JP2013160320A - Energy regeneration device for construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an energy regeneration device for a construction machine capable of improving recovery efficiency of potential energy and operability of an attachment.SOLUTION: An energy regeneration device includes a valve gear 90 and a controller 54. The valve gear 90 is capable of switching to selectively form a first state, a second state and a third state. In the first state, a head (first oil chamber) side of an assist cylinder 70 is connected to an accumulator 84, and a rod (second oil chamber) side of the assist cylinder 70 is connected to a tank 22. In the second state, the head (first oil chamber) of the assist cylinder 70 and the rod (second oil chamber) side thereof are connected to the tank 22. In the third state, the head (first oil chamber) of the assist cylinder 70 and the rod (second oil chamber) side thereof are connected to the accumulator 84. In accordance with stroke positions of work elements, the controller 54 switches a state of the valve gear 90 between two states, among the first state, the second state and the third state in a prescribed time ratio.

Description

  The present invention relates to an energy regeneration device for a construction machine.

  2. Description of the Related Art Conventionally, there is known an energy recovery device for a working machine that includes an assist cylinder that assists in an upward pivoting operation of the boom and an accumulator that accumulates pressure oil that is delivered from the assist cylinder when the boom is pivoted downward ( For example, see Patent Document 1). In this energy regeneration device, the assist cylinder is provided so that its axis is retracted with respect to the axis of the boom cylinder when the boom is pivoted upward.

JP 2004-115245 A

  However, in the configuration described in Patent Document 1 described above, by devising the mounting position of the assist cylinder as described above, the transition of the attachment gravity (assist cylinder holding pressure characteristic) is changed to the transition of the accumulator pressure (assist cylinder operating pressure). It is configured to match the characteristics as much as possible, but there is still a gap in these transitions. When such a divergence exists, potential energy recovery efficiency or attachment operability deteriorates.

  Then, an object of this invention is to provide the energy regeneration apparatus of the construction machine which can improve the collection | recovery efficiency of potential energy, and the operativity of an attachment.

In order to achieve the above object, according to one aspect of the present invention, there is provided an energy regeneration device for a construction machine that assists a work element driven by a main hydraulic cylinder with an assist cylinder.
An accumulator and a tank connected to the assist cylinder;
A valve device provided between the assist cylinder, the accumulator, and the tank, wherein the first oil chamber side of the assist cylinder is connected to the accumulator and the second oil chamber side of the assist cylinder is connected to the tank. A first state of connection, a second state of connecting the first oil chamber side and the second oil chamber side of the assist cylinder to the tank, and a first oil chamber side and a second oil chamber side of the assist cylinder A valve device switchable to selectively form a third state connected to the accumulator;
A controller for controlling the valve device,
The controller switches the state of the valve device between two states of the first state, the second state, and the third state at a predetermined time ratio according to the stroke position of the working element. An energy regeneration device is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the energy regeneration apparatus of the construction machine which can improve the collection | recovery efficiency of a positional energy and the operativity of an attachment is obtained.

It is a figure which shows the structural example of the construction machine 1 which concerns on this invention. It is a figure which shows an example of the hydraulic circuit figure of the hydraulic pump control apparatus 100 mounted in the construction machine 1. FIG. FIG. 3 is a diagram showing a main configuration of an example of an energy regeneration device 102 related to an assist cylinder 70. It is a figure which shows each state of the valve apparatus. 3 is a flowchart showing an example of main processing executed by a main controller 54. 7 is a flowchart showing another example of main processing executed by the main controller 54. It is a figure which shows the idea of the setting of each duty ratio D1, D2, D with assist target thrust and cylinder stroke. It is a figure which shows the principal part structure of energy regeneration apparatus 102 'by another example relevant to the assist cylinder. It is a figure which shows each state of valve apparatus 90 '. It is a figure which shows the alternative example of the state of valve apparatus 90 'at the time of implement | achieving a differential state and a tank state.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration example of a construction machine 1 according to the present invention. In FIG. 1, a construction machine 1 has an upper swing body 3 mounted on a crawler type lower traveling body 2 via a swing mechanism so as to be rotatable around the X axis. The upper swing body 3 includes a boom 4, an arm 5 and a bucket 6, and a boom cylinder 7, an arm cylinder 8 and a bucket cylinder 9 as hydraulic actuators for driving the boom 4, the arm 5 and the bucket 6, respectively. Is provided. The drilling attachment may be another attachment such as a breaker or a crusher.

  In addition to the boom cylinder 7, the upper swing body 3 includes an assist cylinder 70 that drives the boom 4 so as to assist the vertical movement of the boom 4. As with the boom cylinder 7, one end of the assist cylinder 70 is rotatably attached to the upper swing body 3 side, and the other end is rotatably attached to the boom 4. Two assist cylinders 70 may be provided in pairs, or three or more assist cylinders 70 may be provided. The assist cylinder 70 may be provided in parallel to the boom cylinder 7 or may be provided at an angle with respect to the boom cylinder 7. As shown in FIG. 1, the assist cylinder 70 may be provided on the front side of the boom cylinder 7, or may be provided on the rear side of the boom cylinder 7.

  In the illustrated example, the assist cylinder 70 is rotatably attached to the upper swing body 3 on the head side and rotatably attached to the boom 4 on the rod side. Further, in the illustrated example, the assist cylinder 70 is disposed in a relationship in which the raising direction of the boom 4 corresponds to the extending direction and the lowering direction of the boom 4 corresponds to the contracting direction. However, the assist cylinder 70 may be arranged in such a relationship that the raising direction of the boom 4 corresponds to the contracting direction and the lowering direction of the boom 4 corresponds to the extending direction.

  FIG. 2 is a diagram illustrating an example of a hydraulic circuit diagram of the hydraulic pump control device 100 mounted on the construction machine 1. In FIG. 2, the hydraulic circuit portion related to the assist cylinder 70 is omitted. The hydraulic circuit portion related to the assist cylinder 70 will be described later with reference to FIG.

  The hydraulic pump control device 100 includes a center bypass pipe line 30L that connects the switching valves 11L, 12L, 13L, and 15L from the two hydraulic pumps 10L and 10R that are driven by an engine or an electric motor, or switching valves 11R, 12R, Pressure oil is circulated to the tank 22 through the center bypass pipe line 30R that communicates 13R, 14R, and 15R. The hydraulic pumps 10L and 10R are variable displacement inclined plate piston pumps, and the discharge amount (cc / rev) per rotation is variable. The discharge pressures P1, P2 of the hydraulic pumps 10L, 10R are detected by pressure sensors 28L, 28R. Output signals from the pressure sensors 28L and 28R are supplied to the main controller 54.

  The switching valves 11L, 12L, 13L, and 15L and the switching valves 11R, 12R, 13R, 14R, and 15R are all open center types. That is, the switching valves 11L, 12L, 13L, and 15L and the switching valves 11R, 12R, 13R, 14R, and 15R are normally hydraulically connected by connecting their bleed-off passages to the center bypass conduits 30L and 30R. The discharge sides of the pumps 10L and 10R are connected to the tank 22.

  The switching valve 11L is a spool valve that switches the flow of pressure oil so that the hydraulic oil discharged from the hydraulic pump 10L is circulated by the traveling hydraulic motor 42L.

  The switching valve 11 </ b> R is a traveling straight valve, and traveling hydraulic motors 42 </ b> L and 42 </ b> R that drive the lower traveling body 2 and any hydraulic actuator of the upper swing body 3 (for example, boom cylinder 7, arm cylinder 8, bucket cylinder). 9 or the turning hydraulic motor 44) is operated at the same time, the hydraulic oil is circulated from the hydraulic pump 10L to the left and right traveling hydraulic motors 42L and 42R in order to improve the straight traveling performance of the lower traveling body 2. Therefore, it is a spool valve that switches the flow of pressure oil.

  The switching valve 12L is a spool valve that switches the flow of pressure oil in order to circulate the pressure oil discharged from the hydraulic pump 10L by the turning hydraulic motor 44. The switching valve 12R is a pressure oil discharged from the hydraulic pump 10R. Is a spool valve that switches the flow of pressure oil so that the hydraulic oil is circulated by the traveling hydraulic motor 42R.

  Further, the switching valves 13L and 13R supply pressure oil discharged from the hydraulic pumps 10L and 10R to the boom cylinder 7 and flow the pressure oil to discharge the pressure oil in the boom cylinder 7 to the tank 22, respectively. The switching valve 13R is a spool valve that operates when the boom operating lever of the operating device 26 is operated (hereinafter referred to as “first speed boom switching valve 13R”), and the switching valve 13L. Is a spool valve (hereinafter referred to as “second speed boom switching valve 13L”) for joining the pressure oil discharged from the hydraulic pump 10L when the boom operation lever is operated at a predetermined operation amount or more.

  The switching valve 14 </ b> R is a spool valve for supplying the pressure oil discharged from the hydraulic pump 10 </ b> R to the bucket cylinder 9 and discharging the pressure oil in the bucket cylinder 9 to the tank 22.

  Further, the switching valves 15L and 15R supply pressure oil discharged from the hydraulic pumps 10L and 10R to the arm cylinder 8, respectively, and flow the pressure oil in order to discharge the pressure oil in the arm cylinder 8 to the tank 22. The switching valve 15L is a spool valve that operates when the arm operating lever of the operating device 26 is operated (hereinafter referred to as “first speed arm switching valve 15L”), and the switching valve 15R. Is a spool valve (hereinafter referred to as “second speed arm switching valve 15R”) for joining the pressure oil discharged from the hydraulic pump 10R when the arm operation lever is operated at a predetermined operation amount or more.

  The operation device 26 is an operation device for operating the turning hydraulic motor 44, the traveling hydraulic motors 42L and 42R, the boom 4, the arm 5, and the bucket 6, and includes various levers and pedals (arm operation lever, boom operation). Lever, bucket operation lever, turning operation lever, travel pedal (right), travel pedal (left)). Electric signals representing the operation amounts of various levers and pedals in the operation device 26 are supplied to the main controller 54. The method for detecting the amount of operation of various levers and pedals by the user may be a method for detecting the pilot pressure with a pressure sensor, or a method for detecting the lever angle.

  The center bypass pipes 30L and 30R are respectively provided with negative control throttles 20L and 20R between the switching valves 15L and 15R located on the most downstream side and the tank 22 to restrict the flow of the pressure oil discharged by the hydraulic pumps 10L and 10R. This is a pressure oil pipe for generating a control pressure for the negative control system (hereinafter referred to as “negative control pressure”) upstream of the negative control throttles 20L and 20R. The negative control pressure is detected by negative control pressure sensors 27L and 27R. Output signals of the negative control pressure sensors 27L and 27R are supplied to the main controller 54.

  In the configuration shown in FIG. 2, the negative control pressure upstream of the negative control throttles 20L, 20R, the discharge pressures P1, P2, etc. are detected by the pressure sensors 27L, 27R, 28L, 28R, and the detected negative control pressures, discharge pressures P1, P2, etc. The main controller 54 obtains a target value of the discharge flow rate, and drives the electromagnetic proportional valves 57A and 55A to displace the spool valves 600L and 600R so as to obtain the target value of the discharge flow rate, thereby tilting actuators 41L and 41R. To control.

  Typically, the main controller 54 decreases the discharge amount of the hydraulic pumps 10L and 10R as the detected negative control pressure increases, and increases the discharge amount of the hydraulic pumps 10L and 10R as the detected negative control pressure decreases. To.

  As shown in FIG. 2, when any hydraulic actuator in the construction machine 1 is not used (hereinafter referred to as “standby mode”), the hydraulic oil discharged from the hydraulic pumps 10L, 10R is the center bypass pipe line 30L. , 30R to reach the negative control 20L, 20R, and increase the negative control pressure generated upstream of the negative control 20L, 20R.

  At this time, the main controller 54 displaces the spool valves 600L and 600R to the first position and drives the tilt actuators 41L and 41R to reduce the discharge amounts of the hydraulic pumps 10L and 10R. Pressure loss (pumping loss) when passing through the bypass pipes 30L and 30R is suppressed.

  On the other hand, when any hydraulic actuator in the construction machine 1 is used, the pressure oil discharged from the hydraulic pumps 10L, 10R flows into the hydraulic actuator via the switching valve corresponding to the hydraulic actuator, and the negative control throttle 20L, The amount up to 20R is reduced or eliminated, and the negative control pressure generated upstream of the negative control throttles 20L and 20R is reduced.

  At this time, the main controller 54 increases the discharge amount of the hydraulic pumps 10L and 10R, circulates sufficient pressure oil to each hydraulic actuator, and ensures the driving of each actuator.

  With the above-described configuration, the hydraulic pump control device 100 causes wasteful energy consumption in the hydraulic pumps 10L and 10R (pressure oil discharged from the hydraulic pumps 10L and 10R is generated in the center bypass pipes 30L and 30R in the standby mode. In the case of operating various hydraulic actuators while suppressing the pumping loss), necessary and sufficient pressure oil can be supplied to the various hydraulic actuators from the hydraulic pumps 10L and 10R.

  FIG. 3 is a diagram illustrating a main configuration of an example of the energy regeneration device 102 related to the assist cylinder 70.

  The energy regeneration device 102 includes an accumulator 84 connected to the assist cylinder 70. One end of the oil passage 80 is connected to the head side of the assist cylinder 70, and the other end is connected to the accumulator 84. The oil path 88 has one end connected to the rod side of the assist cylinder 70 and the other end connected to the tank 22.

  The energy regeneration device 102 also includes a valve device 90. The valve device 90 includes a first switching valve 90A and a second switching valve 90B. As illustrated, the first switching valve 90A and the second switching valve 90B may be valves (proportional valves) whose opening degree can be controlled linearly. The first switching valve 90A has an output side port connected to the head side port of the assist cylinder 70, and an input side 2 port connected to the accumulator 84 and the connection point 89, respectively. The second switching valve 90B has an output side port connected to the rod side port of the assist cylinder 70 via a connection point 89, and an input side 2 port connected to the accumulator 84 and the tank 22, respectively.

  The pressure sensor 85 detects the hydraulic pressure (accumulator pressure) generated by the accumulator 84. An output signal from the pressure sensor 85 is input to the main controller 54. The displacement sensor 87 detects the displacement (stroke position) of the assist cylinder 70. An output signal of the displacement sensor 87 is input to the main controller 54.

  FIG. 4 is a diagram illustrating each state of the valve device 90.

  FIG. 4A shows the state (switching position) of the valve device 90 when the full state (first state) is realized. In this state, the head side port of the assist cylinder 70 communicates with the accumulator 84 via the first switching valve 90A, and the rod side port of the assist cylinder 70 communicates with the tank 22 via the second switching valve 90B.

  FIG. 4B shows the state (switching position) of the valve device 90 when the differential state (third state) is realized. In this state, the head side port of the assist cylinder 70 communicates with the accumulator 84 via the first switching valve 90A, and the rod side port of the assist cylinder 70 communicates with the accumulator 84 via the second switching valve 90B. In this differential mode, an output corresponding to the pressure receiving area of the assist cylinder 70 (the difference between the rod side pressure receiving area and the head side pressure receiving area) is obtained. In this example, since the extension direction of the assist cylinder 70 corresponds to the raising direction of the boom 4, the head side pressure receiving area is larger than the rod side pressure receiving area.

  FIG. 4C shows a state (switching position) of the valve device 90 when the tank state (second state) is realized. In this state, the head side port of the assist cylinder 70 communicates with the tank 22 via the first switching valve 90A, and the rod side port of the assist cylinder 70 communicates with the tank 22 via the second switching valve 90B.

  In this manner, the valve device 90 can be switched to each of the three states under the control of the main controller 54. Therefore, the main controller 54 can realize desired assist characteristics by changing the time ratio (duty ratio) of each state of the valve device 90 according to the stroke position of the boom 4.

  When the assist cylinder 70 is arranged in a relationship corresponding to the contraction direction when the boom 4 is in the raising direction and corresponding to the extension direction when the boom 4 is in the lowering direction, the valve device 90 is The rod side port of 70 communicates with the accumulator 84 via the first switching valve 90A, and the head side port of the assist cylinder 70 communicates with the tank 22 via the second switching valve 90B. (First state) may be realized.

  FIG. 5 is a flowchart showing an example of main processing executed by the main controller 54.

  In step 500, an operation lever signal (a signal indicating the operation amount of the boom operation lever of the operation device 26) is received.

  In step 502, the stroke position (attachment position) of the boom 4 is received. The stroke position of the boom 4 may be determined based on an output signal from the displacement sensor 87.

  In step 504, the assist target thrust is determined based on the operation lever signal and the stroke position of the boom 4. The assist target thrust is a target value of the assist thrust that should be generated by the assist cylinder 70. The relationship between the operation lever signal (the amount of operation of the boom operation lever), the stroke position of the boom 4, and the assist target thrust at that time may be held in advance as a map. For example, when the operation amount of the boom operation lever is substantially zero, the assist target thrust may be determined so as to substantially match the boom cylinder holding thrust according to the stroke position of the boom 4. On the other hand, when the operation amount of the boom operation lever is increased, the assist target thrust may be determined to be larger when the boom cylinder holding thrust corresponding to the stroke position of the boom 4 is larger and smaller when the boom is lowered. In addition, the characteristic of the boom cylinder holding thrust according to the stroke position of the boom 4 may be acquired by a test or the like. Further, the characteristics of the boom cylinder holding thrust according to the stroke position of the boom 4 may vary depending on the position of the arm 5 and the position of the bucket 6 at that time, and may be acquired in advance for each.

  In step 506, accumulator pressure is received. For example, the accumulator pressure may be detected by a pressure sensor 85 (see FIG. 3) provided in the oil passage 80.

  In step 508, it is determined whether or not the assist target thrust is greater than the product of the accumulator pressure and the differential state pressure receiving area. The differential state pressure receiving area corresponds to the pressure receiving area of the assist cylinder 70 in the differential state (FIG. 4B). Therefore, in step 508, it is determined whether or not the assist target thrust is larger than the assist thrust generated when the differential state is realized based on the current accumulator pressure. If the assist target thrust is greater than the product of the accumulator pressure and the assist cylinder differential pressure receiving area, the process proceeds to step 510; otherwise, the process proceeds to step 514.

In step 510, a duty ratio D1 for switching between the full state (FIG. 4A) and the differential state (FIG. 4B) is determined. The duty ratio D1 (= full state time: differential state time) may be calculated by the following equation, for example.
D1 = (Assist target thrust−Accumulator pressure × Differential state pressure receiving area): (Accumulator pressure × Full state pressure receiving area−Assist target thrust)
Here, the full state pressure receiving area corresponds to the pressure receiving area of the assist cylinder 70 in the full state (FIG. 4A). For example, when the head pressure receiving area of the assist cylinder 70 is 2 and the rod side pressure receiving area of the assist cylinder 70 is 1, the full pressure receiving area is 2, and the differential pressure receiving area is 1. .

  In step 512, the valve device 90 is switched between the full state (FIG. 4A) and the differential state (FIG. 4B) at the duty ratio D1 calculated in step 510.

In step 514, the duty ratio D2 for switching between the differential state (FIG. 4B) and the tank state (FIG. 4C) is determined. The duty ratio D2 (= differential state time: tank state time) may be calculated by the following equation, for example.
D2 = (Assist target thrust−accumulator pressure × tank state pressure receiving area): (accumulator pressure × differential state pressure receiving area−assist target thrust)
Here, the tank state pressure receiving area corresponds to the pressure receiving area of the assist cylinder 70 in the tank state (FIG. 4C) and is zero.

  In step 516, the valve device 90 is switched between the differential state (FIG. 4B) and the tank state (FIG. 4C) at the duty ratio D2 calculated in step 514.

  FIG. 6 is a flowchart showing another example of main processing executed by the main controller 54.

  The processing from step 600 to step 606 shown in FIG. 6 is the same as the processing from step 500 to step 506 shown in FIG.

In step 608, the duty ratio D for switching between the full state (FIG. 4A) and the tank state (FIG. 4C) is determined. The duty ratio D (= full state time: tank state time) may be calculated by the following equation, for example.
D = (Assist target thrust−accumulator pressure × tank state pressure receiving area): (accumulator pressure × full state pressure receiving area−assist target thrust)
In step 610, the valve device 90 is switched between the full state (FIG. 4A) and the tank state (FIG. 4C) at the duty ratio D calculated in step 608.

  The main processes shown in FIGS. 5 and 6 can be combined. For example, in the process shown in FIG. 5, the processes in steps 608 and 610 in FIG. 6 may be executed instead of the processes in steps 510 and 512 in FIG. Similarly, in the process shown in FIG. 5, the processes in steps 608 and 610 in FIG. 6 may be executed instead of the processes in steps 514 and 516 in FIG. When the assist cylinder 70 is arranged in a relationship corresponding to the contraction direction when the boom 4 is in the raising direction and corresponding to the extension direction when the boom 4 is in the lowering direction, the main processing shown in FIG. It is preferable to use it.

  FIG. 7 is a diagram related to FIG. 5 and FIG. 6, and shows the concept of setting the duty ratios D1, D2, and D together with the assist target thrust and the cylinder stroke. The horizontal axis indicates the cylinder stroke (the length of the boom cylinder 7), and the vertical axis indicates each thrust.

  In FIG. 7, the characteristic of the assist target thrust is shown as being the same as the boom cylinder holding thrust. However, as described above, the assist target thrust is not necessarily the same as the boom cylinder holding thrust. In addition, the boom cylinder holding thrust characteristic is simply constant. FIG. 7 also shows the thrust in the full state (accumulator pressure x full state pressure receiving area), the thrust in the differential state (accumulator pressure x differential state pressure receiving area), and the thrust in the tank state (accumulator pressure x tank state). The pressure receiving area) is shown.

  According to the process shown in FIG. 5, as shown in FIG. 7, in the section where the assist target thrust is larger than the thrust in the differential state, the full state (FIG. 4 (A)) and the differential state (FIG. 4 ( B)) is switched at a high speed with a duty ratio D1. Further, in a section where the assist target thrust is smaller than the thrust in the differential state, high-speed switching is performed between the differential state (FIG. 4B) and the tank state (FIG. 4C) by the duty ratio D2. To be implemented. Further, according to the process shown in FIG. 6, as shown in FIG. 7, the duty ratio is changed between the full state (FIG. 4A) and the tank state (FIG. 4C) over the entire section. Fast switching is performed by D.

  By the way, as shown in FIG. 5, the characteristics of the accumulator pressure are the same as the characteristics of the thrust in the differential state where the pressure receiving area is 1, for example, which is large when the cylinder stroke is small and decreases as the cylinder stroke increases. Become. This accumulator pressure characteristic deviates greatly from the boom cylinder holding thrust characteristic. Therefore, in the configuration in which the assist thrust is generated using the accumulator pressure as it is, the potential energy recovery efficiency or the operability of the attachment deteriorates. For example, the configuration using only the thrust in the differential state is more advantageous than the configuration using only the thrust in the full state, for example, because it approaches the characteristics of the boom cylinder holding thrust. The divergence is large, and the recovery efficiency of position energy or the operability of the attachment is deteriorated.

  In contrast, according to the present embodiment, the characteristic of the assist target thrust can be brought close to the boom cylinder holding thrust by switching at high speed between at least two states at a duty ratio corresponding to the cylinder stroke. Thereby, the operability of the attachment can be improved together with the recovery efficiency of potential energy.

  FIG. 8 is a diagram illustrating a main configuration of an energy regeneration device 102 ′ according to another example related to the assist cylinder 70. As illustrated in FIG. The same components as those of the valve device 90 shown in FIG. 2 are denoted by the same reference numerals and description thereof is omitted.

  The energy regeneration device 102 ′ includes an accumulator 84 that is connected to the assist cylinder 70 via an oil passage 80. That is, the oil passage 80 has one end connected to the head side of the assist cylinder 70 and the other end connected to the accumulator 84. The oil path 88 has one end connected to the rod side of the assist cylinder 70 and the other end connected to the tank 22.

  The energy regeneration device 102 ′ also includes a valve device 90 ′. The valve device 90 ′ includes a first switching valve 90A ′ and a second switching valve 90B ′. The first switching valve 90A ′ and the second switching valve 90B ′ may be valves (proportional valves) whose opening degree can be controlled linearly as illustrated. The first switching valve 90A ′ and the second switching valve 90B ′ shown in FIG. 8 are three-position switching valves. This point is that the first switching valve 90A and the second switching valve 90B shown in FIG. This is different from the valve device 90 which is a switching valve. The first switching valve 90A ′ has an output side port connected to the head side port of the assist cylinder 70, and an input side 2 port connected to the accumulator 84 and the connection point 89, respectively. The second switching valve 90B ′ has an output side port connected to the rod side port of the assist cylinder 70 via a connection point 89, and two input side ports connected to the accumulator 84 and the tank 22, respectively.

  The bypass oil passage 92 connects the connection point 89 and the tank 22 by bypassing the second switching valve 90B ′. The bypass oil passage 92 includes a check valve 92a, and the check valve 92a allows only the flow from the tank 22 to the connection point 89 (the rod side port of the assist cylinder 70). The bypass oil passage 94 bypasses the first switching valve 90 </ b> A ′ and connects the head side port of the assist cylinder 70 and the tank 22. The bypass oil passage 94 includes a check valve 94a, and the check valve 94a allows only the flow from the tank 22 to the head side port of the assist cylinder 70.

  FIG. 9 is a diagram showing each state of the valve device 90 ′.

  FIG. 9A shows the state (switching position) of the valve device 90 ′ when realizing the full state during the raising operation of the boom 4. In this state, the head side port of the assist cylinder 70 communicates with the accumulator 84 via the first switching valve 90A ′, and the rod side port of the assist cylinder 70 communicates with the tank 22 via the second switching valve 90B ′. To do. In this state, when the boom 4 is raised, the oil flows into the tank 22 from the rod side port of the assist cylinder 70.

  FIG. 9B shows the state (switching position) of the valve device 90 ′ when the full state during the lowering operation of the boom 4 is realized. In this state, the head side port of the assist cylinder 70 communicates with the accumulator 84 via the first switching valve 90A ′, and the rod side port of the assist cylinder 70 passes through the bypass oil passage 92 (check valve 92a). It communicates with the tank 22. Therefore, in this state, when the boom 4 is lowered, oil is sucked from the tank 22 into the rod side port of the assist cylinder 70 via the check valve 92a.

  FIG. 9C shows the state (switching position) of the valve device 90 ′ when the differential state is realized. In this state, the head side port of the assist cylinder 70 communicates with the accumulator 84 via the first switching valve 90A ′, and the rod side port of the assist cylinder 70 communicates with the accumulator 84 via the second switching valve 90B ′. To do.

  FIG. 9D shows the state (switching position) of the valve device 90 ′ when realizing the tank state during the raising operation of the boom 4. In this state, the head side port of the assist cylinder 70 communicates with the tank 22 via the bypass oil passages 92 and 94 (check valves 92a and 94a), and the rod side port of the assist cylinder 70 is connected to the bypass oil passage 92 ( The tank 22 communicates with the check valve 92a).

  FIG. 9E shows the state (switching position) of the valve device 90 ′ when the tank state during the lowering operation of the boom 4 is realized. In this state, the head side port of the assist cylinder 70 communicates with the tank 22 via the first switching valve 90A ′ and the second switching valve 90B ′, and the rod side port of the assist cylinder 70 is the second switching valve 90B ′. It communicates with the tank 22 via

  Also in the configuration shown in FIG. 8, the control method by the main controller 54 described with reference to FIGS. 5 and 6 may be used. However, during the raising operation of the boom 4, the state shown in FIG. 9A is formed as a full state, and the state shown in FIG. 9D is formed as a tank state. Accordingly, when the boom 4 is raised, when the full state and the tank state are switched at high speed (for example, step 610 in FIG. 6), the high-pressure oil introduced into the head side port of the assist cylinder 70 in the full state is tanked in the tank state. It is possible to prevent the instantaneous return to 22 and to realize a highly efficient switching. Alternatively, during the raising operation of the boom 4, the state shown in FIG. 9C is formed as the differential state, and the state shown in FIG. 9D is formed as the tank state. As a result, when the boom 4 is raised, when the differential state and the tank state are switched at high speed (for example, step 516 in FIG. 5), the same pressure is prevented from being lost and switching with high efficiency can be realized. . Further, when the boom 4 is lowered, the state shown in FIG. 9B is formed as a full state, and the state shown in FIG. 9C is formed as a differential state. As a result, when the boom 4 is lowered, when switching between the full state and the differential state at high speed (for example, step 512 in FIG. 5), the same pressure is prevented from being lost and switching with high efficiency can be realized. .

  FIG. 10 is a diagram showing an alternative example of the state of the valve device 90 ′ when realizing the differential state and the tank state.

  FIG. 10A shows an alternative example of the state (switching position) of the valve device 90 ′ when realizing the differential state. In this state, the head side port of the assist cylinder 70 communicates with the accumulator 84 via the first switching valve 90A ′ and the second switching valve 90B ′, and the rod side port of the assist cylinder 70 is connected to the second switching valve 90B ′. To the accumulator 84. The state shown in FIG. 10A may be used instead of the state shown in FIG.

  FIG. 10B shows an alternative example of the state (switching position) of the valve device 90 ′ when realizing the tank state during the raising operation of the boom 4. In this state, the head side port of the assist cylinder 70 communicates with the tank 22 via the bypass oil passage 94 (check valve 94a), and the rod side port of the assist cylinder 70 passes through the second switching valve 90B ′. It communicates with the tank 22. The state shown in FIG. 10B may be used instead of the state shown in FIG.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  For example, although the assist cylinder 70 is provided for the boom 4 in the above-described embodiment, it may be provided for another work element (for example, the arm 5).

  In the above-described embodiment, the circuit is configured by using a switching valve having three or more ports. However, a similar circuit may be configured by combining a plurality of 2-port simple shut-off valves. .

  In the above description, the hydraulic circuit having a specific configuration shown in FIG. 3 is disclosed, but the configuration of the hydraulic circuit is various. For example, a part of the hydraulic actuator may be realized by a hydraulic pump driven by an electric motor. Further, a hydraulic circuit that realizes a control method other than negative control (for example, positive control) may be used.

DESCRIPTION OF SYMBOLS 1 Construction machine 2 Lower traveling body 3 Upper turning body 4 Boom 5 Arm 7 Boom cylinder 8 Arm cylinder 9 Bucket cylinder 10L, 10R Hydraulic pump 11L, 11R Switching valve 12L, 12R Switching valve 13L, 13R Switching valve 14R Switching valve 15L, 15R Switching valve 20L, 20R Negative control throttle 22 Tank 26 Operating device 27L, 27R Negative control pressure sensor 28L, 28R Pressure sensor 30L, 30R Center bypass pipe 41L, 41R Tilt actuator 42L, 42R Traveling hydraulic motor 44 Turning hydraulic motor 54 main Controller 55A, 57A Proportional solenoid valve 70 Assist cylinder 80, 88 Oil passage 84 Accumulator 85 Pressure sensor 87 Displacement sensor 90, 90 'Valve device 90A, 90A' First switching valve 90B, 90B ' Second switching valve 100 Hydraulic pump control device 102, 102 'Energy regeneration device

Claims (5)

An energy regeneration device for a construction machine that drives a work element driven by a main hydraulic cylinder with an assist cylinder.
An accumulator and a tank connected to the assist cylinder;
A valve device provided between the assist cylinder, the accumulator, and the tank, wherein the first oil chamber side of the assist cylinder is connected to the accumulator and the second oil chamber side of the assist cylinder is connected to the tank. A first state of connection, a second state of connecting the first oil chamber side and the second oil chamber side of the assist cylinder to the tank, and a first oil chamber side and a second oil chamber side of the assist cylinder A valve device switchable to selectively form a third state connected to the accumulator;
A controller for controlling the valve device,
The controller switches the state of the valve device between two states of the first state, the second state, and the third state at a predetermined time ratio according to the stroke position of the working element. An energy regenerative device.   The controller determines the state of the valve device between the first state and the third state, or between the second state and the third state, depending on the position of the working element. The energy regeneration device according to claim 1, wherein the energy regeneration device is switched at a time ratio of An energy regeneration device for a construction machine that drives a work element driven by a main hydraulic cylinder with an assist cylinder.
An accumulator and a tank connected to the assist cylinder;
A valve device provided between the assist cylinder, the accumulator, and the tank, wherein the first oil chamber side of the assist cylinder is connected to the accumulator and the second oil chamber side of the assist cylinder is connected to the tank. A valve device that can be switched to selectively form a first state of connection and a second state of connecting the first oil chamber side and the second oil chamber side of the assist cylinder to the tank;
A controller for controlling the valve device,
The controller switches the state of the valve device between the first state and the second state at a predetermined time ratio in accordance with the stroke position of the working element. . The controller calculates an assist target thrust by the assist cylinder according to a stroke position of the work element, and calculates an assist thrust generated in each switching state based on an accumulator pressure generated by the accumulator. ,
The energy regeneration device according to claim 1, wherein the controller determines the predetermined time ratio based on the assist target thrust and the assist thrust generated in each state. .   The energy regeneration device according to claim 1, wherein the work element is a boom.

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