Abstract:
A system for inspecting thermal spray coated cylinder bores of aluminum alloy cylinder blocks, the system includes a failure detection apparatus, a heating apparatus, a cooling apparatus, and a control unit in electronic communication with each of the failure detection apparatus, the heating apparatus, and the cooling apparatus, and wherein the control unit includes a memory and a control logic sequence for operating the system.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to metal casting and more specifically to aluminum cylinder block castings having thermal spray bores and methods of manufacture. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0003]    A typical cast aluminum cylinder block includes a number of cylinders arranged in a number of configurations. The improvement achieved by using aluminum alloys for casting cylinder blocks includes a higher strength to weight ratio compared with grey iron or other ferrous based casting. However, whereas the cylinder bores of grey iron castings can simply be machined and honed before assembly, most aluminum alloy blocks utilize some type of cylinder bore liner. Some examples of cylinder bore liners include cast-in or press-in place iron or steel liners. Recent developments in cylinder bore liners include techniques known as thermal-sprayed cylinder bores involving plasma transferred liner material. However, unlike parent metal cylinder bores and press-in cylinder bore liners, thermal-sprayed cylinder bores are more susceptible to cracking and delamination causing engine failure. 
         [0004]    While the current engine block and cylinder bore design achieves the initial purpose, the design is susceptible to a specific type of failure in service which can result in a very costly repair. Accordingly, there is a need in the art for an inspection system to ensure initial reliability and long term robustness while maintaining design, cost, and weight improvements. 
       SUMMARY 
       [0005]    The present invention provides a system for inspecting thermal spray coated cylinder bores of aluminum alloy cylinder blocks. The system includes a failure detection apparatus, a heating apparatus, a cooling apparatus, and a control unit in electronic communication with each of the failure detection apparatus, the heating apparatus, and the cooling apparatus. The control unit includes a memory and a control logic sequence for operating the system. 
         [0006]    In another example of the present invention, the failure detection apparatus includes at least one acoustic detection device disposed in contact with the cylinder block proximate a first of the cylinder bores. 
         [0007]    In yet another example of the present invention, the failure detection apparatus includes one acoustic detection device for each of the cylinder bores of the cylinder block and the acoustic detection devices are mounted on a first fixture. 
         [0008]    In yet another example of the present invention, the heating apparatus includes one induction heating element for each of the cylinder bores of the cylinder block and the induction heating elements are mounted on a second fixture. 
         [0009]    In yet another example of the present invention, the heating apparatus further includes a temperature control and the heating apparatus is capable of heating the cylinder bores at a rate of 3° C./s to 50° C./s. 
         [0010]    In yet another example of the present invention, the heating apparatus further includes a surface temperature monitor and the surface temperature is controlled to not exceed a critical temperature of about 500° C. 
         [0011]    In yet another example of the present invention, the cooling apparatus includes one nozzle for each of the cylinder bores of the cylinder block, the nozzles are mounted on a third fixture, and the cooling apparatus provides a pressurized cooling medium to the nozzles. 
         [0012]    In yet another example of the present invention, the cooling apparatus further includes a storage tank and the cooling medium is one of compressed air, water, oil, gasses, and mixtures thereof. 
         [0013]    In yet another example of the present invention, the cooling apparatus is capable of cooling the cylinder bores of the cylinder block at a rate of between 10° C./s and 100° C./s. 
         [0014]    The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0015]      FIG. 1  is a schematic of a cylinder block cylinder bore inspection system in accordance with the present invention; 
           [0016]      FIG. 2  is a partial perspective view of an aluminum alloy cylinder block having thermal-spray cylinder bores, in accordance with the present invention; 
           [0017]      FIG. 3  is a cross sectional view of a cylinder bore wall including a thermal spray coating in accordance with the present invention; 
           [0018]      FIGS. 4 and 4A  are depictions of a failed thermal-spray cylinder bore in accordance with the present invention; 
           [0019]      FIGS. 5 and 5A  are depictions of a failed thermal-spray cylinder bore in accordance with the present invention; and 
           [0020]      FIG. 6  is a flowchart depicting a method of operating a cylinder block cylinder bore inspection system in accordance with the present invention. 
       
    
    
     DESCRIPTION 
       [0021]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0022]    With initial reference to  FIG. 1 , a cylinder block cylinder bore inspection system  10  is illustrated and will now be described. The cylinder block cylinder bore inspection system  10  is utilized as an inspection or gauging operation in a cylinder block manufacturing line. Regardless of precisely where the cylinder bore inspection system  10  is placed in the cylinder block manufacturing process, it is important to perform this inspection early in the process prior to performing too many operations and investing too much time on manufacturing the cylinder block. A cylinder bore that fails the inspection process most likely renders the cylinder block unusable without further off-line repairs. 
         [0023]    The cylinder bore inspection system  10  includes a processor or control unit  12 , a heating apparatus  14 , a cooling apparatus  16 , and a sensing apparatus  18 . A cylinder block  20  is the subject of the inspection. Generally speaking, cylinder blocks  20  are manufactured to provide for engine configurations of multiple shapes and sizes. In-line straight engines may include multiple cylinders with popular designs including engines having four, five, and six cylinders. In the example provided in  FIG. 1 , the cylinder block  20  includes four cylinder bores  22  aligned in an inline or straight formation such that each axis of the cylinder bores  22  are parallel to each other. Other configurations include 60° or 90° V-engine layouts having from 6 to 12 or even more cylinders. Still other configurations include flat or W layouts having a plurality of cylinders. Thus, the cylinder bore inspection system  10  can be configured to inspect any engine design layout regardless of the number of cylinders or arrangement without departing from the scope of the invention. A top end of each cylinder bore  22  terminates at the head deck  24  while the bottom end of each cylinder bore  22  terminates at the crankcase portion (not shown) of the cylinder block  20 . 
         [0024]    With a quick reference to  FIG. 2 , the arrangement of the cylinder bores  22  of the cylinder block  20  is explained in more detail. The cylinder bores  22  are arranged in a “Siamese” fashion. More specifically, each cylinder bore  22  shares a bore wall  26  with the adjacent cylinder bore  22 . The resulting structure thus provides that a portion of the internal cooling cavities or water jacket  28 , does not have any portion of the cooling cavity  28  between the cylinder bores  22 . The shared bore wall  26  allows for a more compact design and improves overall stiffness of the structure. 
         [0025]    Turning now to  FIG. 3  with continuing reference to  FIG. 2 , a cross section of a wall  46  of the cylinder bore wall  22  after processing through a thermal-spray operation is illustrated and will now be described. The cylinder bore wall  46  includes an inner surface or circumference  48  and an outer surface  50 . The outer surface  50  may be adjacent to a cavity utilized as water cooling passages or it may be utilized as a cylinder bore wall  46  of the adjacent cylinder bore  22 . In either aspect, the inner surface  48  of the cylinder bore wall  46  is exposed to a reciprocating piston (not shown) when in operation. The inner surface  48  of the cylinder bore wall  46  includes a coating  52  of material that is bonded to a parent material of the cylinder bore wall  46 . In some examples, the parent material of the cylinder bore wall  46  may be a cast iron alloy or an aluminum alloy. However, other types of alloys may be used without departing from the scope of the invention. The coating  52  is bonded to the parent material of the cylinder bore wall  46  using any one of a number of methods. One such method is a plasma transferred wire arc thermal spray apparatus as explained in U.S. Pat. No. 5,938,944. Other similar methods or variations of the disclosed methods may be used without departing from the scope of the invention. After the coating  42  is applied to the inner surface  48  of the cylinder bore wall  46 , an inner surface  54  of the coating  52  may be machined to achieve a precise fit with the piston and a prescribed surface finish or hone pattern. 
         [0026]    Returning now to  FIG. 1 , the heating apparatus  14  includes a fixture  30 , a plurality of induction heating elements  32 , and a temperature control mechanism  34 . More specifically, the plurality of heating elements  32  include as many individual heating elements as there are cylinder bores  22  in the cylinder block  20 . In this example, four individual heating elements  32  are mounted to the fixture  30  so that each of the four heating elements  32  can be inserted into a separate cylinder bore  20  by lowering the fixture  30  or raising the cylinder block  20 . The heating elements  32  are induction heating coils  32  capable of heating the cylinder bore  22  at a very rapid rate; from 3° C./s to 50° C./s. The rate of heating can be controlled to tailor the gauge to different cylinder block designs. The heating elements  32  may also include other types of mechanisms, for example, infrared heat lamps, without departing from the scope of the invention. The rapid heat rate creates a large temperature gradient as the surface of the cylinder bore  22  will be at a high temperature before the temperature of the internal material of the cylinder bore  22  starts to increase. Preferably, the surface temperature of the cylinder bore  22  reaches from 200° C. to 500° C. before the heating elements  32  are removed. The heating apparatus also includes a surface temperature monitor  35  for detecting the surface temperature of the cylinder bore  22 . The maximum temperature of the surface of the cylinder bore  22  is not to exceed about 500° C. Above this temperature, and the temperature is alloy dependent, the casting microstructure is subject to incipient melting. Thus, the expansion of the metal at the surface of the cylinder bore  22  is restrained by the internal metal of the cylinder bore  22  thus generating thermal stresses in the cylinder bores  22  that approach or exceed thermal stresses produced during operation of the engine in service. 
         [0027]    The cooling apparatus  16  is a mechanism for rapidly cooling the material of the cylinder bore  22 . The cooling apparatus  16  includes a fixture  36 , a plurality of nozzles  38 , a cooling medium  40 , and a delivery mechanism  39 , and depending upon the cooling medium  40  used, a storage tank  42  that is appropriate for that particular cooling medium  40 . The cooling apparatus  16  may use water, air, oil, or gases, such as nitrogen and argon, to remove heat from the surface of the cylinder bores  22 . In this example, four individual nozzles  38  are mounted to the fixture  36  so that each of the four nozzles  38  can be inserted into a separate cylinder bore  22  by lowering the fixture  36  or raising the cylinder block  20 . Once the nozzles  38  are in position, the cooling medium  40  is forced through the nozzles  38  onto the surface of the cylinder bores  22 . The target cooling rate for the surface of the cylinder bores  22  is between 10° C./s and 100° C./s. In one example of the present invention, the fixture  36  of the cooling apparatus  16  may be combined with the fixture  30  of the heating apparatus  14  to form a single fixture supporting each of the nozzles  38  of the cooling apparatus  16  and the heating elements  32  of the heating apparatus  14 . 
         [0028]    The acoustic sensor or transducer apparatus  18  functions to detect audible or vibration signals from the cylinder bores  22  that are produced when the thermal sprayed cylinder bores  22  fail during the thermal cycle testing. The detected failure includes one of the thermal sprayed coating cracking or th thermal sprayed coating delaminating from the substrate or cylinder bore  22  surface. The acoustic sensor apparatus  18  includes at least one acoustical sensor  42  supported by a fixture  44 . Prior to the heating apparatus  14  begins the heating process, the fixture  44  of the acoustic sensor apparatus  18  moves the acoustical sensor  42  into a detection position adjacent to the cylinder block  20 . In another example, the number of acoustical sensors  42  can match the number of cylinder bores  22  of the cylinder block  20  with each sensor  42  being placed proximate to one cylinder bore  22 . In this manner, the acoustic sensor apparatus  18  is capable of identifying which cylinder bore  22  has failed. 
         [0029]    The control unit  12  includes data acquisition and data processing capabilities and electronically communicates with the heating apparatus  14 , the cooling apparatus  16 , and the acoustic sensor or transducer apparatus  18 . The processor or control unit  12  generally includes an electronic control device having a preprogrammed digital computer or processor, control logic, memory used to store data, and at least one I/O peripheral. The control logic includes a plurality of logic routines for monitoring, manipulating, and generating data. The control logic may be implemented in hardware, software, or a combination of hardware and software. For example, control logic may be in the form of program code that is stored on the electronic memory storage and executable by the processor or control unit  12 . 
         [0030]    For example, a control logic or method  100 , shown in flowchart form in  FIG. 6 , is implemented in software program code that is executable by the processor or controller  12  and includes a first control logic  102  for starting the operation after the subject cylinder block is conveyed into position. A second control logic  104  translates the fixture  44  of the acoustic sensor apparatus  18  such that the acoustic sensors  42  are adjacent to or in contact with the corresponding cylinder bores  22  of the cylinder block  20 . A third control logic  106  begins the heating of the induction heating elements  32 . A fourth control logic  108  translates the fixture  30  of the heating apparatus  14  such that the induction heating elements  32  are inserted into the corresponding cylinder bores  22 . After a specified time period, a fifth control logic  110  retracts the fixture  30  of the heating apparatus  14  and translates the fixture  36  of the cooling apparatus  16  such that the nozzles  38  of the cooling apparatus  16  are inserted into the corresponding cylinder bores. A sixth control logic  112  initiates the flow of the cooling medium  40 . After a specified period of time, a seventh control logic  114  ends the flow of the cooling medium  40  and retracts the fixture  36  of the cooling apparatus  16 . An eighth control logic  116  checks for any failure signals received from the acoustic sensors  42  and reports a test failure or test pass to the operator. 
         [0031]    Referring now to  FIGS. 4, 4A, 5, and 5A , depictions of failed cylinder bore thermal spray coatings are illustrated and will now be described. For example,  FIG. 4  shows micrographs at 6000 μm and 200 μm scale of thermal spray coating delamination  56  and cracking  58  resulting from a failed engine test. In another instance,  FIG. 5  depicts an eight cylinder V configuration engine that failed engine testing due to delamination  56  and cracking  58 . 
         [0032]    While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and examples for practicing the invention within the scope of the appended claims.