JP2010190315A - Relief valve for brake valve of traveling unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a relief valve for the brake valve of a traveling unit equipped with a free piston avoiding increase of a dimension of a member without damaging an operation function and braking force or stopping force (slope stop performance), maintaining a low pressure relief state, and extending shock-less time. <P>SOLUTION: The relief valve for the brake valve of the traveling unit includes a first space 79a formed on a back side of the free piston 78 in a case body 71 and communicated with a through-hole 76h of a rod 176 through a hole 76a provided on a rear end of the rod 176 in a position not closed by the free piston 78 even when the free piston 78 is in a rear end position; and an oil delivery hole and an oil delivery hole communication passage formed to communicate a second space 79b between a poppet in the case body 71 and the free piston 78 with a flow passage in downstream when an overload pressure is released. The relief valve further includes an overflow passage 180 communicating the first space 79a with the second space 79b, and the overflow passage 180 is closed when the free piston 78 is in a front end position. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a brake valve relief valve used in a traveling unit such as a hydraulic crawler vehicle, and more particularly to a brake valve relief valve having a free piston.

  In the brake valve of a hydraulic vehicle traveling unit, if the control valve is set to the neutral position when the vehicle decelerates or stops, the check valve stops the oil flow path to the hydraulic motor. The pressure of the oil on the side becomes negative, and the pressure of the oil on the return side instantaneously rises above the set pressure of the relief valve, which causes a shock to the vehicle when braking or stopping There was a problem like that.

Therefore, in order to reduce or eliminate a shock generated in the vehicle when the vehicle is braked or stopped, a relief valve for a brake valve having a free piston as disclosed in, for example, Japanese Patent Laid-Open No. 8-296604 (Patent Document 1) has been proposed. Yes.
Hereinafter, a conventional example of a relief valve for a brake valve provided with the above-described free piston will be described as background art of the present invention. In the embodiment of the present invention to be described later, the present invention is the same as the following conventional example except for matters that are different from the conventional example.

  FIG. 5 shows a relief valve for a brake valve provided with a conventional free piston. As shown in FIGS. 6 and 7, the relief valve 70 is used by incorporating two sets of relief valves 70 </ b> R and 70 </ b> L together with a pair of counter balance valves 60 in the brake valve 50. The brake valve 50 is provided between the control valve 40 for switching the hydraulic pressure from the hydraulic power source 30 and the hydraulic motor 20, and adjusts the operation such as braking and stopping. FIG. 4 shows a main part of a hydraulically driven crawler type vehicle travel drive device incorporating a travel unit in which the brake valve 50 is used.

  First, the hydraulic drive crawler type vehicle travel drive apparatus shown in FIG. 4 will be described. In FIG. 4, reference numeral 11 denotes a crawler shoe, and a number of crawler shoes 11 are connected endlessly to be freely bent to form an endless track. The crawler shoe 11 meshes with the teeth of the sprocket 12 fixed to the rotary casing 13 with bolts 12a, and the rotary casing 13 is connected to be driven by a hydraulic motor 20 via a speed reducer 14. The fixed casing 17 of the hydraulic motor 20 is fixed to the vehicle fixing frame 19 with bolts 17a. 50 is a brake valve. The traveling unit includes 14 parts of a speed reducer housed in the rotary casing 13, 20 parts of a hydraulic motor housed in the fixed casing 17, and 50 parts of a brake valve attached to the fixed casing.

  Next, the operation of the hydraulic drive crawler type vehicle travel drive apparatus shown in FIG. 4 will be described. Although not shown in FIG. 4, when hydraulic pressure is supplied to the hydraulic motor 20 from the hydraulic source 30 (see FIG. 6 or 7) provided in the vehicle body via the control valve 40 and the brake valve 50. The hydraulic motor 20 rotates. The rotation is decelerated and increased by the speed reducer 14 to rotate the rotating casing 13 and the sprocket 12, and the endless crawler shoe 11 meshing with the teeth of the sprocket 12 is driven to advance or reverse the vehicle.

Next, the hydraulic apparatus shown in FIGS. 6 and 7 will be described. 6 and 7, reference numeral 30 denotes a hydraulic pressure source. For example, a hydraulic pump 31 that is driven by an internal combustion engine to send out high-pressure hydraulic oil, a hydraulic pressure relief valve 32 that relieves hydraulic pressure from the hydraulic pump 31, and a reservoir (Oil tank) 33 and the like. A control valve 40 is connected to the flow paths K and M of the brake valve 50 by switching the reciprocating flow path from the hydraulic power source 30 to normal rotation, neutral and reverse rotation according to a command from a control device (not shown). In the brake valve body 52 of the brake valve 50, one set of counter balance valves 60 and two sets of relief valves 70R and 70L are provided. The counter balance valve 60 is provided with a spool 64, check valves 65R and 65L, springs 66R and 66L, and the like.
Next, the operation of the hydraulic apparatus shown in FIGS. 6 and 7 will be described. As shown in FIG. 6, when the control valve 40 is set to the neutral position, both the flow path K and the flow path M communicate with the return pipe line 34 and no pressure is applied. The spool 64 of the counter balance valve 60 is in a neutral position by both springs 66R and 66L, and the flow paths R and L are blocked by check valves 65R and 65L, respectively, so that oil does not flow freely from the hydraulic motor 20. This is to prevent such a situation because if the oil freely enters and exits the hydraulic motor 20, the vehicle may move freely due to external force, ground inclination, or the like.

  In the right position of the control valve 40 shown in FIG. 7, the hydraulic pressure enters the flow path K, the spool 64 is pushed from right to left, the pressure oil flows from the flow path K to the flow path R, and from the right of the hydraulic motor 20. It flows to the left and rotates, flows from the flow path L to the flow path M, and returns to the reservoir 33. Although not shown, at the left position of the control valve 40, oil flows in the opposite direction to that shown in FIG. 7, and the hydraulic motor 20 is driven to rotate in the direction opposite to the direction in FIG. When the overload pressure is generated in the flow path L, the relief valve 70R releases the overload pressure from the branch flow path Ld to the flow path R. The relief valve 70L releases the overload pressure from the branch channel Rd to the channel L when an overload pressure is generated in the channel R.

  Next, a brake valve relief valve provided with this conventional free piston shown in FIG. 5 will be described. As shown in FIGS. 6 and 7, relief valves 70 </ b> R and 70 </ b> L are incorporated in the brake valve body 52 of the brake valve 50. FIG. 5 shows the relief valve 70R, but the relief valve 70L has exactly the same structure except that the flow path R and the flow path L are opposite to each other. In FIG. 5, reference numeral 71 denotes a cartridge which is a cylindrical housing of the relief valve 70. As shown in FIGS. 6 and 7, the brake valve body 52 in which the flow path R and the flow path L of the brake valve 50 are formed. It is oil-tightly screwed in and incorporated. The flow path L and the flow path R are separated by bringing the tip of the relief valve 70 into close contact with each of the flow paths R and L where the branch flow paths Ld and Rd of the other flow path are connected. Is formed. As shown in the figure, the relief valve 70R is assembled so that the branch flow path Ld of the flow path L hits the tip of the relief valve 70R and the flow path R is in contact with the outer periphery of the tip of the relief valve 70R. The relief valve 70L has the same structure with the flow paths R and L reversed.

  As shown in FIG. 5, the opening of the relief valve 70R in the cartridge 71R is opened so that the opening to the branch flow path Ld and the opening in contact with the flow path R on the peripheral surface communicate with each other inside. A poppet seat 71b, which is a valve seat, is formed inside the opening with respect to the branch flow path Ld, and a poppet 73, which is a valve body that closes the flow path so as to be openable and closable with the poppet sheet 71b, is provided. . The poppet 73 is formed in a cylindrical shape, and the outer peripheral surface is in contact with the inner peripheral surface of the cartridge 71 so as to be slidable in the axial direction. A small hole (orifice) 73o penetrating from the front surface (tip surface) to the back surface of the poppet 73 is formed. Further, a rod 76 that is oil-tight and slidable in the axial direction is provided on the inner peripheral surface on the back side of the poppet 73. A rod through hole 76h that penetrates from the front end to the rear end is also formed in the center of the rod 76. A flange 76f is formed at an intermediate portion of the rod 76, and the poppet 73 is pushed between the rear end surface of the poppet 73 and the front end surface of the collar 76f so as to abut against the poppet sheet 71b with a predetermined force. A spring 72 is provided. The poppet spring 72 is given a predetermined elastic force as one element for setting an overload pressure to be released. In the illustrated example, the rear end surface of the rod 76 is formed into a spherical surface. A stopper 77 is provided at the rear end of the inner surface of the cartridge 71 of the relief valve 70 so as to receive the rear end of the rod 76. The stopper 77 can be adjusted in the axial direction by an adjusting screw 75a and an adjusting nut 75b, the axial position of the rod 76 received by the stopper 77 can be adjusted, and the poppet spring 72 pushed by the flange 76f of the rod 76 can be adjusted. The power can be adjusted. Assuming that the area due to the diameter of the poppet sheet 71b is A1, and the area due to the inner diameter of the poppet 73 or the outer diameter of the rod 76 that slides on the poppet 73 is A2, A1 is formed larger than A2 by a predetermined value.

  As shown in FIG. 5, a free piston 78 is provided in a free piston chamber 79 formed at the rear of the cartridge 71 so as to be freely movable in the axial direction. The outer peripheral surface of the free piston 78 is fitted into the inner peripheral surface of the cartridge 71 so as to be oil-tight and slidable, and is externally fitted to the outer peripheral surface of the rod 76 so as to be oil-tight and slidable. In a space equipped with a poppet spring 72 that communicates with the front chamber 78b of the free piston chamber 79, an oil drain hole 71d and an oil drain hole communication path 71e are formed so as to communicate with the flow path R. The rod through hole 76h opens to the rear chamber 79a of the free piston chamber 79 on the rear (right side of the drawing) side of the free piston 78 through a small hole 76a provided on the rear end side of the rod 76. The diameter of the rod 76 where the free piston 78 is externally fitted is smaller than the diameter of the rod 76 where the free piston 78 is internally fitted.

  Next, the operation of the brake valve relief valve shown in FIG. 5 will be described. Since the poppet 73 is closed by being pressed against the poppet seat 71b by the force of the poppet spring 72, the branch passage Ld is caused by the poppet 73R of the relief valve 70R unless the pressure exceeds a predetermined overload pressure in a normal operation state. Is closed and does not communicate with the flow path R. Similarly, the branch flow path Rd does not communicate with the flow path L by the poppet 73L of the relief valve 70L. For example, as shown in FIG. 7, when the control valve 40 is in the right position, high pressure oil enters the flow path K, the spool 64 of the counter balance valve 60 is pushed from right to left, and the high pressure from the hydraulic pump 31 enters the flow path R. When the oil flows to drive the hydraulic motor 20 and the flow path L is in communication with the return pipe 34 and the non-pressure return oil flows, the relief valve 70R has a flow as shown in FIG. The high-pressure oil in the path R flows into the front chamber 79b on the front side of the free piston 78 through the drain hole communicating passage 71e and the drain hole 71d, and presses the free piston 78 to the rear end. Although not shown as the relief valve 70L, as shown in FIG. 7, in the relief valve 70L, the high pressure oil in the branch flow path Rd passes through the small hole 73o, the rod through hole 76h, and the small hole 76a of the relief valve 70L. The free piston 78L enters the rear chamber 79a on the rear side, and the free piston 78 is pressed to the front end.

  When an overload high pressure occurs in the flow path R in the state shown in FIG. 7, the pressure that has entered the branch flow path Rd is applied to the front of the poppet 73L of the relief valve 70L (not shown), and the free piston 78L is shown in FIG. Since it exists in the position shown to b), the pressure which entered from the small hole 73o is applied also to the poppet back surface chamber 73p. Therefore, when the force obtained by multiplying the pressure by the area (A1-A2) exceeds the force of the poppet spring 72, the poppet 73L is pushed open, and the overload pressure escapes from the branch channel Rd to the channel L. That is, in this case, the operation is performed to release the overload pressure at the same high pressure as in the prior art. The above is the operation of the relief valve 70L (not shown), and the relief valve 70R does not operate.

However, when the control valve 40 is moved from the state shown in FIG. 7 to the neutral position shown in FIG. 6, both the flow paths K and M are connected to the return pipe 34 and no pressure is applied. The spool 64 is in the center position due to the balance between the spring 66R and the spring 66L, and the check valves 65R and 65L close the flow paths R and L so as to stop the flow of oil from the outlet side of the hydraulic motor 20.
The oil that has been flowing from the flow path R to the flow path L through the hydraulic motor 20 until now is suddenly stopped. However, since the oil tends to flow as before due to the inertial force of the mass movement of the vehicle body and the like, a high pressure is instantaneously generated in the flow path L and a negative pressure is generated in the flow path R. At that time, the free piston 78R of the relief valve 70R is at the rear end position of the free piston chamber 79, as shown in FIG. However, the flow path R has no pressure or negative pressure, and the front chamber 79b of the free piston 78 communicating with the flow path R through the oil drain hole communication passage 71e and the oil drain hole 71d is also no pressure or negative pressure. Therefore, when the high pressure instantaneously generated in the flow path L due to the sudden stop is applied to the front surface of the poppet 73R of the relief valve 70R from the branch flow path Ld, the pressure that has entered the poppet back chamber 73p through the small hole 73o is: The free piston 78R enters the rear chamber 79a through the rod through hole 76h and the small hole 76a. The free piston 78R easily moves to the left because the front surface 79b has no pressure, and enters the poppet back surface chamber 73p. There is no pressure. Therefore, the pressure from the branch channel Ld is applied to the area A1 and pushes the poppet 73. If this force exceeds the force of the poppet spring 72, the poppet 73 is pushed open and the pressure in the branch flow path Ld escapes to the flow path R. Since the pressure applied to the area A1, that is, the low pressure applied to the area A1 larger than the area (A1-A2) is released, the instantaneous high pressure is released sufficiently to prevent the occurrence of impact and vibration.

  However, due to the pressure entering through the small hole 73o, the rod through hole 76h, and the small hole 76a, the free piston 78 is immediately at the position shown in FIGS. 5 (a) to 5 (b). After the free piston 78 reaches the position shown in FIG. 5B, the same pressure as the front surface is applied to the poppet back chamber 73p, and the force pushing the poppet 73 is a force obtained by multiplying the pressure by the area (A1-A2). If the pressure is not high, the poppet 73 cannot be pushed open, and desired braking and stopping capabilities can be exhibited.

  The operation when the control valve 40 shown in FIG. 7 is changed from the right position to the neutral position in FIG. 6 has been described. The operation when the control valve 40 is changed from the left position to the neutral position in FIG. Since it is easily understood that the flow path R and the flow path L are changed, and that the relief valve 70R and the relief valve 70L are changed and perform the same operation, the drawings and description are omitted.

  Since the diameter of the portion of the rod 76 fitted into the poppet 73 is equal to or larger than the diameter of the portion fitted into the free piston 78, the position of the rod 76 is stabilized. Further, when the rear end of the rod 76 is a spherical surface, an extra twisting force is not applied.

  According to the relief valve for a brake valve equipped with the conventional free piston as described above, the occurrence of shock and vibration is suppressed by releasing the instantaneous overload pressure generated immediately after switching the control valve with a free piston at a low pressure. After that, since the relief pressure is set to a high setting state, the braking force and the stopping force can be exhibited.

JP-A-8-296604 (pages 3-5, FIGS. 1-4)

However, the brake valve relief valve 70 provided with the conventional free piston 78 described above is such that when the vehicle is decelerated or stopped, the brake valve relief valve 70 can release the overload pressure with a low pressure. It is from the time when 78 is at the rear end position before movement (right end position in FIG. 5) to the front end position after movement (left end position in FIG. 5), that is, until moving to the stroke end, and the shockless time is Because the length is short and the high relief pressure set for steady braking and stopping force can not be released sufficiently, the occurrence of impact and vibration may not be sufficiently prevented. There was a problem that there was.
Thus, it is conceivable to improve the free piston chamber 79 by increasing the capacity of the free piston chamber 79. However, the capacity of the free piston chamber 79 is limited due to the layout, and it is difficult to improve sufficiently. .

  In the relief valve for a brake valve having a free piston, the present invention avoids an increase in member dimensions and maintains a low pressure relief state without impairing the operation function and braking force or stopping force (slope staying performance, etc.). It is an object of the present invention to provide a relief valve for a brake valve of a traveling unit that can extend a shockless time.

  The present invention has been made to solve the above problems, and provides the following means (1) to (5), and will be described below in the order of the claims.

  (1) As the first means, a casing in which a fluid flow path and a valve seat are formed, and a small hole penetrating from the front surface to the back surface is provided, and provided in the casing so as to be slidable in the axial direction. It has a poppet, a poppet spring that presses the poppet against the valve seat, and a through hole that penetrates from the front end to the rear end, and the outer peripheral surface of the front end slides in an oil-tight and axial direction inside the cylindrical part on the back of the poppet The rear end of the rod is formed so as to be received by a stopper at the rear of the casing, and the rear end position of the rod is fitted to the inner peripheral surface of the casing. And a free piston provided in an oil-tight and axially slidable manner between the front end position and the rear end of the free piston inside the housing. In the position where it is not blocked by the free piston Overload pressure is released through a first space communicating with the through hole through a hole provided at a rear end of the lid and a second space between the poppet and the free piston in the housing. In a relief valve for a brake valve of a traveling unit comprising an oil drain hole and an oil drain hole communication passage formed so as to communicate with a downstream flow path, the first space and the second space are A relief valve for a brake valve of a traveling unit is provided, characterized in that the relief passage is provided with a communicating fluid passage, and the fluid passage is configured to be closed when the free piston is in a front end position.

  (2) As a second means, in the relief valve for a brake valve of the traveling unit of the first means, the escape passage is configured to be closed when the free piston is at the rear end position. A relief valve for a brake valve of a traveling unit is provided.

  (3) As a third means, in the relief valve for a brake valve of the traveling unit of the second means, the escape channel is a notch provided in the outer peripheral surface of the rod so as to extend in the axial direction. The rear end of the notch is in a position closed by the inner peripheral surface of the free piston when the free piston is in the rear end position, and the front end of the notch is the inner side of the free piston when the free piston is in its front end position. A traveling unit provided so as to be in a position closed by a peripheral surface, wherein a distance in a rod axial direction between a rear end and a front end of the notch is longer than a length in a rod axial direction of an inner peripheral surface of the free piston. Relief valve for brake valve

  (4) As a fourth means, in the relief valve for a brake valve of the traveling unit of the second means, the escape passage is provided in the free piston and communicates with the first space and the second space. The rear end opening of the communication hole is at a position closed by the rear wall surface of the first space when the free piston is at the rear end position, and the front end opening of the communication hole is the front end of the free piston. A relief valve for a brake valve of a traveling unit is provided, wherein the relief valve is provided so as to be closed by a front wall surface of the second space.

  (5) As a fifth means, in the relief valve for a brake valve of the traveling unit of the second means, the escape channel is a spiral groove provided extending in the axial direction on the outer peripheral surface of the rod, The rear end of the spiral groove is in a position closed by the inner peripheral surface of the free piston when the free piston is in the rear end position, and the front end of the spiral groove is free when the free piston is in the front end position. A rod axial direction distance between a rear end and a front end of the spiral groove is longer than a rod axial direction length of the inner surface of the free piston. A relief valve for a brake valve of a traveling unit is provided.

(1) According to the first aspect of the present invention, since the brake valve relief valve of the traveling unit is configured as the first means, the free piston is at the rear end position. The time required to reach the front end position, that is, the shockless time when the relief valve for the brake valve can release the overload pressure at a low pressure, can be extended, and the overload pressure can be released sufficiently. Then, it is possible to sufficiently prevent the occurrence of impact and vibration, which can be set to a re-high leaf pressure set for steady braking force and stopping force.
In addition, since the escape channel is closed at the front end position of the free piston, the setting and operation of the high pressure relief is not impaired.

  (2) According to the invention of claim 2 of the claims, since the relief valve for a brake valve of the traveling unit is configured as the second means, in addition to the effect of the invention of claim 1, Since the escape channel is blocked even at the rear end position of the free piston, the front chamber side of the free piston chamber can be maintained at a higher pressure than the rear chamber side during normal operation, and the maintenance of the free piston at the rear end position is impaired. In addition, there is no oil leakage from the free piston chamber, and the locking performance that prevents drift on a slope when the vehicle is stopped is not impaired.

  (3) According to the invention of claim 3 of the claims, since the brake valve relief valve of the traveling unit is configured as the third means, in addition to the effect of the invention of claim 2, Since the escape channel is formed with a notch, the structure is simple and maintenance is easy.

  (4) According to the invention of claim 4 of the claims, since the relief valve for a brake valve of the traveling unit is configured as the fourth means, in addition to the effect of the invention of claim 2, It is easy to provide an appropriate orifice portion in the communication hole serving as the escape channel.

  (5) According to the invention of claim 5 of the claims, since the relief valve for a brake valve of the traveling unit is configured as the fifth means, in addition to the effect of the invention of claim 2, Since the escape channel is a spiral groove, drilling is not required and machining is easy, and since the escape channel can be set longer, the groove size for a given orifice effect can be increased, preventing clogging, etc., and easy maintenance It is.

FIG. 6 is a longitudinal sectional view schematically showing a portion corresponding to part A in FIG. 5 of the brake valve relief valve of the traveling unit according to the first embodiment of the present invention, in which (a) shows a free piston when braking or stopping; In the moving state, (b) shows the state of the free piston after the movement by a solid line and the state before the movement by a two-dot chain line. FIG. 6 is a longitudinal sectional view schematically showing a portion corresponding to part A in FIG. 5 of a relief valve for a brake valve of a traveling unit according to Embodiment 2 of the present invention, where (a) shows a free piston when braking or stopping. In the moving state, (b) shows the state of the free piston after the movement by a solid line and the state before the movement by a two-dot chain line. FIG. 6 is a longitudinal sectional view schematically showing a portion corresponding to part A in FIG. 5 of a relief valve for a brake valve of a traveling unit according to Embodiment 3 of the present invention, in which (a) shows a free piston when braking or stopping. In the moving state, (b) shows the state of the free piston after the movement by a solid line and the state before the movement by a two-dot chain line. It is a principal part schematic diagram of the traveling drive apparatus of a hydraulic drive crawler type vehicle. 1 shows a relief valve for a brake valve having a conventional free piston, wherein (a) is a longitudinal sectional view when the flow path R is at a high pressure, and (b) is a longitudinal sectional view when the flow path R is at a low pressure. It is a figure which shows the state at the time of neutral of the hydraulic system which has a relief valve for brake valves provided with the conventional free piston. It is a figure which shows the state at the time of driving | running | working of the hydraulic system which has the relief valve for brake valves provided with the conventional free piston.

  Examples 1 to 3 will be described below as modes for carrying out the present invention.

  A relief valve for a brake valve of a traveling unit according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a longitudinal sectional view schematically showing a portion corresponding to the portion A in FIG. 5 of the brake valve relief valve of the traveling unit of the present embodiment. FIGS. 6 and 7 are the same as the relief valve 70R of FIG. The relief valve 170R arranged on the middle right side is illustrated, (a) is a state where the free piston is moving at the time of braking or stopping, (b) is a state before the movement of the free piston after the above movement, and is a state before the movement Is shown by a two-dot chain line.

  The first embodiment is the same as the brake valve relief valve and the traveling drive device described in the conventional example except that the configuration of the rod is different, and the illustration is omitted. FIG. 1 is a schematic diagram for explaining different parts. Detailed shapes of cartridges, rods, etc., and illustration of members (for example, collar 76f, poppet spring 72, etc.) are omitted. It is the same as what was demonstrated in FIGS. 4-7, and FIGS. 4-7 is referred. The parts described in the conventional example are assigned the same reference numerals and the description thereof is omitted, and the parts according to the present embodiment are assigned reference numerals in the 100s with the same last two digits to clarify the relationship.

As shown in FIG. 1, the rod 176 of the relief valve 170R of this embodiment is provided with one or more notches (vertical grooves) 180 extending in the axial direction on the outer peripheral surface thereof, and a rear end 180a (FIG. 1). When the free piston 78 is at the rear end position (right end position in FIG. 1) as shown by a two-dot chain line in FIG. 1B, the free piston 78 is covered and closed by the inner peripheral surface. When the free piston 78 is at the front end position (left end position in FIG. 1) as shown by the solid line in FIG. 1 (b), the front end 180b (left end in FIG. 1) is at the inner periphery of the free piston 78. It is in a position to be covered and closed.
Further, the length of the notch 180 in the rod axis direction, that is, the rod axis direction distance m1 between the rear end 180a and the front end 180b is longer than the length n1 of the inner circumferential surface of the free piston 78.
One or a plurality of notches 180, their cross-sectional shape dimensions, and the like are appropriately set so as to obtain the required flow rate and throttling effect.

When the rear end of the rod 176 has a spherical surface, an extra twisting force is not applied.
The rod 176 is disposed at a position where the free piston 78 is not covered by the free piston 78 when the free piston 78 is at the rear end position, and a rear chamber 79a of the free piston chamber 79 on the rear side (right side in the drawing) of the rod through hole 76h. The small hole 76a which connects these. The single or plural small holes 76a, their cross-sectional shape dimensions, and the like are appropriately set so as to obtain the required flow rate and throttling effect.

  The operation of the relief valve 170R of this embodiment will be described. As explained in the conventional example, during normal operation by applying hydraulic pressure to the flow path R, the free piston 78 of the relief valve 170R is at the rear end position as shown by a two-dot chain line in FIG. When the control valve 40 is set to the neutral position for braking or stopping, the oil that has been flowing from the flow path R to the flow path L through the hydraulic motor 20 until then is suddenly stopped, and the inertia of the movement of the vehicle body and other masses. Since the oil tends to flow as before due to the force, a high pressure is instantaneously generated in the flow path L, a negative pressure is generated in the flow path R, and the front chamber in front of the free piston 78 communicating with the flow path R 79b also has no pressure or negative pressure. Therefore, the high pressure instantaneously generated in the flow path L by the sudden stop is applied from the branch flow path Ld to the front surface of the poppet 73R of the relief valve 170R, and passes through the orifice 73o, the rod through hole 76h, and the small hole 76a to After entering the rear rear chamber 79a, the free piston 78 tends to move easily in the direction of the white arrow (leftward) in FIG. 1A because there is no pressure on the left side and the front chamber 79b side.

  However, in the case of this embodiment, the rod 176 is provided with a notch 180 in the axial direction of the outer peripheral surface to form an escape channel between the rear chamber 79a and the front chamber 79b. The oil a that has flowed into the rear chamber 79a of the engine 79 immediately after pushing the free piston 78 in a state indicated by a two-dot chain line in FIG. 1 (b) forward (to the left in the drawing) As shown, the rear end 180a of the notch 180 opens into the rear chamber 79a, and the partial oil a1 flows through the notch 180 into the front chamber 79b, so that the movement of the free piston 78 is slowed.

  Eventually, when the free piston 78 approaches its front end position (left end position in the figure) indicated by a solid line in FIG. 1B, the front end 180b of the notch 180 is covered with the inner peripheral surface of the free piston 78 and closed. The flow of the oil passing through stops, and the free piston 78 stops at the front end position as shown by the solid line in FIG. 1B, and thereafter moves to the state of setting the high pressure relief.

  Accordingly, the movement time from when the free piston 78 is at the rear end position to the arrival at the front end position, that is, the shockless time during which the relief valve for the brake valve can release the overload pressure at a low pressure is extended. Thus, the overload pressure can be released sufficiently, and then the high relief pressure set for steady braking force and stopping force is obtained, so that the occurrence of impact and vibration can be sufficiently prevented.

Moreover, since the escape channel by the notch 180 is closed at the front end position of the free piston 78, the setting and operation of the high pressure relief is not impaired.
Further, since the escape flow path by the notch 180 is also closed at the rear end position of the free piston 78, the front chamber 79b side of the free piston chamber 79 can be maintained at a higher pressure than the rear chamber 79a side during normal operation. There is no loss of maintaining the rear end position.
Accordingly, there is no oil leakage from the free piston chamber 79, and the locking performance for preventing drift on a slope when the vehicle is stopped is not impaired.

  As described above, the present embodiment has been illustrated and described as the relief valve 170R disposed on the right side in FIGS. 6 and 7 in the same manner as the relief valve 70R in FIG. 5, but the relief valve disposed on the left side in FIGS. By simply reversing the paths R and L, the relief valve 170R can be constructed in exactly the same manner, and the same effect can be obtained.

  Since the relief valve for a brake valve of the traveling unit of the first embodiment is configured and operates as described above, the member size can be increased without impairing the operation function and the braking force or stopping force (slope retention performance, etc.). It can be avoided and the low pressure relief state can be maintained to extend the shockless time. Further, since the notch 180 forms an escape channel between the rear chamber 79a and the front chamber 79b, the structure is simple and maintenance is easy.

  Based on FIG. 2, a brake valve relief valve for a traveling unit according to a second embodiment of the present invention will be described. FIG. 2 is a longitudinal sectional view schematically showing a portion corresponding to the portion A in FIG. 5 of the brake valve relief valve of the traveling unit of the present embodiment. FIG. 6 and FIG. 7 are the same as the relief valve 70R of FIG. The relief valve 270R arranged on the middle right side is illustrated, (a) is a state in which the free piston is moving at the time of braking or stopping, (b) is a state before the movement of the free piston after the movement, shown by a solid line Is shown by a two-dot chain line.

  The second embodiment is the same as the brake valve relief valve and travel drive device described in the conventional example except that the configuration of the free piston is different, and the illustration is omitted. FIG. 2 is a schematic diagram for explaining different parts. Detailed shapes of cartridges, rods, etc., and illustration of members (for example, collar 76f, poppet spring 72, etc.) are omitted. It is the same as what was demonstrated in FIGS. 4-7, and FIGS. 4-7 is referred. The parts described in the conventional example are assigned the same reference numerals and the description thereof is omitted, and the parts according to the present embodiment are assigned the reference numerals in the 200s with the same last two digits to clarify the relationship.

  As shown in FIG. 2, the free piston 278 of the relief valve 270R of the present embodiment is provided with one or a plurality of communication holes 281 that communicate the rear chamber 79a and the front chamber 79b of the free piston chamber 79 in the axial direction of the rod 76. The communication hole 281 has an orifice portion 282.

The communication hole 281 is free at the rear end opening 281a (right end in FIG. 2) when the free piston 278 is at the rear end position (right end position in FIG. 2) as shown by a two-dot chain line in FIG. 2 (b). The front end opening 281b (left end in FIG. 2) of the piston chamber 79 is closed by the rear wall 79c of the rear chamber 79a, and the free piston 278 has a front end position (as shown by a solid line in FIG. 2B) ( 2, the position is closed by the front wall surface 79d of the front chamber 79b of the free piston chamber 79.
One or a plurality of communication holes 281, the orifice portion 282, and the like are appropriately set so as to obtain a desired flow rate and a throttling effect. It is also possible to omit providing the special orifice portion 282 by setting the communication hole 281 itself to have a predetermined orifice effect.

When the rear end of the rod 76 is spherical, an extra twisting force is not applied.
The rod 76 is located at a position where the free piston 278 is not covered by the free piston 278 when the free piston 278 is at the rear end position, and a rear piston 79 of the free piston chamber 79 on the rear side (right side of the drawing) of the rod through hole 76h. The small hole 76a which connects these. The single or plural small holes 76a, their cross-sectional shape dimensions, and the like are appropriately set so as to obtain the required flow rate and throttling effect.

  The operation of the relief valve 270R of this embodiment will be described. As described in the conventional example, during normal operation by applying hydraulic pressure to the flow path R, the free piston 278 of the relief valve 270R is at the rear end position as shown by a two-dot chain line in FIG. When the control valve 40 is set to the neutral position for braking or stopping, the oil that has been flowing from the flow path R to the flow path L through the hydraulic motor 20 until then is suddenly stopped, and the inertia of the movement of the vehicle body and other masses. Since the oil tends to flow as before due to the force, a high pressure is instantaneously generated in the flow path L, a negative pressure is generated in the flow path R, and the front chamber in front of the free piston 278 communicating with the flow path R 79b also has no pressure or negative pressure. Therefore, the high pressure instantaneously generated in the flow path L by the sudden stop is applied from the branch flow path Ld to the front surface of the poppet 73R of the relief valve 270R, and passes through the orifice 73o, the rod through hole 76h, and the small hole 76a to After entering the rear rear chamber 79a, the free piston 278 tends to easily move in the direction of the white arrow (leftward) in FIG. 2A because there is no pressure on the left side and the front chamber 79b side.

However, in the case of this embodiment, the free piston 278 is provided with a communication hole 281 having an orifice portion 282 in the rod axis direction to form a return channel between the rear chamber 79a and the front chamber 79b. As soon as the oil a flowing into the rear chamber 79a of the free piston chamber 79 from the hole 76a pushes the free piston 278 in the state shown by the two-dot chain line in FIG. 2B forward (to the left in the figure), FIG. As shown in (a), the rear end 281a of the communication hole 281 opens into the rear chamber 79a, and part of the oil a1 flows through the communication hole 281 via the orifice portion 282 to the front chamber 79b, so that the free piston 278 Move slower.

  Eventually, when the free piston 278 is positioned at its front end position (left end position in the figure) as shown by a solid line in FIG. 2B, the front end opening 281b of the communication hole 281 is located in front of the front chamber 79b of the free piston chamber 79. The oil flow blocked by the wall surface 79d and passing through the communication hole 281 is stopped, and the free piston 278 is stopped at the front end position as shown by the solid line in FIG. 2B, and thereafter the high pressure relief is set. Move.

  Therefore, the movement time from when the free piston 278 is at the rear end position to the arrival at the front end position, that is, the shockless time during which the relief valve for the brake valve can release the overload pressure at a low pressure is extended. Thus, the overload pressure can be released sufficiently, and then the high relief pressure set for steady braking force and stopping force is obtained, so that the occurrence of impact and vibration can be sufficiently prevented.

In addition, since the escape passage by the communication hole 281 is closed at the front end position of the free piston 278, the setting and operation of the high pressure relief is not impaired.
In addition, since the escape channel by the communication hole 281 is also closed at the rear end position of the free piston 278, the front chamber 79b side of the free piston chamber 79 can be maintained at a higher pressure than the rear chamber 79a side during normal operation. Is maintained in the rear end position.
Accordingly, there is no oil leakage from the free piston chamber 79, and the locking performance for preventing drift on a slope when the vehicle is stopped is not impaired.

  Although the present embodiment has been illustrated and described as the relief valve 270R disposed on the right side in FIGS. 6 and 7 in the same manner as the relief valve 70R in FIG. 5, the relief valve disposed on the left side in FIGS. By simply reversing the paths R and L, the relief valve 270R can be configured in exactly the same manner, and the same effects can be obtained.

  Since the brake valve relief valve of the traveling unit of the second embodiment is configured and operates as described above, the increase in the member dimensions can be achieved without impairing the operation function and the braking force or stopping force (slope retention performance, etc.). It can be avoided and the low pressure relief state can be maintained to extend the shockless time. Further, since the communication hole 281 is provided in the free piston 278 to form the escape channel between the rear chamber 79a and the front chamber 79b, it is possible to provide an appropriate orifice portion 282 in the communication hole serving as the escape channel. Easy.

  Based on FIG. 3, a brake valve relief valve for a traveling unit according to a third embodiment of the present invention will be described. FIG. 3 is a longitudinal sectional view schematically showing a portion corresponding to the portion A in FIG. 5 of the brake valve relief valve of the traveling unit of the present embodiment. FIG. 6 and FIG. 7 are the same as the relief valve 70R of FIG. The relief valve 370R arranged on the middle right side is illustrated, (a) is a state in which the free piston is moving at the time of braking or stopping, (b) is a state before the movement of the free piston after the movement, in a solid line Is shown by a two-dot chain line.

  The third embodiment is the same as the brake valve relief valve and the travel drive device described in the conventional example except that the configuration of the rod is different, and the illustration is omitted. FIG. 3 is a schematic diagram for explaining different parts. Detailed shapes of cartridges, rods, etc., and illustration of members (for example, collar 76f, poppet spring 72, etc.) are omitted. It is the same as what was demonstrated in FIGS. 4-7, and FIGS. 4-7 is referred. The parts described in the prior art are given the same reference numerals and the description thereof is omitted, and the parts according to the present embodiment are given the reference numbers in the 300s with the same last two digits to clarify the relationship.

As shown in FIG. 3, the rod 376 of the relief valve 370R of the present embodiment is provided with one or a plurality of spiral grooves 383 extending in the axial direction of the outer peripheral surface thereof, and a rear end 383a (in FIG. When the free piston 78 is at the rear end position (right end position in FIG. 3) as shown by a two-dot chain line in FIG. The front end 383b (the left end in FIG. 3) is located on the inner peripheral surface of the free piston 78 when the free piston 78 is at the front end position (the left end position in FIG. 3) as shown by the solid line in FIG. It is in a position to be covered and closed.
Further, the length of the spiral groove 383 in the rod axis direction, that is, the rod axis direction distance m3 between the rear end 383a and the front end 383b is longer than the rod axis direction length n3 of the inner peripheral surface of the free piston 78.
One or a plurality of spiral grooves 383, their cross-sectional shape dimensions, inclinations, and the like are appropriately set so as to obtain the required flow rate and throttling effect.

When the rear end of the rod 376 is formed into a spherical surface, an excessive twisting force is not applied.
The rod 376 is disposed at a position where the free piston 78 is not covered by the free piston 78 when the free piston 78 is at the rear end position, and a rear chamber 79a of the free piston chamber 79 on the rear (right side of the drawing) side of the rod through hole 76h. The small hole 76a which connects these. The single or plural small holes 76a, their cross-sectional shape dimensions, and the like are appropriately set so as to obtain the required flow rate and throttling effect.

  The operation of the relief valve 370R of this embodiment will be described. As described in the conventional example, during normal operation by applying hydraulic pressure to the flow path R, the free piston 78 of the relief valve 370R is at the rear end position as shown by a two-dot chain line in FIG. When the control valve 40 is set to the neutral position for braking or stopping, the oil that has been flowing from the flow path R to the flow path L through the hydraulic motor 20 until then is suddenly stopped, and the inertia of the movement of the vehicle body and other masses. Since the oil tends to flow as before due to the force, a high pressure is instantaneously generated in the flow path L, a negative pressure is generated in the flow path R, and the front chamber in front of the free piston 78 communicating with the flow path R 79b also has no pressure or negative pressure. Therefore, the high pressure instantaneously generated in the flow path L by the sudden stop is applied from the branch flow path Ld to the front surface of the poppet 73R of the relief valve 370R, and passes through the orifice 73o, the rod through hole 76h, and the small hole 76a to After entering the rear rear chamber 79a, the free piston 78 tends to easily move in the direction of the white arrow (leftward) in FIG. 3A because there is no pressure on the left side and the front chamber 79b side.

  However, in the case of this embodiment, the rod 376 is provided with a spiral groove 383 extending in the surface axial direction to form a flow path between the rear chamber 79a and the front chamber 79b. Oil a that has flowed into the rear chamber 79a of the free piston chamber 79 will soon be pushed forward (to the left in the figure) in a state indicated by a two-dot chain line in FIG. As shown in a), the rear end 383a of the spiral groove 383 opens into the rear chamber 79a, and a part of the oil a1 flows through the spiral groove 383 to the front chamber 79b, so that the movement of the free piston 78 becomes slow.

  Eventually, when the free piston 78 approaches its front end position (left end position in the figure) indicated by a solid line in FIG. 3B, the front end 383 b of the spiral groove 383 is covered with the free piston 78 and the oil passing through the spiral groove 383 is removed. While the flow stops, the free piston 78 stops at the front end position as shown by the solid line in FIG. 3B, and thereafter moves to the high pressure relief setting state.

  Accordingly, the movement time from when the free piston 78 is at the rear end position to the arrival at the front end position, that is, the shockless time during which the relief valve for the brake valve can release the overload pressure at a low pressure is extended. Thus, the overload pressure can be released sufficiently, and then the high relief pressure set for steady braking force and stopping force is obtained, so that the occurrence of impact and vibration can be sufficiently prevented.

In addition, since the escape channel by the spiral groove 383 is closed at the front end position of the free piston 78, the setting and operation of the high pressure relief is not impaired.
In addition, since the escape channel by the spiral groove 383 is also closed at the rear end position of the free piston 78, the front chamber 79b side of the free piston chamber 79 can be maintained at a higher pressure than the rear chamber 79a side during normal operation. Is maintained in the rear end position.
Accordingly, there is no oil leakage from the free piston chamber 79, and the locking performance for preventing drift on a slope when the vehicle is stopped is not impaired.

  As described above, the present embodiment has been exemplified and described as the relief valve 370R disposed on the right side in FIGS. 6 and 7 in the same manner as the relief valve 70R in FIG. 5, but the relief valve disposed on the left side in FIGS. By simply reversing the paths R and L, the relief valve 370R can be constructed in exactly the same manner, and the same effects can be obtained.

  Since the brake valve relief valve of the traveling unit of the third embodiment is configured and operates as described above, the increase in the member dimensions can be achieved without impairing the operation function and the braking force or stopping force (slope retention performance, etc.). It can be avoided and the low pressure relief state can be maintained to extend the shockless time. In addition, since the spiral groove 383 forms a return channel between the rear chamber 79a and the front chamber 79b, drilling is not required and processing is facilitated. The groove size for the orifice effect can be increased, dust clogging can be prevented, and maintenance is easy.

  The present invention has been described with reference to the illustrated embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications may be made to the specific structure and configuration within the scope of the present invention. Nor.

  The relief valve for a brake valve of the traveling unit of the present invention is not limited to the traveling unit, and it is required to prevent the occurrence of an impact or vibration during deceleration or stop, as well as the traveling unit, while maintaining the braking force and the stopped state during the stop. It can be effectively used as a relief valve for a brake valve of a hydraulic drive unit that requires force.

20 Hydraulic motor 30 Hydraulic source 40 Control valve 50 Brake valve 60 Counter balance valve 70R, 170R, 270R, 370R Relief valve 71 Cartridge 76, 176, 376 Rod 76a Small hole 76h Rod through hole 77 Stopper 78, 278 Free piston 79 Free piston Chamber 79a Rear chamber 79b Front chamber 180 Notch 281 Communication hole 282 Orifice portion 383 Spiral groove

Claims (5)

A housing in which a fluid flow path and a valve seat are formed;
A poppet provided with a small hole penetrating from the front surface to the back surface and slidable in the axial direction in the housing;
A poppet spring that presses the poppet against the valve seat;
It has a through-hole penetrating from the front end to the rear end, and the outer peripheral surface of the front end portion is formed in an oil-tight and axially slidable manner in the cylindrical portion on the back of the poppet, and the rear end is a stopper at the rear portion of the casing A rod provided to be received by
A free piston that is externally fitted to the rear outer peripheral surface of the rod, is fitted to the inner peripheral surface of the housing, and is slidable between the rear end position and the front end position in an oil-tight manner in the axial direction;
Formed on the rear side of the free piston inside the housing, through a hole provided in the rear end portion of the rod at a position where the free piston is not blocked by the free piston even when the free piston is at the rear end position. A first space communicating with the through hole;
An oil drain hole and a drain hole communicating path formed so as to communicate the second space between the poppet in the housing and the free piston to the downstream flow path when the overload pressure is released. ,
In a relief valve for a brake valve of a traveling unit comprising:
A traveling unit comprising: a flow path communicating with the first space and the second space, wherein the flow path is configured to be closed when the free piston is at a front end position. Relief valve for brake valve.   2. The relief valve for a brake valve of a traveling unit according to claim 1, wherein the escape passage is configured to be closed when the free piston is at a rear end position. The escape channel is a notch provided on the outer peripheral surface of the rod so as to extend in the axial direction, and the rear end of the notch is closed by the inner peripheral surface of the free piston when the free piston is at the rear end position. And the front end of the notch is provided so as to be in a position closed by the inner peripheral surface of the free piston when the free piston is in its front end position,
The relief valve for a brake valve of a travel unit according to claim 2, wherein a distance in the rod axial direction between the rear end and the front end of the notch is longer than a length in the rod axial direction of the inner peripheral surface of the free piston.   The escape channel is a communication hole that is provided in the free piston and communicates the first space and the second space, and a rear end opening of the communication hole is formed when the free piston is at a rear end position. The front end opening of the communication hole is provided at a position closed by the front wall surface of the second space when the free piston is at the front end position. The relief valve for a brake valve of a traveling unit according to claim 2. The escape channel is a spiral groove extending in the axial direction on the outer peripheral surface of the rod, and the rear end of the spiral groove is the inner peripheral surface of the free piston when the free piston is at the rear end position. The front end of the spiral groove is provided so as to be closed by the inner peripheral surface of the free piston when the free piston is in its front end position.
The relief valve for a brake valve of a traveling unit according to claim 2, wherein a distance in the rod axial direction between the rear end and the front end of the spiral groove is longer than the length in the rod axial direction of the inner peripheral surface of the free piston.

Images