JPH0240893B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a worm transmission with cyclically varying loads, in which the varying loads always act on the same tooth range of the worm gear, and the worm gear has concave or globoid teeth. .

Worm transmissions are known in which the worm gear has spur teeth which make it possible to install the worm gear later when the worm is already installed in the housing. Such an installation is possible because the tooth profile of a worm gear with spur teeth is the same over the entire tooth width and is parallel to the axis of rotation of the worm gear. A disadvantage of worm transmissions constructed in this way is that the engaged threads of the worm only make point contact with the momentary engaged teeth of the worm gear. The specific load of the worm and especially of the spur teeth is particularly high when the load acting on the worm gear reaches its maximum value. When using a worm gear with concave teeth or globoid teeth, it is known that the contact between the cylindrical worm and the globoid tooth worm gear is a line contact, which significantly reduces the tooth specific load. It is simply not possible to install a transmission constructed in the manner described above. That is, the worm gear must first be installed, and then the worm must be screwed into the teeth of the worm gear like a screw.

According to the invention, in order to avoid these drawbacks:
When the teeth of the worm gear in the circumferential area that receives a smaller load are removed from the side that will be engaged first to approximately the center of the width of the worm gear when it is assembled into the worm that has already been incorporated into the case. ing.

Such a worm transmission has the advantage that when a maximum load is applied to the transmission, the tooth sections of the worm gear, which are configured as concave or globoid teeth, mesh with the worm, thereby reducing the specific load of the teeth. ing. On the other hand, the partially removed circumferential area of the teeth of the worm gear is engaged with the cylindrical worm during installation, so that the transmission can be assembled easily. Moreover, when incorporating
If care is taken that the circumferential region of the worm gear in which some of the teeth are removed is in a circumferential region which is subject to small loads, no disadvantages arise with respect to the specific loading of the teeth in this circumferential region.

Embodiments of the invention are described below with reference to the drawings.

According to the principle diagram shown in FIG. 1 of a window cleaning device for an automobile, a worm 12 of a worm transmission 10 belonging to this window cleaning device is connected to an output shaft of a drive motor (not shown). The transmission worm, configured as a cylindrical worm 12, meshes with a gear wheel 14 made of plastic and having concave or globoid teeth. The worm gear 14 is located on a worm gear shaft 16, and a crank 18 that rotates together with the worm gear 14 is fixedly connected to this gear shaft 16. A connecting rod 20 is pivotally connected to the free end of the crank 18, and the other end of the connecting rod 20 is pivotally connected to a swing piece 22 fixed on a window cleaning shaft 24 supported by the vehicle body. The window cleaning blade 2 is installed via the window cleaning arm 26 attached to the window cleaning shaft 24.
8 is connected to the window cleaning shaft 24. When the window cleaning device is in operation, the crank 18 rotates in the direction of the arrow 30, thereby moving the connecting rod 20 in the direction of the double arrow 32 and entraining the rocker piece 22 in the direction of the double arrow 34. . The rocker piece 22 then swings over an angle α from one reversal position to the other reversal position. Therefore, the crank 18, the connecting rod 2
0 and the rocker piece 22 form a rocker transmission. However, together with the swinging piece 22, the window cleaning shaft 24 and therefore also the window cleaning blade 28 are moved by the double arrows 36 and 3.
It makes a rocking motion as shown at 8. The window wiping blade 28 is rubbed over a not shown wiping area 40 of the vehicle window. The wiping area 40 has a fan shape, and the swing angle β of the window wiping blade 28 is equal to the swing angle α of the swing piece 22.
be equivalent to.

It is clear that the torque acting on the transmission 10 varies as a function of the respective position of the window wiping blade 28 in the wiping area 40. This torque then decreases to approximately zero in the region of the reversal position 42 of the window cleaning blade 28 and reaches its maximum value when the window cleaning blade 28 is in the central area of the wiping zone 40 shown in FIG. The worm transmission 10 is therefore subjected to periodically varying loads. To simplify installation, it is provided that the worm gear 14 is inserted into the housing 44 surrounding the worm gear 10 only when the worm 12 has already been installed. Therefore, the worm gear 14 meshes with the worm 12 perpendicular to the plane of the drawing. It should be taken into account that at the same time the worm gear 16 must also be placed in a bearing (not shown) in the transmission case 44. Such an installation is not possible if the worm gear 14 also has so-called concave or globoid teeth.

Therefore, according to the present invention, as shown in FIG.
However, in order to avoid the installation difficulties mentioned at the beginning, the globoid teeth 54 are removed in a relatively small circumferential range to approximately the center of the worm gear width 50, so that the worm gear 14 in this circumferential range is It is possible to have globoid teeth 70 reaching the center of the gear width 50 only from the side faces 72.

By specially configuring the small circumferential area of each worm gear 14 as described above, each worm gear 14 can be moved from the toothed side to the preinstalled worm 12 as described above. Can be interlocked. However, when assembling, care must be taken that the device that applies torque to the worm transmission 10 (in this case, the window cleaning blade 28) is in a position where only a small force, as much as possible, is applied to the worm transmission 10. be. As a result, when the worm gear 10 is loaded by the device to a large extent, the worm 12 meshes with the complete globoid teeth 54, where the specific load of the teeth is significantly reduced.

The worm gear 14 is made from plastic,
A particularly economical production of the worm gear 14 with a special shape 70 is possible, preferably by injection molding.

[Brief explanation of drawings]

Figure 1 is a basic configuration diagram of an automobile window cleaning device with a worm transmission, Figure 2 is a sectional view of the toothed portion of the worm gear in Figure 1 taken along the - line, and Figure 3 is the worm gear in Figure 1. It is a sectional view along the - line of a gear. 10...Worm transmission device, 12...Worm, 1
4... Worm gear, 50... Worm gear width, 7
0... Globoid teeth.

Claims (1)

[Claims] 1. In a case where a changing load always acts on the same tooth range of the worm gear, and the worm gear has concave teeth or globoid teeth, the circumferential range of the worm gear 14 that receives the tooth load. A cycle characterized in that the teeth 70 in the circumferential region which are subject to small loads are removed from the side that engages first during installation into the worm 12 already installed in the case 44 to approximately the center of the width 50 of the worm gear. A worm transmission device whose load changes over time. 2. The worm transmission device 10 belongs to a drive device of a window cleaning device of an automobile, and the rocking transmission devices 18, 20, 22 provided after this drive device are connected to the window cleaning blade 2.
The worm transmission device according to claim 1, characterized in that the worm transmission device is connected to the worm transmission device 8. 3. Claims characterized in that the circumferential area of the worm gear 14 of the worm gear 10 in which the teeth 70 have been removed up to approximately the center of the width 50 meshes with the worm 12 in the reversal position 42 of the window cleaning blade 28. The worm transmission device according to item 2. 4. Worm transmission according to claim 1, characterized in that the worm gear 14 is made of plastic.