A connecting rod machining tool and a method of using the same

Abstract

The application provides a connecting rod machining tool and a using method thereof, which comprises a base, a first installation groove, a second installation groove and a sliding groove are arranged on the base, the center line of the first installation groove and the second installation groove is collinear with the center line of the sliding groove; a limiting block is fixed on the upper end surface of the base and located between the first installation groove and the second installation groove, a limiting groove is arranged on the upper end surface of the limiting block, and the center of the limiting groove is located on the center line of the first installation groove and the second installation groove; a first positioning core shaft is movably installed in the first installation groove; a second positioning core shaft is movably installed in the second installation groove, and the outer end surface of the second positioning core shaft is inclined to the center; and a process block is slidably installed in the sliding groove, and the end of the process block facing the second positioning core shaft is a circular arc surface matched with the second positioning core shaft. The application can solve the problems of complex machining process, low efficiency and difficult-to-ensure machining precision in the prior art.

Description

Technical Field

[0001] This invention relates to the field of connecting rod processing technology, specifically to a connecting rod processing fixture and its usage method. Background Technology

[0002] Connecting rods are the main force-transmitting components of diesel engines in internal combustion locomotives. The main and auxiliary connecting rod mechanism is one of the basic types commonly used in V-type diesel engines. Its structure is relatively special. The small ends of the main and auxiliary connecting rods are connected to the piston pins, the large end of the main connecting rod is mounted on the crankshaft, and the large end of the auxiliary connecting rod is hinged to the joint pin on the lug of the large end of the main connecting rod. One type of this hinge structure is the saddle-shaped structure, which is fixedly connected to the joint pin by two fastening bolts on both sides of the connecting rod body plate.

[0003] In traditional manufacturing processes, to produce a saddle-shaped connecting rod that meets the required specifications, multiple datum surfaces for positioning are typically pre-defined during the blanking stage. These datum surfaces are first machined using the rough boring as a reference, and then used as positioning references for the fine boring for further precision machining. While this method achieves a certain level of accuracy, it also has significant drawbacks: the process is complex and time-consuming, reducing production efficiency; it also places additional demands on the connecting rod design, limiting its flexibility. Furthermore, the need for multiple clamping and adjustments increases the risk of accumulated errors, posing a potential threat to product quality.

[0004] For saddle-shaped holes, the dimensional accuracy requirements are extremely stringent, with a diameter tolerance of only 0.01 mm. Furthermore, the hole is not a perfect circle but is specially designed according to specific needs. Traditional inspection methods mainly involve using coordinate measuring machines (CMMs) or standard gauge blocks for inspection, and then adjusting the boring bar size based on the inspection results to ensure the accuracy of the saddle-shaped hole. However, this method may result in slight deviations from the actual values, especially in cases of incomplete circumference. Additionally, it cannot adjust the boring bar size in real-time based on the inspection data, placing demands on the repeatability and precision of the boring bar.

[0005] In summary, existing technologies have the following problems when machining saddle-shaped connecting rods:

[0006] 1. An additional positioning reference surface needs to be set on the connecting rod blank surface to perform precision boring positioning, which is complicated and inefficient.

[0007] 2. The saddle hole size needs to be removed from the machining fixture before it can be inspected. It cannot be inspected and adjusted in real time during machining, making it difficult to guarantee machining accuracy. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a connecting rod machining fixture and its usage method, which can solve the problems of complex machining processes, low efficiency, and difficulty in guaranteeing machining accuracy in the prior art for connecting rods (especially saddle-shaped connecting rods).

[0009] To achieve the above and other objectives, the present invention is implemented through the following technical solution: As a first aspect, the present invention proposes a connecting rod processing fixture, including a base having a first mounting groove, a second mounting groove, and a sliding groove thereon, wherein the center line connecting the first mounting groove and the second mounting groove is collinear with the center line of the sliding groove; a limiting block, fixed on the upper end surface of the base, located between the first mounting groove and the second mounting groove, having a limiting groove on its upper end surface, the center of the limiting groove being located on the center line connecting the first mounting groove and the second mounting groove; a first positioning mandrel, movably installed in the first mounting groove; a second positioning mandrel, movably installed in the second mounting groove, the upper part of the outer end surface of the second positioning mandrel being inclined towards its center; and a process block, slidably installed in the sliding groove, the end of which facing the second positioning mandrel being an arc surface that mates with the second positioning mandrel.

[0010] The first and second positioning mandrels of this scheme adopt a lifting design. In the raised state, they are used for positioning, using the pin hole completed by rough boring in the previous process as the positioning reference to complete the reference transfer. The upper end of the outer end face of the second positioning mandrel is inclined to compensate for the center distance deviation of the large and small end holes of different connecting rods and the diameter deviation of the small end hole, thereby correcting the center line of the large and small end holes and achieving complete positioning of the connecting rod. In the lowered state, they are used for machining, avoiding interference between the boring tool and the positioning mandrel. Compared with the existing technology, it is not necessary to set an additional common reference positioning surface on the connecting rod blank surface, and the process reference is unified. The position of the process block can be adjusted according to the rough boring hole size. The process block and the saddle hole are machined together, solving the accuracy problem caused by uneven force during the machining of the saddle hole.

[0011] In one embodiment, the inclination angle of the upper part of the outer end face is less than 0.5°.

[0012] This design can meet the saddle hole positioning requirements of all saddle-shaped connecting rods on the market.

[0013] In one embodiment, the center holes of the first positioning mandrel and the second positioning mandrel are respectively provided with internal threads and lifting screws connected to the internal threads, and the external threads of the lifting screws are clearance-fitted with the internal threads.

[0014] The design allows for the stable lifting of the first and second positioning spindles by rotating the lifting screw clockwise; and after rotating the lifting screw counterclockwise, the first and second positioning spindles return to their original positions using their own weight. This design is convenient to operate and inexpensive.

[0015] In one embodiment, a first guide post and a second guide post are respectively provided in the first mounting groove and the second mounting groove, and guide holes are respectively provided outside the center holes of the first positioning mandrel and the second positioning mandrel; the first positioning mandrel and the second positioning mandrel are respectively fitted onto the first guide post and the second guide post.

[0016] The design of this scheme can provide guidance for the lifting and lowering of the first positioning mandrel and the second positioning mandrel.

[0017] In one embodiment, at least two of the first guide post and the second guide post are provided and arranged symmetrically.

[0018] The design of this scheme can ensure that the first or second positioning mandrel is subjected to uniform force during its ascent along the first or second guide post.

[0019] In one embodiment, a groove is provided on the sidewall of the first mounting groove and the second mounting groove, and a limiting component is provided on the outer end face of the first positioning mandrel and the second positioning mandrel respectively; when the limiting component is engaged in the groove, the first positioning mandrel and the second positioning mandrel are raised into position.

[0020] This design ensures that the first and second positioning mandrels can achieve precise positioning after rising to a specific position.

[0021] In one embodiment, the limiting component includes a positioning ball that engages with the groove and a spring that presses the positioning ball against the groove.

[0022] This design ensures that the first and second positioning mandrels can continue to rise or descend under their own weight after being subjected to force.

[0023] In one embodiment, the connecting rod machining fixture further includes a dial indicator, which is movably mounted on the base, for verifying whether the connecting rod is fully positioned after installation.

[0024] In one embodiment, a first scrap baffle and a second scrap baffle are respectively provided on the first mounting slot and the second mounting slot.

[0025] This design can prevent iron filings generated during processing from falling onto the first and second positioning mandrels, thus avoiding the iron filings from clogging the gap between the first and second positioning mandrels and the first mounting groove, and the gap between the second and third positioning mandrels and the second mounting groove, thereby affecting the lifting effect of the first and second positioning mandrels.

[0026] As a second aspect, the present invention also provides a method of using a connecting rod machining fixture, wherein the connecting rod is positioned and clamped using the connecting rod machining fixture as described in the first aspect for machining, including the steps of...

[0027] In the initial state of the connecting rod machining fixture, the first positioning mandrel and the second positioning mandrel are respectively raised to a specified height;

[0028] The large end hole of the connecting rod big end and the small end hole of the connecting rod small end are respectively fitted onto the first positioning mandrel and the second positioning mandrel, and the lower end face of the rod body abuts against the limiting block;

[0029] Move the dial indicator until the pointer touches the end face of the small end of the connecting rod;

[0030] Continue raising the second positioning spindle until the dial indicator reading begins to change, then stop raising the second positioning spindle.

[0031] Move the process block along the slide groove until it is close to the second positioning mandrel, with the lower end face of the process block being coplanar with the lower end face of the small end hole;

[0032] After fixing the connecting rod and the process block, the first positioning mandrel and the second positioning mandrel are lowered below the upper end surface of the base;

[0033] The large end hole and small end hole of the connecting rod are precision bored. After precision boring, the size of the process hole formed by the small end hole and the process block is directly checked and the boring tool size is adjusted to continue machining until the small end hole is qualified.

[0034] This design uses the rough boring hole as the positioning datum for fine boring, eliminating the need for additional positioning bosses on the connecting rod blank surface. Both the connecting rod bolt holes and fine boring holes are machined using the rough boring hole as the positioning datum, ensuring a unified process datum and resolving the perpendicularity issue between the fine boring hole and the bolt hole. The process block's position can be adjusted according to the rough boring hole size, and the process block is machined together with the saddle hole, resolving the accuracy issue caused by uneven force during saddle hole machining. Furthermore, the connecting rod can be inspected without being removed after the saddle hole is machined. The boring tool size can be adjusted based on the inspection results to continue machining, resolving the issue of dimensional defects caused by boring tool wear during batch machining of saddle holes.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows: the connecting rod machining tooling provided by the present invention has lower cost and wider applicability; the connecting rod blank does not need to be designed with a positioning boss, has good forging processability, and the finished product will not have a positioning boss left, which does not affect the final size of the product; the saddle hole machining dimensions are stable and can be directly detected by a gauge, which is simple to operate and has a wider applicability. Attached Figure Description

[0036] Figure 1 The diagram shown is a top view of a connecting rod machining fixture according to the present invention, in which a connecting rod is placed.

[0037] Figure 2 The image shown is a cross-sectional view of the connecting rod in the fully positioned state according to the present invention.

[0038] Figure 3 Displayed as Figure 2 Enlarged view of point A in the middle.

[0039] Figure 4 The diagram shown is a cross-sectional view of the invention in its initial state.

[0040] Figure 5 Displayed as Figure 4 Enlarged view of point B in the middle. Detailed Implementation

[0041] Please see Figures 1-5 The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0042] It should be noted that the structures, proportions, sizes, etc., illustrated in the accompanying drawings of this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0043] Unless otherwise defined, technical or scientific terms used herein should be understood in their ordinary sense as would be understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” etc., as used herein, are used to distinguish different objects, not to describe a particular order, quantity, or importance. Words such as “comprising” or “including” mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. The term “connection” as used herein, unless otherwise specified, includes both direct and indirect connections.

[0044] Example 1

[0045] like Figures 1-5 As shown, this embodiment provides a connecting rod machining fixture 100 for positioning and clamping the connecting rod 200 to facilitate rough boring, fine boring, and other machining operations on the connecting rod 200. In this embodiment, the connecting rod 200 is a saddle-shaped connecting rod, including a rod body 210, a small end 220 and a large end 230 connected to both ends of the rod body 210, respectively. The small end 220 is a non-circular structure. Specifically, the connecting rod machining fixture 100 includes a base 110, a limiting block 120, a first positioning mandrel 130, a second positioning mandrel 140, a process block 150, and a dial indicator 160.

[0046] The base 110 serves as a mounting base for positioning components such as the limiting block 120, the first positioning mandrel 130, the second positioning mandrel 140, the process block 150, and the dial indicator 160. Specifically, the base 110 has a first mounting groove 111, a second mounting groove 112, and a sliding groove 113. Both the first mounting groove 111 and the second mounting groove 112 are circular grooves, with the radius of the first mounting groove 111 being larger than the radius of the second mounting groove 112. These grooves are used to mount the first positioning mandrel 130 and the second positioning mandrel 140, respectively. The sliding groove 113 is positioned close to the end of the second mounting groove 112 away from the first mounting groove 111, and the center line connecting the first mounting groove 111 and the second mounting groove 112 is collinear with the center line of the sliding groove 113.

[0047] A limiting block 120 is disposed between the first mounting groove 111 and the second mounting groove 112, and can be fixed to the upper end face of the base 110 by screws for positioning the rod body 210. Specifically, the upper end face of the limiting block 120 is provided with a limiting groove 121 that matches the rod body 210. The center of the limiting groove 121 is located on the line connecting the centers of the first mounting groove 111 and the second mounting groove 112. Two limiting blocks 120 can be provided to ensure that the limiting blocks 120 can restrict the position of the rod body 210 and prevent the connecting rod 200 from rotating on the horizontal plane due to force during processing. After the rod body 210 is placed in the limiting groove 121, the fixing studs pre-installed on the base 110 can be used to clamp the rod body 210 onto the limiting block 120, thereby restricting the vertical displacement of the rod body 210.

[0048] The first positioning mandrel 130 is movably installed in the first mounting groove 111 and can be raised and lowered within the first mounting groove 111 to limit the position of the large end hole of the connecting rod 230. Specifically, the first positioning mandrel 130 is a cylinder, and its outer end face is clearance-fitted with the first mounting groove 111. The outer end face can also mate with the large end hole of the connecting rod 230 to prevent the connecting rod 200 from shifting horizontally due to force during processing. Further, in this embodiment, the center hole of the first positioning mandrel 130 is provided with an internal thread and a lifting screw 170 connected to the internal thread. The external thread of the lifting screw 170 is clearance-fitted with the internal thread, so that rotating the lifting screw 170 clockwise causes the thread to drive the first positioning mandrel 130 to rise within the first mounting groove 111; rotating the lifting screw 170 counterclockwise causes the first positioning mandrel 130 to descend and reset within the first mounting groove 111 under its own gravity. In other embodiments, the lifting and lowering of the first positioning spindle 130 can also be controlled by connecting a hydraulic cylinder to the first positioning spindle 130.

[0049] The second positioning mandrel 140 is movably mounted within the second mounting groove 112 and can be raised and lowered within the second mounting groove 112 to limit the small end hole of the connecting rod small end 220. Since the small end hole of the connecting rod small end 220 is not a complete circle, and during mass rough boring, the center distance and diameter of the small end holes of different connecting rods 200 will deviate. To compensate for these deviations, ensure the alignment of the center lines of the large and small end holes, and limit the rotation of the connecting rod 200, the second positioning mandrel 140 can be designed as a cylinder with a frustum upper section. That is, the upper section 141 of the outer end face of the second positioning mandrel 140 is inclined towards its center at an angle less than 0.5°, for example, 0.1°, 0.2°, and 0.3°. The lower section 142 of the outer end face of the second positioning mandrel 140 is a cylindrical surface that has a clearance fit with the second mounting groove 112, and the upper section 141 of the outer end face mates with the small end hole of the connecting rod small end 220. Furthermore, in this embodiment, the center hole of the second positioning mandrel 140 is provided with an internal thread and a lifting screw 170 connected to the internal thread. The external thread of the lifting screw 170 is clearance-fitted with the internal thread, so that by rotating the lifting screw 170 clockwise, the thread drives the second positioning mandrel 140 to rise in the second mounting groove 112; by rotating the lifting screw 170 counterclockwise, the second positioning mandrel 140 descends and resets in the second mounting groove 112 under its own gravity. In other embodiments, the raising and lowering of the second positioning mandrel 140 can also be controlled by connecting a hydraulic cylinder to the second positioning mandrel 140.

[0050] Furthermore, to improve the lifting stability of the first positioning spindle 130 and the second positioning spindle 140, a first guide post 181 and a second guide post 182 can be respectively provided in the first mounting groove 111 and the second mounting groove 112. Simultaneously, guide holes are respectively provided outside the central holes of the first positioning spindle 130 and the second positioning spindle 140. The outer end faces of the first guide post 181 and the second guide post 182 are cylindrical. The bottoms of the first guide post 181 and the second guide post 182 are respectively interference-fitted into the pin holes of the first mounting groove 111 and the second mounting groove 112. The first positioning spindle 130 and the second positioning spindle 140 are respectively fitted onto the first guide post 181 and the second guide post 182 through their respective guide holes. The first guide post 181 and the second guide post 182 are respectively clearance-fitted with the guide holes of the first positioning spindle 130 and the second positioning spindle 140. Two first guide posts 181 and two second guide posts 182 can be provided and arranged symmetrically to ensure that the first positioning mandrel 130 or the second positioning mandrel 140 is subjected to uniform force during the upward process along the first guide post 181 or the second guide post 182.

[0051] Furthermore, in some embodiments, in order to ensure that the first positioning mandrel 130 and the second positioning mandrel 140 can be accurately positioned after rising to a specific position, a groove can be provided on the side wall of the first mounting groove 111 and the second mounting groove 112 respectively, and a limiting component 190 can be provided on the outer end face of the first positioning mandrel 130 and the second positioning mandrel 140. The limiting component 190 includes a positioning ball that cooperates with the groove and a spring that presses the positioning ball into the groove. When the first positioning mandrel 130 and the second positioning mandrel 140 rise to the position of the groove in the first mounting groove 111 and the second mounting groove 112, the positioning ball is positioned and locked into the groove under the action of the spring preload.

[0052] The process block 150 is slidably installed in the slide groove 113 and can move along the slide groove 113. The end of the process block 150 facing the second positioning spindle 140 is an arc surface that can cooperate with the second positioning spindle 140. The process block 150 can be moved left and right manually, or it can be driven by a hydraulic cylinder, pneumatic cylinder or linear module. When the process block 150 moves to abut against the second positioning spindle 140, the process block 150 can be clamped onto the base 110 using a set of fixing studs pre-installed on the base 110.

[0053] The dial indicator 160 is mounted on the base 110 to check whether the connecting rod 200 is fully positioned after installation.

[0054] In addition, such as Figure 1 As shown, a first chip baffle 101 and a second chip baffle 102 can be respectively provided on the first mounting groove 111 and the second mounting groove 112 to prevent the chips generated during processing from falling on the first positioning spindle 130 and the second positioning spindle 140, and to avoid the chips blocking the gap between the first positioning spindle 130 / second positioning spindle 140 and the first mounting groove 111 / second mounting groove 112, thereby affecting the lifting effect of the first positioning spindle 130 and the second positioning spindle 140. Specifically, the first chip baffle 101 and the second chip baffle 102 are designed to be movable in a direction perpendicular to the rod body 210. Before the first positioning spindle 130 and the second positioning spindle 140 are raised to position the connecting rod 200, the first chip baffle 101 and the second chip baffle 102 are removed from the first mounting groove 111 and the second mounting groove 112. After the connecting rod 200 is positioned and the first positioning spindle 130 and the second positioning spindle 140 are lowered into the first mounting groove 111 and the second mounting groove 112, the first chip baffle 101 and the second chip baffle 102 are moved to completely cover the first mounting groove 111 and the second mounting groove 112 before precision boring is performed.

[0055] Example 2

[0056] This embodiment provides a method for using a connecting rod machining fixture. The connecting rod 200 is positioned and clamped using the connecting rod machining fixture 100 as described in Embodiment 1 to facilitate rough boring, fine boring, and other machining operations on the connecting rod 200. Specifically, this includes:

[0057] Step 1: In the initial state of the connecting rod machining fixture 100, raise the first positioning mandrel 130 and the second positioning mandrel 140 to the specified height respectively;

[0058] Specifically, the initial state of the connecting rod machining fixture 100 is such that the upper end faces of the first positioning mandrel 130 and the second positioning mandrel 140 are located below the upper end face of the base 110.

[0059] In this embodiment, "raising the first positioning spindle 130 and the second positioning spindle 140 to a specified height" specifically means: rotating the lifting screw 170 in the center hole of the first positioning spindle 130 and the second positioning spindle 140 clockwise, so that the first positioning spindle 130 rises along the first guide post 181 and the second positioning spindle 140 rises along the second guide post 182. After the limiting component 190 on the side wall of the first positioning spindle 130 is positioned and engaged in the side wall groove of the first mounting groove 111, the rotation of the lifting screw 170 in the center hole of the first positioning spindle 130 is stopped; after the limiting component 190 on the side wall of the second positioning spindle 140 is positioned and engaged in the side wall groove of the second mounting groove 112, the rotation of the lifting screw 170 in the center hole of the second positioning spindle 140 is stopped.

[0060] In other embodiments, the decision to raise the object to a specified height can be determined by the number of rotations, the height measured by a gauge, or other methods.

[0061] Step 2: Fit the large end hole of the connecting rod big end 230 and the small end hole of the connecting rod small end 220 onto the first positioning mandrel 130 and the second positioning mandrel 140 respectively, and let the lower end face of the rod body 210 abut against the limiting block 120.

[0062] At this time, since the upper part 141 of the outer end face of the second positioning spindle 140 is inclined toward its central hole, the second positioning spindle 140 is not raised to the position, and the connecting rod 200 is in an incompletely positioned state. The connecting rod 200 can rotate slightly on the limiting block 120 with the large end hole of the connecting rod large end 230 as the center.

[0063] Step 3: Move the dial indicator 160 until the pointer touches the end face of the small end 220 of the connecting rod. No need to record the reading.

[0064] Step 4: Continue to raise the second positioning spindle 140 until the reading of the dial indicator 160 begins to change, then stop raising the second positioning spindle 140.

[0065] Specifically, during the continued lifting of the second positioning spindle 140, the upper part 141 of the outer end face of the second positioning spindle 140 automatically corrects the center line connecting the large end hole of the connecting rod big end 230 and the small end hole of the connecting rod small end 220, and compensates for the center distance deviation of the large and small end holes and the diameter deviation of the small end hole of different connecting rods 200, until the reading of the dial indicator 160 begins to change and the lifting of the second positioning spindle 140 stops. At this time, the connecting rod 200 is in a fully positioned state.

[0066] Step 5: Move the process block 150 along the slide groove 113 until it is close to the second positioning mandrel 140. The lower end face of the process block 150 is coplanar with the lower end face of the small end hole of the connecting rod small end 220. At this time, the distance between the generatrix of the process block 150 and the generatrix of the small end hole of the connecting rod small end 220 is the rough boring size of the small end hole after compensation.

[0067] Step 6: Use the fixing bolt set to clamp and fix the connecting rod 200 and the process block 150;

[0068] Step 7: Lower the first positioning mandrel 130 and the second positioning mandrel 140 below the upper end surface of the base 110;

[0069] Specifically, in this embodiment, the first positioning spindle 130 and the second positioning spindle 140 are lowered by rotating the lifting screw 170 in the center hole of the first positioning spindle 130 and the second positioning spindle 140 counterclockwise.

[0070] Step 8: Precision boring of the large end hole and small end hole of connecting rod 200. After precision boring, the process hole composed of small end hole (saddle hole) and process block 150 can be directly inspected using a gauge. As the number of machining operations increases, the boring tool will wear. The boring tool size can be adjusted according to the real-time detected small end hole size to continue machining until the small end hole is machined to the qualified standard.

[0071] Step 9: Release the fixing bolts from the connecting rod 200 and the process block 150, remove the connecting rod 200, and move the process block 150 to its initial position.

[0072] Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial applicability. The above embodiments are merely illustrative of the principles and effects of this invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of this invention. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical concept disclosed in this invention should still be covered by the claims of this invention.

Claims

1. A tooling for machining connecting rods, characterized in that, include The base has a first mounting groove, a second mounting groove and a sliding groove, and the center line connecting the first mounting groove and the second mounting groove is collinear with the center line of the sliding groove. A limiting block is fixed on the upper surface of the base, located between the first mounting groove and the second mounting groove. A limiting groove is provided on its upper surface, and the center of the limiting groove is located on the line connecting the centers of the first mounting groove and the second mounting groove. The first positioning mandrel is movably installed in the first mounting slot; The second positioning mandrel is movably installed in the second mounting slot, and the upper part of the outer end face of the second positioning mandrel is inclined toward its center. The process block is slidably installed in the groove, and one end of it facing the second positioning mandrel is an arc surface that mates with the second positioning mandrel; The first positioning mandrel and the second positioning mandrel are respectively provided with internal threads and lifting screws connected to the internal threads in their central holes, and the external threads of the lifting screws are clearance-fitted with the internal threads. A groove is provided on the side wall of the first mounting groove and the second mounting groove respectively, and a limiting component is provided on the outer end face of the first positioning mandrel and the second positioning mandrel respectively; when the limiting component is engaged in the groove, the first positioning mandrel and the second positioning mandrel are raised to the position. A dial indicator, movably mounted on the base, is used to verify whether the connecting rod is fully positioned after installation.

2. The connecting rod machining fixture according to claim 1, characterized in that, The inclination angle of the upper part of the outer end face is less than 0.5°.

3. The connecting rod machining fixture according to claim 1, characterized in that, The first mounting groove and the second mounting groove are respectively provided with a first guide post and a second guide post, and the center holes of the first positioning mandrel and the second positioning mandrel are respectively provided with guide holes; the first positioning mandrel and the second positioning mandrel are respectively fitted onto the first guide post and the second guide post.

4. The connecting rod machining fixture according to claim 3, characterized in that, The first guide post and the second guide post are provided in at least two, and are arranged symmetrically.

5. The connecting rod machining fixture according to claim 1, characterized in that, The limiting component includes a positioning ball that mates with the groove and a spring that presses the positioning ball against the groove.

6. The connecting rod machining fixture according to claim 1, characterized in that, The first mounting slot and the second mounting slot are respectively provided with a first iron chip baffle and a second iron chip baffle.

7. A method of using a connecting rod machining fixture, characterized in that, Using the connecting rod machining fixture as described in any one of claims 1 to 6 to position and clamp the connecting rod for machining, including the steps of In the initial state of the connecting rod machining fixture, the first positioning mandrel and the second positioning mandrel are respectively raised to a specified height; The large end hole of the connecting rod big end and the small end hole of the connecting rod small end are respectively fitted onto the first positioning mandrel and the second positioning mandrel, and the lower end face of the rod body abuts against the limiting block; Move the dial indicator until the pointer touches the end face of the small end of the connecting rod; Continue raising the second positioning spindle until the dial indicator reading begins to change, then stop raising the second positioning spindle. Move the process block along the slide groove until it is close to the second positioning mandrel, with the lower end face of the process block being coplanar with the lower end face of the small end hole; After fixing the connecting rod and the process block, the first positioning mandrel and the second positioning mandrel are lowered below the upper end surface of the base; The large end hole and small end hole of the connecting rod are precision bored. After precision boring, the size of the process hole formed by the small end hole and the process block is directly checked and the boring tool size is adjusted to continue machining until the small end hole is qualified.

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