Worm helical gear transmission pair based on variable pressure angle and its application

Abstract

The present invention discloses a worm helical gear transmission pair based on variable pressure angle and its use; the worm helical gear transmission pair has reliable transmission, durability and easy manufacturing. In order to achieve the above-mentioned purpose, the present invention is a worm helical gear transmission pair based on variable pressure angle, comprising a worm and a helical gear meshing with each other; the helical gear end face module (Mt2) = the worm shaft face module (Ma1); the helical gear end face indexing circular tooth profile angle (αn2)> the worm shaft face indexing circular tooth profile angle (αn1); the helical gear indexing circle helix angle (β2) = the worm shaft face indexing circle lead angle (λ1); the helical gear end face indexing circular tooth profile angle (αn2)-worm shaft face indexing circular tooth profile angle (αn1) is less than 10°.

Description

Technical Field

[0001] The invention relates to a worm helical gear transmission pair, in particular to a transmission pair in which a metal worm is meshed with a plastic helical gear. Background Art

[0002] Worm helical gear transmission has completely replaced worm gear transmission in the occasions where the transmission contact force surface is not large (medium and light load) and the transmission accuracy is not strictly required, and is widely used in the fields of automobiles, kitchen appliances, etc. Automobile motors (wipers, window rollers, etc.) using worm helical gear transmission are required to have high quality reliability, low noise, long life and low cost, which has become the working direction of the enterprise;

[0003] Traditional theory holds that the correct meshing conditions for worm and helical gear transmission are: Mt2 (helical gear end face module) = Ma1 (worm shaft face module); αt2 (helical gear end face pitch circle tooth profile angle) = αa1 (worm shaft face pitch circle tooth profile angle); β2 (helical gear pitch circle helix angle) = λ1 (worm shaft face pitch circle lead angle); that is, the conditions of equal module, pressure angle and helix angle must be met.

[0004] As a result, in order to meet the meshing conditions of traditional gear theory, the worm and plastic gear are usually non-standard gears, which undoubtedly greatly increases the difficulty of plastic gear processing. Usually, plastic gears need to be processed by injection molding, which creates some problems:

[0005] 1. Gear injection molds require high precision, are difficult to manufacture, and have a long cycle;

[0006] 2. Gear injection molding equipment, high precision requirements and strict process;

[0007] 3. The gear material requirements are high and the deformation must be small. Due to the different thickness of the gears, the tooth shape is easy to deform and the stability is poor.

[0008] We have conducted a long period of research on the above technical issues. The method we currently use to solve the above technical problems is that in the transmission of metal worm and plastic helical gear, due to the different material properties and strengths of metal and plastic, we use the tangential displacement method to thin the thickness of the worm tooth profile and correspondingly thicken the thickness of the helical gear tooth profile, so that the metal worm teeth and plastic helical gears can withstand the same force, avoid plastic gear tooth breakage, and meet the motor life requirements; at the same time, in order to ensure less noise, the worm usually uses a smaller non-standard pressure angle (tooth angle such as 10°, 14.5°, etc.); to meet the above requirements, the worm and plastic helical gear are non-standard gears (usually non-standard pressure angle and tooth thickness), and the plastic helical gear needs to be processed by injection molding; similarly, the injection mold has high precision requirements, high cost, long processing cycle, and large deformation of the injection molded gear tooth profile (uneven tooth thickness), which is not conducive to new product development and mass production. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a worm helical gear transmission pair based on variable pressure angle and its use in view of the deficiencies in the above-mentioned prior art; the worm helical gear transmission pair has reliable transmission, durability and easy manufacturing.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] A worm-helical gear transmission pair based on a variable pressure angle comprises a worm and a helical gear meshing with each other;

[0012] The helical gear end face module (Mt2) = the worm shaft face module (Ma1);

[0013] The pitch circular tooth profile angle of the helical gear end face (αn2)> the pitch circular tooth profile angle of the worm shaft face (αn1);

[0014] Helical gear pitch circle helix angle (β2) = worm shaft pitch circle lead angle (λ1);

[0015] The helical gear end face indexing circular tooth angle (αn2)-the worm shaft face indexing circular tooth angle (αn1) is less than 10°.

[0016] The characteristics and further improvements of the above embodiments of the present invention are:

[0017] (1) When the end face module (Mt2) of the helical gear is equal to the axial module (Ma1) of the worm gear; the end face pitch circle tooth profile angle (αn2) of the helical gear is equal to the axial face pitch circle tooth profile angle (αn1) of the worm gear; and the pitch circle helix angle (β2) of the helical gear is equal to the pitch circle lead angle (λ1) of the worm gear, the center distance between the helical gear and the worm gear is L1;

[0018] When the end face module (Mt2) of the helical gear is equal to the axial module (Ma1) of the worm; the end face pitch circle tooth profile angle (αn2) of the helical gear is greater than the axial face pitch circle tooth profile angle (αn1) of the worm; and the pitch circle helix angle (β2) of the helical gear is equal to the pitch circle lead angle (λ1) of the worm, the center distance between the helical gear and the worm is L2;

[0019] Center distance increase (ΔL) = L2-L1;

[0020] Helical gear end face module × 10% ≤ ΔL ≤ helical gear end face module × 30%.

[0021] (2) The helical gear end face pitch circular tooth angle (αn2) - the worm shaft face pitch circular tooth angle (αn1) is less than 5 degrees.

[0022] (3) The helical gear end face module (Mt2) = the worm shaft face module (Ma1) = 0.8;

[0023] The helical angle of the pitch circle of the helical gear (β2) = the lead angle of the pitch circle of the worm shaft surface (λ1) = 7.59389°;

[0024] The helical gear end face indexing circular tooth angle (αn2) = 20°;

[0025] The worm shaft face indexing circular tooth angle (αn1) is 14.5°.

[0026] Furthermore, the center distance increase (ΔL) = 0.15 mm.

[0027] Furthermore, the pitch circle diameter of the helical gear is 48.56 mm; the pressure angle at the pitch circle of the helical gear is 14.5°; and the root circle diameter of the helical gear is 48.3 mm.

[0028] Furthermore, the number of teeth, normal tooth profile angle, tooth top height coefficient, radial modification coefficient, helix line direction, pitch cylindrical helix angle and span tooth number of the helical gear are 62, 20°, 1, +0.162, right, 7°35′38″ and 6 respectively.

[0029] Furthermore, the number of worm heads, normal tooth profile angle, helix direction, radial displacement coefficient, measuring column measuring distance, measuring column diameter, helix lead angle, axial tooth pitch, diameter coefficient, pitch circle diameter and root circle diameter of the worm are: 1, 14.5°, right-handed, 0, 8.65mm, 1.75mm, 7°35′38″, 2.535mm, 7.5, 6.05mm and 4.5mm respectively.

[0030] The present invention also discloses a use of the above-mentioned worm helical gear transmission pair, characterized in that the worm helical gear transmission pair is used for an automobile wiper motor, the automobile wiper motor comprises a drive motor, the drive motor drives a worm connected to the worm helical gear transmission pair; the worm of the worm helical gear transmission pair drives the automobile wiper to swing.

[0031] Furthermore, the swing amplitude of the automobile wiper is 90 degrees or 160 degrees.

[0032] The beneficial effects of the present invention are:

[0033] Under the condition that the worm and the helical gear have the same module (standard module Mn=0.8) and the worm lead angle is the same as the helical gear spiral angle (7.59389°), the present invention adopts different pressure angles (tooth profile angles) design, the worm pressure angle (14.5°), and the plastic gear is designed as the standard pressure angle (20°). The plastic gear adopts the design of the standard (large) pressure angle, so that the standard hobbing method can be used to process the plastic gear. Without opening the injection mold or only opening the tooth blank mold, new product development and mass production can be carried out, which solves the problem that the plastic gear is difficult to process and the tooth profile is easy to deform in the worm helical gear transmission, improves the gear processing accuracy, reduces noise, reduces the product development cycle, cost and risk, and meets the requirements of long product life and low noise (50dB / 30CM). It is now in mass production and supply.

[0034] The present invention is specific:

[0035] 1. The design of variable pressure angle is adopted. Compared with the design of same pressure angle, the contact line (force line) between the worm gear and the plastic gear has changed. The change is positively correlated with the angle change. Therefore, the angle change should be less than 5° and usually not more than 10°.

[0036] 2. In order to ensure good meshing between the worm gear and the plastic gear at different pressure angles, the center distance can be appropriately increased. It is recommended to be 10% to 30% of the module. We increased it by 0.2mm in the specific embodiment.

[0037] 3. The variable pressure angle design is adopted, but the gear meshing line (pitch circle) does not change, and the gear transmission ratio does not change;

[0038] 4. Since the transmission coefficient is >> 1, the requirement of stable transmission is also met;

[0039] 5. In order to further improve the strength of plastic gears, plastic gears adopt positive displacement. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The schematic diagram of the structure of the tooth blank processed by the injection mold;

[0041] Figure 2 It is a schematic diagram of the structure of the helical gear after gear hobbing by the gear hobbing machine;

[0042] Figure 3 It is a schematic structural diagram in a top view of a specific embodiment of the helical gear of the present invention;

[0043] Figure 4 for Figure 3 AA section structural diagram;

[0044] Figure 5It is a structural schematic diagram of a specific embodiment of the worm of the present invention;

[0045] Figure 6 It is a three-dimensional structural schematic diagram of a specific embodiment of a wiper motor adopting the worm helical gear transmission pair of the present invention;

[0046] Figure 7 for Figure 6 Schematic diagram of the structure from the top view.

[0047] Description of reference numerals:

[0048] 1- helical gear, 2- shaft. DETAILED DESCRIPTION

[0049] The specific implementation of the present invention is described below in conjunction with the accompanying drawings and embodiments:

[0050] like Figures 1 to 7 As shown, it shows a specific embodiment of the present invention. The present invention is based on a worm helical gear transmission pair with a variable pressure angle, comprising a worm and a helical gear meshing with each other; it is characterized in that:

[0051] The helical gear end face module (Mt2) = the worm shaft face module (Ma1);

[0052] The pitch circular tooth profile angle of the helical gear end face (αn2)> the pitch circular tooth profile angle of the worm shaft face (αn1);

[0053] Helical gear pitch circle helix angle (β2) = worm shaft pitch circle lead angle (λ1);

[0054] The helical gear end face indexing circular tooth angle (αn2)-the worm shaft face indexing circular tooth angle (αn1) is less than 10°.

[0055] In some specific embodiments:

[0056] When the end face module (Mt2) of the helical gear is equal to the axial module (Ma1) of the worm gear; the end face pitch circle tooth profile angle (αn2) of the helical gear is equal to the axial face pitch circle tooth profile angle (αn1) of the worm gear; and the pitch circle helix angle (β2) of the helical gear is equal to the pitch circle lead angle (λ1) of the worm gear, the center distance between the helical gear and the worm gear is L1;

[0057] When the end face module (Mt2) of the helical gear is equal to the axial module (Ma1) of the worm; the end face pitch circle tooth profile angle (αn2) of the helical gear is greater than the axial face pitch circle tooth profile angle (αn1) of the worm; and the pitch circle helix angle (β2) of the helical gear is equal to the pitch circle lead angle (λ1) of the worm, the center distance between the helical gear and the worm is L2;

[0058] Center distance increase (ΔL) = L2-L1;

[0059] Helical gear end face module × 10% ≤ ΔL ≤ helical gear end face module × 30%.

[0060] Due to the different pressure angles, the meshing of the worm and the helical gear requires a larger gear backlash to make the worm tangent to the helical gear on the pitch circle and avoid interference. We increase the gear backlash by increasing the center distance; the amount of backlash that needs to be increased is equal to the increase in the pitch circle thickness of the helical gear. In addition to considering the clearance factor in the value of the gear common normal, the center distance is appropriately increased under the condition of ensuring the overlap to increase the gear backlash, so that the worm tooth surface can be tangent to the plastic tooth surface near the pitch circle and mesh, ensuring a good meshing state.

[0061] In a specific embodiment, we increase the thickness of the plastic gear indexing circle tooth shape by 0.1MM, and reversely calculate the center distance change Δa = normal line change ΔL / 2xTan20°=0.1 / 2xTan20°=0.137 (mm); the actual center distance is increased by 0.15mm (actual processing 28.2-theoretical calculation 28.05=0.15), which is greater than 0.137mm.

[0062] Another reason for using a larger gear backlash is to take into account the thermal expansion of plastic gears during load.

[0063] In some specific embodiments: the helical gear end face pitch circular tooth angle (αn2) - the worm shaft face pitch circular tooth angle (αn1) is less than 5 degrees.

[0064] In a preferred embodiment:

[0065] The helical gear end face module (Mt2) = the worm shaft face module (Ma1) = 0.8;

[0066] The helical angle of the pitch circle of the helical gear (β2) = the lead angle of the pitch circle of the worm shaft surface (λ1) = 7.59389°;

[0067] The helical gear end face indexing circular tooth angle (αn2) = 20°;

[0068] The worm shaft face indexing circular tooth angle (αn1) is 14.5°.

[0069] As a further improvement of the above preferred embodiment: the center distance increase (ΔL) = 0.15 mm.

[0070] As a further improvement of the above preferred embodiment: the pitch circle diameter of the helical gear is 48.56 mm; the pressure angle at the pitch circle of the helical gear is 14.5°; the root circle diameter of the helical gear is 48.3 mm.

[0071] As an improvement of a further implementation of the above preferred embodiment: the number of teeth, normal tooth profile angle, tooth top height coefficient, radial modification coefficient, helix line direction, pitch cylindrical helix angle and number of teeth across the helical gear are respectively: 62, 20°, 1, +0.162, right, 7°35′38″ and 6.

[0072] As an improvement of a further implementation of the above preferred embodiment: the number of worm heads, normal tooth profile angle, helix direction, radial displacement coefficient, measuring cylinder measuring distance, measuring cylinder diameter, helix lead angle, axial tooth pitch, diameter coefficient, pitch circle diameter and root circle diameter of the worm are respectively: 1, 14.5°, right-handed, 0, 8.65mm, 1.75mm, 7°35′38″, 2.535mm, 7.5, 6.05mm and 4.5mm.

[0073] Regarding the embodiment of the use of the above-mentioned worm helical gear transmission pair disclosed in the present invention, we specifically use the worm helical gear transmission pair for an automobile wiper motor, and the automobile wiper motor includes a driving motor, and the driving motor drives a worm connected to the worm helical gear transmission pair; the worm of the worm helical gear transmission pair drives the automobile wiper to swing.

[0074] Preferably, the swing amplitude of the automobile wiper is 90 degrees or 160 degrees.

[0075] In view of the creative achievements of the present invention, we tested the automobile wiper motor sample with the worm helical gear transmission pair, and the test results are shown in the following table (life test report):

[0076]

[0077] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the field without departing from the purpose of the present invention. These changes involve related technologies well known to those skilled in the art, which all fall within the scope of protection of the patent of the present invention.

[0078] Many other changes and modifications may be made without departing from the concept and scope of the present invention.It should be understood that the present invention is not limited to the specific embodiments, and the scope of the present invention is defined by the appended claims.

Claims

1. A worm helical gear transmission pair based on a variable pressure angle, comprising a worm and a helical gear meshing with each other; the worm is a metal worm, and the helical gear is a plastic helical gear; characterized in that: Helical gear end module (Mt2) = worm shaft module (Ma1); The pitch circular tooth profile angle of the helical gear end face (αn2)> the pitch circular tooth profile angle of the worm shaft face (αn1); Helical gear pitch circle helix angle (β2) = worm shaft pitch circle lead angle (λ1); When the end face module (Mt2) of the helical gear is equal to the axial module (Ma1) of the worm gear; the end face pitch circle tooth profile angle (αn2) of the helical gear is equal to the axial face pitch circle tooth profile angle (αn1) of the worm gear; and the pitch circle helix angle (β2) of the helical gear is equal to the pitch circle lead angle (λ1) of the worm gear, the center distance between the helical gear and the worm gear is L1; When the end face module (Mt2) of the helical gear is equal to the axial module (Ma1) of the worm; the end face pitch circle tooth profile angle (αn2) of the helical gear is greater than the axial face pitch circle tooth profile angle (αn1) of the worm; and the pitch circle helix angle (β2) of the helical gear is equal to the pitch circle lead angle (λ1) of the worm, the center distance between the helical gear and the worm is L2; Center distance increase (ΔL) = L2-L1; The module of the end face of the helical gear × 10% ≤ the increase in the center distance ≤ the module of the end face of the helical gear × 30%; the helical gear end face indexing circular tooth angle (αn2) - the worm shaft face indexing circular tooth angle (αn1) is less than 5 degrees.

2. The worm helical gear transmission pair based on variable pressure angle according to claim 1, characterized in that: The helical gear end face module (Mt2) = the worm shaft face module (Ma1) = 0.8; The helical angle of the pitch circle of the helical gear (β2) = the lead angle of the pitch circle of the worm shaft surface (λ1) = 7.59389°.

3. The worm helical gear transmission pair based on variable pressure angle according to claim 2, characterized in that: The center distance increase (ΔL) = 0.15 mm.

4. The worm helical gear transmission pair based on variable pressure angle according to claim 2, characterized in that: The pitch circle diameter of the helical gear is 48.56 mm; the pressure angle at the pitch circle of the helical gear is 14.5°; and the root circle diameter of the helical gear is 48.3 mm.

5. The worm helical gear transmission pair based on variable pressure angle according to claim 2, characterized in that: The number of teeth, normal tooth profile angle, tooth top height coefficient, radial modification coefficient, helix line direction, pitch cylindrical helix angle and span tooth number of the helical gear are: 62, 20°, 1, +0.162, right, 7°35′38″ and 6, respectively.

6. The worm helical gear transmission pair based on variable pressure angle according to claim 2, characterized in that: The number of worm heads, normal tooth profile angle, helix direction, radial displacement coefficient, measuring cylinder measuring distance, measuring cylinder diameter, helix lead angle, axial tooth pitch, diameter coefficient, pitch circle diameter and root circle diameter of the worm are: 1, 14.5°, right-handed, 0, 8.65mm, 1.75mm, 7°35′38″, 2.535mm, 7.5, 6.05mm and 4.5mm respectively.

7. A windshield wiper motor for an automobile, characterized in that: It comprises the worm helical gear transmission pair as described in any one of claims 1 to 6, wherein the automobile wiper motor comprises a driving motor, and the driving motor drives a worm connected to the worm helical gear transmission pair; the worm of the worm helical gear transmission pair drives the automobile wiper to swing.

8. The automobile wiper motor according to claim 7, characterized in that: The swing amplitude of the automobile wiper is 90 degrees or 160 degrees.

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