KR101330768B1 - Cooling structure of cylinder block and swash plate type liquid-pressure apparatus including same - Google Patents

Abstract

It provides a cooling structure of the cylinder block 12 that can improve the cooling performance of the sliding surface. The cylinder block 12 has the some cylinder 20 in which the piston 13 is inserted in the cylinder 20 in the opening. The piston 13 is configured to reciprocally slide over the sliding surface 12b defining the cylinder 20. In addition, a plurality of cooling grooves 31 are formed on the outer circumferential surface 12a of the cylinder block 12. The cooling groove 31 extends in the front end face to the partition 32 between two adjacent cylinders 20 and further reduces the thickness t between the sliding surface 12b and the outer circumferential surface 12a. It is formed by reducing the thickness of the partition wall (32).

Description

COOLING STRUCTURE OF CYLINDER BLOCK AND SWASH PLATE TYPE LIQUID-PRESSURE APPARATUS INCLUDING SAME}

According to the present invention, a plurality of cylinders each capable of inserting a piston in an opening at a piston insertion side end face are formed, and when rotated, a cylinder in which the inserted piston is reciprocally sliding the cylinder. It relates to a cooling structure of a cylinder block, for example, a cylinder block of a swash plate type hydraulic device.

In an industrial machine including a construction machine, various hydraulic motors and hydraulic pumps are used, and as this hydraulic motor or hydraulic pump, for example, a swash plate type hydraulic motor pump such as Patent Document 1 ( Hereinafter, "also called a swash plate type hydraulic device" is known. The swash plate type hydraulic device of patent document 1 is provided with the rotating shaft, and the cylinder block is integrally couple | bonded with the rotating shaft. Cylinders are formed in the end face of the cylinder block at equal intervals in the circumferential direction, and pistons are inserted into the respective cylinders. A shoe is coupled to an end projecting from the cylinder, and the shoe is disposed on the support surface of the swash plate which is inclined.

The swash plate type hydraulic device configured as described above is configured to rotate the cylinder block by reciprocating the piston in the cylinder.The cylinder block is rotated by supplying a high-pressure hydraulic fluid to the cylinder to reciprocate the piston so that the rotating shaft is integrally installed. It can be rotated. That is, the swash plate hydraulic device operates as a hydraulic motor. In addition, the swash plate type hydraulic device is configured to rotate the cylinder block so that the piston reciprocates in the cylinder, and rotates the cylinder block by the rotating shaft to suck the low pressure hydraulic oil and discharge the high pressure hydraulic oil. That is, the swash plate type hydraulic device can also be operated as a hydraulic pump.

Japanese Patent Application Laid-Open No. 2010-174690

Although the swash plate type hydraulic device having the same configuration as that of Patent Document 1 is mainly used at low speed and medium speed rotation, the swash plate type hydraulic device may be used even at high speed rotation in order to cope with high rotation of the driving device of construction machinery or industrial machinery. It is desirable to be able to. However, when the swash plate hydraulic device rotates the cylinder block at high speed, the influence of the centrifugal force acting on the piston and the shoe increases, so that the influence of the centrifugal force cannot be ignored, unlike at low rotation.

For example, when the piston reciprocates with the cylinder, heat is generated by sliding on the sliding surface of the cylinder block in which the piston slides, and the amount of heat generated here depends on the contact pressure between the cylinder block and the piston. In the low-rotation specification of which the centrifugal force is considerably small as in the prior art, since the contact pressure mainly corresponds to the pressure of the hydraulic oil supplied or discharged, the heat generated on the sliding surface is relatively small. Therefore, a clearance for sending hydraulic oil is formed between the sliding surface and the piston, so that the sliding surface can be sufficiently cooled only by the hydraulic oil leaking from it.

However, when the cylinder block is rotated at a high speed, the centrifugal force side affects the contact pressure more than the influence of the hydraulic pressure. As the rotation speed increases, the contact pressure increases, and the amount of heat generated on the sliding surface also increases. Thereby, since the temperature of a sliding surface rises and it becomes difficult to cool especially by the hydraulic fluid which leaks in clearance, the temperature rise of the opening vicinity of a cylinder becomes remarkable. Further, the centrifugal force increases and the piston is pushed outward, whereby the clearance width on the outside thereof becomes narrower than the radially inner side of the cylinder block. This makes it difficult for the hydraulic oil in the narrowed outer clearance to flow, thus heating the hydraulic oil. If the hydraulic oil continues to be heated to exceed the transition temperature of the hydraulic oil, the lubricating performance of the hydraulic oil is lowered. As a result, the amount of heat generated on the sliding surface is further increased, and the cylinder and the piston can be pressed together. It is also possible to prevent a decrease in lubrication performance and seizure of the hydraulic fluid by increasing the clearance width, but increasing the clearance width greatly increases the leakage of the hydraulic oil, which reduces the performance as a pump or a motor. There is a limit to high pressure.

Therefore, an object of the present invention is to provide a cooling structure of a cylinder block which can improve the cooling performance of the sliding surface.

The cooling structure of the cylinder block of the present invention includes a cylinder block having a plurality of cylinders having openings in an end surface of the piston insertion side and, when rotated, the pistons respectively inserted into the cylinders reciprocally slide, and an outer circumferential surface of the cylinder block. It has a plurality of cooling grooves formed in the groove, the cooling groove extends from the end surface of the piston insertion side to the partition wall between two adjacent cylinders, the sliding surface on which the piston slides and the outer peripheral surface of the cylinder block It is formed by reducing the thickness of the partition wall so as to reduce the thickness therebetween.

According to the present invention, the thickness between the sliding surface and the outer peripheral surface becomes small. Since the sliding surface near the outer circumference generated by the centrifugal force under high speed rotation is higher than the temperature of the drain oil in the surrounding case, the heat generated from the sliding surface is quickly transferred to the outer circumferential surface and dissipated from the outer circumferential surface ( You can do it. Thereby, the cooling performance of a sliding surface can be improved and the temperature rise of a sliding surface can be suppressed. Moreover, since the cooling groove extends in the piston insertion side end face with the opening of the cylinder, the increase in the surface temperature can be particularly suppressed in the vicinity of the piston insertion side end face of the sliding surface where the temperature rise is most significant. Therefore, the occurrence of pressing of the sliding surface can be suppressed.

For example, when this invention is used for hydraulic devices, such as a hydraulic pump and a hydraulic motor, clearance is provided between a sliding surface and the outer peripheral surface of a piston, and the hydraulic oil which leaks by this clearance is used as lubricating oil. By suppressing the temperature rise of the sliding surface, it is possible to suppress the temperature rise of the lubricating oil and prevent the lubricating oil from transferring. Thereby, since the fall of the lubricating performance of lubricating oil can be prevented, it can maintain smooth operation | movement of a piston, and can reduce the heat quantity in a sliding surface.

In the above invention, the piston reciprocates between a top dead center and a bottom dead center of the cylinder, and the cooling groove extends in parallel with the cylinder at the piston insertion side end surface. It is preferable that the tip is formed so as to be located at the piston insertion side end face rather than near the end face in the cylinder of the piston located at the bottom dead center.

According to the said structure, the cooling performance of the area | region which surface temperature becomes high can be improved, maintaining the rigidity of the part which becomes high pressure when a piston is located in bottom dead center. Accordingly, it is possible to prevent breakage due to the sticking of the cylinder and the piston without lowering the use limit pressure of the working liquid supplied to the cylinder block.

In the above invention, the cooling groove is preferably formed such that the minimum thickness tmin between the outer peripheral surface of the cylinder block and the sliding surface is 0.02D ≦ tmin ≦ 0.3D with respect to the inner diameter D of the cylinder. Do.

According to the said structure, rigidity in the area | region on the outer peripheral surface side of a sliding surface can be ensured, improving a cooling effect. Thereby, the pressurization of a cylinder block and the damage on an opening side can be prevented.

The swash plate type hydraulic device of the present invention is connected to a low pressure side passage through which a low pressure working liquid flows and a high pressure side passage through which a high pressure working liquid flows, and the operating liquid is supplied to the cylinder from the high pressure side passage, By discharging to the low pressure side passage to rotate the cylinder block or by rotating the cylinder block, the hydraulic fluid is sucked from the low pressure side passage to the cylinder and further compressed, and then discharged to the high pressure side passage. It has a cooling structure of a cylinder block.

In the swash plate type hydraulic device, a clearance is provided between the sliding surface and the outer circumferential surface of the piston, and the hydraulic oil leaking out of the clearance is used as lubricating oil. According to the above configuration, by suppressing the temperature rise of the sliding surface, it is possible to suppress the rise of the oil temperature of the lubricating oil leaking out of the clearance and to prevent the lubricating oil from transferring. As a result, the degradation of the lubricating performance of the lubricating oil can be prevented, and smooth operation of the piston can be maintained, and the amount of heat generated on the sliding surface can be reduced.

In the above invention, it is preferable to have a casing for accommodating the cylinder block, and the inside of the casing is connected to the low pressure side passage through a communication path, and the low pressure hydraulic oil of the low pressure side passage is guided in the casing.

According to the said structure, since the outer peripheral surface of a cylinder block can be wetted with the low pressure and low temperature hydraulic oil guide | induced in a casing, the said outer peripheral surface can be cooled by a working liquid. As a result, more heat can be dissipated from the outer circumferential surface, so that an increase in the surface temperature of the sliding surface can be further suppressed.

According to this invention, the cooling performance of a sliding surface can be improved.

1 is a cross-sectional view showing a swash plate hydraulic device according to an embodiment of the present invention.
FIG. 2 is a front view of the cylinder block provided in the swash plate hydraulic device shown in FIG.
3 is a cross-sectional view of the cylinder block taken along the cutting line AA shown in FIG. 2.
4 is an example of a hydraulic circuit diagram around the swash plate type hydraulic device.
(A) is a figure which shows the piston in bottom dead center, (b) is a graph which shows the surface temperature of each position of the sliding surface of the cylinder block in the state (a), (c) is (a) It is a graph showing the hydraulic pressure of the sliding surface of the cylinder block in the) state.
6 is a front view showing the cooling structure of the cylinder block of another embodiment.

Hereinafter, the swash plate type hydraulic device 1 according to the embodiment of the present invention will be described with reference to the above-mentioned drawings. In addition, the swash plate type hydraulic device 1 described below is only one embodiment of the present invention, and the present invention is not limited to the above embodiment, and additions, deletions, and changes may be made without departing from the spirit of the present invention. It is possible.

[Swash Plate Type Hydraulic Device]

For construction machinery such as hydraulic shovels, cranes and bulldozers, and for industrial machinery and ships such as hydraulic units, presses, steel machines and injection molding machines In order to drive the apparatus and the actuator (actuator) provided therein, a swash plate type hydraulic device 1 is provided. The swash plate type hydraulic device 1 is a so-called swash plate type motor / pump, and operates the actuator by supplying pressurized liquid to a function of a hydraulic motor that rotates a rotating object provided in an industrial machine or a ship, or an actuator provided in an industrial machine or a ship. It has the function of hydraulic pump. In addition, in the following description, the swash plate type | mold hydraulic device 1 is demonstrated as a hydraulic motor using the fluid to be handled for the convenience of description.

The hydraulic motor 1 which is the swash plate type hydraulic device 1 is a high speed rotary hydraulic motor which has the rotating shaft 11 and can rotate the rotating shaft 11 by a high speed as shown in FIG. This hydraulic motor 1 is provided with the cylinder block 12, the some piston 13, the some shoe 14, the swash plate 15, and the valve plate 16 in addition to the rotating shaft 11, These parts It is housed in this casing 17. The rotary shaft 11 extends in the front-rear direction so as to penetrate the casing 17, and is rotatably supported by the bearings 18 and 19 at the front end and the rear end of the casing 17. The cylinder block 12 is fitted in the intermediate | middle part of the rotating shaft 11 at the rear end side.

The cylinder block 12 is formed in substantially cylindrical shape, and is positioned so that the axis line may coincide with the axis line L1 of the rotating shaft 11. The cylinder block 12 is integrally coupled by the rotation shaft 11 and spline coupling, and is comprised so that relative rotation with respect to the rotation shaft 11 may not be possible. The front end part of the outer peripheral surface 12a of this cylinder block 12 is reduced in thickness radially inward over the whole circumference, and the cooling structure 30 is further formed. The detailed description of this cooling structure 30 is mentioned later. In addition, a plurality of cylinders 12 are formed in the cylinder block 12. The cylinders 20 are arranged at equal intervals in the circumferential direction, as shown in FIG. 2, and extend parallel to the axis L1 as shown in FIG. 3. The cylinder 20 is a hole defined by the sliding surface and bottom face of circular cross section, and has an opening in the front end surface (piston insertion side end surface) of the cylinder block 12. As shown in FIG. In each cylinder 20, the piston 13 is inserted and inserted in the opening.

The piston 13 has a large cylindrical shape, and is reciprocally slid in the front-rear direction while sliding on the sliding surface 12b defining the cylinder 20. In addition, the cylinder 20 may be fitted with a cylindrical sleeve (not shown), such as a copper bush. In this case, the piston 13 slides on the inner circumferential surface of the sleeve, and the sliding surface on which the piston 13 slides means the inner circumferential surface of the sleeve. Hereinafter, although the case where the sleeve is not inserted is demonstrated, it is the same also when the sleeve is fitted.

The outer diameter of the piston 13 is slightly smaller than the inner diameter of the cylinder 20, and a clearance is formed between this and the sliding surface 12b around the piston 13. As shown in FIG. In addition, the piston 13 has a spherical holder 13a at its front end, and the spherical holder 13a protrudes from the cylinder 20 regardless of the position of the piston 13. The outer surface of the spherical holder 13a is formed on a substantially spherical surface, and the shoe 14 is coupled thereto.

The shoe 14 is formed in a substantially cylindrical shape having a bottom, and its inner surface corresponds to the spherical holding portion 13a and is formed in a partial spherical shape. The spherical holding part 13a of the piston 13 fits in this shoe 14, and the piston 13 is comprised so that rotation is possible centering on the center of the spherical holding part 13a. In addition, the shoe 14 has a flange 14a protruding radially outward from the bottom thereof, and the bottom 14 is disposed on the bottom plate in contact with the swash plate 15.

The swash plate 15 is formed in a substantially disk shape. The swash plate 15 is provided in the casing 17 with the upper side inclined backward, and the rotation shaft 11 penetrates around the center thereof. The swash plate 15 is disposed in front of the cylinder block 12 and has a support plate 21 on the cylinder block 12 side. The support plate 21 is formed in a circular shape, and a plurality of shoes 14 are arranged at equal intervals in the circumferential direction. Moreover, the press plate 22 is provided in the some shoe | curd 14 so that these may press and adhere to the support plate 21.

The pressing plate 22 is formed in a substantially circular shape, and the rotary shaft 11 is inserted through the center thereof so as to be relatively rotatable. The press plate 22 is provided with the same number of engaging holes 22a as the shoe 14, and the engaging holes 22a are arranged at equal intervals in the circumferential direction. The pressing plate 22 is made to contact the flange 14a by inserting the opening side of the shoe 14 into the coupling hole 22a, and is made to cooperate with the support plate 21, and to sandwich the flange 14a between them. Moreover, the spherical bush 23 is inserted through the inner hole of the press plate 22. The spherical bush 23 is substantially cylindrical, and is sheathed on the rotating shaft 11 and the cylinder block 12. The spherical bush 23 is urged toward the support plate 21 by a plurality of pressure springs 40 provided on the cylinder block 12, and the pressing plate 22 is supported by the spherical bush 23. It is pressed against 21 and is in close contact.

Thus, the swash plate 15 in which the plurality of shoes 14 are arranged is connected to the regulator 24 provided at the upper portion of the casing 17. The regulator 24 has a plunger 25 which moves in the front-back direction, and the swash plate 15 is connected to this plunger 25. Therefore, by operating the plunger 25 in the front-rear direction, the inclination angle of the swash plate can be changed to adjust the stroke of the piston 13, and the capacity of the oil chamber 20a of the cylinder 20 can be changed. The oil chamber 20a is a space which is rearward of the rear end surface of the piston 13 in the cylinder 20.

The cylinder port 26 connected to this oil chamber 20a is formed in the cylinder block 12. The cylinder port 26 is provided one by one in a cylinder, and corresponds one to one with the cylinder. The cylinder port 26 is opened at the rear end face of the cylinder block 12, and a valve plate 16 is provided at the rear end face.

The valve plate 16 is a circular plate-shaped member and is located between the cylinder block 12 and the rear end of the casing 17. The valve plate 16 is fixed to the casing 17 so as not to rotate relative to the casing 17 by a pin member (not shown). The rotating shaft 11 is inserted through the inner hole of the valve plate 16, and the rotating shaft 11 and the valve plate 16 are comprised so that relative rotation is mutually possible. The suction port 16a and the discharge port 16b are formed in the valve plate 16 located in this way.

The suction port 16a and the discharge port 16b are substantially arc-shaped, and are spaced apart from each other in the circumferential direction. These suction ports 16a and discharge ports 16b penetrate the valve plate 16 in the thickness direction thereof, and the opening on the cylinder block 12 side is connected to several cylinder ports 26, and the cylinder block ( By rotating 12, the connection line of the cylinder port 26 is alternately switched between the suction port 16a and the discharge port 16b. In addition, the other side opening of the suction port 16a is connected to the high pressure side passage 27 shown in FIG. 4, and the opening of the discharge port 16b is connected to the low pressure side passage 28 shown in FIG. 4. . In other words, by rotating the cylinder block 12, the cylinder 20 is alternately connected to the high pressure side passage 27 and the low pressure side passage 28. As shown in FIG. In addition, in FIG. 1, the position of the suction port 16a and the discharge port 16b is moved to the circumferential direction, and described for the convenience of description. And the circuit structure shown in FIG. 4 is an example for further improving a cooling effect, and even without this structure, a cooling effect can be acquired by the oil in a case.

Moreover, the communication path 29 shown in FIG. 4 is formed in the casing 17, and the inside of the casing 17 and the low pressure side passage 28 are connected by this communication path 29. Accordingly, a certain amount of the working oil flowing through the low pressure side passage 28 is guided into the casing 17 through the communication path 29 to be used as the cooling liquid. The rotating shaft 11 and the cylinder block 12 are operated by the low pressure and low temperature working oil. ) And the piston 13 can be cooled.

In the hydraulic motor 1 having such a configuration, the piston 13 moves from the top dead center where the piston 13 is most compressed and retracted from the cylinder 20 to the bottom dead center where the piston 13 protrudes most from the cylinder 20. The hydraulic oil flowing through the high pressure side passage 27 is sucked into the oil chamber 20a through the suction port 16a. As a result, the piston 13 is pushed forward by the hydraulic oil, and as a result, the shoe 14 is pressed against the swash plate 15 to be in close contact. Since the swash plate 15 is inclined, the shoe 14 pressed and in close contact with each other is lubricated so as to slide down on the swash plate 15, and revolves around the axis L1 in one circumferential direction. Thereby, the rotational force around the axis L1 is applied to the cylinder block 12, and the cylinder block 12 and the rotating shaft 11 rotate around the axis L1.

On the other hand, when the piston 13 is located between the bottom dead center and the top dead center, the oil chamber 20a is connected to the low pressure side passage 28 through the discharge port 16b. As the cylinder block 12 rotates, lubrication moves on the swash plate 15 so that the shoe 14 rises upward, and also revolves around the axis L1 in one circumferential direction. As the shoe 14 is raised upward, the piston 13 is pushed back to return the hydraulic oil of the oil chamber 20a to the low pressure side passage 28 through the discharge port 16b. In this way, the hydraulic motor 1 reciprocates the piston 13 in the front-rear direction by sucking and discharging the hydraulic oil, thereby rotating the cylinder block 12 and the rotating shaft 11 around the axis L1.

Thus, in the hydraulic motor 1 which repeats suction discharge of hydraulic fluid, as mentioned above, the piston 13 slides on the sliding surface 12b at the time of rapid discharge, and reciprocally slides back and forth. For this reason, frictional heat generate | occur | produces in the sliding surface 12b at the time of sliding, and the surface temperature of the sliding surface 12b, especially the area | region of an opening side rises. A clearance is provided between the outer surface of the piston 13 and the sliding surface 12b, and lubrication of the piston 13 by using the hydraulic oil leaking from this clearance as lubricating oil reduces the frictional heat generated in the sliding surface 12b. At the same time, the sliding surface 12b is cooled by the lubricating oil. In this way, the hydraulic motor 1 provides a clearance to suppress the increase of the surface temperature at the sliding surface 12b, but the cooling structure 30 of the cylinder block 12 is further suppressed to further increase the surface temperature. Have more.

<Cooling structure of the cylinder block>

The cooling structure 30 of the cylinder block 12 has a cooling groove 31. The cooling grooves 31 are respectively formed in the partitions 32 between two adjacent cylinders 20, as shown in FIG. 2, from the front end face of the cylinder block 12 toward the rear end face. It extends parallel to the axis L1. In this embodiment, the front end of the cooling groove 31 is located at the front end surface side of the cylinder block 12, that is, at the bottom dead center, rather than near the rear end surface of the piston 13 located at the bottom dead center. It is located in the front side rather than in the vicinity of the rear end face of the (). In addition, the partition 32 means the whole wall between the straight lines L2 and L3 which respectively extend to the outer peripheral surface 12a through the center of the two adjacent cylinders 20 from the center of the cylinder block 12 ( Region shown by a rhombic network in FIG. 2).

5B and 5C are graphs showing the surface temperature and the hydraulic pressure at each position of the sliding surface 12b when the piston 13 is located at the bottom dead center (see FIG. 5A). to be. In FIG. 5B, the vertical axis represents the surface temperature T of the sliding surface 12b, and the horizontal axis represents the distance d from the front end face of the cylinder block 12. In FIG. The vertical axis represents the hydraulic pressure P acting on the sliding surface 12b, and the horizontal axis represents the distance d from the front end face of the cylinder block 12. As can be seen in FIG. 5B, the surface temperature of the sliding surface 12b is rearward of the rear end surface of the piston 13 (ie, between the distance d1 and the distance d2). Since it is cooled by the hydraulic oil of this oil chamber 20a, it is maintained at substantially constant temperature. On the other hand, in the rear end surface of the piston 13, the opening side of the cylinder 20 (that is, between the distance 0 and the distance d1) has a small cooling effect due to the hydraulic oil that has entered the clearance, so that it moves toward the opening side. As a result, the surface temperature rises, which is the highest near the opening, i.e., at the front end face of the cylinder block 12.

In addition, as can be seen from FIG. 5C, the oil pressure acting on the sliding surface 12b includes the oil chamber 20a having a rear side of the rear end surface of the piston 13 of the sliding surface 12b. ), The hydraulic pressure acting on the area becomes a pressure approximately equal to the pressure of the hydraulic oil suctioned from the suction port 16a. On the other hand, the pressure acting on the region that is forward of the rear end surface of the piston 13 of the sliding surface 12b decreases as it moves toward the opening side because the front side of the clearance is connected in the casing 17. The pressure in the casing 17, that is, the drain pressure, is lowered.

In this manner, the surface temperature of the sliding surface 12b and the hydraulic pressure acting thereon change with the rear end surface of the piston 13 located at the bottom dead center as a boundary. In addition, high pressure acts on the sliding surface 12b over the widest range when the piston 13 is located at the bottom dead center. As in the present embodiment, the front end of the cooling groove 31 is positioned on the front end surface side of the cylinder block 12 rather than the rear end surface of the piston 13, so that the hydraulic pressure acting on the sliding surface 12b is increased. The cooling performance of the area | region which surface temperature becomes high can be improved, making rigidity high. Accordingly, it is possible to prevent damage due to the pressing of the cylinder 12 and the piston 13 without lowering the use limit pressure of the hydraulic oil.

The cooling groove 31 extending as described above is curved to protrude radially inward when viewed from the front as shown in FIG. 2, and the area between the sliding surface 12b and the outer peripheral surface 12a of the partition wall 32 is reduced in thickness. . As such, the partition wall 32 is reduced in thickness to reduce the thickness t between the sliding surface 12b and the outer circumferential surface 12a so that the heat generated from the sliding surface 12b is soaked in the low temperature working oil 12a. It can be quickly transmitted to the heat dissipation to the low temperature working oil, it is possible to suppress the temperature rise of the sliding surface (12b). Thereby, even if the cylinder block 12 is speeded up, the hydraulic oil (lubricating oil) interposed in the clearance between the sliding surface 12b and the piston 13 becomes high temperature, and can prevent it from exceeding the transition temperature, and lubricates the said hydraulic oil. Pressing of the sliding surface 12b due to deterioration of performance can be prevented. In addition, since the clearance between the sliding surface 12b and the piston 13 can be increased or the surface temperature of the sliding surface 12b can be reduced without machining oil grooves on the sliding surface 12b, the motor can be improved while improving cooling performance. There is no case to degrade the performance.

Below, the shape of the cooling groove 31 is further demonstrated. The cooling groove 31 is formed such that the minimum thickness tmin between the sliding surface 12b and the outer circumferential surface 12a is 0.02D ≦ tmin ≦ 0.3D with respect to the inner diameter D of the cylinder 20. . More specifically, the thickness t between the radially outer region 12c (corresponding to the region on the outer peripheral surface 12a side of the sliding surface 12b) and the outer peripheral surface 12a of the sliding surface 12b is The inner diameter D of the cylinder 20 is formed such that 0.02D ≦ t ≦ 0.3D. The radially outer region 12c is an intersection A1 of the radially outer side and a region extending from both sides in the circumferential direction from two points where the straight line L2 and the sliding surface 12b intersect. Here, when the cylinder block 12 rotates at a high speed, the piston 13 pressed by the centrifugal force is in contact with each other, and the piston 13 slides on the sliding surface 12b in a state in which the piston 13 is in contact with the large centrifugal force. Occurs. The said area | region 12c is an area | region of the center angle (alpha) range on both sides of a circumferential direction centering on the intersection A1, for example, and center angle (alpha) is 30 <= (alpha) <= 180 degree. In addition, the position where the piston 13 is in contact with the center angle α due to the external speed such as the rotational speed and the rotation direction or vibration of the cylinder block 12 may be considered to be wider than the center angle α. The peripheral thickness t of the sliding surface 12b may be formed so as to satisfy 0.02D ≦ t ≦ 0.3D (for example, see FIG. 6 to be described later).

Thus, by making thickness t into 0.3D or less, the cooling performance in the sliding surface 12b, especially the opening side area | region can be improved, and the raise of the surface temperature of the said sliding surface 12b can be suppressed. Thereby, the temperature rise of the hydraulic oil (lubricating oil) which flows through the clearance between the sliding surface 12b and the piston 13 can be suppressed, and it can prevent that the hydraulic oil becomes high temperature and exceeds transition temperature. Therefore, it is possible to prevent the seizure of the sliding surface 12b due to the deterioration of the lubricating performance of the hydraulic oil.

In addition, the surface temperature of the sliding surface 12b can be reduced without increasing the clearance between the sliding surface 12b and the piston 13 or without machining oil grooves on the sliding surface 12b, thereby improving cooling performance. There is no loss of motor performance. Furthermore, by setting the thickness t to 0.02D or more, the rigidity of the vicinity of the opening side of the region 12c on the radially outer circumferential side of the sliding surface 12b can be ensured, and the piston 13 reciprocates at high speed during operation. It is also possible to prevent the case in which the vicinity of the opening side is damaged.

&Lt; Other Embodiments >

In the present embodiment, the bottom surface of the cooling groove 31 is curved in an arch shape, but it is not necessarily arcuate. For example, as shown in FIG. 6, the cooling groove 31A of the cooling structure 30A is formed in a linear shape along the sliding surface 12b, and the radial direction of the sliding surface 12b is shown. The thickness t of the entire outer semicircle may be made uniform. In addition, it is not necessary to bend the shape of the cooling groove 31, and the bottom may be flat, and unevenness may be made like a fin. Furthermore, although the vicinity of the tip of the bottom of the cooling groove 31 is curved to be located radially outward as it goes to the tip, it is not necessary to be curved but may be flat to the tip (for example, the two-dot chain of FIG. 3). Sign of line (41)). In addition, in the present embodiment, as shown in Fig. 3, the front end of the cooling groove 31 is located between the front end face of the cylinder block 12 and the rear end face of the piston 13 located at the bottom dead center. You may extend to the vicinity of the said back cross section.

In the present embodiment, the case where the swash plate type hydraulic device 1 is a hydraulic motor has been described, but as described above, the hydraulic pump may be used. In this case, the cylinder block 12 is rotated by rotating the rotating shaft 11 by an electric motor, an engine, or the like. As the cylinder block 12 rotates, the piston 13 reciprocates and slides. In the hydraulic pump, the discharge port 16b is connected to the high pressure side passage 27, the suction port 16a is connected to the low pressure side passage 28, and is sucked in until it moves from the top dead center to the bottom dead center. The hydraulic oil is sucked into the oil chamber 20a through the port 16a, and the hydraulic oil sucked in between the bottom dead center and the top dead center is compressed to be discharged to the high pressure side passage 27 through the discharge port 16b. consist of.

Thus, even in the case of the hydraulic pump, the piston reciprocally slides the cylinder 20 and slides on the sliding surface 12b. For this reason, heat is generated at the sliding surface 12b as in the case of the hydraulic motor 1. Therefore, even when the swash plate type hydraulic device 1 is used as a hydraulic pump, if there is a cooling structure 30 of the cylinder block 12, the same effect as that of the hydraulic motor 1 can be obtained.

Furthermore, although the swash plate type hydraulic device 1 has been described in the present embodiment, the cooling structure 30 of the cylinder block 12 may be applied to the bent axis hydraulic device. However, in the case of the bent axis hydraulic device, even if the speed is increased, the surface temperature of the sliding surface 12b does not rise as in the swash plate type hydraulic device 1, so the effect that can be obtained is higher in the case of the swash plate type hydraulic device. Moreover, although oil is used as a working liquid, you may use other liquid, such as water, as a working liquid.

1: hydraulic motor
12: cylinder block
12a: outer surface
12b: sliding surface
12c: area
13: piston
17: casing
20: cylinder
27: high pressure side passage
28: low pressure side passage
29: communication path
30: cooling structure
31: cooling groove
32:

Claims (5)

A cylinder block having a plurality of cylinders having openings in an end surface of the piston insertion side is formed, and when rotated, the pistons respectively inserted into the cylinders reciprocate and slide.
It has a plurality of cooling grooves formed on the outer peripheral surface of the cylinder block,
The cooling groove extends from the end surface of the piston insertion side in a partition between two adjacent cylinders, and further thickens the partition so as to reduce the thickness between the sliding surface on which the piston slides and the outer peripheral surface of the cylinder block. Formed by reduction,
The piston reciprocally slides the inside of the cylinder between the top dead center of the cylinder and the bottom dead center.
The cooling groove is formed so as to extend in parallel with the cylinder from the end face of the piston insertion side and to be located at the end face of the piston insertion side rather than near the end face in the cylinder of the piston located at the bottom dead center. Cooling structure of the cylinder block. A cylinder block having a plurality of cylinders having openings in an end surface of the piston insertion side is formed, and when rotated, the pistons respectively inserted into the cylinders reciprocate and slide.
It has a plurality of cooling grooves formed on the outer peripheral surface of the cylinder block,
The cooling groove extends from the end surface of the piston insertion side in a partition between two adjacent cylinders, and further thickens the partition so as to reduce the thickness between the sliding surface on which the piston slides and the outer peripheral surface of the cylinder block. Formed by reduction,
The cooling groove is formed such that the minimum thickness tmin between the outer peripheral surface of the cylinder block and the sliding surface is 0.02D ≦ tmin ≦ 0.3D with respect to the inner diameter D of the cylinder. Cooling structure. A cylinder block is connected to a low pressure side passage through which a low pressure hydraulic fluid flows and a high pressure side passage through which a high pressure hydraulic fluid flows, and the hydraulic fluid is supplied from the high pressure side passage to the cylinder and discharged from the cylinder to the low pressure side passage. A swash plate type hydraulic device which sucks the working liquid from the low pressure side passage to the cylinder by rotating the cylinder block or rotates the cylinder block, further compresses the liquid, and discharges the hydraulic fluid to the high pressure side passage.
The swash plate type hydraulic device which has a cooling structure of the said cylinder block of Claim 1 or 2. 4. A casing according to claim 3, having a casing for receiving said cylinder block,
The inside of the casing is connected to the low pressure side passage through a communication path, and the low pressure hydraulic oil of the low pressure side passage is guided inside the casing. delete

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