JP6101974B2 - Construction machinery - Google Patents

Description

  The present invention relates to a construction machine such as a hydraulic excavator, a wheel loader, or a hydraulic crane.

  In general, a hydraulic excavator, which is a typical example of a construction machine, is, for example, a self-propelled lower traveling body, an upper revolving body that is turnable on the lower traveling body, and a front swinging of the upper revolving body. It is comprised by the work apparatus attached so that it was possible (can be moved up and down).

  The upper swing body includes a swing frame (base) on which a working device is mounted, a support structure member, an engine (prime mover) mounted on the swing frame, a hydraulic pump driven by the engine, and the hydraulic pump. Supply and discharge of pressure oil to and from the boom cylinder (hydraulic cylinder) that changes the posture of the boom of the work device by extending and contracting based on the pressure oil of the hydraulic pump and the boom pump The control valve (direction control valve) for controlling the control valve, the remote control valve (operation means) for operating the control valve, and the oil (operating oil) connected to the engine and discharged from the boom cylinder are used to drive the oil energy. A regenerative motor that regenerates as an engine assist force, and a controller that controls the capacity of the regenerative motor. It is made (e.g., see Patent Document 1).

  Here, the construction machine by patent document 1 becomes a structure which suppresses the pressure vibration which generate | occur | produces in a hydraulic circuit when a boom cylinder is suddenly operated by capacity | capacitance control of a regenerative motor. Specifically, during the operation of moving the boom of the working device in the direction of its own weight (boom lowering operation), the controller detects the vibration component of the oil discharged from the oil chamber on the bottom side of the boom cylinder, that is, the bottom side pressure. The corrected flow rate obtained by multiplying the vibration component excluding the holding pressure applied by the work equipment's own weight, etc., and the gain is added to the target discharge flow rate of the boom cylinder according to the boom lowering operation amount, and the capacity of the regenerative motor is calculated from the total flow rate. Control.

  At this time, since the corrected flow rate obtained by multiplying the vibration component by the gain is fed back to the capacity of the regenerative motor, vibration of the bottom side pressure can be suppressed. That is, when the bottom side pressure increases, the capacity of the regenerative motor increases and the amount of discharged oil increases, and when the bottom side pressure decreases, the capacity of the regenerative motor decreases and the amount of discharged oil decreases. Thereby, the pressure vibration of the bottom side pressure can be attenuated.

JP 2008-075753 A (Patent No. 4973077)

  The configuration described in Patent Document 1 controls pressure vibration based on a sudden operation of the boom cylinder or the like by controlling the capacity of the regenerative motor during the boom lowering operation. However, the configuration described in Patent Document 1 does not target an operation (boom raising operation) for moving the boom of the working device in the anti-self-weight direction. For this reason, the pressure vibration generated in the hydraulic circuit during the boom raising operation cannot be suppressed as it is.

  On the other hand, by applying the capacity control of the regenerative motor of Patent Document 1 to the capacity control of the hydraulic pump, it is conceivable to suppress (attenuate) the pressure vibration generated in the hydraulic circuit during the boom raising operation. However, if the regenerative motor displacement control is simply applied to the displacement control of the hydraulic pump as it is, for example, the initial speed of the boom raising operation may be delayed and the operability may be reduced.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to suppress the vibration of the bottom side pressure accompanying the sudden operation of the hydraulic cylinder and to ensure the initial speed (initial speed) of the working device. It is to provide a construction machine that can achieve both.

  A construction machine according to the present invention includes a base body to which a working device is attached, a prime mover mounted on the base body, a variable displacement hydraulic pump that is driven by the prime mover and has a capacity variable mechanism that increases and decreases capacity, and the hydraulic pump. A hydraulic cylinder that changes the posture of the working device by extending and contracting based on the pressure oil from the cylinder, and is provided between the hydraulic pump and the hydraulic cylinder, and controls the supply and discharge of the pressure oil to the hydraulic cylinder A directional control valve, an operating means for operating the directional control valve, and a controller for controlling the capacity variable mechanism.

  In order to solve the above-described problem, the feature of the configuration adopted by the invention of claim 1 is that the number of revolutions detecting means for detecting the number of revolutions of the prime mover, and the amount of operation detecting means for detecting the amount of operation of the operating means, And a pressure detection means for detecting a bottom side pressure and a rod side pressure of the hydraulic cylinder, respectively, and the controller calculates a target reference flow rate of the hydraulic pump according to a detection value of the operation amount detection means. A flow rate calculating means; a thrust fluctuation speed calculating means for calculating a fluctuation speed of the thrust of the hydraulic cylinder based on a detection value of the pressure detecting means; and a fluctuation speed calculated by the thrust fluctuation speed calculating means is negative. , Calculating a correction flow rate proportional to the fluctuation speed, and based on the correction flow rate, the target reference flow rate calculated by the target reference flow rate calculation means, and the detection value of the rotation speed detection means. Is to have a structure having a target capacity calculation means for calculating a target capacity of the hydraulic pump.

  According to a second aspect of the present invention, the working device includes a boom that is rotatably attached to the base body, and a boom cylinder that rotates the boom, and the hydraulic cylinder is configured as the boom cylinder, The target capacity calculation means is based on the corrected flow rate, the target reference flow rate, and the detection value of the rotation speed detection means when the boom is rotated in the anti-self-weight direction and the fluctuation speed is negative. Therefore, the target capacity of the hydraulic pump is calculated.

  According to a third aspect of the present invention, the hydraulic pump includes a single hydraulic pump, and the target capacity calculation unit includes a total flow rate obtained by adding the target reference flow rate and the correction flow rate, and a detection value of the rotation speed detection unit. The target capacity of the hydraulic pump is calculated based on the above.

  According to a fourth aspect of the present invention, the hydraulic pump includes two hydraulic pumps, a first hydraulic pump and a second hydraulic pump, and the target capacity calculating means includes the target reference flow rate and the rotation speed detecting means. Based on the detected value, the first target capacity calculating means for calculating the target capacity of the first hydraulic pump, and the second hydraulic pressure based on the corrected flow rate and the detected value of the rotation speed detecting means. The second target capacity calculating means for calculating the target capacity of the pump is provided.

  The invention according to claim 5 is provided with a stroke detection means for detecting a stroke amount of the hydraulic cylinder, and the target capacity calculation means is configured to adjust the correction flow rate based on a detection value of the stroke detection means. It is in.

  According to the first aspect of the present invention, it is possible to achieve both the suppression of the vibration of the bottom side pressure accompanying the sudden operation of the hydraulic cylinder and the securing of the initial speed (initial speed) of the working device, and the operability of the working device. Can be improved.

  That is, the controller that controls the displacement mechanism of the hydraulic pump calculates the target displacement of the hydraulic pump only when the hydraulic cylinder thrust is fluctuating at a negative target speed based on the operation amount of the operation means. Instead, the correction flow rate proportional to the fluctuation speed of the thrust of the hydraulic cylinder is also used. Thereby, when the fluctuation speed of the thrust of the hydraulic cylinder is negative, the control of the capacity of the hydraulic pump can be made in consideration of the correction flow rate for supplementing the thrust of the hydraulic cylinder with respect to the target reference flow rate. As a result, it is possible to suppress (attenuate) the vibration of the bottom side pressure when the hydraulic cylinder suddenly operates.

  In addition, the correction flow rate for suppressing the vibration of the bottom side pressure is taken into consideration when the fluctuation speed of the thrust of the hydraulic cylinder is negative (fluctuation speed <0), but the fluctuation speed is positive (fluctuation speed> 0). The case is not taken into account. That is, the correction flow rate for reducing the thrust of the hydraulic cylinder is not added to the control of the capacity of the hydraulic pump. Thereby, it can suppress that the thrust of a hydraulic cylinder falls in the operation | movement initial stage of a working device, and can ensure the initial speed of a working device. For example, compared with a configuration that controls the capacity of the hydraulic pump by taking into account the correction flow rate according to the deviation between the bottom side pressure and the holding pressure applied by the working device's own weight, etc. (feedback using the deviation between the holding thrust and the current thrust). Thus, the initial speed of the working device can be improved.

  According to the second aspect of the present invention, it is possible to achieve both suppression of the vibration of the bottom side pressure accompanying the sudden movement of the boom cylinder and securing the initial speed of the boom. In particular, suppression of boom vibration when a boom raising operation (operation to rotate the boom upward in the anti-self-weight direction) from a state where a part of the work device is grounded (the holding pressure is zero) And securing the initial speed can be achieved at a high level.

  According to the invention of claim 3, the target capacity of the hydraulic pump is calculated using the total flow rate obtained by adding the target reference flow rate and the correction flow rate. Thereby, it is possible to achieve both suppression of vibration of the hydraulic cylinder and securing of the initial speed of the working device in a hydraulic system constituted by one hydraulic pump.

  According to invention of Claim 4, the capacity | capacitance of a 1st hydraulic pump can be made into a thing according to a target reference flow volume, and the capacity | capacitance of a 2nd hydraulic pump can be made into a thing according to correction | amendment flow volume. Thereby, it is possible to achieve both suppression of vibration of the hydraulic cylinder and securing of the initial speed of the working device in a hydraulic system constituted by two hydraulic pumps.

  According to the fifth aspect of the invention, since the correction flow rate is adjusted based on the stroke amount of the hydraulic cylinder, it is based on the compressibility of oil (working oil) existing between the hydraulic pump and the bottom side oil chamber of the hydraulic cylinder. The capacity of the hydraulic pump can be controlled in consideration of a decrease in thrust response. Thereby, coexistence with suppression of the vibration of a hydraulic cylinder and ensuring of the initial speed of a working device can be performed at a higher level.

1 is a front view showing a hydraulic excavator according to a first embodiment. It is a hydraulic circuit diagram which shows the structure for driving a boom cylinder. It is a flowchart which shows the process by the controller in FIG. It is a characteristic diagram which shows an example of the relationship between the boom raising operation amount and the target reference flow rate. It is a characteristic diagram which exaggerates and shows an example of the time change of the bottom side pressure of a boom cylinder, raising operation amount, cylinder thrust, target standard flow, and amendment flow. It is a hydraulic circuit diagram which shows the structure for driving the boom cylinder by 2nd Embodiment. It is a flowchart which shows the process by the controller in FIG. It is a hydraulic circuit diagram which shows the structure for driving the boom cylinder by 3rd Embodiment. It is a flowchart which shows the process by the controller in FIG. It is a hydraulic circuit diagram for demonstrating the relationship between the stroke amount of a boom cylinder, and a vibration suppression effect. It is a characteristic diagram which shows an example of the relationship between the displacement of a boom cylinder, and a correction coefficient. It is a characteristic diagram which shows another example of the relationship between the displacement of a boom cylinder, and a correction coefficient.

  Hereinafter, a construction machine according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings, taking as an example a case where the construction machine is applied to a hydraulic excavator.

  1 to 5 show a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a hydraulic excavator as a typical example of a construction machine used for earth and sand excavation work. The hydraulic excavator 1 includes a self-propelled crawler-type lower traveling body 2, an upper revolving body 3 that is turnably provided on the lower traveling body 2 and that forms a vehicle body (main body) together with the lower traveling body 2, It is comprised by the below-mentioned working apparatus 11 attached to the front side of this upper revolving body 3 and the front direction of a back direction so that rotation (inclination possible) is possible. The excavator 1 performs excavation work of earth and sand using the working device 11.

  Here, the lower traveling body 2 includes a track frame 2A, drive wheels 2B provided on the left and right sides of the track frame 2A, and drive wheels 2B on the left and right sides of the track frame 2A. It comprises an idler wheel 2C provided on the opposite side, a drive wheel 2B and a crawler belt 2D wound around the idler wheel 2C (both shown only on the left side). The left and right drive wheels 2B are rotationally driven by left and right travel motors (not shown) made of a hydraulic motor or the like.

  On the other hand, the upper turning body 3 is attached to the lower traveling body 2 via a turning device (not shown) made of a hydraulic motor or the like, and is driven to turn with respect to the lower traveling body 2 by the turning device. The upper revolving unit 3 forms a support structure and a revolving frame 4 as a base with a working device 11 attached to the front side in the front and rear directions, and a cab 5 that is mounted on the left front side of the revolving frame 4 and forms a driver's cab. A building cover 6 that houses an engine 22, a hydraulic pump 23, a boom direction control valve 25 and the like (see FIG. 2), which will be described later, mounted on the revolving frame 4 at the rear side of the cab 5, and a revolving frame 4 and a counterweight 7 that is attached to the rear part of the 4 and balances the weight with the work device 11.

  Here, a driver's seat (not shown) on which an operator is seated is provided inside the cab 5, and left and right operating lever devices (operating means) are provided on both sides of the driver's seat in the left and right directions. Hereinafter, work operation levers 8A and 8B (refer to FIG. 2) are provided. These left and right operation control levers 8A and 8B are for performing a turning operation of the upper swing body 3 and a turning operation (up and down operation) of the work device 11. The cab 5 is provided with left and right traveling levers and pedals (not shown) located in front of the driver's seat. These left and right traveling levers / pedals are for performing the traveling operation of the lower traveling body 2.

  As shown in FIG. 2, one of the left and right work operation levers 8A, 8B is for operating (switching operation) a boom direction control valve 25 described later. When the operator operates one of the work operation levers 8A, the boom direction control valve 25 is switched based on this operation, and boom cylinders 15 and 16 described later are driven, that is, expand and contract (extend and contract). Thereby, the below-mentioned boom 12 can be rotated (back-and-forth movement). Further, in the cab 5, for example, a controller 45 (see FIG. 2), which will be described later, is provided on the lower side of the driver's seat and behind the backrest.

  On the other hand, as shown in FIG. 1, the working device 11 includes a boom 12 attached (connected) to a front portion of the revolving frame 4 by a pin connection so as to be rotatable (can be moved up and down), and a tip of the boom 12. The arm 13 is attached (connected) by pin coupling so as to be pivotable (can be moved up and down), and the bucket 14 is pivotally attached (connected) to the tip side of the arm 13 by pin coupling. And. Left and right boom cylinders 15 and 16, arm cylinders 17, and bucket cylinders 18 as hydraulic cylinders are attached to the boom 12, arm 13, and bucket 14, respectively. The left and right boom cylinders 15 and 16 rotate the boom 12 with respect to the revolving frame 4 (upward and downward movement), and the arm cylinder 17 rotates (upward and downward movement) the arm 13 with respect to the boom 12. The bucket cylinder 18 rotates the bucket 14 with respect to the arm 13.

  The boom cylinders 15 and 16, the arm cylinder 17, and the bucket cylinder 18 are adapted to change the posture of the work device 11 by expanding and contracting based on pressure oil from a hydraulic pump 23 described later. That is, during excavation work such as earth and sand, the hydraulic cylinders (boom cylinders 15 and 16, arm cylinder 17 and bucket cylinder 18) are expanded and contracted based on the operation of the operation levers 8A and 8B, and the boom 12 and the arm 13 are expanded. The bucket 14 is rotated while rotating (swinging up and down). Thereby, earth and sand etc. can be excavated by the front end side of the bucket 14.

  Here, as shown in FIG. 2, the left and right boom cylinders 15 and 16 are slidably inserted into the tubes 15A and 16A and the tubes 15A and 16A, and the tubes 15A and 16A have a bottom side. Pistons 15B, 16B defined in oil chambers 15C, 16C and rod-side oil chambers 15D, 16D; rods 15E, 16E having proximal ends fixed to the pistons 15B, 16B and distal ends protruding outside the tubes 15A, 16A; It is comprised by. The bottom side oil chamber may be referred to as a head side oil chamber, but the following description will be described as a bottom side oil chamber.

  Next, a hydraulic circuit 21 for driving the boom cylinders 15 and 16 will be described with reference to FIG.

  The hydraulic circuit 21 is for driving the boom cylinders 15 and 16. The hydraulic circuit 21 includes an engine 22, a hydraulic pump 23, a hydraulic oil tank 24, a boom direction control valve 25, and the like, which will be described later, in addition to the aforementioned operation lever 8 A and boom cylinders 15 and 16. .

  The engine 22 is provided on the turning frame 4 between the cab 5 and the counterweight 7. The engine 22 is constituted by a diesel engine, for example, and serves as a prime mover (rotation source) for rotationally driving a hydraulic pump 23, a pilot pump (not shown), etc., which will be described later. When the hydraulic excavator 1 is configured as a hybrid hydraulic excavator, the assist power generation motor is also rotationally driven by the engine 22 in addition to the hydraulic pump 23 and the like.

  The hydraulic pump 23 is driven by the engine 22, and the hydraulic pump 23 constitutes a hydraulic source together with the hydraulic oil tank 24. In addition to the boom cylinders 15 and 16, the arm cylinder 17, and the bucket cylinder 18 of the work device 11, the hydraulic pump 23 drives a hydraulic motor for traveling the lower traveling body 2, a hydraulic motor for rotating the upper revolving body 3, and the like. It becomes a power source to do. The hydraulic pump 23 pressurizes the hydraulic oil (oil) in the hydraulic oil tank 24 and discharges it toward the control valve. FIG. 2 shows only the boom direction control valve 25 for controlling the supply and discharge of the pressure oil to and from the boom cylinders 15 and 16 among the plurality of direction control valves constituting the control valve.

  The hydraulic pump 23 is configured as, for example, a swash plate type, radial piston type or oblique axis type variable displacement hydraulic pump. That is, the hydraulic pump 23 has a capacity variable portion 23A made of a swash plate or a slanted shaft, and a capacity variable mechanism 23B that drives (tilts and drives) the capacity variable portion 23A. The capacity variable mechanism 23B drives (inclination drive) the capacity variable section 23A based on a command from the controller 45 described later. As a result, the capacity variable portion 23A (tilt angle) changes and the pump capacity (displacement volume) of the hydraulic pump 23 can be increased or decreased (the discharge flow rate of the hydraulic oil can be increased or decreased according to the tilt angle. it can).

  The boom direction control valve 25 is provided between the hydraulic pump 23 and the boom cylinders 15 and 16, and the boom direction control valve 25 constitutes a direction control valve according to the present invention. The boom direction control valve 25 controls supply and discharge of pressure oil to and from the boom cylinders 15 and 16. The boom direction control valve 25 constitutes a control valve (control valve group) together with various direction control valves (not shown). That is, the boom direction control valve 25 is an arm direction control valve that controls supply and discharge of pressure oil to the arm cylinder 17, a bucket direction control valve that controls supply and discharge of pressure oil to the bucket cylinder 18, Along with a traveling direction control valve that controls the supply and discharge of pressure oil to and from the hydraulic motor, and a turning direction control valve that controls the supply and discharge of pressure oil to and from the turning hydraulic motor (both not shown) It constitutes a valve.

  The boom direction control valve 25 is constituted by, for example, a 6-port 3-position hydraulic pilot type direction control valve. The boom direction control valve 25 is connected to the hydraulic pump 23 via the discharge line 26 and is connected to the hydraulic oil tank 24 via the center bypass line 27 and the return line 28. In addition, the boom direction control valve 25 is connected to the bottom oil chambers 15C and 16C of the boom cylinders 15 and 16 via the bottom side conduit 29, and is connected to the rods of the boom cylinders 15 and 16 via the rod side conduit 30. The side oil chambers 15D and 16D are connected. In addition, although a bottom side pipe line may be called a head side pipe line, the following description is described as a bottom side pipe line.

  The boom direction control valve 25 is operated (switching operation) by a work operation lever 8A as an operation means. For this purpose, a pair of hydraulic pilot portions 25A and 25B are provided on both ends of the boom direction control valve 25. A pilot pressure (switching signal) based on the operation of the work operation lever 8A is supplied to the hydraulic pilot portions 25A and 25B.

  For example, as shown in FIG. 2, based on the operation of the operation lever 8A, the pilot pressure (switching signal) proportional to the amount of operation is changed to one of the ones via one pilot line (switching signal line) 31. When supplied to the hydraulic pilot unit 25A, the boom direction control valve 25 is switched from the neutral position (C) to the switching position (A). In this case, the discharge pipeline 26 is connected to the bottom pipeline 29 and the rod pipeline 30 is connected to the return pipeline 28. Thereby, the pressure oil discharged from the hydraulic pump 23 is supplied to the bottom side oil chambers 15C and 16C of the boom cylinders 15 and 16 via the discharge pipe 26 and the bottom side pipe 29, and the rod side oil chamber 15D and 16D hydraulic oil is discharged as return oil to the hydraulic oil tank 24 through the rod side pipe 30 and the return pipe 28. As a result, the boom cylinders 15 and 16 extend (the amount of protrusion of the rods 15E and 16E from the tubes 15A and 16A increases).

  On the other hand, based on the operation of the operation lever 8A, the pilot pressure (switching signal) proportional to the amount of operation is supplied to the other hydraulic pilot section 25B via the other pilot line (switching signal line) 32. Then, the boom direction control valve 25 is switched from the neutral position (C) to the switching position (B). In this case, the discharge line 26 is connected to the rod side line 30, and the bottom side line 29 is connected to the return line 28. Thereby, the pressure oil discharged from the hydraulic pump 23 is supplied to the rod side oil chambers 15D and 16D of the boom cylinders 15 and 16 via the discharge pipe line 26 and the rod side pipe line 30, and the bottom side oil chamber 15C and The 16C hydraulic oil is discharged as return oil to the hydraulic oil tank 24 via the bottom side pipe line 29 and the return pipe line 28. As a result, the boom cylinders 15 and 16 are reduced (the amount of protrusion of the rods 15E and 16E from the tubes 15A and 16A is reduced).

  Further, when the work control lever 8A is in the neutral position, no pilot pressure is supplied to the hydraulic pilot portions 25A and 25B, so the boom direction control valve 25 is in the neutral position (C). In this case, the discharge line 26 is connected to the center bypass line 27, and the pressure oil discharged from the hydraulic pump 23 is discharged to the hydraulic oil tank 24. At this time, the bottom side conduit 29 and the rod side conduit 30 are disconnected from the discharge conduit 26 and the return conduit 28, and the movement (extension and contraction) of the boom cylinders 15 and 16 stops.

  By the way, in FIG. 1, a part of the working device 11 including the boom 12, the arm 13, the bucket 14, and the like serving as arms is in contact with the ground (grounded). On the other hand, although illustration is omitted, when the working device 11 is floating (not grounded), the boom cylinders 15 and 16 are placed in a direction in which the weight of the working device 11 reduces the boom cylinders 15 and 16. Join. For this reason, the holding pressure for holding the working device 11 in the floating position acts on the bottom side oil chambers 15C, 16C of the boom cylinders 15, 16.

  Here, when the working device 11 is rotated upward and downward by the boom cylinders 15 and 16 (the boom 12 is moved up and down), an abrupt operation is performed (the boom cylinders 15 and 16 are suddenly operated), The pressure of the hydraulic oil in the bottom side oil chambers 15C and 16C of the boom cylinders 15 and 16 tends to vibrate. For example, when the characteristic line 51 of the two-dot chain line in FIG. 5 performs an abrupt boom raising operation (an operation to rotate the boom 12 upward in the anti-self-weight direction) from a state where a part of the work device 11 is grounded. The pressure behavior of the bottom side oil chambers 15C, 16C is exaggerated.

  As is apparent from the characteristic line 51 of the two-dot chain line, the pressure in the bottom side oil chambers 15C and 16C converges on the holding pressure with vibration, and until the vibration is attenuated (until it converges on the holding pressure). ) Takes time. Such pressure vibration fluctuates the rotation speed of the working device 11 (boom 12) (makes it unstable), lowers the operability, and in addition, the hydraulic pump 23 communicated with the bottom side oil chambers 15C, 16C. The load of the engine 22 becomes oscillating, and the fuel consumption of the engine 22 that drives the hydraulic pump 23 may be reduced.

  On the other hand, the configuration described in Patent Document 1 described above aims to suppress pressure vibration based on a sudden operation of the hydraulic cylinder or the like by controlling the capacity of the regenerative motor during the boom lowering operation. Specifically, the vibration component of the oil discharged from the oil chamber on the bottom side of the boom cylinder, that is, the vibration component excluding the holding pressure applied from the bottom side pressure due to the weight of the working device, etc., is multiplied by the gain. In addition, it is added to the target discharge flow rate of the boom cylinder corresponding to the boom lowering operation amount, and the capacity of the regenerative motor is controlled from the total flow rate. However, the configuration described in Patent Document 1 does not target the operation of moving the boom of the working device in the anti-weight direction, that is, the boom raising operation of rotating the boom upward. For this reason, as it is, the pressure vibration generated in the hydraulic circuit during the boom raising operation cannot be suppressed.

  On the other hand, by applying the capacity control of the regenerative motor of Patent Document 1 to the capacity control of the hydraulic pump, it is conceivable to suppress (attenuate) the pressure vibration generated in the hydraulic circuit during the boom raising operation. For example, the target supply flow rate of the boom cylinder according to the boom raising operation amount is obtained by multiplying the vibration component excluding the holding pressure applied by the weight of the work equipment from the pressure of the bottom oil chamber (bottom side pressure) with the gain. It is conceivable to control the capacity of the hydraulic pump from the total flow rate.

  In this case, the corrected flow rate obtained by multiplying the vibration component by the gain is fed back to the capacity of the hydraulic pump that supplies the pressure oil to the bottom side oil chamber. That is, when the bottom side pressure is larger than the holding pressure, the discharge flow rate is reduced by adding a negative correction flow rate to the hydraulic pump displacement control. Conversely, when the bottom side pressure is smaller than the holding pressure. The discharge capacity is increased by adding a positive correction flow rate to the capacity control of the hydraulic pump. Thereby, it is considered that the pressure vibration during the boom raising operation can be suppressed. However, immediately after the start of the boom raising operation, if the thrust of the boom cylinder is not made larger than the holding pressure equivalent thrust, the boom does not rotate due to the influence of the inertia of the working device or the rotation speed ( The initial speed may be slow. For this reason, in the structure which feeds back the fluctuation | variation component from the above holding pressures, there exists a possibility that a working device (boom) may become difficult to rotate by removing the thrust more than a holding pressure equivalent thrust.

  On the other hand, in the first embodiment, when the fluctuation speed of the thrust of the boom cylinders 15 and 16 is negative, the capacity of the hydraulic pump 23 is added in consideration of the correction flow rate for compensating the thrust of the boom cylinders 15 and 16. It is set as the structure which controls. Then, next, the structure for controlling the capacity | capacitance of such a hydraulic pump 23 is demonstrated.

  The rotation sensor 33 detects the rotation speed (rotation speed) of the engine 22, and the rotation sensor 33 constitutes rotation speed detection means (rotation speed detection means) according to the present invention. The rotation sensor 33 is connected to a controller 45 described later via a signal line 34, and the rotation sensor 33 outputs a detection signal corresponding to the detected number of rotations to the controller 45. For example, the controller 45 can calculate the discharge flow rate of the hydraulic pump 23 from the product of the rotational speed of the engine 22 and the capacity of the hydraulic pump 23.

  In this case, the discharge flow rate of the hydraulic pump 23 determines the expansion / contraction speed (extension speed, reduction speed) of the boom cylinders 15 and 16. That is, as the discharge flow rate of the hydraulic pump 23 increases, the boom cylinders 15 and 16 expand and contract faster. As the discharge flow rate of the hydraulic pump decreases, the boom cylinder extends and contracts slower. As will be described later, the controller 45 calculates a discharge flow rate (final flow rate Q3, which will be described later) to be discharged from the hydraulic pump 23 and divides the discharge flow rate by the number of revolutions of the engine 22 to thereby obtain a hydraulic pump. 23 target capacities are calculated.

  The pressure sensor 35 detects an operation amount of the operation lever 8A for operating the boom cylinders 15 and 16, that is, an operation amount (switching signal amount) of the boom direction control valve 25. Constitutes an operation amount detecting means according to the present invention. More specifically, the pressure sensor 35 detects the boom raising operation amount, that is, the degree (degree) of the operation for rotating the boom 12 upward in the anti-self-weight direction. For this purpose, the pressure sensor 35 is provided in one pilot pipeline 31 that supplies a pilot pressure (switching signal) to one hydraulic pilot section 25A for switching the boom direction control valve 25 to the switching position (A). ing.

  The pressure sensor 35 detects the pilot pressure of one pilot pipe line 31 as a boom raising operation amount C1. The pressure sensor 35 is connected to the controller 45 via the signal line 36, and the pressure sensor 35 outputs a detection signal corresponding to the detected pilot pressure (boom raising operation amount) to the controller 45. As will be described later, the controller 45 determines whether or not the boom cylinders 15 and 16 are operated based on the boom raising operation amount (pilot pressure) C1 (step 3 in FIG. 3 described later), and the hydraulic pump. 23 target reference flow rate Q1 is calculated (step 4 in FIG. 3).

  The bottom side pressure sensor 37 is provided in the bottom side pipe line 29, and the bottom side pressure sensor 37 constitutes a pressure detection means according to the present invention. The rod-side pressure sensor 38 is provided in the rod-side pipe line 30, and the rod-side pressure sensor 38 constitutes a pressure detection means according to the present invention. The bottom side pressure sensor 37 detects the pressure of the bottom side oil chambers 15C and 16C of the boom cylinders 15 and 16, that is, the bottom side pressure, by detecting the pressure of the bottom side pipe line 29. Since the bottom side pressure may be referred to as a head side pressure, the bottom side pressure sensor can also be referred to as a head side pressure sensor, but the following description will be described as a bottom side pressure sensor. On the other hand, the rod side pressure sensor 38 detects the pressure in the rod side oil chambers 15D and 16D of the boom cylinders 15 and 16, that is, the rod side pressure, by detecting the pressure in the rod side pipe line 30.

  The bottom side pressure sensor 37 is connected to the controller 45 via the signal line 39, and the bottom side pressure sensor 37 outputs a detection signal corresponding to the detected bottom side pressure (bottom side pressure) to the controller 45. The rod side pressure sensor 38 is connected to the controller 45 via the signal line 40, and the rod side pressure sensor 38 outputs a detection signal corresponding to the detected rod side pressure (rod side pressure) to the controller 45. As will be described later, the controller 45 calculates the thrust F of the boom cylinders 15 and 16 based on the bottom side pressure and the rod side pressure (step 8 in FIG. 3), and the fluctuation speed of the thrust F of the boom cylinders 15 and 16. V is calculated (step 9 in FIG. 3).

  The pressure sensors 41 and 42 indicate the amount of operation of the work operation lever 8A for operating hydraulic actuators other than the boom cylinders 15 and 16 (for example, the arm cylinder 17, the bucket cylinder 18 and a turning hydraulic motor not shown). The pressure sensors 41 and 42 are an example of an operation amount detection sensor that detects an operation amount of the work operation lever 8A. That is, the pressure sensors 41 and 42 are directional control valves that control the supply and discharge of pressure oil to the hydraulic actuators other than the boom cylinders 15 and 16 (for example, a directional control valve for an arm, a directional control valve for a bucket, not shown) The amount of operation of a directional control valve or the like) is detected.

  Similarly to the pressure sensor 35, these pressure sensors 41 and 42 are connected to the controller 45 via signal lines 43 and 44, and the pressure sensors 41 and 42 correspond to the detected operation amount (for example, pilot pressure). A detection signal is output to the controller 45. As will be described later, the controller 45 determines whether a hydraulic actuator other than the boom cylinders 15 and 16 is operated based on the operation amount (pilot pressure) C2 (step 6 in FIG. 3).

  In FIG. 2, in order to avoid complication of the drawing, the direction control valve other than the boom direction control valve 25 and the work operation levers 8A and 8B and operation means for operating the direction control valve (for example, the traveling direction control valve and the same) The illustration of a travel lever, pedal, etc. for operating is omitted. However, the controller 45 detects an operation amount that detects an operation amount of an operating means (not shown) such as a travel lever / pedal so that it can be determined whether a hydraulic actuator other than the boom cylinders 15 and 16 has been operated. Means (for example, an operation amount detection sensor for detecting an operation amount of the traveling direction control valve) are also connected.

  The controller 45 controls the capacity of the hydraulic pump 23, more specifically, adjusts the capacity of the hydraulic pump 23 by controlling the capacity variable mechanism 23B of the hydraulic pump 23. The controller 45 includes, for example, a microcomputer and the input side thereof is connected to the rotation sensor 33, the pressure sensors 35, 37, 38, 41, 42, and the like. The output side of the controller 45 is connected to the variable capacity mechanism 23 </ b> B of the hydraulic pump 23. The controller 45 has a storage unit (not shown) composed of a ROM, a RAM, and the like. The storage unit includes a capacity control processing program shown in FIG. 3 to be described later, and a boom raising operation amount shown in FIG. 4 to be described later. A table, a map, and the like for determining the target reference flow rate Q1 according to C1 are stored (stored).

  Here, the controller 45 includes a target reference flow rate calculating means (step 4 in FIG. 3), a thrust fluctuation speed calculating means (step 9 in FIG. 3), and a target capacity calculating means (steps 10, 11, 12, 13). The target reference flow rate calculation means corresponding to step 4 in FIG. 3 detects the detected value of the pressure sensor 35 for detecting the operation amount of one of the operation levers 8A (the operation amount of the boom direction control valve 25), that is, raising the boom. The target reference flow rate Q1 of the hydraulic pump 23 is calculated according to the operation amount C1. In this case, the target reference flow rate Q1 can be calculated based on, for example, the relationship between the boom raising operation amount C1 and the target reference flow rate Q1 shown in FIG.

  The thrust fluctuation speed calculating means corresponding to step 9 in FIG. 3 includes a bottom side pressure sensor 37 for detecting the bottom side pressure (bottom side pressure) of the boom cylinders 15 and 16 and a rod side pressure for detecting the rod side pressure (rod side pressure). Based on the detection value of the sensor 38, the fluctuation speed V of the thrust F of the boom cylinders 15 and 16 is calculated. Here, the thrust F of the boom cylinders 15 and 16 is expressed by the following formula 1 when Ab is the pressure receiving area on the bottom side, Ar is the pressure receiving area on the rod side, and the direction in which the rods 15E and 16E extend is positive. Can be calculated.

  In this case, Ab and Ar can be set in advance as known values. The fluctuation speed V of the thrust F of the boom cylinders 15 and 16 can be calculated by, for example, time differentiation of the thrust F. In this case, the fluctuation speed V is set in advance so that the direction in which the thrust F decreases is negative (sign). When the rod side pressure can be ignored, the thrust F can be the bottom side pressure, and the fluctuation speed V of the thrust F in this case can be the bottom side pressure fluctuation speed.

  When the fluctuation speed V of the thrust F is negative, the target capacity calculation means corresponding to steps 10, 11, 12, and 13 in FIG. 3 calculates the correction flow Q2 proportional to the fluctuation speed V, and the correction flow Q2 The target capacity of the hydraulic pump 23 is calculated based on the target reference flow rate Q1 calculated by the target reference flow rate calculation means and the detected value of the rotation sensor 33 (the rotation speed of the engine 22). In this case, the target capacity calculation means is more specific based on the final flow rate Q3 that is the total flow rate obtained by adding the target reference flow rate Q1 and the correction flow rate Q2, and the rotation speed of the engine 22 detected by the rotation sensor 33. The target capacity of the hydraulic pump 23 is calculated by dividing the final flow rate Q3 by the rotation speed. The controller 45 controls the variable capacity mechanism 23B of the hydraulic pump 23 so that the target capacity is calculated by the target capacity calculating means.

  Here, the correction flow rate Q2 is for supplementing the thrust F of the boom cylinders 15 and 16 with respect to the target reference flow rate Q1 (complementing the insufficient thrust F). When the fluctuation speed V of the thrust F of the boom cylinders 15 and 16 is negative, the capacity (target capacity) of the hydraulic pump 23 is obtained by adding the correction flow rate Q2 to the target reference flow rate Q1. Thereby, it is possible to suppress (attenuate) vibration of the bottom side pressure when the boom cylinders 15 and 16 suddenly operate. The processing for controlling the capacity of the hydraulic pump 23 performed by the controller 45 will be described in detail later.

  The hydraulic excavator 1 according to the first embodiment has the above-described configuration. Next, the operation thereof will be described.

  First, an operator can board the cab 5 and operate the left and right traveling levers / pedals (not shown) to move the lower traveling body 2 forward or backward. On the other hand, the operator in the cab 5 can perform the excavation work of earth and sand, etc. by operating the left and right operation levers 8A and 8B to rotate (elevate) the working device 11.

  In this case, for example, when an abrupt boom raising operation (an operation of rotating the boom 12 upward) is performed from a state in which a part of the work device 11 is grounded, a characteristic line 51 indicated by a two-dot chain line in FIG. Further, the pressure of the hydraulic oil in the bottom side oil chambers 15C, 16C of the boom cylinders 15, 16 becomes vibrational. Therefore, in the first embodiment, when the fluctuation speed V of the thrust F of the boom cylinders 15 and 16 is negative, the controller 45 takes into account the correction flow rate Q2 for supplementing the thrust F of the boom cylinders 15 and 16. Thus, the capacity of the hydraulic pump 23 is controlled. The control process of the hydraulic pump 23 performed by the controller 45 will be described with reference to FIG. Note that the process of FIG. 3 is repeatedly executed at a predetermined control period while the controller 45 is energized, for example.

  When the processing operation of FIG. 3 is started by starting the engine 22 or the like, in step 1, the rotation speed of the engine 22 (= engine rotation speed) is detected by the rotation sensor 33. In the subsequent step 2, the boom raising operation amount C1 is detected. The boom raising operation amount C1 is detected by, for example, an operation amount (switching signal amount) of the boom direction control valve 25, more specifically, a pilot for switching the boom direction control valve 25 to the switching position (A). This can be performed by detecting the pressure (switching signal) with the pressure sensor 35.

  In the subsequent step 3, it is determined whether or not the boom raising operation amount C1 is ON, that is, whether the boom raising operation amount C1 is greater than zero (C1> 0). If “NO”, that is, if the boom raising operation amount C1 is determined to be zero (C1 = 0) in step 3, it can be determined that the boom raising operation is not performed. In this case, the process returns to the start via the return, and the processes after step 1 are repeated.

  On the other hand, if “YES”, that is, if the boom raising operation amount C1 is determined to be larger than zero (C1> 0) in step 3, it can be determined that the boom raising operation is being performed. In this case, the process proceeds to step 4, and the target reference flow rate Q1 is calculated from the boom raising operation amount C1. Specifically, referring to a preset table (map) shown in FIG. 4, that is, the relationship between the boom raising operation amount C1 and the target reference flow rate Q1, the target reference flow rate is determined based on the boom raising operation amount C1 at that time. Q1 can be obtained (calculated).

  In step 5 following step 4, the operation amount C2 of a hydraulic actuator other than the boom cylinders 15 and 16 (for example, an arm cylinder 17, a bucket cylinder 18, a turning hydraulic motor not shown) is detected. The operation amount C2 of the hydraulic actuators other than the boom cylinders 15 and 16 is, for example, the operation amounts of the pressure sensors 41 and 42 for detecting the operation amount of the work operation lever 8A, and other travel levers and pedals (not shown). It can be detected by a detected operation amount detection sensor or the like.

  In subsequent step 6, it is determined whether or not the operation amount C2 of the hydraulic actuators other than the boom cylinders 15 and 16 is OFF, for example, whether or not the operation amount C2 is zero (C2 = 0). If it is determined in step 6 that “NO”, that is, the operation amount C2 is ON (for example, C2> 0), it can be determined that the hydraulic actuators other than the boom cylinders 15 and 16 are being operated. . In this case, the process returns to the start via the return, and the processes after step 1 are repeated.

  On the other hand, if it is determined in step 6 that “YES”, that is, the operation amount C2 is OFF (for example, C2 = 0), the hydraulic actuators other than the boom cylinders 15 and 16 are not operated. Can be judged. In this case, the process proceeds to step 7 and the bottom side pressure and the rod side pressure of the boom cylinders 15 and 16 are detected. This detection can be performed by the bottom side pressure sensor 37 and the rod side pressure sensor 38.

  In step 8 following step 7, the thrust F of the boom cylinders 15 and 16 is calculated based on the bottom side pressure and the rod side pressure of the boom cylinders 15 and 16. The thrust F can be calculated by the above equation (1). In addition, when the rod side pressure can be ignored, the thrust F can be set to the bottom side pressure.

  After calculating the thrust F in step 8, in step 9, the fluctuation speed V (= thrust fluctuation speed V) of the thrust F of the boom cylinders 15 and 16 is calculated. The thrust fluctuation speed V can be calculated by differentiating the thrust F with respect to time. In this case, the thrust fluctuation speed V is previously set to be positive or negative (sign) so that the direction in which the thrust F decreases is negative. When the rod side pressure can be ignored, the thrust fluctuation speed V can be set as the bottom side pressure fluctuation speed.

  After calculating the thrust fluctuation speed V in step 9, it is determined in step 10 whether the thrust fluctuation speed V is negative (V <0). If “YES” in step 10, that is, if it is determined that the thrust fluctuation speed V is negative (V <0), the process proceeds to step 11 to calculate the correction flow rate Q2. Thus, in the first embodiment, the discharge flow rate of the hydraulic pump 23 is corrected only when the thrust F decreases, that is, when the thrust fluctuation speed V becomes negative. When it is determined “YES”, the process proceeds to calculation (calculation) of the correction flow rate Q2 with respect to the target reference flow rate Q1.

  The correction flow rate Q2 can be calculated by a calculation formula in which a predetermined amount of gain i is multiplied by the thrust fluctuation speed V. Since the thrust fluctuation speed V at this time is negative, it is necessary to multiply by a minus sign. That is, the correction flow rate Q2 can be calculated from the following equation (2).

  After the correction flow rate Q2 is calculated in step 11, a final flow rate Q3 that is a flow rate to be discharged by the hydraulic pump 23 (target discharge flow rate) is calculated in the following step 12. The final flow rate Q3 can be calculated by adding the corrected flow rate Q2 calculated in step 11 to the target reference flow rate Q1 obtained in step 4. That is, the final flow rate Q3 can be calculated by the following equation (3).

  After the final flow rate Q3 is calculated in step 12, the target capacity of the hydraulic pump 23 is calculated in the following step 13. The target capacity of the hydraulic pump 23 can be calculated by dividing the final flow rate Q3 by the engine speed detected in step 1. The controller 45 controls the variable capacity mechanism 23B of the hydraulic pump 23 so that the target capacity calculated in step 13 is obtained. Then, the process returns to the start via the return, and the processes after step 1 are repeated.

  On the other hand, if it is determined as “NO” in step 10, that is, if the thrust fluctuation speed V is not negative (V ≧ 0), the process returns to the start via a return, and the processing from step 1 is repeated. That is, in this case, the capacity of the hydraulic pump 23 is not corrected. For example, the controller 45 calculates the capacity of the hydraulic pump 23 based on the target reference flow rate Q1 (and the rotational speed of the engine 22). The capacity variable mechanism 23B of the hydraulic pump 23 is controlled so as to achieve the capacity. This is because, for example, when the thrust fluctuation speed V is positive, correction is performed to reduce the thrust F of the boom cylinders 15 and 16 in order to suppress the pressure vibration of the boom cylinders 15 and 16, that is, thrust. This is because if the displacement of the hydraulic pump 23 is controlled in consideration of the correction flow rate for reducing F, the boom 12 may not rotate or the initial speed of the boom 12 may be delayed.

  Thus, according to the first embodiment, it is possible to suppress the vibration of the bottom side pressure accompanying the sudden operation of the boom cylinders 15 and 16 and to secure the initial speed (initial speed) of the boom 12 of the work device 11. And the operability of the working device 11 (boom 12) can be improved. In particular, when the boom 12 is raised from the state where a part of the work device 11 is grounded (the holding pressure is zero) (the boom 12 is turned upward in the anti-self-weight direction), the boom 12 is moved. It is possible to achieve both the suppression of the vibration and the securing of the initial rotation speed at a high level.

  That is, the controller 45 that controls the variable displacement mechanism 23B of the hydraulic pump 23 performs the processing in steps 11, 12, and 13 when the thrust fluctuation speed V of the boom cylinders 15 and 16 is determined to be negative by the processing in step 10. Thus, the target capacity of the hydraulic pump 23 is calculated using not only the target reference flow rate Q1, but also the correction flow rate Q2 proportional to the thrust fluctuation speed V of the boom cylinders 15 and 16. Thereby, when the thrust fluctuation speed V of the boom cylinders 15 and 16 is negative, the control of the capacity of the hydraulic pump 23 compensates the thrust F of the boom cylinders 15 and 16 with respect to the target reference flow rate Q1 (insufficient thrust F The correction flow rate Q2 can be taken into account.

  That is, as shown in FIG. 5, during the raising operation of the boom 12, only when the thrust fluctuation speed V becomes negative (= dF / dt <0), the correction flow rate Q2 is added to the target reference flow rate Q1. Insufficient thrust F of the boom cylinders 15 and 16 can be compensated. As a result, as shown by a solid characteristic line 52 in FIG. 5, it is possible to suppress (attenuate) vibration of the bottom side pressure when the boom cylinders 15 and 16 suddenly operate. That is, the bottom side pressure can be converged to the holding pressure more quickly than the configuration in which the flow rate is not corrected.

  Moreover, the correction flow rate Q2 for suppressing the vibration of the bottom side pressure is taken into consideration when the thrust fluctuation speed V of the boom cylinders 15 and 16 is negative (V <0), but the thrust fluctuation speed V is positive (fluctuation speed). > 0) is not taken into account. That is, the correction flow rate for reducing the thrust F of the boom cylinders 15 and 16 is not added to the control of the capacity of the hydraulic pump 23 (the correction flow rate becomes 0). In short, when the thrust fluctuation speed V is positive (fluctuation speed> 0), there is no effect of reducing the discharge flow rate of the hydraulic pump, so that a bottom side pressure equal to or higher than the holding pressure should be secured immediately after the boom raising operation is started. Can do. Thereby, it can suppress that the thrust F of the boom cylinders 15 and 16 falls in the operation | movement initial stage of the boom 12 of the working apparatus 11, and can ensure the initial speed (rotation initial speed) of the working apparatus 11 (boom 12). Can do. For example, compared with a configuration in which the capacity of the hydraulic pump is controlled by taking into account the correction flow rate according to the deviation between the bottom side pressure and the holding pressure applied by the working device's own weight, etc. (feedback by the deviation between the holding thrust and the current thrust). The initial speed of the working device 11 can be improved.

  According to the first embodiment, the target capacity of the hydraulic pump 23 is calculated using the total flow rate (final flow rate Q3) obtained by adding the target reference flow rate Q1 and the correction flow rate Q2. Thereby, the suppression of the vibration of the boom cylinders 15 and 16 and the securing of the initial speed of the work device 11 (the boom 12) can be achieved with a hydraulic system (hydraulic circuit 21) constituted by one hydraulic pump 23.

  According to the first embodiment, when the thrust fluctuation speed V of the boom cylinders 15 and 16 is determined to be negative in step 10, the corrected flow rate Q2 is calculated in step 11. Thereby, the processing of the controller 45 can be reduced as compared with a configuration in which the correction flow rate Q2 is always calculated, for example, a configuration in which step 11 (or step 13) is provided before step 10.

  In the first embodiment, a specific example of the target reference flow rate calculation means in which the processing in step 4 in FIG. 3 is a constituent requirement of the present invention is shown, and the processing in step 9 in FIG. 3 is a constituent requirement in the present invention. A specific example of a certain thrust fluctuation speed calculation means is shown, and a specific example of the target capacity calculation means in which the processing of step 10 to step 13 in FIG. 3 is a component of the present invention is shown.

  Next, FIG. 6 and FIG. 7 show a second embodiment of the present invention. The feature of the second embodiment resides in that the hydraulic cylinder (boom cylinder) is driven (expanded and reduced) by two hydraulic pumps and two directional control valves (boom directional control valves). That is, while the first embodiment described above is configured to include one hydraulic pump and one directional control valve (boom directional control valve), in the second embodiment, 2 The configuration includes two hydraulic pumps and two directional control valves (boom directional control valves). In the second embodiment, the same components as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 6, the second hydraulic pump 61 is provided in the hydraulic circuit 21 in addition to the hydraulic pump 23 as the first hydraulic pump. The second hydraulic pump 61 pressurizes the hydraulic oil (oil) in the hydraulic oil tank 24 and discharges it toward the second boom direction control valve 62. 6 also omits the direction control valves other than the boom direction control valve 25, as in FIG.

  Similar to the hydraulic pump 23, the second hydraulic pump 61 is configured as a swash plate type, radial piston type, or oblique axis type variable displacement hydraulic pump, and includes a displacement variable portion 61A and a displacement variable mechanism 61B. Yes. The capacity variable mechanism 61B drives (tilts and drives) the capacity variable unit 61A based on a command from the controller 70 described later. In the second embodiment, a boom raising operation is actively performed by the hydraulic pump 23, and pressure oil is supplied to the bottom side oil chambers 15C and 16C of the boom cylinders 15 and 16 at a small flow rate or a minimum flow rate by the second hydraulic pump 61. Is configured to supply. In this case, the target reference flow rate Q1 is controlled by the hydraulic pump 23, and the correction flow rate Q2 is controlled by the second hydraulic pump 61 (the control of the target reference flow rate Q1 and the correction flow rate Q2 is performed in parallel).

  The second boom directional control valve 62 is provided in the hydraulic circuit 21 in addition to the boom directional control valve 25 as the first directional control valve. This constitutes the second direction control valve of the present invention. The second boom direction control valve 62 is provided between the second hydraulic pump 61 and the boom cylinders 15 and 16. Similar to the boom direction control valve 25, the second boom direction control valve 62 controls the supply and discharge of pressure oil to and from the boom cylinders 15 and 16, and is, for example, a 6-port 3-position hydraulic pilot type direction control. It consists of a valve. The second boom direction control valve 62 is connected to the second hydraulic pump 61 via the discharge pipe 63, and is connected to the hydraulic oil tank 24 via the center bypass pipe 64 and the return pipe 65. .

  Further, the second boom direction control valve 62 is connected to the bottom side pipe line 29 via the bottom side connection pipe line 66. Further, the second boom direction control valve 62 is connected to the rod side pipe line 30 via a rod side connection pipe line 67.

  Similarly to the boom direction control valve 25, the second boom direction control valve 62 is also operated (switching operation) by a work operation lever 8A as an operation means. For this purpose, a pair of hydraulic pilot portions 62A and 62B are provided on both ends of the second boom direction control valve 62. The hydraulic pilot parts 62A and 62B are connected to the pilot pipe lines 31 and 32 via the pilot connection pipe lines 68 and 69, respectively, and are supplied with pilot pressure (switching signal) based on the operation of the work operation lever 8A. .

  The controller 70 controls the capacity of the hydraulic pump 23 and the second hydraulic pump 61. More specifically, the controller 70 controls the capacity variable mechanism 23B of the hydraulic pump 23 and the capacity variable mechanism 61B of the second hydraulic pump 61. Thus, the capacities of the hydraulic pump 23 and the second hydraulic pump 61 are adjusted. Similarly to the controller 45 of the first embodiment, the controller 70 includes a microcomputer, for example, and its input side is connected to the rotation sensor 33, the pressure sensors 35, 37, 38, 41, 42, and the like. Has been. On the other hand, the output side of the controller 70 is connected to the capacity variable mechanism 61B of the second hydraulic pump 61 in addition to the capacity variable mechanism 23B of the hydraulic pump 23.

  Similarly to the controller 45 of the first embodiment, the controller 70 is a target reference flow rate calculation means (step 24 in FIG. 7) for calculating the target reference flow rate Q1, and the fluctuation speed V of the thrust F of the boom cylinders 15 and 16. (= Thrust fluctuation speed calculation means (step 30 in FIG. 7) for calculating the thrust fluctuation speed V) and target capacity calculation means (step 25 in FIG. 7) for calculating the target capacity of the hydraulic pump 23 and the second hydraulic pump 61. , 31, 32, 33). In this case, the target capacity calculating means is a first target capacity calculating means for calculating the target capacity of the hydraulic pump 23 based on the target reference flow rate Q1 and the detected value of the rotation sensor 33 (the rotational speed of the engine 22). (Step 25 in FIG. 7), the target flow rate of the second hydraulic pump 61 is calculated based on the corrected flow rate Q2 proportional to the thrust fluctuation speed V and the rotational speed of the engine 22 detected by the rotation sensor 33. Second target capacity calculating means (steps 31, 32, and 33 in FIG. 7). The controller 70 controls the variable capacity mechanism 23B of the hydraulic pump 23 so as to be the target capacity calculated by the first target capacity calculating means so as to be the target capacity calculated by the second target capacity calculating means. Next, the variable capacity mechanism 61B of the second hydraulic pump 61 is controlled.

  Control processing of the hydraulic pump 23 and the second hydraulic pump 61 performed by the controller 70 will be described with reference to FIG. The processing from step 21 to step 23 in FIG. 7 is the same as the processing from step 1 to step 3 in FIG.

  If “YES” in step 23, that is, if it is determined that the boom raising operation amount C 1 is greater than zero (C 1> 0), the process proceeds to step 24 and step 26. In step 24, similarly to step 4 in FIG. 3, the target reference flow rate Q1 is obtained from the boom raising operation amount C1 using, for example, the table (map) in FIG. In step 25 following step 24, the target capacity of the hydraulic pump 23 is calculated. In this case, the target capacity of the hydraulic pump 23 can be calculated, for example, by dividing the target reference flow rate Q1 by the engine speed detected in step 21. The controller 70 controls the variable capacity mechanism 23B of the hydraulic pump 23 so that the target capacity calculated in step 25 is obtained. Then, the process returns to the start via the return, and the processes after step 21 are repeated.

  On the other hand, in step 26, as in step 5 of FIG. 3, the operation amount C2 of the hydraulic actuators other than the boom cylinders 15 and 16 is detected. The processing from step 26 to step 32 is the same as the processing from step 5 to step 11 in FIG. When the correction flow rate Q2 is calculated in step 32, the target capacity of the second hydraulic pump 61 is calculated in step 33. In this case, the target capacity of the second hydraulic pump 61 can be calculated, for example, by dividing the corrected flow rate Q2 by the engine speed detected in step 21. The controller 70 controls the variable capacity mechanism 61B of the second hydraulic pump 61 so that the target capacity calculated in step 33 is obtained. Then, the process returns to the start via the return, and the processes after step 21 are repeated.

  In the second embodiment, the controller 70 controls the capacity of the hydraulic pump 23 and the second hydraulic pump 61 as described above. The basic operation of the second embodiment is the same as that of the first embodiment. There is no particular difference.

  Particularly, in the second embodiment, the capacity of the hydraulic pump 23 can be set according to the target reference flow rate Q1, and the capacity of the second hydraulic pump 61 can be set according to the correction flow rate Q2. Thereby, the suppression of the vibration of the boom cylinders 15 and 16 and the securing of the initial speed of the work device 11 (the boom 12) can be achieved by a hydraulic system (hydraulic circuit 21) configured by the two hydraulic pumps 23 and 61.

  In the second embodiment, a specific example of the target reference flow rate calculation means in which the processing in step 24 of FIG. 7 is a constituent requirement of the present invention is shown, and the processing of step 30 in FIG. 7 is a constituent requirement of the present invention. A specific example of a certain thrust fluctuation speed calculating means is shown, and a specific example of the target capacity calculating means in which the processing of steps 25, 31, 32, and 33 in FIG. 7 is a constituent requirement of the present invention is shown. In this case, a specific example of the first target capacity calculating means in which the process in step 25 in FIG. 7 is a constituent requirement of the present invention is shown, and the processes in steps 31, 32, and 33 in FIG. The specific example of a certain 2nd target capacity | capacitance calculation means is shown.

  Next, FIGS. 8 to 11 show a third embodiment of the present invention. A feature of the third embodiment is that the correction flow rate is adjusted based on the stroke amount of the hydraulic cylinder. In the third embodiment, the same components as those in the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted.

  In FIG. 8, a stroke sensor 71 detects the stroke amount of the boom cylinder 15, and the stroke sensor 71 constitutes a stroke detection means according to the present invention. The stroke sensor 71 is connected to a controller 73 described later via a signal line 72, and the stroke sensor 71 outputs a detection signal corresponding to the detected stroke amount of the boom cylinder 15 to the controller 73. For example, the controller 73 adjusts the correction flow rate Q2 based on the stroke amount of the boom cylinder 15 (= the stroke amount of the boom cylinder 16).

  Since the stroke amounts of the left and right boom cylinders 15 and 16 correspond to each other, the stroke amount of one boom cylinder 15 is detected in FIG. Although illustration is omitted, a configuration may be adopted in which the stroke amounts of both the left and right boom cylinders 15 and 16 are detected.

  The controller 73 controls the capacity of the hydraulic pump 23 (controls the capacity variable mechanism 23B). The controller 73 includes a microcomputer, for example, as with the controller 45 of the first embodiment. The input side of the controller 73 is connected to the stroke sensor 71 in addition to the rotation sensor 33 and the pressure sensors 35, 37, 38, 41 and 42. On the other hand, the output side of the controller 70 is connected to the displacement variable mechanism 23 </ b> B of the hydraulic pump 23.

  Similarly to the controller 45 of the first embodiment, the controller 73 is a target reference flow rate calculation means (step 44 in FIG. 9) for calculating the target reference flow rate Q1, and the fluctuation speed V of the thrust F of the boom cylinders 15 and 16. (= Thrust fluctuation speed calculation means V) (step 49 in FIG. 9) and target capacity calculation means (steps 50 to 56 in FIG. 9) to calculate the target capacity of the hydraulic pump 23. ing. In this case, the target capacity calculation means is configured to adjust the correction flow rate Q2 based on the stroke amount x of the boom cylinder 15 (16) (steps 51 to 54 in FIG. 9).

  More specifically, the target capacity calculation means calculates the volume of hydraulic oil from the hydraulic pump 23 to the bottom side oil chambers 15C, 16C of the boom cylinders 15, 16 based on the detection value of the stroke sensor 71 (FIG. 9 step 52). In addition to this, the target capacity calculation means adjusts the correction flow rate Q2 based on the stroke amount x of the boom cylinder 15 (16) corresponding to the volume (having a correlation) (step 54 in FIG. 9).

  That is, in the third embodiment, the gain i in the first embodiment is set to the stroke amount x corresponding to the volume of oil (operating oil) between the hydraulic pump 23 and the bottom side oil chambers 15C and 16C. ). Here, the relationship between the hydraulic oil volume between the hydraulic pump 23 and the bottom oil chambers 15C and 16C, the discharge flow rate of the hydraulic pump 23, the thrust of the boom cylinders 15 and 16, and the like will be described with reference to FIG.

  FIG. 10 shows the stroke amount x (n) of the boom cylinder 15 (16) at the time t = n, the expansion / contraction speed (displacement speed) vx (n) of the boom cylinder 15 (16), and the boom cylinder 15 (16). The thrust F (n) is shown. Here, the relationship between the thrust F (n) of the boom cylinder 15 (16) at time t = n and the thrust F (n−Δt) at time t = n−Δt can be expressed as the following equation (4). In this case, the bottom pressure receiving area of the boom cylinder 15 (16) is Ab, and the bottom pressure at the time t = n is Pb (n). Further, it is assumed that the rod side pressure is zero and Δt is very small.

  Here, “dPb (n) / dt × Δt” approximately represents the bottom side pressure that fluctuated between time t = n−Δt and t = n. In this case, the volume elastic modulus of the hydraulic oil is K, the volume of the hydraulic oil between the hydraulic pump 23 and the bottom side oil chamber 15C (16C) in the most contracted state of the boom cylinder 15 (16) is V0, and time t Assuming that the discharge flow rate of the hydraulic pump 23 at = n is Qp (n), “dPb (n) / dt” can be obtained by the following equation (5).

  “V0 + x (n) × Ab” in Formula 5 indicates the volume between the hydraulic pump 23 and the bottom side oil chamber 15C (16C) at time t = n, and “Qp (n) −Ab × vx (n ")" Shows the difference between the discharge flow rate of the hydraulic pump 23 and the inflow flow rate of the bottom oil chamber 15C (16C).

  Then, “dPb (n) / dt” is eliminated by Equation 4 and Equation 5, and the thrust fluctuation speed “{F (n) −F (n) between time t = n−Δt and t = n” is eliminated. -Δt)} / Δt ”, the following formula 6 is obtained.

  From equation (6), it can be seen that the larger the “V0 + x (n) × Ab”, that is, the greater the stroke amount x (n) of the boom cylinder 15 (16), the smaller the thrust fluctuation speed V. This is because, when the thrust F of the boom cylinder 15 (16) vibrates due to the influence from outside the hydraulic circuit, for example, the influence of the vehicle body inertia or the like, the greater the stroke amount x (n), the lower the vibration suppressing effect. Means.

  Therefore, in the third embodiment, “V0 + x (n) × Ab”, that is, the corrected flow rate in consideration of the volume of oil (hydraulic oil) between the hydraulic pump 23 and the bottom side oil chambers 15C, 16C. Adjust (correct) Q2. In this case, the correction flow rate Q2 is adjusted by newly multiplying the correction flow rate Q2 by the correction coefficient iv. Specifically, the corrected flow rate Q2 is calculated by the following equation (7).

  Next, control processing of the hydraulic pump 23 performed by the controller 73 will be described with reference to FIG. The processing from step 41 to step 50 in FIG. 9 is the same as the processing from step 1 to step 10 in FIG.

  If “YES” in step 50, that is, if it is determined that the thrust fluctuation speed V is negative (V <0), the process proceeds to step 51, where the stroke amount x of the boom cylinder 15 (16) is detected by the stroke sensor 71. Is detected. In step 52, the volume of hydraulic oil from the hydraulic pump 23 to the bottom side oil chambers 15C, 16C of the boom cylinders 15, 16 is calculated based on the detection value of the stroke sensor 71. Specifically, the stroke amount x detected by the stroke sensor 71, the volume V0 of hydraulic fluid between the hydraulic pump 23 and the bottom side oil chamber 15C (16C) in the most contracted state, and the bottom side pressure receiving area are expressed as Ab. Based on the above, the volume of hydraulic oil from the current hydraulic pump 23 to the bottom side oil chambers 15C and 16C of the boom cylinders 15 and 16, that is, “V0 + x × Ab” is calculated.

  In the following step 53, a correction coefficient iv for adjusting the correction flow rate Q2 is calculated based on the volume of hydraulic oil calculated in step 52 (more specifically, the stroke amount x corresponding to the volume). Specifically, referring to the table (map) shown in FIG. 11 set in advance, that is, the relationship between the stroke amount x of the boom cylinder 15 (16) and the correction coefficient iv, the volume “V0 + x × Ab” at that time is set. A correction coefficient iv is obtained (calculated) based on the corresponding stroke amount x.

  In this case, for example, when the gain i for calculating the correction flow rate Q2 in the next step 54 is determined in the most contracted state of the boom cylinder 15 (16), the correction coefficient iv of the gain i is “(V0 + xx). Ab) / V0 ". Then, as shown in FIG. 11, by creating a map in which the horizontal axis is the stroke amount x and the vertical axis is the correction coefficient iv, that is, “(V0 + x × Ab) / V0”, the stroke amount x is obtained. Based on this, the correction coefficient iv can be obtained. Note that when the correction coefficient iv is obtained from the relationship between the stroke amount x and the correction coefficient iv, the calculation of the volume may be omitted (step 52 may be omitted).

  In step 54 following step 53, the correction flow rate Q2 is calculated. The calculation (calculation) of the correction flow rate Q2 can be calculated from the above-described equation (7). In this case, the correction flow rate Q2 is adjusted by the correction coefficient iv. As a result, the correction flow rate Q2 takes into account the effect of suppressing the vibration corresponding to the volume “V0 + x × Ab” of the hydraulic oil from the hydraulic pump 23 to the bottom side oil chambers 15C, 16C of the boom cylinders 15, 16. be able to.

  After the correction flow rate Q2 is calculated in step 54, in the subsequent step 55, the final flow rate Q3 that is the flow rate (target discharge flow rate) to be discharged by the hydraulic pump 12 is calculated, as in step 12 of FIG. When the final flow rate Q3 is calculated in step 55, in the subsequent step 56, the target capacity of the hydraulic pump 23 is calculated as in step 13 of FIG. The controller 73 controls the variable capacity mechanism 23B of the hydraulic pump 23 so that the target capacity calculated in step 56 is obtained. Then, the process returns to the start via the return, and the processing after step 41 is repeated.

  In the third embodiment, the capacity of the hydraulic pump 23 is controlled by the controller 73 as described above, and the basic operation is not different from that in the first embodiment described above.

  In particular, the third embodiment corrects based on the stroke amount x of the boom cylinder 15 (16) corresponding to the oil volume from the hydraulic pump 23 to the bottom side oil chambers 15C, 16C of the boom cylinders 15, 16. Since the flow rate Q2 is adjusted, the capacity of the hydraulic pump 23 can be controlled in consideration of a decrease in thrust response based on the compressibility of the hydraulic oil. Thus, regardless of the stroke amount x of the boom cylinder 15 (16) (whether the stroke amount x is small or large), the vibration of the boom cylinders 15 and 16 is suppressed and the initial speed of the working device 11 (boom 12) is secured. Can be achieved at a high level.

  In the third embodiment, when the thrust fluctuation speed V of the boom cylinders 15 and 16 is determined to be negative in step 50, the correction coefficient iv is obtained in steps 51 to 53. Thereby, compared with the structure which calculates the correction coefficient iv always, for example, the structure which provides steps 51-53 before step 50, reduction of the process of the controller 73 can be achieved.

  In the third embodiment, a specific example of the target reference flow rate calculation means in which the processing in step 44 in FIG. 9 is a constituent requirement of the present invention is shown, and the processing in step 49 in FIG. 9 is a constituent requirement in the present invention. A specific example of a certain thrust fluctuation speed calculation means is shown, and the processing of steps 50 to 56 in FIG. 9 shows a specific example of the target capacity calculation means, which is a constituent requirement of the present invention.

  In the third embodiment, as shown in FIG. 11, the case where the relationship between the stroke amount x and the correction coefficient iv is a proportional relationship (linear) has been described as an example. However, the present invention is not limited to this. For example, as in the modification shown in FIG. 12, the relationship between the stroke amount x and the correction coefficient iv is a curve (nonlinear) like the characteristic line A, and the boom cylinders 15, 16 are used. The correction coefficient iv may be finely adjusted intentionally with respect to the stroke amount x.

  In the first embodiment, an example in which the thrust F of the boom cylinders 15 and 16 is calculated based on the above-described formula 1 and the thrust fluctuation speed V is calculated based on the thrust F is taken as an example. Explained. However, the present invention is not limited to this. For example, when the rod side pressure of the boom cylinder can be ignored, the thrust F may be the bottom side pressure and the thrust fluctuation speed V may be the bottom side pressure fluctuation speed. The same applies to the second embodiment, the third embodiment, and the modification.

  In the first embodiment, the pilot pressure based on the operation of the work operation lever 8A is supplied to the hydraulic pilot portions 25A and 25B of the boom direction control valve 25, and the pressure sensor detects the pilot pressure. The case where the operation amount of the operation lever 8A for operation (the operation amount of the boom direction control valve 25) is detected by 35 has been described as an example. However, the present invention is not limited to this. For example, the operation amount detection means may be configured by a lever sensor (displacement sensor) that directly detects the operation amount of the operation lever. That is, as the operation amount detection means, various sensors can be used as long as they can detect the operation amount of the work operation lever or the operation amount (switching amount) of the boom direction control valve.

  More specifically, the operation amount detection means is not limited as long as it can detect the operation amount of the operation lever or the operation amount (switching amount, switching signal amount) of the boom direction control valve. Various sensors and detectors such as switches can be used depending on the configuration of the directional control valve. Further, even when a detector is not used, for example, in a configuration in which a signal corresponding to the operation amount is input / output to / from the controller from the operation means or the boom direction control valve, the controller calculates the operation amount from the signal ( Detection). In other words, the controller can also serve as an operation amount detection unit. This detects, for example, the amount of operation of the work operation lever 8A for operating hydraulic actuators other than the boom cylinders 15 and 16, such as the arm cylinder 17, the bucket cylinder 18, and a turning hydraulic motor (not shown). The same applies to the pressure sensors 41 and.

  In each embodiment and modification, the capacity of the hydraulic pump 23 (or the second hydraulic pump 61) that supplies pressure oil to the boom cylinders 15 and 16 is controlled according to the thrust fluctuation speed V of the boom cylinders 15 and 16. The case where it was set as the example demonstrated and demonstrated. In other words, each embodiment has been described by taking as an example a case where the configuration is designed to suppress vibration of the bottom side pressure of the boom cylinders 15 and 16 as hydraulic cylinders. However, the present invention is not limited to this, and may be applied to hydraulic cylinders other than boom cylinders, such as arm cylinders and bucket cylinders.

  In each embodiment and modification, the case where the hydraulic pump 23 is driven by the engine 22 as a prime mover has been described as an example. However, the present invention is not limited to this. For example, the hydraulic pump may be driven by an electric motor (electric motor).

  In each embodiment and modification, the crawler type hydraulic excavator 1 has been described as an example of the construction machine. However, the present invention is not limited to this, and may be applied to a wheel-type hydraulic excavator. Besides, it can be widely applied to various construction machines such as hydraulic cranes, wheel loaders and forklifts.

1 Excavator (construction machine)
4 Revolving frame (base)
8A Operation lever (operation means)
11 Working device 12 Boom 15, 16 Boom cylinder (hydraulic cylinder)
15C, 16C Bottom side oil chamber 15D, 16D Rod side oil chamber 22 Engine (motor)
23 Hydraulic pump (first hydraulic pump)
23B Variable capacity mechanism 25 Boom direction control valve (direction control valve)
33 Rotation sensor (rotational speed detection means)
35 Pressure sensor (operation amount detection means)
37 Bottom pressure sensor (pressure detection means)
38 Rod side pressure sensor (pressure detection means)
45, 70, 73 Controller 61 Second hydraulic pump 61B Variable capacity mechanism 62 Second boom direction control valve (second direction control valve)
71 Stroke sensor (stroke detection means)

Claims (5)

Based on a base body to which a working device is attached, a prime mover mounted on the base body, a variable displacement type hydraulic pump driven by the prime mover and having a variable capacity mechanism for increasing or decreasing a capacity, and pressure oil from the hydraulic pump A hydraulic cylinder that changes the attitude of the working device by expanding and contracting, a directional control valve that is provided between the hydraulic pump and the hydraulic cylinder, and controls the supply and discharge of pressure oil to and from the hydraulic cylinder; In a construction machine comprising operating means for operating a direction control valve and a controller for controlling the variable capacity mechanism,
A rotational speed detection means for detecting the rotational speed of the prime mover;
An operation amount detection means for detecting an operation amount of the operation means;
Pressure detecting means for detecting a bottom side pressure and a rod side pressure of the hydraulic cylinder,
The controller is
Target reference flow rate calculation means for calculating a target reference flow rate of the hydraulic pump according to a detection value of the operation amount detection means;
Thrust fluctuation speed calculating means for calculating a fluctuation speed of thrust of the hydraulic cylinder based on a detection value of the pressure detecting means;
When the fluctuation speed calculated by the thrust fluctuation speed calculation means is negative, a correction flow rate proportional to the fluctuation speed is calculated, the correction flow rate, the target reference flow rate calculated by the target reference flow rate calculation means, A construction machine comprising: a target capacity calculating means for calculating a target capacity of the hydraulic pump based on a detection value of the rotation speed detecting means. The working device includes a boom that is rotatably attached to the base body, and a boom cylinder that rotates the boom.
The hydraulic cylinder is configured as the boom cylinder,
When the boom is rotated in the anti-self-weight direction and when the fluctuation speed is negative, the target capacity calculation means determines the correction flow rate, the target reference flow rate, and the detection value of the rotation speed detection means. The construction machine according to claim 1, wherein the construction machine is configured to calculate a target capacity of the hydraulic pump based on the structure. The hydraulic pump includes one hydraulic pump,
The target capacity calculation unit is configured to calculate a target capacity of the hydraulic pump based on a total flow rate obtained by adding the target reference flow rate and the correction flow rate and a detection value of the rotation speed detection unit. The construction machine according to 1 or 2. The hydraulic pump includes two hydraulic pumps, a first hydraulic pump and a second hydraulic pump,
The target capacity calculating means includes
First target capacity calculation means for calculating a target capacity of the first hydraulic pump based on the target reference flow rate and a detection value of the rotation speed detection means;
3. The configuration according to claim 1, further comprising: a second target capacity calculation unit that calculates a target capacity of the second hydraulic pump based on the correction flow rate and a detection value of the rotation speed detection unit. Construction machinery. Stroke detecting means for detecting the stroke amount of the hydraulic cylinder;
The construction machine according to claim 1, 2, 3, or 4, wherein the target capacity calculation means is configured to adjust the correction flow rate based on a detection value of the stroke detection means.

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