JP2006046150A - Pressure pulsation reducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure pulsation reducer capable of reducing pressure pulsation of pressure oil discharged from one discharge pressure port of a hydraulic pump and of reducing noise accompanied by the pressure pulsation. <P>SOLUTION: Pressure oil discharged from the pump discharge pressure port (21) is introduced to a first pressure chamber (7) via an oil passage (3) and to a second pressure chamber (8) via a second oil passage from an oil passage (33) to a pipe line (35). Pulsation of the pressure oil introduced to the second pressure chamber (8) can be set in a state of the opposite phase to that of pulsation of the pressure oil introduced to the first pressure chamber (7), by the length of the second oil passage. A free piston (6) defining the first pressure chamber (7) and the second pressure chamber (8) is resonated and operated by the pulsation of the pressure oil introduced to each of the pressure chambers (7), (8), and promptly absorbs and alleviates the pulsation of pressure oil inside the oil passage (33) communicated with the first pressure chamber (7) by increasing/reducing the volume of the first pressure chamber (7). As a result, the pressure pulsation can be smoothed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pressure pulsation reducing device that reduces pulsation of pump discharge pressure.

  Conventionally, as a pressure pulsation reducing device for reducing pulsation of pump discharge pressure, many devices having a structure in which a side branch is branched and connected to a pipe from a pump discharge pressure port are used. As a device using a side branch, a pulsation reducing device (see Patent Document 1) has been proposed.

  Further, as a pressure pulsation reducing device that does not use a side branch, a fluid propagation noise reducing device that combines a flow sensor or a pressure sensor and a drive source such as an electromagnetic switching valve having high response characteristics (see Patent Document 2). ) And a pulsation reduction mechanism (see Patent Document 3) for a pump having two discharge pressure characteristics.

  The fluid propagation noise reduction device described in Patent Document 2 has a configuration shown in FIG. The flow path resistance 59 disposed in the pipe 51 from the hydraulic pump 50 causes a pressure drop corresponding to the flow rate of the fluid passing through the flow path resistance 59. The pressure sensor 57 disposed on the upstream side of the flow path resistance 59 detects the fluid pressure in the pipe 51 in the vicinity of the hydraulic pump 50 and outputs the detected pressure signal P to the microprocessor 52.

  The second pressure sensor 58 is disposed on the downstream side of the flow path resistance 59, detects the pressure in the pipe 51, and outputs the detected pressure signal L to the microprocessor 52. The microprocessor 52 compares the two pressure signals P detected on the upstream side and the downstream side of the flow path resistance 59 with the pressure signal L to calculate the pressure drop in the flow path resistance 59 and responds to the pressure drop. The correction signal C is output to the drive source 53 via the wiring 60.

  The drive source 53 drives the flow generator 54 in accordance with the input correction signal C to generate a correction flow in the pipe 51. When the correction signal C input to the drive source 53 is smaller than a predetermined value, the drive source 53 contracts the piston 56 according to the correction signal C, and the volume of the fluid chamber 55 is increased by the movement of the piston 56. Thereby, the fluid is partially sucked into the fluid chamber 55 from the pipe 51, and the pressure in the pipe 51 can be reduced.

  When the correction signal C input to the drive source 53 is larger than a predetermined value, the drive source 53 extends the piston 56 according to the correction signal C, and reduces the volume of the fluid chamber 55 by the movement of the piston 56. . Thereby, a fluid is added in the piping 51, and the pressure in the piping 51 can be increased.

  By increasing or decreasing the volume of the fluid chamber 55 in this way, a correction flow that cancels pulsations occurring in the discharge flow of the hydraulic pump 50 can be supplied from the fluid chamber 55 into the pipe 51. Thereby, the pulsation of the flow in the hydraulic system can be eliminated, and the noise generated from various devices in the hydraulic system can be reduced.

  The pulsation reducing mechanism described in Patent Document 3 has a configuration shown in FIG. 10, which is an enlarged cross-sectional view of the port block of the piston pump. Pressure oil compressed by reciprocating movement of each piston (not shown) in the piston pump is transferred from the inner and outer discharge holes 65a and 65b formed in the valve plate to the ports 64a and 64b through the passages 66a and 66b. Discharged.

  A cylinder 69 is formed in a part of the port block 63, and a free piston 70 is slidably inserted into the cylinder 69, and a first pressure absorption chamber 68a and a second pressure absorption chamber 68b are provided on both sides thereof. Is defined. One end side of the cylinder 69 is sealed with a plug 72 via a sealing material 71.

  The first pressure absorption chamber 68a of the cylinder 69 communicates with pressure transmission passages 67a and 67b branched from the passage 66a, and the second pressure absorption chamber 68b communicates with a pressure transmission passage 67b branched from the passage 66b. . Thereby, the discharge pressure from the discharge pressure port 64a and the discharge pressure port 64b acts on each end face of the free piston 70, respectively. The oil leakage generated from the gap between the free piston 70 and the cylinder 69 flows out to the low pressure side through the drain hole 73.

  The pulsation reducing mechanism described in Patent Document 3 can exhibit the following effects. That is, a piston (not shown) arranged on the inner peripheral side of the cylinder block in the piston pump and a piston (not shown) arranged on the outer peripheral side reciprocate with different phases, and accordingly, different discharge pressures P1. , P2 can discharge hydraulic oil.

  The different discharge pressures P1 and P2 are led to the first pressure absorption chamber 68a and the second pressure absorption chamber 68b of the cylinder 69, respectively, and the free piston 70 according to the pressure difference between the discharge pressure P1 and the discharge pressure P2. Will be moved. When the discharge pressure P1 is higher than the discharge pressure P2, the free piston 70 strokes upward in the drawing to increase the volume of the first absorption chamber 68a. On the other hand, when the discharge pressure P2 becomes higher than the discharge pressure P1, the free piston 70 strokes downward in the drawing to increase the volume of the second pressure absorption chamber 68b.

That is, the free piston 70 strokes upon receiving the higher pressure of the discharge pressure P1 or the discharge pressure P2 having different phases, and expands the volume of the first pressure absorption chamber 68a or the second pressure absorption chamber 68b. . Thereby, the peak of the discharge pressure on the high pressure side is absorbed and relaxed by the volume expansion of the first pressure absorption chamber 68a or the second pressure absorption chamber 68b, and the pressure pulsation can be smoothed.
Japanese Patent No. 3413738 JP-A-8-177723 JP-A-9-14127

  As a device using a side branch as shown in Patent Document 1, in a pulsation reducing device, a side branch having a relatively long length must be used as a side branch for suppressing pulsation, which is extra to accommodate the side branch. Needed a lot of space. In addition, there has been a problem that a clamping place for clamping the side branch has to be secured. Further, in order to connect the side branch to the piping, a connecting portion manifold must be used, resulting in an increase in cost and an increase in piping work for installing the connecting portion manifold.

  In the apparatus for reducing fluid propagation noise described in Patent Document 2, it is necessary to use a drive source 53 such as a pressure sensor 57, a second pressure sensor 58, or an electromagnetic switching valve having high response characteristics. In addition, it is necessary to ensure high sealing performance at the connection portion between the pressure sensor 57, the second pressure sensor 58, the drive source 53, the flow path resistance 59, and the like and the pipe 22.

  In addition, there are a large number of sealing parts that must ensure high sealing performance, and it takes a lot of labor and time to ensure sealing performance. Furthermore, as the pressure of the pressure oil flowing in the pipe line 51 becomes high, there is a problem that it is necessary to ensure durability at the high pressure portion.

  If these problems are not solved in total, the reliability as a device for reducing fluid propagation noise will be deteriorated, and in order to ensure the reliability, it is necessary to assemble a device for reducing fluid propagation noise. Also took great care and a lot of time.

  Furthermore, when the detection sensitivity of the pressure sensor 57 and the second pressure sensor 58 is too high, or the response characteristic of the drive source 53 is too high, the pressure sensor 57 and the second pressure sensor 58 have a minute pressure fluctuation. There is a risk that a signal will oscillate like a housing in a closed loop circuit formed by the microprocessor 52, the drive source 53, and the piping 22 from the pressure sensor 57 and the second pressure sensor 58. Was expensive. Conversely, if the detection sensitivities of the pressure sensor 57 and the second pressure sensor 58 are too low, there is a problem that pulsation cannot be reduced.

  For this reason, the pressure sensor 57, the second pressure sensor 58, the microprocessor 52, the driving source 53, the flow are reduced so as to reduce the pulsation in the pipe 22 while preventing the oscillation of the signal in the closed loop circuit. It is necessary to adjust each of the road resistances 65 in a well-balanced manner, and it is extremely difficult to adjust the resistances so as to be in an optimum state.

  In the pulsation reduction mechanism described in Patent Document 3, a so-called double pump or tandem pump that has two discharge pressure ports 64a and 64b and discharges pressure oil having discharge pressure characteristics with different phases from each discharge pressure port. Can only be used against. Moreover, even when a double pump or a tandem pump is used, when the pressure oil discharged from the two discharge pressure ports is merged and then supplied to the actuator or the like, the pressure oil from the two discharge pressure ports is supplied. Even when each actuator is supplied to a separate actuator or the like, the pulsation reducing mechanism can only function when the pressure of the pressure oil discharged from the two discharge pressure ports is set to substantially equal pressure. Yes.

  For example, when the pressure of the pressure oil discharged from one discharge pressure port is too higher than the pressure of the pressure oil discharged from the other discharge pressure port, the free piston 56 is moved to one side by the pressure oil on the high pressure side. The pressure pulsation of the pressure oil discharged from the discharge pressure port cannot be reduced. In addition, when one discharge pressure port is unloaded, the pulsation reducing mechanism does not operate, and pressure oil is discharged from the other discharge pressure port while maintaining the same pressure pulsation as the conventional pressure pulsation. It was discharged, and noise due to pressure pulsation could not be reduced.

  In the present invention, a pressure pulsation reducing device that solves the conventional problems and can reduce the pressure pulsation of the pressure oil discharged from one discharge pressure port in the hydraulic pump to reduce noise accompanying the pressure pulsation. Is to provide.

The object of the present invention can be achieved by the inventions described in claims 1 to 7.
That is, in the present invention, as described in claim 1, a cylinder defined by a free piston in a first pressure chamber and a second pressure chamber is provided, and the first pressure chamber is one discharge of the hydraulic pump. The pressure port is connected in the vicinity of the discharge pressure port via the first oil passage, and the second pressure chamber has a length that reverses the pulsation of pressure oil from the one discharge pressure port and the discharge pressure port. The main feature is that it is connected via the second oil passage.

Further, in the present invention, by making the length of the second oil passage adjustable, it is possible to obtain pressure oil having a pulsation reversed with respect to the pulsation of the pressure oil from the discharge pressure port, or the second pressure chamber. The main feature is that the pressure loss of the pressure oil led to the above is compensated.
Furthermore, in the present invention, the main feature is that collision noise and the like generated between the free piston and the cylinder storing the free piston are prevented.

  In the present invention, the pulsation of the pressure oil discharged from the discharge port is reduced by connecting the cylinder defined by the free piston to the first pressure chamber and the second pressure chamber to the discharge port of the hydraulic pump. It is characterized by that. Further, as a configuration for reducing the pulsation of the pressure oil discharged from the discharge port, the first pressure chamber of the cylinder is connected to the discharge port in the vicinity of the discharge port, and the second pressure chamber is connected to the discharge pressure port. The pressure oil is connected through a second oil passage having a length that reverses the pulsation of the pressure oil.

  Thereby, the pressure oil discharged from the discharge port can be directly introduced into the first pressure chamber of the cylinder in a state having pulsation, and the pulsation of the pressure oil from the discharge pressure port can be introduced into the second pressure chamber. It can be introduced in an inverted state. That is, the pressure oil introduced into the first pressure chamber and the pressure oil introduced into the second pressure chamber are in a state in which the phases of the pulsations of the pressure oil are mutually reversed.

  The pressure oil in a state where the phases are reversed with each other simultaneously acts on both end portions of the free piston, whereby the volume of the first pressure chamber can be increased or decreased. The pressure oil pulsation in the oil passage communicating with the first pressure chamber is absorbed and relaxed by increasing / decreasing the volume of the first pressure chamber, and the pressure pulsation is smoothed, whereby the pressure oil pulsation in the oil passage is smoothed. Can be reduced.

  For this reason, the pressure oil from the discharge port of the hydraulic pump can be supplied to the actuator or the like in a state where the pulsation is smoothed or in a state where the pulsation is greatly reduced even if there is pulsation. Thereby, the various noises which have occurred with the pulsation of the pressure oil can be reduced.

  The cylinder may be disposed separately from the hydraulic pump and attached to the casing of the hydraulic pump, or may be disposed separately via a pipe line or the like. It can also be formed integrally in the casing of the hydraulic pump.

  A hydraulic hose is provided in at least a part of the second oil passage as described in claim 2, and the length of the hydraulic hose provided in the second oil passage is adjusted to thereby adjust the pressure oil introduced into the second pressure chamber. The pulsation state can be reversed with respect to the pulsation state of the pressure oil introduced into the first pressure chamber. Further, the length of the hydraulic hose can be adjusted depending on which of the natural frequency components of the pulsation described above is reduced to which natural frequency component.

  When the hydraulic pump is driven at the rated rotation, the natural frequency of the order to be reduced is calculated beforehand by calculation or the like along with the primary natural frequency of the pulsation corresponding to the rated rotation and the pulsation of the primary natural frequency component. The length of the hydraulic hose can be adjusted so that the length of the second oil passage becomes a length necessary to reduce the natural frequency component obtained.

  In addition, a plurality of hydraulic hoses are obtained so that the natural frequencies of pulsations corresponding to a plurality of rated rotations are obtained in advance by calculation or the like, and the length of the second oil passage is a length corresponding to each rated rotation. You can also set the length. That is, the length of the hydraulic hose can be set according to various condition settings. A plurality of hydraulic hoses having a set length can be prepared in advance, and hydraulic hoses having a length suitable for various conditions can be used.

  As described in claim 3, it is desirable to form a cancel mechanism for the free piston to compensate for the pressure loss of the pressure oil introduced into the second pressure chamber. The frequency component that resonates with the free piston is the natural frequency component of the pulsation, but the driving force for resonating the free piston is the pressure oil introduced into the first pressure chamber and the second pressure chamber. Pressure is acting. That is, in each pressure chamber, a pressure in a form obtained by multiplying the pressure of the introduced pressure oil by the pulsation waveform is acting.

  However, the pressure oil introduced into the first pressure chamber through the first oil passage in the vicinity of the discharge port is reversed with the discharge pressure of the hydraulic pump almost unchanged, whereas the pulsation of the pressure oil is reversed. The pressure oil introduced into the second pressure chamber through the length of the second oil passage to be introduced is introduced in a state where the pressure is reduced by a pressure loss corresponding to the length of the second oil passage. .

  For this reason, the cancellation mechanism which compensates the pressure loss part by a 2nd oil path so that the pressure of the pressure oil introduce | transduced into a 1st pressure chamber and the pressure oil introduced into a 2nd pressure chamber may become the same pressure. It is desirable to form for the free piston.

  As the cancel mechanism, a spring for urging the free piston toward the first pressure chamber may be provided in the cylinder as described in claim 4. The biasing force of the spring disposed in the cylinder can compensate for the pressure loss due to the second oil passage by adopting a configuration capable of applying a biasing force commensurate with the pressure loss due to the second oil passage. it can.

  Further, as the cancel mechanism, the pressure receiving area of the free piston is configured to be different between the first pressure chamber side and the second pressure chamber side as described in claim 5, and the first pressure chamber side of the free piston is configured. It is also possible to form an area step in which the pressure receiving area at is smaller than the pressure receiving area at the second pressure chamber side, and to compensate for the pressure loss due to the second oil passage by the same area step.

  The cancel mechanism using the spring described in claim 4 and the cancel mechanism using the area step described in claim 5 may be configured independently or may be configured so that the two cancel mechanisms coexist. it can. When the two cancellation mechanisms are configured at the same time, it is necessary to set the resultant force of the two cancellation mechanisms to be a force that compensates for the pressure loss of the second oil passage.

  As in the configuration described in claim 6, the third pressure chamber is connected to the second pressure chamber, and the third pressure chamber is introduced with hydraulic pressure in substantially the same state as introduced into the first pressure chamber, It can also be set as the structure which has arrange | positioned the 2nd free piston which defines a 2nd pressure chamber and a 3rd pressure chamber. Thereby, the pressure loss due to the second oil passage can be compensated by the second free piston.

  The related configuration of the second free piston and the free piston may be configured such that one end portion of the second free piston is in contact with the end portion of the free piston on the second pressure chamber side. An integrally formed configuration can also be used. Moreover, it can also be set as the structure which put the spring between the end surfaces which a free piston and a 2nd free piston oppose.

  According to the seventh aspect of the present invention, a damper mechanism that prevents a collision between the free piston and the cylinder can be formed. As the damper mechanism, various configurations can be adopted as long as the end surface of the free piston or the vicinity of the end surface portion does not collide with the inner end surface portion of the cylinder.

  For example, when the end face of the free piston or the vicinity of the end face approaches a distance that is likely to collide with the end face of the cylinder, the pressure oil interposed between the end face of the free piston or the vicinity of the end face and the inner end face of the cylinder The end face of the free piston or the vicinity of the end face portion does not collide with the inner end face portion of the cylinder.

  In addition, it is desirable to form a damper mechanism for preventing the free piston from rebounding in the direction away from the inner end surface portion of the cylinder by the pressure oil whose pressure has increased. As a damper mechanism for preventing rebound, for example, a pressure chamber that increases in pressure due to the proximity of a free piston is disposed, and the pressure chamber and the first pressure chamber or the second pressure chamber are communicated with each other via a throttle valve or the like. Can be configured. The throttle valve or the like can be formed on the cylinder body or on the periphery of the end portion of the free piston.

  Preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings. As the configuration of the pressure pulsation reducing device of the present invention, in addition to the shape and arrangement described below, the shape and arrangement are adopted as long as they can solve the problems of the present invention. It is something that can be done. For this reason, this invention is not limited to the Example demonstrated below, A various change is possible.

  FIG. 1 is a hydraulic circuit diagram according to an embodiment of the present invention. Pressure oil discharged from the variable capacity hydraulic pump 2 is supplied from the discharge pressure port 21 through the oil passage 33 to the pump discharge port 36 formed in the pump block of the hydraulic pump 2 and connected to the pump discharge port 36. It can be supplied to the operation valve 23 via the pipe 34.

  Although a variable displacement type hydraulic pump is shown as the hydraulic pump 2, in the present invention, the hydraulic pump is not limited to the variable displacement type, and a fixed displacement type hydraulic pump can also be used. Is.

  In addition, the discharge pressure port 21 of the hydraulic pump 2 and the pump discharge port 36 formed in the pump block are shown separately, and in the following description, they are also described separately. In order to make it easy to understand the explanation about the pressure oil to be introduced, both the discharge pressure port 21 and the pump discharge port 36 are treated as the same port without distinction, and the present invention is applied to the same port. A pressure pulsation device can be provided.

  The oil passage 3 branched from the oil passage 33 is connected to the input port 11 of the cylinder 5, and the pressure oil discharged from the hydraulic pump 2 is supplied to the first pressure chamber 7 of the cylinder 5. An oil passage from the discharge pressure port 21 to the input port 11 forms a first oil passage. FIG. 1 shows an example in which the oil passage formed in the pump block is the first oil passage.

  The present invention is not limited to the configuration in which the cylinder 5 is built in the pump block. The cylinder 5 is formed separately from the pump block, and is connected to the pump discharge port 36 of the pump block via a pipe line or the like. Thus, the input port 11 may be connected.

  For example, FIG. 8 shows a cross-sectional view of a cylinder block 32 that can be separately attached to a hydraulic pump, although it is shown using the structure of the free piston of Example 3 described below. Yes. As shown in FIG. 8, the cylinder block 32 including the cylinder 5 is configured independently and can be attached to the hydraulic pump, whereby the cylinder 5 and the hydraulic pump 2 are configured separately. Can do. By doing in this way, it can attach separately also with respect to the pump already installed in the machine.

  In FIG. 8, the oil passage 35 in the cylinder block 32 and the oil passage 35 in the pump block 31 are connected, and the drain oil passage 15 in the cylinder block 32 and the drain oil passage 15 in the pump block 31 are connected.

  Although not shown in FIG. 8, the oil passage 3 is connected to the first pressure chamber 7, and the oil passage 3 is connected to the oil passage 3 in the cylinder block 32 and the oil passage 3 in the pump block 31. Has been. The ends of the first pressure chamber 7 and the second pressure chamber 8 are sealed by a sealing member 37.

  As shown in FIG. 1, a pipe 35 branched from a pipe 34 connected to the pump discharge port 36 is connected to the input port 12 of the cylinder 5. Pressure oil from the pump discharge port 36 can be introduced into the second pressure chamber 8 of the cylinder 5 through the input port 12. The oil passages from the discharge pressure port 21 to the oil passage 33, the conduit 34, and the conduit 35 form a second oil passage.

  The length of the second oil passage can be adjusted by adjusting the length of at least one of the hydraulic hoses 39 in the conduit 34 or the hydraulic hose 39 'in the pilot conduit 35. As a result, the pressure oil pulsating in the opposite phase to the pulsation of the pressure oil introduced into the first pressure chamber 7 can be transferred to the second pressure chamber 8 simply by adjusting the lengths of the hydraulic hoses 39, 39 ′. Can be introduced.

  The waveform of the pulsation of the oil passage can be actually obtained experimentally as a curve shape in which a plurality of curves overlap the Sin curve, but here, it can be expressed using the Sin curve for convenience. . The Sin curve A is input to the first pressure chamber 7, and the Sin curve B inverted with respect to the Sin curve A is input to the second pressure chamber 8. The free piston 6 that defines the first pressure chamber 7 and the second pressure chamber 8 resonates in the left-right direction in FIG. 1 by the pressure oil whose pulsation is in the opposite phase.

  At this time, the pulsation waveform of the pressure oil introduced into the first pressure chamber 7 and the pulsation waveform of the pressure oil introduced into the second pressure chamber 8 are pulsation waveforms that are inverted with a phase difference of at least 180 degrees. Yes. If the pressure at the top of the Sin curve A is acting on the pressure receiving surface of the free piston 6 on the first pressure chamber 7 side, the Sin curve B is applied on the pressure receiving surface of the free piston 6 on the second pressure chamber 8 side. The force at the bottom of the is acting.

  For this reason, the first pressure chamber 7 is at a high pressure, the second pressure chamber 8 is at a low pressure, and these two forces act on the free piston 6 simultaneously. Accordingly, two doubled forces act on the free piston 6, improving the response of the free piston 6 to the pulsation of pressure oil, and the first oil passage communicating with the first pressure chamber 7. The pressure oil pulsation can be absorbed and relaxed quickly to smooth the pressure pulsation.

  Thereby, the pulsation of the pressure oil in the first oil passage communicating with the first pressure chamber 7 is reduced, and the pressure oil with the reduced pulsation flows through the oil passage 33. In addition, since the pressure oil with reduced pulsation can be discharged from the pump discharge port 36, various noises generated due to the pulsation of the pressure oil can be reduced. Furthermore, even in the operation of the actuator and the like, it is possible to prevent the occurrence of minute fluctuations and undulations of the actuator accompanying pulsation.

  Due to the resonance operation of the free piston 6, the pulsation of the pressure oil in the oil passage 33 connected to the first pressure chamber 7 is reduced, and the pulsation of the pressure oil in the conduit 35 connected to the second pressure chamber 8 is also reduced. Is done. As a result, it is possible to supply the operation valve with the pressure oil in which the pulsation is smoothed and reduced.

  In FIG. 2 and the subsequent drawings, which will be described below with reference to FIG. 1 and Embodiment 2, the gap formed between the free piston 6 and the inner peripheral surface of the cylinder 5 is exaggerated. The free piston 6 is arranged to be slidable in close contact with the inner peripheral surface of the cylinder 5 as in a normal relationship between the piston and the cylinder. It is what has been.

  Further, the mass of the free piston 6 can be determined for adjusting the reversal time when the reciprocating vibration is caused by the pressure oil introduced into the first pressure chamber 7 and the second pressure chamber 8, respectively. . That is, when the mass increases, the inertial force acts on the free piston to increase, the time required for reversal increases, and the responsiveness as the free piston decreases, but the pulsation reduction performed using the free piston 6 decreases. The stability of the system in the control system for performing

  On the contrary, when the mass is reduced, the time required for inversion is shortened and the responsiveness can be improved. The reversing time of the free piston 6 can be adjusted by adjusting the lengths of the hydraulic hoses 39 and 39 '.

  By the way, if the responsiveness as a free piston becomes high, the free piston 6 will respond sensitively in response to a minute pressure difference between the first pressure chamber 7 and the second pressure chamber 8. For this reason, it is desirable to form the free piston 6 in a mass capable of ensuring the stability required as the pressure pulsation reducing device from the viewpoint of securing the stability as the free piston 6.

  FIG. 2 shows the main part in the vicinity of the cylinder 5, and the entire circuit diagram of the hydraulic circuit including the cylinder 5 is omitted. As the omitted hydraulic circuit diagram, for example, a cylinder according to the second embodiment can be used instead of the cylinder 5 in the hydraulic circuit diagram shown in FIG. The second embodiment is a modification of the cylinder shown in the first embodiment, and is an example in which a cancel mechanism for compensating for the pressure loss due to the second oil passage is provided in the cylinder. About the structure similar to Example 1, the description shall be abbreviate | omitted by using the same member code | symbol as the member code | symbol used in Example 1. FIG.

  In the cylinder 5 of the second embodiment, the pressure loss caused by the pipe resistance or the like while the hydraulic pressure flows through the oil passage 33, the pipe 34 and the pipe 35 from the discharge pressure port 21 which is the second oil passage shown in FIG. A spring 17 that compensates for the minute amount is provided, and a biasing force corresponding to the pressure loss is applied to the free piston 6.

  As a result, the same pressure acts on the pressure receiving surface on the first pressure chamber 7 side and the pressure receiving surface on the second pressure chamber 8 side of the free piston 6, and the free piston 6 is moved in response to pressure fluctuations due to pulsation. Resonance can be activated. By the reciprocating motion of the free piston 6 by this resonance operation, the volume of the first pressure chamber 7 can be increased or decreased, and the pulsation of the pressure oil in the oil passage 33 can be reduced. Moreover, the pulsation of the pressure oil in the pipe line 35 can also be reduced by increasing or decreasing the volume of the second pressure chamber 8. Therefore, the state in which the pulsation of the pressure oil is reduced is maintained even at the branch portion from the pipe line 34 to the pipe line 35, and the pressure oil with the reduced pulsation can be supplied to the operation valve 23.

  FIG. 3 shows the main part in the vicinity of the cylinder 5, and the entire circuit diagram of the hydraulic circuit including the cylinder 5 is omitted. The omitted hydraulic circuit diagram can be configured using, for example, a cylinder according to the third embodiment instead of the cylinder 5 in the hydraulic circuit diagram shown in FIG. The third embodiment is a modification of the cancel mechanism that compensates for the pressure loss in the cylinder shown in the second embodiment. About the structure similar to Example 1, 2, the description shall be abbreviate | omitted by using the same member code | symbol as the member code | symbol used in Example 1,2.

  The cross-sectional shape of the free piston 6 in the third embodiment is such that D1 <D2 where D1 is the diameter of the pressure receiving surface on the first pressure chamber 7 side and D2 is the diameter of the pressure receiving surface on the second pressure chamber 8 side. An area step is formed between the pressure receiving areas. By forming the pressure receiving area of the free piston 6 in the second pressure chamber 8 to be larger than the pressure receiving area of the free piston 6 in the first pressure chamber 7, the pressure loss in the second oil passage is changed to the difference in the pressure receiving area. Can be compensated based on.

  In addition, a drain port 14 is formed at an intermediate portion in the reciprocating sliding of the free piston 6, and the drain port 14 is connected to the tank 20 via a drain oil passage 15.

  Accordingly, similarly to the second embodiment, a cancel mechanism that can cancel the pressure loss due to the second oil passage can be configured. The cancel mechanisms as shown in the second and third embodiments can be configured independently or in combination of both cancel mechanisms.

  FIG. 4 shows the main part in the vicinity of the cylinder 5 part, and the entire circuit diagram of the hydraulic circuit including the cylinder 5 is omitted. The omitted hydraulic circuit diagram can be configured, for example, using a cylinder according to the fourth embodiment instead of the cylinder 5 in the hydraulic circuit diagram shown in FIG. The fourth embodiment shows an example in which the cancel mechanism for compensating for the pressure loss is formed in the cylinder shown in the second and third embodiments by disposing the third pressure chamber 9 connected to the second pressure chamber. is there. About the structure similar to Examples 1-3, the description shall be abbreviate | omitted by using the same member code | symbol as the member code | symbol used in Examples 1-3.

  Between the third pressure chamber 9 and the second pressure chamber 8, a second free piston 16 that defines both pressure chambers is slidably housed in a close state. A spring 18 is interposed between the free piston 6 and the second free piston 16. An oil passage 10 branched from the oil passage 3 is connected to the third pressure chamber 9, and pressure oil having the same pulsation phase as the pressure oil introduced into the first pressure chamber 7 is introduced.

  Strictly speaking, the pulsation phase of the pressure oil introduced into the first pressure chamber 7 and the pulsation phase of the pressure oil introduced into the third pressure chamber 9 do not necessarily coincide with each other depending on the length of the oil passage 10. When the length of the oil passage 10 is extremely short compared to the speed of sound propagating in the oil, even if it is handled that the pulsation phases of the pressure oil introduced into the two pressure chambers are the same, there is no practical problem.

  The second free piston 16 is pressed by the pressure oil introduced into the third pressure chamber 9, and a biasing force can be applied to the free piston 6 via the spring 18 with the amount of movement of the second free piston 16. The biasing force can be a biasing force that compensates for the pressure loss due to the second oil passage. Thereby, the cancellation mechanism which can cancel the pressure loss part by a 2nd oil path similarly to Example 2, 3 can be comprised.

  FIG. 5 shows the main part in the vicinity of the cylinder 5, and the entire circuit diagram of the hydraulic circuit including the cylinder 5 is omitted. As the omitted hydraulic circuit diagram, for example, a cylinder according to the fifth embodiment can be used instead of the cylinder 5 in the hydraulic circuit diagram shown in FIG. The fifth embodiment shows a modification of the cancel mechanism formed by disposing the third pressure chamber 9 connected to the second pressure chamber shown in the fourth embodiment. About the structure similar to Examples 1-4, the description shall be abbreviate | omitted by using the same member code | symbol as the member code | symbol used in Examples 1-4.

  As in the case of the fourth embodiment, a second free piston that defines both pressure chambers is slidably housed in a close state between the third pressure chamber 9 and the second pressure chamber 8. The free piston 6 and the second free piston 16 can be configured separately, or the free piston 6 and the second free piston 16 can be formed integrally.

Even when the free piston 6 and the second free piston 16 are configured separately, the pressure of the pressure oil introduced into the first pressure chamber and the third pressure chamber 9 is introduced into the second pressure chamber 8. Since the pressure is higher than the pressure oil by the pressure loss, the free piston 6 and the second free piston 16 maintain a contact state and perform reciprocation by pulsation.
Thereby, the urging | biasing force which compensates the part for the pressure loss by a 2nd oil path can be provided with respect to the free piston 6 by pressing the 2nd free piston 16 with the pressure oil introduce | transduced into the 3rd pressure chamber 9. FIG. . Therefore, similarly to the second and third embodiments, a cancel mechanism that can cancel the pressure loss due to the second oil passage can be configured.

  FIG. 6 shows the main part in the vicinity of the cylinder 5, and the entire circuit diagram of the hydraulic circuit including the cylinder 5 is omitted. The omitted hydraulic circuit diagram can be configured, for example, by using a cylinder according to the sixth embodiment instead of the cylinder 5 in the hydraulic circuit diagram shown in FIG. Example 6 shows an example of a damper mechanism formed between a free piston and a cylinder. About the structure similar to Examples 1-5, the description shall be abbreviate | omitted by using the same member code | symbol as the member code | symbol used in Examples 1-5.

  A reduced diameter portion is formed at both ends of the free piston 6, and the reduced diameter portion is slidably mounted on the inner diameter portion of the reduced diameter state formed on both ends of the cylinder 5, and is an intermediate portion of the free piston 6. Is installed in the middle part of the cylinder 5 so as to be slidable closely. Further, the pressure receiving area on the second pressure chamber 8 side of the free piston 6 is formed to be larger than the pressure receiving area on the first pressure chamber 7 side, and the pressure loss in the second oil passage is compensated. Yes.

  Pressure chambers 25a and 25b are formed between both ends of the free piston 6 and both ends of the cylinder 5, respectively. The pressure chambers 25a and 25b communicate with the first pressure chamber 7 and the second pressure chamber 8, respectively, through communication holes 28a and 28b and communication holes 27a and 27b formed on both ends of the free piston 6.

  When the communication holes 27a and 27b are closed by the lands 42, the pressure oil in the pressure chambers 25a and 25b is sealed, and a damper mechanism for the free piston 6 is formed. Further, a drain port 14 is formed in the vicinity of the middle portion of the cylinder 5 to keep the reciprocating sliding of the free piston 6 in a smooth state.

  Next, the operation of the damper mechanism will be described. The damper mechanism is formed around the left and right ends of the free piston 6. Since each damper mechanism has the same function, one damper mechanism will be described, and the other damper mechanism will be described. Omitted.

  It is assumed that the free piston 6 is moved leftward in FIG. 6 due to the pulsation of the pressure oil introduced into the first pressure chamber 7 and the second pressure chamber 8. Until the communication hole 27a approaches the land 42, the pressure oil in the pressure chamber 25a is in communication with the first pressure chamber 7 through the communication holes 28a and 27a. When the free piston 6 further moves to the left in FIG. 6, the communication hole 27 a is blocked by the land 42, the opening area of the communication hole 27 a is reduced, and finally the communication hole 27 a is closed by the land 42. It will be.

  When the opening area of the communication hole 27a is closed while being reduced by the land 42, the pressure in the pressure chamber 25a gradually increases and finally increases to a pressure at which the movement of the free piston 6 is stopped. Thus, a damper mechanism for the free piston 6 can be configured. By this damper mechanism, it is possible to prevent the free piston 6 from coming into contact with the end surface of the cylinder 5.

  Subsequently, when the free piston 6 changes the direction of movement due to the pulsation of the pressure oil introduced into the first pressure chamber 7 and the second pressure chamber 8 and moves to the right in FIG. 6, the opening area of the communication hole 27a. As a result, the pressure chamber 25a finally communicates with the first pressure chamber 7 through the communication hole 28a and the communication hole 27a.

  When the free piston 6 moves to the right in FIG. 6 and the end portion of the free piston 6 and the end surface of the cylinder 5 approach each other, the same action as in the above-described damper mechanism is performed, and the end of the free piston 6 It is possible to prevent a collision between the portion and the end surface of the cylinder 5. Thereby, generation | occurrence | production of the collision sound by the collision with the edge part of the free piston 6 and the end surface of the cylinder 5 can be prevented, and generation | occurrence | production of the rebound accompanying free piston 6 colliding with the cylinder 5 can also be prevented. .

  FIG. 7 shows the main part in the vicinity of the cylinder 5, and the entire circuit diagram of the hydraulic circuit including the cylinder 5 is omitted. The omitted hydraulic circuit diagram can be configured, for example, using a cylinder according to the seventh embodiment instead of the cylinder 5 in the hydraulic circuit diagram shown in FIG. The seventh embodiment shows a modification of the damper mechanism formed between the free piston and the cylinder. About the structure similar to Examples 1-5, the description shall be abbreviate | omitted by using the same member code | symbol as the member code | symbol used in Examples 1-5.

  In the seventh embodiment, pressure chambers 25a and 25b are formed between both ends of the free piston 6 and both ends of the cylinder 5, respectively. The pressure chambers 25a and 25b communicate with the first circumferential groove 40a and the second circumferential groove 40b via communication holes 28a and 28b and damper throttles 38a and 38b formed on both end sides of the free piston 6. The first circumferential groove 40 a and the second circumferential groove 40 b communicate with the first pressure chamber 7 and the second pressure chamber 8 that communicate with the oil passages 3 and 35.

  The first circumferential groove 40 a and the second circumferential groove 40 b are respectively formed with stepped areas on the left and right side surfaces of the free piston 6, and the pressure oil introduced into the first pressure chamber 7 and the second pressure chamber 8. The pulsation can be converted into the left and right movement of the free piston 6 by the area step. The pressure receiving area of the first circumferential groove 40a is formed to be smaller than the pressure receiving area of the second circumferential groove 40b, and compensates for the pressure loss due to the length of the second oil passage. Yes.

  A damper mechanism is configured by the communication holes 28a and 28b and the damper stops 38a and 38b. Further, a drain port 14 is formed in the vicinity of the middle portion of the cylinder 5 to keep the reciprocating sliding of the free piston 6 in a smooth state.

  An oil passage 30a branched from the oil passage 3 through a check valve 29a is connected to the pressure chamber 25a. Similarly, a pipeline 30b branched from the pipeline 35 via a check valve 29b is connected to the pressure chamber 25b.

  Next, the operation of the damper mechanism will be described. The damper mechanism is formed around the left and right ends of the free piston 6. Since each damper mechanism has the same function, one damper mechanism will be described, and the other damper mechanism will be described. Omitted.

  It is assumed that the free piston 6 moves to the left in FIG. 7 due to the pulsation of the pressure oil introduced into the first pressure chamber 7 and the second pressure chamber 8. At this time, the pressure of the pressure oil in the pressure chamber 25a is increased by the damper throttle 38a as the free piston 6 approaches, and the check valve 29a is closed as the pressure in the pressure chamber 25a increases.

  At this time, since the pressure chamber 25a communicates with the first pressure chamber 7 through the communication hole 28a, the damper throttle 38a, and the circumferential groove 40a, the pressure oil in the pressure chamber 25a is increased even when the pressure in the pressure chamber 25a is increasing. A part of the gas flows out into the first pressure chamber 7 through the damper throttle 38a. As a result, the pressure in the pressure chamber 25 a is prevented from becoming more than a pressure suitable for preventing the end of the free piston 6 from colliding with the end surface of the cylinder 5.

  From this, it can prevent that the edge part of the free piston 6 and the end surface of the cylinder 5 collide, and the collision sound which generate | occur | produces by collision can be prevented. Further, it is possible to prevent the free piston 6 from rebounding due to the pressure in the pressure chamber 25a.

  Subsequently, when the free piston 6 changes the direction of movement due to the pulsation of the pressure oil introduced into the first pressure chamber 7 and the second pressure chamber 8 and moves to the right in FIG. 7, the check valve 29a is opened. Thus, the pressure oil in the oil passage 3 can be introduced into the pressure chamber 25a via the check valve 29a.

  Even when the free piston 6 moves rightward in FIG. 7 and the end of the free piston 6 and the end surface of the cylinder 5 approach each other, the same operation as the above-described damper mechanism is performed, and the free piston 6 is moved to the cylinder 5. Can be prevented from colliding with the end face of the. Thereby, the collision between the end of the free piston 6 and the end surface of the cylinder 5 can be prevented, and the collision noise generated by the collision between the end of the free piston 6 and the end surface of the cylinder 5 can be prevented. it can. Moreover, the occurrence of rebound can be prevented.

  Since pressure oil can be introduced into the pressure chambers 25a and 25b via the check valves 29a and 29b, for example, when the free piston 6 moves to the right in FIG. 6 can be moved by the pressure of the pressure oil introduced into the first pressure chamber 7 and the pressure of the pressure oil introduced into the pressure chamber 25a.

  Thereby, the pressure receiving area of the free piston 6 on which the pulsation of the introduced pressure oil acts can be increased. In addition, since the pressure oil can be directly introduced into the pressure chambers 25a and 25b via the check valves 29a and 29b, the responsiveness of the free piston 6 that reacts to the pulsation of the pressure oil can be improved.

  The present invention can be applied to a device that needs to reduce the pressure pulsation of the pump discharge pressure in various hydraulic circuits to which the technical idea of the present invention can be applied. it can.

1 is a hydraulic circuit diagram according to an embodiment of the present invention. (Example 1) It is a principal part schematic circuit diagram centering on a cylinder part. (Example 2) It is a principal part schematic circuit diagram centering on a cylinder part. Example 3 It is a principal part schematic circuit diagram centering on a cylinder part. Example 4 It is a principal part schematic circuit diagram centering on a cylinder part. (Example 5) It is a principal part schematic circuit diagram centering on a cylinder part. (Example 6) It is a principal part schematic circuit diagram centering on a cylinder part. (Example 7) It is sectional drawing of a cylinder part. Example 3 It is a hydraulic circuit diagram. (Conventional example 2) It is sectional drawing of the port block of a hydraulic pump. (Conventional example 3)

Explanation of symbols

2 Variable displacement hydraulic pump 3 Oil passage 5 Cylinder 6 Free piston 7 First pressure chamber 8 Second pressure chamber 9 Third pressure chamber 11-13 Inlet port 14 Drain port 16 Second free piston 21 Discharge pressure port 23 Operation valve 25a, b Pressure chamber 27a, b communication hole 28a, b communication hole 32 cylinder block 38a, b damper throttle 39, 39 ′ hydraulic hose 40a, b circumferential groove 42 land 50 hydraulic pump 51 pipeline 52 microprocessor 53 drive source 54 flow generation Device 55 fluid chamber 56 piston 57 pressure sensor 58 second pressure sensor 59 flow path resistance 63 port block 64a, b discharge chamber pressure port,
65a, b Discharge hole 66a, b Passage 67a, b Pressure 68a First pressure absorption chamber 70 Free piston A, B Pulsation waveform D1, D2 Diameter C Correction signal P, L Pressure signal P1, P2 Discharge pressure

Claims (7)

A cylinder 5 defined by a free piston 6 in a first pressure chamber 7 and a second pressure chamber 8;
The first pressure chamber 7 is connected to one discharge pressure port 21 of the hydraulic pump 2 in the vicinity of the discharge pressure port via a first oil passage,
The second pressure chamber 8 is connected to the one discharge pressure port 21 via a second oil passage having a length that reverses the pulsation of pressure oil from the discharge pressure port. Pulsation reduction device.   The pressure pulsation reducing device according to claim 1, wherein the length of the second oil passage is adjustable by hydraulic hoses (39, 39 ').   The pressure pulsation reducing device according to claim 1 or 2, wherein a cancel mechanism for compensating for the pressure loss of the pressure oil guided to the second pressure chamber (8) is formed for the free piston (6).   The pressure pulsation reducing device according to claim 3, wherein the canceling mechanism is configured to bias the free piston 6 toward the first pressure chamber 7.   The pressure pulsation reducing device according to claim 3, wherein the cancel mechanism is configured to form an area step between pressure receiving areas of the free piston 6. A third pressure chamber 9 connected to the second pressure chamber 8 is disposed;
The third pressure chamber 9 is connected to the one discharge pressure port 21 and the third oil passage 10 in the vicinity of the discharge pressure port,
A second free piston 16 is provided between the second pressure chamber 8 and the third pressure chamber 9 to define both pressure chambers;
The pressure pulsation reducing device according to claim 1 or 2, wherein the second free piston (16) compensates for the pressure loss of the pressure oil introduced into the second pressure chamber (8).   The pressure pulsation reducing device according to any one of claims 1 to 6, wherein a damper mechanism for preventing a collision between the free piston 6 and the cylinder 5 is formed.

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