JP2002364733A - Spur gear power transmission mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rotationally make a spur gear power transmission mechanism compact by improving contact pressure of meshing gears by combination of concave and convex teeth. SOLUTION: The crowning (a convex arc face 4a') is applied to the tooth trace of the tooth 4a in one gear 4 of the meshing spur gears 3, 4 supported by at least two parallel support shafts, while the reverse crowning (a concave arc face 3a') having a curvature radius larger than that of the other gear 3 is machined in the tooth trace of the tooth 3a of the gear 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spur gear power transmission mechanism for reducing the surface pressure at the time of engagement to improve the power transmission function.

[0002]

2. Description of the Related Art Generally, in a power transmission mechanism using a spur gear, at least two shafts are provided in parallel with each other, and gears supported by these support shafts mesh with each other to transmit power. From such a thing,
It is required that the degree of parallelism of the gear with respect to the support shaft be high.

However, in a mechanical device having a structure for driving a gear, a bearing portion for supporting the gear supporting shaft is formed. It must be performed precisely, and it is difficult to finish the parallelism to a high degree by a general processing method. For this reason, the meshing accuracy of the gears is not theoretically possible, and if an error occurs in the bearing portion due to a deviation during assembly or the like, the meshing of the gears is biased. In this case, the meshing portions of the gears are in contact with each other, so that the surface pressure acting on the teeth is not as expected, and when a required driving force is transmitted, an overload occurs and the tooth surfaces are worn. To avoid problems caused by machining errors and center runout at the time of assembling that occur on such a work, the inconvenience at the time of meshing that tends to occur is solved, and the gear teeth are used for the purpose of securing the power transmission force. A measure has been taken in which a crowning process is performed to absorb the so-called runout and reduce the surface pressure so that power can be transmitted by smooth meshing.

A specification disclosed by Japanese Utility Model Laid-Open Publication No. 3-60639 discloses a gear transmission between two orthogonal shafts, such as a helical gear, in which one of the gears is subjected to reverse crowning. It is described that the durability and reliability can be improved by reducing the contact pressure of the tooth surface by using the same.

[0005] In general, when a tooth of a gear is subjected to crowning, the tooth of the other gear is set to be slightly thicker at the center of the tooth width than the normal tooth thickness. It is processed into a bulged shape.
By doing so, the contact between the teeth at the meshing portion can be changed from the point contact to the surface contact, so that the surface pressure of the tooth at the meshing portion can be reduced. By the way, if the amount of tooth trace correction by this crowning is large, the area of contact with the teeth is reduced, and the effect of reducing the surface pressure is reduced. Even if this crowning is performed, heat treatment (quenching) must be performed to increase the surface hardness in order to increase the strength of the tooth surface.

[0006]

However, when a process for increasing the tooth surface strength by quenching is performed, there is a problem that thermal strain is inevitably generated, and the effect of correcting tooth traces is reduced. Therefore, when the crowning process and the tooth-hardening process after quenching are used in combination, there is a problem in that the machining cost increases and the product cost increases.

Conventionally, in a power transmission mechanism using a spur gear, when tooth surface strength is required, for example, a cross shaft such as a helical gear or a torsion gear, or a non-cross shaft such as a hypoid gear is used. Since it is a simple meshing state compared to gear meshing, workability can be improved by adjusting the tooth trace by increasing the surface strength by quenching or increasing the pressure angle to cope with gear load Many measures have been adopted to make the process easier, and tooth shape modification, which has the problem of increasing production costs, is not relatively adopted.The surface strength is increased by quenching, and the tooth It is often dealt with by preparing. For this reason, if gear strength is increased to improve durability and reliability, a corresponding tooth profile is required, and the overall size of the gear transmission device cannot be avoided. There is a point.

SUMMARY OF THE INVENTION The present invention has been made in order to solve such a problem. In a spur gear power transmission mechanism, the contact pressure between the two gears is determined by a combination of concave and convex gear teeth. It is an object of the present invention to provide a spur gear power transmission mechanism that can be reasonably downsized by increasing the power ratio.

[0009]

In order to achieve the above-described object, a spur gear power transmission mechanism according to the present invention comprises a spur gear supported by at least two parallel support shafts and meshing with each other. The teeth of one of the gears are crowned on the tooth traces, and the teeth of the other gear are reverse-crowned on the tooth traces with a larger radius of curvature than that of the gear. It is.

According to the present invention, since the spur gear meshing in the two-axis parallel state meshes with the concave and convex in the meshing state, the meshing shift due to a dimensional error or a load during processing or assembly. Does occur, the contact surface is widened and the surface pressure can be reduced, and the driving force can be transmitted over a wide range of the tooth width. Therefore, if the tooth width is the same, the surface pressure is reduced. In other words, the tooth surface strength is increased, and it is possible to reduce the tooth profile size and make the whole compact. As a result, the weight of the gear transmission mechanism can be reduced, the selection range of gear components can be widened, and expensive lubricating oils can be omitted, and the economic efficiency associated therewith can be significantly improved. Further, since the tooth surface strength is increased, the effect of improving the durability can be obtained.

As the meshing structure of the gears, it is preferable that the planetary gear mechanism is constituted by using a sun gear having a tooth trace reversely crowned and a planetary gear meshing with the sun gear being crowned. In this way, it is possible to make the gear transmission mechanism, which requires advanced technology to increase the meshing accuracy in the work, reasonably high in gear strength, to reduce the tooth profile dimensions within the allowable range and to make it compact. It is possible to obtain an effect that the surrounding structure can be reduced in size and the weight of the device can be reduced. In the planetary gear mechanism, at the portion where the planetary gear meshes with the teeth of the outer internal gear, the outer teeth of the planetary gear are held at the valleys of the teeth of the internal gear. The power transmission function is not impaired because the contact surface of the tooth muscles is wider than in the state where the gears are in mesh with each other and the phenomenon of one-side contact is reduced.

In the present invention, the crowning device
Inverse crowning may be a single arc or a multi-arc envelope. With this configuration, the tooth trace can be selectively corrected depending on the tooth width and the support structure of the gear, and preferable conditions for the contact state at the meshing portion can be set.

[0013]

Next, a specific embodiment of a spur gear power transmission mechanism according to the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing a pair of gears as an embodiment of a power transmission mechanism of a gear according to the present invention, and FIG. 2 is a diagram schematically showing the shape of teeth of both gears meshing with each other. Have been.

In this embodiment, spur gears 3 and 4 respectively supported and fixed on two support shafts 1 and 2 provided in parallel are meshed with each other to move from one support shaft 1 to the other support shaft 2. It has a structure to transmit torque. These two gears 3 and 4 are formed in an involute tooth profile with a normal pressure angle, and the tooth 3a of one of the gears 3 has a central portion having a tooth width larger than the normal tooth thickness along the tooth trace along the tooth trace. However, reverse crowning is performed so as to be thin, for example, about 0.05 mm. On the other hand, the teeth 4a of the other gear 4 are crowned in a convex shape along the tooth trace so as to be thicker at the center of the tooth width than the normal tooth thickness. The correction of the tooth thickness by the crowning process is performed so as to have a dimension of about 0.05 mm or slightly larger than usual.

When the two gears 3 and 4 configured as described above are arranged at a predetermined interval and engaged with each other, the teeth 3a of one of the gears 3 are subjected to reverse crowning to form a concave shape along the tooth trace. While the arc surface 3a 'is formed, the teeth 4a of the other gear 4 are crowned to form a convex arc surface 4a'. The irregularities are meshed with each other, and both the crowning radius of curvature ρ1 and the inverse crowning radius of curvature ρ2
Is set so that at least ρ1 ≦ ρ2,
Even if the parallelism of the support shafts 1 and 2 of the gears 3 and 4 is deviated, the meshing portions of the teeth of the gears 3 and 4 do not contact each other as in the case of ordinary teeth, and a wide contact surface is maintained. Power is transmitted. Therefore, the contact pressure at the meshing portion between the two gears 3 and 4 is significantly reduced as compared with the conventional one.

Therefore, in a gear having the same tooth width, a reduction in the contact pressure of the teeth at the meshing portion increases the tooth profile strength, and if the design strength is kept constant, the tooth shape is reduced. It becomes possible to make it smaller.
Alternatively, the selection range of the gear forming material is widened, the power transmission mechanism can be made compact by reducing the tooth shape, and the supporting structure can be reduced accordingly, so that the weight of the entire apparatus can be reduced.

Further, if the heat treatment of the tooth portion of the gear is subjected to the surface quenching treatment, the heat distortion can be greatly reduced, the workability of the gear is enhanced, and the processing cost is reduced as compared with the general gear manufacturing. On the other hand, the benefits of improved performance due to the improved power transmission performance or the compactness of the power transmission mechanism can reduce the size and weight of the device-side structure incorporating this power transmission mechanism, thereby exceeding the processing cost. , It is possible to provide a better device.

In the power transmission mechanism of a pair of spur gears, if the support shaft has a cantilever structure, deflection due to a machining error at the support shaft mounting portion or a change in a load applied during driving. Therefore, the occurrence of the one-sided contact phenomenon is likely to occur, so the design on the safe side is to reduce the contact pressure at the meshing part of both gears by combining the gears with the tooth traces corrected as described above. This has the advantage that the design conditions can be relaxed and streamlined. In addition, depending on the gear support structure and driving conditions, when performing the above-mentioned crowning (reverse crowning) processing as a tooth trace correction on the tooth portion, the radius of curvature is made a uniform single arc, and an envelope of a plurality of arcs is drawn. Can be

Next, FIG. 3 is a sectional view of an embodiment of a planetary gear device incorporating a gear power transmission mechanism according to the present invention.

As the planetary gear device 10 of this embodiment, a sun gear 11 having reverse crowning along its tooth trace is used, and the planetary gear 1 meshing with the sun gear 11 is used.
Each of the two gears 2 is formed by using a crowned tooth trace and a ring gear 13 formed of a normal tooth. Note that the crowning and the reverse crowning are the same as those of the gear power transmission mechanism of the above embodiment. In the figure, reference numeral 15 denotes a carrier.

In the planetary gear device 10 configured as described above, the sun gear 11 located on the output shaft 14 from the driving machine is used.
On the other hand, since the planetary gear 12 which meshes with the ring gear 13 and rolls around the periphery thereof has a structure in which an error easily occurs in the degree of parallelism of the output shaft 14 on the axis of the support shaft 16 with respect to the support axis. However, it is difficult to transmit power as designed due to the occurrence of a tooth contact phenomenon. However, as described in the above-described embodiment, the driving can be effectively performed by reducing the contact pressure. In other words, by providing a concave inverted crowning on the teeth of the sun gear 11 and a convex crowning on the teeth of the planetary gear 12, a ring in which the planetary gear 12 is likely to have a problem in processing accuracy is an internal tooth. When the gear 13 and the sun gear 11 are simultaneously meshed with each other and rolled, the contact surface pressure at the meshing portion can be increased even if a core run-out occurs due to the unevenness with the sun gear 11, thereby reducing the contact surface pressure between the two. You. In the meshing portion between the planetary gear 12 and the ring gear 13, since the ring gear 13 side has the internal teeth, the teeth of the planetary gear 12 are held by the front and rear teeth at the valleys of the internal teeth of the ring gear 13. Since the tooth surface is slid and the contact surface is widened, unlike the meshing of the external teeth, if the combination is normal, the meshing ratio is high, so that the power transmission efficiency is improved.

As a result, the contact surface of the planetary gear 12 at the meshing portion with the sun gear 11 and the ring gear 13 can be made larger than that of the conventional system. Therefore, according to the gear power transmission mechanism of the present embodiment, the tooth profile strength can be increased as compared with the conventional one at the same tooth width, so that the tooth profile can be reduced, or the selection range of the gear material can be expanded. However, the planetary gear device 10 can be made compact. This planetary gear device 1
Even in the case of the gear No. 0, if the surface of the gear is subjected to a skin quenching treatment, the heat distortion can be suppressed and the effective processing can be performed.

Further, if the planetary gear device can be made compact by adopting the above-described configuration, the structure of the drive unit can be further reduced in size by incorporating it into a final reduction gear of a construction machine, for example. In addition, a remarkable effect can be exhibited in reducing the size of the vehicle and improving the fuel efficiency.

In the above description, when the teeth are crowned (reverse crowning), in addition to making the radius of curvature uniform, the curvature at both ends of the tooth trace may be changed to that at the center.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a pair of gears as an embodiment of a gear power transmission mechanism according to the present invention.

FIG. 2 is a diagram schematically showing the shapes of teeth of both gears that mesh with each other.

FIG. 3 is a cross-sectional view of an embodiment of a planetary gear device incorporating a gear power transmission mechanism according to the present invention.

[Explanation of symbols]

 1, 2 Support shaft 3, 4 Gear (spur gear) 3a One gear tooth 3a 'Concave arc surface 4a The other gear tooth 4a' Convex arc surface 10 Planetary gear device 11 Sun gear 12 Planetary gear 13 Ring gear 14 Output shaft from the drive 15 Carrier 16 Planetary gear support shaft

Claims (3)

[Claims] A tooth of one gear of a spur gear supported and meshing with at least two parallel support shafts is crowned on its tooth trace, and the tooth of the other gear is toothed on its tooth trace. A spur gear power transmission mechanism characterized in that the radius of curvature is made larger than that of the above and reverse crowned. 2. A planetary gear mechanism comprising a sun gear having a tooth trace reverse crowned as a meshing structure of the gears and a planetary gear meshing with the tooth trace having a crowned tooth trace. 2. The spur gear power transmission mechanism according to 1. 3. The crowning / back crowning according to claim 1,
The spur gear power transmission mechanism according to claim 1, wherein the power transmission mechanism is an envelope of a single arc or a plurality of arcs.