JP2013002453A - Working machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a working machine capable of setting the relationship between an operation quantity of an operation member of an operation device and a speed of operation of a working device, constant, without being influenced by a load acting on a hydraulic cylinder.SOLUTION: This working machine includes: an operation direction control means 30a for switching a valve position of a directional control valve 13 to a first valve position b1 or a second valve position b2 based on a command (the operation direction D and U directions from a neutral position of an operation lever 19a) of the operation direction of the working device by the operation device 19, and controlling opening of the directional control valve 13 in the same every time, even when switching the valve position of the directional control valve 13 to any of the first and second valve positions; and a delivery flow rate control means 30b for controlling a delivery flow rate of a hydraulic pump 12 by controlling a rotating speed of an electric motor 11 via an inverter 11a based on a command (the operation quantity of the operation lever 19a) of an operation speed of the working device by the operation device 19.

Description

  The present invention relates to a work machine including a work device that is driven by a hydraulic cylinder and lifts and lowers a load.

  As this type of work machine, there is one disclosed in Patent Document 1. The work machine includes a hydraulic pump, a hydraulic cylinder that is driven by being supplied with discharge oil of the hydraulic pump, a crane (working device) that is driven by the hydraulic cylinder and operates in the vertical direction, the hydraulic pump and the hydraulic cylinder A hydraulic pilot-type switching valve (direction control valve) for controlling the flow of pressure oil supplied from the hydraulic pump to the hydraulic cylinder, an operating lever (operating device), A means for applying a pilot pressure to the switching valve according to the operation direction and the operation amount, and a pipe line on the meter-out side (discharge side) of the hydraulic cylinder when the load is lowered by the downward rotation of the crane. A counter balance valve that operates with the cylinder-side pressure (supply side) of the cylinder as a pilot pressure.

JP-A-5-187408 (paragraphs 0002 to 0005)

  In the work machine disclosed in Patent Document 1 described above, the operation device (operation lever) is operated in accordance with the operation amount of the direction control valve (switching valve) provided between the hydraulic pump and the hydraulic cylinder. When the pilot pressure is applied, the opening degree of the directional control valve changes, thereby changing the flow rate of the pressure oil supplied to the hydraulic cylinder. That is, the flow rate of the pressure oil supplied from the hydraulic pump to the hydraulic cylinder, that is, the speed of operation of the working device is controlled by controlling the opening degree of the direction control valve according to the operation amount of the operating device. .

  For this reason, even when the operation amount of the operating device is constant, when the load acting on the hydraulic cylinder changes with the change in the posture (angle) of the working device (crane), that is, the pressure oil to the hydraulic cylinder When the ease of inflow changes, the flow rate of the pressure oil supplied from the hydraulic pump to the hydraulic cylinder changes, and the speed of operation of the work device changes accordingly. In addition, when the load with a small weight is raised and lowered by the vertical movement of the work device, and when the load with a heavy weight is raised and lowered, the speed of operation of the work device is the same even if the operation amount of the operation device is the same. It will be different. That is, since the relationship between the operation amount of the operating device and the speed of operation of the work device is not constant, the work device may operate at a speed contrary to the will of the operator.

  The present invention has been made in consideration of the above-described circumstances, and the object thereof is influenced by the load acting on the hydraulic cylinder, the relationship between the operation amount of the operation member of the operation device and the speed of operation of the work device. An object of the present invention is to provide a work machine that can be made constant without any problems.

  In order to achieve the above object, a work machine according to the present invention is configured as follows.

[1] A work machine according to the present invention includes a hydraulic pump, a hydraulic cylinder that is driven by being supplied with oil discharged from the hydraulic pump, a working device that is driven by the hydraulic cylinder to raise and lower a load, and an operation member. An operation device that commands each of the direction and speed of operation of the work device based on each of the operation direction and the operation amount, and the flow of pressure oil supplied from the hydraulic pump to the hydraulic cylinder based on the command from the operation device And a control means for controlling the direction and flow rate of the hydraulic cylinder, and a pipe on the meter-out side of the hydraulic cylinder when the operation of the working device is performed downward, and the pressure on the meter-in side of the hydraulic cylinder at that time In a work machine including a counter balance valve that operates as a pilot pressure, the control means includes the hydraulic pump and the hydraulic cylinder. A directional control valve that is provided between and capable of switching to a neutral position for stopping the hydraulic cylinder, a first valve position for contracting the hydraulic cylinder, and a second valve position for extending the hydraulic cylinder; The valve position of the directional control valve is switched to the first valve position or the second valve position based on the command of the direction of operation of the working device by the control device, and the valve position of the directional control valve is changed to the first and second valve positions. Regardless of the operation amount of the operating device, regardless of the operation amount of the operating device, the operation direction control means for controlling the opening degree of the directional control valve to a predetermined opening degree, and the operation of the working device by the operating device And a discharge flow rate control means for controlling the discharge flow rate of the hydraulic pump based on the speed command.

  In a state where the opening degree of the direction control valve is constant, the flow rate of the pressure oil supplied from the hydraulic pump to the hydraulic cylinder through the direction control valve is proportional to the discharge flow rate of the hydraulic pump. In the work machine described in “[1]”, when the operation direction control means switches the valve position of the direction control valve to one of the first and second valve positions, the direction control is performed regardless of the operation amount of the operation device. Since the opening degree of the valve is controlled to a predetermined opening degree, the discharge flow rate control means controls the discharge flow rate of the hydraulic pump based on the operation speed of the working device commanded by the operation device, that is, the operation amount of the operation member. The relationship between the operation amount of the operating device and the speed of operation of the work device can be made constant without being affected by the load acting on the hydraulic cylinder.

[2] The work machine according to the present invention is the work machine according to “[1]”, wherein the meter-out side pipe line includes the meter-out side between the counter balance valve and the hydraulic cylinder. A pressure control valve that adjusts the pressure in the meter-in side pipe line by controlling a back pressure generated in the pipe line, and the pressure control valve is configured to control the meter-in side pressure based on the pressure in the meter-in side pipe line. The back pressure in the pipe on the side is controlled by the back pressure adjusting means so that the pressure in the pipe on the meter-in side becomes equal to or higher than the starting pressure of the counter balance valve.

  When the discharge oil of the hydraulic pump is supplied to the hydraulic cylinder in order to operate the working device downward, the pressure on the meter-in side of the hydraulic cylinder rises due to the back pressure on the meter-in side. When the pressure on the meter-in side becomes equal to or higher than the starting pressure of the counter balance valve, the counter balance valve opens. As a result, the hydraulic cylinder contracts, and the working device operates downward along with this.

  When the work device moves downward and unloads the load, an inertial force acts on the load, so the work device moves downward faster than the speed corresponding to the flow rate of the pressure oil supplied to the hydraulic cylinder. Accordingly, the pressure on the meter-in side of the hydraulic cylinder may be lower than the starting pressure of the counter balance valve. In this case, the counter balance valve is closed, and accordingly, the flow of the pressure oil on the meter-out side of the hydraulic cylinder is prevented, so that the working device stops the downward operation. Thereafter, when the pressure on the meter-in side of the hydraulic cylinder rises above the starting pressure of the counter balance valve, the counter balance valve is opened again, whereby the working device resumes downward operation.

  There is a response delay in the timing at which the counter balance valve is closed with respect to the timing at which the pressure on the meter-in side of the hydraulic cylinder becomes lower than the starting pressure of the counter balance valve. For this reason, the counter balance valve alternately repeats the closing operation and the opening operation, and accordingly, the back pressure on the meter-out side of the hydraulic cylinder alternately repeats a rapid increase and decrease. As a result, a phenomenon occurs in the hydraulic cylinder in which the stop of the contraction and the restart of the contraction are alternately repeated, that is, hunting occurs. In the work machine described in “[2]”, the pressure control valve is configured such that the back pressure of the meter-in side pipe line is based on the pressure of the meter-in side pipe line, the pressure of the meter-in side pipe line is Since it is controlled by the back pressure adjusting means so as to be equal to or higher than the starting pressure, the work machine described in “[2]” can prevent the counter balance valve from repeating the closing operation and the opening operation alternately. Cylinder hunting can be reduced.

[3] A work machine according to the present invention is the work machine according to “[1]” or “[2]”, wherein the work device is driven by the hydraulic cylinder and operates in an up-and-down direction. And a gripping device that grips a load provided at the tip of the arm.

  The work machine described in “[3]” raises and lowers the load gripped by the gripping device by the vertical movement of the arm. At this time, the operation direction control means and the discharge flow rate control means described in “[1]” affect the relationship between the operation amount of the operation device and the operation speed of the work device by the load acting on the hydraulic cylinder. It can be made constant. Further, when the load is lowered by moving the arm downward, the vertical vibration of the arm due to the inertial force acting on the load can be reduced by the back pressure adjusting means described in “[2]”.

  According to the work machine of the present invention, as described above, the relationship between the operation amount of the operation member of the operation device and the operation speed of the work device is made constant without being affected by the load acting on the hydraulic cylinder. Can do. As a result, it is possible to prevent the work device from moving upward or downward at a speed contrary to the will of the operator.

It is a side view of the handling machine which is a working machine concerning one embodiment of the present invention. It is a hydraulic circuit diagram which shows the hydraulic drive device for operating the arm shown in FIG. 1 to the up-down direction. It is a figure which shows the correspondence of the pressure in the rod chamber of the raising / lowering cylinder shown in FIG. 2, and the starting pressure of a pressure-reduction valve. It is a flowchart which concerns on control of the starting pressure of the pressure reducing valve shown in FIG.

  A working machine according to an embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the work machine 1 according to the present embodiment is a handling machine. The work machine 1 includes a traveling body 2 that travels by driving a crawler belt, a revolving body 3 that is turnable on the traveling body 2, and a work device 4 that is provided on the revolving body 3. .

  The working device 4 includes a telescopic arm 5 that is operably coupled to the swing body 3 in a vertical direction, and a gripping device 6 that is provided at the tip of the arm 5 so as to be pivotable in the vertical direction and the horizontal direction. Prepare. The arm 5 is driven by a hoisting cylinder 21 (hydraulic cylinder) to rotate up and down with respect to the revolving body 3, and is also driven by an expansion / contraction cylinder 22 (hydraulic cylinder) so as to expand and contract. It has become. The gripping device 6 is driven by a vertical swing cylinder 23 (hydraulic cylinder) to rotate in the vertical direction with respect to the arm 5, and is driven by a horizontal swing cylinder 24 (hydraulic cylinder) to move the arm 5. It rotates in the left-right direction. The gripping device 6 grips a load by rotating the movable claw 6a in the direction of the fixed claw 6b. The movable claw 6a is moved closer to the fixed claw 6b by a gripping cylinder 25 (hydraulic cylinder). Driven away.

  As shown in FIG. 2, the work machine 1 includes a dedicated hydraulic drive device 10 for causing the arm 5 to perform an up and down operation. The hydraulic drive device 10 includes an electric motor 11, a hydraulic pump 12 that is driven by the output of the electric motor 11, and the above-described undulation cylinder 21 that is driven by being supplied with oil discharged from the hydraulic pump 12 ( A single rod type double acting cylinder) and a directional control valve 13 provided between the hydraulic pump 12 and the undulation cylinder 21. Details of the electric motor 11, the hydraulic pump 12, and the direction control valve 13 will be described below.

  The electric motor 11 is driven by being supplied with electric power from the inverter 11a. The power source of the inverter 11a is a generator (not shown) driven by a diesel engine (not shown) or a power storage device (not shown) that stores the electric power generated by the generator.

  The hydraulic pump 12 is a constant capacity type, and discharges pressure oil at a flow rate proportional to the rotational speed. Further, the maximum discharge pressure of the hydraulic pump 12 is regulated by the relief valve 12a.

  The direction control valve 13 is a spring center type three-position valve, and includes a pump port 13 c connected to the hydraulic pump 12, a tank port 13 d connected to the hydraulic oil tank 14, and a undulation cylinder 21 via a pipe 15. A rod chamber side port 13e connected to the rod chamber 21a, and a bottom chamber side port 13f connected to the bottom chamber 21b of the hoisting cylinder 21 via a pipe line 16. The direction control valve 13 includes a pair of solenoids 13a and 13b, and is an electrically operated valve that is operated by supplying electric power to any one of the solenoids 13a and 13b. The valve position of the directional control valve 13 is switched from the neutral position b0 to the first valve position b1 when electric power is supplied to the solenoid 13a, and conversely, when electric power is supplied to the solenoid 13b, the second position from the neutral position b0 is changed. Switch to valve position b2. In the neutral position b0, the expansion and contraction of the hoisting cylinder 21 is stopped by blocking the pump port 13c, the tank port 13d, the rod chamber side port 13e and the bottom chamber side port 13f from each other, that is, the length of the hoisting cylinder 21 is increased. The valve position to maintain. The first valve position b1 is configured to connect the pump port 13c to the rod chamber side port 13e and connect the tank port 13d to the bottom chamber side port 13f, thereby hydraulically reducing the flow of pressure oil that contracts the undulation cylinder 21. The valve position is generated between the pump 12, the undulation cylinder 21, and the hydraulic oil tank 14. In the second valve position b2, the pump port 13c is connected to the bottom chamber side port 13f, and the tank port 13d is connected to the rod chamber side port 13e, whereby the flow of pressure oil that extends the hoisting cylinder 21 is hydraulically controlled. The valve position is generated between the pump 12, the undulation cylinder 21, and the hydraulic oil tank 14.

  The hydraulic drive device 10 further includes an operating device 19 for instructing each of the operating direction and speed of the work device 4 in the form of an electric signal based on the operating direction and operating amount of the operating lever 19a, and the operating device 19 And a controller 30 for controlling the directional control valve 13 and the inverter 11a based on a command from Details of the operation device 19 and the controller 30 will be described next.

  The operating lever 19a of the operating device 19 is an operating member that can be operated in two opposite directions from the neutral position, that is, in the D direction and the U direction. The operating device 19 commands the downward operation of the arm 5 of the working device 4 based on the tilting operation of the operating lever 19a in the D direction, and the operation amount of the operating lever 19a at this time, that is, from the neutral position to the D direction. Based on the tilt angle of the operating lever 19a, the speed of the downward movement of the work device 4 is commanded. The operating device 19 commands the upward movement of the arm 5 of the working device 4 based on the tilting operation of the operating lever 19a in the U direction, and the operation amount of the operating lever 19a at this time, that is, from the neutral position. Based on the tilt angle of the operation lever 19a in the U direction, the speed of the upward operation of the work device 4 is commanded.

  The controller 30 is a microcomputer including a CPU, a ROM, and a RAM. The controller 30 controls the direction control valve 13 to control the operation direction of the hoisting cylinder 21, and the electric motor via the inverter 11a. And a discharge flow rate control means 30b for controlling the discharge flow rate of the hydraulic pump 12 by controlling the rotation speed of the hydraulic pump 11. These operation direction control means 30 a and discharge flow rate control means 30 b are means that operate according to a control program written in the ROM of the controller 30. Details of the operation direction control means 30a and the discharge flow rate control means 30b will be described below.

  The operation direction control means 30a has a correspondence relationship between a command of the operation direction of the arm 5 by the operation device 19 (operation direction from the neutral position of the operation lever 19a) and a current applied to the solenoids 13a and 13b of the direction control valve 13. The valve position and opening of the directional control valve 13 are controlled based on the direction of operation of the arm 5 that is stored in advance in the ROM of the controller 30 and commanded by the operating device 19. Specifically, the movement direction control means 30a supplies a current having a current value I1 (fixed value) to the solenoid 13a of the direction control valve 13 when the operation device 19 instructs the downward movement of the arm 5. Thus, the valve position of the direction control valve 13 is switched to the first valve position b1. At this time, the opening degree of the directional control valve 13 at the first valve position b1 is controlled to a predetermined opening degree OP1 regardless of the operation amount of the operating device 19. Further, the operation direction control means 30a supplies a current having a current value I2 (fixed value) to the solenoid 13b of the direction control valve 13 when the operation device 19 instructs the upward movement of the arm 5. The valve position of the direction control valve 13 is switched to the second valve position b2. At this time, as described above, the opening degree of the directional control valve 13 at the second valve position b2 is controlled to the predetermined opening degree OP2 regardless of the operation amount of the operating device 19.

  The discharge flow rate control means 30b stores in advance in the ROM of the controller 30 the correspondence relationship between the operation speed command by the operation device 19 (the operation amount from the neutral position of the operation lever 19a) and the rotation speed of the hydraulic pump 12. The inverter 11a is controlled so that the rotational speed of the hydraulic pump 12 corresponding to the operation speed command of the work device 4 commanded by the operation device 19 is obtained.

  The hydraulic drive device 10 further includes a counter balance valve 17 in the pipe line 16, that is, the pipe line on the meter-out side of the hoisting cylinder 21 when the downward movement of the arm 5 is performed. The counter balance valve 17 is a valve that operates using the pressure in the pipe line 15, that is, the pressure Pl in the rod chamber 21 a of the hoisting cylinder 21 as an external pilot pressure. The counter balance valve 17 opens when the pressure Pl in the rod chamber 21a of the hoisting cylinder 21 is equal to or higher than the starting pressure Pc defined by the return spring 17a, and the pressure Pl in the rod chamber 21a of the hoisting cylinder 21 is high. It operates so that the opening degree becomes larger as it becomes. In other words, when the pressure in the rod chamber 21a of the hoisting cylinder 21 is low in a state of the starting pressure Pc or higher, the opening is reduced and the back pressure in the bottom chamber 21b of the hoisting cylinder 21 is increased. . The starting pressure Pc is a negative pressure in the rod chamber 21a of the hoisting cylinder 21 due to the inertial force acting on the working device 4 when the arm 5 moves downward while the gripping device 6 is not gripping a load. In order to prevent this, that is, to prevent the arm 5 from moving downward faster than the speed corresponding to the flow rate of the pressure oil supplied to the hoisting cylinder 21, a back pressure is applied to the hoisting cylinder 21. The counter balance valve 17 is set to open so as to be generated on the meter-out side (in the bottom chamber 21b of the hoisting cylinder 21). When the inside of the rod chamber 21a of the hoisting cylinder 21 becomes lower than the starting pressure Pc of the counter balance valve 17, the counter balance valve 17 is closed, thereby the flow of pressure oil on the meter-out side of the hoisting cylinder 21. That is, the pressure oil is prevented from being discharged from the bottom chamber 21b of the hoisting cylinder 21, and as a result, the arm 5 stops its downward movement.

  The counter balance valve 17 is provided with a check valve 32 in parallel. This check valve 32 permits the flow of pressure oil in the direction from the bottom chamber side port 13f of the direction control valve 13 toward the bottom chamber 21b of the hoisting cylinder 21, and blocks the flow of pressure oil in the opposite direction.

  The hydraulic drive device 10 is further provided between the counter balance valve 17 and the undulation cylinder 21 and is a proportional electromagnetic pressure reducing valve 18 that is a pressure control valve that functions as a variable throttle that throttles the flow path of the pipe line 16. And a pressure sensor 31 that converts the pressure in the pipe line 15, that is, the pressure Pl in the rod chamber 21 a of the undulation cylinder 21, into a pressure detection signal (electric signal) and outputs it to the controller 30. The pressure reducing valve 18 operates so that the lower the starting pressure Pr as a command value, the smaller the opening degree and the higher the back pressure generated in the pipe line 16.

  The pressure reducing valve 18 is provided with a check valve 33 in parallel. The check valve 33 allows the flow of pressure oil in the direction from the check valve 32 toward the bottom chamber 21b of the hoisting cylinder 21 and blocks the flow of pressure oil in the opposite direction.

  The controller 30 includes a back pressure adjusting means 30c for controlling the pressure reducing valve 18 based on the detected value of the pressure Pl in the rod chamber 21a of the hoisting cylinder 21 indicated by the pressure detection signal from the pressure sensor 31. In the back pressure adjusting means 30c, the back pressure (pressure on the meter-out side) generated in the rod chamber 21a of the hoisting cylinder 21 is the pressure Pl (pressure on the meter-in side) in the rod chamber 21a of the hoisting cylinder 21. The pressure reducing valve 18 is controlled so that the pressure becomes equal to or higher than the starting pressure Pc of the counter balance valve 17. Further, the back pressure adjusting means 30c previously stores the correspondence between the detected value of the pressure Pl in the rod chamber 21a of the hoisting cylinder 21 and the current value supplied to the solenoid 18a of the pressure reducing valve 18 in the ROM of the controller 30. I remember it. Depending on the correspondence, the starting pressure Pr as the command value of the pressure reducing valve 18 is controlled as shown in FIG. Specifically, when the detected value of the pressure Pl in the rod chamber 21a of the hoisting cylinder 21 is 0 or less, the back pressure adjusting means 30c reduces the pressure by setting the starting pressure Pr of the pressure reducing valve 18 to the minimum starting pressure Prmin. In the state where the opening degree of the valve 18 is reduced and the detected value of the pressure Pl in the rod chamber 21a is higher than 0 and lower than the specified value Pls (> Pc), the starting pressure Pr of the pressure reducing valve 18 is a linear function. F is set to a value according to F, and as the pressure in the rod chamber 21a increases, the opening of the pressure reducing valve 18 is increased, and the detected value of the pressure Pl in the rod chamber 21a becomes the starting pressure Pls of the counter balance valve 17. In the above state, the starting pressure Pr of the pressure reducing valve 18 is set to the maximum starting pressure Prmax, the opening degree of the pressure reducing valve 18 is maximized, and the back pressure generated in the bottom chamber 21b of the hoisting cylinder 21 (meter out Pressure) is controlled so as the pressure Pl of the rod chamber 21a of hoisting cylinder 21 (pressure meter side) becomes higher than the starting pressure Pc of the counterbalance valve 17. In the state where the pressure Pl in the rod chamber 21a is equal to or higher than the starting pressure Pls, the pressure Pl in the rod chamber 21a is equal to or higher than the starting pressure Pc of the counter balance valve 17, so that the opening of the pressure reducing valve 18 is maximized. Thus, the back pressure control by the pressure reducing valve 18 is not performed.

  The control flow of the pressure reducing valve 18 by the back pressure adjusting means 30c is set as shown in FIG. That is, first, it is determined whether the command of the operation direction of the arm 5 by the operating device 19 is upward or downward, that is, whether the operating direction of the operating lever 19a is the D direction or the U direction (step S1). As a result of this determination, when the operation direction of the operation lever 19a is the D direction, a pressure detection signal from the pressure sensor 31 is input (step S2). Based on the detected value of the pressure Pl in the rod chamber 21a indicated by the pressure detection signal, a current is supplied to the solenoid 18a of the pressure reducing valve 18 to determine the starting pressure Pr of the pressure reducing valve 18 (step S3). As a result, as shown in FIG. 3, when the detected value of the pressure Pl in the rod chamber 21a is 0 or less, the starting pressure Pr of the pressure reducing valve 18 is determined as the minimum starting pressure Prmin, and the pressure in the rod chamber 21a. In a state where the detected value of Pl is higher than 0 and lower than the specified value Pls, the starting pressure Pr of the pressure reducing valve 18 is determined to be proportional to the pressure Pl in the rod chamber 21a, and the pressure Pl in the rod chamber 21a is determined to be the specified value Pls. In the above state, the starting pressure Pr of the pressure reducing valve 18 is determined to be the maximum starting pressure Prmax.

  If the result of determination in step S1 is that the operating direction of the operating lever 19a is the U direction, the back pressure adjusting means 30c determines the starting pressure Pr of the pressure reducing valve 18 as the maximum starting pressure Prmax (step S4). That is, the opening degree of the pressure reducing valve 18 is kept at the maximum, and when the operation direction of the operation lever 19a is the U direction, the back pressure control by the pressure Pl in the rod chamber 21a is not performed.

  The back pressure adjusting means 30c is set to repeat the control flow shown in FIG. 4 at a cycle of several milliseconds based on the CPU clock frequency. Thus, the back pressure in the bottom chamber 21b of the hoisting cylinder 21 is adjusted earlier than the response of the counter balance valve 17 to the fluctuation of the pressure Pl in the rod chamber 21a of the hoisting cylinder 21.

  The operation of the work machine 1 according to the present embodiment configured as described above will be described separately for (1) a case where the arm 5 is operated downward and (2) a case where the arm 5 is operated upward. .

(1) When the arm 5 is moved downward, the operating lever 19a of the operating device 19 is operated in the D direction from the neutral position. Thereby, in the controller 30, the operation direction control means 30 a supplies current to the solenoid 13 a of the direction control valve 13 based on the operation direction of the operation lever 19 a being the D direction, that is, based on the downward operation command of the arm 5. A current of value I1 is supplied, the valve position of the direction control valve 13 is switched to the first valve position b1, and the opening degree of the direction control valve 13 is set to OP1.

  In parallel with the control of the direction control valve 13, the discharge flow rate control means 30b of the controller 30 is based on the operation amount (tilt angle) in the D direction from the neutral position of the operation lever 19a of the operation device 19, that is, the arm 5 Based on the command of the speed of the downward operation, the inverter 11a is controlled so that the hydraulic pump 12 rotates at a rotational speed corresponding to the command.

  The oil discharged from the hydraulic pump 12 is supplied to the rod chamber 21a of the hoisting cylinder 21 through the directional control valve 13 in the state switched to the first valve position b1 and the conduit 15. Accordingly, when the pressure Pl of the rod chamber 21a of the hoisting cylinder 21 reaches Pc, the counter balance valve 17 opens against the return spring 17a using the pressure Pc as a pilot pressure.

  On the other hand, the back pressure adjusting means 30 c of the controller 30 sets the starting pressure Pr of the pressure reducing valve 18 according to the function F based on the detected value Pc of the pressure Pl in the rod chamber 21 a by the pressure sensor 31, and thereby the pressure reducing valve 18. Is determined. Accordingly, the pressure oil in the bottom chamber 21b of the hoisting cylinder 21 returns to the hydraulic oil tank 14 through the pressure reducing valve 18, the counter balance valve 17, and the direction control valve 13 in the state switched to the first valve position b1. As a result, the hoisting cylinder 21 contracts, and the arm 5 moves downward along with this.

  When the arm 5 moves downward in this way, the opening degree of the direction control valve 13 in the state switched to the first valve position b1 is related to the operation amount from the neutral position of the operating lever 19a of the operating device 19. However, since the predetermined opening degree OP1 is determined only based on the operation lever 19a being operated in the D direction from the neutral position, the hydraulic pump 12 enters the rod chamber 21a of the hoisting cylinder 21 through the direction control valve 13. The flow rate of the supplied pressure oil is the same as the discharge flow rate of the hydraulic pump 12. Further, the discharge flow rate of the hydraulic pump 12 is proportional to the rotational speed of the hydraulic pump 12, and the controller 30 controls the rotational speed of the electric motor 11 via the inverter 11a based on the operation amount of the operation lever 19a. To be determined. For these reasons, the relationship between the operation amount of the operation lever 19a in the D direction and the speed of the downward movement of the arm 5 is constant without being affected by the load acting on the hoisting cylinder 21.

  When the downward movement of the arm 5 is performed while the load is gripped by the gripping device 6, an inertial force acts on the load. Therefore, the inertial force causes the inside of the rod chamber 21 a of the hoisting cylinder 21 to move. The pressure Pl may be lower than Pls. In this case, the back pressure adjusting means 30c of the controller 30 performs the processing of “step S1 → step S2 → step S3” shown in FIG. 4, that is, the detection of the pressure Pl in the rod chamber 21a by the pressure sensor 31. Based on the value, the starting pressure Pr of the pressure reducing valve 18 is controlled according to the function F shown in FIG. 3, so that the opening degree of the pressure reducing valve 18 decreases as the pressure Pl in the rod chamber 21 a of the undulation cylinder 21 becomes lower than the specified value Pls. Make it smaller. As a result, the back pressure in the bottom chamber 21b of the hoisting cylinder 21 rises to a specified value Pls or more. Since the specified value Pls is set higher than the starting pressure Pc of the counter balance valve 17, the pressure Pl in the rod chamber 21a of the hoisting cylinder 21 is maintained to be equal to or higher than the starting pressure Pc.

  By the way, when the arm 5 is operating in the downward direction, if the inside of the rod chamber 21a of the hoisting cylinder 21 is lower than the starting pressure Pc of the counter balance valve 17, the counter balance valve 17 is closed. When the pressure oil is prevented from being discharged from the bottom chamber 21b of the hoisting cylinder 21, and then the pressure in the rod chamber 21a of the hoisting cylinder 21 rises above the starting pressure Pc of the counterbalance valve 17, the counter balance valve 17 is Open again. A response delay occurs at the timing when the counter balance valve 17 is closed with respect to the timing when the pressure in the rod chamber 21a of the hoisting cylinder 21 becomes lower than the starting pressure Pc of the counter balance valve 17, so the counter balance valve 17 is closed. The operation and the opening operation are alternately repeated, and accordingly, the back pressure in the bottom chamber 21b of the hoisting cylinder 21 is alternately increased and decreased alternately. As a result, a phenomenon that alternately stops and restarts contraction, that is, hunting occurs in the undulation cylinder 21, and vertical vibrations occur in the arm 5.

  On the other hand, as described above, the back pressure adjusting means 30c is configured to reduce the pressure reducing valve when the pressure Pl in the rod chamber 21a of the hoisting cylinder 21 has decreased to a specified value Pls that is higher than the starting pressure Pc of the counter balance valve 17. 18 is controlled to increase the pressure Pl in the rod chamber 21a of the hoisting cylinder 21 to a specified value Pls or more, that is, the pressure Pl in the rod chamber 21a of the hoisting cylinder 21 is increased to the starting pressure Pc. In order to maintain the above, the counter balance valve 17 is prevented from closing, and as a result, the hunting of the hoisting cylinder 21 is suppressed.

(2) When the arm 5 is moved upward, the operating lever 19a of the operating device 19 is operated in the U direction from the neutral position. Thereby, in the controller 30, the operation direction control means 30 a supplies current to the solenoid 13 b of the direction control valve 13 based on the operation direction of the operation lever 19 a being the U direction, that is, based on the upward operation command of the arm 5. A current of value I2 is supplied to switch the valve position of the direction control valve 13 to the second valve position b2, and the opening degree of the direction control valve 13 is set to OP2.

  In parallel with the control of the direction control valve 13, the discharge flow rate control means 30b of the controller 30 is based on the operation amount (tilt angle) in the U direction from the neutral position of the operation lever 19a of the operation device 19, that is, the arm 5 Based on the command of the speed of the upward operation, the inverter 11a is controlled so that the hydraulic pump 12 rotates at a rotational speed corresponding to the command.

  The oil discharged from the hydraulic pump 12 is supplied to the bottom chamber 21b of the hoisting cylinder 21 through the direction control valve 13 and the check valves 32 and 33 in the state switched to the second valve position b2, and in parallel therewith. The hydraulic oil in the rod chamber 21a of the hoisting cylinder 21 is returned to the hydraulic oil tank 14 through the pipe 15 and the directional control valve 13 in the state switched to the second valve position b2, whereby the hoisting cylinder 21 is The arm 5 moves upward along with the extension.

  When the arm 5 moves upward in this way, the opening degree of the direction control valve 13 in the state switched to the second valve position b2 is related to the operation amount from the neutral position of the operation lever 19a of the operation device 19. However, since the opening degree OP2 is determined only based on the operation lever 19a being operated in the U direction from the neutral position, it is supplied from the hydraulic pump 12 to the bottom chamber 21b of the hoisting cylinder 21 through the direction control valve 13. The flow rate of the pressure oil is the same as the discharge flow rate of the hydraulic pump 12. Further, the discharge flow rate of the hydraulic pump 12 is proportional to the rotational speed of the hydraulic pump 12, and the controller 30 controls the rotational speed of the electric motor 11 via the inverter 11a based on the operation amount of the operation lever 19a. To be determined. For these reasons, the relationship between the operation amount of the operation lever 19 a in the U direction and the speed of the operation of the arm 5 is constant without being affected by the load acting on the undulation cylinder 21.

  According to the working machine 1 according to the present embodiment, the following effects can be obtained.

  In the work machine 1 according to the present embodiment, the opening degree of the direction control valve 13 is determined when the operation direction control unit 30a switches the valve position of the direction control valve 13 to either the first valve position b1 or the second valve position b2. The discharge flow rate control means 30b controls the discharge flow rate of the hydraulic pump 12 based on the speed of operation of the arm 5 of the work device 4 instructed by the operation device 19, that is, the operation amount of the operation lever 19a. Therefore, the relationship between the operation amount of the operation lever 19 a and the speed of operation of the work device 4 can be made constant without being affected by the load acting on the undulation cylinder 21. As a result, it is possible to prevent the arm 5 of the working device 4 from moving upward or downward at a speed against the operator's will.

  When the work machine 1 according to the present embodiment operates the arm 5 of the work device 4 in the downward direction, the back pressure adjusting unit 30c uses the pressure Pl in the rod chamber 21a (meter-in side) of the hoisting cylinder 21 based on the pressure Pl. Since the pressure reducing valve 18 (pressure control valve) is controlled so that the back pressure that maintains the pressure Pl equal to or higher than the starting pressure Pc of the counter balance valve 17 is generated in the bottom chamber 21b (meter-out side) of the hoisting cylinder 21; It is possible to prevent the counter balance valve 17 from being alternately closed and opened, thereby reducing the hunting of the hoisting cylinder 21, that is, the vertical vibration of the arm 5.

  Although the hydraulic drive device 10 of the above-described embodiment drives the hydraulic pump 12 by transmitting the output of the electric motor 11, an internal combustion engine such as a diesel engine is used instead of the electric motor 11. Also good. In this case, the discharge flow rate of the hydraulic pump 12 is controlled by controlling the rotational speed of the internal combustion engine.

DESCRIPTION OF SYMBOLS 1 Work machine 4 Working device 5 Arm 6 Grasp device 10 Hydraulic drive device 11 Electric motor 11a Inverter 12 Hydraulic pump 13 Directional control valve 15 Pipe line 16 Pipe line 17 Counter balance valve 18 Pressure reducing valve 19 Operation device 19a Operation lever 21 Lifting cylinder 21a Rod chamber 21b Bottom chamber 30 Controller 30a Operation direction control means 30b Discharge flow rate control means 30c Back pressure adjustment means 31 Pressure sensor

Claims (3)

The hydraulic pump, a hydraulic cylinder that is driven by being supplied with oil discharged from the hydraulic pump, a working device that is driven by the hydraulic cylinder to raise and lower the load, and the work based on the operation direction and the operation amount of the operation member An operating device that commands each of the operation direction and speed of the device, and a control means that controls the flow direction and flow rate of the pressure oil supplied from the hydraulic pump to the hydraulic cylinder based on the command from the operating device; A counter balance valve that is provided in a pipe line on the meter-out side of the hydraulic cylinder when the operation device performs a downward operation, and operates using the pressure on the meter-in side of the hydraulic cylinder at that time as a pilot pressure. In work machines,
The control means is provided between the hydraulic pump and the hydraulic cylinder, and is provided with a neutral position for stopping the hydraulic cylinder, a first valve position for contracting the hydraulic cylinder, and a second valve for extending the hydraulic cylinder. A directional control valve switchable to a position;
The valve position of the directional control valve is switched to the first valve position or the second valve position based on a command for the direction of operation of the working device by the operating device, and the valve position of the directional control valve is set to the first valve position. , When switching to any of the second valve position, regardless of the operation amount of the operating device, regardless of the operation amount, the operation direction control means for controlling the opening of the direction control valve to a predetermined opening;
A work machine comprising: a discharge flow rate control unit configured to control a discharge flow rate of the hydraulic pump based on a command of an operation speed of the work device by the operation device. The work machine according to claim 1,
In the pipe line on the meter-out side, the pressure in the pipe line on the meter-in side is adjusted by controlling the back pressure generated in the pipe line on the meter-out side between the counter balance valve and the hydraulic cylinder. The pressure control valve is configured such that the back pressure of the meter-in side pipe line changes the pressure of the meter-in side pipe line based on the pressure of the meter-in side pipe line. A work machine controlled by a back pressure adjusting means so as to be equal to or higher than a starting pressure. The work machine according to claim 2 or 3,
The working device includes an arm that is driven by the hydraulic cylinder and moves in a vertical direction, and a gripping device that is provided at a tip portion of the arm and grips a load.

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