that the operation on the hydraulic actuator is the micro-operation state when the operation amount of the operating device is larger than a predetermined first threshold value and smaller than a predetermined second threshold value.

3. The working machine according to claim 1, characterized in that: The working machine further includes: a detector for detecting information related to the driving speed of the hydraulic actuator; The control device determines that the operation on the hydraulic actuator is the micro-operation state when the driving speed of the hydraulic actuator obtained based on the information detected by the detector is greater than a predetermined first threshold and less than a predetermined second threshold.

4. The working machine according to claim 1, wherein: When reducing the opening of the intermediate bypass cut valve, the control device gradually reduces the opening so that the intermediate bypass cut valve is switched to the fully closed state within a fixed period.

5. The working machine according to claim 1, characterized in that: The hydraulic pump is configured to be able to change the pump capacity. The control device reduces the pump capacity of the hydraulic pump in conjunction with the reduction in the opening degree of the intermediate bypass cut valve.

6. The working machine according to claim 1, wherein: The working machine further includes a control mode selection device that selects one of the first control mode and the second control mode according to an operation of an operator. The control device executes one of the first control mode and the second control mode according to the selection of the control mode selection device, wherein the first control mode is a mode capable of executing a reduction control of the opening of the intermediate bypass stop valve, and the second control mode is a mode in which the first control mode cannot be executed and the intermediate bypass stop valve is maintained fully open.

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