JP2008281208A - Relief valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a relief valve which can keep sure shockless capability even when return pressure at discharging side from a hydraulic motor is set to be very high. <P>SOLUTION: The relief valve is characterized in that in a pressure oil chamber formed within a housing 52, a sleeve 51 having internal diameter sections 51b, and 51c different in diameter is inserted in liquidtight, in that in an internal diameter section large in diameter, a cup 72 enclosing a sleeve rear end aperture in the liquidtight is interfit, in that within the sleeve, a poppet 66 is arranged in such a manner that its tip is faced to a valve seat 57, and a spring seat piston 60 rotatably supporting its rear end in sleeve axial direction is arranged slidably, in that this spring seat piston includes an annular projection 61, and in that when the spring seat piston is moved by a predetermined stroke S in right/left directions by hydraulic force, the annular projection contacts with a sleeve internal diameter stepped portion 51a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hydraulic motor device having a relief valve that can be applied to an inertial body drive circuit for controlling a swing drive device or the like of a hydraulic excavator.

  In general, the inertial body drive circuit is configured to control the hydraulic motor drive by controlling the rotation direction and stop of the pressure oil of the hydraulic pump by a switching valve. Therefore, when the hydraulic motor is rotating in one direction and the switching valve is returned to the neutral position to stop the driving of the inertial body, the return side passage of the hydraulic motor is closed by the switching valve. The inertial rotational force remains, and the oil pressure on the return side suddenly rises to increase the energy and generate a shock, which may damage the gears of the hydraulic motor.

  Therefore, the applicant can first reduce the pressure oil working area of the spring seat piston by moving the spring so as to increase the relief pressure when the pressure in the supply passage rises. The relief valve of the hydraulic motor eliminates the pressure peak at the start of the relief valve and reduces the shock when the pressure of the supply passage rises without the spring seat piston moving at low pressure. And obtained a patent (Patent No. 2571828) (Patent Document 1).

  That is, the relief valve of the hydraulic motor according to this patent includes both of the hydraulic motor 12 that drives the inertial load by the pressure oil supplied and discharged from the hydraulic pump 10 through the switching valve 11 as shown in FIGS. When the rotation of the hydraulic motor is stopped, the poppet 13 moves against the spring 14 pressing one end against the back and opens when the hydraulic motor stops rotating. The oil is relieved to the outlet, and the pressure oil from the supply port is introduced into the spring seat piston chamber 15 through the throttle 16, thereby moving the spring seat piston 17 pressed against the other end of the spring 14. In the relief valves 18A and 18B of the hydraulic motor 12 for adjusting the relief pressure by compressing the spring 14, an inner hole 20 having a stepped smaller diameter than the inner hole 19 loaded with the spring 14 is provided. The spring seat piston 17 having a reduced area is movably fitted to move the spring seat piston 17 in the initial position at a pressure of about the back pressure generated in the return passage when the hydraulic motor rotates. It is configured so that nothing happens.

  However, the operation of the differential direct acting relief valves 18A and 18B constructed and arranged as described above is the same as that shown in FIGS. 11 and 12, when the switching valve 11 is in the neutral state shown in FIG. 12, there is no pressure at the supply port 22, the relief valves 18 </ b> A and 18 </ b> B are inactive, and the tip of the poppet 13 is pressed to the left by the elastic force of the spring 14 to contact the valve seat of the seat 23, The supply port 22 and the outlet 24 are blocked.

  Therefore, when the switching valve 11 is switched from the neutral position to the upper position, the pressure oil of the hydraulic pump 10 flows into the hydraulic motor 12 from the pipeline 25 via the switching valve 11 and rotates in one direction. Is discharged from the pipe line 26 to the tank 27 through the switching valve 11. Next, when the switching valve 11 is switched to the neutral position in order to stop the hydraulic motor 12 from rotating, the circuits of the hydraulic pump 10 and the tank 27 in the pipes 25 and 26 are cut off. Therefore, the hydraulic motor 12 does not stop immediately and the pressure in the pipe line 26 increases. Accordingly, the pressure of the supply port 22 of the relief valve 18B rises through the supply passage 21B, and the poppet 13 is formed by the difference between the valve seat diameter D1 of the seat 23 and the diameter D2 of the rod 29 (D1> D2). The force of the pressure oil of the supply port 22 acts on the effective cross-sectional area to be moved rightward against the elastic force of the spring 14, and the supply port is opened through the valve seat opened by the seat 23 and the lateral hole 30. The relief action is started by connecting the outlet 22 and the outlet 24.

  At the same time, the pressure oil in the supply port 22 is introduced from the passage 31 of the poppet 13 and the rod 29 through the passage 16 through the passage 16 into the spring seat piston chamber 15, and the pressure oil in the spring seat piston chamber 15 is The pressure increases corresponding to the pressure increase of the supply port 22, and the spring seat piston 17 is moved to the left against the elasticity of the spring 14. As a result, the spring 14 is further compressed and the relief pressure increases. The left side of the spring seat piston 17 is required until the left side surface 34 of the flange portion 33 of the spring seat piston 17 comes into contact with the wall surface 36a of the sleeve 36 screwed to the valve body 35 as the pressure in the spring seat piston chamber 15 increases. The stroke L is moved and stopped, and the relief pressure at the time of the stop is the set pressure.

  The pressure oil thus relieved is supplied to the hydraulic motor 12 from the outlet 24 through the outlet passage 37B and the check valve 38A in FIG.

  The inflow of the pressure oil into the spring seat piston chamber 15 is gentle because the throttle 16 is in the middle of the passage 31 and the passage 32. Therefore, the relief pressure rises slowly, and a shock due to a sudden rise in pressure occurs. Relaxed. Further, the set pressure can be increased by increasing the stroke L in which the spring seat piston 17 moves.

Japanese Patent No. 2571928

  In the relief valves 18A and 18B of the hydraulic motor 12 according to the prior art shown in FIGS. 11 and 12 described above, when the pressure of the supply passage 21A, that is, the supply port 22, rises, this pressure is provided in the passage provided in the poppet 13. It flows into the spring seat piston chamber 15 through 31. The inflowing pressure oil acts on the spring seat piston 17 and when it exceeds a certain value, the spring 14 is compressed against the load of the spring 14 and moved to the left in the figure.

  In this movement process, since the pressure oil flows into the spring seat piston chamber 15 through the throttle 16, it takes some time for the spring seat piston 17 to move from the illustrated position to the position where it abuts against the chamber wall 36a. When the relief valve poppet 13 opens in this process, the load of the spring 14 acting on the poppet 13 is finally the load at the position where the spring seat piston 17 contacts the chamber wall 36a. Therefore, a dynamic characteristic is obtained in which the pressure of the oil filler port corresponding to this gradually increases in accordance with the movement of the spring seat piston 17.

  As described above, in the prior art, a relief valve is used as a swing drive hydraulic motor of a hydraulic excavator having a large inertia, and this hydraulic motor is operated by a switching valve. This operation is generated in the hydraulic circuit. The outer diameter of the spring seat piston is reduced so that the shockless function is not lost depending on the pressure of the back pressure, and the effective area when pressure oil acts on the spring seat piston is defined as the outer diameter D3 of the spring seat piston and The annular area formed by the inner diameter D2 is set to be small.

  However, in recent years, the return back pressure of the hydraulic motor tends to be set higher in order to improve the turning operability of the hydraulic excavator. In this case, the outer diameter D3 may be set smaller, but there is a limit on the strength of the annular portion of the spring seat piston. In addition, if the effective area where the pressure oil of the spring seat piston acts is reduced, the amount of oil required to move the spring seat piston is also reduced, and therefore the operating pressure rises while operating the relief valve only with the fixed throttle. It is difficult to adjust or maintain the boosting time.

  In addition, in a hydraulic circuit that performs a swing drive of a hydraulic excavator, etc., the applicant has previously registered a utility model as a configuration of a pressure regulating valve including a relief valve that can significantly reduce a shock during a pressure increase process. No. 2111199 (Japanese Utility Model Publication No. 4-51272) was proposed. As shown in FIG. 13, a relief valve as a pressure regulating valve according to this proposal has one end of a pressure adjusting compression spring 40 connected to a poppet 41 via a pressure compensation flow control valve 46 described later, and the other end within a specified stroke. Each of the pistons 42 is brought into contact with one end face of the slidable piston 42 and the pressure oil in the high pressure chamber 44 is introduced into the piston back pressure chamber 43 of the piston 42 to gradually increase the operating pressure of the pressure regulating valve, The operation pressure is set to be constant at a position where the piston 42 abuts against the stopper portion 45, and a pressure compensation flow rate control valve 46 as a pressure compensation flow rate adjusting means is disposed coaxially with the piston 42, and The pressure oil in the high pressure chamber 44 is introduced into the piston back pressure chamber 43 via the pressure compensation flow control valve 46. In FIG. 13, reference numeral 47 indicates a fixed orifice provided in the pressure compensated flow control valve 46, and 48 indicates a variable orifice.

  In the pressure regulating valve configured as described above, the pressure compensation flow rate adjusting means 46 is provided, so that the pressure rise in the piston back pressure chamber 43 causes a time delay and the position where the piston 42 contacts the stopper portion 45. The pressure rises by gradually decelerating and overcoming the elasticity of the pressure adjusting compression spring 40 until it reaches the final set pressure. In this case as well, the operating pressure increases as described above. It has been difficult to sufficiently adjust or maintain the pressurization time.

  Therefore, as a result of intensive research, the present inventors, when the pressure of the pressure oil in the high pressure chamber rises, the poppet moves and opens against the spring elasticity against this, and the pressure oil in the high pressure chamber is removed. It consists of a differential linear motion relief valve configured to discharge to the low pressure chamber. In the operation process of the relief valve, the spring seat piston pressed against the other end of the spring is moved by a required stroke, and the spring seat piston A relief valve structure configured to increase the operating pressure while compressing the spring in the moving process, and to introduce the pressure oil in the high pressure chamber into the spring seat piston chamber through a throttle provided coaxially with the poppet. A step portion is provided on the outer diameter portion of the sleeve surrounding the rod portion of the poppet, and the step portion of the sleeve and the step portion provided on the inner diameter portion of the spring seat piston are fitted in a liquid-tight and slidable manner. Together In addition, a step space formed by the fitting of the spring seat piston and the sleeve is formed as a spring seat piston chamber, and an annular formed between the rod portion of the poppet and the sleeve into the spring seat piston chamber. By adopting a configuration in which the pressure oil in the high pressure chamber is introduced through the throttle, the effective area of the spring seat piston on which the oil pressure in the high pressure chamber acts can be set very small, and the return pressure of the hydraulic motor is compared. Even if it becomes higher, the spring seat piston will not move due to this return pressure, and if this causes the switching valve to return to the neutral position and decelerate and stop the inertial body, the shockless function is ensured. It has been determined that a relief valve that can be maintained can be obtained.

  Accordingly, an object of the present invention is to provide a hydraulic circuit having a hydraulic motor for performing a swing drive of a hydraulic excavator, etc., in which the return pressure on the discharge side from the hydraulic motor is set very high in order to further improve the operability. Is providing a relief valve that can reliably maintain the shockless function of the relief valve.

  In order to achieve the above object, according to the first aspect of the present invention, when the oil pressure in the high-pressure chamber rises, the poppet moves and opens against the elasticity of the spring against the pressure, and the pressure oil in the high-pressure chamber is reduced. A differential direct acting relief valve configured to be discharged into the chamber, wherein a spring seat piston with which the other end of the spring abuts is provided with a small-diameter inner diameter portion that slidably supports the rear end portion of the poppet A large-diameter inner diameter portion having a larger diameter than the small-diameter inner diameter portion is provided via a stepped portion, and a piston is slidably provided in the large-diameter inner diameter portion, and a spring is provided between the front end surface of the piston and the rear end surface of the poppet. A seat piston chamber is defined, and pressure oil from the high pressure chamber is introduced into the spring seat piston chamber via an annular throttle formed between the outer peripheral surface of the poppet and the inner peripheral surface of the spring seat piston. Before being formed between the small diameter inner diameter part and the large diameter inner diameter part Characterized in that the hydraulic force acting on the stepped portions constituting said spring seat piston so that a predetermined stroke movement.

  In that case, the first piston whose one end surface is in contact with the stepped portion and the second piston disposed opposite to the other end of the first piston can slide freely on the large-diameter inner diameter portion of the spring seat piston. The oil chamber formed between the large-diameter inner diameter portion, the first piston, and the second piston is provided with a spring that biases the first piston toward the spring seat piston chamber, and The piston of No. 2 is provided with a throttle for connecting the oil chamber to the low pressure chamber, so that when the pressure of the spring seat piston chamber rises, the first piston moves against the force of the spring. be able to.

  According to the relief valve of the present invention, even when the return pressure of the hydraulic motor becomes relatively high, the spring seat piston does not move due to this return pressure, and therefore the switching valve is returned to the neutral position. When the inertial body is decelerated and stopped, the shockless function can be reliably maintained, and the operability of the inertial body such as turning drive can be improved more appropriately and safely. can get.

  Hereinafter, embodiments of a relief valve according to the present invention will be described with reference to the drawings.

  1 to 3 show a first embodiment of a relief valve 50 according to the present invention. That is, in FIGS. 1 to 3, the relief valve 50 is attached to the housing 52. The housing 52 is provided with a high-pressure chamber 54 and a low-pressure chamber 56, and a seat 57 incorporated at the tip of the sleeve 51 of the relief valve 50 </ b> A is pressed against the wall surface of the housing 52 via the sleeve 51. The high pressure chamber 54 and the low pressure chamber 56 are liquid-tightly defined.

  A spring seat piston 60, in which a sleeve 58 having two outer diameters, that is, a small diameter portion D3 and a large diameter portion D4, is inserted and disposed in the inner diameter portion of the sleeve 51, is liquid-tightly and slidably supported. is doing.

  A step space portion formed by fitting the step portion 58a of the sleeve 58 and the step portion 60a of the corresponding inner diameter portion (D3, D4) of the spring seat piston 60 is configured as a spring seat piston chamber 62. The spring seat piston chamber 62 is connected to the oil chamber 64 through a lateral hole 59 of the sleeve 58. The spring seat piston chamber 62 passes through an annular restrictor 68 formed of an annular gap formed between the outer diameter portion of the rod portion 67 of the poppet 66 and the inner diameter portion of the sleeve 58, and passes through the passage in the rod portion 67. 69, and a passage 69 in the rod portion 67 is connected to the high-pressure chamber 54.

  A spring 70 is provided between the poppet 66 and the spring seat piston 60. One end of the spring 70 is in contact with the poppet 66, and the other end is in contact with the end of the spring seat piston 60 via a spacer 71 as a means for adjusting the spring force of the spring 70.

  A low-pressure side oil chamber 73 is formed between the sleeve 51 and a cap 72 assembled to one end of the sleeve 51, and the low-pressure side oil chamber 73 is formed from the flange 61 of the spring seat piston 60 and the sleeve. 51 is introduced into the oil chamber 75 through a groove 74 provided in the outer diameter portion of the spring seat piston 60 through a gap 53 in the inner diameter portion of the spring seat 60, and further connected to the low pressure chamber 56 through a hole 76.

  The spring seat piston 60 is configured to move a distance S until one shoulder portion 61 a of the flange portion 61 abuts against the inner diameter side surface 51 a of the sleeve 51.

  Next, the operation of the relief valve in the present embodiment having the above configuration will be described. That is, according to the relief valve 50 of the present embodiment, the oil pressure in the high pressure chamber 54 passes through the passage 69, the annular throttle 68, the oil chamber 64, and the lateral hole 59 provided in the rod portion 67 of the poppet 66. 62 is communicated.

  Therefore, for example, even when the pressure in the high pressure chamber 54 is relatively high, the action area of the spring seat piston 60 on which the pressure of the high pressure chamber 54 for compressing the spring 70 acts is the area due to the diameter of the large diameter portion D4 and the small diameter. Since the area of the annular portion is different from the area due to the diameter of the portion D3, the spring seat piston 60 will move even if the pressure in the high pressure chamber 54 is relatively high if the diameter difference is made relatively small. When the pressure in the high pressure chamber 54 becomes equal to or higher than the set pressure, the spring seat piston 60 moves to the left in the figure, and the pressure oil in the high pressure chamber 54 is transferred to the spring seat piston chamber 62 at this time. Since it is introduced, by adjusting the load of the annular throttle 68 and the spring 70, it is possible to adjust the amount of pressurized oil per unit time into the spring seat piston chamber 62 extremely finely, so that the shockless function is ensured. To maintain Door can be.

  FIG. 4 shows an implementation of a hydraulic circuit when the relief valve 50 according to the present embodiment is applied to a construction machine including a hydraulic motor that hydraulically controls an inertial body having a large inertia such as an upper swing body of a hydraulic excavator. An example is given.

  This hydraulic circuit is basically the same as the hydraulic circuit to which the conventional relief valve shown in FIG. 11 is applied. Therefore, for convenience of explanation, the same reference numerals are given to common components, Detailed description is omitted. That is, reference numerals 50A and 50B are the relief valves in the present embodiment, respectively, and constitute a differential direct acting relief valve. Other components and their hydraulic circuit configurations are the same as those of the conventional hydraulic circuit shown in FIG.

  5 and 6 show a second embodiment of the relief valve 50 according to the present invention. The relief valve 50 of the present embodiment is a modification of the relief valve in the first embodiment described above, and is a pressure compensated flow rate as pressure compensated flow rate adjusting means coaxially with the poppet with respect to the relief valve of the first embodiment. The control spool is provided.

  Therefore, in the configuration of the second embodiment shown in FIGS. 5 and 6, the same components as those of the first embodiment shown in FIGS. 1 to 3 are denoted by the same reference numerals.

  That is, the relief valve 50 of this embodiment has a pressure compensation flow rate control spool as a pressure compensation flow rate adjusting means in an oil chamber 64 formed at the inner diameter portion of the sleeve 58 through which the rod portion 67 of the poppet 66 is inserted at one end. 80 is provided.

  The pressure compensation flow rate control spool 80 is provided with a fixed restrictor 82 at one end facing the rod portion 67 of the poppet 66 to define the oil chamber 64 into two oil chambers 64a and 64b. A flange portion 81 is provided at the other end, and the flange portion 81 is elastically abutted against a stepped portion 58b provided on the inner diameter portion of the sleeve 58 via a spring 83 so as to press the spool 80 in the direction of the poppet 66. It consists of the structure made. Further, the side surface of the spool 80 corresponds to a lateral hole 59 of a sleeve 58 provided so as to communicate with a spring seat piston chamber 62 formed by fitting the spring seat piston 60 and the sleeve 58. An opening 84 is provided in the spring so that the spring seat piston chamber 62 and the oil chamber 64b communicate with each other. One end of the spring 83 is brought into contact with the spool 80 and the other end is brought into contact with a plug 86 that closes the rear end opening of the sleeve 58. Other configurations are the same as those of the relief valve 50 described in the first embodiment.

As shown in FIG. 4, the relief valve 50 of the present embodiment configured in this way is applied to a hydraulic motor 10 for driving the swing of a hydraulic excavator. After the body 28 is driven, when the switching valve 11 is returned to neutral and stopped, brake pressure is instantaneously generated on the discharge side of the hydraulic motor 10, but the oil pressure in the high pressure chamber 54 is before the deceleration stop. In addition, even if it is already relatively high due to the resistance on the discharge side of the switching valve 11, the operating area of the spring seat piston 60 on which the pressure of the high pressure chamber 54 acts to compress the spring 70 is the area due to the diameter of the large diameter portion D4. And the area of the annular portion which is the difference from the area due to the diameter of the small-diameter portion D3, so that the pressure in the high-pressure chamber 54 on the return side of the hydraulic motor 12 in the swivel state is reduced if this diameter difference is relatively small. For example, to improve operability To be 100 kgf / cm ² about a high pressure, the spring seat piston 60 never would move. Accordingly, even when the switching valve 11 is returned to the neutral position and the revolving body 28 is decelerated and stopped, the set pressure of the relief valves 50A and 50B is 150 kgf / cm ² and the set pressure after the spring seat piston 60 moves the required stroke S. if the by setting the 300 kgf / cm ^2, spring seat piston 60 after the oil pressure in the high pressure chamber 54 is increased to 150 kgf / cm ² is moved to the left of the shown, moreover when the high-pressure chamber 54 Since the pressure oil is introduced into the spring seat piston chamber 62 through the pressure compensation flow control spool 80, the load per unit time to the spring seat piston chamber 62 is adjusted by adjusting the loads of the annular throttle 68, the fixed throttle 82, the spring 70, and the like. The amount of pressure oil flowing in can be adjusted to an extremely small level, and the shockless function can be reliably maintained.

  7 is a cross-sectional view of a relief valve according to a third embodiment of the present invention, and FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7 and 8, the relief valve 50 includes a housing 52. A pressure oil inlet 52a (a hydraulic oil inlet 52a (not shown) is connected to the left end surface of the housing 52 via a hydraulic line. 4). The pressure oil inlet 52a communicates with a pressure oil chamber formed inside the housing 52, and a sleeve 51 is inserted into the pressure oil chamber through a sleeve insertion port provided on the right end surface of the housing 52 in the drawing. It is inserted liquid-tight.

  The sleeve 51 has two inner diameter portions 51b and 51c having different diameters, and the rear end opening of the sleeve 51 is liquid-tightly connected to the inner diameter portion 51c having the larger diameter among the inner diameter portions 51b and 51c. A plug-like cap 72 that is closed is inserted in a liquid-tight manner.

  The relief valve 50 includes a valve seat 57 at the tip of the sleeve 51. The valve seat 57 has a pressure oil circulation hole 57a at the center, and the pressure oil that has flowed into the pressure oil chamber 52a from the pressure oil inlet of the housing 52 passes through the pressure oil circulation hole 57a into the sleeve 51. It is configured to flow in. Further, the valve seat 57 is pressed against the wall surface of the pressure oil chamber in the housing 52, whereby the pressure oil chamber in the housing 52 is partitioned into a high pressure chamber 54 and a low pressure chamber 56.

  Inside the sleeve 51, a rod-shaped valve body (poppet) 66 is provided with its front end facing the valve seat 57, and the rear end portion of the poppet 66 can be moved in the axial direction of the sleeve 51. A substantially cylindrical spring seat piston 60 is slidably provided. The spring seat piston 60 has an annular protrusion (ridge part) 61 as a stopper on its outer peripheral surface. When the spring seat piston 60 moves to the left in FIG. 61 is in contact with the inner diameter step portion 51 a of the sleeve 51.

  The spring seat piston 60 has a small-diameter inner diameter portion 60b slidably fitted to the rear end portion of the poppet 66, and a large-diameter inner diameter portion formed adjacent to the rear of the small-diameter inner diameter portion 60b. A piston 100 is slidably provided at 60c. The front end surface 100a (see FIG. 9) of the piston 100 faces the rear end surface 66a of the poppet 66, and a spring seat piston chamber 64 is located between the rear end surface 66a of the poppet 66 and the front end surface 100a of the piston 100. It is defined.

  The poppet 66 has a spring receiving portion 66b slidably in contact with the inner peripheral surface of the sleeve 51 at the distal end portion. Between the spring receiving portion 66b and the spring seat piston 60, the distal end of the poppet 66 is connected to the valve seat 57. A compression coil spring 70 is provided to press the rear end of the spring seat piston 60 against the plug 72. A space 90 is defined between the spring receiving portion 66b and the valve seat 57, and this space 90 communicates with the low pressure chamber 56 through a communication hole 92 formed in the sleeve 51. ing.

  Further, the poppet 66 has a pressure oil circulation hole 69 opening toward the valve seat 57 in the shaft core portion. As shown in FIG. 9, the pressure oil circulation hole 69 has a pressure oil circulation hole 102 formed in an annular throttle 68 formed between the outer peripheral surface of the rear end portion of the poppet 66 and the inner peripheral surface of the spring seat piston 60. The annular throttle 68 communicates with the spring seat piston chamber 64 via pressure oil circulation holes 103 and 104 formed in the poppet 66. The sleeve 51 between the spring receiving portion 66b and the spring seat piston 60 communicates with the low pressure chamber 56 and the oil chamber 75 defined between the spring receiving portion 66b and the spring seat piston 60. A hole 76 is formed. The oil chamber 73 formed between the annular protrusion 61 and the cap 72 and the oil chamber 75 are connected via pressure oil circulation grooves 74 and 74 (see FIG. 8) formed on the outer peripheral surface of the spring seat piston 60. Communicate with each other.

  Next, the operation of the relief valve according to the third embodiment of the present invention configured as described above will be described. The relief valve according to the third embodiment of the present invention is used, for example, as a relief valve for swing motor control of a hydraulic excavator, and after driving the upper swing body having a large inertia by operating the switch valve, the switch valve is returned to neutral to Assume that the revolving unit is decelerated to a stop. In this case, the oil that has flowed from the pressure oil inlet 52a of the housing 52 into the pressure oil circulation hole 57a of the valve seat 57 through the high pressure chamber 54, the pressure oil circulation holes 69 and 102 of the poppet 66, the annular throttle 68, the pressure oil circulation. It flows into the spring seat piston chamber 64 through the holes 103 and 104.

  In such a turning operation, the resistance on the discharge side of the switching valve may always be set relatively high in order to improve operability. Even in such a case, in the third embodiment of the present invention, whether or not the spring seat piston 60 moves to the left in FIG. It is determined by the difference in area between the rear end surface 66a and the front end surface 100a of the piston 100 facing the rear end surface 66a, that is, the oil pressure acting on the inner diameter step portion 60a of the spring seat piston 60.

  Therefore, if the area difference between the rear end surface 66a of the poppet 66 and the front end surface 100a of the piston 100 is set appropriately, the spring seat piston 60 can move even if the resistance on the discharge side of the switching valve is set to be relatively high. Absent.

  When the switching valve is returned to the neutral position, a brake pressure is generated on the discharge side of the switching valve, and this brake pressure becomes the pressure of the high pressure chamber 54 to operate the relief valve 50. In the third embodiment described above, In addition to the fact that the area difference between the rear end surface 66a of the poppet 66 and the front end surface 100a of the piston 100 can be made relatively small, the pressure of the low pressure chamber 56 acts on the rear end surface of the piston 100. The piston 100 is constantly pressed toward the cap 72 by the pressure difference between the pressure of the high pressure chamber 54 acting on the pressure and the pressure of the low pressure chamber 56 acting on the rear end surface of the piston 100. Therefore, since the volume of the spring seat piston chamber 64 when the spring seat piston 60 moves to the left in the figure is the area of the front end surface 100a of the piston 100 × stroke S, this can be set relatively large.

  The pressure oil circulation holes 102 and 103 described above can be configured as a small diameter throttle. Further, by adjusting the outer diameter of the poppet 66 at the portion where the annular diaphragm 68 is formed, the diaphragm effect can be set larger than that of the small-diameter diaphragm.

  FIG. 10 is a partial cross-sectional view showing the main part of the relief valve according to the fourth embodiment of the present invention. As shown in the figure, in the fourth embodiment of the present invention, instead of the piston 100 shown in FIG. 7, the first piston 110 and the second piston 112 are provided in the large-diameter inner diameter portion 60 c of the spring seat piston 60. Are slidably provided.

  The first piston 110 is disposed on the poppet 66 side, and a circular concave portion is formed on the front end surface of the first piston 110.

  On the other hand, the second piston 112 is arranged on the cap 72 side. Between the second piston 112 and the first piston 110, the front end of the first piston 110 is connected to the spring seat piston 60. A compression coil spring 111 that presses against the inner diameter step portion 60 a and presses the rear end of the second piston 112 against the cap 72 is provided.

  In addition, a plurality of pressure oil introduction grooves 116 are formed on the rear end surface of the second piston 112 from the center portion of the piston 112 toward the outer peripheral portion, and from the pressure oil circulation groove 74 of the spring seat piston 60 to the sleeve 51. The pressure oil that has flowed into the oil chamber 73 between the spring seat piston 60 flows through the pressure oil introduction groove 116 and flows into the oil chamber 114 formed between the cap 72 and the second piston 112, The pressure oil flowing into the oil chamber 114 flows through a throttle (small hole) 113 formed in the second piston 112 and an oil chamber 117 formed between the first piston 110 and the second piston 112. To flow into.

  According to such a configuration, when the pressure in the high pressure chamber 54 rises and pressure oil flows into the spring seat piston chamber 64, the first piston 110 is first pushed by the pressure oil in the spring seat piston chamber 64 in the drawing. After moving to the right, the spring seat piston 60 moves to the left in the figure. Therefore, even if the pressure in the high pressure chamber 54 suddenly increases, the spring seat piston 60 does not move immediately, and a time delay occurs in the movement of the spring seat piston 60. Therefore, after the pressure in the high pressure chamber 54 rises, the spring seat piston Until the 60 moves, the relief valve can be operated at a low pressure, so that the shock immediately after the operation of the relief valve can be greatly reduced.

  Therefore, even if the back pressure during the turning operation is relatively high, the movement of the spring seat piston 60 can be prevented, and the inflow per unit time of the pressure oil flowing from the high pressure chamber 54 into the spring seat piston chamber 64 by the annular restrictor 68. The amount can be set to be small, and the volume increase of the spring seat piston chamber 64 accompanying the movement of the spring seat piston 60 can be set relatively large. Therefore, the spring seat piston 60 is required to move the predetermined stroke S from the position shown in the figure. Time can be set relatively long. As a result, a shockless function can be reliably provided.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and many design changes can be made without departing from the spirit of the present invention.

It is a principal part cross-sectional side view which shows 1st Example of the relief valve which concerns on this invention. It is the II-II sectional view taken on the line of the relief valve shown in FIG. It is a principal part expanded sectional view of the relief valve shown in FIG. FIG. 2 is a hydraulic circuit diagram of a hydraulic motor device to which the relief valve shown in FIG. 1 is applied. It is a principal part sectional side view which shows 2nd Example of the relief valve which concerns on this invention. It is a principal part expanded sectional view of the relief valve shown in FIG. It is a principal part sectional side view which shows 3rd Example of the relief valve which concerns on this invention. FIG. 8 is a total sectional view taken along line VIII-VIII in FIG. 7. It is sectional drawing which shows the principal part structure of the relief valve shown in FIG. It is a principal part cross-sectional side view which shows 4th Example of the relief valve which concerns on this invention. It is explanatory drawing which shows schematic structure and the system arrangement | positioning of the structural example of the relief valve of the conventional hydraulic motor. It is a principal part expanded sectional view of the relief valve shown in FIG. It is principal part sectional drawing which shows another structural example of the pressure control valve which consists of a conventional relief valve.

Explanation of symbols

50 Relief valve 51 Sleeve 51a Inner diameter side surface 52 Housing 53 Inner diameter gap 54 High pressure chamber 56 Low pressure chamber 57 Seat 58 Sleeve 58a Stepped portion 58b Stepped portion 59 Side hole 60 Spring seat piston 60a Stepped portion 61 Knee portion 61a Shoulder portion 62 Spring seat Piston chamber 64 Oil chamber 64a, 64b Oil chamber 66 Poppet 67 Rod portion 68 Annular throttle 70 Spring 71 Spacer 72 Cap 74 Groove 75 Oil chamber 76 Hole 80 Pressure compensated flow control spool 81 Hook 82 Fixed throttle 83 Spring 84 Opening

Claims (2)

  When the oil pressure in the high pressure chamber rises, the poppet moves and opens against the elasticity of the spring against this, and is a differential direct acting relief valve configured to discharge the pressure oil in the high pressure chamber to the low pressure chamber. The spring seat piston with which the other end of the spring abuts is provided with a small-diameter inner diameter portion that slidably supports the rear end portion of the poppet and has a large diameter larger than the small-diameter inner diameter portion through the step portion. An inner diameter portion is provided, and a piston is slidably provided in the larger diameter inner diameter portion to define a spring seat piston chamber between the front end surface of the piston and the rear end surface of the poppet. Pressure oil in the high pressure chamber is introduced through an annular throttle formed between the outer peripheral surface of the poppet and the inner peripheral surface of the spring seat piston, and between the small diameter inner diameter portion and the large diameter inner diameter portion. The spring seat piston is formed by hydraulic pressure acting on the formed stepped portion. Relief valve, characterized by being configured so as to the emissions predetermined stroke movement.   A first piston whose one end surface is in contact with the stepped portion and a second piston disposed opposite to the other end side of the first piston are provided slidably on the large-diameter inner diameter portion of the spring seat piston, The oil chamber formed between the large-diameter inner diameter portion, the first piston, and the second piston is provided with a spring that biases the first piston toward the spring seat piston chamber, and the second piston The first piston is configured to move against the force of the spring when the pressure of the spring seat piston chamber is increased by providing a throttle for connecting the oil chamber to the low pressure chamber. The relief valve according to claim 1.

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