Support structure for rotation speed sensors

Details Support structure for rotation speed sensors Support structure for rotation speed sensors

1998-10-13

2001-03-20

Marmor, Charles A (Department: 3681)

Planetary gear transmission systems or components

Electric or magnetic drive or control

Differential drive or control

C475S230000

Reexamination Certificate

active

06203464

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a support structure of sensors for detecting the number of rotation of a bevel gear. More specifically, the present invention relates to a sensor support structure for detecting the number of the rotation of a ring gear of a differential apparatus provided in vehicles, based on detecting the teeth of the ring gear.
FIG. 3
shows part of a prior art differential apparatus
20
. As shown in the figure, the differential apparatus
20
has an outer case
23
and an inner case
27
. The inner case
27
is rotatably supported in the outer case
23
. A ring gear
21
, which is a bevel gear, is fixed to the inner case
27
. The ring gear
21
is meshed with a drive pinion (not shown) fixed to the distal end of a drive shaft (not shown). When the drive shaft rotates, the ring gear
21
rotates with the inner case
27
. The rotation of the ring gear
21
is transferred to right and left axles
30
(only one is shown) by differential gears
28
,
29
in the inner case
27
.
A magnetic sensor
22
is installed in the differential apparatus
20
to detect the rotation speed of the ring gear
21
. The magnetic sensor
22
is inserted in an installation hole
24
provided in the outer case
23
. The magnetic sensor
22
is fixed to the outer case
23
, with a positioning flange
22
a
in contact with a positioning surface
24
a
of the hole
24
.
The magnetic sensor
22
includes a detection surface
25
facing the edge
26
a
of each tooth
26
of the ring gear
21
. When the ring gear
21
rotates, the magnetic sensor
22
detects the teeth that pass by the detection surface
25
. Accordingly, the rotation speed of the ring gear
21
is obtained based on the detected number of the teeth
26
per unit time. The speed of the ring gear
21
may be used to determine the vehicle speed.
The magnetic sensor
22
includes a magnet and a magnetic detection element such as an electromagnetic pickup coil, a hall element, and a magnetic resistance element. The magnetic flux from the magnet extends through the detection surface, and a magnetic path is formed between the detection surface
25
and the ring gear
21
. The ring gear
21
forms a part of the magnetic path. When the teeth
26
pass by the detection surface
25
with the rotation of the ring gear
21
, the magnetic resistance and the magnetic flux of the magnetic path between the detection surface
25
and the ring gear
21
change. The magnetic detection element outputs signals in accordance with the change of the magnetic flux. Accordingly, the teeth
26
, which pass by the detection surface, are detected based on the signals.
The sensitivity of the magnetic sensor
22
is greatly influenced by the space between the tooth edge
26
a
and the detection surface
25
. Accordingly, the magnetic sensor
22
is installed in the outer case
23
with the detection surface
25
as near as possible to the tooth edge
26
a
, taking into consideration the error of measurement of the teeth edges and the error of the installation position of the magnetic sensor
22
in the axial direction.
During assembly of the differential apparatus
20
, the position of the inner case
27
in the axial direction is set to adjust the backlash between the ring gear
21
and the drive pinion. When the axial position of the inner case
27
changes, the space between the detection surface
25
of the magnetic sensor and the tooth edge
26
a
of the ring gear
21
changes. Since the position of the inner case
27
is adjusted in each individual differential apparatus
20
, the space between the detection surface
25
and the tooth edge
26
a
differs from one differential apparatus
20
to another. Accordingly, the sensitivity of the magnetic sensor
22
differs in each differential apparatus
20
. Also, when the space between the detection surface
25
and the tooth edge
26
a
is too large, the magnetic sensor
22
will not be able to detect gear teeth.
Thus, to keep the space between the detection surface and the tooth edge
26
a
constant, it was necessary to adjust the assembly position of the magnetic sensor
22
in the axial direction, for example, by arranging a shim (not shown) between the positioning flange
22
a
and the positioning surface
24
a
of the hole
24
. This complicates the installation of the magnetic sensor
22
. Even if the differential apparatus
20
assembled in this way is installed in a vehicle, the axial position of the inner case
27
can change when the rotation direction of the drive shaft is changed. Therefore, fluctuation of the sensitivity of the magnetic sensor
22
was not completely prevented by using a shim.
SUMMARY OF THE INVENTION
The present invention is designed to solve the above problem. The objective of the invention is to provide a support structure for a sensor that maintains a constant minimum space between the teeth of a bevel gear used for a differential apparatus and the sensor for detecting the rotation speed of the bevel gear.
To achieve the above objective, the present invention provides an apparatus including a bevel gear and a sensor for detecting the rotation speed of the bevel gear. One side of the bevel gear has a plurality of teeth. Each tooth has an outer end surface that is parallel to the rotation axis of the bevel gear. The sensor is spaced from the gear and radially faces the axis of the gear. The sensor detects at least one of the teeth passing by the sensor when the bevel gear rotates.
The present invention further provide a differential apparatus for vehicles. The differential apparatus includes an outer case, an inner case rotatably supported in the outer case, and a ring gear fixed to the inner case. One side of the ring gear includes a plurality of teeth. Each tooth has an outer end surface that defines a cylinder, which is coaxial to the bevel gear. A drive pinion is rotatably supported in the outer case to mesh with the ring gear. The axial position of the inner case is adjustable to adjust the backlash between the ring gear and the drive pinion. A sensor is installed in the outer case to face the periphery of the ring gear, wherein the sensor detects at least one of the teeth passing by the sensor.
The present invention further provides a bevel gear having a plurality of teeth. Each tooth includes an outer end surface that defines a cylinder that is coaxial to the bevel gear.
Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.


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