Gear grinding idle stroke eliminating method based on online measurement system

Abstract

The invention discloses a cut-in gear grinding idle stroke eliminating method based on an online measurement system. The cut-in gear grinding idle stroke eliminating method comprises an electromechanical device required by the method and specific implementation steps of the method. The electromechanical device is composed of a machine tool body (2), a machine tool X shaft (1), a machine tool Y shaft (5), a machine tool Z shaft (3), a machine tool rotary table C shaft (9), a grinding wheel spindle (6), a grinding wheel (7), a high-precision measuring head (4), an electrical device of the machine tool and a numerical control system. The method mainly comprises the specific implementation steps that a measuring head is used for measuring tooth groove coordinate points of a to-be-machined gear; transforming a tooth space coordinate; performing curve fitting on the coordinate points of the tooth socket; calculating the shortest distance between the grinding wheel and the tooth groove and determining the initial cutting point of the grinding wheel. The method is completely achieved based on an existing device of the machine tool, the achieving process is simple and easy to implement, human participation is not needed at all, and automatic machining of the machine tool can be achieved.

Description

Technical Field

[0001] The present invention belongs to the field of precision gear processing, and relates to an online measurement system, a fitting method for an actual tooth profile curve, a method for establishing a theoretical grinding wheel profile, and a method for accurately calculating a grinding wheel starting cutting point. Specifically, it relates to a method for reducing the idle stroke in a gear grinding process based on an online measurement system. Background Art

[0002] Before the start of the profile grinding process, in order to ensure that the grinding wheel does not collide with the gear when grinding begins or to avoid excessive grinding wheel feed, a certain safety distance is usually left between the grinding wheel and the gear. Before the grinding wheel contacts the workpiece for grinding, the feeding motion of the grinding wheel is also called the idle stroke. The time consumed by the idle stroke accounts for about 10%-20% of the total processing time, which greatly reduces the efficiency of the gear grinding process.

[0003] At present, the main method for eliminating backlash in grinding in China is to control the feed speed of the machine tool by using sensors to determine in real time whether the grinding wheel and the workpiece are in contact. However, this solution requires very high sensitivity of the sensor and is prone to problems such as tool collision and misjudgment of contact between the grinding wheel and the workpiece. Summary of the invention

[0004] The present invention aims to provide a method for reducing the idle stroke caused by the grinding wheel cutting into the tooth groove during the process of forming gear grinding. The method comprises an electromechanical device used in the method and the implementation steps of the method. The electromechanical device is composed of a machine tool bed (2), an X-axis (1) of the machine tool, a Y-axis (5) of the machine tool, a Z-axis (3) of the machine tool, a C-axis (9) of the machine tool turntable, a grinding wheel spindle (6), a grinding wheel (7), a high-precision probe (4), and an electrical device and a numerical control system of the machine tool. The implementation steps of the method mainly include three main contents: using the probe to measure the coordinate points of the tooth groove of the gear to be processed; tooth groove coordinate conversion; calculating the shortest distance between the grinding wheel and the tooth groove and determining the starting cutting point of the grinding wheel.

[0005] The technical solution of the present invention is:

[0006] 1. The present invention discloses a plunge-type gear grinding backlash elimination device based on an online measurement system, comprising a machine tool bed (2), an X-axis (1) of the machine tool, a Y-axis (5) of the machine tool, a Z-axis (3) of the machine tool, a turntable C-axis (9) of the machine tool, a grinding wheel spindle (6), a grinding wheel (7), and a high-precision probe (4) located near the grinding wheel spindle, and also comprises an electrical device and a numerical control system of the machine tool.

[0007] 2. A method of reducing idle travel in gear grinding according to the present invention:

[0008] a. First, use the probe to measure the coordinate points (X mn ,C mn-1 ) and (Xmn ,C mn-2 ), where m represents the mth tooth slot being measured, n represents the nth point in a tooth slot, 1 represents that the point is on the left side of the tooth slot, and 2 represents that the point is on the right side of the tooth slot. The specific operation is as follows:

[0009] a1. Install the gear (8) to be processed on the machine tool turntable (9), and adjust the position of the gear (8) until the rotation center of the gear and the rotation center of the turntable are on the same axis.

[0010] a2. Adjust the machine tool Y axis (5) until the line connecting the probe and the rotation center of the turntable is always parallel to the machine tool X axis (1).

[0011] a3. Adjust the rotation angle of the C-axis (9) of the machine tool rotary table until the probe can enter the vicinity of the center line of the tooth groove when feeding along the X-axis direction of the machine tool.

[0012] a4. Feed the probe along the X-axis direction of the machine tool to the top circle of the gear, rotate the C-axis of the turntable clockwise and counterclockwise until the probe contacts the tooth profile, take the rotation center of the gear as the coordinate origin, and record the coordinates of this pair of tooth profile points (X 11 , C 11-1 ) and (X 11 , C 11-2 ).

[0013] a5. Feed the probe a short distance along the X-axis direction, then rotate the turntable C-axis clockwise and counterclockwise until the probe contacts the tooth profile, and record the coordinates of the pair of tooth profile points (X 12 , C 12-1 ) and (X 12 , C 12-2 ).

[0014] a6. Repeat step a5 to measure and obtain the tooth profile point coordinates (X 1n , C 1n-1 ) and (X 1n , C 1n-2 ).

[0015] a7. Repeat the above steps to measure the coordinates of the tooth profile points (X mn , C mn-1 ) and (X mn , C mn-2 ).

[0016] b. All tooth profile coordinate points (X mn , C mn-1 ) and (X mn , C mn-2) is transformed into a rectangular coordinate system with the vertex at the center of the tooth groove as the origin; and the X axis (2) of the machine tool is the y axis of the rectangular coordinate system. The specific operation is as follows:

[0017] b1. Alignment: First, take all the coordinates of the first tooth groove (X 1n , C 1n-1 ) and (X 1n , C 1n-2 ), according to C mid =∑(C 1n-1 +C 1n-2 ) / (2·n) to calculate the C-axis centering value C of the tooth groove mid According to C′ 1n-1 =C 1n-1 -C mid , C′ 1n-2 =C 1n-2 -C mid Get the C-axis coordinates C′ on the left and right sides after centering 1n-1 and C′ 1n-2 The coordinate points of the remaining tooth grooves are based on C′ mn-1 =C mn-1 -C mid , C′ mn-2 =C mn-2 -C mid Get the C-axis coordinates C′ on the left and right sides after centering mn-1 and C′ mn-2 .

[0018] b2. Correction of coordinates: The purpose of correcting coordinates is to make all the measured tooth groove center lines coincide. The specific method is to find a positive integer n such that C′ mn-1 and C ′mn-2 satisfy and This is the coordinate of the C-axis after correction.

[0019] b3. Convert the polar coordinate point (X, C) into a rectangular coordinate point (x, y) according to the following formula. The C-axis coordinate is the corrected coordinate and

[0020] x=X·sinC

[0021] y=X·cosC-R f

[0022] c. Probe radius compensation, the specific steps are as follows:

[0023] c1. Import the tooth groove coordinate data into the data interpolation algorithm to obtain the fitting curve of the tooth shape before the probe radius compensation. The interpolation algorithm can be a polynomial interpolation or a spline interpolation method.

[0024] c2. Calculate the normal equation based on the fitting curve

[0025] c3. Offset each tooth groove coordinate point along the normal direction of the point by a probe radius distance to obtain the actual profile of the tooth groove.

[0026] d. Calculate the starting point of the grinding wheel. The specific steps are as follows:

[0027] d1. According to the following parametric equation, calculate the coordinates of a single tooth groove point m (x', y') and establish the theoretical profile of the grinding wheel. j , the root radius is R f , the base circle tooth angle is α. m is any point on the tooth involute, the vector radius of Om is r, and θ is the expansion angle of the involute.

[0028]

[0029] d2. Calculate the shortest distance d between the theoretical profile of the grinding wheel and the tooth profile fitting curve. Taking the horizontal coordinates on the top circles on both sides of the tooth groove as the interval, calculate the minimum value of the vertical coordinate y' of the grinding wheel profile and the vertical coordinate y of the fitting tooth groove profile point, d = min (y' (x) - y (x)).

[0030] d3. Determine the starting cutting point of the grinding wheel based on the shortest distance between the grinding wheel and the gear workpiece.

[0031] The beneficial effects of the present invention are:

[0032] The method of the present invention can effectively reduce radial idle travel.

[0033] The method of the present invention does not require human intervention during use, and the measurement, calculation, processing and other processes of the machine tool can be realized through G code programming, which can greatly save the preparation time before gear grinding.

[0034] The method for reducing idle travel in gear grinding processing of the present invention is not only applicable to gear grinding machine tools, but also applicable to large gear processing machine tools such as gear milling machines. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of the device of the present invention

[0036] Figure 2 This is a schematic diagram of the idle stroke of the gear grinding process of the present invention.

[0037] Figure 3 It is a schematic diagram for solving the theoretical profile of the grinding wheel.

[0038] Figure 4 This is a schematic diagram of the probe measuring the tooth groove coordinate points.

[0039] exist Figure 1 In the figure, 1 is the X-axis of the machine tool, 2 is the machine tool bed, 3 is the Z-axis of the machine tool, 4 is the probe, 5 is the Y-axis of the machine tool, 6 is the grinding wheel spindle, 7 is the grinding wheel, 8 is the gear, and 9 is the machine tool turntable.

[0040] exist Figure 3 In the figure, the base circle radius R j , the root radius is R f , the base circle tooth angle is α. m is any point on the involute, and r is the vector radius of Om. Specific implementation methods

[0042] The present invention will be further described below in conjunction with the accompanying drawings:

[0043] like Figure 1 The structure diagram of the device of the present invention is shown, and the device mainly includes a machine tool bed (2), an X-axis (1) of the machine tool, a Y-axis (5) of the machine tool, a Z-axis (3) of the machine tool, a C-axis (9) of the machine tool turntable, a grinding wheel spindle (6), a grinding wheel (7), and a high-precision probe (4) located near the grinding wheel spindle, and also includes an electrical device and a numerical control system of the machine tool. The gear (8) to be processed is located on the C-axis (9) of the machine tool turntable and rotates with the turntable. The high-precision probe (4) of the online measurement system is fixed on the machine tool bed (2), and each spindle and turntable of the machine tool are driven and controlled by the electrical device and the numerical control system of the machine tool. Figure 2 It shows two types of idle stroke in gear grinding. Type I represents the idle stroke before the grinding wheel cuts into the tooth groove and comes into contact with the gear for grinding; Type II represents the idle stroke generated from the time when the grinding wheel starts grinding from the starting cutting point until the grinding wheel comes into contact with each tooth groove during grinding. The method for eliminating idle stroke proposed in the present invention is for type I idle stroke. Figure 3 It is a schematic diagram for solving the theoretical profile of the grinding wheel. Figure 4 This is a schematic diagram of the probe measuring the tooth groove coordinate points.

[0044] The specific process of the method of the present invention is as follows:

[0045] a. First, use the probe to measure the coordinate points (X mn , C mn-1 ) and (X mn , C mn-2 ), where m represents the mth tooth slot being measured, n represents the nth point in a tooth slot, 1 represents that the point is on the left side of the tooth slot, and 2 represents that the point is on the right side of the tooth slot. The specific operation is as follows:

[0046] a1. Install the gear (8) to be processed on the machine tool turntable (9), and adjust the position of the gear (8) until the rotation center of the gear and the rotation center of the turntable are on the same axis.

[0047] a2. Adjust the machine tool Y axis (5) until the line connecting the probe and the rotation center of the turntable is always parallel to the machine tool X axis (1).

[0048] a3. Adjust the rotation angle of the C-axis (9) of the machine tool rotary table until the probe can enter the vicinity of the center line of the tooth groove when feeding along the X-axis direction of the machine tool.

[0049] a4. Feed the probe along the X-axis direction of the machine tool to the top circle of the gear, rotate the C-axis of the turntable clockwise and counterclockwise until the probe contacts the tooth profile, take the rotation center of the gear as the coordinate origin, and record the coordinates of this pair of tooth profile points (X 11 , C 11-1 ) and (X 11 , C 11-2 ).

[0050] a5. Feed the probe a short distance along the X-axis direction, then rotate the turntable C-axis clockwise and counterclockwise until the probe contacts the tooth profile, and record the coordinates of the pair of tooth profile points (X 12 , C 12-1 ) and (X 12 , C 12-2 ).

[0051] a6. Repeat step a5 to measure and obtain the tooth profile point coordinates (X 1n , C 1n-1 ) and (X 1n , C 1n-2 ).

[0052] a7. Repeat the above steps to measure the coordinates of the tooth profile points (X mn , C mn-1 ) and (X mn , C mn-2 ).

[0053] b. All tooth profile coordinate points (X mn , C mn-1 ) and (X mn , C mn-2 ) is transformed into a rectangular coordinate system with the vertex at the center of the tooth groove as the origin; and the X axis (2) of the machine tool is the y axis of the rectangular coordinate system. The specific operation is as follows:

[0054] b1. Alignment: First, take all the coordinates of the first tooth groove (X 1n , C 1n-1 ) and (X 1n , C 1n-2 ), according to Cmid =∑(C 1n-1 +C 1n-2 ) / (2·n) to calculate the C-axis centering value C of the tooth groove mid According to C′ 1n-1 =C 1n-1 -C mid , C′ 1n-2 =C 1n-2 -C mid Get the C-axis coordinates C′ on the left and right sides after centering 1n-1 and C′ 1n-2 The coordinate points of the remaining tooth grooves are based on C′ mn-1 =C mn-1 -C mid , C′ mn-2 =C mn-2 -C mid Get the C-axis coordinates C′ on the left and right sides after centering mn-1 and C′ mn-2 .

[0055] b2. Correction of coordinates: The purpose of correcting coordinates is to make all the measured tooth groove center lines coincide. The specific method is to find a positive integer n such that C′ mn-1 and C′ mn-2 satisfy and This is the coordinate of the C-axis after correction.

[0056] b3. Convert the polar coordinate point (X, C) into a rectangular coordinate point (x, y) according to the following formula. The C-axis coordinate is the corrected coordinate and

[0057] x=X·sinC

[0058] y=X·cosC-R f

[0059] c. Probe radius compensation, the specific steps are as follows:

[0060] c1. Import the tooth groove coordinate data into the data interpolation algorithm to obtain the fitting curve of the tooth shape before the probe radius compensation. The interpolation algorithm can be a polynomial interpolation or a spline interpolation method.

[0061] c2. Calculate the normal equation based on the fitting curve

[0062] c3. Offset each tooth groove coordinate point along the normal direction of the point by a probe radius distance to obtain the actual profile of the tooth groove.

[0063] d. Calculate the starting point of the grinding wheel. The specific steps are as follows:

[0064] d1. According to the following parametric equation, calculate the coordinates of a single tooth groove point m (x', y') and establish the theoretical profile of the grinding wheel. j , the root radius is R f , the base circle tooth angle is α. m is any point on the tooth involute, the vector radius of Om is r, and θ is the expansion angle of the involute.

[0065]

[0066] d2. Calculate the shortest distance d between the theoretical profile of the grinding wheel and the tooth profile fitting curve. Taking the horizontal coordinates on the top circles on both sides of the tooth groove as the interval, calculate the minimum value of the vertical coordinate y' of the grinding wheel profile and the vertical coordinate y of the fitting tooth groove profile point, d = min (y' (x) - y (x)).

[0067] d3. Determine the starting cutting point of the grinding wheel based on the shortest distance between the grinding wheel and the gear workpiece.

Claims

1. A plunge-type gear grinding and backlash elimination device based on an online measurement system, characterized in that The invention comprises a machine tool bed (2), an X-axis (1), a Y-axis (5), a Z-axis (3), a turntable (9), a grinding wheel spindle (6), a grinding wheel (7), and a high-precision probe (4) located near the grinding wheel spindle, as well as an electrical device and a numerical control system of the machine tool. The gear (8) to be processed is located on the C-axis (9) of the machine tool turntable and rotates with the turntable. The high-precision probe (4) of the online measurement system is fixed on the machine tool bed (2), and the spindles and the turntable of the machine tool are driven and controlled by the electrical device and the numerical control system of the machine tool.

2. A method for eliminating backlash by cutting-in type gear grinding based on an online measurement system, characterized in that: a. Use the probe to measure the coordinate points (X mn , C mn-1 ) and (X mn , C mn-2 ), where m represents the mth tooth slot being measured, n represents the nth point in a tooth slot, 1 represents that the point is on the left side of the tooth slot, and 2 represents that the point is on the right side of the tooth slot (e.g. (X 12 , C 12-1 ) represents the second point of the first tooth groove on the left). The specific operation of measurement is as follows: a1. Install the gear (8) to be processed on the machine tool turntable (9), and adjust the position of the gear (8) until the rotation center of the gear and the rotation center of the turntable are on the same axis. a2. Adjust the machine tool Y axis (5) until the line connecting the probe and the rotation center of the turntable is always parallel to the machine tool X axis (1). a3. Adjust the rotation angle of the C-axis (9) of the machine tool rotary table until the probe can enter the vicinity of the center line of the tooth groove when feeding along the X-axis direction of the machine tool. a4. Feed the probe along the X-axis direction of the machine tool to the top circle of the gear, rotate the C-axis of the turntable clockwise and counterclockwise until the probe contacts the tooth profile, take the rotation center of the gear as the coordinate origin, and record the coordinates of this pair of tooth profile points (X 11 , C 11-1 ) and (X 11 , C 11-2 ). a5. Feed the probe a short distance along the X-axis direction, then rotate the turntable C-axis clockwise and counterclockwise until the probe contacts the tooth profile, and record the coordinates of the pair of tooth profile points (X 12 , C 12-1 ) and (X 12 , C 12-2 ). a6. Repeat step a5 to measure and obtain the tooth profile point coordinates (X 1n , C 1n-1 ) and (X 1n , C 1n-2 ). a7. Repeat the above steps to measure the coordinates of the tooth profile points (X mn , C mn-1 ) and (X mn , C mn-2 ). b. Include all tooth profile coordinate points (X mn , C m-1 ) and (X mn , C mn-2 ) is transformed into a rectangular coordinate system with the vertex at the center of the tooth groove as the origin; and the X-axis (2) of the machine tool is the y-axis of the rectangular coordinate system: b1. Alignment: First, take all the coordinates of the first tooth groove (X 1n , C 1n-1 ) and (X 1n , C 1n-2 ), according to C mid =∑(C 1n-1 +C 1n-2 ) / (2·n) to calculate the C-axis centering value C of the tooth groove mid According to C′ 1n-1 =C 1n-1 -C mid , C′ 1n-2 =C 1n-2 -C mid Get the C-axis coordinates C′ on the left and right sides after centering 1n-1 and C′ 1n-2 The coordinate points of the remaining tooth grooves are based on C′ mn-1 =C mn-1 -C mid , C′ mn-2 =C mn-2 -C mid Get the C-axis coordinates C′ on the left and right sides after centering mn-1 and C′ mn-2 . b2. Correction of coordinates: The purpose of correcting coordinates is to make all the measured tooth groove center lines coincide. The specific method is to find a positive integer n such that C′ mn-1 and C′ mn-2 satisfy and This is the coordinate of the C-axis after correction. b3. Convert the polar coordinate point (X, C) into a rectangular coordinate point (x, y) according to the following formula. The C-axis coordinate is the corrected coordinate and x=X·sinC y=X·cosC-R f c.Including probe radius compensation algorithm c1. Import the tooth groove coordinate data into the data interpolation algorithm to obtain the fitting curve of the tooth shape before the probe radius compensation. The interpolation algorithm can be a polynomial interpolation or a spline interpolation method. c2. Calculate the normal equation based on the fitting curve c3. Offset each tooth groove coordinate point along the normal direction of the point by a probe radius distance to obtain the actual profile of the tooth groove. d. Including the steps of finding the starting cutting point of the grinding wheel: d1. According to the following parametric equation, calculate the coordinates of a single tooth groove point m (x', y') and establish the theoretical profile of the grinding wheel. j , the root circle radius is R f , the base circle tooth angle is α. m is any point on the tooth involute, the vector radius of Om is r, and θ is the expansion angle of the involute. d2. Calculate the shortest distance d between the theoretical profile of the grinding wheel and the tooth profile fitting curve. Taking the horizontal coordinates on the top circles on both sides of the tooth groove as the interval, calculate the minimum value of the vertical coordinate y' of the grinding wheel profile and the vertical coordinate y of the fitting tooth groove profile point, d = min (y' (x) - y (x)). d3. Determine the starting cutting point of the grinding wheel based on the shortest distance between the grinding wheel and the gear workpiece.

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