Patent Description:
Many machines include one or more components that rotate relative to one another. For example, excavators include a cabin disposed on top of a lower frame or undercarriage, with the cabin rotatable with respect to the undercarriage. These machines may include a positioning system that includes a motor that rotates a gear assembly associated with a swing gear train, which in turn, rotates the house. There is a general need to improve the accuracy at which the rotation is determined, so that the cabin can more accurately rotate to the desired position. There is also a general need for an accurate rotation measurement system that can be retrofitted to existing machines.

Sensors can monitor the actual position of the cabin and accuracy of the sensors can improve reliability for some control applications. Some machines include a position-sensing system with a sensor that generates a signal related to proximity of the sensor element to a component or to a projection of a component, such as a gear tooth. Other position-sensing systems may include a sensor that senses rotational movement of a component, such as a gear. Unfortunately, a number of factors may cause significant variations in the values of the signals generated by such sensors. For example, vibrations, temperature variations, variations in the characteristics of the sensor and/or variations in the characteristics of power supplied to the sensor may increase or decrease the sensor signal value. Because of variations in such parameters, a position-sensing system employing one or more sensors may be inaccurate and therefore more robust position-sensing systems are needed.

<CIT> discusses a slew position sensing system that includes a swing sensor housing coupled to a rotary position sensor or speed sensor to detect rotation of target gear.

<CIT> relates to tracked vehicle motion correction and discloses a working machine that includes an undercarriage supported by first and second ground engaging units powered by first and second drive units, a main frame supported by the undercarriage, a first sensor configured to sense an orientation and relative angular motion of the main frame with respect to the undercarriage, a second sensor configured to sense an orientation and relative angular motion of the main frame in an external reference frame independent of the undercarriage, and a controller functionally linked to the first and second sensors. The controller is configured to receive commands corresponding to an intended movement of the first and second ground engaging units, and generate control signals to the first and second drive units to achieve or maintain the intended movement taking into account a detected orientation of the main frame relative to the undercarriage and a detected orientation of the main frame in the external reference frame.

In accordance with the present invention, a positioning system as set forth in claim <NUM> is provided. Preferred embodiments of the invention are claimed in the dependent claims.

<FIG> shows a side view of an excavator <NUM>, in accordance with this disclosure. While example embodiments are described with reference to an excavator <NUM>, examples according to this disclosure are applicable to a variety of types of work machines, including cranes or other machines in which an attached body rotates (using, e.g., a gear, bearing or sprocket mechanism) relative to another body of the work machine.

Referring to <FIG>, an excavator <NUM> may include an upper structure <NUM>, a lower structure <NUM> and a working element <NUM>. The upper structure <NUM> may include a body <NUM> and an operator cab <NUM>. The operator cab <NUM> is mounted on the body <NUM>. The operator cab <NUM> may include devices that receive input from a machine operator which may indicate a desired maneuvering of the excavator <NUM>. Specifically, the operator cab <NUM> may include one or more operator interface devices. Examples of operator interface devices include, but are not limited to, a joystick, a travel control lever, and/or a pedal (none of which are shown but are well known in the industry).

The lower structure <NUM> may comprise a pair of tracks <NUM>, to drive the excavator <NUM> on a path. The pair of tracks <NUM> may be driven by a hydrostatic transmission or by electric travel motors which, in turn, are powered by a prime mover such as an internal combustion engine (not shown).

The working element <NUM> includes a boom <NUM>, an arm <NUM>, and a work tool <NUM>. The boom <NUM> may be mounted on the body <NUM> at a pivot point <NUM>. The boom <NUM> is made to vertically pivot by means of a boom hydraulic cylinder <NUM>. A first end <NUM> of the boom hydraulic cylinder <NUM> may be coupled to the body <NUM>. A second end <NUM> of the boom hydraulic cylinder <NUM> may be coupled to the boom <NUM>. The boom <NUM> may be coupled to the arm <NUM>.

The arm <NUM> is moved with respect to the boom <NUM> by extending or retracting an arm hydraulic cylinder <NUM>. A first end <NUM> of the arm hydraulic cylinder <NUM> is coupled to the boom <NUM>. A second end <NUM> of the arm hydraulic cylinder <NUM> is coupled to the arm <NUM>. The arm <NUM> may further be coupled to the work tool <NUM>.

The work tool <NUM> is moved with respect to the arm <NUM> by extending or retracting a work tool hydraulic cylinder <NUM>. The work tool hydraulic cylinder <NUM> moves the work tool <NUM> via a bucket linkage assembly <NUM>. A first end <NUM> of the work tool hydraulic cylinder <NUM> may be coupled to the arm <NUM>. A second end <NUM> of the work tool hydraulic cylinder <NUM> is coupled to the bucket linkage assembly <NUM>. In an embodiment, the bucket linkage assembly <NUM> may be referred as a work tool linkage assembly and may be used to couple any type of work tool.

Numerous different work tools <NUM> may be attached to the excavator <NUM> and may be controlled by the machine operator. Work tool <NUM> may include any device used to perform a particular task, such as a blade, a fork arrangement, a bucket (shown in <FIG>), a shovel, a ripper, a broom, a propelling device, a cutting device, a grasping device, and/or any other task-performing device known in the art.

The upper structure <NUM> may use swing gear (generally placed around element <NUM>) to rotate with respect to lower structure <NUM> about an axis X. Further detail regarding the swing gear <NUM> is provided later herein. Available systems for determining the amount of this rotation (slew) may be imprecise or may require replacement of costly components such as the hydraulic swivel or swing motor. In available systems, Hall Effect sensors measure rotation of a swing gear pinion (not shown in <FIG>), and therefore precision is limited by the number of teeth on the swing gear pinion. To address these and other concerns, systems, apparatuses and methods according to some embodiments can provide a separate, nonmetallic pinion (e.g., a "follower pinion") that meshes with the swing gear and that follows rotation of the swing motor pinion, so that measurement precision is not limited by or dependent on the number of teeth on the swing gear pinion. Motion and position of this follower pinion can then be detected and used to determine cabin swing rotation. This assembly can be retrofitted to an existing machine. Description of the follower pinion assembly, and placement of the follower pinion assembly, is provided below.

<FIG> shows a perspective view of the excavator <NUM> in accordance with this disclosure. Certain elements of <FIG> were separately described with reference to <FIG> and are numbered similarly as <FIG> where appropriate. The perspective view is provided for depiction of center enclosure panel <NUM>. The follower pinion swing sensor location can be primarily identified when the center enclosure panel <NUM> is removed. The center enclosure panel <NUM> can be regularly accessed for service and installation of aftermarket sensing systems.

<FIG> shows a top view of an upper frame portion <NUM> of an excavator in accordance with this disclosure. The view depicts the upper frame portion <NUM> after the center enclosure panel <NUM> (<FIG>) has been removed. After removing the center enclosure panel <NUM>, the location <NUM> of a follower pinion swing sensor (or cover if the follower pinion swing sensor is not installed) can be seen under hydraulic hoses <NUM> routing toward a boom (e.g., boom <NUM> (<FIG>). Boom swing casting <NUM> can be located below pivot point <NUM> (<FIG>), e.g., between pivot point <NUM> and tracks <NUM>.

<FIG> shows a lower frame swivel access panel <NUM> of an excavator in accordance with this disclosure. Certain portions of the excavator <NUM> are the same as portions depicted and described with reference to <FIG> above and accordingly similar reference numerals as <FIG> may be used in <FIG>. As shown in <FIG>, a follower pinion swing sensor location can be discovered by removing the lower frame swivel access panel <NUM>. The lower frame swivel access panel <NUM> is less commonly removed than the panel <NUM> but does provide an additional access point that the follower pinion assembly could be discovered.

<FIG> shows a follower pinion apparatus <NUM> with the swivel access panel removed. Follower pinion <NUM> meshes with swing gear <NUM>. As described later herein, a sensor (not shown in <FIG>) detects motion of the follower pinion <NUM> and provides information on motion of the follower pinion to a controller, which deduces rotation of swing gear <NUM>.

<FIG> shows an upper frame portion <NUM> without sensor mounting provisions in accordance with this disclosure. The upper frame portion <NUM> can be similar to upper frame portion <NUM> (<FIG>). The upper frame portion <NUM> includes a swivel clearance aperture <NUM>. A swivel (not shown in <FIG>) comprises a fluid transfer mechanism that allows hydraulic oil to flow from the upper frame portion <NUM> to a lower frame (e.g., lower structure <NUM> (<FIG>). The top section <NUM> rotates relative to lower frame.

The upper frame portion <NUM> further includes a swing motor mounting aperture <NUM>. A swing motor (not shown in <FIG>) comprises a hydraulic mechanism that rotates the upper frame portion <NUM> about the lower frame (not shown in <FIG>). Swing gear/bearing mounting apertures <NUM> are also provided. A swing gear/bearing (not shown in <FIG>) provides a load carrying aspect of rotation and is provided with mounting apertures to both upper frame portion <NUM> and lower frame.

<FIG> shows an upper frame portion <NUM> with sensor mounting provisions in accordance with this disclosure. Features of <FIG> are as described with respect to similarly numbered features of <FIG>. The upper frame portion <NUM> can be similar to upper frame portion <NUM> (<FIG>). In comparison to <FIG>, the upper frame portion <NUM> further includes a follower pinion swing sensor mounting aperture <NUM>. Follower pinion sensor mounting aperture <NUM> comprises an additional machined aperture that meshes directly into the swing gear pitch center diameter (not visible in <FIG>). Currently available solutions provide an aperture similar to aperture <NUM> to provide access to Hall effect sensing solutions for sensing swing gear rotation. However, as mentioned earlier herein, Hall effect-based sensing solutions are less accurate and less precise than follower pinion-based solutions according to aspects of the disclosure.

Instead of measuring rotation of swing gear using Hall effect sensing solutions, systems, methods and apparatuses according to aspects of the disclosure kinematically compute the cabin swing rotation using a nonmetallic follower pinion that meshes with the swing gear and follows the rotation driven by the swing motor pinion.

<FIG> shows a follower pinion apparatus <NUM> in accordance with this disclosure. The follower pinion apparatus <NUM> includes a swing gear system comprised of a swing gear <NUM> and a swing motor pinion <NUM>. The follower pinion apparatus <NUM> further includes a follower pinion <NUM> that meshes with the swing gear <NUM>. The follower pinion <NUM> can be placed in the same locating diameter as the swing motor pinion <NUM> although embodiments are not limited thereto, and the follower pinion <NUM> and swing motor pinion <NUM> can have varying numbers of teeth. Further, similarly to the swing motor pinion <NUM>, the follower pinion can be designed as an involute gear design and having a same or lower backlash than the swing motor pinion <NUM>. In some examples, the swing gear <NUM> includes a pitch center diameter (not depicted in <FIG>) and the swing sensor aperture <NUM> (<FIG>) is positioned to mesh to the pitch center diameter.

The follower pinion apparatus <NUM> further includes a sensor <NUM> (<FIG>) configured to sense a position of a follower pinion <NUM>. As the follower pinion <NUM> follows the swing gear <NUM> (as shown with follower pinion <NUM> (<FIG>)), the sensor <NUM> can detect position of the follower pinion <NUM> and measurements therefore can be used to determine cabin swing rotation. Measurement can be continuous (as opposed to discrete) because the measurements do not rely on detection of a number of gear teeth but rather on the continuous rotation of the follower pinion <NUM> within the swing gear <NUM>. Furthermore, apparatuses according to embodiments can reduce or eliminate measurement errors that can occur due to misalignment of the swing gear <NUM> and can provide flexibility in mounting of the swing gear <NUM>.

<FIG> shows a cutout view of a follower pinion swing sensor assembly <NUM> in accordance with this disclosure. Referring to both <FIG> and <FIG>, sensor <NUM> reading is driven by pinion rotation of the follower pinion <NUM>, <NUM>, wherein the follower pinion <NUM>, <NUM> meshes with the teeth of the swing gear <NUM>. The sensor <NUM> can comprise a magnetic sensor, a contacting sensor, an encoder, or other type of sensor. Dimensions (e.g., the profile) of the follower pinion <NUM>, <NUM> can coincide with some dimensions of the swing motor pinion <NUM>.

The follower pinion <NUM>, <NUM> can comprise plastic or similar lightweight but durable material. The plastic can include, for example, nylon plastic, e.g., a Type <NUM> nylon thermoplastic containing molybdenum disulfide (MoS2), although embodiments are not limited to any particular type of plastic. The plastic material can be lightweight but durable to surrounding environment (dirt, grease, hydraulic oil) & continuous exposed temperatures. The plastic material can be available in rod extrusions allowing the material to be machined with sufficient precision to meet sensor alignment requirements and involute gear shape of the swing gear to prevent backlash. Using this nonmetallic material cuts down on cost (relative to machined steel) and eliminates any ferrous material interaction with the position sensor <NUM> that would present accuracy limitation.

The sensor <NUM> can be positioned outside the follower pinion housing <NUM> on an opposite side of the housing cover <NUM> from the follower pinion <NUM>. Dimensions (e.g., thickness) of the follower pinion housing <NUM> or other elements of <FIG> can be based on bearing size. A transitional fit condition may be present between one or more ball bearings <NUM> and the follower pinion housing <NUM>. The ball bearing/s <NUM> can be provided to allow the pinion <NUM> to rotate with swing gear <NUM> (<FIG>). A press-fit condition may exist between the ball bearing/s <NUM> and the pinion <NUM>. The follower pinion swing sensor assembly <NUM> can be mounted with the housing cover <NUM> using mechanisms such as bolts <NUM>, to the upper frame portion <NUM> (<FIG>) or <NUM> (<FIG>) at e.g., aperture <NUM> (<FIG>). Target (e.g., a magnetic target) <NUM> can mounted on a bolt (e.g., a stud bolt) <NUM> and within an inner diameter of the follower pinion <NUM> to be read by the position sensor <NUM>. Retaining rings <NUM> can be provided for further stability of the follower pinion swing sensor assembly <NUM>.

<FIG> is a flowchart depicting an example method <NUM> for sensing swing gear rotation in an excavator (e.g., work machine) <NUM> in accordance with this disclosure. The method <NUM> can be performed by elements of <FIG>, including in particular the follower pinion apparatus <NUM> and position sensor <NUM>.

The method <NUM> can begin with operation <NUM> with providing a follower pinion sensor housing including a follower pinion <NUM> and a position sensor <NUM>. The method <NUM> can continue with operation <NUM> with providing an aperture with an upper frame of the work machine, the aperture to mesh with a pitch center diameter of a swing gear system of the work machine.

The method <NUM> can continue with operation <NUM> with installing the follower pinion sensor housing in the aperture. A housing cover <NUM> can be mounted within the aperture and the position sensor <NUM> can be mounted to the housing cover <NUM>. The method <NUM> can continue operation <NUM> with detecting swing gear rotation based on a position of the follower pinion. The follower pinion <NUM>, <NUM> can be within a same locating diameter as a swing motor pinion <NUM> of the swing gear system.

In general, excavator <NUM> can be configured and equipped to detect rotation of a housing with a lower assembly of the excavator <NUM>. For example, a follower pinion <NUM> can be mounted within swing gear of the excavator <NUM>. The follower pinion <NUM> can mesh with this swing gear similar to the swing gear pinion such that the follower pinion moves with the swing gear. Therefore, by detecting the position of the follower pinion, swing gear position can be detected. Accuracy and precision are not limited by the number of teeth in the swing gear; instead, measurement is continuous throughout rotation of the swing gear.

Claim 1:
A positioning system comprising a swing gear system comprised of a swing gear (<NUM>; <NUM>) and a swing motor pinion (<NUM>);
the positioning system characterized by further comprising:
a nonmetallic follower pinion (<NUM>; <NUM>; <NUM>) positioned to mesh with the swing gear (<NUM>; <NUM>); and
a sensor (<NUM>) configured to sense a position of the follower pinion (<NUM>; <NUM>; <NUM>).