CN101696870A - Parallelism measuring method and measuring apparatus of rear beam pipe of sedan car - Google Patents

Abstract

The invention relates to parallelism measuring method and measuring apparatus of a rear beam pipe, belonging to the technical field of measurement. the method comprises the following steps: determining coordinates of circle centers of an inner hole and an outer circle according to measuring points orthogonally arranged at the inside diameter and outside diameter of two ends of the rear beam pipe; determining a straight line according to the circle centers and working out the distances between the points and the straight line; and then, working out the parallelism of the rear beam pipe according to the distance calculations. The invention provides a parallelism measuring apparatus of the rear beam pipe on the basis of the method. The measuring method and the measuring apparatus can realize the high-precision and quick measurement of the rear beam pipe of a sedan car.

Description

Rear beam pipe of sedan car parallelism measurement method and measuring instrument

Technical field

The present invention relates to a kind of rear beam pipe of sedan car parallelism measurement method, relate to the cubing of using this measuring method simultaneously, belong to the detection technique field.

Background technology

Rear beam pipe is the vitals of rear axle, and it plays a part to connect wheel hub and supports vehicle body, and the quality of the depth of parallelism at rear beam pipe two ends is most important to the influence of rear axle part, therefore is necessary this workpiece is detected to control its quality.In the on-the-spot practical application, often use three coordinate measuring machine that the rear beam pipe depth of parallelism is detected, the time of needs about 5 minutes of every detection, length consuming time, the measuring process complexity, and this product generally requires every all to measure, the efficient of three coordinate measuring machine can not satisfy the production testing requirement.Still there be not at present the detection of better detection method and cubing realization to the rear beam pipe depth of parallelism.

Summary of the invention

The objective of the invention is in order to solve above-mentioned existing problem, design provides a kind of rear beam pipe of sedan car parallelism measurement method, and use this method and design measuring instrument, solve the problem that three coordinate measuring machine is consuming time, require great effort of using, realize rear beam pipe depth of parallelism high precision, the quick purpose of measuring.

The object of the present invention is achieved like this:

A kind of rear beam pipe of sedan car parallelism measurement method, by quadrature arrangement in left end cross section O ₁Interior measuring point P ₁, P ₂, P ₃, P ₄Determine O ₁Centre coordinate, by quadrature arrangement in left end cross section O ₂Interior measuring point P ₅, P ₆, P ₇, P ₈Determine O ₂Centre coordinate, by O ₁And O ₂Determine some X ₁By quadrature arrangement in right-hand member cross section O ₅Interior measuring point P ₁₇, P ₁₈, P ₁₉, P ₂₀Determine O ₅Centre coordinate, by quadrature arrangement in right-hand member cross section O ₆Interior measuring point P ₂₁, P ₂₂, P ₂₃, P ₂₄Determine O ₆Centre coordinate, by O ₅And O ₆Determine some X ₂By quadrature arrangement in left end cross section Y ₁Interior measuring point P ₉, P ₁₀, P ₁₁, P ₁₂Determine Y ₁Centre coordinate; By quadrature arrangement Z in the right-hand member cross section ₁Measuring point P ₁₃, P ₁₄, P ₁₅, P ₁₆Determine Z ₁Centre coordinate; Ask for a Y more respectively ₁, Z ₁To straight line X ₁X ₂Between distance, try to achieve the rear beam pipe depth of parallelism according to distance calculation then.

A kind of rear beam pipe of sedan car parallelism measuring instrument, the cubing stage body is placed on the table surface, a left side the 1st guide rail, a left side the 2nd guide rail and right the 1st guide rail, right the 2nd guide rail is packed in cubing stage body left and right sides sidepiece respectively accordingly, left skateboard, right slide plate is fitted in a left side the 1st guide rail respectively slidably, a left side the 2nd guide rail and right the 1st guide rail, on right the 2nd guide rail, left side V-type body, a left side the 1st handle, a left side the 2nd handle is packed on the left skateboard, right V-type body, right the 1st handle, right the 2nd handle is packed on the right slide plate left locking handle, right locking handle is contained in left skateboard respectively slidably, on the right slide plate; The left measuring head that left side measuring head core, left outer shield, left side protection tube constitute is packed on the left V-type body, the right measuring head that right measuring head core, right outer shield, right protection tube constitute is packed on the right V-type body, and workpiece for measurement is placed on left V-type locating piece, the right V-type locating piece; Column is packed in middle part, worktable side, and Computer Assisted Measurement System is installed on the column; Left side intermediate sleeve and left measuring head core, left skeleton closely cooperate and install, No. 1 sensor, No. 2 sensor, No. 3 sensor, be installed in left skeleton left part No. 4 sensor orthogonal packing, and be positioned at left outer shield, No. 5 sensor, No. 6 sensor, No. 7 sensor, be installed in left skeleton right part No. 8 sensor orthogonal packing, and be positioned at left outer shield, No. 9 sensor, No. 10 sensor, o.11 sensor, be installed on the left measuring head core No. 12 sensor orthogonal packing, and be positioned at left side protection tube; Left side shroud cover is packed in left outer shield end, and the left-hand cylinder lid is packed in protection tube end, a left side; Right intermediate sleeve closely cooperates and installs with right measuring head core, right skeleton, No. 13 sensor, No. 14 sensor, No. 15 sensor, is installed on the right measuring head core No. 16 sensor orthogonal packing, and is positioned at right protect tin; No. 21 sensor, No. 22 sensor, No. 23 sensor, be installed in right skeleton right part No. 24 sensor orthogonal packing, and be positioned at right outer shield, No. 17 sensor, No. 18 sensor, No. 19 sensor, be installed in right skeleton left part No. 20 sensor orthogonal packing, and be positioned at right outer shield; Right shroud cover is packed in right outer shield end, and right cover is packed in right protection tube end.

The invention has the advantages that, utilize rear beam pipe of sedan car parallelism measurement method and measuring instrument can realize the high precision of the rear beam pipe depth of parallelism, measure fast, easy to operate, the needs of high-precision rapid survey in being highly suitable for producing in enormous quantities.

Description of drawings

Fig. 1 is the technical requirement and the structural drawing of rear beam pipe of sedan car

Fig. 2 is the measuring point coordinate system synoptic diagram of rear beam pipe parallelism measurement method

Fig. 3 is a rear beam pipe parallelism measuring instrument structural representation

Fig. 4 is the vertical view of Fig. 3

Fig. 5 is the A-A cut-open view of Fig. 4

Fig. 6 is the C-C cut-open view of Fig. 5

Fig. 7 is the D-D cut-open view of Fig. 5

Fig. 8 is the B-B cut-open view of Fig. 4

Fig. 9 is the E-E cut-open view of Fig. 8

Figure 10 is the F-F cut-open view of Fig. 8

Piece number explanation among the figure:

1, worktable, 2, left V-type locating piece, 3, the cubing stage body, 4, a left side the 1st guide rail, 5, left skateboard, 6, left V-type body, 7, a left side the 1st handle, 8, left measuring head core, 9, left outer shield, 10, a left side the 2nd handle, 11, left side protection tube, 12, workpiece for measurement, 13, Computer Assisted Measurement System, 14, column, 15, right protection tube, 16, right the 1st handle, 17, right outer shield, 18, right measuring head core, 19, right the 2nd handle, 20, right V-type body, 21, right slide plate, 22, right the 1st guide rail, 23, right V-type locating piece;

24, a left side the 2nd guide rail, 25, right the 2nd guide rail, 26, right locking handle, 27, left locking handle;

28, No. 3 sensor, 29, No. 7 sensors, 30, the o.11 sensor, 31, left-hand cylinder lid, 32, No. 10 sensors, 33, No. 12 sensors, 34, left shroud cover, 35, No. 8 sensors, 36, No. 4 sensors, 37, left skeleton, 38, left intermediate sleeve, 39, No. 5 sensors, 40, No. 1 sensor, 41, No. 6 sensor, 42, No. 2 sensors, 43, No. 9 sensors;

44, No. 15 sensor, 45, No. 19 sensors, 46, No. 23 sensors, 47, right intermediate sleeve, 48, right skeleton, 49, No. 24 sensors, 50, No. 20 sensor, 51, right shroud cover, 52, No. 16 sensors, 53, No. 14 sensor, 54, right cover, 55, No. 22 sensors, 56, No. 18 sensor, 57, No. 21 sensor, 58, No. 17 sensors, 59, No. 13 sensors.

Embodiment:

Below in conjunction with accompanying drawing embodiment of the present invention is elaborated.

1 measuring principle

The depth of parallelism that accompanying drawing 1 requires can be regarded as some Y ₁, Y ₂Straight line with cross a some X ₁, X ₂The depth of parallelism of straight line, cross a some Z ₁, Z ₂Straight line with cross a some X ₁, X ₂The depth of parallelism of straight line.Wherein, X ₁Be to be positioned at some O ₁, O ₂Straight line on and apart from the point at 13mm place, crossbeam pipe left side, X ₂Be to be positioned at some O ₅, O ₆Straight line on and apart from the point at 13mm place, crossbeam pipe right side.Therefore, measure the depth of parallelism of rear beam pipe, can carry out according to the following steps:

1. with being arranged in O ₁The measuring point of 4 quadratures in the cross section is determined ⊙ O ₁Center of circle O ₁Coordinate, with being arranged in O ₂The measuring point of 4 quadratures in the cross section is determined ⊙ O ₂Center of circle O ₂Coordinate; Set up by center of circle O ₁With center of circle O ₂Straight-line equation, further can determine an X ₁Coordinate; X ₁With Y ₂Overlap, can determine Y ₂Coordinate;

2. with being arranged in O ₅The measuring point of 4 quadratures in the cross section is determined ⊙ O ₅Center of circle O ₅Coordinate, with being arranged in O ₆The measuring point of 4 quadratures in the cross section is determined ⊙ O ₆Center of circle O ₆Coordinate; Set up by center of circle O ₅With center of circle O ₆Straight-line equation, further can determine an X ₂Coordinate; X ₂With Z ₂Overlap, can determine Z ₂Coordinate;

3. with being arranged in O ₃The measuring point of 4 quadratures in the cross section is determined ⊙ O ₃Center of circle O ₃(Y ₁) coordinate;

4. with being arranged in O ₄The measuring point of 4 quadratures in the cross section is determined ⊙ O ₄Center of circle O ₄(Z ₁) coordinate;

5. set up X ₁, X ₂Straight line X ₁X ₂Equation;

6. calculation level Y ₁To straight line X ₁X ₂Vertical range δ ₁, if δ ₁=0, straight line Y then ₁Y ₂Be parallel to straight line X ₁X ₂Otherwise it is not parallel;

7. calculation level Z ₁To straight line X ₁X ₂Vertical range δ ₂, if δ ₂=0, straight line Z then ₁Z ₂Be parallel to straight line X ₁X ₂Otherwise it is not parallel.

The coordinate system of setting up according to foregoing is established X shown in Figure of description 2 ₁Be true origin.Measuring point P among Fig. 2 _iCorresponding to sensor T _i

For the rear beam pipe left side, Section is apart from the dark cross section ⊙ O of end face 5mm ₁4 measuring points of interior quadrature arrangement are used to measure cross section ⊙ O ₁Diameter and definite center of circle O ₁Coordinate;

Section is apart from the dark cross section ⊙ O of end face 48mm ₂4 measuring points of interior quadrature arrangement are used to measure cross section ⊙ O ₂Diameter and definite center of circle O ₂Coordinate; Then cross center of circle O ₁And O ₂The i.e. left side of straight line

The center line of section.

The cross section ⊙ O of section ₃4 measuring points of interior quadrature arrangement are used to measure cross section ⊙ O ₃Diameter and definite center of circle O ₃(Y ₁) coordinate.

For crossbeam pipe right side,

The cross section ⊙ O of part ₄4 measuring points of interior quadrature arrangement are used to measure cross section ⊙ O ₄Diameter and definite center of circle O ₄(Z ₁) coordinate.

Section is apart from the dark cross section ⊙ O of end face 48mm ₅4 measuring points of interior quadrature arrangement are used to measure cross section ⊙ O ₅Diameter and definite center of circle O ₅Coordinate;

Section is apart from the dark cross section ⊙ O of end face 5mm ₆4 measuring points of interior quadrature arrangement are used to measure cross section ⊙ O ₆Diameter and definite center of circle O ₆Coordinate; Then cross center of circle O ₅And O ₆Straight line be the right side The axis of section.

According to the measuring instrument of above-mentioned measuring method design shown in Figure of description 3.3 structures to 10 pairs of rear beam pipe parallelism measuring instruments of accompanying drawing describe in conjunction with the accompanying drawings, cubing stage body 3 is placed on worktable 1 table top, a left side the 1st guide rail 4, a left side the 2nd guide rail 24 and right the 1st guide rail 22, right the 2nd guide rail 25 is packed in cubing stage body 3 left and right sides sidepieces respectively accordingly, left skateboard 5, right slide plate 21 is fitted in a left side the 1st guide rail 4 respectively slidably, a left side the 2nd guide rail 24 and right the 1st guide rail 22, on right the 2nd guide rail 25, left side V-type body 6, a left side the 1st handle 7, a left side the 2nd handle 10 is packed on the left skateboard 5, right V-type body 20, right the 1st handle 16, right the 2nd handle 19 is packed on the right slide plate 21 left locking handle 27, right locking handle 26 is contained in left skateboard 5 respectively slidably, on the right slide plate 21; The left measuring head that left side measuring head core 8, left outer shield 9, left side protection tube 11 constitute is packed on the left V-type body 6, the right measuring head that right measuring head core 18, right outer shield 17, right protection tube 15 constitute is packed on the right V-type body 20, and workpiece for measurement 12 is placed on left V-type locating piece 2, the right V-type locating piece 23; Column 14 is packed in middle part, worktable 1 side, and Computer Assisted Measurement System 13 is installed on the column 14; Left side intermediate sleeve 38 and left measuring head core 8, left side skeleton 37 closely cooperates and installs, No. 1 sensor 40, No. 2 sensor 42, No. 3 sensor 28, be installed in left skeleton 37 left parts No. 4 sensor 36 orthogonal packings, and be positioned at left outer shield 9, No. 5 sensor 39, No. 6 sensor 41, No. 7 sensor 29, be installed in left skeleton 37 right parts No. 8 sensor 35 orthogonal packings, and be positioned at left outer shield 9, No. 9 sensor 43, No. 10 sensor 32, o.11 sensor 30, be installed on the left measuring head core 8 No. 12 sensor 33 orthogonal packings, and be positioned at left side protection tube 11; Left side shroud cover 34 is packed in left outer shield 9 ends, and left-hand cylinder lid 31 is packed in protection tube 11 ends, a left side; Right intermediate sleeve 47 closely cooperates and installs with right measuring head core 18, right skeleton 48, No. 13 sensor 59, No. 14 sensor 53, No. 15 sensor 44, be installed on the right measuring head core 18 No. 16 sensor 52 orthogonal packings, and be positioned at right protection tube 15; No. 21 sensor 57, No. 22 sensor 55, No. 23 sensor 46, be installed in right skeleton 48 right parts No. 24 sensor 49 orthogonal packings, and be positioned at right outer shield 17, No. 17 sensor 58, No. 18 sensor 56, No. 19 sensor 45, be installed in right skeleton 48 left parts No. 20 sensor 50 orthogonal packings, and be positioned at right outer shield 17; Right shroud cover 51 is packed in right outer shield 17 ends, and right cover 54 is packed in right protection tube 15 ends.

According to the above, can determine that in conjunction with the accompanying drawings the coordinate of each measuring point is listed in table 1.

Table 1 measuring point coordinate

Ri, ri ', Ri, Ri ' are the radius values of each cross section circle orthogonal directions in the table 1, and ti represents corresponding sensor T _iThe displacement variable that records.

Can determine the central coordinate of circle that each cross section is round by table 1, list in table 2.

Table 2 central coordinate of circle

1.1 determine some X ₁(Y ₂)

Cross some O ₁, O ₂Straight line O ₁O ₂Direction vector:

$\stackrel{\&OverBar;}{O_1{\mathrm{<figure-callout\; id="2"\; label="O"\; filenames="H200910073086XE0000012.png,H200910073086XE0000021.png"\; state="\{\{state\}\}">O</figure-callout>}}_2}=\left\{\begin{array}{c}((t06-t05)-(t02-t01))/2\\ ((t08-t07)-(t04-t03))/\mathrm{2,43}\end{array}\right\}---\left(1\right)$

Straight line O ₁O ₂Equation:

$\frac{x-(t02-t01)/2}{\left((t06-t05)\right)-(t02-t01)/2}=\frac{y-(t04-t03)/2}{(t08-t07)-(t04-t03)/2}=\frac{z-18}{43}---\left(2\right)$

Make the z=0 in the formula (2), can solve x=0.709 * (t02-t01)-0.209 * (t06-t05), y=0.709 * (t04-t03)-0.209 * (t08-t07).

Therefore put X ₁(Y ₂) coordinate be X ₁(Y ₂) (0.709 * (t02-t01)-0.209 * (t06-t05), 0.709 * (t04-t03)-0.209 * (t08-t07), 0).

1.2 determine some X ₂(Z ₂)

But invocation point X in like manner ₂(Z ₂) coordinate X ₂(Z ₂) (0.709 * (t18-t17)-0.209 * (t22-t21), 0.709 * (t20-t19)-0.209 * (t24-t23), 983).

1.3 set up straight line X ₁X ₂Equation

Straight line X ₁X ₂Direction vector:

$\stackrel{\&OverBar;}{X_1{\mathrm{<figure-callout\; id="2"\; label="X"\; filenames="H200910073086XE0000012.png,H200910073086XE0000021.png"\; state="\{\{state\}\}">X</figure-callout>}}_2}=\{p,q,r\}=\left\{\begin{array}{c}0.709\&times;((t10-t09)-(t04-t03))-\\ 0.209\&times;(t14-t13)-(t08-t07),\\ 0.709\&times;(t12-t11)-(t02-t01)-\\ 0.209\&times;((t16-t15)-(t06-t05)),983\end{array}\right\}---\left(3\right)$

Straight line X ₁X ₂Equation:

(x-x ₁)/p＝(y-y ₁)/q＝z/r (4)

1.4 some Y ₁To straight line X ₁X ₂Distance

$d_l=\frac{||\begin{array}{ccc}i& j& k\\ p& q& r\\ x_{Y_1}-x_1& y_{Y_1}-y_1& z_{Y_1}-z_1\end{array}||}{\sqrt{{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="H200910073086XE0000012.png,H200910073086XE0000021.png"\; state="\{\{state\}\}">p</figure-callout>}}^2+{\mathrm{<figure-callout\; id="2"\; label="q"\; filenames="H200910073086XE0000012.png,H200910073086XE0000021.png"\; state="\{\{state\}\}">q</figure-callout>}}^2+r^2}}---\left(5\right)$

1.5 some Z ₁To straight line X ₁X ₂Distance

$d_r=\frac{||\begin{array}{ccc}i& j& k\\ p& q& r\\ x_{Z_1}-x_2& y_{Z_1}-y_2& z_{Z_1}-z_2\end{array}||}{\sqrt{{\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="H200910073086XE0000012.png,H200910073086XE0000021.png"\; state="\{\{state\}\}">p</figure-callout>}}^2+{\mathrm{<figure-callout\; id="2"\; label="q"\; filenames="H200910073086XE0000012.png,H200910073086XE0000021.png"\; state="\{\{state\}\}">q</figure-callout>}}^2+r^2}}---\left(6\right)$

Bring each measuring point coordinate into formula (5), formula (6), write as the measurement equation according to the formula after the arrangement, the Survey Software of importing Computer Assisted Measurement System then gets final product.

2 error analyses

From the measuring process analysis of instrument as can be known, error is mainly derived from two links: the one, and the error that the calibrating of master body is introduced, the 2nd, the error that measuring instrument produces.

2.1 the error that master body is introduced

The error that master body is introduced mainly contains two.

1. master body is examined and determine the error of introducing

Master body must be examined and determine on large-scale metering type three coordinate measuring machine.

Here require calibrating to master body, must be corresponding with the measurement state of measuring instrument.Otherwise not only can't be used for the mismachining tolerance of master body is revised, nor can be used for calibration instrument.

The calibrating of the master body depth of parallelism will detect the centre coordinate that portals in the X and the Y direction in hole, and the master body parallelism error of examining and determine out is not more than 5 μ m, and the gauging error of the exemplar depth of parallelism that therefore settles the standard is

Δ ₁＝5μm

2. the exemplar material that calibrates for error of temperature introducing is bearing steel (GCr15), compares its temperature coefficient with workpiece material and is more or less the same.Again because they all are in the same environment, so the error that Yin Wendu causes can be ignored.

2.2 the error that sensor and signal processing module are introduced

The transducer range that uses in the measuring instrument is ± 200 μ m, sensor and signal processing module nonlinearity erron in ± 200 mu m ranges is very little, can reach ± 2 μ m/ ± 200 μ m, and stability is also fine, during measuring workpieces, the displacement of sensor is no more than 100 μ m, and parallelism measuring instrument uses is 12 A/D data collecting card, input voltage ± 2.5V, their common estimation of error of introducing are to the maximum

Δ ₂＝2μm

2.3 measuring error

Every error of the above analysis, the overall measurement error of measuring instrument should be the synthetic of every error.

When measuring the depth of parallelism, total error is

$\mathrm{\&Delta;}=\sqrt{{{\mathrm{\&Delta;}}_1}^2+{{\mathrm{\&Delta;}}_2}^2}\&ap;5.4\mathrm{\&mu;m}$

Every from the overall measurement error, the error that master body is introduced when measuring the depth of parallelism accounts for significant proportion.Therefore should improve the calibration accuracy of master body as far as possible.

Use the measurement result of rear beam pipe parallelism measuring instrument to list in table 3 with the measurement result of using three-dimensional.

The comparison of table 3 measurement result

From the comparison of table 3 measurement result as can be seen, use rear beam pipe parallelism measuring instrument and the measurement result basically identical that uses three-dimensional.

It is as follows to the detailed process of the depth of parallelism of common axis to measure the rear beam pipe two ends:

System school zero

Before measuring, at first will be with crossbeam pipe standards exemplar to the sensor on the measuring instrument measuring head to zero.Earlier system power supply is connected, entered zero interface, school behind the unlatching computing machine automatically.Hold a left side the 1st handle 7 or a left side the 2nd handle 10, right the 1st handle 16 or right the 2nd handle 19 measuring head is pulled to the worktable two ends, and left locking handle 27, right locking handle 26 rotated to the white marking angle, loose one's grip put down handle then measuring head be fixed on the worktable two ends, be positioned over master body on left V-type locating piece 2, the right V-type locating piece 23 this moment, then pull up the left locking handle 27 of left skateboard 5, allow the measuring head in left side advance with left skateboard 5, enter the measuring position, left side of master body pipe, stoped by its positive stop up to left skateboard; Pull up the right locking handle 26 of right slide plate 21 again, allow the measuring head on right side advance, enter the measuring position, right side of master body pipe, stoped by master body pipe end face up to right slide plate with slide plate.When be sure oing that left and right sides measuring head has been close to the both ends of the surface of master body pipe, carry out school zero, the initial value of computer recording sensor, promptly finish in school zero.

In general, every measuring workpieces is after two hours time, can be with master body to sensor to once zero.Gauge systems just can have been surveyed rear beam pipe after zero.

Measuring workpieces

After finished in gauge systems school zero, the comprehensive detection option of option program entered the comprehensive detection interface.

Measuring head is pulled to cubing stage body 3 two ends, and left locking handle 27, right locking handle 26 rotated to the white marking angle, loose one's grip put down handle then measuring head be fixed on cubing stage body 3 two ends, the master body riding position is taken down and be positioned over to master body from left V-type locating piece 2, right V-type locating piece 23.

Then workpiece to be measured (12) is positioned on left V-type locating piece 2, the right V-type locating piece 23.The red-label angle is extracted and rotated to left locking handle 27 put down, allow the measuring head in left side advance, enter the measuring position, left side of tested crossbeam pipe, stoped by its positive stop up to left skateboard with left skateboard (5).Pull up the right locking handle 26 of right slide plate (21) again, allow the measuring head on right side advance, enter the measuring position, right side of tested crossbeam pipe, stoped by crossbeam pipe end face up to right slide plate with slide plate.When be sure oing that left and right sides measuring head has been close to the both ends of the surface of tested crossbeam pipe, the computing machine interface displayed is the measurement result of this workpiece.Preserve data if desired, click in the dash number text box of the lower right corner of software interface, input Part No., or saving options by the F5 shortcut below the selection software interface can be preserved this time measurement data.The workpiece that to measure last time when surveying second moves down, and second is positioned on the V-type locating piece, and process is the same.

Claims (2)

1. rear beam pipe of sedan car parallelism measurement method is characterized in that: by quadrature arrangement in left end cross section O ₁Interior measuring point P ₁, P ₂, P ₃, P ₄Determine O ₁Centre coordinate, by quadrature arrangement in left end cross section O ₂Interior measuring point P ₅, P ₆, P ₇, P ₈Determine O ₂Centre coordinate, by O ₁And O ₂Determine some X ₁By quadrature arrangement in right-hand member cross section O ₅Interior measuring point P ₁₇, P ₁₈, P ₁₉, P ₂₀Determine O ₅Centre coordinate, by quadrature arrangement in right-hand member cross section O ₆Interior measuring point P ₂₁, P ₂₂, P ₂₃, P ₂₄Determine O ₆Centre coordinate, by O ₅And O ₆Determine some X ₂By quadrature arrangement in left end cross section Y ₁Interior measuring point P ₉, P ₁₀, P ₁₁, P ₁₂Determine Y ₁Centre coordinate; By quadrature arrangement Z in the right-hand member cross section ₁Measuring point P ₁₃, P ₁₄, P ₁₅, P ₁₆Determine Z ₁Centre coordinate; Ask for a Y more respectively ₁, Z ₁To straight line X ₁X ₂Between distance, try to achieve the rear beam pipe depth of parallelism according to distance calculation then.

2. rear beam pipe of sedan car parallelism measuring instrument of method according to claim 1, it is characterized in that: cubing stage body (3) is placed on worktable (1) table top, a left side the 1st guide rail (4), a left side the 2nd guide rail (24) and right the 1st guide rail (22), right the 2nd guide rail (25) is packed in cubing stage body (3) left and right sides sidepiece respectively accordingly, left skateboard (5), right slide plate (21) is fitted in a left side the 1st guide rail (4) respectively slidably, a left side the 2nd guide rail (24) and right the 1st guide rail (22), on right the 2nd guide rail (25), left side V-type body (6), a left side the 1st handle (7), a left side the 2nd handle (10) is packed on the left skateboard (5), right V-type body (20), right the 1st handle (16), right the 2nd handle (19) is packed on the right slide plate (21) left locking handle (27), right locking handle (26) is contained in left skateboard (5) respectively slidably, on the right slide plate (21); The left measuring head that left side measuring head core (8), left outer shield (9), left side protection tube (11) constitute is packed on the left V-type body (6), the right measuring head that right measuring head core (18), right outer shield (17), right protection tube (15) constitute is packed on the right V-type body (20), and workpiece for measurement (12) is placed on left V-type locating piece (2), the right V-type locating piece (23); Column (14) is packed in middle part, worktable (1) side, and Computer Assisted Measurement System (13) is installed on the column (14); Left side intermediate sleeve (38) and left measuring head core (8), left side skeleton (37) closely cooperates and installs, No. 1 sensor (40), No. 2 sensor (42), No. 3 sensor (28), be installed in left skeleton (37) left part No. 4 sensor (36) orthogonal packing, and be positioned at left outer shield (9), No. 5 sensor (39), No. 6 sensor (41), No. 7 sensor (29), be installed in left skeleton (37) right part No. 8 sensor (35) orthogonal packing, and be positioned at left outer shield (9), No. 9 sensor (43), No. 10 sensor (32), o.11 sensor (30), be installed on the left measuring head core (8) No. 12 sensor (33) orthogonal packing, and be positioned at left side protection tube (11); Left side shroud cover (34) is packed in left outer shield (9) end, and left-hand cylinder lid (31) is packed in protection tube (11) end, a left side; Right intermediate sleeve (47) closely cooperates and installs with right measuring head core (18), right skeleton (48), No. 13 sensor (59), No. 14 sensor (53), No. 15 sensor (44), be installed on the right measuring head core (18) No. 16 sensor (52) orthogonal packing, and be positioned at right protection tube (15); No. 21 sensor (57), No. 22 sensor (55), No. 23 sensor (46), be installed in right skeleton (48) right part No. 24 sensor (49) orthogonal packing, and be positioned at right outer shield (17), No. 17 sensor (58), No. 18 sensor (56), No. 19 sensor (45), be installed in right skeleton (48) left part No. 20 sensor (50) orthogonal packing, and be positioned at right outer shield (17); Right shroud cover (51) is packed in right outer shield (17) end, and right cover (54) is packed in right protection tube (15) end.

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