Working machinery

Abstract

In the present invention, shock caused by frequent switching between a non-merging state and a merging state of pressure oil from two hydraulic pumps is suppressed.　This work machine comprises: a hydraulic drive device that includes a first hydraulic pump, a second hydraulic pump, a first hydraulic actuator, and a merging valve that merges pressure oil and causes communication with the first hydraulic actuator; an operation member; and a controller. The controller controls the merging valve so as to supply pressure oil from the first hydraulic pump to the first hydraulic actuator until the operation member reaches the first position from the initial position, controls the merging valve so as to supply the merged pressure oil to the first hydraulic actuator when the operation member is operated past the first position in a direction in which the operation amount increases, and controls the merging valve so as to supply pressure oil from the first hydraulic pump to the first hydraulic actuator when the operation member reaches a second position closer to the initial position than the first position from any position past the first position.

Description

Technical Field

[0001] The present invention relates to a working machine such as a hydraulic excavator.

Background Art

[0002] Generally, in a hydraulic system used in a working machine such as a hydraulic excavator, there are an actuator that operates with one of two hydraulic pumps as a supply source, and an actuator that operates with both as supply sources. In the actuator that operates with both as supply sources, from the viewpoint of reducing the loss of the flow dividing throttle, the priority order of the two hydraulic pumps is often determined in advance for each actuator.

[0003] In this type of hydraulic system, for example, the hydraulic pump assigned the first priority is determined in advance as the primary pump, and the hydraulic pump assigned the second priority is determined as the secondary pump. When the target flow rate is within the supplyable flow rate range of the primary pump, pressure oil is supplied to the actuator only from the primary pump. Only when the primary supplyable flow rate is exceeded, pressure oil is supplied to the actuator from the secondary pump.

[0004] At this time, when the pressure of the actuator to be merged is higher than the pressure of other actuators, the discharge pressure of the secondary pump varies depending on the presence or absence of merging. Therefore, when the target flow rate increases or decreases near the upper limit of the supplyable flow rate of the primary pump, there is a concern that repeated fluctuations in the discharge pressure accompanying the switching between the merged state and the non-merged state may cause operation shocks, a sense of discomfort in operation, instability of control, etc.

[0005] Therefore, in Patent Document 1, when the driving pressure, which is the difference between the rod-side pressure and the cap-side pressure of a hydraulic cylinder (actuator), is below a specified value, the first hydraulic pump and the second hydraulic pump are controlled to be in a connected state, thereby suppressing the occurrence of operation shocks caused by the switching between the connected state (merged state) and the non-connected state (non-merged state).

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Patent No. 6145229 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, in Patent Document 1, the controller controls the pump connection state depending on whether the required flow rate is above a certain threshold or whether the drive pressure is above a certain threshold. Therefore, if the required flow rate or drive pressure increases or decreases near the threshold, the switching between the merged state and the non-merged state may be repeated. As a result, when the drive pressure is high, the repeated switching between the merged state and the non-merged state may lead to an unnatural feeling during operation or instability of control. Furthermore, even under flow rate conditions where merging is not necessary, the merged state is maintained if the drive pressure is below a specified value. Therefore, during complex operations while the work machine is moving in the air (for example, when the boom and arm are operated simultaneously in the air), unnecessary throttling losses may occur, potentially leading to a deterioration in fuel efficiency.

[0008] The object of the present invention is to provide a work machine that can reduce flow throttling losses while suppressing shocks caused by frequent switching between non-combined and combined states of pressurized oil from two hydraulic pumps. [Means for solving the problem]

[0009] To achieve the above objective, one aspect of the present invention provides a work machine comprising: a hydraulic drive system including a first hydraulic pump, a second hydraulic pump, a first hydraulic actuator driven by pressurized oil supplied from the first hydraulic pump, and a confluence valve that combines the pressurized oil supplied from the first hydraulic pump and the second hydraulic pump and communicates them with the first hydraulic actuator; an operating member operated by an operator; and a controller that controls the hydraulic drive system based on the amount of operation of the operating member, wherein the controller supplies pressurized oil from the first hydraulic pump to the first hydraulic actuator when the operating member is operated in a direction that increases the amount of operation, until the operating member moves from an initial position to a first position. The merging valve is controlled in such a way (non-merging state), and when the operating member is operated beyond the first position in a direction that increases the operating amount, the merging valve is controlled to merge the pressurized oil from the second hydraulic pump with the pressurized oil from the first hydraulic pump, and to supply the merged pressurized oil to the first hydraulic actuator in accordance with the increase in the operating amount (merging state), and when the operating member is operated from any position beyond the first position in a direction that decreases the operating amount and reaches a second position that is closer to the initial position than the first position, the merging of the pressurized oil from the first hydraulic pump and the pressurized oil from the second hydraulic pump is released, and the merging valve is controlled to supply the pressurized oil from the first hydraulic pump to the first hydraulic actuator in accordance with the decrease in the operating amount. death (Non-merging state) The controller, when combining the pressurized oil from the first hydraulic pump with the pressurized oil from the second hydraulic pump, performs flow rate adjustment control by reducing the supply flow rate of pressurized oil from the first hydraulic pump to the first hydraulic actuator by a predetermined amount, and increasing the supply flow rate of pressurized oil from the second hydraulic pump to the first hydraulic actuator by the predetermined amount. It is characterized by the following: [Effects of the Invention]

[0010] The working machine according to the present invention can reduce flow throttling losses while suppressing shocks caused by frequent switching between non-combined and combined states of pressurized oil from two hydraulic pumps. Other issues, configurations, and effects will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0011] [Figure 1] This is a side view showing the external appearance of a hydraulic excavator. [Figure 2] A hydraulic circuit diagram showing a hydraulic system. [Figure 3] This is a functional block diagram of the controller. [Figure 4] This figure shows the changes in flow rate, pressure, and flow diversion throttling loss with respect to boom operation amount in conventional technology. [Figure 5] This figure shows the change in flow rate with respect to boom operation amount in the first embodiment. [Figure 6] This is a flowchart showing the control process steps of the controller. [Figure 7] This figure shows the change in flow rate with respect to boom operation amount in a modified example. [Figure 8] This is a flowchart showing the control process procedure of the controller according to the second embodiment. [Figure 9] This is a flowchart showing the control process procedure of the controller according to the third embodiment. [Modes for carrying out the invention]

[0012] (First Embodiment) Embodiments of the present invention will be described below with reference to the drawings.

[0013] Figure 1 is a side view showing the external appearance of a hydraulic excavator, which is an example of a work machine according to the present invention. In Figure 1, the hydraulic excavator 1 comprises a lower traveling body 3, an upper rotating body 2 that is rotatably mounted on the lower traveling body 3, and a driver's cab 10. The upper rotating body 2 is equipped with a boom 4, an arm 6, and a bucket 8 that constitute the front work machine, and is driven by hydraulic actuators, a boom cylinder 5, an arm cylinder 7, and a bucket cylinder 9, respectively. Attachments not shown can be attached to the hydraulic excavator 1.

[0014] Here, the boom cylinder 5 corresponds to the first hydraulic actuator of the present invention, and the arm cylinder 7 corresponds to the second hydraulic actuator of the present invention.

[0015] Figure 2 is a hydraulic circuit diagram of the hydraulic drive device HD mounted on the hydraulic excavator 1. Here, the circuit of the hydraulic system that drives the boom cylinder 5, the arm cylinder 7, the attachment 1 cylinder 24, and the attachment 2 cylinder 25 will be described.

[0016] The hydraulic drive device HD includes a controller 20 that controls the operation of the hydraulic actuators 5, 7, 24, 25, an operation lever 21 that sends an electrical signal to the controller 20, a first hydraulic pump 17 that supplies hydraulic oil to the hydraulic actuators 5, 7, 24, 25, a second hydraulic pump 18, a pilot pump 19 that supplies hydraulic oil to drive each switching valve, an engine 52 that drives the first hydraulic pump 17, the second hydraulic pump 18, and the pilot pump 19, a control valve 16 that controls the flow rate and direction of the hydraulic oil supplied to the hydraulic actuators 5, 7, 24, 25, and a hydraulic oil tank 26 that stores the hydraulic oil.

[0017] The operation lever (operation member) 21 is mounted in the cab 10 where the operator rides, and includes an operation lever that can be tilted forward, backward, left, and right, and a detection device that electrically detects an operation signal corresponding to the tilt amount (lever operation amount) of this operation lever. The lever operation amount detected by this detection device is output to the controller 20 via electrical wiring. That is, the operation of each hydraulic actuator 5, 7, 24, 25 is assigned to the front-back direction or the left-right direction of each operation lever of the operation lever 21.

[0018] [[ID=eleven]] The first hydraulic pump 17 and the second hydraulic pump 18 are driven by the engine 52, and discharge the hydraulic oil stored in the hydraulic oil tank 26 as pressure oil toward the hydraulic actuators 5, 7, 24, 25.

[0019] The pilot pump 19 is driven by the engine 52 together with the first hydraulic pump 17 and the second hydraulic pump 18, and discharges the hydraulic oil stored in the hydraulic oil tank 26 as pressure oil toward the switching valves 41, 42, 43. <0OO0100>

[0020] In this embodiment, electromagnetic proportional valves are exemplified as switching valves 41, 42, and 43, but other types of valves may be used. Also, although not shown in the figures, the switching valves and bleed-off valves of hydraulic actuators other than the boom cylinder 5, namely the arm cylinder 7, attachment 1 cylinder 24, and attachment 2 cylinder 25, are also switched by electromagnetic proportional valves.

[0021] The control valve 16 is located between the first hydraulic pump 17 and the second hydraulic pump 18, and the boom cylinder 5, arm cylinder 7, attachment cylinder 1 24, and attachment cylinder 2 25. The control valve 16 receives command signals from the controller 20 corresponding to the operating lever 21 and controls the supply, discharge, and stopping of pressurized oil to the boom cylinder 5, arm cylinder 7, attachment cylinder 1 24, and attachment cylinder 2 25.

[0022] The control valve 16 consists of pump junction valves 28, 29, 31, 32, 34, 35, 37, and 38 that control the supply flow rate from each hydraulic pump 17 and 18; directional control valves 27, 30, 33, and 36 that switch the direction of pressurized oil supplied from the pump junction valves 28, 29, 31, 32, 34, 35, 37, and 38 to each cylinder 5, 7, 24, and 25, and pressurized oil discharged from each cylinder 5, 7, 24, and 25 to the hydraulic oil tank 26; and bleed-off valves 39 and 40 that control the flow rate discharged from each hydraulic pump 17 and 18 to the hydraulic oil tank 26.

[0023] The control valve 16 has a first pump line 53 connected to the first hydraulic pump 17 and a second pump line 54 connected to the second hydraulic pump 18. The boom pump 1 junction valve 28, the arm pump 1 junction valve 31, the attachment 1 pump 1 junction valve 34, and the attachment 2 pump 2 junction valve 37 are connected in parallel to the first pump line 53. Similarly, the boom pump 2 junction valve 29, the arm pump 2 junction valve 32, the attachment 1 pump 2 junction valve 35, and the attachment 2 pump 2 junction valve 38 are connected in parallel to the second pump line 54.

[0024] Since the operation of each cylinder 5, 7, 24, and 25 is basically the same, the following will explain how to operate boom cylinder 5.

[0025] The boom pump 1 junction valve 28 is pilot-operated by an electromagnetic proportional valve 42 to control the supply flow rate from the first hydraulic pump 17 and direct pressurized oil to the downstream directional control valve 27. The boom pump 2 junction valve 29 is pilot-operated by an electromagnetic proportional valve 43 to control the supply flow rate from the second hydraulic pump 18 and direct pressurized oil to the downstream directional control valve 27. The controller 20 can control whether pressurized oil is supplied to the boom cylinder 5 only from the first hydraulic pump 17, only from the second hydraulic pump 18, or by combining the pressurized oil from the first hydraulic pump 17 and the second hydraulic pump 18 (switching control between combined and uncombined states).

[0026] The pressurized oil supplied from the hydraulic pumps 17 and 18 through the pump junction valves 28 and 29 is supplied to the bottom and rod sides of the boom cylinder 5 through the boom directional control valve 27. The pressurized oil discharged from the bottom side and the pressurized oil discharged from the rod side are then discharged to the hydraulic oil tank 22 through the boom directional control valve 27. This allows the boom cylinder 5 to extend and retract.

[0027] The solenoid proportional valve 41 is connected to the pilot pump 19 via a pilot primary pressure pipeline 55. The solenoid proportional valve 41 is also connected to a pilot oil chamber located at one end of the boom directional control valve 27 via a pilot secondary pressure pipeline 56. Similarly, the solenoid proportional valve 42 is connected to a pilot oil chamber located at one end of the boom pump 1 junction valve 28, and the solenoid proportional valve 43 is connected to a pilot oil chamber located at one end of the boom pump 2 junction valve 29.

[0028] When the operator moves the operating lever 21 from the initial position (neutral position) to the operating position, the controller 20 outputs a command signal corresponding to the amount of movement to the electromagnetic proportional valve 41 via the electromagnetic proportional valve command circuit 57. The electromagnetic proportional valve 41 then controls the pressure of the pilot pressure oil supplied from the pilot primary pressure pipeline 55 in response to the command signal. Furthermore, the pilot pressure oil whose pressure is controlled by the electromagnetic proportional valve 41 is supplied to and discharged from the pilot oil chamber of the boom directional control valve 27 via the pilot secondary pressure pipeline 56. Similarly, the pilot pressure oil is also supplied to and discharged from the pilot oil chambers of the boom pump 1 junction valve 28 and the boom pump 2 junction valve 29.

[0029] This drives the boom pump 1 junction valve 28, the boom pump 2 junction valve 29, and the boom directional control valve 27, thereby supplying and discharging pressurized oil to the boom cylinder 5.

[0030] Next, the functions of the controller 20 will be described. Figure 3 is a functional block diagram of the controller 20. As shown in Figure 3, the controller 20 includes a requested flow rate calculation unit 61, a pump dischargeable flow rate calculation unit 63, and a valve control unit 60.

[0031] The requested flow rate calculation unit 61 calculates the actuator's requested flow rate using the lever operation amount of the operating lever 21 as input, and outputs the actuator's requested flow rate to the valve control unit 60. Specifically, the requested flow rate calculation unit 61 calculates the actuator's requested speed from the lever operation amount, and then calculates the actuator's requested flow rate from that actuator's requested speed.

[0032] The pump discharge flow rate calculation unit 63 calculates the pump discharge flow rate using the pump pressure from the pump pressure sensors 49 and 50 as input, and outputs this pump discharge flow rate to the valve control unit 60. Specifically, the pump discharge flow rate calculation unit 63 calculates the maximum flow rate that the hydraulic pump can discharge, within a range that does not exceed a torque limit value determined based on the pump pressure.

[0033] The valve control unit 60 calculates the command current to each solenoid proportional valve for each spool valve using the actuator request flow rate, the pump dischargeable flow rate, and the boom pressure (actuator load pressure) from the boom pressure sensors 44A and 44B as input, and outputs the command current to each solenoid proportional valve.

[0034] The valve control unit 60 consists of a priority pump recording unit 64, a directional control valve control unit 66, a pump merging valve control unit 67, and a bleed-off valve control unit 68.

[0035] The priority pump recording unit 64 has the primary pump (first priority pump) set for each actuator 5, 7, 24, and 25. The primary pump settings should be set to a level that feels natural when considering standard usage. For example, as follows: (1) The two actuators that are used most frequently will have separate primary pumps. (Example: The primary pump for boom cylinder 5 is the first hydraulic pump 17, and the primary pump for arm cylinder 7 is the second hydraulic pump 18.) (2) Two actuators with high combined frequency will have separate primary pumps. (Example: The primary pump for bucket cylinder 9 is the first hydraulic pump 17, and the primary pump for arm cylinder 7 is the second hydraulic pump 18) (3) Do not connect actuators that tend to have high load pressure ranges when used in combination to the primary pump side of actuators that have a high flow rate frequency. (Example: Do not use the same hydraulic pump for boom raising and slewing.) (4) Actuators with similar load pressure zones shall use the same hydraulic pump. (Example: Boom lowering and bucket dumping shall use the first hydraulic pump 17.)

[0036] The directional control valve control unit 66 determines, based on the detected lever operation amount, whether to connect the bottom side or the rod side of the cylinder to the pump line, and outputs a command signal to the electromagnetic proportional valve for the directional control valve.

[0037] The pump junction valve control unit 67 calculates the actuator target flow rate and, as a breakdown, the target flow rate for pump 1 junction valve and the target flow rate for pump 2 junction valve, based on the actuator request flow rate, priority pump data, and pump dischargeable flow rate. It then outputs a command signal to the electromagnetic proportional valve for the junction valve so that the opening is adjusted according to the target flow rate.

[0038] The bleed-off valve control unit 68 outputs a command signal to the electromagnetic proportional valve for the bleed-off valve to discharge excess pump flow when an excess pump flow occurs relative to the actuator target flow rate.

[0039] Next, we will explain the control in actual operation.

[0040] When the operating lever 21 is operated in the boom operating direction, the requested flow rate calculation unit 61 calculates the boom requested flow rate (actuator requested flow rate) and outputs the boom requested flow rate to the valve control unit 60.

[0041] The pump discharge flow rate calculation unit 63 calculates the pump discharge flow rate of the first hydraulic pump 17 from the value of the pump pressure sensor 49 and the pump discharge flow rate of the second hydraulic pump 18 from the value of the pump pressure sensor 50, and outputs these pump discharge flow rates to the valve control unit 60.

[0042] The pump junction valve control unit 67 calculates the target flow rate of the actuator in the following manner. (1) Calculate the total value of the requested flow rates of the actuators that have received operation command signals. (2) Calculate the sum of the dischargeable flow rate of the first hydraulic pump 17 and the dischargeable flow rate of the second hydraulic pump 18. (3) The total pump discharge flow rate is divided by the total actuator required flow rate to calculate the flow rate reduction ratio. (4) The actuator target flow rate is calculated by multiplying the actuator's required flow rate by the flow rate reduction ratio.

[0043] Next, the pump merging valve control unit 67 retrieves the boom primary pump record from the priority pump recording unit 64. Since the primary pump for the boom cylinder 5 recorded is the first hydraulic pump 17, the pump merging valve control unit 67 first assigns the boom target flow rate to the boom pump 1 merging valve 28.

[0044] When the operating lever 21 is also operated in the arm operating direction, the pump junction valve control unit 67 calculates the target flow rate of the arm cylinder 7 in the same manner as the boom cylinder 5.

[0045] The pump merging valve control unit 67 retrieves the record of the arm primary pump from the priority pump recording unit 64. Since the primary pump of the recorded arm cylinder 7 is the second hydraulic pump 18, the pump merging valve control unit 67 first assigns the arm target flow rate to the arm pump 2 merging valve 32.

[0046] Next, the pump merging valve control unit 67 calculates the primary pump supplyable flow rate for each of the boom cylinder 5 and arm cylinder 7. Here, the boom primary pump supplyable flow rate is equal to the pump dischargeable flow rate of the first hydraulic pump 17, and the arm primary pump supplyable flow rate is equal to the pump dischargeable flow rate of the second hydraulic pump 18. If actuators with overlapping primary pump records are operated simultaneously, the primary pump supplyable flow rate for each actuator is calculated by sequentially subtracting the target flow rate of the actuator with the higher priority from the pump dischargeable flow rate, according to a predetermined priority order among the actuators.

[0047] Next, the changes in flow rate, pressure, and flow diversion throttling loss with respect to the boom operation amount in the present invention will be explained in comparison with the conventional technology.

[0048] First, let's explain the case of the conventional technology. Figure 4 shows the changes in flow rate, pressure, and flow diversion throttling loss with respect to the boom maneuver amount in the conventional technology. Note that the explanation assumes that the arm 6 maneuver amount is constant and the target flow rate of the arm cylinder 7 is also constant.

[0049] Figure 4(a) shows the boom target flow rate, the supply flow rate of the primary pump P1 (supply flow rate of the first hydraulic pump 17), and the supply flow rate of the secondary pump P2 (supply flow rate of the second hydraulic pump 18) in relation to the boom maneuver amount. When considering increasing the boom maneuver amount, the boom target flow rate is zero until a certain maneuver amount is reached. That is, no flow is supplied to the boom cylinder 5 from either the first hydraulic pump 17 or the second hydraulic pump 18. When the boom maneuver amount reaches a certain maneuver amount (B1), the boom target flow rate increases. At this point, since the boom target flow rate is smaller than the flow rate that can be supplied by the primary pump, the boom target flow rate can be supplied entirely from the primary pump, the first hydraulic pump 17. Therefore, the target flow rate of the boom pump 1 junction valve 28 becomes equal to the boom target flow rate, and the target flow rate of the boom pump 2 junction valve 29 is set to zero. As a result, the boom pump 1 junction valve 28 opens according to the target flow rate, and pressurized oil is supplied to the boom cylinder 5 through the boom directional control valve 27.

[0050] Figure 4(b) shows the target arm flow rate and the arm supply flow rate of the second hydraulic pump 18 in relation to the boom operation amount. Since the target arm flow rate is smaller than the flow rate that the primary pump can supply to the arm cylinder 7 (not shown), the entire target arm flow rate can be supplied by the second hydraulic pump 18, which is the primary pump. Therefore, the target flow rate of the arm pump 2 junction valve 32 is equal to the target arm flow rate, and the target flow rate of the arm pump 1 junction valve 31 is set to zero. As a result, the arm pump 2 junction valve 32 opens according to the target flow rate, and pressurized oil is supplied to the arm cylinder 7 through the arm directional control valve 30.

[0051] Figure 4(c) shows the pump 1 pressure (pressure of the first hydraulic pump 17), pump 2 pressure (pressure of the second hydraulic pump 18), boom pressure (pressure of the boom cylinder 5), and arm pressure (pressure of the arm cylinder 7) in relation to the boom operation amount. In this example, the boom pressure and arm pressure are constant. When pressurized oil is supplied to the boom cylinder 5 from the first hydraulic pump 17 and to the arm cylinder 7 from the second hydraulic pump 18, i.e., in a non-combined state, the pump 1 pressure is approximately equal to the boom pressure, and the pump 2 pressure is approximately equal to the arm pressure.

[0052] Figure 4(d) shows the flow diversion throttling loss with respect to the boom maneuver amount. In the aforementioned non-merging state, no flow diversion occurs in each pump line, so the flow diversion throttling loss is zero.

[0053] When the boom operation amount increases to operation amount B2, a shortage occurs in the supply flow rate from the first hydraulic pump 17, so a target flow rate for the shortage is set in the boom pump 2 merging valve 29. As a result, the boom pump 2 merging valve 29 opens according to the target flow rate, and the pressurized oil that has passed through the boom pump 1 merging valve 28 is merged and supplied to the boom cylinder 5. At this time, as shown in Figure 4(c), the pump 2 pressure rises to equal the pump 1 pressure in order to supply pressurized oil to the boom cylinder 5. In addition, the opening of the arm pump 2 merging valve 32 is narrowed in order to divide the flow to the boom cylinder 5 and the arm cylinder 7 in the second pump line 54. As a result, as shown in Figure 4(d), a narrowing loss occurs when the boom operation amount is B2.

[0054] Thus, when switching from a non-combined state to a combined state, or vice versa, fluctuations in pump discharge pressure and control of the opening amount of the merging valve may occur, and these can cause fluctuations in the actual flow rate supplied to the actuator. For example, if the lever operation is performed in small increments, and the target flow rate at that time is close to the primary pump's supplyable flow rate, the non-combined and combined states will switch frequently, raising concerns about operational shocks, operational discomfort, and control instability due to repeated fluctuations in pump discharge pressure. An example of an operation that involves small increments in the lever operation is, for example, putting sand into bucket 8 and sifting it.

[0055] Next, a first embodiment of the present invention will be described using Figures 5 and 6. Figure 5 shows the changes in the boom target flow rate, the supply flow rate of the primary pump P1 (first hydraulic pump 17), and the supply flow rate of the secondary pump P2 (second hydraulic pump 18) with respect to the boom operation amount. Note that the changes in arm flow rate, pressure, and throttling loss, which are not shown, are the same as in Figures 4(b), (c), and (d), where the arm flow rate, pump 1 pressure, boom pressure, and arm pressure are constant, and the pump 2 pressure and throttling loss change with the switching between the non-combined state and the combined state.

[0056] Figure 6 is a flowchart showing the control processing procedure by the controller 20. The process shown in Figure 6 is initiated, for example, by engine startup and is repeatedly executed at predetermined cycles (for example, every 1 millisecond). As described above, the process (S1 to S5) in Figure 6, in which the requested flow rate, target flow rate, and primary pump supplyable flow rate are sequentially calculated based on the actuator (Act) operation amount, is omitted in detail below. The processing from S6 onwards, which is a feature of the present invention, will be explained in detail below.

[0057] In S6, the pump junction valve control unit 67 determines the ON / OFF state of the primary pump dischargeable flow rate correction flag. The state of the correction flag is determined in S13 and S14, described below. The initial value of the correction flag is set to OFF. If the correction flag is OFF, the primary pump supplyable flow rate is not corrected (S8). If the correction flag is ON, the primary pump supplyable flow rate is corrected to be reduced by a certain amount (determined amount) (S7 / flow rate adjustment control).

[0058] In S9, the pump merging valve control unit 67 determines whether the target flow rate exceeds the primary pump's supplyable flow rate. If it does not, the non-merging state is reached, i.e., the secondary pump side pump merging valve is closed (S11). If it does exceed the target flow rate, the merging state is reached, i.e., the secondary pump side pump merging valve opens (S10). Here, the case where S9 is Yes is when the boom operation amount in Figure 5(a) exceeds X1.

[0059] If the systems are merged, in S12, it is determined whether the primary pump's insufficient flow rate is within the range of the secondary pump's available flow rate. If it is within the range, the correction flag is turned ON in S13. If it is not within the range, or if the systems are not merged, the correction flag is turned OFF.

[0060] Figure 5 illustrates the change in flow rate with respect to boom maneuver amount when the above control flow is applied. Figure 5(a) shows the case when the boom maneuver amount increases, and Figure 5(b) shows the case when the boom maneuver amount decreases. Q1 is the primary pump supplyable flow rate, and Q0 is the modified primary pump supplyable flow rate.

[0061] In Figure 5(a), as the boom operation amount increases from zero (initial position of the operating lever 21) until it reaches X1 (first position of the operating lever 21), the boom target flow rate does not exceed the primary pump supplyable flow rate Q1, so the control flow S9 determination is No, and the system remains in a non-merging state. When the boom operation amount exceeds X1, the boom target flow rate exceeds the primary pump supplyable flow rate Q1 (maximum flow rate of the primary pump), so the control flow S9 determination becomes Yes, and the system switches to a merging state. Furthermore, the correction flag is turned ON, and the primary pump supplyable flow rate is effectively reduced to Q0. As a result, the pump 1 supply flow rate (supply flow rate of the first hydraulic pump 17) decreases once the boom operation amount exceeds X1 and becomes constant, while the pump 2 supply flow rate (supply flow rate of the second hydraulic pump 18) increases in accordance with the increase in the target flow rate. Note that the value of Q1-Q0 (=ΔQ) in Figure 5(a) is the "determined amount" of the present invention.

[0062] By seemingly reducing the primary pump's supplyable flow rate, the primary pump's insufficient flow rate appears to increase. As long as the insufficient flow rate is within the secondary pump's supplyable flow rate range, the correction flag remains ON. However, when the boom operation amount reaches X2, the insufficient flow rate exceeds the range of the secondary pump's supplyable flow rate, resulting in a No determination in control flow S12 and the correction flag being turned OFF. As a result, the primary pump's supplyable flow rate returns to Q1, the pump 1 supply rate increases, and the insufficient flow rate decreases, thus reducing the pump 2 supply rate. At this point, there is a margin in the secondary pump's supplyable flow rate, so if the boom operation amount is further increased, the pump 2 supply rate will increase. In this way, even if a correction is made to reduce the primary pump's supplyable flow rate, the correction is released when the target flow rate approaches the limit of the total pump supplyable flow rate, and the total flow rate that can be supplied to the boom cylinder 5 can be reliably supplied by the first hydraulic pump 17 and the second hydraulic pump 18.

[0063] Next, we will explain the case where the boom maneuver amount decreases, as shown in Figure 5(b). When the boom maneuver amount decreases from the maximum state (any position beyond the first position X1 of the control lever 21) to X2, the insufficient flow rate falls within the range of the secondary pump's supplyable flow rate, and the correction flag is turned ON. The merging state is maintained even when the boom maneuver amount decreases further and falls below X1 (the first position). When the boom maneuver amount becomes even smaller and reaches X0 (the second position where the control lever 21 is closer to the initial position than the first position), and falls below X0, the boom target flow rate falls below the corrected primary pump supplyable flow rate Q0, so the control flow S9 determination becomes No, and the system switches to the non-merging state. At the same time, the correction flag is switched OFF.

[0064] Thus, when the boom control amount increases, the state switches between non-merged and merged at boom control amount X1, but when it decreases, the switch occurs at boom control amount X0. For example, even if the boom control amount is increased or decreased in small increments near X1, the merged state will be maintained as long as the boom control amount does not return to X0. This eliminates the switching between non-merged and merged states, preventing operational shocks, operational discomfort, and control instability caused by repeated fluctuations in pump discharge pressure.

[0065] The adjustment amount (determined amount) for the primary supplyable flow rate is set within a range that does not exceed the secondary supplyable flow rate. A smaller adjustment amount increases the frequency of switching between the non-combined and combined states, thereby reducing the flow diversion throttling loss. A larger adjustment amount decreases the frequency of switching between the non-combined and combined states, resulting in better operability. For example, it is preferable to arbitrarily set the adjustment amount within a range of approximately 1 / 4 to 1 / 2 of the secondary supplyable flow rate (the maximum flow rate that the second hydraulic pump 18 can supply).

[0066] (modified version) Figure 7 shows the relationship between boom operation amount and flow rate in the modified example. As shown in Figure 7, in the modified example, the correction amount for the boom operation amount is not constant but varies. Specifically, the supply flow rate of pump 1 gradually decreases once it exceeds the boom operation amount X1, while the supply flow rate of pump 2 gradually increases. Furthermore, when the boom operation amount reaches X2, the insufficient flow rate becomes equal to the supplyable flow rate of the secondary pump, and thereafter the correction amount gradually decreases so that the insufficient flow rate does not increase even if the target flow rate increases. As a result, both the supply flow rate of pump 1 and pump 2 increase. In this way, the change in the supply flow rate from each pump becomes smoother, and better operability is obtained. Needless to say, the change in the correction amount is within a range in which the primary pump insufficient flow rate calculated as a result of the correction does not exceed the supplyable flow rate of the secondary pump.

[0067] (Second embodiment) Next, a second embodiment of the present invention will be described with reference to Figure 8. Figure 8 is a flowchart showing the processing procedure of the controller according to the second embodiment. Note that in Figure 8, the processing of S102 to S108 is the same as S2 to S8 in Figure 6, so the details shown are omitted.

[0068] In the second embodiment, in S110, it is determined whether the load pressure of the target actuator (Act) is greater than that of all other actuators (Act) that receive flow from the secondary pump of the target actuator. Taking the first embodiment as an example, if the boom cylinder 5 is the target actuator, the other actuator that receives flow from the second hydraulic pump 18 (pump 2), which is the secondary pump of the boom cylinder 5, is the arm cylinder 7. Since the load pressure of the boom cylinder 5 is greater than the load pressure of the arm cylinder 7, S110 is determined to be Yes. In this case, the processing from S111 onward is the same as the processing from S10→S12→S13 in the first embodiment. That is, the primary pump supplyable flow rate is modified to be reduced by a certain amount (determined amount) (flow rate adjustment control).

[0069] On the other hand, if the determination in S110 is No, that is, if the load pressure of the boom cylinder 5 is less than the load pressure of the arm cylinder 7, the discharge pressure of the second hydraulic pump 18 (pump 2) will not change even if the boom cylinder 5 enters the merging state. In such cases, by turning OFF the primary pump supplyable flow rate correction flag (S116), it is possible to actively switch between the non-merging state and the merging state, thereby reducing the flow diversion throttling loss.

[0070] (Third embodiment) Next, a third embodiment of the present invention will be described with reference to Figure 9. Figure 9 is a flowchart showing the processing procedure of the controller according to the third embodiment. Note that in Figure 9, the processing of S202 to S208 is the same as S2 to S8 in Figure 6, so the details shown are omitted.

[0071] In the third embodiment, if in S210 it is determined that the load pressure of the target actuator (Act) is greater than that of all other actuators (Act) that receive flow from the secondary pump of the target actuator, then in S211 it is determined whether the load pressure of the target actuator (in this case, boom cylinder 5) is below a certain threshold. This threshold (limit value) is the value at which the pump tilt decreases due to horsepower control when the first hydraulic pump 17 (pump 1) and the second hydraulic pump 18 (pump 2) are at the same pressure, and in this embodiment, it is set to, for example, 15 MPa. In other words, when the system merges while exceeding this threshold and pumps 1 and 2 are at the same pressure, the pump dischargeable flow rate decreases, and the flow rate supplied to the actuator decreases.

[0072] If the load pressure of boom cylinder 5 is below this threshold, S211 is determined to be Yes, and the processing from S212 onward is the same as in the first embodiment. If the load pressure exceeds this threshold, the determination in S211 is No, and the boom does not enter the merging state (S212). This configuration prevents the situation where increasing the manipulative amount in an attempt to increase the supply flow rate to the actuator results in a decrease in the supply flow rate, causing an unnatural feeling during operation.

[0073] In this embodiment, the pump junction valve is provided separately from the directional control valve. However, it is also possible to provide a directional control valve in each of the multiple pump lines (as the pump junction valve in this invention) to control the supply flow rate from the pumps and to merge them downstream of the directional control valve. That is, it is also possible to use directional control valves 28 and 29 as junction valves and omit directional control valve 27.

[0074] Furthermore, while this embodiment describes a case where the target flow rate changes according to the manipulated amount, the present invention is also effective in other cases where the target flow rate changes. For example, in automatic control, the required flow rate is calculated directly from the required speed of the actuator, rather than from the manipulated amount, and the target flow rate is calculated from the required flow rate. Also, even if the required flow rate does not change, the target flow rate may change due to a change in the total value of the pump's dischargeable flow rate.

[0075] Furthermore, although this embodiment describes a case of combined operation in which multiple actuators are operated, the present invention is also effective in the case of single operation in which a single actuator is operated. In particular, the effects of the present invention can be obtained in situations where half-lever operation is required, such as in finishing work, regardless of whether it is a single or combined operation.

[0076] The embodiments described above are illustrative for explaining the present invention and are not intended to limit the scope of the present invention to those embodiments only. Those skilled in the art can implement the present invention in various other forms without departing from the spirit of the invention. [Explanation of Symbols]

[0077] 1…Construction machinery (working equipment) 2…Upper rotating body 3…Lower running body 4…Boom 5…Boom cylinder (first hydraulic actuator) 6... Arm 7…Arm cylinder (second hydraulic actuator) 8…Bucket 9… Bucket cylinder 10... Driver's cab 16…Control valve 17…First Hydraulic Pump 18…Second hydraulic pump 19…Pilot pump 20… Controller 21... Operating lever (operating component) 24... Attachment 1 Cylinder 25...Attachment 2 Cylinder 26... Hydraulic oil tank 27... Directional control valve for boom 28... Boom pump 1 junction valve (junction valve) 29... Boom pump 2 junction valve (junction valve) 30… Directional control valve for arm 31... Pump for arm, 1 junction valve 32... Pump for arm, 2 junction valves 33… Directional control valve for attachment 1 34... Pump 1 for attachment 1, junction valve 35... Pump 2 junction valve for attachment 1 36… Directional control valve for attachment 2 37... Pump 1 Junction Valve for Attachment 2 38... Pump 2 Junction Valve for Attachment 2 39... Pump 1 Bleed-off valve 40... Pump 2 bleed-off valve 41... Solenoid proportional valve for boom directional control valve 42...Boom pump 1 Solenoid proportional valve for junction valve 43... Solenoid proportional valve for boom pump 2 junction valve 44A... Boom rod pressure sensor 44B... Boom bottom pressure sensor 45A... Arm rod pressure sensor 45B... Arm bottom pressure sensor 46A... Attachment 1 Rod Pressure Sensor 46B... Attachment 1 Bottom Pressure Sensor 47A... Attachment 2-rod pressure sensor 47B... Attachment 2 Bottom Pressure Sensor 48...Mode selection dial 49...First pump pressure sensor 50...Second pump pressure sensor 52… Engine 53...First pump line 54... Second pump line 55…Pilot primary pressure pipeline 56…Pilot secondary pressure pipeline 57... Electromagnetic proportional valve command circuit 60…Valve control unit 61…Required flow rate calculation section 63... Pump discharge flow rate calculation unit 64…Priority Pump Recording Unit 66... ​​Directional control valve control unit 67... Pump junction valve control unit 68... Bleed-off valve control unit HD…Hydraulic drive system

Claims

1. A work machine comprising a hydraulic drive system including a first hydraulic pump, a second hydraulic pump, a first hydraulic actuator driven by pressurized oil supplied from the first hydraulic pump, a merge valve that combines the pressurized oil supplied from the first hydraulic pump and the second hydraulic pump and connects them to the first hydraulic actuator, an operating member operated by an operator, and a controller that controls the hydraulic drive system based on the amount of operation of the operating member, The aforementioned controller, When the operating member is operated in a direction that increases the amount of operation, the confluence valve is controlled to supply pressurized oil from the first hydraulic pump to the first hydraulic actuator while the operating member moves from the initial position to the first position. When the operating member is operated beyond the first position in a direction that increases the amount of operation, the pressurized oil from the second hydraulic pump is merged with the pressurized oil from the first hydraulic pump, and the merging valve is controlled to supply the merged pressurized oil to the first hydraulic actuator in accordance with the increase in the amount of operation. When the operating member is operated from any position beyond the first position in a direction that decreases the amount of operation, and reaches a second position that is closer to the initial position than the first position, the confluence of pressurized oil from the first hydraulic pump and the pressurized oil from the second hydraulic pump is released, and the confluence valve is controlled to supply pressurized oil from the first hydraulic pump to the first hydraulic actuator in accordance with the decrease in the amount of operation. The aforementioned controller, When combining the pressurized oil from the first hydraulic pump with the pressurized oil from the second hydraulic pump, flow rate adjustment control is performed to reduce the supply flow rate of pressurized oil from the first hydraulic pump to the first hydraulic actuator by a predetermined amount, and increase the supply flow rate of pressurized oil from the second hydraulic pump to the first hydraulic actuator by the predetermined amount. A work machine characterized by the following features.

2. In the work machine described in claim 1, The first position is set to the operating position of the operating member corresponding to the maximum flow rate that the first hydraulic pump can supply. A work machine characterized by the following features.

3. In the work machine described in claim 1, The predetermined amount is set in advance within the range of the flow rate that the second hydraulic pump can supply. A work machine characterized by the following features.

4. In the work machine described in claim 1, The system further comprises a second hydraulic actuator driven by pressurized oil supplied from the second hydraulic pump, The aforementioned controller, When combining the pressurized oil from the first hydraulic pump with the pressurized oil from the second hydraulic pump, the flow rate adjustment control is performed only when the pressure of the first hydraulic actuator is higher than the pressure of the second hydraulic actuator. A work machine characterized by the following features.

5. In the work machine described in claim 4, The aforementioned controller, When combining the pressurized oil from the first hydraulic pump with the pressurized oil from the second hydraulic pump, even if the pressure of the first hydraulic actuator is higher than the pressure of the second hydraulic actuator, if the pressure of the first hydraulic actuator exceeds the discharge pressure limit of the first hydraulic pump, the merging valve is controlled so as not to combine the pressurized oil from the first hydraulic pump with the pressurized oil from the second hydraulic pump. A work machine characterized by the following features.

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