JP5150529B2 - Flow control valve with pilot switching mechanism - Google Patents

Description

  According to the present invention, the hydraulic pressure output from the operation valve is input to the pilot port according to the operation amount of the first operating means for driving the hydraulic actuator, and flows to the hydraulic actuator according to the pilot pressure of the pilot port. The present invention relates to a flow control valve with a pilot switching mechanism that changes the flow rate of pressure oil.

  FIG. 1 is a right side view showing a known excavator 10. An excavator 10 that is a construction machine includes a boom 13, an arm 14, and a bucket 11. Each of the boom 13, the arm 14, and the bucket 11 is provided with hydraulic cylinders 20, 21, and 22. Each hydraulic cylinder 20, 21, 22 is provided with a directional flow control valve that switches the direction and flow rate of the pressure oil flowing from the hydraulic pump to the hydraulic cylinders 20, 21, 22 according to the operation of the operation levers 31, 46. Yes. The driver operates the operation levers 31 and 46 to switch the direction of the pressure oil flowing through the hydraulic cylinders to expand and contract the hydraulic cylinders 20, 21 and 22, and move each of the boom 13, the arm 14, and the bucket 11.

  The hydraulic cylinders 20, 21, and 22 are supplied with the pressure oil discharged from one hydraulic pump and divided. When the boom 13 and the bucket 11 are moved simultaneously, it is necessary to move the boom 13 with priority. Therefore, the hydraulic circuit that moves the bucket 11 and the boom 13 is configured such that the boom 11 moves preferentially when the boom 13 and the bucket 11 are moved simultaneously.

  FIG. 5A is a circuit diagram showing a part of the hydraulic circuit 1A of the first prior art. The hydraulic circuit 1 </ b> A and a hydraulic circuit 1 </ b> B, which will be described later, relate to the bucket hydraulic cylinder 21. The hydraulic circuit 1 </ b> A includes a bucket hydraulic cylinder 21, a flow direction control valve 3 </ b> A, and a flow rate adjustment valve 4. The flow rate adjusting valve 4 is interposed in a pump passage 5 that connects a hydraulic pump (not shown) and the flow direction control valve 3A. The flow rate adjusting valve 4 receives a hydraulic switching command signal that is output when the boom hydraulic cylinder 20 is driven. The flow rate adjusting valve 4 limits the flow rate of the pressure oil flowing through the pump passage 5 when a switching command signal is input. The restricted amount of pressure oil is sent to the boom hydraulic cylinder. As a result, the flow rate of the pressure oil flowing through the boom hydraulic cylinder 20 is greater than that of the bucket hydraulic cylinder 21, and the boom hydraulic cylinder 20 is preferentially driven (see, for example, Patent Document 1).

  FIG. 5B is a circuit diagram showing a part of the hydraulic circuit 1B of the second prior art. The hydraulic circuit 1B includes a bucket hydraulic cylinder 21 and a flow direction control valve 3B. The flow direction control valve 3B is configured such that the spool 3a moves in accordance with an operation lever operated by the driver, and the direction and flow rate of the pressure oil flowing through the bucket hydraulic cylinder 21 changes according to the position of the spool 3a. Yes. The flow direction control valve 3B is provided with a regulating member 6 for regulating the stroke of the spool 3a. The restricting member 6 restricts the stroke of the spool 3a when a hydraulic switching command signal output when the boom hydraulic cylinder 20 is driven is input. As a result, the flow rate of the pressure oil flowing through the bucket hydraulic cylinder 21 is limited, and the flow rate of the pressure oil flowing through the boom hydraulic cylinder 20 is larger than that of the bucket hydraulic cylinder 21 as in the hydraulic circuit 1A. Therefore, the boom hydraulic cylinder 20 is driven preferentially.

Japanese Patent No. 2987279

  In the excavator 10, the flow rate of the pressure oil flowing through the bucket hydraulic cylinder 21 changes according to the operation amount of the operation lever, and the movable speed of the bucket 11 changes due to the change in the flow rate. The hydraulic circuits 1A and 1B are both configured to limit the upper limit amount of the flow rate of the pressure oil flowing through the bucket hydraulic cylinder 21 when the switching command signal is input to the flow rate adjusting valve 4 and the regulating member 6, respectively. ing. Therefore, after the switching command signal is input, if the operation amount of the operation lever exceeds a certain amount, the movable speed of the bucket does not change even if the operation amount increases, and the response according to the operation amount of the operation lever 31 is achieved. You will not be able to get.

  Further, the hydraulic circuit 1A needs to have the flow rate adjusting valve 4 interposed in the pump passage 5, and the hydraulic circuit 1B needs to be provided with a regulating member 6 so that the stroke of the spool 3a is regulated. Therefore, the number of parts provided in the valve block constituting the flow direction switching valves 3A, 3B increases, and the structure of the valve block becomes complicated. In addition, when multiple hydraulic cylinders are provided, all hydraulic cylinders 20, 21, and 22 that are not driven preferentially must be provided on the flow rate adjusting valve 4 or the regulating member 6. This makes the valve block structure more complex. Turn into.

  An object of the present invention is to switch a pilot pressure input to a flow rate control valve for controlling a flow rate of pressure oil supplied to a hydraulic actuator in accordance with a switching command signal, and also in accordance with an operation amount of an operating means after switching. To provide a flow control valve with a pilot switching mechanism capable of changing the drive speed of a hydraulic actuator in accordance with the operation amount of an operation means.

  Another object of the present invention is to provide a flow control valve with a pilot switching mechanism capable of switching the pilot pressure in accordance with a command signal by connecting the third oil passage to the pilot passage of the flow control valve. It is.

  According to the flow control valve with a pilot switching mechanism of the present invention, the hydraulic pressure output from the operation valve is input to the pilot port in accordance with the operation amount of the first operation means for operating the hydraulic actuator, and the pilot pressure of the pilot port is A flow control valve with a pilot switching mechanism that changes the flow rate of the pressure oil flowing to the hydraulic actuator according to the pressure, and outputs the hydraulic pressure from the pilot hydraulic pump to a pressure corresponding to the hydraulic pressure from the operation valve The pressure reducing valve and a pilot pressure switching valve that switches the hydraulic pressure input to the pilot port to the hydraulic pressure output from the pressure reducing valve when the switching command signal is output from the switching command unit.

  According to the present invention, the hydraulic pressure input to the pilot port is switched from the hydraulic pressure flowing from the operation valve to the hydraulic pressure flowing from the pressure reducing valve in response to the output of the switching command signal from the switching command section. Thereby, when the switching command signal is output, the pressure oil decompressed by the pressure reducing valve is input to the pilot port, so that the pilot pressure is switched according to the presence or absence of the switching command signal.

  In the present invention, the hydraulic pressure output from the pressure reducing valve is reduced to a pressure corresponding to the hydraulic pressure from the operation valve. Therefore, the relationship between the operation amount of the operating means and the pilot pressure can be switched in two stages depending on the presence / absence of the switching command signal, and even after the switching command signal is output, the pilot pressure remains in the operation of the first operating means. It is configured to change according to the quantity. Therefore, even after the switching command signal is output, the pressure oil having a flow rate corresponding to the operation amount of the first operation means is caused to flow through the hydraulic actuator, and the hydraulic actuator is driven at a driving speed corresponding to the operation amount of the first operation means. Can be driven.

  In the present invention, a first oil passage connected to the pilot hydraulic pump, a second oil passage connected to the operation valve, a third oil passage connected to the pilot port, and the switching A directional switching valve that causes pressure oil from a pilot hydraulic pump to flow to the first oil passage in response to the switching command signal output from the command portion, and the pressure reducing valve is configured to be the first oil passage. And the pressure of the first oil passage is reduced according to the oil pressure of the second oil passage, and the pilot switching valve causes the first oil passage to flow when the pressure oil flows into the first oil passage. An oil passage is connected to the third oil passage, and when the pressure oil flowing through the first oil passage is stopped, the second oil passage and the third oil passage are connected. It is preferable.

  According to the present invention, in the state where the switching command signal is not output, the flow of pressure oil from the pilot hydraulic pump to the first oil passage is stopped. Therefore, the pilot switching valve connects the second oil passage and the third oil passage. As a result, the hydraulic pressure in the second oil passage is input to the pilot port as a pilot pressure. When the switching command signal is output, the pressure oil from the pilot hydraulic pump flows into the first oil passage. When the hydraulic pressure flows through the first oil passage, the pilot switching valve connects the first oil passage and the third oil passage. The oil pressure in the first oil passage is reduced by the pressure reducing valve, and this reduced oil pressure is input to the pilot port as a pilot pressure. When the reduced hydraulic pressure is input to the pilot port, the flow rate of the pressure oil supplied to the hydraulic actuator changes according to the pilot pressure. Thus, the pilot pressure is switched according to the switching command signal.

  In the present invention, since the oil pressure in the second oil passage is connected to the operation valve, the pressure oil in the second oil passage changes according to the operation amount of the first operation means. Therefore, the hydraulic pressure of the first oil passage, which is reduced according to the hydraulic pressure of the second oil passage by the pressure reducing valve, is also reduced to a pressure corresponding to the operation amount of the first operating means. As a result, the relationship between the operation amount of the first operating means and the pilot pressure can be switched in two stages depending on the presence / absence of the switching command signal, and the pilot pressure remains at the first level even after the switching command signal is output. It will be comprised so that it can change according to the operation amount of this operation means. Therefore, even after the switching command signal is output, the pressure oil having a flow rate corresponding to the operation amount of the first operation means is caused to flow through the hydraulic actuator, and the hydraulic actuator is driven at a driving speed corresponding to the operation amount of the first operation means. Drive.

  Furthermore, according to the present invention, the third oil passage of the pilot switching mechanism is connected to the pilot port of the flow control valve, so that the relationship between the operation amount of the first operating means and the pilot pressure can be switched. be able to. Therefore, the configuration of the flow control valve is not complicated, and the configuration of the valve block provided with the flow control valve is not complicated.

  A construction machine according to the present invention operates a flow rate control valve with a pilot switching mechanism according to claim 1, at least two hydraulic actuators, and a hydraulic actuator to be preferentially driven among the at least two hydraulic actuators. And a switching command unit for outputting the switching command signal, wherein the flow control valve with a pilot switching mechanism is a hydraulic actuator other than the hydraulic actuator to be driven preferentially among the plurality of hydraulic actuators. The switching command section is configured to output a switching command signal when the second operating means is operated.

  According to the present invention, when the second operating means is operated, the switching command unit outputs a switching command signal. When the first operating means is operated at this time, the flow rate of the pressure oil supplied to the hydraulic actuator other than the hydraulic actuator to be preferentially driven is limited by the flow rate control valve with a pilot switching mechanism. Therefore, the flow rate of the pressure oil supplied to the hydraulic actuator to be preferentially driven becomes larger than that of the other hydraulic actuators. As a result, even when a plurality of hydraulic actuators are driven simultaneously, the hydraulic actuators to be preferentially driven are preferentially driven.

  According to the present invention, the pilot pressure input to the flow rate control valve that controls the flow rate of the pressure oil supplied to the hydraulic actuator is switched according to the switching command signal, and the operation amount of the first operating means is changed even after the switching. Accordingly, the drive speed of the hydraulic actuator can be changed.

It is a right view which shows the shovel of embodiment of this invention. It is a hydraulic circuit diagram which shows a part of hydraulic circuit of a hydraulic device. It is a circuit diagram which shows the hydraulic circuit of a pilot switching mechanism. It is a graph which shows the change of the pilot pressure input into the 2nd pilot port with respect to the operation amount of an operation lever. (A) is a circuit diagram which shows a part of hydraulic circuit of 1st prior art, (b) is a circuit diagram which shows a part of hydraulic circuit of 2nd prior art.

  FIG. 1 is a right side view showing an excavator 10 according to an embodiment of the present invention. The excavator 10 is a construction machine that scoops up earth and sand with a bucket 11. The excavator 10 is provided with a boom 13 that can swing in a vertical direction on a vehicle main body 12 that can travel. A base end portion of the arm 14 is swingably attached to the distal end portion of the boom 13. A bucket 11 is swingably attached to the tip of the arm 14. Further, the excavator 10 is provided with a hydraulic device 15. The hydraulic device 15 is configured to drive the boom cylinder 20, the bucket cylinder 21, and the arm cylinder 22 to move the boom 13, the arm 14, and the bucket 11, respectively. The boom hydraulic cylinder 20 is provided between the vehicle body 12 and the boom 13. The bucket hydraulic cylinder 21 is provided between the arm 14 and the bucket 11. The arm hydraulic cylinder 22 is provided to the arm 14 and the bucket 11. Hereinafter, the configuration of the hydraulic device 15 will be described in more detail.

  FIG. 2 is a hydraulic circuit diagram showing a part of the hydraulic circuit of the hydraulic device 15. Below, it demonstrates, also referring FIG. The hydraulic device 15 includes a hydraulic pump 16, a boom direction flow control valve (hereinafter also simply referred to as “boom control valve”) 17, and a bucket direction flow control valve (hereinafter also simply referred to as “bucket control valve”) 18. , An arm directional flow control valve (hereinafter also simply referred to as “arm control valve”) 19, a boom hydraulic cylinder 20, a bucket hydraulic cylinder 21, and an arm hydraulic cylinder 22. The hydraulic pump 16 is, for example, an axial pump, and is configured to discharge pressure oil from the discharge port 16a to the pump passage 23. The downstream side of the pump passage 23 is divided into four passages 23a, 23b, 23c, and 23d, and a check valve 24 is interposed in the first passage 23a. The check valve 24 allows the flow of pressure oil from the upstream side to the downstream side and blocks the flow in the opposite direction. Both the first and second passages 23 a and 23 b are connected to the boom control valve 17. The third passage 23 c is connected to the bucket control valve 18, and the fourth passage 23 d is connected to the arm control valve 19.

  The boom control valve 17 is a center open type 5-port switching valve. The five ports are connected to two cylinder chambers 20a and 20b and a bucket communication passage 25 formed in the boom hydraulic cylinder 20 in addition to the first and second passages 23a and 23b. The boom control valve 17 includes a spool 17a whose stroke changes according to a boom pilot pressure given according to an operation amount of a boom operation lever 46 described later.

  The boom control valve 17 is configured to be connected to the second passage 23b and the bucket communication passage 25 when the spool 17a is in the neutral position. At this time, the first passage 23a and the two cylinder chambers 20a and 20b are blocked. The boom control valve 17 is configured to switch the connection destination of the first passage 23a to one of the two cylinder chambers 20a and 20b according to the position of the spool 17a when the spool 17a moves. . The boom control valve 17 is configured to supply pressure oil at a flow rate corresponding to the stroke of the spool 17a to the cylinder chambers 20a and 20b. At this time, the other of the two cylinder chambers 20a and 20b is connected to the bucket communication passage 25, and the second passage 23b is blocked.

  The boom hydraulic cylinder 20 is configured to expand and contract according to the direction of the pressure oil from the boom control valve 17, that is, according to which of the two cylinder chambers 20a and 20b is supplied with the pressure oil. Yes. At this time, the boom hydraulic cylinder 20 is configured to expand and contract at a drive speed corresponding to the supplied flow rate. Accordingly, the boom hydraulic cylinder 20 expands and contracts at a drive speed corresponding to the operation amount of the boom operation lever 46 (see FIG. 1), and swings the boom 13 in the vertical direction at a swing speed corresponding to the drive speed. .

  A check valve 26 is interposed in the third passage 23c. The check valve 26 allows the flow of pressure oil from the upstream side to the downstream side and blocks the flow in the opposite direction. Both the third passage 23 c and the bucket communication passage 25 are connected to the bucket control valve 18.

  The bucket control valve 18 is a center open type 5-port switching valve. The five ports are connected to two cylinder chambers 21 a and 21 b and an arm communication path 27 formed in the bucket hydraulic cylinder 21 in addition to the third path 23 c and the bucket communication path 25. The bucket control valve 18 has first and second pilot ports 18b and 18c. The bucket control valve 18 includes a spool 18a whose stroke changes in accordance with the pilot pressures of the first and second pilot ports 18b and 18c.

  The bucket control valve 18 is configured to be connected to the bucket communication path 25 and the arm communication path 27 when the spool 18a is in the neutral position. At this time, the third passage 23c and the two cylinder chambers 21a and 21b are blocked. Further, when the pilot pressure is input to the first pilot port 18b and the spool 18a moves, the bucket control valve 18 switches the connection destination of the third passage 23c to the first cylinder chamber 21a, and the second pilot port When the pilot pressure is input to 18c and the spool 18a moves, the connection destination of the third passage 23c is switched to the second cylinder chamber 21b. The unconnected one of the two cylinder chambers 21a and 21b is connected to the arm communication path 27 and the bucket communication path 25 is blocked. Further, the bucket control valve 18 is configured to supply pressure oil having a flow rate corresponding to the position of the spool 18a to the cylinder chambers 21a and 21b.

  The bucket hydraulic cylinder 21 is configured to expand and contract in accordance with the direction of pressure oil from the bucket control valve 18. Specifically, it is configured to contract when pressure oil is supplied to the first cylinder chamber 21a and to expand when pressure oil is supplied to the second cylinder chamber 21b. The bucket hydraulic cylinder 21 is configured to expand and contract at a driving speed corresponding to the flow rate of the pressure oil supplied to the cylinder chambers 21a and 21b. In other words, the bucket hydraulic cylinder 21 expands at a driving speed corresponding to the input pilot pressure, and swings the bucket 11 at a swinging speed corresponding to the driving speed. In the present embodiment, the bucket hydraulic cylinder 21 is configured to swing the bucket 11 in the winding direction when pressure oil is supplied to the second cylinder chamber 21b.

  A check valve 28 is interposed in the fourth passage 23d. The check valve 28 allows the flow of pressure oil from the upstream side to the downstream side and blocks the flow in the opposite direction. Both the fourth passage 23 d and the arm communication passage 27 are connected to the arm control valve 19.

  The configuration of the arm control valve 19 is substantially the same except that the passage connected to the bucket control valve 18 is different. The arm hydraulic cylinder 22 is also substantially the same in configuration except for the arrangement of the bucket hydraulic cylinder. Only the differences will be described below.

  The five ports of the arm control valve 19 are connected to two cylinder chambers 22 a and 22 b and a tank 29 formed in the arm hydraulic cylinder 22 in addition to the fourth passage 23 d and the arm communication passage 27. The spool 19a of the arm control valve 19 is configured to move according to the pilot pressures of the first pilot port 19b and the second pilot port 19c. The hydraulic cylinder 22 for arm contracts when pressure oil is supplied to the first cylinder chamber 22a and swings the arm 14 upward, and expands when pressure oil is supplied to the second cylinder chamber 22b. Thus, the arm 14 is configured to swing downward.

  A relief valve 50 is provided upstream of the branch point of the pump passage 23. The relief valve 50 is connected to the tank 29, and is configured to discharge the pressure oil flowing through the pump passage 23 to the tank 29 when the pump passage 23 exceeds a predetermined pressure.

  FIG. 3 is a circuit diagram showing a hydraulic circuit of the pilot switching mechanism 30. The pilot switching mechanism 30 is provided in each of the bucket control valve 18 and the arm control valve 19. Each pilot switching mechanism 30 has substantially the same configuration, and the pilot port to be input is the first and second pilot ports 18b and 18c of the bucket control valve 18, or the first and second pilot ports of the arm control valve 19. This is the difference between the pilot ports 19b and 19c. Below, the pilot switching mechanism 30 provided in the bucket control valve 18 will be described, and the description of the pilot switching mechanism 30 provided in the arm control valve 19 will be omitted.

  The pilot switching mechanism 30 inputs a pilot pressure corresponding to the operation amount of the tilting operation of the operation lever 31 to the first or second pilot port 18b, 18c of the bucket control valve 18. The pilot switching mechanism 30 switches the correspondence relationship between the pilot pressure of the second pilot port 18c and the operation amount of the operation lever 31 in accordance with a switching command signal output in response to the operation of the boom operation lever 46. Even after switching, the pilot pressure corresponding to the operation amount is input to the second pilot port 18c.

  The pilot switching mechanism 30 includes a pilot pump passage 41, an operation lever 31, an operation valve 32, an electromagnetic valve 33, a pressure reducing valve 34, and a pilot direction switching valve 35. A discharge port 40a of a pilot hydraulic pump 40 that is a gear pump, for example, is connected to the pilot pump passage 41. The pilot pump passage 41 is divided into two on the downstream side, one connected to the operation valve 32 and the other connected to the electromagnetic valve 33.

  The operation valve 32 is provided with an operation lever 31 for moving the bucket 11. The operation lever 31 is provided in the driver's seat of the vehicle main body 12 so that the operation valve 32 can tilt in the front-rear direction. The operation valve 32 is connected to the first pilot passage 43 connected to the first pilot port 18 b and the main passage 42. The operation valve 32 is configured to switch the connection destination of the pilot pump passage 41 to one of the main passage 42 and the first pilot passage 43 in accordance with the tilting operation of the operation lever 31. For example, the connection destination is switched to the first pilot passage 43 when tilted backward, and the connection destination is switched to the main passage 42 when tilted forward. The operation valve 32 is configured to output pressure oil having a pressure corresponding to the tilt angle θ of the operation lever 31 to the connection destination passage.

  The electromagnetic valve 33 is connected to the sub passage 45 together with the pilot pump passage 41. The electromagnetic valve 33 which is a direction switching valve is a so-called solenoid valve having a solenoid 33a. The solenoid 33a is electrically connected to detection means 46a for detecting the tilting operation of the boom operation lever 46. The detecting means 46a which is a switching command section is configured to output a switching command signal which is an electric current when the tilting operation of the boom operation lever 46 is detected. The detection means 46a is a limit switch, for example. The electromagnetic valve 33 is configured to switch the connection state between the pilot pump passage 41 and the sub passage 45 in accordance with a switching command signal input to the solenoid 33a. In other words, when the boom operation lever 46 is operated, the solenoid valve 33 causes pressure oil to flow from the pilot pump passage 41 to the sub-passage 45, the operation of the boom operation lever 46 is stopped, and the boom operation lever 46 is neutral. When returned to the position, the flow of pressure oil from the pilot pump passage 41 to the sub passage 45 is stopped.

  The sub-passage 45 has a pressure reducing valve 34 in the middle thereof. The pressure reducing valve 34 is configured to reduce the hydraulic pressure in the sub passage 45 to a pressure corresponding to the differential pressure between the hydraulic pressure on the secondary side of the pressure reducing valve 34 and the hydraulic pressure in the main passage 42. In the present embodiment, the pressure reducing valve 34 reduces the pressure of the sub passage 45 to a pressure lower than that of the main passage 42.

  The downstream side of the main passage 42 and the sub passage 45 is connected to the pilot direction switching valve 35. Further, the pilot direction switching valve 35 is connected to the second pilot port 18 c of the bucket control valve 18 via the second pilot passage 47. The pilot directional control valve 35, which is a pilot switching valve, connects the second pilot passage 47 to either the main passage 42 or the sub passage 45 according to the hydraulic pressure upstream of the pressure reducing valve 34 of the sub passage 45. It is configured to switch to either.

  In the pilot switching mechanism 30 configured as described above, before the boom operation lever 46 is operated, the switching command signal is not output to the electromagnetic valve 33, and the pilot valve passage 41 moves from the pilot pump passage 41 to the sub passage 45 by the electromagnetic valve 33. The flow of pressure oil is stopped. Therefore, the hydraulic pressure of the sub passage 45 is low, and the main passage 42 and the second pilot passage 47 are connected by the pilot direction switching valve 35. In this state, when the operation lever 31 is operated forward, the pressure oil supplied from the operation valve 32 to the main passage 42 passes through the pilot direction switching valve 35 and the second pilot passage 47, and the second Is supplied to the pilot port 18c. That is, the pilot pressure is input to the second pilot port 18c. As a result, the third passage 23c is connected to the second cylinder chamber 21b, and the bucket 11 swings in the winding direction. Since the flow rate supplied to the main passage 42 changes according to the operation amount of the operation lever 31, the pilot pressure of the second pilot port 18 c changes according to the operation amount of the operation lever 31.

  Next, when the boom operation lever 46 is operated, a switching command signal is output from the detection means 46 a and the pilot pump passage 41 and the sub passage 45 are connected by the electromagnetic valve 33. As a result, pressure oil flows from the pilot pump passage 41 to the sub-passage 45, and the hydraulic pressure of the sub-passage 45 increases. As the hydraulic pressure in the sub-passage 45 increases, the pilot direction switching valve 35 switches the connection destination of the second pilot passage 47 to the sub-passage 45. When the operation lever 31 is operated forward in this state, pressure oil is supplied from the operation valve 32 to the main passage 42, and the primary side and the secondary side of the pressure reducing valve 34 are connected. Thereby, the pressure oil decompressed by the pressure reducing valve 34 is supplied from the secondary side to the pilot direction switching valve 35. The reduced pressure oil passes through the second pilot passage 47 and is input to the second pilot port 18c. As a result, the pilot pressure in the second pilot port 18c becomes smaller than before the boom operation lever 46 is operated. That is, the pilot pressure of the second pilot port 18c is switched between two kinds of magnitudes depending on the presence / absence of a change command signal.

  Further, the pressure reducing valve 34 reduces the pressure oil flowing to the secondary side of the pressure reducing valve 34 to a hydraulic pressure corresponding to the differential pressure between the hydraulic pressure of the main passage 42 and the secondary side hydraulic pressure of the pressure reducing valve 34. Therefore, the secondary side hydraulic pressure of the pressure reducing valve 34 is a pressure corresponding to the hydraulic pressure of the main passage 42. Accordingly, the pilot pressure of the second pilot port 18 c changes according to the operation amount of the operation lever 31.

  FIG. 4 is a graph showing a change in the pilot pressure of the second pilot port 18 c with respect to the operation amount of the operation lever 31. A change in pilot pressure before the boom operation lever 46 is operated is indicated by a solid line, and a change after the boom operation lever 46 is operated is indicated by a one-dot chain line. The two-dot chain line is a pilot pressure input to the boom control valve 17 when the boom operation lever 46 and the operation lever 31 are operated simultaneously.

  As shown in FIG. 4, the pilot pressure of the second pilot port 18 c changes according to the operation amount of the operation lever 31 regardless of the presence / absence of the switching command signal. Then, the correspondence between the operation amount of the operation lever 31 and the pilot pressure of the second pilot port 18c is switched depending on the presence / absence of the switching command signal. Specifically, the increase amount of the pilot pressure with respect to the operation amount of the operation lever 31 changes. Thus, the pilot switching mechanism 30 can switch the correspondence relationship between the operation amount of the operation lever 31 and the pilot pressure of the second pilot port 18c in two stages depending on the presence or absence of the switching command signal, and the operation lever The pilot pressure of the second pilot port 18c changes according to the operation amount of 31.

  Therefore, when the switching command signal is output, even if the operation amount of the operating lever 31 is the same as when the switching command signal is not input, the pilot pressure of the second pilot port 18c decreases, and the spool 18a Stroke is shortened. Thereby, the flow volume of the pressure oil which flows into the 2nd cylinder chamber 21b from the 3rd channel | path 23c is restrict | limited. In contrast, the pilot pressure applied to the spool 17a of the boom control valve 17 remains substantially unchanged after the switching command signal is output. Therefore, the pilot pressure changes in accordance with the operation amount of the boom operation lever 46 (see the two-dot chain line in FIG. 4), and the change in the stroke of the spool 17a does not change substantially. Accordingly, of the pressure oil divided into the hydraulic cylinders 20, 21, the pressure oil having a flow rate that is limited by the bucket direction flow control valve flows into the boom hydraulic cylinder 20. Therefore, the boom hydraulic cylinder 20 flows more than the bucket hydraulic cylinder 21, and the boom 13 is driven preferentially over the bucket 11.

  The pilot switching mechanism 30 simultaneously drives the boom hydraulic cylinder 20 and the bucket hydraulic cylinder 21 even when the boom hydraulic cylinder 20, the bucket hydraulic cylinder 21 and the arm hydraulic cylinder 22 are simultaneously driven. Works like time. That is, the pilot switching mechanism 30 switches the pilot pressure of the second pilot ports 18c and 19c based on the switching command signal, and causes a large amount of hydraulic oil to flow through the boom hydraulic cylinder 20 to give priority to the boom hydraulic cylinder 20. Drive.

  The pilot switching mechanism 30 configured as described above connects the first and second pilotle passages 43 and 47 to the first and second pilot ports 18b and 18c of the bucket direction flow control valve 18, The bucket directional flow control valve 18 can switch the relationship between the operation amount of the operation lever 31 and the pilot pressure. Therefore, the configuration of the bucket directional flow control valve 18 is not complicated, and the configuration of a valve block (not shown) provided with the bucket directional flow control valve 18 is not complicated.

  According to the present embodiment, the switching command signal is output according to the operation of the boom operation lever 46, but it is configured to output by operating different operating means, for example, a switch. Also good. Specifically, it is configured to be able to switch between the quick operation mode and the fine adjustment mode with a switch. When the switch is operated to switch from the fine adjustment mode to the sudden operation mode, the switching command signal is input to the electromagnetic valve 33. The pressure reducing valve 34 is configured such that the secondary side hydraulic pressure is higher than the hydraulic pressure of the main passage 42.

  With this configuration, when the switching command signal is input to the electromagnetic valve 33 and the operation mode is switched to the sudden operation mode, the stroke of the spool 19a increases. Therefore, when switching to the sudden operation mode, the increase amount of the pilot pressure with respect to the operation amount of the operation lever 31 becomes larger than in the fine adjustment mode. As a result, it is possible to perform doha hitting by quickly swinging the arm 14 downward and hitting the ground with the bucket 11. When the fine adjustment mode is restored, the arm 14 is swung slowly so that the bucket 11 can be moved horizontally while being rubbed against the ground.

  In the present embodiment, the electromagnetic valve 33 is configured by an electromagnetic direction switching valve, but may be an electromagnetic on-off valve that is a kind of direction switching valve. A pilot-type direction switching valve may be employed instead of the electromagnetic valve 33. In this case, it can be realized by inputting the pressure oil guided from the boom control valve 17 to the boom hydraulic cylinder 20 to the pilot-type direction switching valve as pilot oil as a switching command signal.

  In the present embodiment, the drive hydraulic pump 16 and the pilot hydraulic pump 40 are provided. However, the drive hydraulic pump 16 may also function as the pilot hydraulic pump 40. good. Thereby, the pilot hydraulic pump 40 is omitted, and the number of parts of the excavator is reduced. Therefore, the construction of the shovel is simplified.

  In this embodiment, a hydraulic cylinder is used as the hydraulic actuator, but a hydraulic motor may be used.

  In the present embodiment, an excavator is described, but the same effect can be obtained even when applied to a construction machine such as a bulldozer or a wheel loader.

  The present invention is not limited to the embodiments, and can be added, deleted, and changed without departing from the spirit of the invention.

DESCRIPTION OF SYMBOLS 10 Excavator 16 Hydraulic pump 17 Boom directional flow control valve 18 Bucket directional flow control valve 18b First pilot port 18c Second pilot port 19 Arm directional flow control valve 19b First pilot port 19c Second pilot port 20 Boom Hydraulic Cylinder 21 Bucket Hydraulic Cylinder 22 Arm Hydraulic Cylinder 30 Pilot Switching Mechanism 31 Operation Lever 33 Solenoid Valve 34 Pressure Reducing Valve 35 Pilot Directional Switching Valve 42 Main Passage 45 Sub Passage 46a Detection Means 47 Second Pilot Passage

Claims (2)

The oil pressure output from the operation valve is input to the pilot port according to the operation amount of the first operation means for driving the hydraulic actuator, and the flow rate of the pressure oil flowing to the hydraulic actuator according to the pilot pressure of the pilot port A flow control valve with a pilot switching mechanism for changing
A pressure reducing valve for reducing the hydraulic pressure from the pilot hydraulic pump to a pressure corresponding to the hydraulic pressure from the operation valve;
When a switching command signal is output from the switching command unit, a pilot pressure switching valve that switches the hydraulic pressure input to the pilot port to the hydraulic pressure output from the pressure reducing valve;
A first oil passage connected to the pilot hydraulic pump;
A second oil passage connected to the operation valve;
A third oil passage connected to the pilot port;
A directional switching valve for flowing pressure oil from a pilot hydraulic pump to the first oil passage in response to the switching command signal output from the switching command unit ;
The pressure reducing valve is interposed in the first oil passage, reduces the oil pressure of the first oil passage according to the oil pressure of the second oil passage,
When pressure oil flows through the first oil passage, the pilot pressure switching valve connects the first oil passage and the third oil passage, and stops the pressure oil flowing through the first oil passage. is the, the second oil passage and the third pilot switching mechanism with the flow control valve characterized that you have been configured so as to connect the oil passage. A flow control valve with a pilot switching mechanism according to claim 1 ,
At least two of the hydraulic actuators;
Second operating means for driving a hydraulic actuator to be driven preferentially among the at least two hydraulic actuators;
A switching command unit that outputs the switching command signal;
The pilot control mechanism-equipped flow control valve is provided in each of the hydraulic actuators other than the hydraulic actuator to be preferentially driven among the plurality of hydraulic actuators,
A construction machine such as an excavator, wherein the switching command unit is configured to output a switching command signal when the second operating means is operated.

Images