JP2010078035A - Hydraulic cylinder control circuit of utility machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize the pressure variation of a hydraulic circuit while keeping the operating speed of a hydraulic cylinder constant when hydraulic fluid is regenerated along with the telescopic movement of the hydraulic cylinder, in a hydraulic cylinder control circuit of a utility machine. <P>SOLUTION: In the hydraulic circuit engaging hydraulic fluid reproduction from one side oil chamber 38a of a hydraulic cylinder 38 to the other side oil chamber 38b, a pressure sensor 1 detecting a load pressure on a side of the one side oil chamber 38a is provided, and a solenoid proportional pressure reducing valve 2 is provided on a reproduction circuit L2 connecting between each of oil chambers 38a and 38b. Furthermore, in the opening control of the solenoid proportional pressure reducing valve 2, a differential pressure between a target pressure on a side of the one side oil chamber 38a and the load pressure is operated, and the opening is throttled more as the differential pressure becomes smaller, conversely the opening is released more as the differential pressure becomes greater. Thereby, the pressure of the one side oil chamber 38a is converged to the target pressure. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hydraulic cylinder control circuit for a work machine that supplies hydraulic oil that flows out during expansion and contraction of a hydraulic cylinder to the inflow side for recycling.

Some hydraulic circuits of work machines typified by hydraulic excavators are provided with a so-called regeneration circuit that supplies hydraulic oil that flows out during expansion and contraction of a hydraulic cylinder to the inflow side for recycling. Cited Document 1 describes a hydraulic circuit including a regeneration oil passage that regenerates return oil from the boom bottom (boom head) side to the boom rod side when the boom is lowered.
In this technology, a variable throttle valve is installed on the center bypass at the boom lowering position of the directional control valve (control valve) installed on the hydraulic oil supply path from the hydraulic oil pump to the hydraulic cylinder. Control is performed according to the boom bottom pressure and boom rod pressure. By such control, it is said that the fuel consumption can be improved by reducing the discharge flow rate on the hydraulic oil pump side when the hydraulic oil is regenerated.
JP-A-10-89317

  By the way, in the regeneration circuit as described above, for example, when the attachment attached to the tip of the arm is replaced, the bottom pressure of the hydraulic cylinder changes. Therefore, even if the same lever operation as before the replacement is performed, the operating speed of the hydraulic cylinder changes, and the operability also changes. Therefore, in order to keep the correspondence between the hydraulic cylinder lever operation amount and the operating speed constant in the conventional regeneration circuit, it is necessary to change the flow rate characteristic of the regeneration circuit when replacing the attachment, and such setting work is complicated. There is a problem of being.

  Moreover, not only the replacement of the attachment, but also the operating speed of the hydraulic cylinder may change due to load fluctuations acting on the front work machine. In this case, it is conceivable to control the operating speed of the hydraulic cylinder by keeping the amount of hydraulic oil regenerated from the hydraulic oil outflow side to the inflow side constant. However, such flow rate control on the regeneration circuit cannot control the pressure on the hydraulic oil outflow side provided by the load. Therefore, even if the operating speed of the hydraulic cylinder can be made constant regardless of the load fluctuation, the fluctuation of the working hydraulic pressure in the hydraulic cylinder cannot be suppressed. In particular, when the circuit pressure on the outflow side of hydraulic oil is used as the control pilot pressure of another hydraulic circuit, good controllability may not be obtained due to such pressure fluctuation.

  The present invention has been made in view of such problems, and can stabilize pressure fluctuations in the hydraulic circuit while maintaining the operating speed of the hydraulic cylinder constant during regeneration of the hydraulic oil accompanying the expansion and contraction operation of the hydraulic cylinder. An object of the present invention is to provide a hydraulic cylinder control circuit for a work machine.

  In order to achieve the above object, a hydraulic cylinder control circuit for a working machine according to a first aspect of the present invention is a hydraulic cylinder (for example, a boom cylinder or an arm cylinder) that is mounted on a hydraulic excavator and whose hydraulic fluid flow rate is controlled by a control valve. Is a hydraulic cylinder control circuit for supplying hydraulic oil discharged from one oil chamber to the other oil chamber on the drive side and regenerating it without extending through the control valve during expansion and contraction of the oil chamber, A pressure sensor for detecting a load pressure, a regeneration circuit connecting the one oil chamber and the other oil chamber, and an operation related to regeneration of the hydraulic cylinder (for example, a boom cylinder) interposed on the regeneration circuit When the boom lowering operation or arm-in operation with respect to the arm cylinder) is detected, and the regeneration circuit is shut off when the operation is not detected. A switching valve, an electromagnetic proportional pressure reducing valve that is interposed on the other oil chamber side of the switching valve in the regeneration circuit and is configured to be able to change the opening degree, and the electromagnetic proportional pressure reducing valve in the regeneration circuit And a pilot check valve that is interposed on the other oil chamber side and switches between a state in which hydraulic fluid flows in from the other oil chamber side by pilot control and a state in which the regeneration circuit is opened, and the regeneration circuit in the regeneration circuit. It is installed on a circuit connecting the downstream side of the pilot check valve and the control valve, and shuts off the state in which the circuit is opened by pilot control and the outflow of hydraulic oil from the other oil chamber side to the control valve side. A pilot switching valve for switching states, a pilot circuit for introducing the secondary pressure of the switching valve as a control pilot pressure into the pilot check valve and the pilot switching valve, A predetermined pressure setting means for setting a predetermined set pressure as a target pressure on the one oil chamber side when supplying hydraulic oil from the oil chamber side to the other oil chamber, and the load detected by the pressure sensor Control means for controlling the opening of the electromagnetic proportional pressure reducing valve in accordance with a pressure difference between the pressure and the predetermined set pressure set by the predetermined pressure setting means.

According to a second aspect of the hydraulic cylinder control circuit for a work machine of the present invention according to claim 2, in addition to the configuration according to claim 1, the control means throttles the opening of the electromagnetic proportional pressure reducing valve as the differential pressure decreases, Control is performed to open the opening of the electromagnetic proportional pressure reducing valve as the differential pressure increases.
According to a third aspect of the present invention, the hydraulic cylinder control circuit for the working machine according to the present invention supplies the hydraulic oil bleed-off via the center bypass of the control valve to the hydraulic pump. And a pilot throttle valve that is provided on the center bypass and that controls the hydraulic pressure of the negative control circuit according to the control pilot pressure introduced from the pilot circuit. .

  According to a fourth aspect of the present invention, there is provided a hydraulic cylinder control circuit for a working machine according to the present invention, wherein when a hydraulic cylinder mounted on a hydraulic excavator and whose hydraulic oil flow rate is controlled by a control valve is expanded or contracted, the hydraulic cylinder control circuit is controlled from one oil chamber without the control valve. A hydraulic cylinder control circuit for supplying and regenerating discharged hydraulic oil to the other oil chamber on the drive side, the pressure sensor for detecting the load pressure on the one oil chamber side, the one oil chamber, and the oil chamber A regeneration circuit connecting the other oil chamber, an electromagnetic proportional pressure reducing valve interposed on the regeneration circuit and capable of changing the opening, and from the one oil chamber side to the other oil chamber A predetermined pressure setting means for setting a predetermined set pressure as a target pressure on the one oil chamber side at the time of supplying hydraulic oil, the predetermined set pressure set by the predetermined pressure setting means and the pressure sensor Difference to calculate the differential pressure with the load pressure Opening control for reducing the opening degree of the electromagnetic proportional pressure reducing valve as the differential pressure calculated by the calculating means and the differential pressure calculating means decreases, and opening the opening degree of the electromagnetic proportional pressure reducing valve as the differential pressure increases And a means.

According to the hydraulic cylinder control circuit of the working machine of the present invention (Claim 1), by adjusting the flow rate of the regeneration circuit, the magnitude of the load pressure acting on one oil chamber of the hydraulic cylinder is set to a constant value (that is, in advance The pressure can be converged to a predetermined set pressure), and the hydraulic circuit can stabilize fluctuations in the operating hydraulic pressure while appropriately controlling the operating speed of the hydraulic cylinder.
In addition, according to the hydraulic cylinder control circuit (claim 2) of the working machine of the present invention, it is possible to perform speed control that is not easily affected by the load acting on the hydraulic cylinder. Even if the load pressure fluctuates or the load constantly increases or decreases due to the replacement of the attachment, the operating speed of the hydraulic cylinder can be made constant.

According to the hydraulic cylinder control circuit for a working machine of the present invention (Claim 3), when the load pressure on one oil chamber side of the hydraulic cylinder is high during the reduction operation of the hydraulic cylinder, the opening degree of the pilot throttle valve Is opened and the negative control pressure is set high, so that the discharge flow rate of the hydraulic pump can be reduced. Thereby, the energy loss of hydraulic fluid can be suppressed.
In addition, when the hydraulic excavator bucket is grounded and the hydraulic cylinder head pressure decreases, the pilot throttle valve opening is closed, so the negative control pressure decreases, and the hydraulic pump moves from the hydraulic cylinder to the rod side of the hydraulic cylinder. The hydraulic oil flow rate increases. Therefore, the hydraulic cylinder can be reduced at an appropriate speed even in a situation where the dead weight does not act.

  Further, according to the hydraulic cylinder control circuit of the working machine of the present invention (Claim 4), since the opening of the electromagnetic proportional pressure reducing valve is opened as the load pressure increases, the hydraulic pressure on one oil chamber side is kept constant. It becomes possible to do. Accordingly, the hydraulic cylinder can always be driven at a constant speed regardless of the fluctuation of the load pressure when the hydraulic oil is regenerated.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 3 are diagrams for explaining a hydraulic cylinder control circuit of a working machine according to an embodiment of the present invention, and FIG. 1 is a perspective view showing an overall configuration of a hydraulic excavator equipped with the hydraulic cylinder control circuit. FIGS. 2A and 2B are hydraulic circuit diagrams showing the overall configuration of the hydraulic cylinder control circuit, and FIG. 3 is a control block diagram of a controller related to the hydraulic cylinder control circuit.

[1. overall structure]
The hydraulic cylinder control circuit according to the present invention is applied to a hydraulic excavator 30 shown in FIG. The hydraulic excavator 30 includes a lower traveling body 31 equipped with a crawler-type traveling device, and an upper revolving body 32 that is rotatably mounted on the lower traveling body 31. A front working machine 34 such as a boom 35, an arm 36, a bucket 37, and a cab 41 on which an operator rides are provided on the front side of the upper swing body 32. An engine room 33 is provided behind the front work machine 34 and the cab 41.

The cab 41 is provided with operation levers for driving the front work machine 34 and a seat on which an operator is seated. In the engine room 33, an engine 12, which is a drive source of the hydraulic excavator 30, the engine-driven hydraulic pump 10, a cooling package, and the like are arranged.
A hydraulically driven boom cylinder 38 that swings the boom 35 in the vertical direction is interposed between the frame of the upper swing body 32 and the boom 35. The boom 35 is provided so as to be raised and lowered with respect to the upper swing body 32 by expansion and contraction of the boom cylinder 38. Similarly, the arm cylinder 39 and the bucket cylinder 40 shown in FIG. 1 are hydraulic actuators for moving the postures of the arm 36 and the bucket 37, respectively.

  This hydraulic cylinder control circuit is provided as a circuit for regenerating hydraulic oil when the boom cylinder 38 is reduced. That is, the hydraulic oil discharged from the head chamber 38a of the boom cylinder 38 during the boom lowering operation is supplied to the rod chamber 38b for reuse.

[2. Circuit configuration]
2A and 2B schematically show a hydraulic circuit to which the present hydraulic cylinder control circuit is applied. FIGS. 2A and 2B show a schematic configuration of a hydraulic circuit related to driving of the boom cylinder 38, and a description of the hydraulic circuit related to other actuators is omitted.

  FIG. 2A shows the operation lever 42 of the boom 35 and the remote control valve 13 connected thereto. A pilot pump 14 and a tank 15 are connected to the remote control valve 13, and a control pilot pressure corresponding to the operation amount and operation direction input to the operation lever 42 is generated as a secondary pressure. When the boom lowering operation is performed, the control pilot pressure is transmitted in the direction A in FIG. 2A, which is downstream of the lowering remote control valve 13a, and when the boom raising operation is performed, the downstream side of the raising remote control valve 13b. Thus, the control pilot pressure is transmitted in the direction of symbol B in FIG. These control pilot pressures are transmitted to symbols A and B in FIG. 2 (b), respectively.

  FIG. 2B shows a circuit relating to driving of the boom cylinder 38. This circuit includes a main hydraulic circuit L1, a regeneration circuit L2, a pilot circuit L3, and a negative control circuit L4. In addition, a controller 20 is provided as an electronic control device related to the opening degree control of the electromagnetic proportional pressure reducing valve 3 interposed on the regeneration circuit L2.

[2-1. Main hydraulic circuit]
The main hydraulic circuit L1 is a hydraulic circuit through which hydraulic oil that extends and retracts the boom cylinder 38 flows. On the main hydraulic circuit L1, as shown in FIG. 2B, a hydraulic pump 10, a control valve 8, a boom cylinder 38 and a tank 15 are interposed.

The hydraulic pump 10 driven by the engine 12 is a variable displacement pump provided with a regulator 11. The regulator 11 is a known pump displacement variable means, and the hydraulic pump 10 is configured to decrease the discharge flow rate of the hydraulic pump 10 as the introduced negative control pressure increases, and to increase the discharge flow rate as the negative control pressure decreases. The swash plate control is implemented.
Inside the boom cylinder 38, a head chamber 38a and a rod chamber 38b are formed via a piston. A piston rod is fixed to the piston, and the upper end of the piston rod is pivotally supported by the boom 35. On the other hand, the lower end of the boom cylinder 38 is pivotally supported by the frame of the upper swing body 32.

The control valve 8 is a valve that adjusts the flow rate and flow direction of the hydraulic oil to the boom cylinder 38, and variably controls the flow rate and flow direction of the hydraulic oil by switching the flow control spool (stem) position to three positions S1 to S3. It is configured as a possible electromagnetic flow control valve.
For example, when no operation lever 42 is operated, the spool is controlled to the S2 position, and the hydraulic oil returns to the tank 15 via the center bypass L5. On the other hand, when the boom lowering operation is performed, a secondary pressure is generated downstream of the lower-side remote control valve 13a, the spool is gradually switched to the S1 position, and hydraulic oil is supplied to the rod chamber 38b side of the boom cylinder 38. . When the boom raising operation is performed, a secondary pressure is generated downstream of the raising-side remote control valve 13b, the spool is gradually switched to the S3 position, and hydraulic oil is supplied to the head chamber 38a side of the boom cylinder 38. . A pressure sensor 1a (pressure switch) is interposed downstream of the lower side remote control valve 13a. The pressure sensor 1 a detects the presence or absence of a boom lowering operation and outputs the information to the controller 20.

Of the two circuits L1a and L1b between the control valve 8 and the boom cylinder 38 in the main hydraulic circuit L1, the fall prevention valve 7 is disposed on the circuit L1a that connects the control valve 8 and the head chamber 38a. Has been.
The fall prevention valve 7 is a valve provided with a check valve mechanism for containing hydraulic oil in the head chamber 38a so that the boom 35 does not fall due to its own weight. As shown in FIG. 2 (b), when the control pilot pressure in the direction of symbol A in the remote control valve 13 is input, the circuit L1a is opened at an opening degree corresponding to the magnitude of the pressure, and the control pilot pressure is received. In the absence, it functions as a check valve that blocks only the flow of hydraulic oil from the head chamber 38a to the control valve 8. Thereby, the boom 35 is prevented from dropping when the boom is raised and the boom is stopped.

At the downstream side of the fall prevention valve 7 in the circuit L1a, a branch point BP is formed that communicates with the regeneration circuit L2, the relief circuit L6, and the head chamber 38a. The pressure sensor 1 and the relief valve 16 are provided on the relief circuit L6. The pressure sensor 1 is a cylinder head pressure P _H, i.e., detects the hydraulic pressure of the head chamber 38a side of the boom cylinder 38, and outputs to the controller 20.
A pilot switching valve 5 is interposed on a circuit L1b that connects the control valve 8 and the rod chamber 38b. The operation of the pilot switching valve 5 will be described later.

[2-2. Negative control circuit]
On the center bypass L5 of the control valve 8, a pilot throttle valve 6 and a negative control relief valve 9 are provided. Further, a negative control circuit L4 is branched between the pilot throttle valve 6 and the negative control relief valve 9. Has been.

  The negative control relief valve 9 is a relief valve for taking out the negative control pressure related to the so-called negative control in the regulator 11 of the hydraulic pump 10, and functions to maintain the operating hydraulic pressure of the center bypass L5. The pilot throttle valve 6 is a throttle valve for changing the working hydraulic pressure of the negative control circuit L4 by pilot control. As shown in FIG. 2 (b), when the control pilot pressure is not introduced, the opening of the pilot throttle valve 6 is throttled to a preset size and opens when the control pilot pressure is introduced. The degree is to be released. A pilot circuit L3, which will be described later, is connected to the pilot port of the pilot throttle valve 6, and the operating hydraulic pressure downstream of the switching valve 2 in the regeneration circuit L2, which will be described later, is introduced as a control pilot pressure.

[2-3. Regenerative circuit, pilot circuit]
The regeneration circuit L2 connects the downstream side (the rod chamber 38b side) of the pilot switching valve 5 on the circuit L1b and the branch point BP, and the hydraulic fluid flowing out from the head chamber 38a of the boom cylinder 38 is directed toward the rod chamber 38b. It is a circuit to supply. On the regeneration circuit L2, as shown in FIG. 2B, a switching valve 2, an electromagnetic proportional pressure reducing valve 3, and a pilot check valve 4 are interposed.

  The switching valve 2 is a valve that controls the flow rate of the hydraulic oil in the regeneration direction via the regeneration circuit L2. As shown in FIG. 2 (b), when the secondary pressure of the remote control valve 13 is input as a control pilot pressure, the circuit is opened at an opening corresponding to the magnitude of the pressure, and no control pilot pressure is received. Then, it functions as a check valve that blocks only the flow of hydraulic oil from the head chamber 38a to the rod chamber 38b. Thereby, at the time of boom lowering operation, it is possible to increase the regeneration flow rate as the operation amount increases.

  A pilot circuit L3 is branched from the downstream side of the switching valve 2 on the regeneration circuit L2. The pilot circuit L3 is a circuit for introducing control pilot pressure to the pilot check valve 4, the pilot switching valve 5, and the pilot throttle valve 6. The pilot circuit L3 functions as a flag transmission circuit indicating whether or not the hydraulic oil is regenerated through the regeneration circuit L2.

Solenoid proportional pressure reducing valve 3 is a proportional pressure reducing valve controlled by the controller 20 is controlled so that the predetermined pressure cylinder head pressure P _H by adjusting the hydraulic fluid flow circulating in the regeneration circuit L2 is set in advance It is a valve. Specific control contents will be described later.
The pilot check valve 4 is a check valve that can turn on or off the check valve mechanism by pilot control. Like a general check valve, the pilot check valve 4 is connected to the head chamber 38a side from the rod chamber 38b side in the regeneration circuit L2. This is a valve that can be switched between a state that interrupts the flow of hydraulic oil to the state and a state that allows reverse flow and permits the flow of hydraulic oil in both directions. A pilot circuit L3 is connected to the pilot port of the pilot check valve 4, and only when the hydraulic oil is regenerated through the regeneration circuit L2, bidirectional hydraulic fluid distribution is permitted.

  The pilot switching valve 5 opens the circuit L1b in a state where the control pilot pressure from the pilot circuit L3 is not introduced. When the control pilot pressure is introduced, the pilot switching valve 5 moves from the rod chamber 38b side to the control valve 8 side on the circuit L1b. It is a valve that functions as a check valve that shuts off hydraulic fluid flow. As a result, when the hydraulic oil is regenerated through the regeneration circuit L2, bleed-off of the hydraulic oil through the circuit L1b is prohibited.

  The pilot throttle valve 6 throttles the negative control circuit L4 to a preset opening when the control pilot pressure of the pilot circuit L3 is not introduced, and opens according to the magnitude when the control pilot pressure is introduced. This valve opens the negative control circuit L4. When the hydraulic oil is regenerated through the regeneration circuit L2, the negative control pressure introduced into the regulator 11 is set higher than that during non-regeneration, thereby suppressing the flow rate of hydraulic oil discharged from the hydraulic pump 10.

[3. Controller configuration]
As shown in FIG. 2B, the hydraulic excavator 30 is provided with a controller (control means) 20 for controlling the opening degree of the electromagnetic proportional pressure reducing valve 3 of the regeneration circuit L2. The controller 20 is an electronic control device configured by a microcomputer, and is provided as an LSI device in which a known microprocessor, ROM, RAM, and the like are integrated. As shown in FIG. 3, the controller 20 includes a predetermined pressure setter (predetermined pressure setting means) 21, a subtracter (differential pressure calculation means) 22, a PI control calculator 23 (one of opening degree control means), and an electromagnetic proportional pressure reduction. A valve driver 24 (one of opening control means) is provided. Note that these configurations may be provided as an electronic circuit or software.

Controller 20, when the boom lowering operation by the pressure sensor 1a is detected to control the solenoid proportional pressure reducing valve 3 based on the cylinder head pressure P _H detected by the pressure sensor 1. On the other hand, control is not performed when boom lowering operation is not detected. The detection information of the pressure sensor 1a is used as a trigger for starting the control described in detail below.
Predetermined pressure setter 21 is for setting a predetermined set pressure P _P as the target pressure of the cylinder head pressure P _H during the working oil reproduction from the head chamber 38a side to the rod chamber 38b side. In this embodiment, it is set to about 20 [MPa]. A hydraulic cylinder control circuit of the present invention, during reproduction of the hydraulic fluid through the reproduction circuit L2, not only controls the hydraulic fluid flow rate constant, so as to converge the cylinder head pressure P _H to a predetermined set pressure P _P To control. The predetermined set pressure P _P set here is input to the addition side of the subtractor 22.

As described above, the controller 20, the cylinder head pressure P _H detected by the pressure sensor 1 is inputted. Cylinder head pressure P _H is inputted to the subtraction side of the subtracter 22. Meanwhile subtractor 22 outputs a differential pressure obtained by subtracting the cylinder head pressure P _H from the input predetermined set pressure P _P to PI control calculation unit 23.
PI control calculation unit 23 converges the differential pressure input from the subtractor 22 to zero degree of opening of the electromagnetic proportional pressure reducing valve 3 (i.e., is to converge the cylinder head pressure P _H to a predetermined set pressure P _P) for This is calculated and output to the electromagnetic proportional pressure reducing valve driver 24. The control amount output here includes a component set in proportion to the differential pressure (P operation component) and a component set in proportion to the integral of the differential pressure (I operation component). ing.

For example, when the cylinder head pressure P _H does not reach the predetermined set pressure P _P , the differential pressure output from the subtractor 22 is large (P _P -P _H becomes a positive value), so the electromagnetic proportional pressure reducing valve The regeneration flow rate is reduced by reducing the opening of 3. When Accordingly cylinder head pressure P _H rises, so that the differential pressure gradually approaches zero. Further, when the cylinder head pressure P _H exceeds the predetermined set pressure P _P , the differential pressure is small (P _P -P _H becomes a negative value), so the opening degree of the electromagnetic proportional pressure reducing valve 3 is increased. Increase regeneration flow. When Accordingly cylinder head pressure P _H is decreased, so that the differential pressure gradually approaches zero.
The electromagnetic proportional pressure reducing valve driver 24 converts the control amount input from the PI control calculator 23 into an opening command value of the electromagnetic proportional pressure reducing valve 3 and outputs it to the electromagnetic proportional pressure reducing valve 3.

[4. Action]
[4-1. Boom raising operation]
When the operation lever 42 is operated in the boom raising direction, the control pilot pressure is transmitted in the direction B in FIG. 2A, and the flow control spool of the control valve 8 is switched to the S3 position. The hydraulic oil discharged from the hydraulic pump 10 circulates to the circuit L1a side through the control valve 8, and is supplied to the head chamber 38a of the boom cylinder 38 through the fall prevention valve 7. At this time, the switching valve 2 functions as a check valve because it does not receive the control pilot pressure, and the hydraulic oil flow to the rod chamber 38b is shut off. Therefore, the hydraulic oil from the hydraulic pump 10 does not flow into the regeneration circuit L2. In addition, since the boom lowering operation is not detected in the pressure sensor 1a, the electromagnetic proportional pressure reducing valve 3 is not controlled.

  Further, the hydraulic oil in the rod chamber 38 b flows through the circuit L 1 b through the pilot switching valve 5 and returns to the tank 15 through the control valve 8. At this time, since the pilot check valve 4 is not opened, the return oil from the rod chamber 38b does not flow into the regeneration circuit L2. Therefore, the boom cylinder 38 extends according to the operation amount of the operation lever 42.

[4-2. Boom lowering operation]
On the other hand, when the operating lever 42 is operated in the boom lowering direction, the secondary pressure of the lower remote control valve 13a is transmitted in the direction A in FIG. 2A, and the flow control spool of the control valve 8 is switched to the S1 position. It is done. Further, the secondary pressure of the remote control valve 13 is also introduced into the switching valve 2 and the fall prevention valve 7 for switching. The pressure sensor 1 a detects a boom lowering operation and transmits the information to the controller 20.

  The hydraulic oil discharged from the hydraulic pump 10 flows to the circuit L1b side via the control valve 8, and is supplied to the rod chamber 38b of the boom cylinder 38 via the pilot switching valve 5. The hydraulic fluid in the head chamber 38a is diverted to the control valve 8 side, the regeneration circuit L2, and the relief circuit L6 via the branch point BP. At this time, since the fall prevention valve 7 opens the circuit L1a, the hydraulic fluid flowing to the control valve 8 side returns to the tank 15.

Since the switching valve 2 is opened at an opening corresponding to the secondary pressure of the remote control valve 13, the flow rate of the hydraulic oil flowing through the regeneration circuit L2 increases as the operation amount of the operation lever 42 increases. Further, the downstream pressure of the switching valve 2 is also transmitted to the pilot circuit L3, and the pilot check valve 4, the pilot switching valve 5 and the pilot throttle valve 6 are switched.
As a result, in the circuit L1b, the pilot switching valve 5 prevents back flow to the control valve 8 side. Further, the hydraulic oil in the regeneration circuit L2 is supplied to the rod chamber 38b through the electromagnetic proportional pressure reducing valve 3 and the pilot check valve 4, and the hydraulic oil is regenerated.

The controller 20, based on the cylinder head pressure P _H detected by the pressure sensor 1 of the relief circuit L6, as the pressure difference obtained by subtracting the cylinder head pressure P _H from a predetermined set pressure P _P is zero, the solenoid proportional The opening degree of the pressure reducing valve 3 is controlled. For example, when the cylinder head pressure P _H is higher than the predetermined set pressure P _P , the regeneration flow rate is increased by increasing the opening degree of the electromagnetic proportional pressure reducing valve 3. As a result, the hydraulic pressure on the rod chamber 38b side increases. That is, the controller 20 increases the hydraulic pressure in the rod chamber 38b by causing the hydraulic oil in the rod chamber 38b to share the load that was only borne by the hydraulic oil in the head chamber 38a of the boom cylinder 38, and the cylinder head pressure P _H is kept constant.

If the cylinder head pressure P _H is controlled to be constant, with hydraulic oil in the head chamber 38a is no longer relieved from the relief valve 16, the flow rate of the return oil in the anti-drop valve 7 also, as long as that does not change the operation amount of the operation lever 42 It becomes constant. As a result, the operating speed of the boom cylinder 38 is less affected by the load acting on the boom cylinder 38.
Further, when the hydraulic oil is flowing through the regeneration circuit L2, the control pilot pressure is transmitted to the pilot throttle valve 6 via the pilot circuit L3. Thereby, the center bypass L5 is opened, and the negative control pressure of the negative control circuit L4 increases. Therefore, the discharge flow rate of the hydraulic pump 10 is suppressed by the negative control in the regulator 11. The opening degree of the pilot throttle valve 6 is released as the operating hydraulic pressure of the pilot circuit L3 is higher, that is, as the operating hydraulic pressure flowing through the regeneration circuit L2 is higher, so the main hydraulic circuit is higher as the cylinder head pressure is higher. The flow rate of hydraulic oil flowing through L1 decreases.

[5. effect]
Thus, according to the hydraulic cylinder control circuit of the present working machine, since the larger the cylinder head pressure P _H is the opening degree of the solenoid proportional pressure reducing valve 3 is opened, the load pressure acting in the head chamber 38a of the hydraulic cylinder 38 (Cylinder head pressure P _H ) can be converged to a constant value, and fluctuations in hydraulic pressure can be stabilized. Further Thus, regardless of the variation in the cylinder head pressure P _H during reproduction of the hydraulic oil can always drive the boom cylinder 38 at a constant speed.

Further, since the cylinder head pressure P _H is constant, it is possible to make constant the flow rate of the return oil through a fall prevention valve 7 with respect to the operation amount of the operation lever 42, the boom by regeneration of hydraulic oil cylinder 38 It is possible to prevent a sudden change in the operating speed.
It is also possible to perform speed control that is not easily affected by the load acting on the boom cylinder 38. For example, even if the work load fluctuates during the boom lowering operation, the operating speed of the boom cylinder 38 can be made constant. Alternatively, even if the load constantly increases or decreases due to the replacement of the attachment, the operating speed of the boom cylinder 38 does not change, and good operability can be obtained.

Further, by controlling the pilot throttle valve 6 of the center bypass L5 via the pilot circuit L3, the flow rate of hydraulic oil discharged from the hydraulic pump 10 can be appropriately controlled. For example, since the negative control pressure is set high when the cylinder head pressure P _H was high when the cylinder lowering operation, it can reduce the delivery rate of the hydraulic pump 10 to suppress the energy loss of the hydraulic oil.

On the other hand, the cylinder head pressure P _H bucket 37 of the hydraulic excavator 30 is set to the ground state becomes low, even when it is not possible to reproduce the hydraulic fluid through the reproduction circuit L2, the pilot throttle valve 6 of the center bypass L5 is down Since the negative control pressure is set low, the discharge flow rate of the hydraulic pump 10 can be increased, and the hydraulic oil can be supplied to the rod side 38b of the boom cylinder 38 to contract the boom cylinder 38. In this way, the hydraulic cylinder can be reduced at an appropriate speed even in a situation where the dead weight does not act.

[6. Others]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, the hydraulic oil regeneration circuit L2 in the boom cylinder 38 is illustrated, but it may be configured as a regeneration circuit for the arm cylinder 39. In this case, the configuration of the present invention may be applied to a hydraulic circuit that regenerates hydraulic oil from the rod chamber of the arm cylinder 39 to the head chamber during the arm-in operation.

  In the above-described embodiment, the present invention is applied to the hydraulic circuit of the excavator 30. However, the application target of the present invention is not limited to this, and various operations such as a bulldozer, a wheel loader, and a hydraulic crane are performed. It can be applied to the hydraulic circuit of a machine.

1 is a perspective view showing an overall configuration of a hydraulic excavator equipped with a hydraulic cylinder control circuit for a work machine according to an embodiment of the present invention. It is a figure which shows the whole structure of the hydraulic cylinder control circuit of the working machine which concerns on one Embodiment of this invention, (a) is a hydraulic circuit diagram which concerns on an operation lever, (b) is a hydraulic circuit diagram which concerns on a boom cylinder. It is a control block diagram of the controller which concerns on the hydraulic cylinder control circuit of the working machine which concerns on one Embodiment of this invention.

Explanation of symbols

1 Pressure sensor 1a Pressure sensor (pressure switch)
DESCRIPTION OF SYMBOLS 2 Switching valve 3 Electromagnetic proportional pressure reducing valve 4 Pilot check valve 5 Pilot switching valve 6 Pilot throttle valve 7 Fall prevention valve 8 Control valve 9 Negative control relief valve 10 Hydraulic pump 11 Regulator 12 Engine 13 Remote control valve 13a Lowering side remote control valve 13b Raising side Remote control valve 14 Pilot pump 15 Tank 16 Relief valve 20 Controller (control means)
21 Predetermined pressure setter (predetermined pressure setting means)
22 Subtractor (Differential pressure calculation means)
23 PI control calculator (opening control means)
24 Electromagnetic proportional pressure reducing valve driver (opening control means)
DESCRIPTION OF SYMBOLS 30 Hydraulic excavator 31 Lower traveling body 32 Upper turning body 33 Engine room 34 Front work machine 35 Boom 36 Arm 37 Bucket 38 Boom cylinder 38a Head chamber 38b Rod chamber 39 Arm cylinder 40 Bucket cylinder 41 Cab 42 Operation lever L1 Main hydraulic circuit L2 Regeneration Circuit L3 Pilot circuit L4 Negative control circuit L5 Center bypass L6 Relief circuit BP Branch point

Claims (4)

When a hydraulic cylinder mounted on a hydraulic excavator and whose hydraulic oil flow rate is controlled by a control valve is expanded and contracted, hydraulic oil discharged from one oil chamber is supplied to the other oil chamber on the drive side without passing through the control valve. A hydraulic cylinder control circuit to be regenerated,
A pressure sensor for detecting the load pressure on the one oil chamber side;
A regeneration circuit connecting the one oil chamber and the other oil chamber;
A switching valve interposed on the regeneration circuit that opens the regeneration circuit when an operation relating to regeneration of the hydraulic cylinder is detected and shuts off the regeneration circuit when the operation is not detected;
An electromagnetic proportional pressure reducing valve that is interposed on the other oil chamber side of the switching valve in the regeneration circuit and is configured to be able to change the opening;
Switched between the state in which the hydraulic oil from the other oil chamber side is shut off and the state in which the regeneration circuit is opened by pilot control. A pilot check valve;
The regeneration circuit is provided on a circuit connecting the downstream side of the pilot check valve and the control valve, and the circuit is opened by pilot control and the operation from the other oil chamber side to the control valve side A pilot switching valve for switching the state of blocking oil spill,
A pilot circuit for introducing the secondary pressure of the switching valve as a control pilot pressure into the pilot check valve and the pilot switching valve;
A predetermined pressure setting means for setting a predetermined set pressure as a target pressure on the one oil chamber side when hydraulic oil is supplied from the one oil chamber side to the other oil chamber;
Control means for controlling the opening of the electromagnetic proportional pressure reducing valve in accordance with a differential pressure between the load pressure detected by the pressure sensor and the predetermined set pressure set by the predetermined pressure setting means. A hydraulic cylinder control circuit for a work machine. The control means performs control to reduce the opening degree of the electromagnetic proportional pressure reducing valve as the differential pressure is smaller, and to open the opening degree of the electromagnetic proportional pressure reducing valve as the differential pressure is larger. Item 2. A hydraulic cylinder control circuit for a work machine according to Item 1. A negative control circuit for guiding hydraulic oil bleed-off through the center bypass of the control valve to the hydraulic pump;
2. A pilot throttle valve provided on the center bypass and further controlling an operating oil pressure of the negative control circuit according to the control pilot pressure introduced from the pilot circuit. 2. A hydraulic cylinder control circuit for a work machine according to 2. When a hydraulic cylinder mounted on a hydraulic excavator and whose hydraulic oil flow rate is controlled by a control valve is expanded and contracted, hydraulic oil discharged from one oil chamber is supplied to the other oil chamber on the drive side without passing through the control valve. A hydraulic cylinder control circuit to be regenerated,
A pressure sensor for detecting the load pressure on the one oil chamber side;
A regeneration circuit connecting the one oil chamber and the other oil chamber;
An electromagnetic proportional pressure reducing valve interposed on the regeneration circuit and configured to change the opening;
A predetermined pressure setting means for setting a predetermined set pressure as a target pressure on the one oil chamber side when hydraulic oil is supplied from the one oil chamber side to the other oil chamber;
Differential pressure calculating means for calculating a differential pressure between the predetermined set pressure set by the predetermined pressure setting means and the load pressure detected by the pressure sensor;
Opening degree control means for narrowing the opening degree of the electromagnetic proportional pressure reducing valve as the differential pressure calculated by the differential pressure calculating means decreases, and opening the opening degree of the electromagnetic proportional pressure reducing valve as the differential pressure increases. A hydraulic cylinder control circuit for a work machine.

Images