JP2011196475A - Hydraulic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic circuit which prevents the occurrence of an operator's unintended malfunction of a directional selector valve when starting an engine.SOLUTION: This hydraulic circuit includes the directional selector valve 1 for controlling supply of oil to a hydraulic cylinder 3, a pilot valve 10 for moving a main spool 2 in a mode of approaching a pilot spool 20 by making pilot pressure act on the other end part of the main spool 2 by communicating an input port 12 with an output port 14 by moving the pilot spool 20 in a mode of approaching one end of the main spool 2 when an operation force is applied, and a feedback spring 34 abutting on the other end of the directional selector valve 1 and an end of the pilot valve 10. The pilot valve 10 cuts off the input port 12 and the output port 14, and communicates a drain port 13 with the output port 14 when in a neutral state.

Description

  The present invention relates to a hydraulic circuit, and more particularly to a hydraulic circuit applied to a vehicle such as a construction machine.

  As this type of hydraulic circuit, one having a directional switching valve and a pilot valve is known. The direction switching valve has a main spool and controls the flow of oil between the supply pump and the actuator.

  The pilot valve is arranged so that the pilot valve body accommodates both ends of the main spool at both ends of the direction switching valve, and controls the operation of the direction switching valve. Each of these pilot valves has a pilot spool that moves on the same axis as the main spool.

  When these pilot valves are in a neutral state where no operating force is applied, both the input ports and the output ports formed in the pilot valve main body communicate with each other. Thereby, in one pilot valve, the oil introduced through the input port flows into the pressure chamber between the pilot valve and the direction switching valve through the output port. In the other pilot valve, the oil introduced through the input port flows into the pressure chamber between the pilot valve and the direction switching valve through the output port. In this way, the state in which the oil has flowed into each pressure chamber is maintained, whereby the pressures in both pressure chambers are maintained at an equal magnitude to restrict the movement of the main spool.

  Then, when an operating force is applied to one of these pilot valves, the pilot spool that constitutes the pilot valve is moved toward one end of the main spool, and the pilot port as in the output port and the output port is moved. The tank port formed in the valve body is communicated. As a result, the pressure in the pressure chamber between the pilot valve and the direction switching valve becomes equal to the tank pressure, and a pressure difference is generated between the two pressure chambers. The main spool is moved by the pressure difference, and the oil supply to the actuator is controlled (see, for example, Patent Document 1 and Patent Document 2).

US Pat. No. 5,664,477 US Pat. No. 5,568,759

  By the way, in the neutral state before starting the engine, the hydraulic circuit has a pressure equal to the tank pressure in the state where residual air is present in the pressure chamber, and the main spool is driven by a spring force provided at a position facing the pressure chamber. Is held in the neutral position. When the engine is started from such a state, the hydraulic pump is driven and oil is discharged into both pressure chambers. However, due to the influence of residual air, the pressure chambers may not instantaneously become the same pressure, and a pressure difference may occur. If there is a pressure difference between the two pressure chambers in this way, a pressure difference will occur on both sides of the main spool, and the directional control valve will move from the higher pressure to the lower pressure, causing an unintended malfunction by the operator. There was a risk of causing it.

  In view of the above circumstances, an object of the present invention is to provide a hydraulic circuit that can prevent a malfunction of a direction switching valve that is not intended by an operator when starting an engine.

  In order to achieve the above object, a hydraulic circuit according to claim 1 of the present invention is disposed in an oil passage connecting the first supply pump and the actuator, and a direction switching valve for controlling the supply of oil to the actuator; One end of the directional control valve is arranged in an oil passage extending from the second supply pump to one end of the directional switching valve, and the input port and the output port communicate with each other when an operating force is applied. A pilot valve that applies a pilot pressure to the portion, and a spring member that abuts against the other end of the direction switching valve and the end of the pilot valve, and when the pilot valve is in a neutral state, the input port And the output port, and the drain port and the output port are communicated with each other.

  According to the hydraulic circuit of the present invention, when the pilot valve is in a neutral state, the input port and the output port are shut off and the drain port and the output port are communicated with each other, so that the pilot pressure is applied. Oil can be discharged into the tank. As a result, the end of the direction switching valve can be made equal to the tank pressure. Moreover, since the pressure is equal to the tank pressure, no pressure acts on the direction switching valve even when the engine of the vehicle to which the hydraulic circuit is applied is started, and there is no possibility of being affected by residual air. Therefore, it is possible to prevent the malfunction of the direction switching valve that is not intended by the operator when starting the engine.

FIG. 1 is a hydraulic circuit diagram showing a hydraulic circuit according to an embodiment of the present invention. FIG. 2 shows a modification of the hydraulic circuit shown in FIG. 1, and is a hydraulic circuit diagram showing a hydraulic circuit in which pilot valves are provided on both ends of the direction switching valve. FIG. 3 is an enlarged cross-sectional view showing a main part of the hydraulic circuit shown in FIG. 4 is a cross-sectional view schematically showing an example of a stopped state of the pilot spool in FIG. FIG. 5 is a cross-sectional view schematically showing an example of a stopped state of the pilot spool in FIG. FIG. 6 is a cross-sectional view schematically showing another example of the stopped state of the pilot spool in FIG. FIG. 7 is an enlarged cross-sectional view showing a main part of a modification of the hydraulic circuit according to the embodiment of the present invention.

  Exemplary embodiments of a hydraulic circuit according to the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a hydraulic circuit diagram showing a hydraulic circuit according to an embodiment of the present invention. The hydraulic circuit exemplified here is applied to a vehicle such as a construction machine, for example, and includes a direction switching valve 1 and a pilot valve 10.

  The direction switching valve 1 is constituted by a two-position three-port switching valve, and controls the supply of oil to a hydraulic cylinder (single-acting cylinder) 3 that is an actuator. The direction switching valve 1 includes an input port 2a, an output port 2b, and a drain port 2c.

  The input port 2a is connected to the oil supply path 4a. The oil supply passage 4a is an oil passage for supplying the oil pressurized by the supply pump (first supply pump) P1. In addition to the supply pump P1, the oil supply passage 4a is provided with a pressure control valve PR. The pressure control valve PR is for discharging oil to the tank T1 through the bypass oil passage BP1 when the discharge pressure at the supply pump P1 exceeds a predetermined magnitude. The output port 2b is connected to the hydraulic cylinder 3 via an oil passage, and the drain port 2c is connected to the tank T2 via an oil passage. Thus, the direction switching valve 1 is disposed in the oil passage that connects the supply pump P1 and the hydraulic cylinder 3.

  In such a directional switching valve 1, in the neutral state where no operating force is applied, it is defined at the position (b) by the urging force of the return spring 35, the input port 2a is shut off as shown, and the output port 2b The drain port 2c is in communication.

  The pilot valve 10 is a two-position / three-port switching valve, and includes a drain port 12, an input port 13, and an output port 14. A proportional solenoid 40 is provided at the base end of the pilot valve 10. The proportional solenoid 40 is electrically connected to the controller 42 and is excited (driven) when an operation signal is given from the controller 42 when the lever device 43 is operated. As described above, the proportional solenoid 40 is excited, so that an operating force is applied to the pilot valve 10.

  A feedback spring (spring member) 34 is disposed between the front end portion of the pilot valve 10 and one end portion (right end portion in the illustrated example) of the direction switching valve 1 so as to be in contact with both. The feedback spring 34 constantly biases the pilot valve 10 in a manner to separate the pilot valve 10 from the direction switching valve 1. In the illustrated example, a tank T4 is provided between one end of the direction switching valve 1 and the pilot valve 10. Although the tank T4 is provided here, the direction switching valve 1 and the pilot 10 may be opened to the outside.

  The drain port 12 is connected to the tank T3 via a drain oil passage 21. The input port 13 is connected to the supply oil path 22. The supply oil passage 22 is an oil passage for supplying the oil pressurized by the supply pump (second supply pump) P2. The supply oil path 22 is provided with a pressure control valve PR in addition to the supply pump P2. The pressure control valve PR is for discharging oil to the tank T3 via the bypass oil passage BP2 when the discharge pressure at the supply pump P2 exceeds a predetermined magnitude.

  The output port 14 is connected to the other end portion (the left end portion in the illustrated example) of the direction switching valve 1 via the control oil passage 23. The output port 14 supplies oil to the left end portion of the direction switching valve 1 via the control oil passage 23 to apply a pilot pressure. Thus, the pilot valve 10 is disposed in the oil passage from the supply pump P2 to the left end portion of the direction switching valve 1.

  In such a pilot valve 10, in a neutral state where no operating force is applied from the proportional solenoid 40, the pilot valve 10 is defined at the position (a) by the urging force of the feedback spring 34, and the drain port 12 and the output port as shown in the figure. 14 and communication between the input port 13 and the output port 14 is blocked.

  In such a neutral state, (1) the left end portion of the direction switching valve 1 is led to the tank T3 from the pilot valve 10 to the tank T3, and (2) the direction switching valve 1 is (b) by the urging force of the return spring 35. The input port 2a is shut off, the output port 2b and the drain port 2c communicate with each other, and (3) the hydraulic cylinder 3 communicates with the tank T2 through the direction switching valve 1 to become tank pressure.

  When the lever device 43 is operated by the operator and an operation signal is given from the controller 42 to the proportional solenoid 40, the proportional solenoid 40 is excited. When the proportional solenoid 40 is excited, an operating force is applied to the pilot valve 10.

  The pilot valve 10 to which the operating force is applied switches from the position (a) to the position (b) against the urging force of the feedback spring 34. When the pilot valve 10 is switched to the position (b), the communication between the drain port 12 and the output port 14 is blocked, and the input port 13 and the output port 14 are communicated.

  When the input port 13 and the output port 14 communicate with each other, oil from the supply oil passage 22 is supplied to the left end portion of the direction switching valve 1 via the control oil passage 23. As a result, the pilot pressure from the supply pump P2 acts on the left end of the direction switching valve 1.

  Due to the action of the pilot pressure, the direction switching valve 1 switches from the position (b) to the position (a) against the urging force of the return spring 35. As a result, the feedback spring 34 is bent by the amount of movement by which the direction switching valve 1 is switched from the position (b) to the position (a), and the spring load (resistance force) increases. In this way, as the spring load of the feedback spring 34 increases, the pilot valve 10 is pressed toward the right side, whereby the pilot valve 10 reaches a position where the operating force from the proportional solenoid 40 and the spring load of the feedback spring 34 become equal. Moves to the right. As the pilot valve 10 moves to the right in this way, the oil supplied to the left end portion of the direction switching valve 1 via the control oil passage 23 is reduced and acts on the left end portion of the direction switching valve 1. The pilot pressure is reduced. As a result, the direction switching valve 1 stops at a position where the pilot pressure acting on the left end, that is, the reduced pilot pressure, and the urging force (spring force) of the return spring 35 are balanced. The direction switching valve 1 balances by repeating these operations by the action of the pilot pressure.

  By such switching of the direction switching valve 1, the communication between the output port 2b and the drain port 2c is cut off, and the input port 2a and the output port 2b are communicated. In this way, the input port 2a and the output port 2b communicate with each other, so that the oil that has been adjusted to a predetermined pressure by the supply pump P1 and the pressure control valve PR and has passed through the oil supply passage 4a enters the hydraulic cylinder 3 through the direction switching valve 1. The flow and the hydraulic cylinder 3 operate.

  As described above, in the hydraulic circuit described above, when the pilot valve 10 is in a neutral state where no operating force is applied, the pilot valve 10 is defined by the feedback spring 34 at the position (a). Thereby, the input port 13 and the output port 14 are shut off, and the drain port 12 and the output port 14 are communicated with each other, so that the oil used to apply the pilot pressure can be discharged to the tank T3. Therefore, the left end portion of the direction switching valve 1 can be made equal to the tank pressure, and the position of the direction switching valve 1 is only defined by being biased by the return spring 35. In addition, since the left end portion of the direction switching valve 1 is made equal to the tank pressure, even when the engine or the like of the vehicle to which the hydraulic circuit is applied is started, no pressure acts on the direction switching valve 1 and the residual air There is no fear of being affected.

  Therefore, according to the hydraulic circuit of the present embodiment, it is possible to prevent the malfunction of the direction switching valve 1 that is not intended by the operator when starting the engine.

  FIG. 2 shows a modification of the hydraulic circuit shown in FIG. 1, and is a hydraulic circuit diagram showing a hydraulic circuit in which pilot valves are provided on both ends of the direction switching valve. The hydraulic circuit exemplified here is applied to a vehicle such as a construction machine, for example, and includes a direction switching valve 1, a right pilot valve 10 and a left pilot valve 10 '.

  The direction switching valve 1 is constituted by a three-position four-port switching valve, and controls the supply of oil to a hydraulic cylinder (return cylinder) 3 that is an actuator. The direction switching valve 1 includes an input port 2a, two output ports 2b and 2b ', and a drain port 2c.

  The input port 2a is connected to the oil supply path 4a. The oil supply passage 4a is an oil passage for supplying the oil pressurized by the supply pump (first supply pump) P1. In addition to the supply pump P1, the oil supply passage 4a is provided with a pressure control valve PR. The pressure control valve PR is for discharging oil to the tank T1 through the bypass oil passage BP1 when the discharge pressure at the supply pump P1 exceeds a predetermined magnitude. One output port 2b is connected to one side of the hydraulic cylinder 3 via an oil passage, and the other output port 2b 'is connected to the other side of the hydraulic cylinder 3 via another oil passage. . The drain port 2c is connected to the tank T2 via an oil passage. Thus, the direction switching valve 1 is disposed in the oil passage that connects the supply pump P1 and the hydraulic cylinder 3.

  In such a direction switching valve 1, in the neutral state where no operating force is applied, the directional switching valve 1 is defined at the position (b) by the urging force of the right return spring 35 and the left return spring 35 '. That is, as shown in the figure, the input port 2a, the output ports 2b and 2b ', and the drain port 2c are defined at positions where they are blocked.

  The right pilot valve 10 is composed of a two-position three-port switching valve, and is located on the right side of the direction switching valve 1 on the paper surface. The right pilot valve 10 includes a drain port 12, an input port 13, and an output port 14. A proportional solenoid 40 is provided at the right end of the right pilot valve 10. The proportional solenoid 40 is electrically connected to the controller 42 and is excited (driven) when an operation signal is given from the controller 42 when the lever device 43 is operated. As described above, the proportional solenoid 40 is excited, so that an operating force is applied to the right pilot valve 10.

  A feedback spring (spring member) 34 is disposed between the front end portion (left end portion in the illustrated example) of the right pilot valve 10 and the right end portion of the direction switching valve 1 so as to be in contact with both. . The feedback spring 34 constantly urges the right pilot valve 10 in a manner to separate the right pilot valve 10 from the direction switching valve 1.

  The drain port 12 is connected to the tank T3 via a drain oil passage 21. The input port 13 is connected to the supply oil path 22. The supply oil passage 22 is an oil passage for supplying the oil pressurized by the supply pump (second supply pump) P2. The supply oil path 22 is provided with a pressure control valve PR in addition to the supply pump P2. The pressure control valve PR is for discharging oil to the tank T3 via the bypass oil passage BP2 when the discharge pressure at the supply pump P2 exceeds a predetermined magnitude.

  The output port 14 is connected to the left end portion of the direction switching valve 1 via the control oil passage 23. The output port 14 supplies oil to the left end portion of the direction switching valve 1 via the control oil passage 23 to apply a pilot pressure. Thus, the right pilot valve 10 is disposed in the oil passage from the supply pump P2 to the left end portion of the direction switching valve 1.

  In such a right pilot valve 10, in the neutral state where no operating force is applied from the proportional solenoid 40, the position is defined at the position (a) by the biasing force of the feedback spring 34, and the output port 14 and the drain as shown in the figure. The port 12 communicates, and the input port 13 and the output port 14 are blocked.

  The left pilot valve 10 'is composed of a 2-position 3-port switching valve, and is located on the left side of the direction switching valve 1 on the paper surface. The left pilot valve 10 'includes a drain port 12', an input port 13 ', and an output port 14'. A proportional solenoid 40 'is provided at the left end of the left pilot valve 10'. The proportional solenoid 40 ′ is electrically connected to the controller 42, and is excited (driven) when an operation signal is given from the controller 42 by operating the lever device 43. As described above, the proportional solenoid 40 'is excited to apply an operating force to the left pilot valve 10'.

  A feedback spring (spring member) 34 'is disposed between the front end portion (right end portion in the illustrated example) of the left pilot valve 10' and the left end portion of the direction switching valve 1 so as to be in contact with both. It is. The feedback spring 34 ′ constantly urges the left pilot valve 10 ′ in a manner to be separated from the direction switching valve 1.

  The drain port 12 'is connected to the tank T3 via the drain oil passage 21. The input port 13 ′ is connected to the supply oil passage 22. The output port 14 'is connected to the right end portion of the direction switching valve 1 via a control oil passage 23'. This output port 14 'supplies oil to the right end portion of the direction switching valve 1 through a control oil passage 23' to apply a pilot pressure. Thus, the left pilot valve 10 ′ is disposed in the oil passage from the supply pump P 2 to the right end of the direction switching valve 1.

  In such a left pilot valve 10 ', in a neutral state where no operating force is applied from the proportional solenoid 40', the position is defined at the position (a ') by the urging force of the feedback spring 34', and the output port as shown in the figure. 14 'communicates with the drain port 12', and the input port 13 'and the output port 14' are blocked.

  As described above, when both the right pilot valve 10 and the left pilot valve 10 'are in the neutral state, (1) the left and right end portions of the direction switching valve 1 are connected to the tank T3 from the pilot valve 10 to the tank pressure, and (2 The direction switching valve 1 is defined at the position (b) by the biasing force of the return spring 35, and the input port 2a, the output ports 2b, 2b 'and the drain port 2c are shut off.

  Such a hydraulic circuit operates as follows. When the lever device 43 is operated by the operator and an operation signal is given from the controller 42 to the proportional solenoid 40, the proportional solenoid 40 is excited. When the proportional solenoid 40 is excited, an operating force is applied to the right pilot valve 10. Here, the left pilot valve 10 'is in a neutral state and is defined at the position (a'). Therefore, the output port 14 'and the drain port 12' communicate with each other, and the right end portion of the direction switching valve 1 is equal to the tank pressure.

  The right pilot valve 10 to which the operating force is applied switches from the position (a) to the position (b) against the urging force of the feedback spring 34. When the right pilot valve 10 is switched to the position (b), the output port 14 and the drain port 12 are shut off, and the input port 13 and the output port 14 communicate with each other.

  When the input port 13 and the output port 14 communicate with each other, oil from the supply oil passage 22 is supplied to the left end portion of the direction switching valve 1 via the control oil passage 23. As a result, the pilot pressure from the supply pump P2 acts on the left end of the direction switching valve 1.

  Due to the action of the pilot pressure, the direction switching valve 1 switches from the position (b) to the position (a) against the urging force of the return spring 35. As a result, the feedback spring 34 is bent by the amount of movement by which the direction switching valve 1 is switched from the position (b) to the position (a), and the spring load (resistance force) increases. In this way, as the spring load of the feedback spring 34 increases, the pilot valve 10 is pressed toward the right side, whereby the pilot valve 10 reaches a position where the operating force from the proportional solenoid 40 and the spring load of the feedback spring 34 become equal. Moves to the right. As the pilot valve 10 moves to the right in this way, the oil supplied to the left end portion of the direction switching valve 1 via the control oil passage 23 is reduced and acts on the left end portion of the direction switching valve 1. The pilot pressure is reduced. As a result, the direction switching valve 1 stops at a position where the pilot pressure acting on the left end, that is, the reduced pilot pressure, and the urging force (spring force) of the return spring 35 are balanced. The direction switching valve 1 balances by repeating these operations by the action of the pilot pressure.

  By such switching of the direction switching valve 1, the input port 2a and the one output port 2b communicate with each other, and the other output port 2b 'and the drain port 2c communicate with each other. As described above, the input port 2a and the one output port 2b communicate with each other, so that oil from the supply pump P1 flows from the oil supply passage 4a to one side of the hydraulic cylinder 3 through the direction switching valve 1. On the other hand, the other output port 2 b ′ and the drain port 2 c communicate with each other so that the oil on the other side of the hydraulic cylinder 3 is discharged to the tank T 2 through the direction switching valve 1. As a result, the hydraulic cylinder 3 operates.

  As described above, in the hydraulic circuit described above, when the operation force is not applied to the right pilot valve 10, the right pilot valve 10 is defined by the feedback spring 34 at the position (a). As a result, the input port 13 and the output port 14 are blocked and the output port 14 and the drain port 12 are communicated with each other, so that the oil used to apply the pilot pressure can be discharged to the tank T3. Therefore, the left end portion of the direction switching valve 1 can be made equal to the tank pressure, and the direction switching valve 1 is only regulated by being biased by the return spring 35. Moreover, since the left end portion of the direction switching valve 1 is made equal to the tank pressure, no pressure acts on the end portion of the direction switching valve 1 even when the engine of the vehicle to which the hydraulic circuit is applied is started. There is no risk of being affected by residual air.

  Incidentally, the proportional solenoid 40 'is the same as the proportional solenoid 40 described above, and the operation of the left pilot valve 10' and the operation of the direction switching valve 1 associated therewith are also the same as described above. Omit.

  Therefore, according to the hydraulic circuit of the present embodiment, it is possible to prevent the malfunction of the direction switching valve 1 that is not intended by the operator when starting the engine.

  FIG. 3 is an enlarged cross-sectional view showing a main part of the hydraulic circuit shown in FIG. 2 that are the same as those shown in FIG. 2 are assigned the same reference numerals, and redundant descriptions are omitted as appropriate.

  The direction switching valve 1 has one main spool 2 inside the valve body 1a, and controls the flow of oil by moving the main spool 2 along the axial direction.

  The right pilot valve 10 is provided on the right side of the direction switching valve 1. The right pilot valve 10 has a drain port 12, an input port 13, and an output port 14 in the right pilot valve main body 11, and a pilot spool 20 in a spool hole 15 provided so as to communicate these ports 12, 13, and 14. It is prepared.

  The drain port 12 of the right pilot valve main body 11 is a port located on the rightmost side, and is connected to the tank T3 via the drain oil passage 21. The input port 13 is a port adjacent to the drain port 12 and is connected to the supply oil passage 22 connected to the supply pump P2. The output port 14 is a port provided on the side opposite to the drain port 12 and the input port 13, and is connected to the left pressure chamber 30 ′ located on the left side of the main spool 2 via the control oil passage 23.

  The pilot spool 20 has a cylindrical shape having an annular groove 20S at an appropriate position on the outer peripheral surface, and more specifically, along the axis direction of the pilot spool 20 and more specifically on the same axis as the main spool 2. Is inserted into the spool hole 15 of the right pilot valve main body 11 so as to be slidable along

  The annular groove 20S of the pilot spool 20 is disposed in a portion extending from the drain port 12, the input port 13, and the output port 14 in the spool hole 15 of the right pilot valve main body 11, and is moved along the axial direction. In this case, the communication state of the drain port 12, the input port 13, and the output port 14 is switched.

  Further, a plunger 41 that is movable in the left-right direction by a proportional solenoid 40 is connected to the right end portion 20 a of the pilot spool 20. When an operation signal is given from the controller 42 by operating the lever device 43, the proportional solenoid 40 is excited (driven) to apply an operating force to the plunger 41, and the plunger 41 is directed leftward. To move.

  The right pilot valve main body 11 is provided with a right pressure chamber 30. The right pressure chamber 30 is a chamber that is open to the spool hole 15 and is formed adjacent to the valve body 1 a of the direction switching valve 1.

  The right pressure chamber 30 allows the right end 2a1 of the main spool 2 to enter and is housed. More specifically, the right pressure chamber 30 is provided with a spring base 31. The spring pedestal 31 is formed with a spool recess 32 and a spring recess 33 formed so as to communicate with each other, and the right end 2a1 of the main spool 2 is inserted into the spool recess 32 and stored therein. . A part of the feedback spring 34 is inserted into the spring recess 33.

  The feedback spring 34 is a coil spring having one end in contact with the bottom 33 a of the spring recess 33 and the other end in contact with the left end 20 b of the pilot spool 20. The feedback spring 34 always urges the pilot spool 20 toward the right direction.

  A flange portion 31 a is formed on the outer peripheral portion of the spring pedestal portion 31. A return spring 35 whose one end is in contact with the flange portion 31 a and whose other end is in contact with the right end surface 30 a of the right pressure chamber 30 is arranged in a manner in which a part of the spring pedestal portion 31 is wound. The return spring 35 is a coil spring that urges the spring pedestal portion 31 toward the left side, that is, urges the spring pedestal portion 31 so as to contact the right end of the valve body 1 a of the direction switching valve 1.

  A control port 16 is formed in the right pilot valve main body 11 in such a manner that it communicates with the right pressure chamber 30. The control port 16 is connected to the output of the left pilot valve 10 'via a control oil passage 23'. Connected to port 14 '. That is, the right pressure chamber 30 of the main spool 2 is connected to the output port 14 ′ of the left pilot valve 10 ′ via the control oil passage 23 ′.

  The left pilot valve 10 ′ is provided on the left side of the direction switching valve 1. The left pilot valve 10 'has a drain port 12', an input port 13 'and an output port 14' in the left pilot valve main body 11 ', and is provided so as to communicate these ports 12', 13 'and 14'. A pilot spool 20 'is provided in the spool hole 15'.

  The drain port 12 ′ of the left pilot valve body 11 ′ is the leftmost port and is connected to the tank T 3 through the drain oil passage 21. The input port 13 ′ is a port adjacent to the drain port 12 ′, and is connected to the supply oil passage 22 connected to the supply pump P2. The output port 14 'is a port provided on the opposite side of the drain port 12' and the input port 13 ', and is connected to the right pressure chamber 30 located on the right side of the main spool 2 via the control oil passage 23'. .

  The pilot spool 20 'has a cylindrical shape having an annular groove 20S' at an appropriate position on the outer peripheral surface, and more specifically, along the axis direction of the pilot spool 20 'on the same axis as the main spool 2. In FIG. 3, it is inserted into the spool hole 15 'of the left pilot valve body 11' so as to be slidable in the left-right direction.

  The annular groove 20S 'of the pilot spool 20' is disposed at a portion extending from the drain port 12 ', the input port 13', and the output port 14 'in the spool hole 15' of the left pilot valve body 11 '. When moved along the center direction, the communication state of the drain port 12 ', input port 13', and output port 14 'is switched.

  In addition, a plunger 41 'that is movable in the left-right direction by a proportional solenoid 40' is connected to the left end 20a 'of the pilot spool 20'. When an operation signal is given from the controller 42 by operating the lever device 43, the proportional solenoid 40 'is excited (driven) to apply an operating force to the plunger 41' so that the plunger 41 'is moved to the right. It moves in the direction.

  The left pilot valve body 11 'is provided with a left pressure chamber 30'. The left pressure chamber 30 ′ is a chamber that is open to the spool hole 15 ′ and is formed adjacent to the valve body 1 a of the direction switching valve 1.

  The left pressure chamber 30 'allows the left end 2b1 of the main spool 2 to enter and is housed. More specifically, a spring pedestal 31 'is disposed in the left pressure chamber 30'. The spring pedestal 31 ′ is formed with a spool recess 32 ′ and a spring recess 33 ′ formed so as to communicate with each other, and the left end 2 b 1 of the main spool 2 enters the spool recess 32 ′. It is stored. A part of the feedback spring 34 'is inserted into the spring recess 33'.

  The feedback spring 34 'is a coil spring having one end in contact with the bottom 33a' of the spring recess 33 'and the other end in contact with the right end 20b' of the pilot spool 20 '. The feedback spring 34 'always biases the pilot spool 20' toward the left.

  A flange portion 31a 'is formed on the outer peripheral portion of the spring pedestal portion 31'. A return spring 35 ′ having one end on the flange 31 a ′ and the other end abutting on the left end surface 30 a ′ of the left pressure chamber 30 ′ is arranged in such a manner that a part of the spring pedestal 31 ′ is wound around. The return spring 35 ′ is a coil spring that urges the spring pedestal 31 ′ toward the left, that is, urges the spring pedestal 31 ′ in a manner to contact the left end of the valve body 1 a of the direction switching valve 1.

  A control port 16 'is formed in the left pilot valve body 11' in such a manner that it communicates with the left pressure chamber 30 '. The control port 16' is connected to the right pilot valve via the control oil passage 23 '. 10 is connected to the output port 14. That is, the left pressure chamber 30 ′ of the main spool 2 is connected to the output port 14 of the right pilot valve 10 via the control oil passage 23 ′.

  The hydraulic circuit having the above configuration operates as follows. In the following description, the operation of the right pilot valve 10 in FIG. 3 will be mainly described, and the left pilot valve 10 ′ is assumed to be in a neutral state. Further, since the spring force of the return spring 35 is larger than the spring force of the feedback spring 34, the position of the main spool 2 is determined by the balance between the force of the return spring 35 and the pressure chamber 30 ′, and the pilot spool. For the spool 20, the position of the pilot spool 20 is determined by the balance between the spring force of the feedback spring 34 and the force acting on the plunger 41.

  The operation will be described. When an operation signal is given from the controller 42 to the proportional solenoid 40 of the right pilot valve body 11 by the operation of the lever device 43 by the operator, the proportional solenoid 40 is driven to move the plunger 41 to the left. Move in the direction. With this movement of the plunger 41, the pilot spool 20 moves in the left direction against the urging force of the feedback spring 34. As the pilot spool 20 moves, the communication between the output port 14 and the drain port 12 is cut off, while the input port 13 and the output port 14 communicate with each other.

  When the input port 13 and the output port 14 communicate with each other in this way, the oil supplied from the supply oil passage 22 is introduced from the input port 13 and led out from the output port 14, and the main spool 2 is connected via the control oil passage 23. It flows into the left pressure chamber 30 '. When oil flows into the left pressure chamber 30 ′ and the pressure inside the left pressure chamber 30 ′ becomes larger than the urging force of the return spring 35 in the right pressure chamber 30 of the main spool 2, the main spool 2 moves rightward. Move towards. With the movement of the main spool 2, in the right pressure chamber 30, the spring pedestal 31 that is in contact with the right end 2 a 1 of the main spool 2 moves in the right direction against the urging force of the return spring 35. Due to the rightward movement of the spring pedestal 31, the resistance force against the movement of the pilot spool 20 by the feedback spring 34 increases. When the force balance between the plunger 41 that moves the pilot spool 20 toward the left and the feedback spring 34 becomes equal, the movement of the pilot spool 20 stops. Thus, the feedback spring 34 applies a feedback force proportional to the movement of the main spool 2 to the pilot spool 20. By stopping the movement of the pilot spool 20, the movement of the main spool 2 is also stopped.

  Here, there are the following three cases in which the movement of the pilot spool 20 is stopped when the balance of the forces of the plunger 41 and the feedback spring 34 that move the pilot spool 20 toward the left becomes equal.

  That is, as shown in FIG. 4, the annular groove 12a leading to the drain port 12 and the annular groove 13a communicating to the input port 13 are blocked, and the end of the annular groove 20S of the pilot spool 20 is annular. This is a so-called zero lap state in which the movement of the pilot spool 20 stops in a state where it coincides with the end of the groove 12a. However, since it is difficult to manufacture the pilot valves 10 and 10 'that stop the movement of the pilot spool 20 in the zero lap state as described above, the following two states are actually obtained.

  As shown in FIG. 5, the movement of the pilot spool 20 is stopped in a state where the annular groove 12a communicating with the drain port 12 and the annular groove 13a communicating with the input port 13 are completely blocked. It is a state to be done.

  Alternatively, as shown in FIG. 6, the movement of the pilot spool 20 is stopped in a state where the annular groove 12 a communicating with the drain port 12 and the annular groove 13 a communicating with the input port 13 are slightly communicated with each other. It is a state to be done.

  In FIG. 3, the main spool 2 moves rightward by the movement of the pilot spool 20, whereby the flow of oil is controlled by the direction switching valve 1, and a desired operation is performed through the hydraulic cylinder 3. .

  Thereafter, when the lever device 43 is operated to be in a neutral state by the operator, an operation stop signal is given from the controller 42 to the proportional solenoid 40 provided in the right pilot valve 10. As a result, the force from the plunger 41 disappears, and the pilot spool 20 is urged by the feedback spring 34 to move rightward and returns to a position where it abuts against the end face of the left end portion 40a. As the pilot spool 20 moves, the communication between the input port 13 and the output port 14 is blocked, while the output port 14 and the drain port 12 communicate with each other.

  The pilot spool 20 abuts on the left end 40a of the housing that houses the proportional solenoid 40 and stops moving to the right, shuts off the input port 13 and the output port 14, and outputs the output port 14 and the drain port 12. It will be a position to communicate with.

  When the output port 14 and the drain port 12 communicate with each other in this manner, the oil that has flowed into the left pressure chamber 30 ′ is introduced from the output port 14 through the control oil passage 23 and is led out from the drain port 12. It is discharged to the tank T3 through the path 21. As a result, the internal pressure of the left pressure chamber 30 ′ decreases, and is biased by the return spring 35 on the right side of the main spool 2, so that the main spool 2 moves leftward together with the spring pedestal 31. Thereafter, the left end portion 31b of the spring pedestal portion 31 biased by the return spring 35 comes into contact with the valve body 1a of the direction switching valve 1, whereby the movement of the main spool 2 in the left direction is stopped, and the main spool 2 is in the neutral position. Located in.

  As described above, according to the hydraulic circuit described above, when the pilot spool 20 is in the neutral state, the input port 13 and the output port 14 are cut off while the output port 14 and the drain port 12 communicate with each other. Therefore, the pilot spool 20 can be placed at a position where the output port 14 and the drain port 12 communicate with each other with high accuracy without being affected by the influence caused by the above, i.e., the viscosity based on the temperature and the change of the flow.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to this, and various modifications can be made.

  In the above-described embodiment, as an example of giving an operation signal to the pilot spool 20, the proportional solenoid 40 is driven and the pilot spool 20 is moved via the plunger 41. The pilot spool 20 may be moved by giving an operation signal based on the hydraulic pressure and operating the piston 50 as shown in FIG. 7 without being limited to the one that operates the plunger 41 based on the signal. Even with such a configuration, it is possible to exhibit the operational effects of the above-described embodiment.

  As described above, the hydraulic circuit according to the present invention is useful for vehicles such as construction machines.

1 direction switching valve 1a valve body 2 main spool 3 hydraulic cylinder 10 right pilot valve 11 left pilot valve body 12 drain port 13 input port 14 output port 15 spool hole 16 control port 20 pilot spool 20S annular groove 21 drain oil path 22 supply Oil path 23 Control oil path 30 Right pressure chamber 31 Spring seat 32 Spool recess 33 Spring recess 34 Feedback spring 35 Return spring 40 Proportional solenoid 41 Plunger 42 Controller 43 Lever device T3 Tank

Claims (1)

A directional control valve that is disposed in an oil passage connecting the first supply pump and the actuator and controls the supply of oil to the actuator;
One end of the directional control valve is arranged in an oil passage extending from the second supply pump to one end of the directional switching valve, and the input port and the output port communicate with each other when an operating force is applied. A pilot valve that applies pilot pressure to the part,
A spring member in contact with the other end of the direction switching valve and the end of the pilot valve;
When the pilot valve is in a neutral state, the pilot valve shuts off the input port and the output port, and connects the drain port and the output port.

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