JP4953378B2 - Hydraulic control system for construction machinery - Google Patents

Description

  The present invention belongs to the technical field of a hydraulic control system in a construction machine provided with a hydraulic cylinder for moving a heavy object up and down.

Generally, in construction machines such as hydraulic excavators, various hydraulic actuators such as hydraulic cylinders for moving a heavy object up and down, control valves for performing oil supply / discharge control on these hydraulic actuators based on operation of an operation tool, hydraulic supply sources For example, when the hydraulic actuator is a boom cylinder for moving a boom of a hydraulic excavator up and down, the boom cylinder is configured to supply oil to a head side oil chamber that is a weight holding side oil chamber and The boom is lifted by the oil discharge from the rod side oil chamber, which is the anti-weight holding side oil chamber, and the boom is moved upward, and the boom is reduced by the oil supply to the rod side oil chamber and the oil discharge from the head side oil chamber. Is configured to move down.
By the way, when the boom is lowered, the weight applied to the boom (total weight of the front work machine) acts as a force for reducing the boom cylinder, so the pressure in the head side oil chamber is the pressure in the rod side oil chamber. Higher pressure. Therefore, conventionally, there has been provided a regeneration oil passage that supplies oil discharged from the head side oil chamber to the rod side oil chamber as regeneration oil when the boom is lowered, and the pressure in the head side oil chamber is higher than the pressure in the rod side oil chamber. It is known that the regenerated oil is supplied to the rod side oil chamber in addition to the pressure oil supplied from the hydraulic pump during high pressure.
Further, in the case where the above-described regeneration oil passage is provided, a technique in which the control valve is set to the neutral position when the boom is lowered (for example, see Patent Document 1), or when the boom is lowered. A technique (for example, see Patent Document 2) provided with a switching valve that adjusts the supply flow rate from the hydraulic pump to the rod-side oil chamber is known. In these cases, when the boom is moved down in the air, only the regenerated oil from the head-side oil chamber is supplied to the rod-side oil chamber, and pressure oil is not supplied from the hydraulic pump. Thus, the discharge flow rate of the hydraulic pump can be reduced.
JP-A-9-132927 JP 2005-256895 A

By the way, in many construction machines such as a hydraulic excavator, the engine is controlled so as to have a target rotational speed set by an engine rotational speed setting tool such as an accelerator dial, and a hydraulic pump using the engine as a power source is The maximum flow rate is changed according to the target rotational speed, that is, the pump flow rate is increased when the engine speed is high, and the pump flow rate is decreased when the engine speed is low. . And when the operator wants to increase the work speed or to perform high-load work, the target rotation speed is set high to increase the engine output, while the operator wants to work at low speed or to perform low-load work. When performing, the target output speed is set low so that the engine output is reduced to reduce fuel consumption.
However, in Patent Documents 1 and 2, although the discharge flow rate of the hydraulic pump is reduced when the boom is moving in the air, the engine target rotational speed remains the value set by the engine rotational speed setting tool. If the target speed is set high, engine output is wasted. Therefore, it is proposed that the engine speed is controlled to decrease when the boom moves in the air. However, when the engine speed decreases due to the control, for example, when a dump cylinder is dumped, a stick cylinder or the like is used. In the case where the boom is moved downward while the other hydraulic actuators are mainly operated, the operation speed of the other hydraulic actuators is lowered, resulting in a problem of poor work efficiency.
Further, as described above, in Patent Documents 1 and 2, when the boom is moved down in the air, only the regenerated oil is supplied to the rod side oil chamber and no pressure oil is supplied from the hydraulic pump. The downward movement speed is not affected by the increase or decrease in the pump flow rate associated with the target rotation speed set by the engine rotation speed setting tool. For this reason, even if the operator sets the target rotation speed with the engine rotation speed setting tool in consideration of the work speed, the work content, etc., the lowering speed of the boom does not change, and the workability is inferior. There are problems to be solved by the present invention.

The present invention has been created in view of the above-described circumstances and has been created for the purpose of solving these problems. The invention of claim 1 is directed to a heavy load that can be moved up and down. A hydraulic cylinder that is extended and retracted to move up by oil supply and oil discharge from the anti-weight holding side oil chamber, and to move down by oil supply to the anti-weight holding side oil chamber and oil discharge from the weight holding side oil chamber; A regeneration oil passage that supplies oil discharged from the weight holding side oil chamber to the anti-weight holding side oil chamber when the heavy object moves down, a hydraulic actuator other than the hydraulic cylinder, the hydraulic cylinder, and the other hydraulic actuator In a hydraulic control system for a construction machine comprising an engine that is a power source of a hydraulic pump that supplies pressure oil to the engine and an engine speed setting tool for setting a target speed of the engine, the hydraulic control system includes a weight Thing The operation judgment downward movement of the weight thereof is equal to or a driven work that is performed in conjunction with the operation of other hydraulic actuators at the time of movement, set by the engine revolution speed setting device during downward movement of the heavy A control device for performing engine speed reduction control for reducing the engine speed to the engine speed for reduction control when the set target speed is higher than a preset engine speed for reduction control; In the construction machine, the number reduction control is executed when it is determined by the operation determination that the downward movement of the heavy object is not a subordinate operation, but is not executed when it is determined that the subordinate operation is a subordinate operation. It is a hydraulic control system.
In the invention of claim 2, a regeneration control valve whose opening amount is adjusted based on a control command from the control device is arranged in the regeneration oil passage, and the control device is set by an engine speed setting tool. characterized in that the regeneration amount adjustment control to adjust the opening degree of the reproduction control valve so as to correspond to the set target rotational speed of the height from the weight holding side oil chamber and decreasing the regeneration amount of the counter-weight holding-side oil chamber The hydraulic control system for a construction machine according to claim 1.
According to a third aspect of the present invention, the control device is a slave operation in which the downward movement of the heavy load is performed in conjunction with the operation of another hydraulic actuator when the hydraulic cylinder operating tool is finely operated to the downward movement side. The hydraulic control system for a construction machine according to claim 1 or 2, characterized in that

According to the first aspect of the present invention, when the heavy object is moved downwardly, if the downward movement of the heavy object is not a slave operation performed in conjunction with the operation of another hydraulic actuator, the engine speed is decreased. The engine speed reduction control that lowers the engine speed to less than the engine speed is executed, which can greatly contribute to the reduction of fuel consumption. On the other hand, when the downward movement of the heavy object is a subordinate operation, the engine speed reduction control is not executed. Thus, it is possible to contribute to the improvement of work efficiency without lowering the operating speed of other hydraulic actuators performed in conjunction with the downward movement of the heavy object.
According to the invention of claim 2, the amount of reclaimed oil supplied from the weight holding side oil chamber to the anti-weight holding side oil chamber via the regeneration control valve is the set target rotation set by the engine speed setting tool. The speed increases or decreases in accordance with the level of the number, and the downward movement speed of the heavy object can be changed in accordance with the set target rotational speed, so that the workability is excellent.
According to the invention of claim 3, it is possible to easily and inexpensively determine whether or not the downward movement of the heavy object is a slave operation.

  Next, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a hydraulic excavator. The hydraulic excavator 1 is attached to a crawler type lower traveling body 2, an upper revolving body 3 that is pivotably supported by the lower traveling body 2, and the upper revolving body 3. The front work machine 4 further includes a boom 5 whose base end is supported by the upper swing body 3 so as to be movable up and down, and swings back and forth at the front end of the boom 5. The hydraulic excavator 1 includes left and right traveling motors, turning motors, and boom cylinders (not shown). The stick 6 is freely supported and includes a bucket 7 attached to the tip of the stick 6. 8, the basic configuration such as the provision of various hydraulic actuators such as a stick cylinder 9 and a bucket cylinder 10 is the same as the conventional one. In addition, in FIG. 1, 1a is a cab which becomes an operator's cab.

  The hydraulic excavator 1 is provided with a hydraulic control circuit including the various hydraulic actuators, a hydraulic pump, various valves, an oil tank, and the like. FIG. 2 shows the hydraulic control circuit. 11 and 12 are variable displacement type first and second hydraulic pumps driven by the engine E as a power source, 11a and 12a are capacity variable means of the first and second hydraulic pumps 11 and 12, and 13 is a predetermined pressure. 14 is an oil tank, 15 and 16 are left and right traveling motors, 17 is a turning motor, 8 is a boom cylinder, 9 is a stick cylinder, and 10 is a bucket cylinder.

  Here, the boom cylinder 8 corresponds to the hydraulic cylinder of the present invention, and is extended by oil supply to the head side oil chamber 8a and oil discharge from the rod side oil chamber 8b to move the boom 5 upward. In addition, the boom 5 is moved downward by contracting by supplying oil to the rod side oil chamber 8b and discharging oil from the head side oil chamber 8a, but the head side oil chamber 8a has a weight. The weight of the front work machine 4 as a whole is held and corresponds to the weight holding side oil chamber of the present invention, and the rod side oil chamber 8b corresponds to the anti-weight holding side oil chamber of the present invention.

  Further, reference numeral 18 denotes a first boom control valve connected to the discharge line A of the first hydraulic pump 11, and the first boom control valve 18 includes pilot ports 18a and 18b on the upper moving side and the lower moving side. And a spool valve in which the opening amounts of supply and discharge valve passages 18c to 18f, which will be described later, are adjusted in accordance with the level of pilot pressure input to the pilot ports 18a and 18b. In other words, the first boom control valve 18 is located at the neutral position N and does not supply or discharge oil to the boom cylinder 8 when no pilot pressure is input to the pilot ports 18a and 18b. When the pilot pressure is input to the side pilot port 18 a, the supply valve path 18 c is switched to the upper movement side position X to supply the discharge oil of the first hydraulic pump 11 to the head side oil chamber 8 a of the boom cylinder 8. The discharge valve path 18d that opens and allows the oil discharged from the rod side oil chamber 8b to flow into the oil tank 14 is opened. Further, the first boom control valve 18 is switched to the lower movement side position Y when the pilot pressure is inputted to the lower movement side pilot port 18b, and the discharged oil of the first hydraulic pump 11 is roded through the throttle. The supply valve path 18e supplied to the side oil chamber 8b is opened, and the discharge valve path 18f for discharging the oil discharged from the head side oil chamber 8a to the oil tank 14 through the throttle is opened.

  On the other hand, 19 is a second boom control valve connected to the discharge line B of the second hydraulic pump 12, and the second boom control valve 19 is connected to the pilot ports 19a, 19b on the upper and lower moving sides. And a spool valve whose opening and closing amounts of a supply valve passage 19c and a regeneration valve passage 19d, which will be described later, are adjusted in accordance with the level of pilot pressure input to the pilot ports 19a and 19b. In other words, the second boom control valve 19 is located at the neutral position N and does not supply or discharge oil to the boom cylinder 8 when no pilot pressure is input to the pilot ports 19a and 19b. When the pilot pressure is input to the side pilot port 19a, the supply valve path 19c is switched to the upward movement side position X to supply the discharge oil of the second hydraulic pump 12 to the head side oil chamber 8a of the boom cylinder 8. It is supposed to open. Further, the second boom control valve 19 is configured to be switched to the lower movement side position Y when a pilot pressure is inputted to the lower movement side pilot port 19b and to open a regeneration valve path 19d described later. Yes.

  Here, the regeneration valve passage 19d of the second boom control valve 19 is a valve passage for opening and closing the regeneration oil passage C from the head side oil chamber 8a of the boom cylinder 8 to the rod side oil chamber 8b. When the regeneration valve passage 19d is opened, the head side oil chamber 8a is passed through the regeneration oil passage C while the pressure in the head side oil chamber 8a of the boom cylinder 8 is higher than the pressure in the rod side oil chamber 8b. The oil discharged from the cylinder can be supplied to the rod-side oil chamber 8b as reclaimed oil. The amount of regeneration from the head-side oil chamber 8a to the rod-side oil chamber 8b depends on the head-side oil chamber 8a and the rod-side oil. The pressure increases and decreases according to the pressure difference with the chamber 8b and the opening amount of the regeneration valve passage 19d. In the present embodiment, the second boom control valve 19 having the regeneration valve path 19d corresponds to the regeneration control valve of the present invention.

  In FIG. 2, 20, 21, 22, 23, and 24 are the left and right traveling motors 15 and 16, the left and right traveling motors 15 and 16, the turning motor 17, the stick cylinder 9, and the left and right traveling control for controlling the bucket cylinder 10, respectively. In this embodiment, the right-hand drive control valve 21 and the bucket control valve 24 are connected to the discharge line A of the first hydraulic pump 11, and The left traveling control valve 20, the turning control valve 22, and the stick control valve 23 are arranged in the discharge line B of the second hydraulic pump 12. Thus, the right traveling motor 16 and the bucket cylinder 10 are supplied with pressure oil from the first hydraulic pump 11, and the left traveling motor 15, the turning motor 17, and the stick cylinder 9 are pressurized from the second hydraulic pump 12. Oil is supplied.

  The first and second hydraulic pumps 11 and 12 are variable displacement type as described above, and the capacity variable means 11a and 12a of the first and second hydraulic pumps 11 and 12 are center bypass. Negative control flow rate control based on the passage flow rate of the oil passage SB, constant horsepower control for controlling the pump flow rate so that the horsepower supplied from the engine E is constant, and a pump based on a control signal corresponding to the work load and the engine speed Perform output increase / decrease control. Since the flow rate control is a well-known technique, a detailed description is omitted, but the first and second hydraulic pumps 11 and 12 have a maximum pump flow rate when the engine speed is high, and the engine speed is high. The maximum pump flow rate is controlled to decrease as the value decreases.

  Reference numeral 25 denotes a pilot valve that outputs a pilot pressure based on an operation of a boom operation lever (corresponding to the hydraulic cylinder operation tool of the present invention) 26, and includes an upper movement side pilot valve 25X and a lower movement side pilot valve. 25Y. When the boom operation lever 26 is not operated, pilot pressure is not output from both the upper and lower pilot valves 25X and 25Y, but the boom operation lever 26 is operated to the upper movement side. As a result, pilot pressure is output from the upper moving side pilot valve 25X to the upper moving side pilot ports 18a and 19a of the first and second boom control valves 18 and 19, and thereby, for the first and second booms. The control valves 18 and 19 are configured to switch to the upward movement position X. Further, when the boom operation lever 26 is operated to the downward movement side, the pilot pressure is output from the downward movement side pilot valve 25Y to the lower movement side pilot ports 18b and 19b of the first and second boom control valves 18 and 19. Thus, the first and second boom control valves 18 and 19 are configured to be switched to the lower movement side position Y. In this case, the pilot pressure output from the pilot valve 25 is increased or decreased in accordance with the operation amount of the boom operation lever 26.

  Further, 27 is an electromagnetic proportional pressure control valve arranged in a pilot oil passage from the lower moving pilot valve 25Y to the lower moving pilot port 19b of the second boom control valve 19, and the electromagnetic proportional pressure control valve 27 reduces the pilot pressure output from the lower moving pilot valve 25Y based on a control signal from the control device 28, which will be described later, and outputs it to the lower moving pilot port 19b of the second boom control valve 19. It is configured.

  The control device 28 is configured by using a microcomputer or the like, which inputs signals from a pressure sensor 29 and an accelerator dial 30 described later, and will be described later based on the input signals. A control command is output to the electromagnetic proportional pressure control valve 27 and the engine E to perform operation determination, engine speed reduction control, and regeneration amount adjustment control.

  Here, the pressure sensor 29 is a pressure sensor that detects the pilot pressure P output from the lower pilot valve 25Y in accordance with the operation of the boom operation lever 26.

  The accelerator dial 30 (corresponding to the engine speed setting tool of the present invention) is a setting tool provided in the cab 1a for the operator to set the target engine speed of the engine E. The target rotational speed is set for each of the 30 dial values. Hereinafter, the target rotational speed of the engine E set by the accelerator dial 30 is referred to as a set target rotational speed Ns.

Next, operation determination, engine speed reduction control, and regeneration amount adjustment control performed by the control device 28 will be described based on the flowchart of FIG.
First, the control device 28 reads signals from the pressure sensor 29 and the accelerator dial 30 (step S1).

  Next, the controller 28 reduces the pilot pressure output from the lower pilot valve 25Y to the electromagnetic proportional pressure control valve 27 in accordance with the set target rotational speed Ns set by the accelerator dial 30. A control command is output (step S2).

  That is, in the process of step S2, the control device 28, when the set target rotational speed Ns is the maximum (the dial value of the accelerator dial 30 is the maximum) with respect to the electromagnetic proportional pressure control valve 27, the downward movement side pilot valve 25Y. The control command is output so as to output the pilot pressure output from the second boom control valve 19 to the lower pilot side port 19b without reducing the pressure, while the primary side pressure decreases as the set target rotational speed Ns decreases. The secondary side pressure P2 (output from the electromagnetic proportional pressure control valve 27 and output from the lower proportional pilot valve 25Y and input to the electromagnetic proportional pressure control valve 27) and the second boom control valve 19 The ratio (P2 / P1) of the pilot pressure input to the lower moving side pilot port 19b becomes smaller. Sea urchin, and outputs a control command. Accordingly, regeneration amount adjustment control is executed to increase or decrease the opening amount of the regeneration valve passage 19d of the second boom control valve 19 in accordance with the level of the set target rotational speed Ns set by the accelerator dial 30. Thus, the regeneration passage 19d of the second boom control valve 19 has a maximum opening degree when the set target rotational speed Ns is maximum if the boom operation lever 26 is fully operated. The opening amount is controlled so as to decrease as the set target rotational speed Ns decreases. However, in the state where the opening amount of the regeneration valve passage 19d is maximum, the engine speed is controlled by engine speed reduction control as will be described later. Even when the engine speed Nd decreases, the regeneration amount is set so that the boom can be moved down at a sufficiently high speed. As described above, since the pilot pressure output from the lower pilot valve 25Y increases or decreases according to the operation amount of the boom operation lever 26, if the set target rotational speed Ns is the same, the regeneration valve path The opening amount 19d is adjusted to increase or decrease in accordance with the operation amount of the boom operation lever 26.

  Next, the control device 28 determines the operation of the boom 5 based on the input signal from the pressure sensor 29 (step S3).

The determination in step S3 will be described based on the control block diagram of FIG. 4. First, the value of the pilot pressure P output from the lower moving pilot valve 25Y is input from the pressure sensor 29 to the determination table 31. In the determination table 31, when the pilot pressure P is less than the preset first threshold value Px (P <Px), the boom operation lever 26 is not operated or is operated downward. Is determined to be a fine operation, and an OFF signal is output. On the other hand, if the pilot pressure P is equal to or higher than the first threshold value Px (P ≧ Px), it is determined that the boom lowering operation is performed beyond the fine operation To output an ON signal. The first threshold value Px is a value that is set to determine the downward operation amount of the boom operation lever 26, and is set based on actual work data or the like. The pilot pressure P is set to be slightly different (Pxu> Pxd) when the pilot pressure P increases (Pxu) and when the pilot pressure P decreases (Pxd).
When the OFF signal is output from the determination table 31, that is, the control device 28 is determined to be a fine operation even if the boom operation lever 26 is not operated downward or is operated. In such a case, it is determined that the boom lowering is a subordinate operation performed in conjunction with another hydraulic actuator such as the stick 9 even when the boom is not moving downward or when the boom is moving downward. On the other hand, when the ON signal is output from the determination table 31, that is, when it is determined that the boom lower side operation is performed more than the fine operation, and the ON signal lasts for a predetermined time S set in advance, It is determined that the lowering of the boom is not a slave operation, that is, the main operation is being performed. When the output time of the ON signal is less than the predetermined time S, it is determined that the operation is a slave operation.

  If it is determined in step S3 that the lowering of the boom is being performed as the main operation, the control device 28 is continuously set by the accelerator dial 30 based on the input signal from the accelerator dial 30. It is determined whether or not the set target rotational speed Ns is higher than the engine speed Nd for lowering control described later (Ns> Nd?) (Step S4).

  Here, the engine speed Nd for lowering control is an engine speed set in advance in order to lower the engine speed when the boom is moved in order to achieve low fuel consumption.

  If “YES” in the determination in step S4, that is, if it is determined that the set target rotational speed Ns set by the accelerator dial 30 is higher than the engine speed Nd for decrease control (Ns> Nd), the control device 28 A control command is output to E so that the engine speed Nd for lowering control becomes the target speed of the engine E (step S5).

  On the other hand, if “NO” in the determination in step S4, that is, if it is determined that the set target rotational speed Ns set by the accelerator dial 30 is equal to or lower than the engine speed Nd for lowering control (Ns ≦ Nd), the control device 28 Then, a control command is output to the engine E so that the set target rotational speed Ns set by the accelerator dial 30 is set as the target rotational speed of the engine E (step S6).

That is, when the lowering of the boom is performed as the main operation, the rotational speed of the engine E is controlled to decrease by the process of step S5 when the set target rotational speed Ns is higher than the engine speed Nd for lowering control. On the other hand, when the set target engine speed Ns is equal to or lower than the lower engine speed Nd, the engine speed is controlled to be the set target engine speed Ns by the process of step S6. As a result, the engine speed reduction control for reducing the engine speed of the engine E to be equal to or lower than the engine speed Nd for reduction control is executed.
After step S5 or step S6, the process returns to step S1.

  On the other hand, if it is determined in step S3 that the boom is not moved downward or the boom is moved downward, the process proceeds to step S6 described above. In other words, a control command is output from the control device 28 to the engine E so that the set target rotational speed Ns set by the accelerator dial 30 is set to the target rotational speed of the engine E, and therefore, when the boom is not lowered or Even when the boom is moving downward, when the boom moving downward is a slave operation, the engine speed reduction control described above is not executed.

  In the present embodiment configured as described, when the boom operation lever 26 is operated to the downward movement side, the pilot pressure is output from the downward movement side pilot valve 25Y along with the operation, and the pilot pressure is The first boom control valve 18 is supplied to the lower movement side pilot port 18b to switch the first boom control valve 18 to the lower movement side position Y and to the second via the electromagnetic proportional pressure control valve 27. The second control valve 19 is switched to the lower movement side position Y by being supplied to the lower movement side pilot port 19 b of the boom control valve 19. Thus, when the boom 5 is moved downward, the oil discharged from the head side oil chamber 8a of the boom cylinder 8 passes through the regeneration valve passage 19d of the second boom control valve 19 and is regenerated as rod side oil. The excess oil is supplied to the chamber 8b and discharged to the oil tank 14 via the first boom control valve 18, while the rod-side oil chamber 8b passes through the first boom control valve 18. The oil discharged from the first hydraulic pump 11 and the regenerated oil from the head-side oil chamber 8a are combined and supplied. In this case, depending on the operation judgment performed by the control device 28, the boom 5 is a subordinate operation performed in conjunction with the operation of another hydraulic actuator such as the stick cylinder 9, and it is determined that the subordinate operation is not a subordinate operation, that is, a main operation. In the case where the engine speed is reduced, the engine speed reduction control is executed to reduce the engine speed to a predetermined lower control engine speed Nd or less. The engine speed reduction control is not executed.

  As a result, when the boom 5 is moved downward, when the downward movement of the boom 5 is the main operation, the engine speed is reduced to a lower control engine speed Nd or less, which can greatly contribute to a reduction in fuel consumption. . On the other hand, when the downward movement of the boom 5 is a slave operation performed in conjunction with the operation of another hydraulic actuator such as the stick cylinder 9, the engine speed becomes the set target speed Ns set by the accelerator dial 30. Thus, when other hydraulic actuators such as the stick cylinder 9 are mainly operated in conjunction with the downward movement of the boom, for example, when dumping in dumping work, the other The operating speed of the hydraulic actuator can be reduced and the work efficiency can be improved.

  Further, in this case, the amount of opening of the regeneration valve passage 19d of the second boom control valve 19 corresponds to the level of the set target rotational speed Ns set by the accelerator dial 30 by the regeneration amount adjustment control performed by the control device 28. Thus, it will be adjusted up or down. As a result, the amount of regenerated oil supplied from the head side oil chamber 8a to the rod side oil chamber 8b via the regenerating valve passage 19b increases or decreases in accordance with the level of the set target rotational speed Ns. Thus, the boom lowering speed changes in accordance with the level of the set target rotational speed Ns arbitrarily set by the operator using the accelerator dial 30, and the workability is excellent. Moreover, as described above, the opening amount of the regeneration valve passage 19b when the set target rotational speed Ns is the maximum is sufficiently high even if the engine rotational speed has decreased to the engine speed Nd for control of decrease. Since the amount of regeneration is set such that the boom can be moved downward, it is possible to easily handle high-speed work.

  In this case, the boom operation lever 26 is finely operated to determine whether or not the downward movement of the boom 5 is a slave operation performed in conjunction with the operation of another hydraulic actuator such as the stick cylinder 9. In many cases, the operation is a subordinate operation. Therefore, the boom operation lever 26 is determined to be a subordinate operation when it is finely operated. Further, since the fact that the boom operation lever 26 is finely operated is determined based on the pilot pressure P output from the lower moving pilot valve 25Y, it is determined whether or not it is a slave operation. As a sensor necessary for the above, only the pressure sensor 29 for detecting the pilot pressure is sufficient, which is advantageous in terms of cost.

  Needless to say, the present invention is not limited to the above-described embodiment, and in the above-described embodiment, the second boom control valve 19 is discharged from the second hydraulic pump 12 when the boom 5 is moved upward. Is controlled as a control valve for supplying the oil to the head-side oil chamber 8a of the boom cylinder 8, while the boom 5 is moved downward, the regeneration control for supplying the oil discharged from the head-side oil chamber 8a to the rod-side oil chamber 8b. It is configured to function as a valve, and therefore, one valve has two functions, which can contribute to the reduction of the number of parts. Of course, the present invention can be implemented even if the control valve for supplying the oil discharged from the pump 12 to the boom cylinder 8 is provided separately.

  In the above embodiment, negative control flow rate control is adopted as flow rate control of the hydraulic pump based on the operation tool operation amount, but not limited thereto, positive control flow rate control or load sensing control flow rate control. Even if is adopted, the present invention can be implemented.

  Further, the control device 28 can be configured as in the second embodiment shown in the control block diagram of FIG. 5 when determining whether or not the downward movement of the boom 5 is a slave operation. In the second embodiment, similarly to the above-described embodiment, it is determined that the operation on the lower side of the boom operation lever 26 is a follow operation when it is a fine operation. Is determined based on the discharge pressure PP of the first hydraulic pump 11 that supplies pressure oil to the boom cylinder 8 when the boom 5 is moved downward.

That is, in this second embodiment, in determining whether or not the downward movement of the boom 5 is a slave operation, the control device 28 first turns ON / OFF from the pressure switch for detecting the downward movement operation of the boom. An OFF signal is input, and the ON / OFF signal is output to the AND gate 32.
Here, the pressure switch for detecting the boom lowering operation is a pressure switch for detecting whether or not the boom operating lever 26 is operated to the lower side, and although not shown, the pressure in the above-described embodiment. Instead of the switch 29, it is provided. The boom downward operation detection pressure switch is switched from OFF to ON based on the pilot pressure being output from the downward movement side pilot valve 25Y in accordance with the downward movement side operation of the boom operation lever 26. The threshold value for switching from OFF to ON is set smaller than the first threshold value Px in the above-described embodiment (for example, to move the spools of the first and second boom control valves 18 and 19). The minimum pressure required) is set to be switched ON even when the boom operation lever 26 is finely operated.

Further, the control device 28 inputs the discharge pressure PP of the first hydraulic pump 11 input from the first hydraulic pump pressure sensor into the determination table 33.
Here, the pressure sensor for the first hydraulic pump is a pressure sensor for detecting the discharge pressure PP of the first hydraulic pump 11 and is connected to the discharge line A of the first hydraulic pump 11 (not shown). Yes.

  The determination table 33 indicates that the boom operation lever 26 is not operated or is operated when the discharge pressure PP of the first hydraulic pump 11 is less than a preset second threshold value PPy (PP <PPy). However, if the discharge pressure PP of the first hydraulic pump 11 is greater than or equal to the second threshold value PPy (PP ≧ PPy), the boom operation greater than the fine operation is performed. It is determined that the signal is ON and an ON signal is output. The second threshold value PPy is a value set to determine the operation amount of the boom operation lever 26 from the load applied to the first hydraulic pump 11, and is set based on actual work data or the like. The ON signal output from the determination table 33 is input to the AND gate 32 when the ON signal continues for a predetermined time S set in advance. On the other hand, when the OFF signal is output from the determination table 33 or when the output time of the ON signal output from the determination table 33 is less than the predetermined time S, the OFF signal is input to the AND gate 32.

  When the ON signal is input to the AND gate 32 from the boom lowering operation detection pressure switch and the ON signal is input from the determination table 33, the control device 28 performs the boom lowering operation. When the boom operation is performed more than the fine operation, it is determined that the lowering of the boom is not a subordinate operation, that is, is performed as a main operation. On the other hand, when an OFF signal is input to the AND gate 32 from at least one of the boom lowering operation detection pressure switch or the determination table 33, that is, the boom lowering operation is not performed or the boom lowering operation is performed. However, in the case of fine operation, it is determined that the boom is not moved downward, or that the boom downward movement is a slave operation performed in conjunction with another hydraulic actuator such as the stick 9. It is configured as follows.

  Thus, in the second embodiment, the lower operation of the boom operation lever 26 is controlled based on the discharge pressure PP of the first hydraulic pump 11 that supplies pressure oil to the boom cylinder 8 when the boom 5 is moved downward. In this case, it is possible to determine whether or not the downward movement of the boom 5 is a subordinate operation. The necessary pressure switch for detecting the lowering operation of the boom and the pressure sensor for the first hydraulic pump are devices usually provided in the hydraulic control circuit of the hydraulic excavator 1 for valve control and pump control. There is no need to add, which can greatly contribute to cost reduction.

  In each of the above embodiments, it is configured to determine whether or not the boom lowering is a slave operation based on the detection value of the pressure switch or the pressure sensor. However, the operation direction and operation of the boom operation lever are determined. An operation detection unit that electrically detects the amount may be provided, and the above determination may be made based on a detection signal from the operation detection unit. Furthermore, with respect to other hydraulic actuator operating tools such as stick cylinders, by providing an operation detecting means for electrically detecting the operation direction and the operation amount, it is possible to determine whether or not the boom downward movement is a slave operation. It can be done more accurately.

  Furthermore, the present invention is not limited to the hydraulic control system of a hydraulic excavator, and can of course be applied to a hydraulic control system of various construction machines provided with a hydraulic cylinder for moving a heavy object up and down.

It is a side view of a hydraulic excavator. It is a hydraulic control circuit diagram of a hydraulic excavator. It is a flowchart figure which shows the control procedure of a control apparatus. It is a control block diagram which shows the control procedure of operation | movement judgment. It is a control block diagram which shows the control procedure of the operation | movement judgment in 2nd embodiment.

Explanation of symbols

8 Boom cylinder 8a Head side oil chamber 8b Rod side oil chamber 9 Stick cylinder 11 First hydraulic pump 12 Second hydraulic pump 19 Second boom control valve 26 Boom operation lever 28 Control device 30 Accel dial C Regeneration oil path E engine

Claims (3)

A heavy object that can move up and down is moved upward by supplying oil to the weight holding side oil chamber and discharging oil from the anti weight holding side oil chamber, and from the oil supply to the anti weight holding side oil chamber and from the weight holding side oil chamber. A hydraulic cylinder that expands and contracts in order to move it down with oil discharge
A regeneration oil passage for supplying oil discharged from the weight holding side oil chamber to the anti-weight holding side oil chamber when the heavy object is moved down;
A hydraulic actuator other than the hydraulic cylinder;
An engine that is a power source of a hydraulic pump that supplies pressure oil to the hydraulic cylinder and other hydraulic actuators;
In a hydraulic control system for a construction machine comprising an engine speed setting tool for setting a target speed of the engine,
In the hydraulic control system,
An operation determination for determining whether or not the downward movement of the heavy object is a subordinate operation performed in conjunction with the operation of another hydraulic actuator;
When the set target rotational speed set by the engine rotational speed setting tool is higher than the preset lowering engine rotational speed when the heavy object is moved downward, the engine rotational speed is decreased to the lower controlling engine rotational speed. While providing a control device that performs the number reduction control
The engine speed reduction control is executed when it is determined by the operation determination that the downward movement of the heavy object is not a subordinate operation, but is not executed when it is determined that the subordinate operation is a subordinate operation. Hydraulic control system for construction machinery. While arranging the regeneration control valve whose opening degree is adjusted based on the control command from the control device in the regeneration oil passage,
The controller is
To adjust the opening degree of the reproduction control valve so as to increase or decrease the regeneration amount of the counter-weight holding-side oil chamber from the weight holding side oil chambers in response to the set target rotational speed of the height set by the engine rotational speed setting instrument The hydraulic control system for a construction machine according to claim 1, wherein regeneration amount adjustment control is performed.   The control device determines that the downward movement of the heavy load is a slave operation performed in conjunction with the operation of another hydraulic actuator when the hydraulic cylinder operating tool is finely operated to the downward movement side. The hydraulic control system for a construction machine according to claim 1 or 2.

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