JP3068699U - Gear pump gears - Google Patents

Abstract

(57) [Problem] To form a power transmission part with an involute tooth profile excellent in power transmission and to form other parts with an arcuate tooth shape, thereby facilitating gear processing and gear pump assembly work. Further, the present invention provides a gear pump gear having excellent pump efficiency without trapping or backflow of fluid. SOLUTION: The front and rear sides of a pitch circle are formed by an involute curve 12, and the tooth tip side and the root side continuous with the front and rear sides are formed by arcuate curves 13, 13, and a portion formed by the involute curve 12 is formed. A helical gear having a pitch of 0.15 to 0.5 and a center of curvature P ′ at each point of the arc-shaped curve has an arc-shaped curve 13 with the pitch circle 11 interposed therebetween.
And the involute curve 1
2 and the tangent lines at the connection points E1 ′ to E4 ′ of the arc-shaped curve 13 are shared.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to an improved gear pump gear that is easy to manufacture and has improved pump efficiency.

[0002]

[Prior art]

 The gear pump forms a confined gap by engaging a pair of gears in the housing, and the fluid moves continuously from the inlet side to the outlet side of the housing by the rotation of the gears. It is something that is moved.

[0003] There are various types of gear pump structures. As a type commonly used in automobiles and machine tools, for example, as shown in FIG. 4, involute gears 1A and 1B are used and meshed with each other. It is mounted in a housing 4 provided with an inlet 2 and an outlet 3. This is easy to manufacture because the tooth profile of the rack 6, which is a gear cutting tool, is formed as a straight line as shown in FIG. 6, and the meshing accuracy does not change even if the mounting interval of the involute gears 1A and 1B changes. Therefore, there are advantages such as easy assembly of the gear pump.

[0005] The meshing state of the involute gears 1A and 1B will be described with reference to the case of Sugba in FIG. 5. The point that the gear 1A is a driver, the gear 1B is a follower, and the contact of the tooth end of the gear 1A is about to be terminated. This is indicated by C1. In this case, the tooth root of the gear 1A and the tooth tip of the gear 1B need to be in contact with each other at the point C2 before the completion of the contact at the point C1. In the case of an involute gear, the distance C1-C2 is called the normal pitch, and the actual length of the contact in the normal direction of the tooth profile, that is, the length twice as long as P-C1, is divided by the normal pitch C1-C2. This is called the meshing ratio. If it is not 1 or more, it will not work as a normal gear.

When the involute gears 1A and 1B for power transmission are employed in a gear pump, a backlash-free mesh as shown in FIG. There is a need. However, in the process of the rotation, in addition to the contact points C1 and C2, the contact also occurs at a point C on the rear side as viewed from the power transmission side. As a result, the fluid is confined in the gap G1 surrounded by the contact points C1 and C and the gap G2 surrounded by the contact points C2 and C. The gaps G1 and G2 increase and decrease with the rotation of the gears 1A and 1B. As a result, the pressure of the fluid fluctuates, and the performance of the gear pump is reduced.

In order to solve the problem of fluid confinement, as shown in FIG. 7, a gear having a gear tooth profile formed by a sinusoidal curve and contact at one point has been developed by Matsuki Itaya. Japanese Patent Publication No. 35-13504). Fig. 8 shows the relationship between the tooth profile developed by Matsuki Itaya (hereinafter referred to as the Itaya-type tooth profile) and the tooth profile of the rack that processes the tooth profile. D0-C-D0 'is given as the tooth profile of the rack, and the tooth profile of the processed gear 5A is D1-C-D1', the tooth profile of the gear 5B is D2-C-D2 ', and the gear 5A and the gear 5B are formed. Is a one-point contact at the point C, and a gear pump free of fluid is obtained. This Itani-type tooth profile curve is defined as shown in the following equation. x = mθ (1 + 0.3cosθ) (1) y = 1.2mcosθ (2) where m is 0.5 times the module and θ is an angle represented by rad.

[0007] The problem of the rack tooth profile in this Itani-type tooth profile is that the curvature of the tooth profile curve reverses from plus to minus at the connection point between the tip tooth profile and the root tooth profile when the tooth profile curve passes through the pitch line. It is. The reversal of this curvature in the tooth profile of the rack also occurs in the gears 5A, 5B machined thereby. This means that when assembling a gear pump, strict precision is required for the mounting intervals of the gears 5A and 5B, and this is theoretically effective but not practical.

For this reason, at present, the tip curve of the tooth profile of the rack is corrected to x = mθ (1 + 0.3 cos θ) (3) y = 1.21 mcos θ (4), and the root curve of the tooth profile of the rack is modified. By changing the coefficient of the coordinate y from 1.2 to 1.21 in the above formulas (1) and (2), the meshing accuracy is lowered and the assembling workability is improved.

However, the gears 5A and 5B processed by the modified rack tooth form come into contact only with the pitch point, and in the case of the helical gear, the point contact is continuous along the twisted direction. The structure is such that the inlet side and the outlet side of the fluid communicate with each other, and there is a problem that the pump efficiency is reduced. For this reason, in gear pumps and the like used in hydraulic equipment, when the oil temperature rises and the viscosity of the oil decreases when the oil is rotated at high speed, the oil flows backward and the discharge rate decreases. In other words, the confinement of the fluid was a problem in the involute gear, but the modified Itaya-type tooth profile had the disadvantage that the reverse flow of the fluid reduced the efficiency.

[0010]

[Problems to be solved by the invention]

 The present invention eliminates the above drawbacks, and the power transmission section is formed by an involute curve with excellent power transmission, and the other part is formed by an arcuate curve, so that gear processing is easy and gear pump assembly workability is improved. The purpose of the present invention is to provide a gear for a gear pump which has improved pumping efficiency and has no pumping or backflow of fluid and has excellent pump efficiency.

[0011]

[Means for Solving the Problems]

 In the gear pump gear according to the present invention, the front and rear sides of the pitch circle are formed by an involute curve, and the tooth tip side and the root side continuous with the involute curve are formed by an arc-shaped curve, and the involute curve is formed. A helical gear that shares a tangent at the connection point of the arc curve and the arc curve, and the center of curvature at each point of the arc curve is located on the opposite side of the arc curve with respect to the pitch circle and formed by an involute curve. The portion is set to a range of 0.15 to 0.5 of 1 pitch.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 shows the tooth profile of the rack 6 according to the present invention. The front and rear E1-E2 are formed as oblique straight lines with the pitch line 7 interposed therebetween. The original side E1-E4 is formed by arcuate curved portions 9, 9, respectively. Furthermore, the tangents at the connection points E1, E2, E3, and E4 of the straight line portion 8 and the arc-shaped curved portion 9 are shared, and the center of curvature P at each point of the arc-shaped curved portions 9 is arc-shaped with the pitch line 7 interposed therebetween. It is formed so as to be located on the opposite side to the shape curves 9 and 9.

As shown in FIG. 2, gears 10 A and 10 B machined by the tooth shape of the rack 6 are formed by involutes E 1 ′ -E 2 ′ in front and behind the pitch circle 11 by machining the straight portion 8 of the rack 6. A helical gear formed by a curve 12 and having the tooth flank side E2'-E3 'and the tooth root side E1'-E4' continuous with the curve 12 processed by the arcuate curved part 9 of the rack to form arcuate curves 13,13. And the tangents at the connection points E1 ', E2', E3 ', E4' of the involute curve 12 and the arc-shaped curve 13 are shared.

Further, the center of curvature P ′ at each point of the arc-shaped curves 13, 13 is located on the opposite side of the arc-shaped curves 13, 13 with respect to the pitch circle 11, and the formation range of the involute curve 12 is one pitch. It is in the range of 0.15 to 0.5. In other words, the power transmission portion is formed by the involute curve 12 so that the power transmission efficiency is excellent, and other portions continuous with the power transmission portion are formed by the arc-shaped curves 13 and 13, and the center of curvature P 'at each point is a pitch circle. By placing the gears 10A and 10B on the opposite side of the arcuate curves 13 and 13 with the gear 11 interposed therebetween, the gears 10A and 10B are brought into one-point contact at the contact point C in a cross section perpendicular to the axis, as shown in FIG. A continuous line contact obliquely along the twisting direction of the helical gear can be achieved.

As a result, in the cross section perpendicular to the axis, since the contact point C is a single point contact, it is possible to prevent the fluid from being trapped as in the conventional involute gears 1A and 1B, and to continuously obliquely extend along the torsional direction of the helical gear. Since it is in line contact, there is no fluid backflow as in the modified Itani-type tooth profile, and power can be transmitted efficiently. In addition, since the tangents at the connection points E1 'to E4' of the involute curve 12 and the arc-shaped curve 13 are shared, the gears 10A and 10B can make smooth contact without a sharp change in curvature. Further, since the power transmission portion is formed by the involute curve 12, strict assembly accuracy is not required and the assembly workability is excellent.

In the present invention, the formation range of the involute curve 12 is set to the range of 0.15 to 0.5 of one pitch. If the range is less than 0.15, the range of the involute curve 12 is narrowed, and the power transmission efficiency is reduced. It is because it falls. Also, if it exceeds the range of 0.5, the range of the involute curve 12 becomes too wide, and there is a possibility that two-point contact may occur. Further, the arc-shaped curve 13 in the present invention may be formed by any of an sine curve, an elliptic curve, a perfect circular curve, and an n-order curve such as a quadratic curve.

Further, in the present invention, it is preferable that the meshing ratio of the gears is in the range of 0.2 to 0.4. In this case, if the meshing ratio is less than 0.2, the discharge pressure of the pump becomes small, and if it exceeds 0.4, the power transmission efficiency is improved, but the fluid may be trapped.

[0018]

【Example】

 Hereinafter, embodiments of the present invention will be described. Module 2.5, pressure angle 27 degrees, number of teeth 8 and helical angle 30 degrees, and the part formed by the involute curve has a pitch of 0. A gear 10A having a range of 346 was prepared, and the gear 10A was assembled in the housing 4 to assemble a gear pump. Using this gear pump, ISO. VG. Using 32 oil having a viscosity of 70 RW / sec, the suction pressure, the discharge pressure and the discharge amount at this time were measured while rotating at a rotation speed of 960 rpm. As a result, the volumetric efficiency (discharge flow rate / theoretical flow rate) was 78.7%.

For comparison, the gears 5A and 5B formed as a sine curve with a module 2.5, a pressure angle of 27 degrees, a number of teeth of 8, and a helical angle of 30 degrees are prepared by using a conventional modified Itaya type tooth profile. Then, a gear pump in which this was incorporated in the housing 4 was assembled. Using this gear pump, a test is performed under the same conditions as above. At this time, the suction pressure, the discharge pressure, and the discharge amount were measured. As a result, the volumetric efficiency was 68.7%. As a result, it was confirmed that the volume efficiency was improved by 10% in the present invention.

Further, the same experiment was conducted using low viscosity kerosene as a test solution. The volume efficiency of the gear pump of the present invention was 31.8%, and the volume efficiency of the modified Itaya gear tooth pump was 9%. It was confirmed that the efficiency was improved by 22% in the present invention.

The present invention can be applied not only to gears for gear pumps but also to gears for air motors.

[0022]

[Effect of the invention]

 As described above, according to the gear pump gear according to the present invention, the power transmission portion before and after the pitch circle is formed by an involute curve, and the tooth tip side and the root side continuous with the power transmission portion are formed by an arc-shaped curve. By using the helical gears, the machining of gears is easy, the workability of gear pump assembly is improved, and the efficiency of pumping is improved by preventing the trapping and backflow of fluid. It is effective at high speed rotation where viscosity decreases.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a tooth profile of a rack according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing tooth shapes of gears processed by the rack of FIG. 1;

FIG. 3 is an explanatory view showing a meshing portion of the gear pump in which the gears of the present invention are combined.

FIG. 4 is an explanatory diagram showing a gear pump using a conventional involute gear.

FIG. 5 is an explanatory diagram showing meshing portions of gears of a gear pump using a conventional involute gear.

FIG. 6 is a plan view of a rack for processing the involute gear.

FIG. 7 is an explanatory view showing a meshing portion of the conventional modified plate-valley type tooth profile.

FIG. 8 is an explanatory view showing a mesh portion of a plate-and-tooth-type toothed rack and gears processed by the rack.

[Explanation of symbols]

 Reference Signs List 1A involute gear 4 housing 5A gear 6 rack 7 pitch line 8 linear part 9 arc-shaped curve part 10A gear 11 pitch circle 12 involute curve 13 arc-shaped curve

Claims (1)

[Utility model registration claims] An involute curve is formed before and after a pitch circle, and a tip side and a root side connected to the involute curve are formed by an arcuate curve, and a tangent at a connection point between the involute curve and the arcuate curve. With a helical gear that shares
In addition, the center of curvature at each point of the arc-shaped curve is located on the opposite side of the arc-shaped curve with respect to the pitch circle, and the portion formed by the involute curve has a pitch of 0.15-0.
5. A gear for a gear pump, wherein the gear ratio is in the range of 5.