News Column

Patent Issued for Cam Driving Device and Processing Method

July 22, 2014



By a News Reporter-Staff News Editor at Information Technology Newsweekly -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Kume, Masao (Tochigi, JP); Takahashi, Keisuke (Tochigi, JP), filed on May 14, 2010, was published online on July 8, 2014.

The assignee for this patent, patent number 8770312, is Honda Motor Co., Ltd. (Tokyo, JP).

Reporters obtained the following quote from the background information supplied by the inventors: "The present invention relates to a cam driving device and a processing method, and particularly to a cam driving device and a processing method that are suitably used for a processing apparatus for processing the inner peripheral surface of a non-circular bore.

"It has been general in a manufacturing process of vehicles that a bore of a cylinder block of an engine is formed by a cutting work and then a cylinder head, a crank case, etc. are installed in the cylinder block. Furthermore, a piston is also mounted in the bore. When an actual engine is driven, fuel in the engine is combusted, and the piston is heated by combustion gas and expands. At this time, the shape of the piston approaches to a perfectly circular shape in section, and thus the piston has a substantially perfectly circular cross-section. Therefore, when the piston is installed in the bore of the cylinder block, the piston has an oval shape in which the major axis is slightly longer than the minor axis. In some cases, it is desired that the cross-sectional shape of the bore is a desired elliptical shape having an outward fixed clearance with respect to the outline of the cross-section of the piston. Therefore, it is desired to perform the cutting work so that the cross-sectional shape of the bore approaches to such a state that a fixed range of clearance is formed between the cross-section of the bore and the piston, and it is also desired that the bore has a substantially perfectly circular cross-section when the engine is driven after the engine is assembled.

"It has been hitherto difficult to process bores in a non-circular shape containing a desired elliptic shape at high speed, and thus bores have been hitherto processed in a substantially perfectly circular shape. Even when the bore of a cylinder block is processed to have a desired elliptical cross-section, the shape of the bore is deformed when a cylinder head, a crank case, etc. are assembled to the cylinder block. When the bore is deformed as described above, it increases the sliding resistance between the bore and the piston when the engine is used, and thus there is a risk that the engine cannot exercise desired performance.

"Therefore, in the process of processing the bore of the cylinder block, the bore processing is executed while a dummy head imitating the cylinder head is attached, and when the bore processing is finished, the dummy head is detached. However, when the attaching and detaching work of the dummy head, etc. is executed every time the processing of the bore of the cylinder block is executed, the productivity is greatly reduced.

"In order to solve this problem, the following method has been proposed (see JP-A-2007-313619). That is, a dummy head is mounted in the cylinder block, and a bore is processed to have a non-circular shape containing a desired elliptic shape in cross-section or an ideal circular shape containing a substantially perfectly circular shape in cross-section. Subsequently, the dummy head is detached from the cylinder block. At this time, stress caused by the mounting of the dummy head is released, and thus the shape of the bore is deformed and becomes a non-circular shape in cross-section. The overall shape of the bore having the non-circular cross-section is measured to generate NC data. Specifically, measurement points are set at predetermined intervals along the axial line of the bore which has been deformed to have a non-circular cross-section due to the detachment of the dummy head, and the cross-sectional shape of the bore at each measurement point is measured, thereby generating the NC data described above.

"Thereafter, boring processing is executed on a non-processed cylinder block on the basis of the generated NC data without mounting any dummy head to form a non-circular bore. According to this method, even in a case where the bore is processed without securing the dummy head to the cylinder block, the bore has a three-dimensional shape having a desired ideal elliptical cross-section when the cylinder is mounted.

"However, the deformation amount of the bore when the dummy head is detached from the cylinder block is not necessarily uniform, and thus the cross-sectional shapes of the bore at the respective measurement points are different from one another. Accordingly, in order to form a non-circular bore in the cylinder block, it is necessary to execute the cutting work corresponding to the cross-sectional shape at each of the measurement points along the axial line. The cutting work is executed while a cutting tool is projected to the inner peripheral surface of the bore. In order to process the bore so that the bore have different cross-sectional shapes at the respective measurement points, the projection amount of the cutting tool at each measurement point is required to be accurately set. When the control of the projection amount is not accurate, the cross-section of the bore does not have a desired ideal elliptical shape when the cylinder head is assembled to the cylinder block, and this causes increase of the sliding resistance between the bore and the piston when the engine is used."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "The present invention has been implemented in view of the foregoing problem, and has an object to provide a cam driving device and a processing method with which the inner peripheral surface of a non-circular bore can be processed with high precision.

"In order to attain the above object, according to a first aspect of the present invention, there is provided a cam driving device for a processing device including a cylindrical member (25), a rotational shaft (11, 12) that is provided in the cylindrical member and has a mount hole (111) formed on the outer peripheral surface thereof, a cam (121) provided to the rotational shaft, and a tool (13) that is mounted in the mount hole of the cylindrical member so that the tool can be protruded and retracted through the mount hole in a radial direction of the rotational shaft in accordance with a profile of the cam, the cylindrical member and the rotational shaft being axially reciprocated to process a non-circular bore, characterized by comprising: a storage unit (91) for storing a data table (90) representing associating relationship between a rotational angle of the cam and a protrusion amount of the tool which is provided on the basis of the rotational angle of the cam; and a controller (41) for advancing or retarding the rotational angle of the rotational shaft with respect to the cylindrical member according to the data table stored in the storage unit.

"According to the cam driving device, the cam is used as a mechanism of protruding the tool, and thus the construction can be facilitated. In addition, the data (data table) associating the rotational angle of the cam and the protrusion amount of the tool obtained on the basis of the rotational angle with each other is stored, and the rotational shaft is advanced or retarded in rotational angle with respect to the cylindrical member according to the data (data table) concerned. Therefore, the protrusion amount of the tool provided in the mount hole can be properly adjusted while the cam having any cam profile is used. Accordingly, the non-circular bore can be processed with high precision.

"Furthermore, in the above cam driving device, the rotational shaft comprises a first rotational shaft (11) and a second rotational shaft (12) provided in the first rotational shaft, the mount hole is formed on the outer periphery of the first rotational shaft, the cam is provided to the second rotational shaft, and the controller advances or retards the phase of the rotational angle of the second rotational shaft with respect to the phase of the rotational angle of the first rotational shaft according to the data table stored in the storage unit.

"According to the cam driving device, the cam is used as a mechanism of protruding the tool, and thus the construction can be facilitated. In addition, the data (data table) associating the rotational angle of the cam and the protrusion amount of the tool obtained on the basis of the rotational angle with each other is stored, and the phase of the second rotational shaft is advanced or retarded with respect to the phase of the first rotational shaft according to the data (data table) concerned. Therefore, the protrusion amount of the tool provided in the mount hole can be properly adjusted while the cam having any cam profile is used. Accordingly, the non-circular bore can be processed with high precision.

"The above cam driving device further may comprises a first rotation detecting unit (252) for detecting a rotational speed of the first rotational shaft, and a second rotation detecting unit (241) for detecting a rotational speed of the second rotational shaft, wherein the first and second rotational shafts are synchronized with each other in rotational speed, the rotational speed of the first rotational shaft is multiplied by the resolution of the second rotation detecting unit to obtain a first multiplication value, the rotational speed of the second rotational shaft is multiplied by the resolution of the first rotation detecting unit to obtain a second multiplication value, a speed error is calculated from the difference between both the first and second multiplication values, and the calculated speed error is added to an instruction value of the rotational speed of the first or second rotational shaft to control the rotation.

"According to the cam driving device, even when the resolution of the first rotation detecting unit is different from the resolution of the second rotation detecting unit, these resolutions can be matched with each other in consideration of the resolution ratio. The speed error is calculated on the basis of the difference between the rotational speeds of the first and second rotational shafts whose resolutions are matched with each other, whereby the speed error between the first and second rotational shafts can be accurately determined, and both the rotational shafts can be accurately synchronized with each other.

"In the above cam driving device, the cam may be designed in a perfectly circular shape. According to this construction, the manufacturing cost of the cam can be suppressed.

"According to a second aspect of the present invention, there is provided a method of processing a non-circular bore in a processing device including a first rotational shaft (11) having a mount hole (13) on the outer periphery thereof, a second rotational shaft (12) provided in the first rotational shaft, a cam (121) provided to the second rotational shaft, and a tool (13) mounted in the mount hole of the cylindrical member, comprising: protruding and retracting the tool through the mount hole in a radial direction of the first rotational shaft in accordance with a profile of the cam while the first and second rotational shafts are axially reciprocated; and advancing or retarding the phase of the rotational angle of the second rotational shaft with respect to the phase of the rotational angle of the first rotational shaft according to a data table (90) representing associating relationship between a rotational angle of the cam and a protrusion amount of the tool provided on the basis of the rotational angle of the cam.

"This processing method has the same effect as the cam driving device of this invention. That is, the cam is used as a mechanism of protruding the tool, and thus the construction can be facilitated. In addition, the data (data table) associating the rotational angle of the cam and the protrusion amount of the tool obtained on the basis of the rotational angle with each other is stored, and the rotational shaft is advanced or retarded in rotational angle with respect to the cylindrical member according to the data (data table) concerned. Therefore, the protrusion amount of the tool provided in the mount hole can be properly adjusted while the cam having any cam profile is used. Accordingly, the non-circular bore can be processed with high precision.

"In the above processing method, the non-circular bore may be processed on the basis of processing information for controlling the processing device when the tool is protruded from the mount hole to process the non-circular hole, and the processing information may be created on the basis of shape data obtained on the basis of a simulation in which under a condition that an assembly member is assembled to an assembly target member having a bore having a desired ideal cross-sectional shape, it is simulated how the bore is deformed and thus what shape the bore has after the assembly in a virtual space on a computer in a CAE system.

"According to this processing method, the shape data of the bore which has a desired ideal cross-sectional shape when the assembly member is assembled to the assembly target member can be obtained through the simulation with neither actually processing the bore having the desired ideal cross-sectional shape in the assembly target member to which the assembly member is assembled, nor measuring the shape of the bore after the assembly member is detached."

For more information, see this patent: Kume, Masao; Takahashi, Keisuke. Cam Driving Device and Processing Method. U.S. Patent Number 8770312, filed May 14, 2010, and published online on July 8, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8770312.PN.&OS=PN/8770312RS=PN/8770312

Keywords for this news article include: Honda Motor Co. Ltd., Information Technology, Information and Data Tabulation.

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Source: Information Technology Newsweekly


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