Patent Application
20080232994
The present invention relates to an inner rotor of an internal gear pump which meshes with an outer rotor, and more specifically, relates to an inner rotor of an internal gear pump in which a mounting hole that allows a driving shaft to be inserted thereinto is formed in an axis, the mounting hole has a cross-sectional shape substantially corresponding to the driving shaft, and torque is transmitted by the driving shaft inserted into the mounting hole.
As a general internal gear pump that is known widely, there is a trochoidal pump utilizing a trochoidal tooth profile for an inner rotor and an outer rotor. In the trochoidal pump, as the inner rotor is rotationally driven, the outer rotor which meshes with the inner rotor is rotated in the same direction as the inner rotor. This rotation increases and decreases the volume of a pump chamber formed between contact parts of the rotors, thereby suctioning a fluid from a suction port and discharging the fluid from a discharge port. Since this trochoidal pump has advantages, such as good efficiency and ease of fabrication, it has come into wide use.
The internal gear pump as described above is used as an oil pump of a prime mover, and the inner rotor is rotationally driven by using a crankshaft of the prime mover as the driving shaft (for example, Japanese Unexamined Patent Application, First Publication No. H11-343985 (FIG. 8, Paragraph 0019)).
An example of the internal gear pump will now be described with reference to
Also, in the internal gear pump 1 in which the inner rotor 4 is rotated by the crankshaft 6 of an engine, in order for the crankshaft 6 to be inserted into and connected to the mounting hole 5 of the inner rotor 4 after the outer rotor 3 and the inner rotor 4 are assembled into the casing 2, a clearance that enables insertion is provided between the mounting hole 5 and the crankshaft 6 so that centering of the central axis of the inner rotor 4 can be obtained by engagement with the casing 2.
As the above engaging structure, for example, an axially projecting tubular part is provided at a side face of an inner rotor, a supporting hole which supports the tubular part is provided in a casing (for example, Japanese Unexamined Patent Application, First Publication No. S63-223382 (first line from the bottom in the lower right column of Page 2 to first line in the upper left column of Page 3, and FIGS. 5, 6, and 8)), and the supporting hole defines the center of rotation of the inner rotor. In this case, the clearance between the tubular part and the supporting hole is set smaller than the clearance between the mounting hole and the crankshaft.
In the structure in which a predetermined clearance is provided between the mounting hole and the crankshaft as described above, in order to positively transmit rotation of the crankshaft to the mounting hole, a pair of flat surfaces are formed at the outer periphery of the crankshaft (for example, Japanese Unexamined Patent Application, First Publication No. H11-343985 (FIG. 8, Paragraph 0019)), Japanese Unexamined Patent Application, First Publication No. S63-223382 (first line from the bottom in the lower right column of Page 2 to first line in the upper left column of Page 3, and FIGS. 5, 6, and 8).
When the above engaging structure between the crankshaft and a mounting hole is shown in
Moreover, since the corners 6B that are edges of the crankshaft 6 strike against the mounting hole 5, there is a problem in that the mounting hole 5 is worn out in the portion against which the corner 6B hits. Furthermore, if hard foreign objects enter the clearance between the mounting hole 5 and the crankshaft 6, the mounting hole 5 is damaged easily.
It is an object of the present invention to provide an inner rotor of an internal gear pump capable of relaxing any local stress concentration caused by a rotational moment transmitted from a driving shaft.
The present invention is an inner rotor of an internal gear pump in which a mounting hole that allows a driving shaft to be inserted thereinto is formed in an axis, the mounting hole has a cross-sectional shape substantially corresponding to the driving shaft, and torque is transmitted by the driving shaft. Here, the driving shaft and the mounting hole have a cross-sectional shape including two main circular arc parts on the same circle and two connecting parts which connect both adjacent ends of the main circular arc parts, and the connecting parts of the mounting hole are recessed at their ends.
According to the configuration of the present invention, the connecting parts of the mounting hole are recessed at their ends. Therefore, corners of the crankshaft do not hit against corners of the mounting hole. As a result, any stress concentration caused by the transmission of rotation between the corners can be relieved.
Moreover, in the present invention, the connecting parts of the mounting hole may be formed in the shape of a large circular arc which projects inward.
According to the configuration, the torque of the driving shaft is transmitted to the mounting hole in a state where the connecting parts of the driving shaft and the connecting parts of the mounting hole which are formed in the shape of a large circular arc come into line contact with each other. Therefore, the value of any local stress generated in the mounting hole can be reduced. Moreover, since any local stress concentration can be suppressed in this way, generation of abnormal noises, etc. can be prevented.
Moreover, in the present invention, convex small circular arc parts having a small radius may be provided at both ends of each of the connecting parts of the mounting hole.
According to the configuration of, the torque of the driving shaft is transmitted to the mounting hole in a state where the connecting parts of the driving shaft and one of the convex small circular arc parts of the mounting hole come into line contact with each other or in a state where the connecting parts of the driving shaft and the connecting parts of the mounting hole come into surface contact with each other. Therefore, any local stress generated in the mounting hole can be reduced.
Moreover, in the present invention, the connecting parts of the driving shaft may be located outside inner ends of the convex small circular arc parts.
According to the configuration, the torque of the driving shaft is transmitted to the mounting hole in a state where the connecting parts of the driving shaft and at least one of the convex small circular arc parts of the connecting parts of the mounting hole come into line contact with each other. Therefore, any local stress generated in the mounting hole can be reduced.
Moreover, in the present invention, recesses that are recessed may be provided at corners of the mounting hole so as to correspond to corners of the driving shaft in places where the main circular arc parts and the connecting parts are connected.
According to the configuration, the corners of the driving shaft do not hit against the corners of the mounting hole by providing the recesses.
Moreover, in the present invention, the recesses may be circular arc cutouts having a small radius.
According to the configuration, any stress generated in the vicinity of the corners of the mounting hole can be reduced.
Moreover, in the present invention, the recesses are formed by recessing ends of each of the main circular arc parts of the mounting hole.
According to the configuration, any stress generated in the vicinity of the corners of the mounting hole can be reduced.
Moreover, in the present invention, the inner rotor is a ferrous sintered member.
According to the configuration, since the inner rotor is a ferrous sintered member, shaping of the mounting hole is easy.
Moreover, in the present invention, the sintered member may be an Fe—Cu—C-based sintered member having a density of 6.6 to 7.0 cm3.
According to the configuration, parts having a lower density than a conventional article can be used, and product cost can be reduced.
Moreover, in the present invention, the driving shaft may be connected to a crankshaft of a prime mover.
According to the configuration, even under the vibrating conditions of the prime mover, generation of abnormal noises can be prevented. As a result, an inner rotor having excellent durability can be obtained.
According to the present invention, the driving shaft and the mounting hole have a cross-sectional shape including two main circular arc parts on the same circle and two connecting parts which connect both adjacent ends of the main circular arc parts, and the connecting parts of the mounting hole are recessed at their ends. Thus, any local stress concentration caused by the rotational moment transmitted from the driving shaft can be relaxed.
Moreover, according to the present invention, the connecting parts of the mounting hole are formed in the shape of a large circular arc which projects inward. Thus, any local stress concentration caused by the rotational moment transmitted from the driving shaft can be relaxed.
Moreover, according to the present invention, convex small circular arc parts having a small radius are at both ends of each of the connecting parts of the mounting hole. Thus, any local stress concentration caused by the rotational moment transmitted from the driving shaft can be relaxed.
Moreover, according to the present invention, the connecting parts are located outside inner ends of the convex small circular arc parts. Thus, any local stress generated in the mounting hole can be reduced.
Moreover, according to the present invention, recesses that are recessed are provided at corners so as to correspond to corners of the driving shaft in places where the main circular arc parts and the connecting parts are connected. Thus, the corners of the driving shaft do not hit against the corners of the mounting hole.
Moreover, according to the present invention, the recesses are circular arc cutouts having a small radius. Thus, any stress generated in the vicinity of the corners of the mounting hole can be reduced.
Moreover, according to the present invention, the recesses are formed by recessing ends of each of the main circular arc parts of the mounting hole. Thus, any stress generated in the vicinity of the corners of the mounting hole can be reduced.
Moreover, according to the present invention, the inner rotor is a ferrous sintered member. Thus, shaping of the mounting hole is easy.
Moreover, according to the present invention, the sintered member is an Fe—Cu—C-based sintered member having a density of 6.6 to 7.0 cm3. Thus, parts having a lower density than a conventional article can be used, and product cost can be reduced.
Moreover, according to the present invention, the driving shaft is connected to a crankshaft of a prime mover. Thus, even under the vibrating conditions of the prime mover, generation of abnormal noises is prevented, and an inner rotor having excellent durability is obtained.
Hereinafter, embodiments of an inner rotor of an internal gear pump of the present invention will be described with reference to the accompanying drawings. In addition, the parts described with reference to
The mounting hole 5 formed in the inner rotor 4 has two main circular arc parts 21 located on the same circle around an axis 5S thereof, and linear connecting parts 22 which connect ends of the main circular arc parts 21 adjacent to each other in the circumferential direction. The mounting hole 5 has a cross-sectional shape in which the connecting parts 22 which face each other with the axis 5S as the centers thereof are parallel with each other and which is symmetrical in four directions. An intersection of the main circular arc part 21 and the connecting part 22 is a corner 23. Moreover, the symbol K in the drawing denotes a basic circle of the mounting hole 5, and the main circular arc part 21 is located on this basic circle K.
As shown in the explanatory view of
Moreover, the connecting part 22 of the mounting hole 5 is formed in the shape of a large circular arc which projects inward. This connecting part 22 projects to the greatest at a middle part thereof, and is recessed at ends thereof. The dimension between the middle part and the linear connecting part 12 of the crankshaft 6 is set to a dimension of the clearance Y The corners 23 are formed at both ends of the connecting part 22 of the mounting hole 5. The projection height H of the connecting part 22 is 0.05 to 0.25 mm. In addition, this projection height H is the difference in height between the middle part of the connecting part 22 and the corners 23 at both ends of the connecting part. Moreover, the radius RI of the connecting part 22 is determined depending on the dimension of each part of the mounting hole 5, and the projection height H. In this case, if the projection height H is less than 0.05 mm, the curvature of the radius R becomes excessively large, and thus the effect of reducing a stress generated in contact with the crankshaft 6 is not obtained sufficiently. Moreover, if the projection height H exceeds 0.25 mm, this results in a large deviation of a part contacting the crankshaft 6 in the central axis direction. That is, the clearance between the contact part and the axis 6S becomes narrow, and the stress generated with respect to the same transmission torque tends to rise strongly. This should be avoided.
In addition, although the connecting part 22 is shown in a straight line in
Moreover, the inner rotor 4 is a Fe—Cu—C-based sintered member containing Fe as its main component, and is obtained by compacting raw powder to form a green compact, and sintering the green compact. In this embodiment, the crankshaft 6 is used for a prime mover, such as an engine, and the internal gear pump 1 is an internal gear-type oil pump of the prime mover. In order to satisfy this use condition, the density of the inner rotor 4 is set to 6.6 to 7.0 cm3 (6.6 cm3 or more and 7.0 cm3 or less). Moreover, the tensile strength of the inner rotor 4 is about 35 to 40 kg/mm2.
Next, the operation will now be described on the basis of the above configuration. First, since the clearance Y is provided between the middle parts of the linear connecting part 12 and the connecting part 22, when the prime mover is driven to rotate the crankshaft 6, the corner 13 of the main circular arc part 11 of the crankshaft 6 on the forward in the direction of rotation thereof abuts the connecting part 22, which forms a large circular arc shape, of the mounting hole 5 whereby torque is transmitted to the inner rotor 4.
Accordingly, at the time of rotation of the crankshaft, the linear connecting part 12 of the crankshaft 6 that is a flat surface and the circular arc connecting part 22 of the mounting hole 5 that is a curved surface come into line contact with each other whereby torque is transmitted to the mounting hole 5 from the crankshaft 6. Therefore, compared with a case where torque is transmitted by contact between corners, any local stress concentration in the mounting hole 5 can be prevented.
As described above, in the present embodiment, the inner rotor 4 of an internal gear pump is provided in which the mounting hole 5 which allows the crankshaft 6 as a driving shaft to be inserted therethrough is formed, the mounting hole 5 has a cross-sectional shape substantially corresponding to the crankshaft 6, and torque is transmitted by the crankshaft 6 inserted into the mounting hole 5. The crankshaft 6 and the mounting hole 5 have the two main circular arc parts 11 and 21 on the same circle, and the two connecting parts 12 and 22 which connect the adjacent ends of the main circular arc parts 11 and 21. The connecting parts 12 and 22 which face each other have a substantially parallel cross-sectional shape. The ends of each connecting part 22 of the mounting hole 5 are recessed. Therefore, the corner 13 of the crankshaft 6 does not hit against the corner 23 of the mounting hole 5. As a result, any stress concentration caused by the transmission of rotation between corners can be relieved.
Moreover, as described above, in the present embodiment, the connecting part 22 of the mounting hole 5 is formed in the shape of a large circular arc which projects inward. Therefore, the torque of the crankshaft 6 is transmitted to the mounting hole 5 in a state where the connecting part 12 of the crankshaft 6 and the connecting part 22 of the mounting hole 5 which forms a large circular arc shape come into line contact with each other. Therefore, the value of any local stress generated in the mounting hole 5 can be reduced.
Moreover, as described above, in the present embodiment, the inner rotor 4 is a ferrous sintered member. Therefore, shaping of the mounting hole 5 is easy.
Moreover, as described above, in the present embodiment, the sintered member is an Fe—Cu—C-based sintered member having a density of 6.6 to 7.0 cm3. Therefore, parts having a lower density than a conventional article can be used, and product cost can be reduced.
Moreover, as described above, in the present embodiment, the driving shaft is connected to the crankshaft 6 of the prime mover. Therefore, even under the vibrating conditions of the prime mover, generation of abnormal noises is prevented and an inner rotor having excellent durability is obtained.
As shown in
Accordingly, the corner 13 of the crankshaft 6 is prevented from hitting against the mounting hole 5 by providing the circular arc cutout 24 in the corner 23 that is an intersection part of the main circular arc part 21 and the large circular arc connecting part 22.
As described above, in the present embodiment, the circular arc cutout 24 having a small radius, which is a recess that is recessed, is provided at the corner 23 of the mounting hole 5 so as to correspond to corner 13 of the driving shaft as a connecting part between the main circular arc part 11 and the connecting part 12. Therefore, the corner 13 of the crankshaft 6 does not hit against the corner 23 of the mounting hole 5, and consequently, any stress generated in the vicinity of the corner 23 of the mounting hole 5 can be reduced.
Moreover, as described above, in the present embodiment, the recess is composed of the circular arc cutout 24 having a small radius. Therefore, any stress generated in the vicinity of the corner of the mounting hole 5 can be reduced.
Accordingly, the corner 13 of the crankshaft 6 is prevented from hitting against the mounting hole 5 by providing the escape recess 25 in the corner that is an intersection part of the main circular arc part 21 and the linear connecting part 22.
As described above, in the present embodiment, the connecting part 22 is formed in the shape of a large circular arc which projects inward, and the escape recess 25 as a recess is provided. Therefore, the same operation and effects as the above respective embodiments are exhibited.
Moreover, as described above, in the present embodiment, the recess is formed by recessing the end 21T of the main circular arc part 21 of the mounting hole 5. Therefore, any stress generated in the vicinity of a corner of the mounting hole 5 can be reduced.
Accordingly, at the time of rotation of the crankshaft, the linear connecting part 12 of the crankshaft 6 that is a flat surface and the convex small circular arc part 31 of the mounting hole 5 that is a curved surface come into line contact with each other, or the linear connecting part 12 and the connecting part 22S come into surface contact with each other, whereby torque is transmitted to the mounting hole 5 from the crankshaft 6. Therefore, compared with a case where torque is transmitted by contact between corners, any local stress concentration in the mounting hole 5 can be prevented.
As described above, in the present embodiment, the crankshaft 6 has the two main circular arc parts 11 on the same circle and the two connecting parts 12 which connect adjacent ends of the main circular arc parts 11. The crankshaft 6 has a cross-sectional shape in which the connecting parts 12 which face each other are substantially parallel. The convex small circular arc parts 31 having a small radius are provided at both ends of the linear connecting part 22S of the mounting hole 5. Thus, the torque of the crankshaft 6 is transmitted to the mounting hole 5 in a state in which the connecting part 12 of the crankshaft 6 and one of the convex small circular arc parts 31 of the connecting part 22S of the mounting hole 5 come into line contact with each other or in a state in which the connecting part 12 of the crankshaft 6 and the connecting part 22S of the mounting hole 5 come into surface contact with each other. Therefore, the value of any local stress value generated in the mounting hole 5 can be reduced.
As described above, in the present embodiment, the convex small circular arc parts 31 having a small radius are provided at both ends of each of the connecting parts 22S of the mounting hole 5, and the circular arc cutout 24 as a recess is provided. Thus, the same operation and effects as the above respective embodiments are exhibited.
As described above, in the present embodiment, the convex small circular arc parts 31 having a small radius are provided at both ends of each of the connecting parts 22S of the mounting hole 5, and the escape recess 25 as a recess is provided. Thus, the same operation and effects as the above respective embodiments are exhibited.
Accordingly, at the time of rotation of the crankshaft, the linear connecting part 12 of the crankshaft 6 that is a flat surface and the convex small circular arc part 31 of the mounting hole 5 that is a curved surface come into line contact with each other, or the linear connecting part 12 and the inner ends 31A of the convex small circular arc parts 31 come into line contact with each other, whereby torque is transmitted to the mounting hole 5 from the crankshaft 6. Therefore, compared with a case where torque is transmitted by contact between corners, any local stress concentration in the mounting hole 5 can be prevented.
As described above, in the present embodiment, the convex small circular arc parts 31 having a small radius are provided at both ends of each of the connecting parts 22S of the mounting hole 5. Therefore, the torque of the crankshaft 6 is transmitted to the mounting hole 5 in a state where the connecting part 12 of the crankshaft 6 and any one or both of the convex small circular arc parts 31 of the connecting part 22S of the mounting hole 5 come into line contact with each other. Therefore, the value of any local stress generated in the mounting hole 5 can be reduced.
Moreover, as described above, in the present embodiment, the connecting part 22S is located outside the inner end 31A of the convex small circular arc part 31. Thus, the torque of the crankshaft is transmitted to the mounting hole in a state where the connecting part 12 of the crankshaft 6 hits against one of the convex small circular arc parts 31 or the inner ends 31A thereof. Therefore, the value of any local stress generated in the mounting hole 5 can be reduced.
As described above, in the present embodiment, the convex small circular arc parts 31 having a small radius are provided at both ends of each of the connecting parts 22S of the mounting hole 5, and the circular arc cutout 24 as a recess is provided. Thus, the same operation and effects as the above respective embodiments are exhibited.
As described above, in the present embodiment, the convex small circular arc parts 31 having a small radius are provided at both ends of each of the connecting parts 22S of the mounting hole 5, and the escape recess 25 as a recess is provided. Thus, the same operation and effects as the above respective embodiments are exhibited.
In addition, the present invention is not limited to the above embodiments, and various modifications thereof can be made.
This is a U.S. national phase application under 35 U.S.C. §371 of International Patent Application No. PCT/JP2005/000233, filed Jan. 12, 2005. The International Application was published in Japanese on Jul. 20, 2006 as International Publication No. WO 2006/075363 under PCT Article 21(2) the content of both are incorporated herein in their entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2005/000233 | 1/12/2005 | WO | 00 | 6/14/2007 |
