Construction Machinery

Abstract

To provide a construction machine which can prevent a hunting due to an unintended revolving lever operation caused by a vehicle swing while keeping responsibility to a revolving lever operation intended by an operator.SOLUTION: A construction machine 100 comprises pressure sensors 41, 42 detecting a revolving operation pressure outputted from solenoid proportional control valves 31, 32. A controller 60 calculates a target revolving operation pressure based on an operation amount of an operation lever 10a, calculates a difference between the revolving operation pressure detected by the pressure sensors 41, 42 and the target revolving operation pressure, and restricts a rise rate of the target revolving operation pressure according to the difference.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a construction machine equipped with a spool-type directional control valve that controls the flow of pressurized oil supplied from a hydraulic pump to a swing hydraulic motor, and equipped with a device that generates operating pressure for this directional control valve with an electromagnetic proportional control valve. [Background technology]

[0002] Conventionally, various methods have been proposed for effectively suppressing hunting that occurs when the swing operation lever of a crawler crane or hydraulic excavator is suddenly operated to start or stop the machine. When an operator is shaken by inertial force caused by a sudden operation at start or stop, the swing operation lever may be operated in an unintended direction, i.e., in the neutral direction at start and in the swing operation direction at stop, and then the operator may repeatedly operate the operation lever in the opposite direction to the intended direction to suppress this. The swing vibration phenomenon caused by such operations is called hunting. Patent Document 1 proposes a method for suppressing such hunting.

[0003] Patent Document 1 discloses a swing control device for a construction machine, which includes a hydraulic pump, a swing hydraulic motor that drives a swing body by pressure oil discharged from the hydraulic pump, a swing control valve that controls the flow of oil discharged from the hydraulic pump to control the drive of the swing hydraulic motor, and an operation means that is operated by an operator during a swing operation to output a command signal for driving the swing control valve, and is characterized in that the swing control device includes a swing detection means that detects the sway of the operator by a pressure sensor embedded in a seat, and a valve drive control means that drives and controls the swing control valve based on the sway of the operator detected by the swing detection means and the command signal. As a specific example of the swing control process, it is described that when it is determined that the maximum sway of the operator is greater than a predetermined threshold value, a delay element is added to the command signal output from the operation lever, and the swing control valve is driven in response to the command signal to which the delay element is added. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-222384 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the swing control device described in Patent Document 1, a delay element is added to the command signal output from the operation lever after the pressure sensor detects the operator's shaking, so the occurrence of hunting itself cannot be prevented. Also, while the operator's shaking is being detected, the drive of the swing control valve is delayed with respect to the operation of the swing lever, so that the response to the lever operation is reduced, such as delays in re-acceleration after deceleration and deceleration when stopping.

[0006] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a construction machine that is capable of preventing hunting caused by unintentional rotation lever operation resulting from swaying of the vehicle body, while maintaining responsiveness to the operator's intended rotation lever operation. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a construction machine including a lower traveling body, an upper rotating body rotatably mounted on the lower traveling body, a swing hydraulic motor for driving the upper rotating body to swing, an operation lever for operating the swing hydraulic motor, a hydraulic pump, a swing direction switching valve for controlling a flow of pressure oil supplied from the hydraulic pump to the swing hydraulic motor, a pilot pump, an electromagnetic proportional control valve for outputting a discharge pressure of the pilot pump as a swing operation pressure which is an operation pressure of the swing direction switching valve, and a controller for calculating a target swing operation pressure which is a target value of the swing operation pressure based on an operation amount of the operation lever and outputting a command current to the electromagnetic proportional control valve in accordance with the target swing operation pressure, the construction machine including a pressure sensor for detecting the swing operation pressure, the controller for calculating a difference between the swing operation pressure detected by the pressure sensor and the target swing operation pressure, and limiting a rate of increase of the target swing operation pressure in accordance with the difference. and when the difference falls below a predetermined threshold, correcting the target turning operation pressure so that the increase rate of the target turning operation pressure becomes equal to or less than a predetermined increase rate limit value. It shall be so.

[0008] According to the present invention configured as described above, the rate of increase of the target turning operation pressure is limited according to the difference between the turning operation pressure and the target turning operation pressure, making it possible to suppress hunting caused by unintentional turning lever operation due to swaying of the vehicle body while maintaining responsiveness to the operator's intended turning lever operation. Effect of the Invention

[0009] According to the construction machine of the present invention, it is possible to prevent hunting caused by unintended rotation lever operation due to swaying of the vehicle body while maintaining responsiveness to the operator's intended rotation lever operation. [Brief description of the drawings]

[0010] [Figure 1] 1 is an external view of a hydraulic excavator according to an embodiment of the present invention. FIG. [Diagram 2] FIG. 1 is a configuration diagram of a hydraulic drive system according to an embodiment of the present invention. [Diagram 3] FIG. 4 is a diagram showing the relationship between a lever operation amount and a target operating pressure. [Figure 4] 5 is a flowchart showing a process related to driving of a rotation hydraulic motor by a controller in the embodiment of the present invention. [Diagram 5] 11 is a diagram showing a comparison between the target turning operation pressure and the change in turning operation pressure during turning braking in this embodiment and the prior art. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a hydraulic excavator will be described as an example of a construction machine according to an embodiment of the present invention with reference to the drawings. In each drawing, the same reference numerals are used to designate the same members, and duplicated descriptions will be omitted as appropriate.

[0012] Fig. 1 is an external view of a hydraulic excavator according to this embodiment. In Fig. 1, a hydraulic excavator 100 includes a crawler-type undercarriage 1, an upper rotating body 2 rotatably provided on the undercarriage 1, and a front working mechanism 3 for performing excavation work and the like.

[0013] A pair of left and right traveling hydraulic motors 4 (only the left one is shown) are disposed on the lower traveling body 1. The lower traveling body 1 travels forward or backward as each crawler is independently rotated and driven by the traveling hydraulic motors 4 and their reduction mechanisms, etc.

[0014] The upper rotating body 2 is equipped with an operator's cab 5 in which a driver's seat where an operator sits and the like are arranged, an engine 6 as a prime mover, a hydraulic pump 7 and a pilot pump 8 (shown in FIG. 2) driven by the engine 6, a hydraulic motor 9 for swinging, and the like. The upper rotating body 2 is driven to swing rightward or leftward relative to the lower traveling body 1 by the hydraulic motor 9 for swinging. Inside the operator's cab 5, there are provided an operating lever device 10 for instructing various operations of the hydraulic excavator 100, various instruments for checking the status of the hydraulic excavator 100, a display device for displaying machine information, and the like.

[0015] The front working mechanism 3 is composed of a boom 11, an arm 12, and a bucket 13. The boom 11 is driven vertically by a boom cylinder 14, the arm 12 is driven to the dump side (opening side) or the crowd side (scooping side) by an arm cylinder 15, and the bucket 13 is driven to the dump side or the crowd side by a bucket cylinder 16.

[0016] The hydraulic excavator 100 is provided with a hydraulic oil tank 17 (shown in FIG. 2) that stores hydraulic oil to be supplied to the hydraulic actuators (the traveling hydraulic motor 4, the swing hydraulic motor 9, the boom cylinder 14, the arm cylinder 15, and the bucket cylinder 16). The hydraulic oil (pressurized oil) discharged from the hydraulic pump 7 is supplied to the hydraulic actuators 4, 9, 14-16 via a control valve 18 (shown in FIG. 2). The control valve 18 controls the flow (direction and flow rate) of the hydraulic oil supplied from the hydraulic pump 7 to the hydraulic actuators 4, 9, 14-16.

[0017] Fig. 2 is a configuration diagram of a hydraulic drive system mounted on a hydraulic excavator 100. In Fig. 2, the hydraulic drive system 200 includes a hydraulic pump 7, a pilot pump 8, a swing hydraulic motor 9, a boom cylinder 14, an arm cylinder 15, a bucket cylinder 16, a hydraulic oil tank 17, a control valve 18, electromagnetic proportional control valves 31-38, pressure sensors 41-48, a main relief valve 51, a pilot relief valve 52, swing relief valves 53, 54, a lock valve 55, an operating lever device 10, and a controller 60. Note that portions related to the drive of the traveling hydraulic motor 4 are omitted in Fig. 2.

[0018] The control valve 18 has a swing direction switching valve 21, a boom direction switching valve 22, an arm direction switching valve 23, and a bucket direction switching valve 24. The direction switching valves 21-24 control the flow (direction and flow rate) of pressure oil supplied from the hydraulic pump 7 to the hydraulic actuators 9, 14-16, respectively.

[0019] The electromagnetic proportional control valves 31-38 reduce the discharge pressure (pilot primary pressure) of the pilot pump 8 in response to a command current from the controller 60, and output it as an operating pressure (pilot pressure) of the directional control valves 21-24. Pressure sensors 41-48 are provided in pilot lines connecting the electromagnetic proportional control valves 31-38 and the directional control valves 21-24, respectively. The pressure sensors 41-48 convert the operating pressures output from the electromagnetic proportional control valves 31-38 into pressure signals, and output them to the controller 60.

[0020] The operating lever device 10 generates an operation signal corresponding to the amount of operation (lever operation amount) for each operating direction of the operating lever 10a, and outputs the operation signal to the controller 60. The controller 60 stores the relationship between the lever operation amount and the target operating pressure as shown in Fig. 3 (conversion table 61) for each operating direction of the operating lever 10a. The controller 60 converts the lever operation amount into the target operating pressure based on the conversion table 61, and outputs a command current corresponding to the target operating pressure to the electromagnetic proportional control valves 31 to 38. Hereinafter, the operating pressure and target operating pressure of the swing directional control valve 21 will be referred to as the swing operating pressure and the target swing operating pressure, respectively.

[0021] The main relief valve 51 opens when the discharge pressure of the hydraulic pump 7 exceeds a predetermined pressure, preventing the discharge pressure from rising excessively. The pilot relief valve 52 opens when the discharge pressure of the pilot pump 8 exceeds a predetermined pressure (pilot primary pressure), and keeps the discharge pressure constant. The swing relief valves 53, 54 open when the driving pressure or braking pressure of the swing hydraulic motor 9 exceeds a predetermined pressure, preventing the driving pressure or braking pressure from rising excessively. The lock valve 55 allows or blocks the supply of pilot primary pressure from the pilot pump 8 to the electromagnetic proportional control valves 31-38 according to a command current from the controller 60. When the supply of pilot primary pressure to the electromagnetic proportional control valves 31-38 stops, the hydraulic actuators 9, 14-16 cannot be operated.

[0022] Fig. 4 is a flow chart showing the process related to the drive of the swing hydraulic motor 9 by the controller 60. The controller 60 repeatedly executes the process shown in Fig. 4 at a predetermined control period. Each step will be described below in order.

[0023] The controller 60 calculates a target turning operation pressure based on the amount of operation of the operating lever 10a (step S1), and determines whether the target turning operation pressure is greater than the target turning operation pressure calculated in the previous control cycle (previous target turning operation pressure) (step S2).

[0024] If the determination result in step S2 is NO, the electromagnetic proportional control valves 31-38 are controlled in accordance with the target swing operation pressure (step S10), and the flow ends. As a result, when the swing lever is operated to reduce the target swing operation pressure, the change in the target swing operation pressure is not restricted, so that it is possible to prevent the front working implement 3 from overshooting the target point or colliding with an obstacle against the operator's intention.

[0025] If the determination result in step S2 is YES, it is determined whether or not the target swing operation pressure is greater than a predetermined threshold value Pmin (step S3). Here, the threshold value Pmin is determined for each vehicle body according to the swing operation pressure when the upper swing body 2 starts to swing.

[0026] If the determination result in step S3 is NO, the restriction mode flag is set to OFF (step S14), and the process proceeds to step S10 described later. As a result, the increase rate of the target turning operation pressure is not restricted until the target turning operation pressure reaches the threshold value Pmin, so that a response delay at the time of starting a turning operation can be prevented.

[0027] If the determination result in step S3 is YES, the difference between the turning operation pressure detected by the pressure sensors 41-48 and the target turning operation pressure is calculated (step S4), and it is determined whether or not the difference is smaller than a predetermined threshold value ΔPmin (step S5). Here, the threshold value ΔPmin is used to distinguish between normal turning lever operation and other turning lever operation, and is determined according to the size of the vehicle body, turning performance, and the tracking ability of the electromagnetic proportional valve to the target pressure. Note that if the difference between the target turning operation pressure and the turning operation pressure is equal to or greater than the threshold value ΔPmin, it is regarded as a normal turning lever operation, and if it is less than the threshold value ΔPmin, it is regarded as other turning lever operation.

[0028] If the result of the determination in step S5 is NO, the control mode flag is set to OFF (step S14), and the process proceeds to step S9 described later. As a result, the increase rate of the target turning operation pressure is not limited during normal turning lever operation, so that responsiveness during turning drive can be maintained.

[0029] If the determination result in step S5 is YES, it is determined whether the limit mode flag is OFF (step S6). If the determination result in step S6 is YES, the limit mode flag is set to ON (step S7), an initial value RL0 is set as the increase rate limit value RL of the target turning operation pressure (step S8), the target turning operation pressure is corrected so that the increase rate (increase width per control cycle) of the target turning operation pressure is equal to or less than the increase rate limit value RL (step S9), the electromagnetic proportional control valves 31 to 38 are controlled according to the target turning operation pressure (step S10), and the flow is terminated. As a result, when a turning lever operation that swings in small increments (hereinafter referred to as an abnormal turning lever operation) is performed, the increase rate of the turning operation pressure is suppressed to or less than the increase rate limit value RL, so that hunting due to unintended turning lever operation caused by the swinging of the vehicle body can be suppressed.

[0030] If the determination result in step S6 is NO, a predetermined value ΔRL is added to the increase rate limit value RL (step S11). As a result, when an abnormal swing lever operation is continuously performed, the limit on the increase rate of the target swing operation pressure is relaxed according to the duration of the operation, so that it is possible to improve responsiveness when the operator intentionally performs an abnormal swing lever operation. Note that if it is desired to quickly release the limit on the increase rate of the target swing operation pressure, the predetermined value ΔRL should be made smaller, and if it is desired to slowly release the limit, the predetermined value ΔRL should be made larger.

[0031] Following step S11, it is determined whether the increase rate limit value RL is greater than a predetermined threshold value RLmax (step S12). Here, the threshold value RLmax is, for example, the maximum increase rate of the target turning operation pressure at which the operator does not feel a sudden acceleration, and is determined based on the turning performance of the vehicle body. If the determination result of step S12 is NO, the process proceeds to step S9.

[0032] If the determination result in step S12 is YES, the maximum climb rate RLmax is set to the climb rate limit value RL (step S13), and the process proceeds to step S9. This keeps the climb rate limit value RL below the maximum climb rate RLmax, making it possible to prevent the operator from feeling a sudden acceleration during an abnormal swing lever operation.

[0033] Fig. 5 is a diagram showing the target turning operation pressure and the change in turning operation pressure during turning braking in comparison with the conventional technology. The solid line in Fig. 5 shows the turning operation pressure, and the dotted line shows the target turning operation pressure. The upper diagram in Fig. 5 shows the state before turning control was applied, and the lower diagram shows the state after turning control was applied.

[0034] In the conventional technology, when the swing lever is operated with small swings (unintentional swing lever operation by the operator) during swing braking, the target swing operation pressure changes in response to the swing lever operation. As a result, the swing hydraulic motor 9 repeats acceleration and deceleration, causing hunting in the vehicle body.

[0035] In contrast, in this embodiment, when the operation lever 10a is operated to the swing drive side, the target swing operation pressure rises with a delay from the swing lever operation, and when the operation lever 10a is operated to the swing brake side, the target swing operation pressure falls following the swing lever operation. As a result, the acceleration of the swing hydraulic motor 9 due to unintended swing lever operation by the operator is suppressed, so that the upper swing body 2 can be braked without causing hunting in the vehicle body.

[0036] (summary) In this embodiment, the equipment includes a lower traveling body 1, an upper rotating body 2 rotatably mounted on the lower traveling body 1, a hydraulic motor for rotation 9 for driving the upper rotating body 2 to rotate, an operation lever 10a for operating the hydraulic motor for rotation 9, a hydraulic pump 7, a direction control valve for rotation 21 for controlling the flow of pressure oil supplied from the hydraulic pump 7 to the hydraulic motor for rotation 9, a pilot pump 8, and an electromagnetic proportional control valve 31 for outputting the discharge pressure of the pilot pump 8 as a swing operation pressure which is the operation pressure of the direction control valve for rotation 21. , 32, and a controller 60 that calculates a target operating pressure, which is a target value of the swing operating pressure, based on the operation amount of the operating lever 10a and outputs a command current to the electromagnetic proportional control valves 31, 32 in accordance with the target swing operating pressure, the construction machine 100 is provided with pressure sensors 41, 42 that detect the swing operating pressure, and the controller 60 calculates the difference between the swing operating pressure detected by the pressure sensors 41, 42 and the target swing operating pressure, and limits the rate of increase of the target swing operating pressure in accordance with the difference.

[0037] According to the present embodiment configured as described above, the rate of increase of the target turning operation pressure is limited according to the difference between the turning operation pressure and the target turning operation pressure, making it possible to suppress hunting caused by unintentional turning lever operation due to swaying of the vehicle body while maintaining responsiveness to the operator's intended turning lever operation.

[0038] Furthermore, when the difference between the turning operation pressure and the target turning operation pressure falls below a predetermined threshold ΔP, the controller 60 corrects the target turning operation pressure so that the increase rate of the target turning operation pressure is equal to or less than a predetermined increase rate limit value RL. This makes it possible to suppress the increase rate of the target turning operation pressure to equal to or less than the predetermined increase rate limit value RL when a turning lever operation is performed such that the target turning operation pressure changes within a range of the predetermined threshold ΔP relative to the turning operation pressure.

[0039] Furthermore, the controller 60 increases the increase rate limit value RL according to the duration of the state in which the difference between the swing operation pressure and the target swing operation pressure falls below a predetermined threshold value ΔPmin. As a result, when an abnormal swing lever operation (a swing lever operation with small swings) is continuously performed, the limit on the increase rate of the target swing operation pressure is relaxed according to the duration, so that when a swing lever operation with small swings is performed transiently (against the operator's intention), shock to the vehicle body is suppressed, while when the swing lever operation is performed continuously (i.e. in accordance with the operator's intention), the swing hydraulic motor 9 can be driven faithfully in response to the swing lever operation.

[0040] Although the embodiment of the present invention has been described above in detail, the present invention is not limited to the above-mentioned embodiment and includes various modified examples. For example, the above-mentioned embodiment has been described using a hydraulic excavator as an example, but the present invention is also applicable to other construction machines (e.g., crawler cranes). Furthermore, the above-mentioned embodiment has been described in detail to explain the present invention in an easily understandable manner, and the present invention is not necessarily limited to those having all of the configurations described. [Explanation of symbols]

[0041] 1...lower traveling body, 2...upper rotating body, 3...front working device, 4...traveling hydraulic motor, 5...operator cab, 6...engine, 7...hydraulic pump, 8...pilot pump, 9...swing hydraulic motor, 10...operating lever device, 10a...operating lever, 11...boom, 12...arm, 13...bucket, 14...boom cylinder, 15...arm cylinder, 16...bucket cylinder, 17...hydraulic oil tank, 18...control valve, 21-24...directional control valve, 31-38...electromagnetic proportional control valve, 41-48...pressure sensor, 51...main relief valve, 52...pilot relief valve, 53,54...swing relief valve, 55...lock valve, 60...controller, 61...conversion table, 100...hydraulic excavator (construction machinery), 200...hydraulic drive unit.

Claims

1. A lower running body; An upper rotating body rotatably attached on the lower traveling body; A hydraulic motor for rotating the upper rotating body; An operation lever for operating the swing hydraulic motor; A hydraulic pump; a swing direction control valve for controlling a flow of pressure oil supplied from the hydraulic pump to the swing hydraulic motor; A pilot pump; an electromagnetic proportional control valve that outputs the discharge pressure of the pilot pump as a swing operating pressure which is the operating pressure of the swing directional control valve; a controller that calculates a target swing operation pressure, which is a target value of the swing operation pressure, based on an operation amount of the operation lever, and outputs a command current to the electromagnetic proportional control valve in accordance with the target swing operation pressure, A pressure sensor is provided to detect the turning operation pressure, The controller calculates a difference between the turning operation pressure detected by the pressure sensor and the target turning operation pressure, limits an increase rate of the target turning operation pressure in accordance with the difference, and corrects the target turning operation pressure so that the increase rate of the target turning operation pressure becomes equal to or less than a predetermined increase rate limit value when the difference falls below a predetermined threshold value. A construction machine characterized by:

2. 2. The construction machine according to claim 1, The controller increases the increase rate limit value in accordance with a duration of a state in which the difference is below the predetermined threshold value. A construction machine characterized by:

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