This invention relates generally to the field of devices used to sense, monitor, count or measure rotation of a shaft, axle, tube or the like in order to determine the number of revolutions in total or over a given time period, with the resulting data being used to determine the speed of rotation, velocity or distance traveled of a vehicle, etc. Such devices are known in general as tachometers. More particularly, the invention relates to such devices which are attached directly onto the rotating member, and even more particularly, to such devices which incorporate a bearing assembly having a plural number of ball, roller or other type individual bearing members and which are integral units, such that the sensing means is integral with the bearing assembly structure.
It is often necessary or desirable to monitor the rotation of a shaft or axle, such as for example an axle or drive shaft on a vehicle, in order to determine data for calculating the revolutions per minute (rpm), speed, distance traveled, etc. Apparatuses for accomplishing this task are known generally as tachometers, which are taken herein to include more specialized apparatuses commonly referred to as speedometers or odometers when the calculations of speed and distance are based on measurement of the rotation or a shaft or axle. For example, from knowledge of the circumference measurement of a wheel coupled with the number of revolutions of the wheel axle or drive shaft, the distance traveled can be calculated, and this coupled with a time period produces a speed value.
In many instances, it is desirable to provide an auxiliary tachometer device for use with vehicles in addition to the factory installed equipment, such as for example where it is desired to be able to measure amount of travel of the vehicle more precisely over short distances. While the standard odometer provides broad information in terms of mile tenths, it is useful in many circumstances to be able to precisely determine distances in terms of yards or feet. In these circumstances, auxiliary tachometers which are able to provide data in smaller increments are attached to the vehicle. These may take the form of a small wheel attached externally to the vehicle frame or pulled as a trailer, or may comprise equipment which is connected to a rotating component of the vehicle which rotates in response to or causes rotation of the vehicle wheels. For example, it is known to provide auxiliary tachometers which measure rotation of the vehicle speedometer or tachometer cable, or the drive shaft or wheel axles, by attachment of a target device or pulser ring to the rotating vehicle member. Separate sensing devices are then used to measure the rotation of the target device or pulser ring to determine the number of rotations of the rotating component. Other known devices sense rotation of vehicle drive train components themselves without attachment of separate target members, such as by monitoring the rotation of the CV joint itself for example.
Examples of such tachometer devices include U.S. Pat. No. 4,002,937 to Anson, U.S. Pat. No. 4,167,734 to Logan et al., U.S. Pat. No. 4,259,637 to Blomfield et al., U.S. Pat. No. 4,732,494 to Guers et al., U.S. Pat. No. 4,914,387 to Santos, U.S. Pat. No. 5,372,435 to Genero et al., U.S. Pat. No. 5,388,916 to Ohtsuki et al., U.S. Pat. No. 5,428,289 to Sahashi et al., U.S. Pat. No. 5,594,334 to Sonnerat et al., U.S. Pat. No. 6,007,250 to Brauer et al., U.S. Pat. No. 6,082,195 to Wallingford, and U.S. Pat. No. 6,111,401 to Mierzwinski. The prior art illustrates that it is known to provide target devices or pulser rings which provide rotational information to a sensor means. In most instances, the sensor means is separated by an exposed gap from the target device, which is detrimental in outdoor or rough duty environments, since the accuracy of the device can be affected by misalignment or by the accumulation of dirt and debris. In other instances, target devices and sensor means are mounted within bearing assemblies such that the apparatus is an integral unit enclosed by a housing, where the rotation of the target devices are detected by the sensor means.
It is an object of this invention to provide a rotation measuring device which comprises or incorporates a bearing assembly, such that the sensor means and target devices are maintained within an integral unit, wherein the device is directly attached to encircle the rotating shaft or axle of a vehicle or other equipment, and wherein the bearings themselves are the actual targets sensed by the sensor means. It is a further object to provide such a device which is multi-sectional, such that the device can be connected to or removed from a shaft or axle without requiring the shaft or axle to have a free end over which the device may be slipped, thereby enabling the device to be attached and removed from the shaft or axle without requiring disassembly of the shaft or axle mounting structure.
In general, the invention device is a bearing assembly with integral sensing means which is attached directly to a rotating shaft, axle, tube or other such rotating member, such as for example the drive shaft or axle on a motor vehicle, or the shaft of a lathe or other piece of equipment, where the device senses and measures the rotation of the rotating member so that determination of desired data can be obtained, such as the total accrued number of revolutions, the number of revolutions per time period, the speed of rotation, the speed of a motor vehicle, the distance traveled by a motor vehicle, etc. The bearing assembly may incorporate ball, roller or other type bearing members.
The bearing assembly comprises an inner ring or race which is connected directly onto the rotating shaft member, and preferably comprises two semi-annular halves or greater than two partial arc segments joined to form a complete ring. A compressible mounting ring is preferably disposed between the inner ring and the rotating shaft member to insure that the inner ring is secured so that it will not rotate independently of the shaft member. The outer surface of the inner ring comprises bearing retaining means such as bearing seats or a cage structure to retain the bearing members in fixed, equally-spaced, circumferential positions about the inner ring, such that the bearings may rotate or revolve freely within the bearing retaining means but the relative positions of the bearings on the inner ring will not change. In this manner each bearing will make a complete 360 degree rotation relative to the central axis of the shaft member for each complete 360 degree rotation of the inner ring member and the rotating shaft member. The bearing assembly further comprises an outer ring or race which contains an interior track or channel to receive the bearing members. The outer ring is also preferably comprised of two semi-annular halves or greater than two partial arc segments joined to form a complete ring encircling the inner ring in a manner whereby the inner ring is free to rotate independently of the outer ring. The outer ring is fixed so as to be non-rotating, which may be accomplished by connecting the outer ring to a stationary component of the vehicle or piece of equipment to which the device is attached. The outer ring is most preferably provided with collar flanges or other housing means to enclose the bearing members and the inner race to prevent debris from contacting the bearings. Because the bearing assembly is sectional, it can be applied to a shaft or axle which does not have an exposed end.
Sensor means are provided in the outer ring itself, which sensor means may comprise a Hall Effect, optical or other type sensor. The sensor means detects each passage of a bearing member as the inner ring member and shaft member rotates, the bearing members themselves being the targets for the sensor means, which data is then interpreted or analyzed to determine the desired information for the equipment being monitored, such as rpm, speed, distance traveled, etc.