A method and device for online measurement of workpiece size

Abstract

The present invention discloses an online workpiece size measurement method and device, which belongs to the technical field of measuring devices characterized by mechanical technology. The device includes a feeding mechanism and an offset detection mechanism. The feeding mechanism is used to convey a crankshaft to a detection position of the offset detection mechanism; a second limiter is controlled to descend by a first linear drive. During the descent, a detection rod of a first displacement sensor is pressed against a major axis, and a second limiter is pressed against lugs on both sides of the crankshaft to achieve positioning of the crankshaft and prevent crankshaft deflection; the descent is continued until the first limiter is pressed against a minor axis, and the detection value of the first displacement sensor is recorded. The detection value is compared with a standard value of a calibration piece to calculate the surface offset and eccentricity of the crankshaft.

Description

Technical Field

[0001] The present invention relates to the technical field of measuring devices characterized by mechanical technology, and in particular to an online workpiece size measuring method and device. Background Art

[0002] The crankshaft is a critical component used in engines and other applications. It primarily consists of a short shaft and a long shaft, with eccentricity / offset between them. Traditionally, the method for detecting eccentricity in crankshafts relies on simple caliper inspections or spot checks, which is inconvenient and inefficient. Furthermore, the inspection process requires significant manpower, suffers from low accuracy, and is unable to achieve comprehensive inspections. This limits quality control and prevents online testing.

[0003] Therefore, it is necessary to design an online workpiece size measurement method that can realize unmanned and automated detection. Summary of the Invention

[0004] In response to the above-mentioned technical problems existing in the prior art, the present invention provides a method and device for online measurement of workpiece dimensions, which positions the crankshaft through multiple positioning mechanisms. After positioning, the displacement of the detection part is detected by a displacement sensor, and the eccentricity is detected by the displacement.

[0005] The present invention discloses an online workpiece size measuring device, comprising a feeding mechanism and an offset detection mechanism.

[0006] The feeding mechanism includes a feeding frame, and the feeding frame is provided with a V-shaped groove matching the crankshaft;

[0007] The offset detection mechanism includes a detection frame arranged on the upper side of the loading frame, and the detection frame is provided with a first linear drive.

[0008] A first slide is provided at the output end of the first linear actuator, and a first limiter and a first displacement sensor are provided on the lower side of the first slide;

[0009] The detection rod of the first displacement sensor is matched with the long axis of the crankshaft;

[0010] The first limiting member cooperates with the short shaft of the crankshaft.

[0011] Preferably, a second limiting member is further provided on the lower side of the first slide, and two second limiting members arranged at intervals cooperate with the lugs on both sides of the crank arm of the crankshaft;

[0012] A detection head is provided at one end of the detection rod of the first displacement sensor, and a first spring is provided on the outer side of the detection rod;

[0013] In the free state, the distance between the detection head and the long axis of the detection position crankshaft is smaller than the distance between the second limiter and the lug, and smaller than the distance between the first limiter and the short axis;

[0014] A verification piece is also included, wherein the outer diameter of the verification piece is the same as the diameter of the short shaft.

[0015] Preferably, it also includes a crankshaft lifting mechanism,

[0016] The crankshaft lifting mechanism includes a first lifting cylinder installed on one side of the loading rack, a positioning block is provided at the output end of the first lifting cylinder, and a positioning groove is provided at the upper end of the positioning block to match the short shaft of the crankshaft.

[0017] Preferably, it also includes an eccentric hole detection mechanism,

[0018] The eccentric hole detection mechanism includes a bracket arranged on one side of the loading rack,

[0019] The bracket is provided with a second linear drive, an output end of the second linear drive is provided with a second slide, and the detection slider is slidably mounted on the second slide;

[0020] The inner end of the detection slider is provided with a detection needle that matches the eccentric hole at one end of the short shaft, and the outer end is provided with a detection piece;

[0021] The second slide is provided with a proximity switch that cooperates with the detection element;

[0022] A second spring is provided between the detection slider and the second slide bracket.

[0023] Preferably, it also includes a diameter detection mechanism,

[0024] The diameter detection mechanism includes a pair of clamping jaws and a second displacement sensor;

[0025] The clamping jaws mate with the short or long axis of the crankshaft;

[0026] The second displacement sensor is arranged on one clamping jaw, and the detection end of the second displacement sensor extends toward the limit block on one side of the other clamping jaw.

[0027] Preferably, the feeding mechanism further comprises a second lifting cylinder, a third linear drive and a lifting frame movably mounted on the inner side of the feeding frame.

[0028] The second lifting cylinder is installed on the lower side of the loading rack, and a slider is provided at the output end of the second lifting cylinder;

[0029] A slide rail is provided on the lower side of the lifting frame, and the slider cooperates with the slide rail;

[0030] The third linear drive is installed on the lower side of the lifting frame, and the output end of the third linear drive is connected to the slider.

[0031] Preferably, the output end of the second lifting cylinder is provided with a lifting block, and the sliding block is fixed on the lifting block;

[0032] The output end of the third linear actuator is connected to the lifting block;

[0033] The second lifting cylinder is provided with a third displacement sensor, and the outer end of the detection rod of the third displacement sensor is installed on the lifting block or the sliding block.

[0034] Preferably, a feeding positioning mechanism is provided upstream of the feeding mechanism.

[0035] The loading and positioning mechanism includes a fourth cylinder and a fifth cylinder respectively arranged on both sides of the loading rack.

[0036] The output end of the fourth cylinder is provided with a pushing block, and the pushing block extends toward the V-shaped groove of the loading rack;

[0037] The output end of the fifth cylinder is provided with a U-shaped positioning block, and the bosses on both sides of the U-shaped positioning block match with the lugs of the crank arm.

[0038] The present invention also discloses a measurement method using the above-mentioned measuring device, comprising the following steps:

[0039] The crankshaft is transported to the inspection position through the loading mechanism;

[0040] Controlling the second limit member and the first displacement sensor to descend by the first linear drive;

[0041] During the descent, the detection rod of the first displacement sensor presses on the long axis;

[0042] Continue to descend until the first limit member presses the short shaft, and record the detection value of the first displacement sensor;

[0043] Obtaining a standard value of a first displacement sensor detecting a calibration piece, wherein the diameter of the calibration piece is the same as the minor axis;

[0044] The surface offset and eccentricity are obtained by the difference between the test value and the standard value.

[0045] Preferably, the eccentricity is calculated as follows:

[0046] (1);

[0047] (2);

[0048] Among them, L1 represents the detection value of the crankshaft, L0 represents the standard value of the calibration part, It is expressed as surface offset, b as major axis diameter, and a as minor axis diameter.

[0049] Compared with the prior art, the beneficial effects of the present invention are as follows: the loading mechanism is used to transport the crankshaft to the detection position of the offset detection mechanism; the second limit member is controlled to descend by the first linear drive, and during the descent, the detection rod of the first displacement sensor is pressed on the long axis, and the second limit member is pressed on the lugs on both sides of the crankshaft to achieve the positioning of the crankshaft and avoid crankshaft deflection; continue to descend until the first limit member is pressed on the short axis, record the detection value of the first displacement sensor, compare the detection value with the standard value of the calibration piece, and calculate the surface offset and eccentricity of the crankshaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a structural schematic diagram of the workpiece size online measuring device of the present invention;

[0051] Figure 2 It is a schematic diagram of the structure of the crankshaft;

[0052] Figure 3 It is a schematic diagram of the crankshaft positioning;

[0053] Figure 4 This is a schematic diagram of the installation of the detection head of the eccentricity detection mechanism;

[0054] Figure 5 It is a structural diagram of the feeding mechanism;

[0055] Figure 6 It is a structural diagram of the feeding positioning mechanism;

[0056] Figure 7 It is a plot showing the surface offset, major axis diameter, and minor axis diameter.

[0057] Mark in the figure: 1 rack,

[0058] 2 feeding mechanism, 21 feeding rack, 22 V-groove, 25 lifting rack, 26 slide rail, 27 third linear drive, 31 second lifting cylinder, 32 third displacement sensor, 33 lifting block, 35 slider,

[0059] 4 crankshaft, 41 short shaft, 42 crank arm, 43 lug, 44 long shaft, 45 eccentric hole,

[0060] 5 offset detection mechanism, 51 detection frame, 52 first linear drive, 521 first slide, 53 first limiter, 55 second limiter, 56 first displacement sensor, 57 first spring, 58 detection head,

[0061] 6 crankshaft lifting mechanism, 61 first lifting cylinder, 62 positioning groove, 63 positioning block,

[0062] 7 diameter detection mechanism, 71 clamping jaw, 73 second displacement sensor, 74 limit block,

[0063] 8 eccentric hole detection mechanism, 81 bracket, 82 second linear drive, 83 second slide, 85 detection needle, 86 proximity switch, 87 detection slider, 88 detection member, 89 second spring;

[0064] 9 feeding positioning mechanism, 91 fourth air cylinder, 92 pushing block, 95 fifth air cylinder, 96 U-shaped positioning block. DETAILED DESCRIPTION

[0065] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0066] Overview: As Figure 2 The crankshaft 4 includes a long shaft 44 and a short shaft 41 connected to both sides of a crank arm 42. A lug 43 is provided on the crank arm 42. When the lug 43 is horizontal, the long shaft 44 and the short shaft 41 are eccentric in the longitudinal direction, and the outer surfaces of the long shaft 44 and the short shaft 41 are offset. A hole is provided at one end of the short shaft 41, and an eccentric hole 45 is provided at one end of the long shaft 44.

[0067] The present invention is described in further detail below with reference to the accompanying drawings:

[0068] The first aspect of the present invention provides an online workpiece size measuring device, such as Figures 1-6 , including a feeding mechanism 2 and an offset detection mechanism 5 arranged on the frame 1, the feeding mechanism 2 includes a feeding frame 21, and the feeding frame 21 is provided with a V-shaped groove 22 that cooperates with the crankshaft 4; the offset detection mechanism 5 includes a detection frame 51 arranged on the upper side of the feeding frame, and a first linear drive 52 is provided on the detection frame 51, and the output end of the first linear drive 52 is provided with a first slide 521, and the lower side of the first slide 521 is provided with a second limit member 55 and a first displacement sensor 56; the two second limit members 55 arranged at intervals cooperate with the lugs 43 on both sides of the crank arm 42 of the crankshaft 4 to realize crankshaft positioning and avoid crankshaft deflection, and the detection rod of the first displacement sensor 56 cooperates with the long axis 44 of the crankshaft 4; the lower side of the first slide 521 is also provided with a first limit member 53 that cooperates with the short axis 41 of the crankshaft 4, for positioning the short axis 41.

[0069] The feeding mechanism is used to transport the crankshaft 4 to the detection position of the offset detection mechanism; the second limiter 55 is controlled to descend by the first linear drive 52. During the descent, the detection rod of the first displacement sensor 56 presses on the long shaft 44, and the second limiter presses on the lugs on both sides of the crankshaft to achieve the positioning of the crankshaft and prevent the crankshaft from deflecting; continue to descend, such as Figure 3 The first limit member 53 is pressed onto the short shaft 41, the detection value of the first displacement sensor 56 is recorded, the detection value is compared with the standard value of the calibration member, and the surface offset and eccentricity of the crankshaft are calculated.

[0070] The first displacement sensor 56 has a detection head 58 at one end of its detection rod, and a first spring 57 is disposed outside the detection rod. A third spring is disposed between the second stopper 55 and the first slide 521 to position the crankshaft and prevent deflection.

[0071] like Figure 4 In the free state / lifted state, the distance between the detection head 58 and the long axis 44 of the detection crankshaft 4 is smaller than the distance between the second limit member 55 and the lug 43, and smaller than the distance between the first limit member 53 and the short axis 41.

[0072] Figure 1 and Figure 4 Also shown are a crankshaft lifting mechanism 6 and an eccentric hole detection mechanism 8. The crankshaft lifting mechanism 6 includes a first lifting cylinder 61 mounted on one side of the loading rack 21. A positioning block 63 is provided at the output end of the first lifting cylinder 61. The upper end of the positioning block 63 is provided with a positioning groove 62 that mates with the short shaft 41 of the crankshaft 4. The positioning groove 62 mates with the short shaft 41 to adjust its height and, in conjunction with the V-groove on the long shaft, ensures that the crankshaft is in a horizontal position, thus avoiding detection errors caused by the V-groove 22. Figure 3 The crankshaft lifting mechanism 6 is removed.

[0073] The eccentric hole detection mechanism 8 includes a bracket 81 mounted on one side of the loading frame 21. A second linear actuator 82 is mounted on the bracket 81. A second slide 83 is mounted at the output end of the second linear actuator 82. A detection slider 87 is slidably mounted on the second slide 83. A detection needle 85 is mounted on the inner end of the detection slider 87, which engages with the eccentric hole 45 at one end of the short shaft 41, and a detection member 88 is mounted on the outer end. A proximity switch 86 is mounted on the second slide 83, which engages with the detection member 88. A second spring 89 is provided between the detection slider 87 and the second slide 83 to provide a buffer and reset function. The detection needle 85 is inserted into the eccentric hole by the second linear actuator 82. When the detection member 88 reaches a certain depth, the detection member 88 approaches the proximity switch 86, generating a detection signal, and the eccentric hole is deemed qualified. If the eccentric hole 45 is misaligned, the detection needle 85 cannot enter the eccentric hole and cannot detect the electrical signal from the proximity switch 86, resulting in the product being deemed unqualified.

[0074] Figure 1 、 Figure 2 and Figure 3 Diameter detection mechanism 7 is shown, comprising a pair of jaws 71 and a second displacement sensor 73. The jaws 71 engage with the minor axis 41 or major axis 44 of the crankshaft 4. The second displacement sensor 73 is mounted on one jaw 71, with its detection end extending toward a stopper 74 on one side of the other jaw 71. The diameter is determined to be acceptable by comparing the detection value of the second displacement sensor with a standard value. Figure 2 The diameter detection mechanism 7 is arranged on the minor axis side, but can also be arranged on the major axis side. The structures and functions of the two installation methods are the same or similar, and will not be described in detail in the present invention.

[0075] Figure 5 The second lifting cylinder 31, the third linear drive 27 and the lifting frame 25 movably installed on the inner side of the loading frame 21 of the loading mechanism 2 are shown. The second lifting cylinder 31 is installed on the lower side of the loading frame 21, and a slider 35 is provided at the output end of the second lifting cylinder 31; a slide rail 26 is provided on the lower side of the lifting frame 25, and the slider 35 cooperates with the slide rail; the third linear drive 27 is installed on the lower side of the lifting frame 25, and the output end of the third linear drive 27 is connected to the slider 35.

[0076] The second lifting cylinder 31 lifts the lifting frame 25 and the crankshaft, freeing the crankshaft 4 from the V-groove of the loading frame 21. The third linear actuator 27 propels the lifting frame 25 to the next station. The second lifting cylinder then lowers the lifting frame 25, allowing the crankshaft 4 to enter the V-groove 22 of the corresponding station, completing the movement and subsequent inspection of the crankshaft. After lowering, the third linear actuator 27 returns the lifting frame 25 to its original position. These steps are repeated to achieve automated loading and inspection of the crankshaft 4.

[0077] More specifically, the output end of the second lifting cylinder 31 is provided with a lifting block 33, and the slider 35 is fixed on the lifting block 33; the output end of the third linear drive 27 is connected to the lifting block 33; the second lifting cylinder 31 is provided with a third displacement sensor 32, and the outer end of the detection rod of the third displacement sensor 32 is installed on the lifting block 33 or the slider 35 to achieve stable translation and monitor the lifting height.

[0078] like Figure 6 The figure shows a feeding positioning mechanism 9 arranged upstream of the feeding mechanism 2.

[0079] The feeding positioning mechanism 9 includes a fourth cylinder 91 and a fifth cylinder 95 respectively arranged on both sides of the feeding rack 21. The output end of the fourth cylinder 91 is provided with a pushing block 92, and the pushing block 92 extends toward the V-groove 22 of the feeding rack, and is used to push the crank arm toward the feeding rack on one side; the output end of the fifth cylinder 95 is provided with a U-shaped positioning block 96, and the bosses on both sides of the U-shaped positioning block 96 cooperate with the lugs 43 of the crank arm 42 to adjust the position of the lugs and the flipping position of the crankshaft.

[0080] A second aspect of the present invention provides a detection method using an online workpiece size measurement device, comprising the following steps:

[0081] Step S1: The crankshaft is transported to the inspection position through the loading mechanism 2.

[0082] Step S2: controlling the second limiting member 55 and the first displacement sensor 56 to descend by the first linear driver 52 .

[0083] Step S3 : During the descending process, the detection rod of the first displacement sensor 56 presses on the long shaft 44 .

[0084] During descent, the first stopper 53 presses against the corresponding lug 43, positioning the axis. The third spring on the first stopper 53 provides cushioning and floating. After the detection rod presses against the long shaft 44, it generates relative displacement with the first displacement sensor 56, which generates an electrical signal and detection value based on the displacement.

[0085] Step S4 : Continue to descend until the first limit member 53 presses the short shaft 41 , stop descending and record the detection value L1 of the first displacement sensor 56 .

[0086] Step S5: Obtain the standard value L0 of the first displacement sensor 56 detecting the calibration piece.

[0087] The calibration piece has the same outer diameter as the short shaft 41 and is cylindrical or tubular. Replacing the crankshaft with the calibration piece will yield the standard value. The calibration piece is cylindrical or tubular, meaning it has equal major and minor axis diameters and a center distance of 0.

[0088] Step S6: Obtain the surface offset by the difference between the detected value and the standard value.

[0089] Step S7: Calculate the eccentricity of the crankshaft according to the surface offset, the major axis diameter and the minor axis diameter.

[0090] like Figure 7 , the eccentricity is calculated as:

[0091] (1);

[0092] (2);

[0093] Among them, L1 represents the detection value of the crankshaft, which is the reading of the first displacement sensor during the actual detection of the workpiece / crankshaft being tested. L0 represents the standard value of the calibration piece, which is the reading of the first displacement sensor when calibrating using the calibration piece. DL is expressed as surface offset, b as the major axis diameter, a as the minor axis diameter, and D as the eccentricity, which is the distance between the minor and major axes. The DL value is typically stored as a fixed parameter and only changes when recalibration is required.

[0094] The specific solution is as follows: Taking the upper end surface of the minor axis 41 as the reference M, the longitudinal distance between the center axis of the minor axis and the reference is: Ma / 2, and the longitudinal distance between the center axis of the major axis and the reference is: , the eccentricity D can be obtained by subtracting the two distances.

[0095] Step S8: Check whether the absolute value of the difference between the eccentricity and the standard value exceeds a first threshold.

[0096] If so, execute step S9: the crankshaft is unqualified and an alarm message is generated.

[0097] If not, execute step S10: the crankshaft is qualified, and the first linear driver 52 controls the second limiter 55 and the first displacement sensor 56 to move up and down, and execute step S1 until all crankshafts are tested.

[0098] The present invention detects the surface displacement of the upper end surface of the crankshaft (the surface where the short axis and the first limit member abut each other) through an offset detection mechanism, and calculates the eccentricity through the surface displacement, the diameters of the short axis and the long axis. This can realize automated detection and loading, improve detection efficiency, and achieve full-scale detection and online detection.

[0099] It can prevent unqualified products from flowing into the next process and provide data for the next process to improve accuracy. It can detect crankshafts of other types and specifications in the mixture and quickly identify workpieces during mixed production (measure standard-sized workpieces, obtain numerical values ​​and match them with the system to quickly determine which type of workpiece it is) to select the corresponding recipe.

[0100] In some of the processes described in the specification and claims of this application and the above-mentioned figures, multiple operations that appear in a specific order are included, but it should be clearly understood that these operations may not be executed in the order in which they appear in this document or may be executed in parallel. The serial numbers of the operations, such as 101, 102, etc., are only used to distinguish between different operations, and the serial numbers themselves do not represent any execution order. In addition, these processes may include more or fewer operations, and these operations may be executed in sequence or in parallel. It should be noted that the descriptions of "first", "second", etc. in this document are used to distinguish different messages, devices, modules, etc., and do not represent the order of precedence, nor do they limit "first" and "second" to different types.

[0101] It should be understood that terms such as "include" or "have" are intended to indicate the presence of features, numbers, steps, actions, components, parts, or a combination thereof disclosed in this specification, and do not exclude the possibility that one or more other features, numbers, steps, actions, components, parts, or a combination thereof exist or are added.

[0102] It should also be noted that, unless there is any conflict, the embodiments and features in the embodiments of the present disclosure may be combined with each other.

[0103] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A workpiece size online measuring device, characterized in that: It includes a feeding mechanism (2) and an offset detection mechanism (5), The feeding mechanism (2) comprises a feeding frame (21), and the feeding frame (21) is provided with a V-shaped groove (22) that matches the crankshaft (4); The offset detection mechanism (5) comprises a detection frame (51) arranged on the upper side of the loading frame, and a first linear drive (52) is arranged on the detection frame (51). The output end of the first linear drive (52) is provided with a first slide (521), and the lower side of the first slide (521) is provided with a first limit member (53) and a first displacement sensor (56); The detection rod of the first displacement sensor (56) is matched with the long axis (44) of the crankshaft (4); The first limiting member (53) cooperates with the short shaft (41) of the crankshaft (4); A second limiting member (55) is further provided on the lower side of the first slide (521), and two second limiting members (55) arranged at intervals cooperate with lugs (43) on both sides of the crank arm (42) of the crankshaft (4); A detection head (58) is provided at one end of a detection rod of the first displacement sensor (56), and a first spring (57) is provided on the outer side of the detection rod; In a free state, the distance between the detection head (58) and the major axis (44) of the detection position crankshaft (4) is smaller than the distance between the second limiting member (55) and the lug (43), and smaller than the distance between the first limiting member (53) and the minor axis (41); It also includes a calibration piece, the outer diameter of which is the same as the diameter of the short shaft (41); the calibration piece is a columnar or cylindrical piece; It also includes a crankshaft lifting mechanism (6), The crankshaft lifting mechanism (6) comprises a first lifting cylinder (61) mounted on one side of a loading rack (21); a positioning block (63) is provided at the output end of the first lifting cylinder (61); and a positioning groove (62) is provided at the upper end of the positioning block (63) for matching with the short shaft (41) of the crankshaft (4).

2. The workpiece size online measuring device according to claim 1, characterized in that: It also includes an eccentric hole detection mechanism (8), The eccentric hole detection mechanism (8) includes a bracket (81) arranged on one side of the loading rack (21), A second linear drive (82) is provided on the bracket (81), a second slide (83) is provided at the output end of the second linear drive (82), and a detection slider (87) is slidably mounted on the second slide (83); The inner end of the detection slider (87) is provided with a detection needle (85) that matches the eccentric hole (45) at one end of the short shaft (41), and the outer end is provided with a detection member (88); The second slide (83) is provided with a proximity switch (86) that cooperates with the detection member (88); A second spring (89) is provided between the detection slider (87) and the second slide (83).

3. The workpiece size online measuring device according to claim 1, characterized in that: It also includes a diameter detection mechanism (7), The diameter detection mechanism (7) includes a pair of clamping jaws (71) and a second displacement sensor (73); The clamping jaw (71) cooperates with the short shaft (41) or the long shaft (44) of the crankshaft (4); The second displacement sensor (73) is arranged on one clamping jaw (71), and a detection end of the second displacement sensor (73) extends toward a limit block (74) on one side of the other clamping jaw (71).

4. The workpiece size online measuring device according to claim 1, characterized in that: The feeding mechanism (2) further comprises a second lifting cylinder (31), a third linear drive (27) and a lifting frame (25) movably mounted on the inner side of the feeding frame (21). The second lifting cylinder (31) is installed on the lower side of the loading rack (21), and a slider (35) is provided at the output end of the second lifting cylinder (31); A slide rail (26) is provided on the lower side of the lifting frame (25), and the slider (35) cooperates with the slide rail; The third linear drive (27) is installed on the lower side of the lifting frame (25), and the output end of the third linear drive (27) is connected to the slider (35).

5. The workpiece size online measuring device according to claim 4, characterized in that: The output end of the second lifting cylinder (31) is provided with a lifting block (33), and the sliding block (35) is fixed on the lifting block (33); The output end of the third linear drive (27) is connected to the lifting block (33); The second lifting cylinder (31) is provided with a third displacement sensor (32), and the outer end of the detection rod of the third displacement sensor (32) is installed on the lifting block (33) or the sliding block (35).

6. The workpiece size online measuring device according to claim 5, characterized in that: A feeding positioning mechanism (9) is provided upstream of the feeding mechanism (2). The loading and positioning mechanism (9) comprises a fourth cylinder (91) and a fifth cylinder (95) respectively arranged on both sides of the loading rack (21). The output end of the fourth cylinder (91) is provided with a pushing block (92), and the pushing block (92) extends toward the V-shaped groove (22) of the loading rack; The output end of the fifth cylinder (95) is provided with a U-shaped positioning block (96), and the bosses on both sides of the U-shaped positioning block (96) match with the lugs (43) of the crank arm (42).

7. A method for online measurement of workpiece dimensions using the workpiece dimension online measurement device according to any one of claims 1 to 6, characterized in that: The following steps are involved: The crankshaft is transported to the inspection position through the loading mechanism; Controlling the second limit member and the first displacement sensor to descend by the first linear drive; During the descent, the detection rod of the first displacement sensor presses on the long axis; Continue to descend until the first limit member presses the short shaft, and record the detection value of the first displacement sensor; Obtaining a standard value of a first displacement sensor detecting a calibration piece, wherein the outer diameter of the calibration piece is the same as the short axis; The surface offset and eccentricity are obtained by the difference between the test value and the standard value; the eccentricity D is calculated as follows: （1）； （2）； Among them, L1 represents the detection value of the crankshaft, L0 represents the standard value of the calibration part, It is expressed as surface offset, b as major axis diameter, and a as minor axis diameter.

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