CN103954447B - A kind of cutting error measurement method of harmonic speed reducer flexible gear - Google Patents

Abstract

The invention relates to a flexible gear for a harmonic reducer, in particular to a cutting error measurement method for a flexible gear for a harmonic reducer. The laser probe emits two parallel laser beams with a certain distance, and shoots them on different tooth surfaces respectively, and then the probe outputs the distances measured by each. If over-cut or under-cut occurs, the tooth thickness will inevitably change, resulting in a change in the output signal of the probe. The cutting error caused by the cutting depth of the gear hobbing machine and tool wear can be calculated from the difference in the output signal. For gears, measure its full teeth to reduce the positioning error caused by adjusting the relative position of the gear and the probe, and meet the requirements of manufacturing quality control.

Description

A Cutting Error Measurement Method of Flexible Gear Used in Harmonic Reducer

technical field

The invention relates to a flexible gear for a harmonic reducer, which measures the cutting error of the tooth profile through a laser probe and a rotating measuring platform system; in order to reduce the inconvenience caused by the micrometer and the Kuven line in the traditional measurement method to the measurement process and the damage to the measurement result The error of the present invention proposes a cutting error measurement method of the flexible gear used in the harmonic reducer, which belongs to the precision manufacturing technology of advanced equipment.

Background technique

The main structure of the harmonic reducer is a harmonic generator, a flexible external gear and a rigid internal gear. The harmonic reducer has a high deceleration rate and almost no tooth backlash. It is featured in high positioning accuracy, good repeatability, high torque, high efficiency and low wear in industrial robots, machine tools, and medical equipment. and spacecraft are widely used. Since it is mostly used in the precision manufacturing industry, the dimensional tolerance requirements of harmonic reducer parts are becoming more and more stringent. Therefore, in order to ensure the manufacturing accuracy of its parts, it is necessary to accurately measure the cutting error of the parts and feed back the error information to the machine tool at the same time. Thereby controlling the manufacturing precision. However, for the harmonic reducer, it is particularly difficult to control the manufacturing accuracy of the flexible gear, and its cutting accuracy is only about a few microns, which will greatly affect the performance of the harmonic reducer. Generally, the measurement of the cutting error of flexible gears is realized by measuring a system consisting of flexible gears, Fan Kuven lines and micrometers. Insert the wire between two adjacent teeth, press the wire with a micrometer and measure the diameter of the addendum circle at this time. If overcut occurs during cutting, the distance between two adjacent teeth will increase, and the Van Kuven wire will Moving towards the center of the gear, the cutting error of the flexible gear can be obtained by comparing the measured data obtained by this method with the reference data. But the actual operation is very difficult, because the gear size is very small and has good elasticity, and the cutting must be stopped during the measurement, which makes the whole measurement process unstable, inefficient and difficult to guarantee accurate data. Based on the fact that the size of the gear is too small to measure, and the dimensional accuracy and measurement efficiency must be ensured, the patent of this invention proposes a measurement system using two laser probes and a rotating measuring table to measure the cutting error of the flexible gear in a non-contact and inelastic manner. The deformation measurement method can effectively improve the measurement accuracy and measurement efficiency.

Contents of the invention

The measurement system for the cutting error of the flexible gear used in the harmonic reducer involved in the patent of the present invention is composed of two parallel laser probes and a rotating measuring table. The respective measured distances are output by the probes. If overcut or undercut occurs, the tooth thickness will inevitably change, resulting in a change in the output signal of the probe. The cutting error caused by the cutting depth of the gear hobbing machine and tool wear can be calculated from the difference in the output signal. At the same time, the positioning error caused by adjusting the relative position of the gear and the probe can be reduced by rotating the gear and measuring its entire tooth, so as to meet the requirements of manufacturing quality control.

Description of drawings

Figure 1 Schematic diagram of the measurement system;

1-laser probe; 2-flexible gear; 3-rotary measuring table.

Figure 2 Schematic diagram of reference gear calibration measurement;

m ₁₀ - the distance measured by laser probe ₁ ; m ₂₀ - the distance measured by laser probe 2; θ _i - the angle of gear rotation; m _A the distance from the probe to the pitch circle; The passing angle; D-distance between two laser probes.

Figure 3 is a schematic diagram of the measurement of the gear to be tested;

m ₁ - the distance measured by laser probe 1; m ₂ - the distance measured by laser probe 2; m _B - the distance when the distances measured by the two probes are equal; θ _B - the distance turned when the distances measured by the two probes are equal Angle; Δα-cutting error.

Figure 4 is a schematic diagram of the measurement difference between the two probes in one revolution.

Fig. 5 is a schematic diagram of the measured average value Δm _ave of each gear after multi-turn measurement.

detailed description

(1) As shown in the schematic diagram of the measurement system in Figure 1, the flexible gear is fixedly installed on the rotating measuring platform by using a static pressure cylindrical fixture, and the measuring platform is driven by a stepping motor; then two laser probes are fixed in parallel at the same height as the gear, and the laser The probe adopts LC-2420 laser displacement sensor with a resolution of 10nm; the two displacement sensors are connected to the computer through the AD module for data collection and calculation.

(2) Before the actual measurement, first select the flexible external tooth gear in Figure 2 as the reference gear for calibration measurement; adjust the distance between the two parallel probes so that the two measurement points of the laser on the tooth surface are located on the pitch circle of the gear , so that the small-scale measurement area around the measurement point can be regarded as a straight line; as shown in Figure 2, when measuring the two teeth of the reference gear, as the gear rotates clockwise, m ₁₀ gradually decreases, and m ₂₀ Gradually increase, when the two are equal after turning θ _A , it is the distance from the two probes to the pitch circle, and at this time the two measurement points are located on the pitch circle.

The reference gear refers to a flexible gear whose cutting error meets the error range, and the cutting error of the gear is regarded as 0;

The error range generally refers to the relevant national standards for gear precision, and the specific error range depends on the actual processing technical requirements.

(3) After replacing the gear to be measured, turn the gear to measure. The relationship between the rotation angle and the measurement distance obtained at this time is shown in Figure 3. m _B is the equal distance measured by the two probes, and the reference gear In comparison, the error Δα between m _A and m _B is the cutting error; however, the cutting errors shown in Figure 2 and Figure 3 are all theoretical values obtained without considering the gear eccentric error, rotation error and other errors. Obtaining the actual precise error needs to take external influence factors into account.

The gear to be measured and the reference gear should be of the same kind.

(4) Data collection and calculation: The measuring platform is driven by a stepping motor and collects data once per revolution, so the collected data appears in a discrete form, and the error can be calculated more accurately through calculation, and the XY coordinates are established in the horizontal plane The Y axis is parallel to the laser. It can be seen from Fig. 3 that when the distance measured by the laser probe 2 (i.e. m ₂ ) is equal to mA, the measurement result of the laser probe _{1 can be expressed by mA + 2Δα, then m 1 and m 2} can be expressed for

m ₁ ＝m _A +2Δα+{e _C cosθ _i +e _X (θ _i )}tanφ ₁ (θ _i )+e _C sinθ _i +e _Y (θ _i ) (1)

m ₂ ＝m _A +{e _C cosθ _i +e _X (θ _i )}tanφ ₂ (θ _i )+e _C sinθ _i +e _Y (θ _i ), i=1, 2, ..., N (2)

Among them, N is the number of gear teeth; e _C is the eccentric error of the gear; e _X and e _Y are the rotation errors of the gear in the X and Y axis directions respectively; Φ ₁ and Φ ₂ are the angles between the two measured tooth surfaces and the X axis, The data are obtained through measurement, and _θi is the gear rotation angle, which is measured in real time by the built-in angle sensor of the measuring platform.

Subtract (1)(2) to get

It can be seen from the formula (3) that the error in the Y direction is completely eliminated after the subtraction. In order to reduce the error in the X direction, the measured Δm is averaged after the gear is rotated once to obtain Δm _ave

in

The average value Δm _ave of the measurement difference Δm can be calculated by obtaining the values of m ₁ and m ₂ through real-time measurement, and ΔE _X can also be calculated by measuring e _C , e _X , Φ ₁ and Φ ₂ and the real-time measured rotation angle θ _i Then the final and more accurate cutting error Δα can be obtained; from the results, it can be seen that the error in the Y direction has been eliminated, and ΔE _X is mainly determined by the size of the error in the X direction, as long as the average value is obtained through multiple rotation measurements It can be greatly reduced, and the Δα measured by this method is the cutting error of the flexible gear.

In order to verify the feasibility of this method, three gear samples with cutting errors of -6 μm, 0, and +6 μm were selected for testing experiments. Figure 4 shows the measurement differences of the two probes measured by the three gear samples rotating one circle respectively. The value of Δm, the abscissa indicates the rotation angle, and the ordinate indicates the measurement difference between the two probes. It can be seen from the figure that the measurement results include external factors such as eccentricity error and rotation error; Figure 5 shows three gear samples The average value Δm _ave of the measurement difference obtained after the multi-turn measurement respectively, the abscissa represents different cutting errors, the ordinate represents Δm _ave , and σ represents the measurement uncertainty, which is the average error of Δm _ave , from the figure It can be seen that Δm _ave has a linear relationship with the cutting error, which conforms to the law of (4), indicating that the measurement method is feasible. The measurement uncertainty of the three gears is ±1.83μm, which meets the actual requirements of the production line.

Claims (5)

1. a kind of cutting error measurement method of harmonic speed reducer flexible gear, it is characterised in that the measuring method is included such as Lower step：

(1) flexible gear is fixedly mounted on wheel measuring platform using static pressure cylinder fixture, test desk is driven by stepper motor It is dynamic；Again by two laser probes it is parallel be fixed on at gear equal height；

(2) before actually measurement, first to carrying out calibration measurement with reference to gear；Adjust the distance between two parallel probes so that swash Two measurement points of the light on the flank of tooth are respectively positioned on pitch circle, now laser probe 1 measure apart from m₁₀Visited equal to laser First 2 measure apart from m₂₀Equal to probe to pitch circle apart from m_A；

(3) change after the gear for needing to measure, rotate gear is measured, m_BThe distance when distance measured of being popped one's head in for two is equal, With reference gear ratio compared with m_AWith m_BBetween error delta α be cutting error, be theoretical value；

(4) Data Collection and calculating：Test desk by driving stepper motor, every turn once collect a data, therefore collect Data occur in discrete form, and the exact value of cutting error is obtained by calculating, X-Y coordinate, Y-axis are set up in the horizontal plane It is parallel with laser, when the measurement of laser probe 2 is apart from m₂Equal to m_AWhen, the measurement result m of laser probe 1₁M can be used_A+ 2 Δ α tables Show, then m₁With m₂It is represented by

m₁=m_A+2Δα+{e_Ccosθ_i+e_X(θ_i)}tanφ₁(θ_i)+e_Csinθ_i+e_Y(θ_i) (1)

m₂=m_A+{e_Ccosθ_i+e_X(θ_i)}tanφ₂(θ_i)+e_Csinθ_i+e_Y(θ_i), i=1,2 ..., N (2)

Wherein N is number of gear teeth；e_CFor gear eccentricity error；e_XAnd e_YRespectively gear is in X and the rotation error of Y direction；Φ₁ And Φ₂The angle of the respectively two measurement flank of tooth and X-axis, obtains data, θ by measurement_iFor pinion rotation angle, pass through survey Amount platform built-in angular sensor is measured in real time；

Obtained after (1) (2) are subtracted each other：

Understand that the error for subtracting each other rear Y-direction is completely eliminated by (3) formula, in order to reduce the error of X-direction, gear is rotated a circle The Δ m that measurement is obtained afterwards, which averages, produces Δ m_ave

Wherein

M is obtained by measuring in real time₁And m₂Value can calculate measurement difference DELTA m average value Δ m_ave, Δ E_XIt can also lead to Cross measurement e_C、e_X、Φ₁And Φ₂And the anglec of rotation θ measured in real time_iCalculate, then final cutting error delta α exact value 2 Δ α=Δ m can be passed through_ave-ΔE_XTry to achieve；The error for finding out Y-direction from result has been eliminated, Δ E_XMainly by X-direction What error size was determined, can significantly it reduce as long as being averaged by multiple rotary measurement, the Δ measured by the method α, as flexible gear cutting error.

2. a kind of cutting error measurement method of harmonic speed reducer flexible gear as claimed in claim 1, it is characterised in that： The laser probe uses LC-2420 type laser displacement sensors, and resolution ratio is 10nm；Two displacement transducers pass through A/D module It is connected with computer, carries out data acquisition with calculating.

3. a kind of cutting error measurement method of harmonic speed reducer flexible gear as claimed in claim 1, it is characterised in that It is described make it that two measurement points of the laser on the flank of tooth are respectively positioned on finger on pitch circle：In two gear teeth of the measurement with reference to gear When, rotated clockwise with reference to gear edge, m₁₀It is gradually reduced, m₂₀Gradually increase, when turning over θ_AIt is two spies when the latter two are equal Head arrives the distance of pitch circle, and now two measurement points are respectively positioned on pitch circle.

4. a kind of cutting error measurement method of harmonic speed reducer flexible gear as claimed in claim 1, it is characterised in that： Described reference gear refers to cutting error and meets flexible gear in error range, and regards the gear cutting error as 0.

5. a kind of cutting error measurement method of harmonic speed reducer flexible gear as claimed in claim 1, it is characterised in that： The gear for needing to measure with reference to gear with should be gear of the same race.