JP2014167421A - Prediction method of bearing damage state and peeling lifetime - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a prediction method of a bearing damage state and a prediction method of a peeling lifetime that have a high prediction accuracy and can respond to the case in which the hardness of a bearing component member is changed.SOLUTION: The state of a damage occurring in a component member of a bearing during an operation of the bearing is predicted on the basis of the contact pressure when the component member is in contact with the other component members of the bearing, and the plasticity exponent or a parameter including the plasticity exponent as a factor. The peeling lifetime of the component member during the operation of the bearing is predicted on the basis of the contact pressure when the component member of the bearing is in contact with the other component members of the bearing, the plasticity exponent, the sliding rate, and the surface roughness of the component member and the other component members.

Description

  The present invention relates to a method for predicting the form of surface damage of a bearing component that occurs in the operation of a bearing. The present invention also relates to a method for predicting the number of loads (hereinafter referred to as peeling life) until peeling of a bearing component occurs when peeling is predicted as surface damage.

  Rolling bearing surface damage can be broadly divided into flaking, peeling, wear, and smearing. Of these, flaking is a phenomenon in which when the rolling bearing is operated under load and the number of rolling contact cycles exceeds a certain value, the raceway surface and the surface of the rolling element peel off in a scaly manner. The rated life of the rolling bearing is determined.

  Peeling is a phenomenon in which the surface peels off at a depth of several μm to 10 μm when the number of rolling contact repetitions exceeds a certain value. As an example in which the occurrence of peeling is often seen, there is a case in which the peeling occurs on the smooth surface side due to rolling of the rough surface and the smooth surface in a state where the lubricating oil film is insufficient. Research on bearing components that can improve the peeling damage life and extend the life of the bearing has been made (see Patent Documents 1 and 2).

  Smearing is a collection of minute seizures generated on the surface of a rolling bearing. As a cause of smearing, it is considered that slip occurs during the rolling motion of the rolling element, and the performance of the lubricant is insufficient. In order to prevent the occurrence of slipping in order to prevent smearing damage, a preload in the radial direction is applied to the cylindrical roller bearing in consideration of operating conditions, bearing life, and the like. In addition, a smearing damage prevention apparatus that does not apply a smearing countermeasure method that always applies preload has been studied (see Patent Document 3).

  As described above, since there are several types of bearing surface damage, it is important to predict which surface damage will occur in the bearing in the bearing design. Thus, it is considered to predict the form of surface damage that occurs in the operation of the bearing from the surface roughness of the bearing component that is in rolling contact. The correspondence between the surface roughness of the rolling contact member and the form of surface damage that occurs as a result of operation is investigated in advance by a rolling experiment using a two-cylinder testing machine, etc., and based on the obtained correspondence, This is a method for predicting the form of surface damage that occurs from the surface roughness of a bearing component in rolling contact with a bearing.

Japanese Patent Laid-Open No. 10-196658 JP 2012-219995 A JP 2011-190844 A

  However, in the above prediction method for predicting the surface damage that occurs in the operation of the bearing from the surface roughness of the bearing component in rolling contact, if the hardness of the bearing component is changed in the bearing design, the hardness before the change However, since the correspondence data between the surface roughness and the surface damage obtained by the experiment is not effective for the hardness after the change, there is a problem that the prediction cannot be performed. Moreover, it is desired to further improve the prediction accuracy by more accurately reflecting the actual surface contact state.

  The present invention has been made to cope with such a problem, and has an excellent prediction accuracy and can cope with a case where the hardness of a bearing component member is changed, and a bearing damage form prediction method and a peeling life prediction method. The purpose is to provide.

  The method for predicting a bearing damage mode according to the present invention is a method for predicting a mode of damage to a bearing. The contact pressure and the plasticity index or the plasticity index in the contact between a component of the bearing and another component of the bearing are factors. From this parameter, the form of damage that occurs in the structural member during the operation of the bearing is predicted.

The plastic index ψ is an amount given by ψ = (E / H) (Rq / R) ^0.5 . Here, Rq is the root mean square roughness of the equivalent rough surface, R is the radius of curvature of the protrusion tip of the equivalent rough surface, E is the equivalent Young's modulus, and H is the hardness. Each symbol is given by:
Root mean square roughness Rq of equivalent rough surface
Rq = (Rq ₁ ² + Rq ₂ ² ) ^0.5
Radius of curvature R at the tip of the equivalent rough surface protrusion
R = (R ₁ ² + R ₂ ² ) ^0.5
Equivalent Young's modulus (1 / E) = (1/2) ((1-ν ₁ ² ) / E ₁ + (1-ν ₂ ² ) / E ₂ )
Here, Rq ₁ and Rq ₂ are the mean square surface roughness of the _two contact objects, R ₁ and R ₂ are the curvature radii of the protrusion tips of the two contact objects, ν ₁ and ν ₂ are the Poisson's ratio of the two contact objects, E ₁ And E ₂ is the Young's modulus of the two contact objects, and the subscripts 1 and 2 represent the object numbers of the two objects.

  The method for predicting the bearing damage mode is characterized in that the contact is a rolling contact between a smooth surface of the constituent member and a rough surface of the other constituent member.

  The bearing damage mode prediction method is characterized in that it is predicted which type of peeling, flaking, wear, or smearing is caused by the damage.

  The above bearing damage form prediction method uses a contact pressure and a plastic index or a parameter with the plastic index as a factor, which are created in advance based on the experimental results, as coordinate axes, and is classified according to the type of damage. It is characterized by predicting using a figure.

  The method for predicting the peeling life according to the present invention is a method for predicting the peeling life, which is the number of loads until the peeling is confirmed in the bearing component after the operation of the bearing is started. The peeling life of the component member in the operation of the bearing is predicted from the contact pressure, the plasticity index, the slip ratio in contact with the component member, and the surface roughness of the component member and the other component member. .

  The peeling life prediction method is characterized in that the contact is a rolling contact between a smooth surface of the component member and a rough surface of the other component member.

  The peeling life prediction method described above is based on the experimental results, which are preliminarily created based on the experimental results, using the empirical formula that inputs the contact pressure, plasticity index, slip ratio, and surface roughness and outputs the peeling life. It is characterized by predicting.

  The method for predicting a bearing damage mode according to the present invention is a method for predicting based on a contact pressure in contact between bearing constituent members and a plasticity index or a parameter having a plasticity index as a factor. When changing the hardness of the bearing component, the change in hardness is reflected as a change in the plastic index, and the changed surface damage form can be predicted by using the changed plastic index. Thus, the method for predicting the bearing damage mode according to the present invention can cope with a change in the hardness of the bearing constituent member. In addition, the prediction method of the bearing damage mode according to the present invention uses a plasticity index including information such as hardness and Young's modulus as factors in addition to the surface roughness. Improved accuracy is obtained.

  The peeling life prediction method of the present invention is a method for prediction based on contact pressure, plasticity index, slip ratio, and surface roughness in contact between bearing components. When changing the hardness of the bearing component, the change in hardness is reflected as a change in the plastic index, and the changed peeling index can be predicted by using the changed plastic index. Thus, the peeling life prediction method of the present invention can cope with a change in the hardness of the bearing constituent member.

It is the schematic of the damage form figure used with one Example of the prediction method of the bearing damage form of this invention. It is the schematic of the 2 cylinder test machine used for the experiment previously performed with one Example of the prediction method of the bearing damage form of this invention. It is sectional drawing of the drive side straight test piece ((a)) and driven side R60 test piece ((b)) used for the said 2 cylinder test machine. It is an optical microscope observation image of the contact part in each load frequency of the said R60 test piece of the driven side. It is a graph which shows the root mean square roughness of the equivalent rough surface with respect to the load frequency in the said experiment. It is a graph which shows the plastic index with respect to the load frequency in the said experiment. It is a graph which shows the curvature radius of the protrusion front-end | tip of an equivalent rough surface with respect to the load frequency in the said experiment. It is a graph of the empirical formula of peeling lifetime used in one Example of the measuring method of peeling lifetime of this invention.

  The method for predicting a bearing damage mode according to the present invention is based on the contact pressure in contact between a component of the bearing and another component of the bearing, and the plastic index or a parameter factoring the plastic index. Predict the type of damage that will occur to the part. In addition to the contact pressure and the parameters that factor the plasticity index or plasticity index, additional parameters related to the contact may be considered. Examples of the bearing include a rolling bearing, and examples of the contact include a rolling contact. Examples of the constituent member and other constituent members include bearing rings such as an inner ring and an outer ring of the bearing, rolling elements such as balls and rollers, and Examples include combinations selected from cages. Examples of the contact pressure include the maximum contact pressure of Hertz.

The plastic index ψ is an amount given by ψ = (E / H) (Rq / R) ^0.5 . Here, Rq is the root mean square roughness of the equivalent rough surface, R is the radius of curvature of the protrusion tip of the equivalent rough surface, E is the equivalent Young's modulus, and H is the hardness. Each symbol is given by:
Root mean square roughness Rq of equivalent rough surface
Rq = (Rq ₁ ² + Rq ₂ ² ) ^0.5
Radius of curvature R at the tip of the equivalent rough surface protrusion
R = (R ₁ ² + R ₂ ² ) ^0.5
Equivalent Young's modulus (1 / E) = (1/2) ((1-ν ₁ ² ) / E ₁ + (1-ν ₂ ² ) / E ₂ )
Here, Rq ₁ and Rq ₂ are the mean square surface roughness of the _two contact objects, R ₁ and R ₂ are the curvature radii of the protrusion tips of the two contact objects, ν ₁ and ν ₂ are the Poisson's ratio of the two contact objects, E ₁ And E ₂ is the Young's modulus of the two contact objects, and the subscripts 1 and 2 represent the object numbers of the two objects.

  Examples of damage to be predicted include damage that first occurs in the above-described components after the start of operation of the bearing. For example, the damage is confirmed on the surface of the component member by a microscope or the like when the vibration value of the bearing first exceeds a predetermined magnitude after the operation of the bearing is started. Examples of the predetermined magnitude include a predetermined value (for example, 5 times) a vibration value in the initial stage of operation. In addition to this, damage at a reference time set in advance in consideration of the application of the bearing and the like can be mentioned.

  In addition to wear, which is a phenomenon in which materials are gradually lost from the surface due to friction, the surface of the bearing component is separated at a depth of several to 10 μm when the number of rolling contact cycles exceeds a certain value. Peeling, which is a phenomenon that occurs when rolling bearings are operated under load, and flaking, which is a phenomenon where the surface of the raceway and rolling elements peel off in a scaly manner when the number of rolling contact cycles exceeds a certain value There is a smearing that is caused by the addition of sliding motion to rolling motion.

  The prediction of bearing damage according to the present invention is based on the combination of the contact pressure and the plasticity index (or the parameter with the plasticity index as a factor) in contact, and the peeling, flaking, wear, A method of predicting the type of damage such as smearing is preferable.

  As an example in which the occurrence of peeling is often seen, there is a case in which the peeling occurs on the smooth surface side due to rolling of the rough surface and the smooth surface in a state where the lubricating oil film is insufficient. Therefore, as one embodiment of the method for predicting a bearing damage mode according to the present invention, a component of the bearing has a smooth surface, and other components of the bearing have a rough surface, and these surfaces are in rolling contact. And predicting the form of damage occurring on the smooth surface of the component member during the operation of the bearing from the contact pressure in the contact and the plastic index or a parameter having the plastic index as a factor. In the present invention, the terms smooth surface and rough surface represent relative roughness. As an example, regarding arithmetic average roughness Ra, root mean square roughness Rq, etc., when the rough surface is 10 times or more rough than the smooth surface, when the rough surface is 5 times or more rough than the smooth surface, When the rough surface is 3 times or more rough than the smooth surface, the rough surface is 0.1 μm or more and the smooth surface is less than 0.1 μm.

  In general, a rolling bearing in which a sufficient lubricating film is formed reaches the end of its life due to flaking, but when the lubricating film is insufficient, surface damage such as peeling and smearing occurs. Therefore, the bearing damage mode prediction method of the present invention is mainly used when the lubricating film is insufficient, and is useful when the oil film parameter is 3 or less, particularly 1 or less. Alternatively, it is useful for boundary lubrication or mixed lubrication.

  As an embodiment of the present invention, based on experimental results, a prediction means having information that associates a damage form with a set of a contact pressure and a plasticity index (or a parameter having a plasticity index as a factor) is created in advance. And the form which applies this prediction means to the bearing of prediction object is mentioned. In particular, it is possible to use, as a predicting means, a damage configuration diagram that is preliminarily created based on experimental results and uses a contact pressure and a plasticity index (or a parameter having a plasticity index as a factor) as coordinate axes to divide the area into regions according to the type of damage. preferable.

  As an experiment to be performed in advance, an experiment using an experimental apparatus such as a two-cylinder tester or a bearing can be given. In the creation of the prediction means, the form of damage associated with the set of the contact pressure and the plasticity index (or the parameter with the plasticity index as a factor) is the form of damage that occurs first after the start of operation. Can be mentioned. For example, it is a form of surface damage that is measured by a microscope or the like when a vibration value of an experimental apparatus that has started operation at the set value is measured and the vibration value first exceeds a predetermined magnitude. Examples of the predetermined magnitude include a predetermined value (for example, 5 times) a vibration value in the initial stage of operation. In addition to this, the form of damage at the reference time set in advance in consideration of the application of the bearing and the like can be mentioned.

  The above damage morphologies supplement the results after examining the different types of damage that occur in, for example, several sample contact pressures and plastic index (or parameters with plastic index as a factor). It is obtained by processing.

As an example of the above damage form diagram, as shown in FIG. 1, the contact pressure (maximum contact pressure P _max ) is the vertical axis, the plasticity index is the horizontal axis, and the form of damage corresponding to the segmented region. The top view which displayed is mentioned.

  An example of an experiment performed to create the above-described damage pattern is described below. The following experiment observes the generation process of the surface damage for the bearing steel (SUJ2), and is a case where the occurrence of peeling is observed.

  The test was conducted with a two-cylinder tester shown in FIG. Of the upper and lower rotary shafts, the motor 5 was driven via the belt 4 on the lower shaft. The upper shaft is driven by the traction of the contact portion of the test piece 1. The test piece 1 is attached to the taper portion at the center of the shaft with a width presser, and both left and right ends of the shaft are supported by bearings attached to the housing. The distance between the upper and lower axes is 40 mm. The test piece 1 is in contact while being pressed by the spring 3. The lubricating oil is circulated and supplied from the oil supply port 2 in the vicinity of the contact portion of the test piece 1.

  For the experiment, cylindrical test pieces shown in FIG. 3 and Table 1 were used. On the drive shaft side, a test piece with a straight section of the contact portion (straight test piece, FIG. 3A) is provided. On the driven side, a test piece with a cross section of the contact portion in an arc shape (R60 test piece, FIG. 3). (B)) was mounted. The outer diameter surface of the 0.06 μm Ra test piece is obtained by superfinishing, and the 0.33 μm Ra test piece is obtained by grinding. A non-contact laser microscope was used for measuring the surface roughness.

Table 2 shows the test conditions. Lubrication was carried out using boundary-lubricated VG2 additive-free lubricating oil. The number of loads was set from 10 ³ to 10 ⁵ times.

The optical microscope observation image of the contact part in each load frequency of the driven side R test piece with a large surface change compared with the drive side straight test piece is shown in FIG. The processed pattern confirmed on the surface before the experiment in FIG. 4A gradually decreases when the number of loads in FIGS. 4B and 4C is 10 ³ times and 10 ⁴ times. In FIG. 4C, peeling is slightly generated. Thereafter, the load count 10 ⁵ times in FIG. 4 (d), peeling spreads the contact portion areas.

  FIG. 5 shows the root mean square roughness Rq of the equivalent rough surface at each load. When peeling occurs in the entire area, Rq greatly increases.

FIG. 6 shows the plasticity index ψ = (E / H) (Rq / R) ^0.5 calculated to estimate the severity of contact between the protrusions as defined above. FIG. 7 shows the radius of curvature R of the tip of the equivalent rough surface protrusion necessary for this calculation. R at the tip of the projection of the equivalent rough surface becomes maximum at the load count of 10 ³ times and then decreases. The plasticity index is less than 2 at a load number of 10 ³ to 10 ⁴ times, and is much closer to an elastic contact state. Thereafter the plastic contact state again in 10 ⁵ times the peeling is developed.

Peeling begins to occur at 10 ⁴ times, even though the roughness decreases at 10 ³ times. Under these conditions, since the roughness is reduced, the interprotrusion interference is close to an elastic contact state. That is, in the early projections interference, and proceeds rolling fatigue and local plastic deformation, where under load of 10 ⁴ times, be understood that micro flaking occurs.

In this experiment, the 10 ^three previous initial rolling contact occurs in the vicinity of fatigue contact surface by repeated load, it has led to peeling. Thus, it can be seen that the plasticity index at the initial stage of operation, that is, before the start of operation, has a great influence on the occurrence of peeling.

  Color-coded plots on the plane with the maximum contact pressure and the plastic index as the coordinate axes so that the peeling corresponds as a damage mode to the set of the plastic index and the maximum contact pressure in the contact between the two cylinders at the start of this experiment. . The same experiment is performed with various combinations of the plastic index and the maximum contact pressure, and a damage configuration diagram is created.

  The method for predicting the peeling life of the present invention is based on the contact pressure, plasticity index, slip ratio, and surface roughness of the component member and the other component member in contact between the component member of the bearing and the other component member of the bearing. Predicting the peeling life of the component in operation of the bearing. Examples of the bearing include a rolling bearing, and examples of the contact include a rolling contact. Examples of the constituent member and other constituent members include bearing rings such as an inner ring and an outer ring of the bearing, rolling elements such as balls and rollers, and Examples include combinations selected from cages. Examples of the contact pressure include the maximum contact pressure of Hertz. Examples of the surface roughness include arithmetic average roughness Ra, root mean square roughness Rq, and the like.

The plastic index ψ is an amount given by ψ = (E / H) (Rq / R) ^0.5 . Here, Rq is the root mean square roughness of the equivalent rough surface, R is the radius of curvature of the protrusion tip of the equivalent rough surface, E is the equivalent Young's modulus, and H is the hardness. Each symbol is given by:
Root mean square roughness Rq of equivalent rough surface
Rq = (Rq ₁ ² + Rq ₂ ² ) ^0.5
Radius of curvature R at the tip of the equivalent rough surface protrusion
R = (R ₁ ² + R ₂ ² ) ^0.5
Equivalent Young's modulus (1 / E) = (1/2) ((1-ν ₁ ² ) / E ₁ + (1-ν ₂ ² ) / E ₂ )
Here, Rq ₁ and Rq ₂ are the mean square surface roughness of the _two contact objects, R ₁ and R ₂ are the curvature radii of the protrusion tips of the two contact objects, ν ₁ and ν ₂ are the Poisson's ratio of the two contact objects, E ₁ And E ₂ is the Young's modulus of the two contact objects, and the subscripts 1 and 2 represent the object numbers of the two objects.

  The slip ratio is a value obtained by dividing the speed on the fast side of these members by the speed on the slow side in the slip that occurs between the constituent member and the other constituent member due to the motion of the bearing. 1 if there is no slip.

  The peeling life in the present invention represents the number of loads until the ratio of the surface where peeling occurs on the surface of the component of the bearing after the start of operation of the bearing exceeds a certain value. For example, after starting the bearing operation, when the vibration value of the bearing first exceeded a predetermined magnitude, the surface of the above component was observed with a microscope or the like, and the ratio of the surface where peeling occurred exceeded a certain value. Is confirmed, the number of loads from the start time of the operation to that time is defined as the peeling life. As the predetermined magnitude, for example, a predetermined multiple (for example, five times) a vibration value in the initial stage of operation can be cited.

  As described above, an example in which the occurrence of peeling is often seen in a bearing is the case where it occurs on the smooth surface side due to rolling of the rough surface and the smooth surface in a state where the lubricating oil film is insufficient. Therefore, as one embodiment of the peeling life prediction method of the present invention, there is a case where the contact is a rolling contact between the smooth surface of the constituent member and the rough surface of the other constituent member. In addition, the meaning of the terms smooth surface and rough surface is the same as in the case of the prediction method of the above-described bearing damage mode.

  The peeling life prediction method of the present invention can be used to predict the peeling life when the occurrence of peeling is predicted by the above-described bearing damage configuration prediction method.

  The peeling life prediction method of the present invention is mainly intended for cases where the lubricating film is insufficient, and is useful when the oil film parameter is 3 or less, particularly 1 or less. Alternatively, it is useful for boundary lubrication or mixed lubrication.

  As an embodiment of the present invention, based on experiments, an empirical formula is created in which a set of contact pressure, plasticity index, slip ratio, and surface roughness is input and peeling life is output.

  As an experiment to be performed in advance, an experiment using an experimental apparatus such as a two-cylinder tester or a bearing can be given. Examples of the two-cylinder tester used include the same ones as in the above experimental example.

  In the bearing to be predicted and the experimental apparatus to be performed in advance, the peeling life of the component that is the prediction target (test target) is the number of loads at which peeling of a certain area ratio or more is first confirmed on the surface of the component. .

In an experimental apparatus for an experiment to be performed in advance, the maximum contact pressure P _max of Hertz is taken as the contact pressure in contact between the component to be tested and another component, the plasticity index in the contact is ψ, the slip ratio is N, and coarse The side surface roughness is represented by Y, the fine side surface roughness is represented by X, and the peeling life of the constituent members is represented by L. At this time, the following formula (1) is given as an example of the above empirical formula.

L = a × P _max ^α × ψ ^β × N ^γ × (Y / X) ^ε + b (1)

Here, α, β, γ, ε, and a and b are constants, and these constants are determined by regression analysis from the results of the experiment in which the parameters in the contact are changed.

FIG. 8 is a graph of an example of this empirical formula. The horizontal axis of the coordinates is P _max ^α × ψ ^β × N ^γ × (Y / X) ^ε , and the vertical axis is the peeling life L. In this example, the coefficients are a = −24.47, b = 61627, α = 1.51, β = 144.5, γ = 3.34, and ε = 0.978.

  In various rolling bearings, a method for predicting the damage form and estimating a peeling life will be described below.

Usually, damage occurs on the non-rotating raceway surface that receives the maximum load. Therefore, the oil film thickness there is obtained by calculation to determine whether it is mixed lubrication or boundary lubrication. Next, in the above case, the plastic index ψ and the maximum contact pressure P _max of the contact portion are calculated, and the damage form is determined using FIG.

  When it is determined as peeling in the above, the sliding ratio of the contact portion is calculated, and the peeling life is calculated by the equation (1).

  If the required life is not reached, the internal specifications of the rolling bearing are changed, for example, to reduce the surface roughness or reduce the contact pressure. By using the present invention in this way, it is possible to prevent an unexpected short life from occurring when incorporated in a machine.

  For the calculation of the slip ratio, for example, the method of non-patent literature (Sakaguchi / Akamatsu, Tribologist, 2006, Influence of Roller Rolling Surface Shape on Bearing Characteristics of Spherical Roller Bearing (1st Report)) This can be done by using

  The bearing damage mode prediction method and the peeling life prediction method of the present invention are methods that use means that can cope with changes in the hardness of bearing components, and are therefore suitable for bearing design including selection of bearing materials. Available to:

1 Test piece 2 Refueling port 3 Spring 4 Belt 5 Motor

Claims (7)

A method for predicting the form of damage to a bearing,
Predicting the form of damage that occurs in the component during operation of the bearing from the contact pressure in contact between the component of the bearing and the other component of the bearing, and the plasticity index or a parameter based on the plasticity index A method for predicting a bearing damage mode.   2. The method for predicting a bearing damage mode according to claim 1, wherein the contact is a rolling contact between a smooth surface of the component member and a rough surface of the other component member.   3. The method for predicting a bearing damage mode according to claim 1, wherein the damage is predicted to be any one of peeling, flaking, wear, and smearing.   Predicted by using a damage morphology diagram that is preliminarily created based on the experimental results, using the contact pressure and the plastic index or the parameter with the plastic index as a factor as the coordinate axes, and categorized according to the type of damage. The method for predicting a bearing damage mode according to claim 3. A method of predicting a peeling life, which is the number of loads until peeling is confirmed in a bearing component after the operation of the bearing is started,
The peeling life in the operation of the bearing is determined from the contact pressure, plasticity index, slip ratio, and surface roughness of the constituent member and the other constituent member in contact between the bearing constituent member and the other constituent member of the bearing. A method for predicting a peeling life characterized by predicting.   6. The peeling life prediction method according to claim 5, wherein the contact is rolling contact between a smooth surface of the constituent member and a rough surface of the other constituent member.   The peeling life is predicted using an empirical formula that is preliminarily created based on the experimental results and uses the contact pressure, plasticity index, slip ratio, and surface roughness as input and the peeling life as output. The peeling life prediction method according to claim 5 or claim 6.