Driving control device

Abstract

To appropriately limit an acceleration of a travel motor in accordance with difference in operation contents of right and left travel operation portions.SOLUTION: A travel device 11b includes a left travel device 11bL and a right travel device 11bR. A left travel operation portion 31L operates the left travel device 11bL. A right travel operation portion 31R operates the right travel device 11bR. A travel motor 26 drives the travel device 11b. A controller 40 controls the travel motor 26 in accordance with operation contents of the left travel operation portion 31L and the right travel operation portion 31R. The controller 40 determines difference between the operation contents of the left travel operation portion 31L and the operation contents of the right travel operation portion 31R, and changes a limit on an acceleration of the travel motor 26 according to the above-mentioned difference.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a travel control device that controls left and right travel devices. [Background technology]

[0002] For example, Patent Document 1 describes a conventional travel control device. In the invention described in this document, when the travel operation unit (travel operation lever in the document) is operated, a controller temporarily delays the response of the travel motor to the operation. This ensures that even if an erroneous operation is made on the travel operation unit, the construction machine will only move a small distance (see the abstract and paragraph 0013 of the specification of the document, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-319940 Summary of the Invention [Problem to be solved by the invention]

[0004] The invention described in the same document is equipped with left and right travel operation units (a left travel operation lever and a right travel operation lever in the same document). The need to limit the acceleration of the travel motor (delaying response in the same document) may vary depending on the difference in the operation content of the left and right travel operation units. However, the invention described in the same document does not take into account the difference in the operation content of the left and right travel operation units when limiting the acceleration of the travel motor. Therefore, the limit on the acceleration of the travel motor is left running It is desirable to impose restrictions according to the difference in operation content between the row operation unit and the right-travel operation unit.

[0005] Therefore, an object of the present invention is to provide a driving control device that can limit the acceleration of the driving motor appropriately according to the difference in the operation content of the left and right driving operation units. [Means for solving the problem]

[0006] The travel control device includes a travel device, a left travel operation unit, a right travel operation unit, a travel motor, and a controller. The travel device has a left travel device and a right travel device. The left travel operation unit is for operating the left travel device. The right travel operation unit is for operating the right travel device. The travel motor drives the travel device. The controller controls the travel motor according to the operation details of the left travel operation unit and the right travel operation unit. The controller determines a difference between the operation details of the left travel operation unit and the operation details of the right travel operation unit, and changes the acceleration limit of the travel motor according to the difference. [Effects of the Invention]

[0007] With the above configuration, the acceleration of the travel motor can be limited appropriately according to the difference in the operation of the left and right travel operation units. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a side view of a work machine 10 of a travel control device 1. FIG. [Figure 2] 2 is a diagram showing a hydraulic circuit 20 and the like of the travel control device 1 shown in FIG. [Figure 3] 3 is a graph showing changes in the displacement of pump 21 over time when the amount of change in pump displacement Δq of pump 21 shown in FIG. 2 is limited. [Figure 4] 3 is a graph showing changes in the displacement of pump 21 over time when the pump displacement change amount Δq of pump 21 shown in FIG. 2 is not limited. [Figure 5] 3 is a graph showing the relationship between the left and right operation amount difference D of the travel operation unit 31 shown in FIG. 2 and the upper limit value R of the pump displacement change amount Δq of the pump 21. [Figure 6] 3 is a graph showing the relationship between the pump rotation speed N of the pump 21 shown in FIG. 2 and the corrected upper limit value Ra of the pump displacement change amount Δq of the pump 21. [Figure 7]3 is a flowchart showing the operation of the controller 40 shown in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0009] The driving control device 1 will be described with reference to FIGS.

[0010] The travel control device 1 is a device (travel control system) that controls the travel motor 26 shown in Figure 2 and controls the travel device 11b (see Figure 1). The travel control device 1 includes a work machine 10 (see Figure 1), a travel operation unit 31, an operation amount detection unit 33, and a controller 40.

[0011] As shown in FIG. 1, the work machine 10 is a machine that performs work, such as a construction machine that performs construction work, and may be, for example, a shovel or a crane. The following mainly describes a case where the work machine 10 is a shovel. The work machine 10 may be operated by an operator (worker) in a cab 13a (described later), or may be remotely operated by an operator outside the work machine 10. The work machine 10 includes a lower traveling body 11, an upper rotating body 13, an attachment 15, a power source 17 shown in FIG. 2, a rotation speed detection unit 19, and a hydraulic circuit 20.

[0012] The lower traveling body 11 (see FIG. 1) is capable of traveling on a traveling surface (such as the ground). As shown in FIG. 1, the lower traveling body 11 includes a lower frame 11a and a traveling device 11b. The lower frame 11a is a structure that supports the traveling device 11b and the upper rotating body 13.

[0013] The traveling unit 11b is a unit that causes the work machine 10 to travel. The traveling unit 11b is equipped with a left traveling unit 11bL and a right traveling unit 11bR. The left traveling unit 11bL is attached to one side portion in the left-right direction (for example, the left side portion) of the lower frame 11a. For example, the left traveling unit 11bL is a unit that includes a crawler and a crawler frame that supports the crawler (the same applies to the right traveling unit 11bR). The left traveling unit 11bL can travel in both the forward and reverse directions (the same applies to the right traveling unit 11bR). The "forward side" of the left traveling unit 11bL is one side in the longitudinal direction of the left traveling unit 11bL (the same applies to the right traveling unit 11bR). The "reverse side" of the left traveling unit 11bL is the side opposite the forward side of the left traveling unit 11bL (the same applies to the right traveling unit 11bR). The right traveling device 11bR is attached to the side of the lower frame 11a opposite to the side to which the left traveling device 11bL is attached in the left-right direction.

[0014] The upper rotating body 13 is mounted on the lower traveling body 11 (more specifically, the lower frame 11a) so as to be able to rotate (rotate around a rotation axis extending in the vertical direction). The upper rotating body 13 is provided with a cab 13a. The cab 13a is a section (operation room) where an operator can operate the work machine 10.

[0015] The attachment 15 is the part that performs work and includes, for example, a boom 15a, an arm 15b, and a tip attachment 15c. The boom 15a is attached to the upper rotating body 13 so that it can be raised and lowered (rotated up and down). The arm 15b is rotatably attached to the boom 15a. The tip attachment 15c is provided at the tip of the attachment 15 and is rotatably attached to the arm 15b. The tip attachment 15c may be, for example, a bucket used to scoop or excavate a work object, a device that clamps the work object (such as a grapple or nibbler), or a device that crushes the work object (such as a breaker).

[0016] The power source 17 drives the pump 21 (see Figure 2). The power source 17 is mounted on the work machine 10 and mounted on the upper rotating body 13. The power source 17 may be an internal combustion engine (engine) or an electric motor. The power source 17 shown in Figure 2 is capable of changing the rotation speed (rotational speed) (more specifically, the rotation speed of the output shaft 17a). The rotation speed of the power source 17 may be changed (arbitrarily) in response to an operation by an operator, or may be controlled by the controller 40. The power source 17 is equipped with an output shaft 17a. The output shaft 17a is a shaft member that rotates when driven by the power source 17.

[0017] The rotation speed detection unit 19 detects the rotation speed (pump rotation speed N) (rotation speed) of the pump 21 (details will be described later).

[0018] The hydraulic circuit 20 is a circuit that controls the travel motor 26. The hydraulic circuit 20 is mounted on the work machine 10 (see FIG. 1) and on the upper rotating body 13 (see FIG. 1). The hydraulic circuit 20 includes a pump 21, a pump displacement control unit 23, the travel motor 26, and a control valve 27.

[0019] The pump 21 is a hydraulic pump that discharges oil when rotated by the power source 17. When rotated by the power source 17, the pump 21 sucks oil from the tank T and discharges the oil. Only one pump 21 may be provided, or multiple pumps 21 may be provided. The pump 21 (more specifically, the input shaft of the pump 21) is connected to the output shaft 17a of the power source 17. The pump 21 may be directly connected to the output shaft 17a. The pump rotation speed N may be equal to the rotation speed of the power source 17 (e.g., the engine rotation speed). The pump 21 may be connected to the output shaft 17a via a transmission (a reducer or a speed-up gear). When the gear ratio (a reduction ratio or a speed-up ratio) of the transmission is constant, the pump rotation speed N may be proportional to the rotation speed of the power source 17.

[0020] The capacity of the pump 21 is changeable. The capacity of the pump 21 is referred to as "pump capacity q" (see Figures 3 and 4; the same applies to pump capacity q below). The pump capacity q is equal to the flow rate of oil discharged from the pump 21 when the input shaft of the pump 21 makes one rotation. Specifically, for example, the pump capacity q (tilting capacity) is changed by changing the tilt angle of a swash plate (not shown) relative to the input shaft of the pump 21. Here, a case where multiple pumps 21 are provided will be described. The pump 21 includes a first pump 21L and a second pump 21R. The first pump 21L supplies oil to the left travel motor 26L. The second pump 21R supplies oil to the right travel motor 26R. The pump 21 may also supply oil to a hydraulic actuator (not shown) other than the travel motor 26.

[0021] The pump displacement control unit 23 (regulator) controls the pump displacement q. The pump displacement control unit 23 controls the pump displacement q in accordance with a command (pump displacement command) input to the pump displacement control unit 23. The pump displacement command is, for example, an electrical signal output by the controller 40, and specifically, for example, a current value (pump displacement command current (tilt angle command current)). The pump displacement control unit 23 may be configured to change the pump displacement q based on the pump displacement command in the form of an electrical signal (without converting the electrical signal). The pump displacement control unit 23 may be configured to convert the pump displacement command from an electrical signal to a pilot pressure (hydraulic pressure) and change the pump displacement q based on the pilot pressure. In this case, the pump displacement control unit 23 may include an electromagnetic proportional valve, or may include a valve other than an electromagnetic proportional valve.

[0022] When a plurality of pumps 21 (specifically, a first pump 21L and a second pump 21R) are provided, the pump capacity control unit 23 is provided for each pump 21. For example, the pump capacity control unit 23 includes a first pump capacity control unit 23L and a second pump capacity control unit 23R. The first pump capacity control unit 23L controls the pump capacity q of the first pump 21L. The second pump capacity control unit 23R controls the pump capacity q of the second pump 21R.

[0023] The travel motor 26 drives the travel device 11b (see Figure 1). The travel motor 26 travels the lower travel unit 11 (see Figure 1) and causes the work machine 10 (see Figure 1) to travel. The travel motor 26 is connected to the pump 21 via a flow path (oil passage) through which oil passes. The travel motor 26 is a hydraulic motor that is operated (rotationally driven) by being supplied with oil (hydraulic oil) discharged from the pump 21. Note that the travel motor 26 may also be an electric motor. The following mainly describes the case where the travel motor 26 is a hydraulic motor. The travel motor 26 includes a left travel motor 26L and a right travel motor 26R.

[0024] The left traveling motor 26L is mounted on the left traveling device 11bL (see FIG. 1) and drives the left traveling device 11bL. The left traveling motor 26L is driven by oil supplied from the first pump 21L.

[0025] The right traveling motor 26R is mounted on the right traveling device 11bR (see FIG. 1) and drives the right traveling device 11bR. The right traveling motor 26R is driven by oil supplied from the second pump 21R.

[0026] The control valve 27 is a valve that controls the operation of the travel motor 26. The control valve 27 is provided between the pump 21 and the travel motor 26 (in the oil path). The control valve 27 is a directional control valve that switches the oil flow direction (oil path), switches the travel motor 26 to be operated, and switches the operation direction (rotation direction) of the travel motor 26. The control valve 27 may change the flow rate of oil supplied to the travel motor 26 to change the rotation speed of the travel motor 26. The control valve 27 includes a left travel control valve 27L and a right travel control valve 27R. The left travel control valve 27L controls the left travel motor 26L. The right travel control valve 27R controls the right travel motor 26R.

[0027] The travel operation unit 31 is operated by an operator. The travel operation unit 31 is a part for operating the travel device 11b (see FIG. 1) and for operating the travel motor 26. The travel operation unit 31 may be provided in the driver's cab 13a (see FIG. 1) or in a device (remote control unit) that performs remote control. The travel operation unit 31 may be a lever (control lever) or a pedal (control pedal). The travel operation unit 31 outputs a command (operation command) for operating the travel motor 26. The travel operation unit 31 outputs the operation command to the control valve 27 and controls (operates) the control valve 27 to operate the travel motor 26. The operation command output by the travel operation unit 31 may be a pilot pressure. In this case, the travel operation unit 31 may be a hydraulic lever equipped with a hydraulic remote control valve. The operation command output by the travel operation unit 31 may be an electric signal. In this case, the travel operation unit 31 may be an electric joystick. The driving operation unit 31 includes a left driving operation unit 31L and a right driving operation unit 31R.

[0028] The left traveling operation unit 31L is a part for operating the left traveling device 11bL (see FIG. 1). More specifically, the left traveling operation unit 31L is a part for operating the left traveling device 11bL (see FIG. 1) by operating the left traveling control valve 27L and operating the left traveling motor 26L. Specifically, for example, when the left traveling operation unit 31L is operated forward from the operator's perspective, the left traveling device 11bL travels forward. When the left traveling operation unit 31L is operated backward from the operator's perspective, the left traveling device 11bL travels backward. Note that traveling forward of the left traveling device 11bL does not necessarily mean traveling forward from the operator's perspective, and traveling backward of the left traveling device 11bL does not necessarily mean traveling backward from the operator's perspective (details will be described later).

[0029] The right traveling operation unit 31R is a part for operating the right traveling device 11bR (see FIG. 1). More specifically, the right traveling operation unit 31R is a part for operating the right traveling device 11bR (see FIG. 1) by operating the right traveling control valve 27R and the right traveling motor 26R. Specific examples of the operation of the right traveling operation unit 31R are the same as those of the left traveling operation unit 31L.

[0030] The operation amount detection unit 33 detects the operation amount of the travel operation unit 31. Hereinafter, the operation amount of the travel operation unit 31 will also be simply referred to as the "operation amount." The operation amount detection unit 33 may detect the operation angle of the travel operation unit 31 (e.g., the angle of a lever or pedal). For example, if the travel operation unit 31 outputs a pilot pressure (secondary pressure of a hydraulic remote control valve) corresponding to the operation amount, the operation amount detection unit 33 may detect this pilot pressure. For example, if the travel operation unit 31 outputs an electrical signal corresponding to the operation amount, the operation amount detection unit 33 may detect this electrical signal. In this case, the operation amount detection unit 33 may be the controller 40. The operation amount detection unit 33 detects the forward and reverse operation amounts of the left and right travel operation units 31. Specifically, for example, the operation amount detection unit 33 includes a left travel operation amount detection unit 33L that detects the operation amount of the left travel operation unit 31L and a right travel operation amount detection unit 33R that detects the operation amount of the right travel operation unit 31R. The left traveling operation amount detection unit 33L includes a left forward movement operation amount detection unit 33Lf and a left backward movement operation amount detection unit 33Lr. The left forward movement operation amount detection unit 33Lf detects the amount of operation for causing the left traveling device 11bL to travel forward. The left backward movement operation amount detection unit 33Lr detects the amount of operation for causing the left traveling device 11bL to travel backward. The left forward movement operation amount detection unit 33Lf and the left backward movement operation amount detection unit 33Lr may be separate devices (sensors) or a single device. Similarly, the right traveling operation amount detection unit 33R includes a right forward movement operation amount detection unit 33Rf and a right backward movement operation amount detection unit 33Rr.

[0031] The controller 40 is a computer that inputs and outputs signals, performs calculations (processing), stores information, and so on. For example, the functions of the controller 40 are realized when a program stored in a memory unit (not shown) of the controller 40 is executed by a calculation unit (not shown). The controller 40 performs various controls. For example, the controller 40 controls the travel motor 26 in accordance with the operation content of the travel operation unit 31 (details will be described later). For example, if the travel motor 26 is a hydraulic motor, the controller 40 controls the capacity of the pump 21. The controller 40 may be mounted in whole or in part on the work machine 10 (see FIG. 1 ), or may be located outside the work machine 10. The controller 40 includes an operation content acquisition unit 41, a pump rotation speed acquisition unit 43, a pump capacity calculation unit 45, and a pump capacity command unit 47.

[0032] The operation content acquisition unit 41 acquires the operation content of the driving operation unit 31. For example, the "operation content" acquired by the operation content acquisition unit 41 includes information on whether or not the driving operation unit 31 has been operated, and includes information on whether or not the left driving operation unit 31L has been operated, and information on whether or not the right driving operation unit 31R has been operated. This "operation content" includes information on the direction of operation (forward or reverse) of the operated driving operation unit 31 and the amount of operation. For example, the operation content acquisition unit 41 acquires a detection result (e.g., an electrical signal) from the operation amount detection unit 33.

[0033] The pump rotation speed acquisition unit 43 acquires the pump rotation speed N. The pump rotation speed acquisition unit 43 may acquire the pump rotation speed N by acquiring the rotation speed of the power source 17. In this case, for example, the pump rotation speed acquisition unit 43 may acquire a detected value of the rotation speed of the power source 17 from the rotation speed detection unit 19, or may acquire a rotation speed command to the power source 17 from the controller 40. When the rotation speed of the power source 17 and the pump rotation speed N are different from each other, the pump rotation speed acquisition unit 43 may calculate the pump rotation speed N based on the rotation speed of the power source 17. Note that the pump rotation speed acquisition unit 43 may also acquire a detected value of the pump rotation speed N of the input shaft of the pump 21. Normally, the pump rotation speed N of the first pump 21L and the pump rotation speed N of the second pump 21R are the same. When the pump rotation speed N differs between the first pump 21L and the second pump 21R, the pump rotation speed acquisition unit 43 may acquire the pump rotation speed N of each of the first pump 21L and the second pump 21R.

[0034] The pump capacity calculation unit 45 calculates the pump capacity q to be instructed by the controller 40 to the pump capacity control unit 23. For example, the pump capacity calculation unit 45 calculates the pump capacity q of each of the first pump 21L and the second pump 21R. The pump capacity calculation unit 45 calculates (calculates, determines) the pump capacity q based on the operation content of the travel operation unit 31 acquired by the operation content acquisition unit 41 (details will be described later).

[0035] The pump displacement command unit 47 commands the pump displacement q. More specifically, the pump displacement command unit 47 outputs a command (pump displacement command) for the pump displacement q calculated by the pump displacement calculation unit 45 to the pump displacement control unit 23. For example, the pump displacement command unit 47 outputs a command for the pump displacement q to each of the first pump displacement control unit 23L and the second pump displacement control unit 23R. The pump displacement command output by the pump displacement command unit 47 is, for example, an electric signal (e.g., a current value).

[0036] (Driving operation) As described above, the driving operation unit 31 is operated by an operator. The operation of the driving device 11b (see FIG. 1) performed by the driving operation unit 31 is called a driving operation. The driving operation includes a straight driving operation and a steering operation.

[0037] The straight-ahead traveling operation is an operation that moves the lower traveling body 11 (see FIG. 1) in a straight line (forward or backward). The straight-ahead traveling operation is an operation in which the left traveling operation unit 31L and the right traveling operation unit 31R are operated in the same operating direction (both forward or both backward) and the left / right operation amount difference D is less than a predetermined difference value Dth0 (for example, approximately zero) (see FIG. 5). The left / right operation amount difference D (see FIG. 5; the same applies to the left / right operation amount difference D below) is the difference between the operation amount of the left traveling operation unit 31L and the operation amount of the right traveling operation unit 31R. The left / right operation amount difference D is the magnitude (absolute value) of the difference between the operation amount of the left traveling operation unit 31L and the operation amount of the right traveling operation unit 31R.

[0038] A steering operation is an operation for changing the orientation (direction) of the lower traveling body 11 (see FIG. 1) relative to the traveling surface (ground, etc.). A steering operation is an operation in which at least one of the left traveling operation unit 31L and the right traveling operation unit 31R is operated, and is an operation other than the above-mentioned "straight traveling operation." Steering operations include traveling steering operations and turning operations.

[0039] The travel steering operation is an operation for changing the direction of the lower travel structure 11 (see FIG. 1) while moving the lower travel structure 11 forward or backward. The travel steering operation is an operation in which the left travel operation unit 31L and the right travel operation unit 31R are operated in the same operation direction, and the left and right operation amount difference D is equal to or greater than a predetermined difference value Dth0 (see FIG. 5).

[0040] A turn operation is an operation to rotate the lower traveling body 11 (see FIG. 1) on the spot. Turn operations include a pivot turn operation and a spin turn operation. A pivot turn operation is an operation to pivot the lower traveling body 11. A pivot turn operation is an operation in which only one of the left traveling operation unit 31L and the right traveling operation unit 31R is operated. A spin turn operation is an operation to spin the lower traveling body 11. A spin turn operation is an operation in which the left traveling operation unit 31L and the right traveling operation unit 31R are operated in opposite operating directions. In a spin turn operation, the left traveling operation unit 31L and the right traveling operation unit 31R may be operated in opposite operating directions and the same amount of operation. Furthermore, in a spin turn operation, the left traveling operation unit 31L and the right traveling operation unit 31R may be operated in opposite operating directions and the amount of operation may be different.

[0041] (Activation) The driving control device 1 is configured to operate as follows: The operation of the pump displacement calculation unit 45 of the controller 40 will be mainly described below.

[0042] The operation of the controller 40 is summarized as follows. The controller 40 determines the difference between the operation content of the left travel operation unit 31L and the operation content of the right travel operation unit 31R (see steps S20 and S30 in FIG. 7). The controller 40 changes the limit on the acceleration of the travel motor 26 according to the determined difference (see steps S22, S32, and S42 in FIG. 7). Specifically, for example, the controller 40 changes the limit on the acceleration of the travel motor 26 by changing the limit on the pump displacement change amount Δq (described below).

[0043] (Calculation of target pump capacity qr according to operation details) The controller 40 controls the travel motor 26 in accordance with the operation content (such as the amount of operation) of the travel operation unit 31. Specifically, the controller 40 calculates a target value for the pump capacity q in accordance with the operation content of the travel operation unit 31. The target value for the pump capacity q is referred to as a "target pump capacity qr" (see FIGS. 3 and 4; the same applies to the target pump capacity qr below). The controller 40 calculates the target pump capacity qr for each of the first pump 21L and the second pump 21R. Specifically, for example, the controller 40 has a relationship (map) previously set between the operation content of the travel operation unit 31 and information related to the target pump capacity qr. The "information related to the target pump capacity qr" may be the target pump capacity qr or information related to the target pump capacity qr. The "information related to the target pump capacity qr" may be a target value for a pump capacity command (a command output from the controller 40 to the pump capacity control unit 23), and specifically, for example, may be a target current value. Furthermore, for example, the controller 40 may calculate the target pump displacement qr based on a mathematical formula or the like in accordance with the operation details of the travel operation unit 31. Note that there are cases where the pump 21 supplies oil not only to the travel motor 26 but also to hydraulic actuators other than the travel motor 26. In this case, the controller 40 may determine the target pump displacement qr based on the operation details of the travel motor 26 and the operation details of the hydraulic actuators other than the travel motor 26.

[0044] (Limitation of pump displacement change Δq) For example, the controller 40 limits the acceleration of the travel motor 26 by limiting the pump displacement change amount Δq. The pump displacement change amount Δq is the amount of change in the pump displacement q per unit time (the increase gain of the pump displacement q) (see the slope of the graphs of the pump displacement q shown in FIGS. 3 and 4). The above-mentioned "unit time" can be set in various ways, and may be, for example, one control cycle of the controller 40, one second, or one minute.

[0045] More specifically, when limiting the pump displacement change amount Δq, the controller 40 determines the target pump displacement amount qr and then gradually brings the actual pump displacement amount q closer to the target pump displacement amount qr (see FIG. 3). By limiting the pump displacement change amount Δq, the controller 40 limits the amount of change in the pump discharge flow rate Q per unit time (pump discharge flow rate change amount ΔQ), limits the acceleration of the traveling motor 26, and suppresses sudden changes in the rotation speed of the traveling motor 26.

[0046] Specifically, the controller 40 limits the pump displacement change amount Δq by setting an upper limit value R (an example of an upper limit value related to the magnitude of acceleration of the travel motor 26) of the magnitude (absolute value) of the pump displacement change amount Δq. More specifically, assuming that the pump displacement change amount Δq is not limited, suppose that an operation (sudden operation) is performed on the travel operation unit 31 such that the pump displacement change amount Δq exceeds the upper limit value R. If the pump displacement change amount Δq is limited when this sudden operation is performed, the controller 40 limits the pump displacement change amount Δq so that the pump displacement change amount Δq is equal to or less than the upper limit value R. More specifically, if the pump displacement q is controlled by the current value, the controller 40 limits the pump displacement change amount Δq by setting an upper limit value R of the magnitude (absolute value) of the change in the current value per unit time.

[0047] FIG. 3 shows a graph representing changes over time in the pump capacity q and other parameters when the pump capacity change amount Δq is limited. The vertical axis of this graph represents the operation amount of the travel operation unit 31, the pump capacity q, and the pump capacity command (e.g., current). The horizontal axis of the graph represents time. The graph shown at the top of FIG. 3 is a graph relating to the left travel operation unit 31L and the first pump 21L. The graph shown at the bottom of FIG. 3 is a graph relating to the right travel operation unit 31R and the second pump 21R. The graph shown in FIG. 3 is a graph representing a case where a straight-ahead operation is performed with the travel operation unit 31. In this graph, the operation amount is the same for the left travel operation unit 31L and the right travel operation unit 31R. Limiting the pump capacity change amount Δq means that the slope of the graph showing the relationship between pump capacity q and time is limited.

[0048] In the example shown in FIG. 3, the operation amount of the left travel operation unit 31L increases from time t0 to time t1 and remains constant after time t1. Meanwhile, the pump displacement command (e.g., current) of the first pump 21L increases from time t0 to time t2 (after time t1) and becomes a command corresponding to the operation amount of the left travel operation unit 31L (a command corresponding to the target pump displacement qr) at time t2. As a result, the pump displacement q of the first pump 21L increases from time t0 to time t2 and becomes a capacity corresponding to the operation amount of the left travel operation unit 31L (the target pump displacement qr) at time t2. Here, assuming that the pump displacement change amount Δq is not limited, the magnitude of the pump displacement change amount Δq of the first pump 21L from time t0 to time t1 is greater than the upper limit value R set in the controller 40. Meanwhile, in this example, the pump displacement change amount Δq is limited. Therefore, the controller 40 limits the pump displacement command of the first pump 21L so that the magnitude of the pump displacement change amount Δq is equal to or less than the upper limit value R (for example, equal to the upper limit value R). When limiting the pump displacement change amount Δq, the controller 40 reduces the pump displacement change amount Δq and the pump displacement command compared to when not limiting the pump displacement change amount Δq. Therefore, the pump displacement command of the first pump 21L does not complete its increase to the capacity (target pump displacement qr) corresponding to the operation amount of the left traveling operation unit 31L at time t1, when the increase in the operation amount of the left traveling operation unit 31L ends. The pump displacement command of the first pump 21L continues to increase after time t1 and becomes a command corresponding to the operation amount of the left traveling operation unit 31L (a command corresponding to the target pump displacement qr) at time t2. Note that after time t2, the pump displacement command of the first pump 21L becomes constant at a command value corresponding to the target pump displacement qr. Furthermore, the pump displacement q of the first pump 21L becomes constant at the target pump displacement qr. In the example shown in FIG. 3, the operation amount of the right traveling operation unit 31R, the pump displacement command of the second pump 21R, and the pump displacement q of the second pump 21R change in the same way as the left traveling operation unit 31L and the first pump 21L.

[0049] There may be cases where the controller 40 does not limit the acceleration of the travel motor 26 (specifically, does not limit the pump displacement change amount Δq). In this case, the controller 40 determines the target pump displacement qr and immediately sets the actual pump displacement q to the target pump displacement qr (see FIG. 4).

[0050] FIG. 4 shows a graph representing changes over time in pump capacity q and other parameters when the pump capacity change amount Δq is not limited. The vertical and horizontal axes of this graph are the same as those in FIG. 3. The graph shown at the top of FIG. 4 is a graph relating to the left driving operation unit 31L and the first pump 21L. The graph shown at the bottom of FIG. 4 is a graph relating to the right driving operation unit 31R and the second pump 21R. The graph shown in FIG. 4 is a graph representing a case where driving steering is performed with the driving operation unit 31. In this graph, the amount of operation of the right driving operation unit 31R is smaller than the amount of operation of the left driving operation unit 31L.

[0051] In the example shown in FIG. 4, the operation amount of the left travel operation unit 31L increases from time t0 to time t1 and remains constant after time t1 (similar to the example shown in FIG. 3). Meanwhile, the pump displacement command (e.g., current) of the first pump 21L increases from time t0 to time t1 and becomes a command corresponding to the operation amount of the left travel operation unit 31L (a command corresponding to the target pump displacement qr) at time t1 (before time t2 (see FIG. 3)). As a result, the pump displacement q of the first pump 21L increases from time t0 to time t1 and becomes a capacity corresponding to the operation amount of the left travel operation unit 31L (the target pump displacement qr) at time t1. Note that after time t1, the pump displacement command of the first pump 21L becomes constant at a command value corresponding to the target pump displacement qr, and the pump displacement q of the first pump 21L becomes constant at the target pump displacement qr. In the example shown in Figure 4, the operation amount of the right travel operation unit 31R, the pump capacity command of the second pump 21R, and the pump capacity q of the second pump 21R change in approximately the same manner as the left travel operation unit 31L and the first pump 21L. The operation amount of the right travel operation unit 31R is smaller than the operation amount of the left travel operation unit 31L. Therefore, the pump capacity command of the second pump 21R is smaller than the pump capacity command of the first pump 21L. As a result, the pump capacity q of the second pump 21R is smaller than the pump capacity q of the first pump 21L.

[0052] The controller 40 may limit the acceleration of the travel motor 26 only when the travel motor 26 accelerates, or may limit the acceleration when the travel motor 26 accelerates and decelerates, or may limit the acceleration only when the travel motor 26 decelerates. Specifically, the controller 40 may limit the pump displacement change amount Δq only when the pump displacement q increases, or may limit the pump displacement change amount Δq when the pump displacement q increases and decreases, or may limit the pump displacement change amount Δq only when the pump displacement q decreases.

[0053] (Change in limit for pump displacement change Δq) The controller 40 shown in FIG. 2 changes the limit on the acceleration of the travel motor 26 depending on the difference between the operation of the left travel operation unit 31L and the operation of the right travel operation unit 31R. Specifically, the controller 40 changes the limit on the pump displacement change amount Δq depending on the difference between the operation of the left travel operation unit 31L and the operation of the right travel operation unit 31R. The "difference between the operation of the left travel operation unit 31L and the operation of the right travel operation unit 31R" may include a difference in the operation direction (forward or reverse) or a difference in the amount of operation. Note that the "difference between the operation of the left travel operation unit 31L and the operation of the right travel operation unit 31R" does not include a difference in the travel device 11b (see FIG. 1) that is the target of operation (i.e., a difference between the left travel device 11bL (see FIG. 1) and the right travel device 11bR (see FIG. 1)). The "changing the limit on the acceleration of the travel motor 26" may include changing whether or not to limit the acceleration of the travel motor 26, or may include changing the degree of limit on the acceleration of the travel motor 26. Specifically, the above "changing the limit on the pump capacity change amount Δq" may include changing whether or not there is a limit on the pump capacity change amount Δq, or may include changing the degree of limit on the pump capacity change amount Δq (specifically, the value of the upper limit value R).

[0054] (Change of restrictions on straight-line driving and steering operations) It is preferable that the controller 40 set a smaller limit on the acceleration of the travel motor 26 when a steering operation is performed than on the acceleration of the travel motor 26 when a straight travel operation is performed. Specifically, it is preferable that the controller 40 set a smaller limit on the pump displacement change amount Δq when a steering operation is performed than on the limit on the pump displacement change amount Δq when a straight travel operation is performed. This "set a smaller limit" means reducing (loosening) the degree of the limit and includes eliminating the limit. As described above, the controller 40 may set an upper limit R for the magnitude (absolute value) of the pump displacement change amount Δq. In this case, it is preferable that the controller 40 set a higher upper limit R when a steering operation is performed than the upper limit R when a straight travel operation is performed. Note that a comparison is made here between a straight travel operation and a steering operation for travel. In this comparison, it is assumed that conditions other than the travel operation (e.g., pump rotation speed N, operation amount of hydraulic actuators other than the travel motor 26, etc.) are the same between a straight travel operation and a steering operation for travel. Similarly, in the following comparisons, it is assumed that conditions other than the content of the comparison are the same.

[0055] The reason why it is preferable to change the limit on the acceleration of the travel motor 26 depending on whether the vehicle is traveling straight ahead or steering is as follows, for example.

[0056] (Limitation of pump capacity change Δq when driving straight) When operating to travel straight ahead, it is preferable that the response of the travel device 11b (see FIG. 1) to the operation of the travel operation unit 31 be gentle. For example, it is preferable that the work machine 10 (see FIG. 1) starts off slowly. The reason for this is as follows, for example.

[0057] [Example Problem A1: Problem of Misoperation] When operating the vehicle for traveling straight, a problem of misoperation may occur. Depending on the rotation angle of the upper rotating body 13 relative to the lower running body 11 shown in FIG. 1 , the lower running body 11 may travel in a direction contrary to the operator's intention. Specifically, for example, the front side of the upper rotating body 13 and the front side of the lower running body 11 may face the same or approximately the same direction. In this case, the operator operates the travel operation unit 31 forward as seen from the operator to cause the lower running body 11 to travel forward. As a result, the lower running body 11 travels to the front side of the upper rotating body 13 (including diagonally forward). On the other hand, the front side of the upper rotating body 13 and the front side of the lower running body 11 may face the opposite direction or approximately the opposite direction. In this case, the operator operates the travel operation unit 31 forward as seen from the operator, with the intention of causing the lower running body 11 to travel to the front side of the upper rotating body 13. As a result, the lower traveling body 11 travels to the rear (including diagonally rearward) of the upper rotating body 13. This causes the operator to perform an erroneous operation (causing a problem of erroneous operation). Similarly, if the front side of the upper rotating body 13 faces right or left relative to the front side of the lower traveling body 11, a problem of erroneous operation may also occur.

[0058] [Example Problem A2: Shock Problem] When operating the travel operation unit 31 in a straight line, a shock may occur in the work machine 10. More specifically, if the operator suddenly operates the travel operation unit 31, the rotation speed of the travel motor 26 (see FIG. 2) changes suddenly, causing a sudden change in the speed of the travel device 11b (sudden acceleration or deceleration). This causes a shock (vibration, impact) in the work machine 10. For example, if the work machine 10 suddenly accelerates from a stopped state, a starting shock occurs. If the operator is operating the work machine 10 from inside the cab 13a, the shock from the work machine 10 may be transmitted to the operator's arm. This may result in the operator unintentionally operating the travel operation unit 31 (e.g., lever hunting).

[0059] In order to mitigate the above problem examples A1 and A2, it is preferable that the controller 40 limit the acceleration of the travel motor 26 during straight-ahead travel operation, thereby smoothing the response of the travel device 11b to operation of the travel operation unit 31. Specifically, the controller 40 limits the amount of change in pump displacement Δq. Therefore, even if the operator erroneously operates the travel operation unit 31, the travel distance of the lower traveling body 11 (of the work machine 10) can be reduced. Furthermore, it is possible to reduce shock to the work machine 10 caused by a sudden change in speed of the travel device 11b, thereby suppressing lever hunting, for example.

[0060] (Limitation of pump displacement change Δq during steering operation) When steering, the travel device 11b is required to have good response to the operation of the travel operation unit 31.

[0061] If the acceleration of the travel motor 26 is limited during steering operations in the same way as during straight-ahead travel operations, the problem of poor steering operability arises. Specifically, for example, if the pump displacement change amount Δq is limited, the change in the discharge flow rate of the pump 21 (see FIG. 2) becomes gentler in response to changes in the operation amount of the travel operation unit 31 (the pump discharge flow rate change amount ΔQ is limited). This causes gentle changes in the flow rate of oil supplied from the pump 21 to the travel motor 26, and the speed change of the travel motor 26 becomes gentler (i.e., the acceleration is limited). This results in poor responsiveness of the speed change (operability) of the travel device 11b in response to steering operations at the travel operation unit 31. As a result, the responsiveness of the undercarriage 11 in changing direction in response to steering operations at the travel operation unit 31 becomes poor. In particular, when the work machine 10 travels on narrow terrain, it is important for the undercarriage 11 to change direction responsively. If the lower traveling body 11 cannot change direction responsively, the traveling device 11b may deviate from the area in which it should travel (the road, the step board, etc.). In this case, for example, there is a risk that the work machine 10 may slip off the step board.

[0062] Therefore, it is preferable that the controller 40 limits the acceleration of the travel motor 26 less during steering operation than during straight ahead driving operation, thereby improving the operability of the steering operation.

[0063] (Limitation of pump displacement change Δq during steering operation) The following describes a case where a travel steering operation is performed by the travel operation unit 31. Here, the description mainly focuses on a case where the controller 40 sets an upper limit value R for the magnitude of the pump displacement change amount Δq, thereby limiting the acceleration of the travel motor 26. For example, the controller 40 sets the upper limit value R according to the following [Condition B1] and [Condition B2].

[0064] [Condition B1] It is preferable that the controller 40 reduce the limit on the acceleration of the travel motor 26 when the left / right operation amount difference D is a second difference D2 that is larger than the first difference D1, compared to when the left / right operation amount difference D is the first difference D1 (see FIG. 5). Specifically, the controller 40 sets the upper limit value R when the left / right operation amount difference D is the first difference D1 to a first upper limit value R1 (see FIG. 5). At this time, it is preferable that the controller 40 set the upper limit value R when the left / right operation amount difference D is the second difference D2 to a second upper limit value R2 that is larger than the first upper limit value R1 (see FIG. 5). In this case, when the left / right operation amount difference D is small during travel steering operation (operation similar to straight travel operation), the above-mentioned problem of erroneous operation and the problem of shock occurring in the work machine 10 can be suppressed. Furthermore, when the left / right operation amount difference D is large during travel steering operation, the responsiveness of the travel device 11b to operation of the travel operation unit 31 can be improved.

[0065] [Condition B2] When a steering operation for traveling is performed, it is preferable that the controller 40 decreases the limit on the acceleration of the traveling motor 26 (specifically, sets the upper limit value R to a larger value) as the left / right operation amount difference D increases (see Figure 5).

[0066] [Condition B2a] For example, when a steering operation for traveling is performed, the controller 40 may increase the upper limit value R in a stepwise manner as the left-right operation amount difference D increases (not shown). [Condition B2b] For example, the controller 40 may increase the upper limit value R continuously as the left-right operation amount difference D increases. A graph showing the relationship between the left-right operation amount difference D and the upper limit value R, which satisfies [Condition B2b], may be a curve, a broken line, a straight line, or a combination of these. [Condition B2b1] For example, the controller 40 may set the upper limit value R so that the upper limit value R is proportional to the left-right operation amount difference D (see FIG. 5).

[0067] The graph shown in FIG. 5 is a graph (map M5) showing an example of the relationship between the left / right operation amount difference D and the upper limit value R. When the left / right operation amount difference D is less than a predetermined difference value Dth0, a straight-ahead operation is being performed using the travel operation unit 31 (see FIG. 1). At this time, the upper limit value R is set to a minimum value (minimum upper limit value Rmin), the pump displacement change amount Δq is most strictly limited, and the acceleration of the travel motor 26 is most strictly limited. When the left / right operation amount difference D is equal to or greater than the predetermined difference value Dth0 and equal to or less than the maximum difference value Dmax, a travel steering operation is being performed using the travel operation unit 31. At this time, as the left / right operation amount difference D increases, the upper limit value R is set to a larger value, the pump displacement change amount Δq is less (more lenient), and the acceleration of the travel motor 26 is less strictly limited. In this example, when the left / right operation amount difference D is equal to or greater than the predetermined difference value Dth0 and equal to or less than the maximum difference value Dmax, the upper limit value R is proportional to the left / right operation amount difference D. When the left / right operation amount difference D is greater than the maximum difference value Dmax, for example, a travel steering operation may be performed with the travel operation unit 31, or a pivot turn operation may be performed. When the left / right operation amount difference D is greater than the maximum difference value Dmax, the upper limit value R is set to the maximum value (maximum upper limit value Rmax), the limit on the pump displacement change amount Δq is set to the smallest, and the limit on the acceleration of the travel motor 26 is set to the smallest. The above "setting the limit on the pump displacement change amount Δq to the smallest" may mean that the pump displacement change amount Δq is limited to a certain amount, or may mean that there is no limit on the pump displacement change amount Δq.

[0068] (Another example that meets the above [Condition B1]) In the example shown in FIG. 5, the upper limit value R increases as the left-right operation amount difference D increases. On the other hand, the value of the upper limit value R may change in stages with a certain magnitude of the left-right operation amount difference D as a boundary (not shown). [Condition B1a] Specifically, for example, a threshold value Dth1 related to the left-right operation amount difference D may be set in advance (before the upper limit value R is set) in the controller 40. When the left-right operation amount difference D is less than the threshold value Dth1 (for example, the first difference D1), the controller 40 may set the upper limit value R to a first upper limit value R1, and when the left-right operation amount difference D is equal to or greater than the threshold value Dth1 (for example, the second difference D2), the controller 40 may set the upper limit value R to a second upper limit value R2. Furthermore, a plurality of threshold values ​​Dth1 (multiple stages) may be set.

[0069] (Correction of limit on pump displacement change amount Δq according to pump rotation speed N) 2 may correct the determined limit on the pump displacement change amount Δq. For example, it is preferable that the controller 40 corrects the limit on the pump displacement change amount Δq in accordance with the pump rotation speed N.

[0070] (When pump rotation speed N is not taken into consideration) An example of why it is preferable to correct the limit on the pump displacement change amount Δq (e.g., upper limit value R) in accordance with the pump rotation speed N is as follows. As described above, the limit on the pump displacement change amount Δq is changed based on the difference between the operation content of the left travel operation unit 31L and the operation content of the right travel operation unit 31R, thereby changing the limit on the acceleration of the travel motor 26. Here, the acceleration of the travel motor 26 changes depending on the amount of change in the flow rate of oil supplied to the travel motor 26. The amount of change in the flow rate of oil supplied to the travel motor 26 changes depending on the amount of change in pump discharge flow rate ΔQ. The amount of change in pump discharge flow rate ΔQ is proportional to the product of the pump displacement change amount Δq and the pump rotation speed N. Therefore, the magnitude of the acceleration of the travel motor 26 changes depending on the size of the pump rotation speed N.

[0071] The acceleration of the travel motor 26 changes depending on the pump rotation speed N. For example, when the minimum pump capacity q of the pump 21 is 10 cm 3 / rev, the pump displacement change amount Δq per 0.1 seconds is set to 10cc, and the pump displacement q is increased from the minimum value. -1 In this case, the pump discharge flow rate Q is 10 L / min (minimum flow rate) when the pump capacity q starts to increase, and changes to 60 L / min 0.5 seconds after the pump capacity q starts to increase. On the other hand, when the pump rotation speed N is 2000 min -1 In this case, the pump discharge flow rate Q is 20 L / min (minimum flow rate) when the pump capacity q starts to increase, and changes to 120 L / min 0.5 seconds after the pump capacity q starts to increase. In this way, even if the pump capacity change amount Δq remains the same (10 cc per 0.1 seconds in this example), as the pump rotation speed N increases, the pump discharge flow rate change amount ΔQ also increases. Note that the pump capacity q 0.5 seconds after the pump capacity q starts to increase will be the maximum value of the pump capacity q (for example, 200 cm 3 / rev).

[0072] The following problem may occur due to the acceleration of the travel motor 26 changing depending on the magnitude of the pump rotation speed N.

[0073] [Example Problem C1: Problem caused by sudden change in pump discharge flow rate Q] Even if the amount of change in pump capacity Δq is the same, the greater the pump rotation speed N, the greater the amount of change in pump discharge flow rate ΔQ, making it more likely that the pump discharge flow rate Q will change suddenly. When the pump discharge flow rate Q changes suddenly, the flow rate of oil supplied to the travel motor 26 (input flow rate) changes suddenly, causing a sudden change in the speed of the travel motor 26 and a sudden change in the speed of the travel device 11b (see Figure 1), which is likely to cause a shock (see example problem A2 above) in the work machine 10 (see Figure 1).

[0074] [Problem Example C2: Slow Change in Pump Discharge Flow Rate Q] Even if the pump displacement change amount Δq is the same, the smaller the pump rotation speed N, the smaller the pump discharge flow rate change amount ΔQ. [Problem Example C2a] As a result, the change in the flow rate of oil supplied to the travel motor 26 (input flow rate) in response to changes in the operation amount of the travel operation unit 31 becomes slower, resulting in poor response to speed changes of the travel motor 26 and poor response to speed changes of the travel device 11b (see FIG. 1). Therefore, the smaller the pump rotation speed N, the worse the operability of the travel operation unit 31 may become. [Problem Example C2b] Furthermore, when the work machine 10 (see FIG. 1) is traveling downhill, the travel motor 26 may be affected by gravity acting on the work machine 10. Specifically, due to the effect of gravity, the travel motor 26 may be rotated at a rotation speed higher than the rotation speed of the travel motor 26 corresponding to the flow rate of oil supplied to the travel motor 26 in response to the operation amount of the travel operation unit 31. In this case, the flow rate of oil supplied to the travel motor 26 may be insufficient compared to the flow rate of oil required to rotate the travel motor 26. This may result in a drop in oil pressure in the travel motor 26 and in the oil passage that supplies oil to the travel motor 26, which may cause cavitation. In this case, the hydraulic equipment in the hydraulic circuit 20 may be damaged, or the travel motor 26 may behave abnormally (for example, its rotation speed may become unstable).

[0075] If the limit on the pump displacement change amount Δq is set too large (strict) in order to suppress the problem caused by a sudden change in the pump discharge flow rate Q (problem example C1 above), a problem (problem example C2 above) may occur in which the pump discharge flow rate Q changes slowly. On the other hand, if the limit on the pump displacement change amount Δq is set too small (loose) in order to suppress the problem caused by a slow change in the pump discharge flow rate Q (problem example C2 above), a problem (problem example C1 above) may occur in which the pump discharge flow rate Q changes suddenly.

[0076] (Details of the limit on the pump displacement change amount Δq according to the pump rotation speed N) In order to alleviate these problems, it is preferable that the controller 40 corrects the magnitude of the limit on the pump displacement change amount Δq in accordance with the pump rotation speed N (see FIG. 6). For example, the controller 40 corrects the upper limit value R in accordance with the pump rotation speed N. The upper limit value R corrected by the controller 40 is set as the corrected upper limit value Ra. For example, the controller 40 sets the corrected upper limit value Ra (corrects the upper limit value R) according to the following [Condition E1], [Condition E2], and [Condition E3]. Note that each of the following conditions applies when the corrected upper limit value R (the upper limit value R determined based on the operation content of the travel operation unit 31) is a certain constant value. If the corrected upper limit value R changes, the following conditions do not need to be met. Furthermore, each of the following conditions applies when the pump rotation speed N is within a predetermined range (an example of the predetermined range will be described later), and does not need to be met when the pump rotation speed N is outside the predetermined range.

[0077] [Condition E1] It is preferable that the controller 40 increase the limit on the pump displacement change amount Δq when the pump rotation speed N is a second rotation speed N2 that is greater than the first rotation speed N1, compared to when the pump rotation speed N is a first rotation speed N1. Specifically, the controller 40 sets the corrected upper limit value Ra to a low rotation speed upper limit value Ra1 (corrects the upper limit value R to the low rotation speed upper limit value Ra1) when the pump rotation speed N is the first rotation speed N1 (see FIG. 6). In this case, it is preferable that the controller 40 sets the corrected upper limit value Ra to a high rotation speed upper limit value Ra2 that is smaller than the low rotation speed upper limit value Ra1 when the pump rotation speed N is the second rotation speed N2 (see FIG. 6). By setting the corrected upper limit value Ra in this manner, the cruise control device 1 can mitigate the problem of a sudden change in the pump discharge flow rate Q (the above-mentioned example problem C1) and the problem of a slow change in the pump discharge flow rate Q (the above-mentioned example problem C2), regardless of the pump rotation speed N.

[0078] [Condition E2] It is preferable that the controller 40 increase the limit on the pump displacement change amount Δq as the pump rotation speed N increases. Specifically, it is preferable that the controller 40 set the corrected upper limit value Ra so that the corrected upper limit value Ra decreases as the pump rotation speed N increases (see FIG. 6).

[0079] [Condition E2a] For example, the controller 40 may decrease the corrected upper limit value Ra in stages as the pump rotation speed N increases (not shown). [Condition E2b] For example, the controller 40 may decrease the corrected upper limit value Ra continuously as the pump rotation speed N increases. A graph showing the relationship between the pump rotation speed N and the corrected upper limit value Ra that satisfies [Condition E2b] may be a curve, a broken line, a straight line, or a combination of these. [Condition E2b1] For example, it is preferable that the controller 40 set the corrected upper limit value Ra so that the corrected upper limit value Ra is proportional to the pump rotation speed N (see, for example, Equation 1 below).

[0080] [Condition E3] It is preferable that the controller 40 sets the corrected upper limit value Ra so that the amount of change in pump discharge flow rate ΔQ is constant for any pump rotation speed N within a predetermined range (regardless of the pump rotation speed N). The "within a predetermined range" of the pump rotation speed N is, for example, the range (e.g., the usage range) of the pump rotation speed N used when operating the work machine 10 (see FIG. 1).

[0081] The graph shown in Figure 6 is a graph (map M6) showing the relationship between the pump rotation speed N and the corrected upper limit value Ra. The corrected upper limit value Ra in this graph is also the magnitude (absolute value) of the pump displacement change amount Δq limited by the corrected upper limit value Ra. This graph is a graph when the above [Condition E1], [Condition E2], [Condition E2b1], and [Condition E3] are satisfied.

[0082] (Another example that satisfies the above [Condition E1]) In the example shown in FIG. 6, the corrected upper limit value Ra decreases as the pump rotation speed N increases. On the other hand, the value of the corrected upper limit value Ra may change in stages with a certain pump rotation speed N as a boundary (not shown). [Condition E1a] Specifically, for example, a threshold value Nth1 related to the pump rotation speed N may be set in advance in the controller 40 (before the corrected upper limit value Ra is set). When the pump rotation speed N is equal to or greater than the threshold value Nth1 (e.g., the second rotation speed N2), the controller 40 may set the corrected upper limit value Ra to the high rotation speed upper limit value Ra2. When the pump rotation speed N is less than the threshold value Nth1 (e.g., the first rotation speed N1), the controller 40 may set the corrected upper limit value Ra to the low rotation speed upper limit value Ra1. Furthermore, a plurality of threshold values ​​Nth1 (multiple stages) may be set.

[0083] (Calculation of corrected upper limit value Ra) Specifically, for example, the controller 40 (see FIG. 2) calculates the corrected upper limit value Ra as follows: The controller 40 determines the corrected upper limit value Ra (reference upper limit value Rs) at a reference pump rotation speed N (reference rotation speed Ns). For example, the reference rotation speed Ns may be the maximum value (maximum rotation speed) of the pump rotation speed N of the pump 21 (see FIG. 2) in the usage range, or may not be the maximum value. The reference rotation speed Ns may be, for example, the pump rotation speed N when the rotation speed of the power source 17 (see FIG. 2) is at "high idle." For example, a relationship (map) between the operation content and the reference upper limit value Rs may be preset in the controller 40. The controller 40 may calculate the reference upper limit value Rs according to some condition (such as a mathematical formula). The controller 40 also calculates the ratio (rotation speed ratio) (e.g., Ns / Nc) between the reference rotation speed Ns and the current pump rotation speed N (usage rotation speed Nc). Then, the controller 40 calculates the corrected upper limit value Ra at the operating rotation speed Nc based on the reference upper limit value Rs and the rotation speed ratio (Ns / Nc). Through this calculation, the controller 40 corrects the reference upper limit value Rs (upper limit value R before correction) at the reference rotation speed Ns to the corrected upper limit value Ra at the current operating rotation speed Nc.

[0084] Specifically, for example, the controller 40 (see FIG. 2) calculates the magnitude α of the corrected upper limit value Ra using the following formula: α = Reference upper limit value Rs × (Reference rotation speed Ns / Operating rotation speed Nc) (Equation 1) In this case, the pump discharge flow rate change amount ΔQ is constant at any pump rotation speed N.

[0085] The controller 40 (see FIG. 2) may calculate the difference (rotation speed difference) between the reference rotation speed Ns and the operating rotation speed Nc (for example, Ns-Nc or ​​Nc-Ns). The controller 40 may then calculate the corrected upper limit value Ra based on the reference upper limit value Rs and the rotation speed difference.

[0086] (flowchart) A specific example of calculation of the pump displacement q by the controller 40 shown in Fig. 2 will be described with reference to the flowchart shown in Fig. 7. Steps S10 to S50 of the flowchart will be described below with reference to Fig. 7.

[0087] In step S10, the controller 40 shown in FIG. 2 determines whether a driving operation is being performed (whether a driving operation is present) with the driving operation unit 31. If an operation amount for operating the driving motor 26 is being performed with at least one of the left driving operation unit 31L and the right driving operation unit 31R, the controller 40 determines that a driving operation is being performed with the driving operation unit 31. In this case (YES in step S10), the controller 40 advances the processing flow to step S20. If an operation amount for operating the driving motor 26 is not being performed with either the left driving operation unit 31L or the right driving operation unit 31R, the controller 40 determines that a driving operation is not being performed with the driving operation unit 31 (no driving operation). In this case (NO in step S10), the controller 40 ends the current series of processing (proceeds to "return") and starts the next series of processing.

[0088] In step S20, the controller 40 determines whether driving operations are being performed on both the left driving operation unit 31L and the right driving operation unit 31R. If driving operations are being performed on both the left driving operation unit 31L and the right driving operation unit 31R (YES in step S20), the flow proceeds to step S30. If driving operations are being performed on only one of the left driving operation unit 31L and the right driving operation unit 31R (NO in step S20), specifically if a pivot turn operation is being performed, the flow proceeds to step S21.

[0089] In step S21, the controller 40 calculates a target pump displacement qr corresponding to the operation amount of the travel operation unit 31. More specifically, the controller 40 calculates a target pump displacement qr of the pump 21 that supplies oil to the travel motor 26 of the travel unit 11b that is being operated, either the left travel unit 11bL or the right travel unit 11bR. Next, the flow proceeds to step S22.

[0090] In step S22, the controller 40 calculates the pump displacement change amount Δq. More specifically, the controller 40 calculates the pump displacement change amount Δq of the pump 21 that supplies oil to the travel motor 26 of the travel device 11b that is being operated, either the left travel device 11bL or the right travel device 11bR. When a turn operation (here, a pivot turn operation) is performed, the pump displacement change amount Δq does not need to be limited. In this case, for example, the controller 40 may calculate the pump displacement change amount Δq so that the actual pump displacement q immediately becomes the target pump displacement qr. Also, for example, the controller 40 may set the pump displacement change amount Δq to the maximum upper limit value Rmax (see FIG. 5). After step S22, the flow may proceed to step S50, or may end this series of processes (or may proceed to "return").

[0091] In step S30, the controller 40 determines whether the operation directions (forward and reverse) of the left traveling operation unit 31L and the right traveling operation unit 31R are the same. If the operation directions of the left traveling operation unit 31L and the right traveling operation unit 31R are the same (YES in step S30), specifically, if a traveling steering operation or a straight traveling operation is being performed, the controller 40 causes the processing flow to proceed to step S41. If the operation directions of the left traveling operation unit 31L and the right traveling operation unit 31R are opposite to each other (NO in step S30), specifically, if a spin turn operation is being performed, the controller 40 causes the processing flow to proceed to step S31.

[0092] In step S31, the controller 40 performs substantially the same processing as in step S21. In step S31, the controller 40 calculates the target pump displacements qr of the first pump 21L and the second pump 21R. Next, the flow proceeds to step S32.

[0093] In step S32, the controller 40 performs substantially the same processing as in step S22. In step S32, the controller 40 calculates the pump displacement change amount Δq of each of the first pump 21L and the second pump 21R. Next, the flow proceeds to step S50 or "RETURN".

[0094] In step S41, the controller 40 performs the same process as in step S31. Next, the flow proceeds to step S42.

[0095] In step S42, the controller 40 calculates the pump displacement change amount Δq limited in accordance with the left / right operation amount difference D. Specifically, for example, the controller 40 calculates an upper limit value R in accordance with the left / right operation amount difference D. As shown in FIG. 5, the controller 40 increases the upper limit value R (decreases the limit on the pump displacement change amount Δq) as the left / right operation amount difference D increases. The controller 40 decreases the upper limit value R (decreases the limit on the pump displacement change amount Δq) as the left / right operation amount difference D decreases. Then, for example, the controller 40 sets the magnitude of the pump displacement change amount Δq to the upper limit value R (or equal to or less than the upper limit value R). Next, the flow proceeds to step S50 or "return".

[0096] In step S50, the controller 40 corrects the pump displacement change amount Δq in accordance with the rotational speed (pump rotational speed N) of the pump 21. Specifically, for example, as shown in Fig. 6, the controller 40 reduces the corrected upper limit value Ra (increases the limit on the pump displacement change amount Δq) as the pump rotational speed N increases. The controller 40 increases the corrected upper limit value Ra (decreases the limit on the pump displacement change amount Δq) as the pump rotational speed N decreases.

[0097] The controller 40 repeats the processes from step S10 to step S50 at predetermined control processing intervals.

[0098] (Effects of the first invention) The effects of the travel control device 1 shown in FIG. 2 are as follows. The travel control device 1 includes a travel device 11b (see FIG. 1), a left travel operation unit 31L, a right travel operation unit 31R, a travel motor 26, and a controller 40. The travel device 11b shown in FIG. 1 has a left travel device 11bL and a right travel device 11bR. The left travel operation unit 31L shown in FIG. 2 is for operating the left travel device 11bL (see FIG. 1). The right travel operation unit 31R is for operating the right travel device 11bR (see FIG. 1). The travel motor 26 drives the travel device 11b (see FIG. 1). The controller 40 controls the travel motor 26 in accordance with the operation of the left travel operation unit 31L and the right travel operation unit 31R.

[0099] [Configuration 1] The controller 40 determines the difference between the operation content of the left traveling operation unit 31L and the operation content of the right traveling operation unit 31R, and changes the limit on the acceleration of the traveling motor 26 in accordance with the difference.

[0100] The above-mentioned [Configuration 1] provides the following effect. The need to limit the acceleration of the travel motor 26 varies depending on the difference in the operation of the left and right travel operation units 31. Therefore, the travel control device 1 is equipped with the above-mentioned [Configuration 1]. Therefore, the limit on the acceleration of the travel motor 26 can be changed depending on the difference in the operation of the left and right travel operation units 31. Therefore, the travel control device 1 can limit the acceleration of the travel motor 26 to an appropriate limit depending on the difference in the operation of the left and right travel operation units 31. As a result, the travel control device 1 can limit the acceleration of the travel device 11b (see FIG. 1) to an appropriate limit depending on the difference in the operation of the left and right travel operation units 31.

[0101] (Effects of the second invention) An operation in which the left traveling operation unit 31L and the right traveling operation unit 31R are operated in the same direction and the left / right operation amount difference D, which is the difference between the operation amount of the left traveling operation unit 31L and the operation amount of the right traveling operation unit 31R, is equal to or less than a predetermined difference value Dth0 (see FIG. 5), is defined as a straight traveling operation. An operation in which at least one of the left traveling operation unit 31L and the right traveling operation unit 31R is operated but is not a straight traveling operation is defined as a steering operation.

[0102] [Configuration 2] The controller 40 limits the acceleration of the travel motor 26 when a steering operation is performed less than the limit on the acceleration of the travel motor 26 when a straight-ahead operation is performed.

[0103] In the above [Configuration 2], the acceleration of the traveling motor 26 is limited less (i.e., the limit is looser) during steering operation compared to when the vehicle is driven straight ahead. This ensures responsiveness of the speed change of the traveling motor 26 to the steering operation of the traveling operation unit 31. As a result, the traveling control device 1 allows the operator to easily perform steering operation.

[0104] In the above [Configuration 2], when a straight-ahead travel operation is performed, the acceleration of the travel motor 26 is more restricted (i.e., the restriction is stricter) than when a steering operation is performed. Therefore, when a straight-ahead travel operation is performed with the travel operation unit 31, a sudden change in the rotational speed of the travel motor 26 is suppressed. As a result, even if an erroneous operation is performed with the travel operation unit 31, the travel distance of the travel device 11b (see FIG. 1) can be reduced. Furthermore, because a sudden change in the rotational speed of the travel motor 26 is suppressed, shocks (vibrations, impacts) of the work machine 10 (see FIG. 1) can be suppressed. When an operator is on board the work machine 10, it is possible to prevent the operator from erroneously operating the travel operation unit 31 due to shocks of the work machine 10 (e.g., lever hunting).

[0105] (Effect of the third invention) The steering operation includes a driving steering operation in which the left driving operation unit 31L and the right driving operation unit 31R are operated in the same direction and the left / right operation amount difference D is greater than a predetermined difference value Dth0 (see FIG. 5).

[0106] [Configuration 3] When a steering operation for traveling is performed, the controller 40 reduces the limit on the acceleration of the traveling motor 26 when the left / right operation amount difference D is the second difference D2 compared to when the left / right operation amount difference D is the first difference D1 (see FIG. 5). The second difference D2 is greater than the first difference D1.

[0107] The above [Configuration 3] provides the following effects. During a steering operation for traveling, the smaller the left / right operation amount difference D, the closer the steering operation is to a straight-ahead operation. The smaller the left / right operation amount difference D, the greater the need to limit the acceleration of the traveling motor 26. On the other hand, during a steering operation for traveling, the larger the left / right operation amount difference D, the greater the need to improve the responsiveness of the speed change of the traveling motor 26 to the operation of the traveling operation unit 31. Therefore, the traveling control device 1 is equipped with the above [Configuration 3]. Therefore, the traveling control device 1 can more appropriately limit the acceleration of the traveling motor 26 in accordance with the need to limit the acceleration of the traveling motor 26.

[0108] (Effect of the fourth invention) [Configuration 4] When a steering operation for traveling is performed, the controller 40 reduces the limit on the acceleration of the traveling motor 26 as the left / right operation amount difference D increases (see FIG. 5).

[0109] The above [Configuration 4] provides the following effect. As described above, the need to limit the acceleration of the traveling motor 26 changes depending on the left / right operation amount difference D. Therefore, the traveling control device 1 is equipped with the above [Configuration 4]. Therefore, the traveling control device 1 can limit the acceleration of the traveling motor 26 more appropriately depending on the need to limit the acceleration of the traveling motor 26.

[0110] (Effect of the fifth invention) [Configuration 5-1] The travel control device 1 includes a pump 21. The pump 21 is driven to rotate by a power source 17 to supply oil to a travel motor 26. The travel motor 26 is driven to rotate by the oil supplied from the pump 21. The controller 40 controls the discharge flow rate (pump discharge flow rate Q) of the pump 21 in accordance with the operation of the left travel operation unit 31L and the right travel operation unit 31R.

[0111] [Configuration 5-2] The controller 40 changes the limit on the pump discharge flow rate change amount ΔQ in accordance with the difference (the difference between the operation content of the left travel operation unit 31L and the operation content of the right travel operation unit 31R), thereby changing the limit on the acceleration of the travel motor 26 in accordance with the difference. The pump discharge flow rate change amount ΔQ is the amount of change in the discharge flow rate of the pump 21 per unit time.

[0112] In the above [Configuration 5-1], the pump 21 supplies oil to the travel motor 26, which drives the travel motor 26 to rotate. Therefore, when the pump discharge flow rate Q changes, the flow rate of oil supplied to the travel motor 26 changes, and the rotation speed of the travel motor 26 changes. In this configuration, when the pump discharge flow rate change amount ΔQ changes, the acceleration of the travel motor 26 changes. Therefore, in the above [Configuration 5-2], the controller 40 changes the limit on the acceleration of the travel motor 26 by changing the limit on the pump discharge flow rate change amount ΔQ. Therefore, by changing the limit on the pump discharge flow rate change amount ΔQ, it is possible to reliably change the limit on the acceleration of the travel motor 26 (see the above [Configuration 1]).

[0113] (Effect of the sixth aspect of the invention) The capacity of the pump 21 is changeable. The controller 40 controls the capacity of the pump 21 in accordance with the operation of the left traveling operation unit 31L and the right traveling operation unit 31R.

[0114] [Configuration 6] The controller 40 changes the limit on the acceleration of the travel motor 26 by changing the limit on the pump displacement change amount Δq, which is the amount of change per unit time in the displacement (pump displacement q) of the pump 21.

[0115] The above [Configuration 6] provides the following effect. When the pump capacity q changes, the pump discharge flow rate Q changes, which changes the flow rate of oil supplied to the travel motor 26 and the rotation speed of the travel motor 26. In this configuration, when the pump capacity change amount Δq changes, the acceleration of the travel motor 26 changes. Therefore, in the above [Configuration 6], the controller 40 changes the limit on the acceleration of the travel motor 26 by changing the limit on the pump capacity change amount Δq. Therefore, by changing the limit on the pump capacity change amount Δq, it is possible to reliably change the limit on the acceleration of the travel motor 26 (see the above [Configuration 1]).

[0116] (Effect of the seventh invention) [Configuration 7] The controller 40 corrects the magnitude of the restriction on the pump displacement change amount Δq in accordance with the pump rotation speed N (see FIG. 6).

[0117] The above [Configuration 7] provides the following effect. The rotation speed of the travel motor 26 varies depending on the discharge flow rate (pump discharge flow rate Q) of the pump 21. The pump discharge flow rate Q is proportional to the product of the capacity of the pump 21 (pump capacity q) and the pump rotation speed N. Therefore, when the pump rotation speed N changes, the appropriate magnitude of the limit on the pump displacement change amount Δq may change. Therefore, in the above [Configuration 7], the magnitude of the limit on the pump displacement change amount Δq is corrected taking into account the pump rotation speed N (see FIG. 6). Therefore, compared to when the magnitude of the limit on the pump displacement change amount Δq is set without taking into account, for example, the pump rotation speed N, the travel control device 1 can set the magnitude of the limit on the pump displacement change amount Δq to an appropriate magnitude corresponding to the pump rotation speed N.

[0118] (Effect of the eighth invention) [Configuration 8] The controller 40 increases the limit on the pump displacement change amount Δq when the pump rotation speed N is a second rotation speed N2 that is greater than the first rotation speed N1 compared to when the pump rotation speed N is a first rotation speed N1 (see FIG. 6).

[0119] The above-mentioned [Configuration 8] achieves the following effect. For a given pump displacement change amount Δq, the higher the pump rotation speed N, the larger the pump discharge flow rate change amount ΔQ, making the pump discharge flow rate Q more likely to change suddenly, and the rotation speed of the traveling motor 26 more likely to change suddenly. Therefore, in the above-mentioned [Configuration 8], the limit on the pump displacement change amount Δq is increased when the second rotation speed N2 is greater than the first rotation speed N1 (see FIG. 6). Therefore, the traveling control device 1 can reduce the pump displacement change amount Δq when the pump rotation speed N is the second rotation speed N2, which is greater, and can suppress sudden changes in the pump discharge flow rate Q. Therefore, the traveling control device 1 can suppress sudden changes in the rotation speed of the traveling motor 26 and can suppress sudden changes in the speed of the traveling device 11b (see FIG. 1). As a result, the travel distance of the traveling device 11b in the event of an incorrect operation is reduced, and shocks in the work machine 10 (see FIG. 1) are suppressed (for details, see "(Effects of the Second Invention)" above).

[0120] Furthermore, for the same pump displacement change amount Δq, the smaller the pump rotation speed N, the smaller the pump discharge flow rate change amount ΔQ, and the more likely it is that the pump discharge flow rate Q changes slowly in response to changes in the operation of the travel operation unit 31. Therefore, in the above-described [Configuration 8], when the pump rotation speed N is the first rotation speed N1, which is lower than the second rotation speed N2, the limit on the pump displacement change amount Δq is reduced (the limit is corrected to the smaller side) (see FIG. 6 ). Therefore, the travel control device 1 can prevent the pump discharge flow rate Q from changing too slowly in response to changes in the operation of the travel operation unit 31 when the pump rotation speed N is the first rotation speed N1, which is low. Therefore, the travel control device 1 can ensure responsiveness in changes in the rotation speed of the travel motor 26 in response to operations of the travel operation unit 31, and can ensure responsiveness in changes in the speed of the travel unit 11b in response to operations of the travel operation unit 31. As a result, the travel control device 1 can ensure responsiveness in changing direction of the undercarriage 11 (undercarriage 11 including the travel unit 11b) in response to operations of the travel operation unit 31.

[0121] (Effect of the ninth invention) [Configuration 9] The controller 40 increases (stricts) the limit on the pump displacement change amount Δq as the pump rotation speed N increases (see FIG. 6).

[0122] The above [Configuration 9] makes it possible to more reliably obtain the effects of the above [Configuration 8].

[0123] (Variation) The above-described embodiments may be modified in various ways. For example, the number of components (including modified examples) of the above-described embodiments may be changed, or some of the components may not be provided. For example, modified examples of the above-described embodiments may be combined in various ways. For example, components may be fixed or connected directly or indirectly to one another. For example, the connections between the components shown in FIG. 2 may be modified. For example, the inclusion relationships between components may be modified in various ways. For example, a component described as a lower-level component included in a higher-level component may not be included in this higher-level component, but may be included in another component. For example, what is described as multiple different components or parts may be combined into a single component or part. For example, what is described as a single component or part (e.g., controller 40) may be provided as multiple different components or parts. For example, various parameters (e.g., setting values, thresholds, ranges, etc.) may be preset in controller 40 or may be directly set by manual operation by an operator. Various parameters may be calculated by controller 40 based on information manually set by an operator, or may be calculated by controller 40 based on information detected by a sensor. For example, the various parameters may not be changed, may be changed by manual operation, or may be changed automatically by the controller 40 in response to certain conditions. For example, the order of the steps in the flowchart shown in Fig. 7 may be changed, or some of the steps may not be performed. For example, each component may have only some of its characteristics (function, arrangement, shape, operation, etc.). [Explanation of symbols]

[0124] 1. Driving control device 11b Running gear 11bL left running gear 11bR Right running gear 17 Power source 21 Pump 26 Travel motor 31L Left driving control unit 31R Right driving control unit 40 Controller D Difference in left and right operation amount (example of difference) D1 1st difference D2 2nd difference Dth0 Predetermined difference value N Pump rotation speed (pump 21 rotation speed) N1 First rotation speed N2 Second rotation speed Δq Pump displacement change amount

Claims

1. a traveling device having a left traveling device and a right traveling device; a left travel operating unit for operating an operating direction to cause the left traveling device to travel forward and an operating direction to cause the left traveling device to travel backward; a right traveling operation unit for operating an operation direction to cause the right traveling device to travel forward and an operation direction to cause the right traveling device to travel backward; a travel motor that drives the travel device; a controller that controls the travel motor in accordance with the operation of the left travel operation unit and the right travel operation unit; Equipped with The controller determines a difference between an operation content including an operation direction of the left traveling operation unit and an operation content including an operation direction of the right traveling operation unit, and changes a limit on the acceleration of the traveling motor according to the difference. Driving control device.

2. The travel control device according to claim 1, An operation in which the left traveling operation unit and the right traveling operation unit are operated in the same operation direction, and a left-right operation amount difference, which is a difference between the operation amount of the left traveling operation unit and the operation amount of the right traveling operation unit, is less than a predetermined difference value, is defined as a straight traveling operation, When an operation in which at least one of the left traveling operation unit and the right traveling operation unit is operated and which is not the straight traveling operation is defined as a steering operation, the controller sets a limit on the acceleration of the travel motor when the steering operation is performed smaller than a limit on the acceleration of the travel motor when the straight travel operation is performed, Driving control device.

3. The travel control device according to claim 2, The steering operation includes a travel steering operation in which the left travel operation unit and the right travel operation unit are operated in the same operation direction, and the left-right operation amount difference is equal to or greater than the predetermined difference value, When the travel steering operation is performed, the controller reduces the limit on the acceleration of the travel motor when the left-right operation amount difference is a second difference that is larger than the first difference, compared to when the left-right operation amount difference is a first difference. Driving control device.

4. The travel control device according to claim 3, When the travel steering operation is performed, the controller reduces the limit on the acceleration of the travel motor as the left-right operation amount difference increases. Driving control device.

5. The driving control device according to any one of claims 1 to 4, a pump that is rotationally driven by a power source to supply oil to the traveling motor; the travel motor is rotationally driven by oil supplied from the pump, the controller controls the discharge flow rate of the pump in accordance with the operation content of the left traveling operation unit and the right traveling operation unit, the controller changes a limit on a pump discharge flow rate change amount, which is a change amount of the discharge flow rate of the pump per unit time, in accordance with the difference, thereby changing a limit on the acceleration of the travel motor in accordance with the difference. Driving control device.

6. The travel control device according to claim 5, The displacement of the pump is variable; the controller controls the capacity of the pump in accordance with the operation of the left traveling operation unit and the right traveling operation unit; the controller changes the limit on the acceleration of the travel motor by changing the limit on the pump displacement change amount, which is the amount of change in the displacement of the pump per unit time; Driving control device.

7. 7. The driving control device according to claim 6, the controller corrects the magnitude of the restriction on the pump displacement change amount in accordance with the rotation speed of the pump. Driving control device.

8. a traveling device having a left traveling device and a right traveling device; a left traveling operation unit for operating the left traveling device; a right traveling operation unit for operating the right traveling device; a travel motor that drives the travel device; a pump whose capacity is changeable and which is rotationally driven by a power source to supply oil to the traveling motor; a controller that controls the travel motor in accordance with the operation of the left travel operation unit and the right travel operation unit, and controls the discharge flow rate of the pump by controlling the capacity of the pump in accordance with the operation of the left travel operation unit and the right travel operation unit; Equipped with the travel motor is rotationally driven by oil supplied from the pump, The controller determines a difference between the operation content of the left traveling operation unit and the operation content of the right traveling operation unit, the controller changes a limit on a pump displacement change amount, which is a change in the displacement of the pump per unit time, so that a limit on a pump discharge flow rate change amount, which is a change in the discharge flow rate of the pump per unit time, changes in accordance with the difference, thereby changing a limit on an acceleration of the travel motor in accordance with the difference; the controller corrects the magnitude of the restriction on the pump displacement change amount in accordance with the rotation speed of the pump. Driving control device.

9. The travel control device according to claim 8, the controller increases the limit on the pump displacement change amount when the rotation speed of the pump is a second rotation speed that is higher than the first rotation speed, compared to when the rotation speed of the pump is a first rotation speed. Driving control device.

10. The travel control device according to claim 9, the controller increases the limit on the pump displacement change amount as the rotation speed of the pump increases; Driving control device.

Images