JP2009024733A - Braking system of hydraulic motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a braking system of a hydraulic motor for surely bleeding air in an oil path for supplying a pilot pressure with a spool. <P>SOLUTION: This braking system of a hydraulic motor drains a pressure oil supplied to a pump port 39 from bypass oil paths 40a, 41a, 42a via a pilot pressure oil path 82, and discharges air in the pilot pressure oil path by the drained pressure oil, when a pilot pressure switch valve 80 makes inside of the pilot pressure oil path 82 to a drainage pressure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a friction braking type brake system used for a hydraulic motor.

As a friction braking type brake system used for a hydraulic motor, a fixed plate provided on a non-rotating body, a rotating plate provided on the rotating body, and a coil spring that presses the rotating plate against the fixed plate via a piston (For example, refer to Patent Document 1)
In this brake device, a friction brake force is generated between the rotating plate and the fixed plate by the biasing force of the coil spring to stop the rotating body. Release of the braking force is performed by moving the piston against the urging force of the coil spring using hydraulic pressure.

  For this reason, in Patent Document 1, a brake release hydraulic pressure switching valve for controlling the release of the brake force is provided. This hydraulic pressure switching valve causes the hydraulic pressure from the pump to act on the piston of the brake device according to the position of the spool that moves according to the supplied pilot pressure.

Thus, the release of the braking force is performed by compressing the coil spring by the action of the hydraulic switching valve and releasing the frictional force between the rotating plate and the fixed plate.
JP 2002-39047 A

  The pilot pressure oil passage that supplies the signal pressure to the spool of the hydraulic switching valve is configured such that the pressure oil is drained to the tank when the drive pressure from the hydraulic pump is not supplied. However, one end of the pilot pressure oil passage is only opened in the tank, and so-called air venting for removing air remaining in the pilot pressure oil passage may be insufficient. When air bleeding is insufficient, the brake pressure release timing is delayed as the pilot pressure rises, and the brake motor is accelerated by the rotation of the hydraulic motor, resulting in a problem that the service life is shortened.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to reliably carry out air bleeding of a brake system in a brake system of a hydraulic motor.

  The present invention relates to a brake device that generates a braking force for stopping rotation of a hydraulic motor, an oil passage that supplies pressure oil from a hydraulic pump to the brake device to release the braking force, and drains pressure oil from the brake device. A hydraulic switching valve that selectively switches an oil passage that generates a braking force according to a pilot pressure, a pilot pressure oil passage that guides a pilot pressure that acts on the hydraulic switching valve, and the pilot pressure oil passage, A pilot pressure switching valve that selectively switches between a drain pressure for braking force and a driving pressure for releasing braking force, and a bypass that supplies a part of the pressure oil supplied from the hydraulic pump to the pilot pressure oil passage An oil passage, and when the pilot pressure switching valve makes the inside of the pilot pressure oil passage a drain pressure, the pressure oil supplied from the hydraulic pump is passed from the bypass oil passage to the pilot pressure oil passage. A braking system of the hydraulic motor, characterized in that the drain to.

  According to the brake system for a hydraulic motor of the present invention, when the pilot pressure switching valve sets the drain pressure in the pilot pressure oil passage, the pressure oil supplied from the hydraulic pump is passed through the bypass oil passage and the pilot pressure oil passage. Since the air is drained and the air in the pilot pressure oil passage is discharged by the drained pressure oil, the air in the pilot pressure oil passage can be surely removed. For this reason, the rising of the pilot pressure is not delayed, and the release timing of the braking force can be prevented from being delayed.

  Hereinafter, a brake system for a hydraulic motor according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an overall configuration of a hydraulic motor 1 to which a brake system is applied, and FIG. 2 is a cross-sectional view showing a brake release hydraulic switching valve 30 provided in the hydraulic motor 1.

  First, the overall configuration of the hydraulic motor 1 will be described with reference to FIG. The hydraulic motor 1 is, for example, a swash plate type hydraulic motor used in a turning device such as a construction machine.

  The hydraulic motor 1 includes an output shaft 2 connected to a load (not shown) and a cylinder block 3 connected to the output shaft 2 and rotating integrally with the output shaft 2. The output shaft 2 is rotatably supported by the case 11 and the cover 12 of the hydraulic motor 1 via bearings 17 and 18.

  A plurality of cylinders 4 are opened in parallel with the output shaft 2 on a concentric circle centering on the output shaft 2 in the cylinder block 3. A piston 6 that defines a volume chamber 5 is inserted into each cylinder 4 so as to be slidable back and forth.

  A shoe 9 is connected to the tip of the piston 6 via a spherical seat 10. The shoe 9 is in surface contact with the swash plate 7 fixed to the case 11. As the cylinder block 3 rotates, each shoe 9 comes into sliding contact with the swash plate 7, and each piston 6 reciprocates with a stroke amount corresponding to the tilt angle of the swash plate 7.

  A valve plate 8 with which the base end surface of the cylinder block 3 is in sliding contact is attached to the cover 12. The valve plate 8 has a port communicating with a hydraulic pump (not shown) and a port communicating with the tank side. Each piston 6 protrudes from the cylinder 4 by the hydraulic pressure guided from the hydraulic pump to each volume chamber 5 through each port, and each piston 6 pushes the swash plate 7 through the shoe 9 to rotate the cylinder block 3. Then, the rotation of the cylinder block 3 is transmitted to the load via the output shaft 2.

  The hydraulic motor 1 includes a friction braking type brake device 20. The brake device 20 will be described below.

  The brake device 20 is provided with a plurality of (three in the present embodiment) disk plates 21 that rotate together with the cylinder block 3 and the case 11 so as not to rotate. In this embodiment, a plurality of (two in this embodiment) friction plates 22 as friction members that generate a frictional braking force, and the disk plate 21 and the friction plate 22 are pressed against each other between the plates 21 and 22. And a brake actuating mechanism 25 that can release the friction brake force by releasing the pressing force.

  Each disk plate 21 has an annular shape, and teeth (not shown) are formed on the inner periphery. A spline 3 a formed so as to extend in the axial direction of the output shaft 2 is formed on the outer periphery of the cylinder block 3. When the teeth of the disk plate 21 and the splines 3 a of the cylinder block 3 are engaged with each other, the disk plate 21 rotates with the rotation of the cylinder block 3 and can move in the axial direction of the output shaft 2. Thus, each disk plate 21 is spline-engaged with the outer periphery of the cylinder block 3.

  Each friction plate 22 has an annular shape, and is attached to the inner periphery of the case 11 so as not to rotate relative to the case 11 and to be movable in the axial direction of the output shaft 2. Each friction plate 22 is also spline-engaged with the inner periphery of the case 11 like the disc plate 21.

  Each friction plate 22 is disposed so as to be sandwiched between adjacent disk plates 21.

  The brake operating mechanism 25 is supported between the inner periphery of the case 11 and is interposed between the cover 12 and the brake piston 27, and is disposed between the cover 12 and the brake piston 27. The brake piston 27 is attached to the disc plate. The brake piston 27 is moved against the urging force of the brake spring 26 by supplying pressure oil from a plurality of brake springs 26 as urging members urging toward 21 and a brake release hydraulic switching valve 30. And a brake release chamber 28 to be released.

  The brake piston 27 is formed between the sliding portion 27a that slides along the inner peripheral wall 11a of the case 11 and the friction plate 22 by pressing the disk plate 21 that is provided integrally with the sliding portion 27a and faces the sliding plate 27a. It comprises a piston portion 27b that generates a friction brake force. A pin 13 implanted in the cover 12 is inserted into the brake piston 27 and rotation around the output shaft 2 is prevented.

  The piston portion 27b is formed to have a smaller outer diameter compared to the sliding portion 27a, and a space exists between the outer peripheral surface 27c of the piston portion 27b and the inner peripheral wall 11a of the case 11.

  In the space, a ring body 29 is disposed so as to be in contact with both the outer peripheral surface 27c of the piston portion 27b and the inner peripheral wall 11a of the case 11. Thereby, the brake release chamber 28 is defined by the outer peripheral surface 27 c of the piston portion 27 b, the inner peripheral wall 11 a of the case 11, and the base end surface of the ring body 29. Note that a stepped portion 11 b with which the tip of the ring body 29 engages is formed on the inner peripheral wall 11 a of the case 11.

  The sliding portion 27a of the brake piston 27 is formed with a plurality of holes 27d opened on the base end face on the same circle, and the brake springs 26 are accommodated in the holes 27d, respectively.

  The brake release chamber 28 is selectively connected to a tank or a hydraulic supply source (pilot pump 50) (not shown) via a hydraulic switching valve 30. By switching the selection by the hydraulic switching valve 30, pressure oil is supplied to and discharged from the brake release chamber 28, and the brake piston 27 is moved forward and backward accordingly, and the brake operation and release thereof are performed.

  On the inner wall of the case 11, as a restricting member that restricts movement of each disk plate 21 and each friction plate 22 in the axial direction of the output shaft 2 more than a predetermined amount when the brake piston 27 moves forward by the urging force of the brake spring 26. The receiving portion 11c is formed. In this way, the disc plate 21 and the friction plate 22 are pressed against each other between the brake piston 27 and the receiving portion 11 c, and a friction brake force is generated between the disc plate 21 and the friction plate 22.

  2 is a cross-sectional view of the brake release hydraulic switching valve 30. The hydraulic switching valve 30 includes a valve body 31, a closing plug 34 for closing one open end 32 of the valve body 31, and a valve body 31. A spool 35 is slidably disposed in a hole formed in the central axis direction, and a pilot pressure as a signal pressure acts on one end thereof, and the spool 35 is biased against the pilot pressure (to the left in the figure). Return spring 36. When the driving pressure from the pilot pressure supply pilot pump 50 shown in FIG. 3 is supplied from the pilot pressure oil passage 82 to the opening end 33 as a pilot pressure port, the spool 35 is resisted against the urging force of the return spring 36. In the figure, movement in the right direction (hereinafter referred to as right movement. Similarly, movement in the left direction is referred to as left movement). The left movement of the spool 35 is restricted by the step 43 formed on the inner peripheral surface of the valve body 31, while the right movement is restricted by the right end of the spool 35 coming into contact with the closing plug 34.

  The valve body 31 includes a pump port 39 to which pressure oil from the pilot pump 50 is supplied through a pump oil passage 83 shown in FIG. 3, a brake port 38 communicating with the chamber 28, and a case 11 in which the cylinder block 3 is disposed. And a drain port 37 communicating with the. When the spool 35 is in the position of FIG. 2 (a), the pump port 39 and the brake port 38 are connected, pressure oil from the pilot pump 50 is supplied to the chamber 28, and the spool 35 is in the position of FIG. 2 (b). In some cases, the drain port 37 and the brake port 38 are connected, and the pressure oil in the chamber 28 is discharged into the case 11. The inside of the case 11 communicates with a tank side (not shown).

  The spool 35 formed of a cylindrical member has holes 40a and 40b that are formed along the central axis from both ends and do not communicate with each other, and concave grooves 41a and 41b formed on the outer peripheral surface of the spool 35, A communication hole 42a that communicates the hole 40a and the groove 41a and a communication hole 42b that communicates the hole 40b and the groove 41b are formed, and a part of the communication holes 42a and 42b is formed in an orifice shape. The A hole 40a, a concave groove 41a formed on the outer peripheral surface of the spool 35, and a communication hole 42a communicating the hole 40a and the groove 41a are easily formed in the spool 35 by cutting. Configure the bypass oil passage. On the other hand, the hole 40b, the concave groove 41b formed on the outer peripheral surface of the spool 35, and the communication hole 42b communicating the hole 40b and the groove 41b constitute a drain oil passage. The pair of grooves 41b are always in communication with each other by a restriction as an orifice.

  As shown in FIG. 3, in the pilot pressure oil passage 82 connected to the open end 33 as the pilot pressure port of the hydraulic switching valve 30, the driving pressure from the pilot pump 50 is applied to the spool 35, or the pilot pressure In order to drain the pressure oil in the oil passage 82 and cause the drain pressure to act on the spool 35, a pilot pressure switching valve 80 that selectively switches these is provided. The pilot pressure oil passage 82 and the pump oil passage 83 are supplied with pressure oil by the same hydraulic pump (pilot pump 50).

  As shown in FIG. 2A, the hydraulic switching valve 30 is configured as described above when the driving pressure from the pilot pump 50 acts on the spool 35 from the open end 33 through the pilot pressure oil passage 82. 35 moves to the right in the figure against the return spring 36, the pump port 39 communicates with the brake port 38 via the groove 41a, and pressure oil is supplied from the brake port 38 to the chamber 28 of FIG. 27b moves to the left, the pressing of the disc plate 21 and the friction plate 22 is released, and the brake device 20 does not generate a braking force.

  As shown in FIG. 2B, when the drain pressure is applied to the spool 35 from the opening end 33 by the pilot pressure oil passage 82, in other words, when the pressure oil is discharged from the opening end 33, the spool 35 is returned to the return spring. The pump port 39 and the brake port 38 are disconnected from each other by the urging force 36, while the brake port 38 and the drain port 37 communicate with each other through the hole 40b, the groove 41b, and the communication hole 42b. The pressure oil in the chamber 28 is discharged. For this reason, in FIG. 1, the piston portion 27 b moves rightward by the urging force of the brake spring 26 to press the disc plate 21 against the friction plate 22, and the brake device 20 generates a braking force. At this time, since the pressure oil to be drained is drained through the throttle of the groove portion 41b and the throttle of the communication hole 42b, the drain speed is slow and the braking force is generated slowly. The pilot pressure oil passage 82 communicates with the opening end 33. In this case, the pressure oil supplied from the pump port 39 is drained from the pilot pressure oil passage 82 through the orifice-shaped communication hole 42a. This prevents air from accumulating in the pilot pressure oil passage 82 during braking of the brake device 20.

  FIG. 3 shows a hydraulic circuit for turning a hydraulic excavator to which the brake system of the hydraulic motor of the present invention is applied. In the figure, a hydraulic motor 1 is configured to drive an upper swing body (not shown) of a hydraulic excavator through a speed reducer using a planetary gear mechanism. Further, the hydraulic motor 1 is provided with the above-described brake device 20, and the brake device 20 generates a braking force when the upper swing body stops turning.

  As described above, the pilot pump 50 that supplies the driving pressure to the pump port 39 and the spool 35 of the hydraulic switching valve 30 is provided, and the hydraulic pump 51 that supplies the hydraulic oil that has been sucked up from the tank 52 to the hydraulic motor 1 is provided. . The hydraulic pump 51 is connected to the hydraulic motor 1 through a pair of main pipes 54A and 54B. In the middle of the main pipelines 54A and 54B, a manually-switchable direction switching valve 55 is provided.

  The direction switching valve 55 is switched from the neutral position (A) to the switching position (B) and (C) by the operator operating the operation lever 58, and switched from the neutral position (A) to the switching position (B). In such a case, the discharged pressure oil is supplied from the main pipeline 54A to the hydraulic motor 1 and drained from the main pipeline 54B to the tank 52. On the other hand, when the neutral position (A) is switched to the switching position (C), the discharged pressure oil is supplied from the main line 54B to the hydraulic motor 1 and drained from the main line 54A to the tank 52. In the neutral position (A), the pressure oil from the hydraulic pump 51 is drained to the tank 52 without being supplied to the hydraulic motor 1. In this way, the configuration is such that the direction of the pressure oil supplied to and discharged from the hydraulic pump 51 to the hydraulic motor 1 is switched, and the rotational direction of the hydraulic motor 1 is switched or stopped.

  Branch pipes 57A, 57B, 58A and 58B are provided between the hydraulic motor 1 and the direction switching valve 55 to communicate between the main pipes 54A and 54B, and the tank pipe 56 is connected to the branch pipes 57A and 57B. , Connected to the connecting portion with the branch pipes 58A, 58B, and opens to the tank 52.

  Check valves 59A and 59B are provided in the middle of the branch pipes 57A and 57B, respectively, and the check valves 59A and 59B allow pressure oil to flow from the tank 52 toward the main pipes 54A and 54B. This prevents the main pipelines 54A and 54B from becoming a negative pressure state.

  A pair of relief valves 60A and 60B are provided in the middle of the branch pipes 58A and 58B. The relief valves 60A and 60B have a high relief setting pressure Ph determined in advance by pressure setting springs 61A and 61B. The valve opening pressure Pl at the time of low pressure relief is set by 62A and 62B. The relief valves 60A and 60B, for example, when the pressure (excess pressure) higher than the relief set pressure Ph is generated in the main pipeline 54A or 54B when the hydraulic motor 1 is rotated, etc., the valve bodies of the relief valves 60A and 60B are By opening the valve, this pressure (excess pressure) is relieved to the tank line 56 side.

  The accumulators 62A and 62B attached to the relief valves 60A and 60B are provided. For example, when the hydraulic motor 1 is rotated by inertia, the pressure oil from the main pipelines 54A and 54B passes through the throttles 67A and 67B. , The pressure oil is temporarily stored, and at this time, the relief valves 60A and 60B perform low pressure relief with the valve opening pressure Pl.

  As a result, the accumulators 62A and 62B provide a shockless function to the relief valves 60A and 60B, and the impact when the relief valves 60A and 60B are opened at the high relief set pressure Ph is reduced.

  Further, the brake device 20 described above for applying a braking force to the hydraulic motor 1 is provided. When the pressure oil in the chamber 28 is drained, the brake piston 27 presses the disc plate 21 against the friction plate 22 side by the brake spring 26, A braking force is generated on the output shaft 2 and the like of the hydraulic motor 1. When the hydraulic pressure is supplied from the pilot pump 50 to the chamber 28 from the brake line 73 when the hydraulic motor 1 is driven to rotate, the brake device 20 is supplied with the pressure at this time. The brake of the hydraulic motor 1 is released by compressing the brake spring 26.

  The brake release hydraulic pressure switching valve 30 described above selectively switches the connection destination of the brake line 73 between the pilot pump 50 and the tank 52. Here, when the drain pressure acts on the spool 35 via the opening end 33, the brake release hydraulic switching valve 30 drains the pressure oil in the chamber 28 by the urging force of the return spring 36, and the brake device 20 The braking position (d) where the braking force is generated is held. On the other hand, when the driving pressure is supplied from the open end 33 to the spool 35, the brake release hydraulic switching valve 30 is switched from the brake position (d) to the release position (e), and the pilot pump 50 to the chamber of the brake device 20 is switched. 28 is supplied with a drive pressure, that is, a brake release pressure, via a brake line 73.

  As described above, in order to switch the supply of the pilot pressure to the brake release hydraulic pressure switching valve 30, the pilot pressure switching valve 80 of the two-position switching valve is provided. The pilot pressure switching valve 80 is provided with an operation lever 81. The operation lever 81 is interlocked with the operation lever 58. When the operator switches the operation lever 58, the operation lever 81 is interlocked with the release lever (he The driving pressure from the pilot pump 50 acts on the pilot pressure port at the end of the spool 35 through the pilot pressure oil passage 82 branched from the pump oil passage 83. On the other hand, when switching to the braking position (g), the pilot pressure port (opening end 33) is opened to the tank 52, and the pressure oil in the pilot pressure oil passage 82 is drained to the tank 52. A drain pressure acts on the end.

  Next, the operation of the brake release hydraulic pressure switching valve 30 will be described according to the state of the brake device 20. In the following description, it is assumed that the vehicle is stopped and the engine as the driving source of the pilot pump 50 is always in operation.

  First, a case where the brake device 20 generates a braking force will be described with reference to FIG.

  In this case, the pilot pressure switching valve 80 is switched to the braking position (g). Therefore, a drain pressure is applied to the end of the spool 35 of the hydraulic switching valve 30, and the hydraulic switching valve 30 is switched to the braking position (d) by the urging force of the return spring 36. The pressure oil supplied from the pilot pump 50 through the pump oil passage 83 flows from the pump port 39 of the hydraulic switching valve 30 to the opening end 33 with a flow rate restricted through the groove 41a, the orifice-shaped communication hole 42a, and the hole 40a. The oil is discharged to the tank 52 through the pilot pressure oil passage 82 and the pilot pressure switching valve 80. On the other hand, the pressure oil in the chamber 28 is drained to the tank 52 via the brake port 38 and the drain port 37, and the urging force of the brake spring 26 becomes larger than the pressure in the chamber 28. For this reason, the brake piston 27 moves to the right, and by this right movement, the disc plate 21 is pressed against the friction plate 22 and a friction brake force is generated between the disc plate 21 and the friction plate 22. Since a part of the pressure oil is supplied to the pilot pressure oil passage 82 from the pump port 39 through the orifice-shaped communication hole 42a and the like to the open end 33, the pilot pressure oil passage 82 is always in the pilot pressure oil passage 82. The pressure oil continues to be supplied, and air is released from the pilot pressure oil passage, and the pilot pressure oil passage 82 is filled with the pressure oil so that air does not enter.

  Next, a case where the brake device 20 does not generate a braking force will be described.

  In this case, the pilot pressure switching valve 80 is switched to the release position (f). The driving pressure supplied from the pilot pump 50 is supplied to the pump port 39 through the pump oil passage 83 and is sent from the pilot pressure switching valve 80 to the opening end 33 through the pilot pressure oil passage 82 to be supplied to the spool 35 as a pilot pressure. Works. When the driving pressure is applied to the spool 35, the hydraulic switching valve 30 is switched to the release position (e) against the urging force of the return spring 36, and the pressure oil introduced into the pump port 39 is supplied from the brake port 38 to the brake device. 20 chambers 28 are supplied. By supplying pressurized oil to the chamber 28, the pressure in the chamber 28 overcomes the urging force of the brake spring 26, the pressure contact between the disk plate 21 and the friction plate 22 is released, and the space between the disk plate 21 and the friction plate 22 is released. To eliminate the friction brake force. The pressure in the pump oil passage 83, the pilot pressure oil passage 82, the hole 40a, the groove 41a, and the communication hole 42a is the same, and no pressure oil flows between them.

  Next, a case where the brake device 20 switches from a braking state that generates a braking force to a non-braking (braking release) state that does not occur will be described.

  First, in the braking state, as described above, the pilot pressure switching valve 80 is in the braking position (g), and the hydraulic pressure switching valve 30 is in the braking position (d). Therefore, the pressure oil from the pilot pump 50 is drained from the pump oil path 83 via the hydraulic pressure switching valve 30 and the pilot pressure oil path 82. In a state where the braking state is maintained, the pressure oil always fills the pilot pressure oil passage 82 and air does not enter. When this state is switched to the non-braking state, that is, when the pilot pressure switching valve 80 is switched to the release position (g), the pressure oil from the pilot pump 50 is supplied to the pilot pressure oil passage 82, and the hydraulic pressure switching valve 30 is released to the release position. Switch to position (e).

  Here, when switching from the braking state to the non-braking state, the pilot pressure oil passage 82 is filled with pressure oil, and as the pilot pressure switching valve 80 is switched to the release position (f), the pilot pump 50 The pilot pressure is rapidly increased by the pressure oil supplied from. For this reason, the spool 35 of the hydraulic switching valve 30 is quickly switched by the pilot pressure (driving pressure), the pump port 39 and the brake port 38 communicate with each other, and the pressure oil from the pilot pump 50 is supplied to the chamber 28, and the brake device The pressure in the 20 chambers 28 increases, and the braking force can be quickly eliminated. As a result, the brake force release timing is delayed, and the rotation of the hydraulic motor 1 accelerates wear of the brake device 20 and can solve the problem of shortening the service life.

  Furthermore, the case where the brake device 20 switches from the non-braking state to the braking state will be described.

  First, the position of the pilot pressure switching valve 80 is switched from the release position (f) to the braking position (g). As a result, the end of the spool 35 is switched to the drain pressure. However, the pressure oil from the pilot pump 50 is sent from the pump oil passage 83 to the pump port 39 and is also supplied from the communication hole 42a to the open end 33. However, since the pressure is sufficiently reduced by the orifice of the communication hole 42a, the drain pressure Will not increase. Therefore, the spool 35 is quickly switched to the braking position (d) by the return spring 36. When switched to the braking position (d), the pressure oil in the chamber 28 passes through the drain port 37 from the brake port 38 and is drained to the tank 52. As a result, the pressure in the chamber 28 decreases, and the braking device 20 generates a braking force by the urging force of the brake spring 26. A part of the pressure oil is supplied to the pilot pressure oil passage 82 from the opening end 33 through the orifice-shaped communication hole 42a from the pump port 39, and the pilot pressure oil passage is filled with the pressure oil.

Therefore, in the brake system of the hydraulic motor of the present invention, in the braking state in which the pressure oil in the pilot pressure oil passage 82 is drained, the pressure oil from the pilot pump 50 is bypassed from the pump port 39, that is, the pilot pressure oil passage. 82 is drained from pilot pressure oil passage 82 through hole 40a, groove 41a, and communication hole 42a. Since the pressure oil in the pump port 39 is drained through the pilot pressure oil passage 82, the residual air in the pilot pressure oil passage 82 is discharged using the pressure oil, and the air in the pilot pressure oil passage 82 is surely vented. can do. For this reason, a delay in the rise of the pilot pressure (driving pressure supplied from the pilot pump 50) that occurs when air bleeding is insufficient when releasing the braking is suppressed. As a result, the braking force release timing is not delayed, wear of the brake device 20 is suppressed, and the life of the brake device 20 can be extended. FIG. 4 is applied to the hydraulic motor brake device of the second embodiment. 1 shows a hydraulic circuit for turning a hydraulic excavator. This embodiment is an embodiment in which only the configuration of the brake release hydraulic switching valve 30 is changed as compared with the hydraulic circuit of the first embodiment shown in FIG.

  Specifically, in the first embodiment, the pump port 39 and the open end 33 serving as a pilot pressure port communicate with each other through a hole 40a formed in the spool 35, a groove 41a, and a communication hole 42a. The pressure oil in the oil passage 83 is discharged to the pilot pressure oil passage 82 via the inside of the spool 35. On the other hand, in this embodiment, the hydraulic switching valve 90 is constituted by a three-port two-position switching valve, eliminates the hole 40a and the communication hole 42a formed in the spool 35, and connects the pump oil passage 83 and the opening end 33 to each other. The oil passage 91 that directly communicates is formed not in the spool 35 but in the valve body 31. The oil passage 91 is not limited to the one formed in the valve body 31 and may be an external pipe. The oil passage 91 is provided with an orifice 92 to restrict the flow rate of the pressure oil from the pump oil passage 83 to the pilot pressure oil passage 82.

  In this embodiment, in addition to the effects of the first embodiment, the shape of the spool 35 can be simplified, and it is not necessary to perform fine processing on the spool 35.

  FIG. 5 shows a hydraulic circuit for turning a hydraulic excavator applied to the hydraulic motor brake device of the third embodiment. In this embodiment, the configuration of the brake release hydraulic switching valve 30 is changed as compared with the hydraulic circuit of the first embodiment shown in FIG. 3, and the pump port 39 and the pilot only when the brake device 20 generates a braking force. This is an embodiment in which the open end 33 as a pressure port is in communication.

  A specific configuration will be described with reference to FIG. The configuration corresponding to the hole 40a is different from the configuration shown in FIG. The hole 40a is connected to the communication hole 42a and opened to the opening end 33. However, in the configuration of this embodiment, the hole 40a does not open to the opening end 33 but opens to the inner peripheral surface of the valve body 31. A hole portion 44 is formed. Further, the valve body 31 is formed with a communication portion 45 that communicates with the hole portion 44 and communicates with the opening end 33 in a state where the drain pressure is applied to the spool 35. When the drain pressure acts on the spool 35, the communication portion 45 communicates the hole 44 and the opening end 33. However, when the driving pressure acts on the spool 35, the communication portion 45 does not connect the hole 44 and the opening end 33. It is formed at a position to be in a communication state.

  Therefore, when the driving pressure is applied to the end surface of the spool 35, the pump port 39 and the brake port 38 communicate with each other via the hole 44, the groove 41a, and the communication hole 42a, and the brake device 20 is in a brake released state. . On the other hand, when the drain pressure is applied, the pump port 39 communicates with the opening end 33 through the hole 44, the groove 41a, and the communication hole 42a. The brake port 38 communicates with the drain port 37, and the brake device 20 generates a braking force.

  In this embodiment, pressure oil does not flow from the pump oil passage 83 to the pilot pressure oil passage 82 at the time of non-braking, so that the switching from the braking state to the non-braking state is performed quickly, and the release timing of the braking force is prevented from being delayed. Is done.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  The present invention can be applied to a friction braking type brake system used in a hydraulic motor.

It is sectional drawing which shows the whole structure of the hydraulic motor to which the brake system in embodiment of this invention is applied. It is sectional drawing which shows the hydraulic pressure switching valve for brake release in embodiment of this invention. It is a hydraulic circuit diagram for turning of a hydraulic excavator to which a brake system of a hydraulic motor is applied. FIG. 5 is a turning hydraulic circuit diagram of a hydraulic excavator to which a hydraulic motor brake system according to a second embodiment is applied. It is a hydraulic circuit diagram for turning of a hydraulic excavator to which a brake system of a hydraulic motor of a third embodiment is applied. It is sectional drawing which shows the hydraulic pressure switching valve for brake release in 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydraulic motor 2 Output shaft 20 Brake device 26 Brake spring 27 Brake piston 28 Brake release chamber 29 Ring body 30 Brake release hydraulic switching valve 31 Valve body 33 Open end 34 Closure plug 35 Spool 36 Return spring 37 Drain port 38 Brake port 39 Pump Port 40a Hole 41a Groove 42a Communication Hole 43 Step 50 Pilot Pump 52 Tank 68 Operation Lever 80 Pilot Pressure Switching Valve 81 Operation Lever 82 Pilot Pressure Oil Path 83 Pump Oil Path 90 Hydraulic Switching Valve 91 Oil Path

Claims (6)

A brake device that generates a braking force to stop the rotation of the hydraulic motor;
An oil passage that releases the braking force by supplying pressure oil from the hydraulic pump to the brake device and an oil passage that drains the pressure oil from the brake device and generates the braking force are selectively switched according to the pilot pressure. A hydraulic switching valve;
A pilot pressure oil passage for guiding pilot pressure acting on the hydraulic switching valve;
A pilot pressure switching valve that selectively switches the inside of the pilot pressure oil passage between a drain pressure for braking force and a driving pressure for releasing braking force;
A bypass oil passage for supplying a part of the pressure oil supplied from the hydraulic pump to the pilot pressure oil passage,
When the pilot pressure switching valve sets the drain pressure in the pilot pressure oil passage, the hydraulic oil supplied from the hydraulic pump is drained from the bypass oil passage through the pilot pressure oil passage. Motor brake system.   The brake system for a hydraulic motor according to claim 1, wherein the bypass oil passage includes an orifice. The hydraulic switching valve includes a brake port that supplies pressure oil to the brake device, a pump port that communicates with the brake port and is supplied with pressure oil from a hydraulic pump, a drain port that drains pressure oil, A pilot port connected to the pilot pressure oil passage, a spool that moves according to the pilot pressure from the pilot port, and selectively connects the brake port to the pump port or the drain port, and a pilot pressure to the spool. With a return spring that urges to resist,
2. The brake system for a hydraulic motor according to claim 1, wherein the bypass oil passage is an oil passage that passes through the spool and communicates the pump port and the pilot port. 3. The spool is composed of a cylindrical member,
The oil passage penetrating through the spool is formed along the central axis of the spool, and has a hole opening in the pilot pressure oil passage, and a concave shape formed in the outer peripheral surface of the spool and opening in the pump port. The brake system for a hydraulic motor according to claim 3, further comprising: a groove portion, and a communication hole communicating with the hole portion and the groove portion.   The brake system for a hydraulic motor according to claim 3, wherein the communication hole includes the orifice. The hydraulic switching valve includes a valve body that slidably houses the spool,
The hydraulic motor brake system according to claim 1 or 2, wherein the bypass oil passage is an oil passage that penetrates through the valve body.

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