JP2012154277A - Cylinder block - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylinder block for a piston pump capable of restraining pulsation, by optimizing pressure in a cylinder, without reducing work efficiency of a pump.SOLUTION: This cylinder block 7 for the piston pump includes a plurality of cylinder holes 9 arranged at an interval in the peripheral direction and reciprocatably storing a piston and a cylinder port 9A continuously arranged in the respective cylinder holes, and rotates in the predetermined one direction around a rotary shaft. The cylinder block includes communicating passages 18 each connecting the mutually adjacent two cylinder holes. An inlet 21 of the communicating passage is arranged further on a cylinder port side position than the tip of the piston existing in the top dead center on an inner peripheral surface of the one cylinder hole positioned on the upstream side in the rotational direction, and an outlet 22 of the communicating passage is arranged further in a position on the opposite side of the cylinder port than the tip of the piston existing in the bottom dead center on an inner peripheral surface of the other cylinder hole positioned on the downstream side in the rotational direction.

Description

  The present invention relates to a cylinder block used for a piston pump.

  For example, a piston pump as provided in a work machine has conventionally had the following problems. That is, the pressure in the cylinder hole that has sucked the hydraulic oil through the suction port of the valve plate in the suction stroke is lower than the pressure in the discharge port. Further, the pressure in the cylinder hole tends to be negative pressure because the volume in the cylinder hole is slightly expanded until the piston reaches the bottom dead center after the suction stroke is finished. When the cylinder port connected in the cylinder hole begins to communicate with the discharge port, the high pressure oil in the discharge port suddenly flows (backflow) into the low pressure cylinder hole through the cylinder port, resulting in large pressure fluctuations. The pressure fluctuation causes pulsation in the piston, and vibration and noise are generated from the casing via a swash plate or the like. Further, pulsation also occurs in the hose pipe connected to the discharge port, and noise and vibration are also generated from the hose pipe side.

  Conversely, the pressure in the cylinder hole that discharges the hydraulic oil through the discharge port in the discharge stroke is higher than the pressure in the suction port. Further, the pressure in the cylinder hole is further increased by slightly reducing the volume in the cylinder hole until the piston reaches the top dead center after the discharge stroke. When the cylinder port connected to the cylinder hole begins to communicate with the suction port, the high-pressure pressure oil remaining in the cylinder hole flows back into the suction port through the cylinder port. Cannot be sucked into the cylinder hole smoothly, and the pump efficiency tends to decrease.

  Furthermore, as described above, the pressure oil that flows backward from the discharge port into the cylinder hole and the pressure oil that flows backward from the cylinder hole into the suction port form a jet flow that suddenly jets into the cylinder hole or into the suction port, This jet flow may cause erosion or the like in the inner wall portion of the cylinder port or the suction port, and the pump efficiency tends to be lowered from this point. In addition, the lifetime is likely to be greatly reduced.

  As a technique for solving the above-described problems, for example, techniques described in Patent Documents 1 and 2 are known. Patent Document 1 discloses a configuration in which a through port leading to a discharge port is provided in front of one end of a discharge port of a valve plate of an axial piston pump, and a plate spring is provided on the discharge port side of the through port. Yes. According to this configuration, the leaf spring opens the through-hole only when the pressure in the cylinder chamber (cylinder hole) of the cylinder block is higher than the pressure of the discharge port, so the pressure change at the discharge port of the axial piston pump is alleviated. In addition, backflow from the discharge port to the cylinder chamber can be prevented, and the pulsation width can be reduced.

  Patent Document 2 discloses a configuration of a valve plate in which a pressure relief port having first and second pressure relief holes is formed at a position upstream of the suction port in the rotation direction of the cylinder block. Yes. One of the two pressure release holes provided in the valve plate is configured to communicate with the drain discharge place, and the other communicates with the suction port. According to Patent Document 2, it is possible to prevent a jet flow from being generated when the piston chamber is connected to the suction port, to prevent noise, and to prevent erosion of the valve plate.

JP-A-5-44630 JP 2007-9811 A

  However, in the technique described in Patent Document 1, since the structure uses a leaf spring, the leaf spring acts as a vibration source, and the entire valve plate vibrates. There remains a problem that fretting wear may occur between the valve plate and the cylinder block. Further, in the technique described in Patent Document 2, since one of the pressure release holes communicates with the drain discharge place, the hydraulic oil in the cylinder chamber flows out to the outside, so that the work efficiency of the pump is reduced. The problem remains.

  The present invention has been made in view of the above problems, and a purpose thereof is a piston pump capable of optimizing the pressure in the cylinder and suppressing pulsation without lowering the work efficiency of the pump. It is to provide a cylinder block for use.

  In order to achieve the above object, the present invention has a plurality of cylinder holes that are provided at intervals in the circumferential direction and accommodate a piston in a reciprocable manner, and a cylinder port that is connected to each cylinder hole. In the cylinder block for the piston pump that rotates in a predetermined direction around the rotation axis, a communication passage that connects the two cylinder holes adjacent to each other is provided, and the inlet of the communication passage is on the upstream side in the rotation direction. Of the inner peripheral surface of one of the cylinder holes that are positioned, the other end of the communication path that is provided at a position closer to the cylinder port than the tip of the piston at the top dead center is located on the downstream side in the rotational direction. Among the inner peripheral surfaces of the cylinder hole, the cylinder hole is provided at a position on the opposite side of the cylinder port from the tip of the piston at the bottom dead center.

  Further, according to the present invention, in the above configuration, a groove extending in a circumferential direction including the outlet is formed on an inner peripheral surface of the cylinder hole, and a cross section of the groove is directed in a depth direction on the cylinder port side. It is characterized by a substantially semi-elliptical shape with a steep slope and a side opposite to the cylinder port becoming a gentle slope in the depth direction.

  According to the present invention, even when a negative pressure is generated in the cylinder hole when changing from the suction stroke to the discharge stroke, the hydraulic oil is sucked from the adjacent cylinder hole through the communication path, and the pressure in the cylinder hole is reduced. Therefore, the backflow phenomenon of the hydraulic oil from the discharge port into the cylinder hole can be prevented. Furthermore, even when the inside of the cylinder hole becomes a positive pressure (high pressure) when changing from the discharge stroke to the suction stroke, the pressure in the cylinder hole is reduced by flowing the hydraulic oil to the adjacent cylinder hole through the communication path. Therefore, it is possible to prevent the backflow phenomenon of the hydraulic oil from the cylinder hole to the suction port, and as a result, the abnormal pulsation phenomenon can be eliminated. Furthermore, since the hydraulic oil can be supplied to the sliding surface of the piston through the communication path, the lubrication state between the inner peripheral surface of the cylinder hole and the outer peripheral surface of the piston can be kept good.

  Further, according to the present invention, a groove extending in the circumferential direction from the outlet of the communication path is provided, and the cross-sectional shape of the groove is steeply inclined toward the depth direction on the cylinder port side and directed toward the depth direction on the opposite side to the cylinder port. Because it has a semi-elliptical shape with a gentle slope, even if the cylinder bore has a negative pressure, the hydraulic fluid that has flowed through the communication path smoothly flows in the groove and the inner circumferential surface of the cylinder bore. And an oil film can be formed between the outer peripheral surface of the piston. Therefore, the lubrication state of the piston and the cylinder can be kept even better.

It is sectional drawing of the swash plate type hydraulic pump to which the cylinder block which concerns on the 1st Example of this invention was applied. It is the side view which looked at the cylinder block shown in FIG. 1 from the load side. It is the figure which showed the cross section between AA among the cross sections which cut | disconnected and expanded the cylinder block shown in FIG. 2 along the circle (broken line) which passes along the center of each cylinder hole. It is the figure which showed the positional relationship of the piston and cylinder hole accompanying rotation of the cylinder block shown in FIG. It is a figure for demonstrating the flow of the hydraulic fluid in a cylinder hole in (i) and (a) of FIG. It is a figure for demonstrating the flow of the hydraulic fluid in a cylinder hole in (d) and (e) of FIG. It is the external view which looked at the cylinder hole shown in FIG. 2 from the B direction. It is the figure which expanded a part of section of the cylinder block concerning the 2nd example of an embodiment of the present invention. It is the external view which looked at the cylinder hole shown in FIG. 8 from the B direction. It is XX sectional drawing of FIG. (A) is a YY sectional view of FIG. 9, (b) is an enlarged sectional view of a main part for explaining the relationship between the sectional shape of the communication path and the groove, and (c) is a sectional view of the groove. is there. It is the figure which expanded a part of cross section of the cylinder block which concerns on the 3rd Example of this invention. It is the external view which looked at the cylinder hole shown in FIG. 12 from the B direction.

  Hereinafter, an example in which the cylinder block according to the first embodiment of the present invention is applied to a swash plate type hydraulic pump will be described with reference to FIGS. Needless to say, the present invention can be applied not only to the swash plate type hydraulic pump but also to a piston pump such as a swash shaft type or a radial piston type.

  In the figure, reference numeral 1 denotes a casing of a swash plate type hydraulic pump. The casing 1 is composed of a bottomed cylindrical casing body 1A that is open at one end in the axial direction, and a rear casing 1B that closes the open end of the casing body 1A. When the rear casing 1B is attached to the casing body 1A, a sealed housing space is formed inside the casing 1. Various components constituting the swash plate type hydraulic pump are mounted in the housing space. Hereinafter, various components mounted in the accommodation space will be described.

  Reference numeral 2 denotes a swash plate, on which a sliding surface is formed on which a shoe 12 described later is in sliding contact. Reference numeral 3 is a valve plate fixed to the inner surface of the rear casing 1B. The valve plate 3 is provided with a discharge port 4A and a suction port 4B formed by cutting out in an arc shape symmetrically, and the discharge port 4A includes a discharge passage provided in the rear casing 1B, and a suction port. The ports 4B communicate with the supply passages of the rear casing 1B. Reference numeral 5 denotes a rotating shaft that is rotatably supported by the casing 1 via respective bearings. The rotating shaft 5 penetrates through the central portions of the swash plate 2 and the valve plate 3, and one end 5 </ b> A side thereof protrudes outward from the casing 1. Note that one end 5A of the rotary shaft 5 is connected to a motor or engine drive shaft (not shown) via a coupling.

  Reference numeral 7 denotes a cylinder block connected to the rotary shaft 5 via a spline 8, and this cylinder block 7 is disposed in the casing 1 so that one side surface faces the swash plate 2, The other side is in sliding contact with the valve plate 3. Reference numeral 9 denotes a cylinder hole formed in the cylinder block 7 in the axial direction. A plurality (specifically, nine) of cylinder holes 9 are arranged at a constant interval on the same circumference around the rotation shaft 5. Each of the plurality of cylinder holes 9 has an open end on one end side, and a cylinder port 9A communicating with the discharge port 4A and the suction port 4B of the valve plate 3 on the other end side.

  Reference numeral 10 denotes a piston inserted in each cylinder hole 9 so as to be reciprocally movable. Each piston 10 has a hollow interior, and the hydraulic oil in the cylinder hole 9 is pressurized as the piston 10 reciprocates in the cylinder hole 9. Reference numeral 15 denotes a retainer disposed between the swash plate 2 and the cylinder block 7. The retainer 15 is formed in an annular shape, and a presser member urged by a spring 17 from the cylinder block 7 side is in contact with the periphery of the center insertion hole. In the retainer 15, a plurality of shoe support holes are formed as circular holes having a constant interval in the circumferential direction. When each shoe 12 is mounted in each shoe support hole, the sliding contact portion 14 of each shoe 12 is pressed toward the swash plate 2 by the urging force of the spring 17.

  Reference numeral 18 shown in FIGS. 3, 4, etc. is a communication path that connects two cylinder holes 9 adjacent to each other in the cylinder block 7. This communication path 18 is located further on the cylinder port 9A side than the tip of the piston 10 at the top dead center on the inner peripheral surface of one cylinder hole 9 located on the upstream side in the rotational direction (left side in FIG. 4). That is, among the inlet 21 provided in the region D) in FIG. 4 and the inner peripheral surface of the other cylinder hole 9 located on the downstream side in the rotational direction (right side in FIG. 4), The hydraulic oil in the cylinder hole 9 flows from the inlet 21 to the outlet 22. The outlet 22 is provided at a position opposite to the cylinder port 9 </ b> A (ie, region C in FIG. 4) from the tip. Thus, it is possible to flow between the cylinder holes 9. Here, the region C is a region where the inner peripheral surface of the cylinder hole 9 and the outer peripheral surface of the piston 10 are always in contact when the piston 10 reciprocates, and the region D is a cylinder when the piston 10 reciprocates. It can also be said that the inner peripheral surface of the hole 9 and the outer peripheral surface of the piston 10 are regions that do not always contact.

  The communication path 18 is formed with a minute diameter (for example, several millimeters) to the extent that the hydraulic oil is not hindered from being pressurized to a predetermined pressure. Further, the corners of the inlet 21 and the outlet 22 of the communication path 18 are chamfered to suppress the occurrence of cavitation and the like.

  The swash plate type hydraulic pump configured as described above is inserted into the cylinder hole 9 by transmitting the rotational force from the engine and the motor to the rotary shaft 5, rotating the cylinder block 7, and rotating the cylinder block 7. The piston 10 also reciprocates. The shoe 12 at the rear end of the piston 10 slides on the swash plate 2, and the piston 10 is pushed and moved toward the swash plate 2 in the cylinder hole 9 (see FIGS. 4A to 4E). . At this time, the volume in the cylinder hole 9 increases so that hydraulic oil is supplied into the cylinder hole 9 from the suction port 4B of the valve plate 3 (suction stroke). By continuously rotating the rotating shaft 5, the piston 10 is gradually pushed and moved toward the valve plate 3 in the cylinder hole 9 (see (e) to (i) of FIG. 4). At this time, since the volume of the cylinder hole 9 is reduced, the hydraulic oil is discharged from the inside of the cylinder hole 9 through the discharge port 4A of the valve plate 3 (discharge stroke).

  Here, if the communication passage 18 is not provided, the discharge port 4A and the suction port 4B of the valve plate 3 are separated from each other. Therefore, in the range E and F in FIG. It remains confined within 9. Therefore, in the range of E in FIG. 4, the piston 10 is displaced to the position of FIG. 4 (e), which is the bottom dead center, thereby generating a negative pressure in the cylinder hole 9. In the range of F in FIG. 4 is displaced to the position of FIG. 4 (i), which is the top dead center, and positive pressure is generated in the cylinder hole 9. However, in this embodiment, since the adjacent cylinder holes 9 are connected by the communication path 18, the above-described negative pressure and positive pressure can be suppressed. This will be described in detail below with reference to FIGS.

  First, the operation in the range of F in FIG. 4 will be described with reference to FIG. In the range of F, as described above, when the piston 10 is displaced to the top dead center, the pressure in the cylinder hole 9 shown in FIG. 5I increases. At this time, the hydraulic oil in the cylinder hole 9 of FIG. 5 (i) whose pressure has increased flows from the inlet 21 through the communication passage 18, and is downstream in the rotation direction of the cylinder block 7 (the movement direction of the cylinder block). 5, that is, the outlet 22 of the cylinder hole 9 shown in FIG. 5A, and enters a slight gap between the inner peripheral surface of the cylinder hole 9 and the outer peripheral surface of the piston 10. Therefore, the pressure increase in the cylinder hole 9 in FIG. 5 (i) is alleviated, and the cylinder hole 9 is maintained in an appropriate state.

  Next, the range of E in FIG. 4 will be described with reference to FIG. In the range of E, as described above, the piston 10 is displaced to the bottom dead center, whereby a negative pressure is generated in the cylinder hole 9 (state (e) in FIG. 6). In this state, the pressure in the cylinder hole 9 shown in FIG. 6D is larger than the pressure in the cylinder hole 9 shown in FIG. The hydraulic oil in the upstream cylinder hole 9 in the rotational direction of the cylinder 7 (the movement direction of the cylinder block) flows through the communication path 18 from the inlet 21 and flows out to the outlet 22 of the downstream cylinder hole 9. It enters a slight gap between the inner peripheral surface of the hole 9 and the outer peripheral surface of the piston 10. Therefore, the negative pressure in the cylinder hole 9 in FIG. 6 (e) is relieved, and the cylinder hole 9 is maintained in an appropriate state.

  As described above, in the cylinder block 7 according to the first embodiment, the pressure fluctuation in the adjacent cylinder holes 9 is alleviated by the communication path 18, so that the work efficiency of the hydraulic pump is not lowered. Further, since pressure fluctuation can be suppressed, vibration and noise caused by this can be prevented. In addition, according to the cylinder block 7 according to the first embodiment, the lubrication state between the cylinder hole 9 and the piston 10 can be maintained well, so that it is possible to prevent a decrease in life.

  Next, the cylinder block according to the second embodiment will be described with reference to FIGS. 8 to 11. The same reference numerals are used for the same components as those of the cylinder block according to the first embodiment. The description is omitted.

  As shown in FIGS. 8 and 9, the cylinder block 107 according to the second embodiment includes the outlet 22 of the communication path 18, and the groove 119 makes one round in the circumferential direction along the inner peripheral surface of the cylinder hole 9. There is a big feature in the point formed. As shown in FIGS. 10 and 11, the groove 119 has a substantially semi-elliptical cross-sectional shape. More specifically, as shown in FIG. 11 (c), the cross section of the groove 119 is a steep slope from the deepest part to the cylinder port 9A side (lower side in the figure) in the depth direction. The opposite side (the upper side in the figure) has a substantially semi-elliptical shape with a gentle slope in the depth direction. 11B, the angle formed by the gentle slope of the groove 119 and the inner peripheral surface of the cylinder hole 9 is substantially the same as the angle θ at which the communication path 18 enters the cylinder hole 9. Yes.

  According to the cylinder block 107 according to the second embodiment configured as described above, by forming the groove 119 on the inner peripheral surface of the cylinder hole 9, the following effects can be obtained. That is, the most severe sliding state between the piston 10 and the cylinder hole 9 of the swash plate type hydraulic pump occurs when the piston 10 moves out of the cylinder hole 9 (during the intake stroke) and is negative in the cylinder hole 9. Since the pressure is generated, the oil film becomes thin between the piston 10 and the inner peripheral surface of the cylinder hole 9. At this time, the hydraulic oil flows into the cylinder hole 9 having a negative pressure through the communication path 18, but the cross section of the groove 119 has a shape as shown in FIG. In the portion where the outlet 22 of the communication passage 18 merges with the groove 119, it flows smoothly in the groove 119 along the direction of the arrow in FIG. An oil film can be formed between the piston 10. Therefore, even if the inside of the cylinder hole 9 becomes a negative pressure, the lubrication state between the cylinder hole 9 and the piston 10 is kept good.

  Next, a cylinder block according to a third embodiment will be described with reference to FIG. 12 and FIG. 13. The same reference numerals are used for the same configurations as the cylinder block according to the first embodiment. The description is omitted.

  As shown in FIGS. 12 and 13, the cylinder block 207 according to the third embodiment includes a groove 219 in the circumferential direction along the inner peripheral surface of the cylinder hole 9 including the outlet 22 of the communication passage 18. It has a great feature in that it is formed only by a length (specifically, a length of approximately ¼ circumference). The cross-sectional shape of the groove 219 is the same as that of the groove 119 (see FIGS. 10 and 11) formed in the second cylinder block 107, and the description thereof is omitted here.

  According to the cylinder block 207 according to the third embodiment configured as described above, the cylinder block 107 according to the second embodiment is formed by forming the groove 219 on the inner peripheral surface of the cylinder hole 9. Similarly, an oil film can be formed between the inner peripheral surface of the cylinder hole 9 and the piston 10. Therefore, even if the inside of the cylinder hole 9 becomes negative pressure, the lubrication state between the cylinder hole 9 and the piston 10 is maintained well.

  Of the cross-sectional shapes of the grooves 119 and 219, the steep slope can be configured as a surface that is substantially orthogonal to the sliding surface (that is, a surface that rises substantially at a right angle). be able to.

5 Rotating shaft 7, 107, 207 Cylinder block 9 Cylinder hole 9A Cylinder port 10 Piston 18 Communication path 21 Inlet 22 Outlet 119, 219 Groove

Claims (2)

A plurality of cylinder holes that are provided at intervals in the circumferential direction and accommodate a piston so as to be reciprocally movable, and a cylinder port that is connected to each cylinder hole, and rotates in a predetermined direction around the rotation axis. In the cylinder block for the piston pump
Providing a communication path connecting the two cylinder holes adjacent to each other;
The inlet of the communication path is provided at a position closer to the cylinder port than the tip of the piston at the top dead center, of the inner peripheral surface of one cylinder hole located on the upstream side in the rotation direction,
The outlet of the communication path is provided at a position further on the opposite side to the cylinder port than the tip of the piston at the bottom dead center on the inner peripheral surface of the other cylinder hole located on the downstream side in the rotation direction. A featured cylinder block. In the description of claim 1,
On the inner peripheral surface of the cylinder hole, a groove extending in the circumferential direction including the outlet is formed,
The cross section of the groove has a substantially semi-elliptical shape in which the cylinder port side is a steep slope in the depth direction and the opposite side to the cylinder port is a gentle slope in the depth direction.

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