JP4098503B2 - Indentation formation mechanism and hardness tester - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an indentation forming mechanism used in a testing machine that evaluates material properties of a sample based on the formation of an indentation by pushing an indenter into the surface of the sample, and a hardness tester equipped with the indentation forming mechanism.
[0002]
[Prior art]
An indentation type hardness tester is used for evaluating the physical properties of the surface of a cutting tool, casting, plastic, IC wafer or other solid sample. This hardness tester presses the indenter against the measurement surface of the sample, and after the indentation force reaches the target value, the target value is held for a predetermined time, and then the indenter penetration amount, that is, the indentation depth, the surface area of the indentation, etc. Based on this, the hardness of the sample is measured. Note that the target value is maintained for a predetermined time in order to avoid an error that the indentation depth is reduced due to the elastic deformation of the sample and the apparent hardness is extremely increased.
[0003]
Such an indentation type hardness tester is also provided that can follow the indenter's indentation force to a predetermined target value as disclosed in Japanese Patent Application Laid-Open No. 2000-304670. This hardness tester includes a servo motor that applies a pressing force to the indenter via a leaf spring that is an elastic member. In the process of driving the servo motor, the pushing force of the indenter is determined from the amount of spring displacement of the leaf spring. By calculating and performing feedback control of the servo motor based on the calculated pressing force, the pressing force at that time follows the given target value.
According to this hardness tester, since it is possible to avoid the indentation force from overshooting the target value, it is possible to perform a hardness test according to the standard.
[0004]
[Problems to be solved by the invention]
However, in the hardness tester as described above, it has not been possible to realize control for maintaining the increase rate of the indenter pushing force, that is, the load speed, at a desired value during the indentation process. Therefore, there is a case where the load speed varies depending on the sample, and it is difficult to test a plurality of samples under exactly the same conditions.
Further, from the viewpoint of convenience, it corresponds to the sum of the time until the pushing force reaches the target value (hereinafter referred to as “load time”) and the time for holding the target value (hereinafter referred to as “holding time”). In the testing machine in which the test load loading time can be set in advance, the load speed varies depending on the sample. As a result, there is an adverse effect that the holding time varies for each sample. For this reason, it has been necessary to perform a preliminary test each time a test is performed on samples of different materials, to examine the load time of the sample, and to reset the test load load time.
[0005]
The present invention has been made in view of such problems, and an object thereof is to provide a technique for accurately performing a hardness test at a load speed according to a standard.
[0006]
[Means for Solving the Problems]
  In order to achieve the above object, the invention described in claim 1 is characterized in that, as shown in FIGS. An indentation formation mechanism (10) used in a testing machine for measuring
  A force applying means (for example, a servo motor 61) for applying a pressing force for forming an indentation on the sample surface to the indenter, and an elasticity for transmitting the force applied by the force applying means to the indenter. Changes in the detection results of the member (for example, the leaf spring 7), the elastic displacement amount detecting means (for example, the spring displacement amount sensor 64) for detecting the elastic displacement amount of the elastic member, and the elastic displacement amount detecting means. An increase rate calculating means (for example, a differentiator 65 or the like) for calculating an increase rate of the pushing force acting on the indenter based on the increase rate calculated by the increase rate calculating means, and a preset target increase rate On the basis of the comparison with the increase rate control means (for example, load arm operation control unit 67 etc.) feedback control the force applying means so that the increase rate follows the target increase rate,
A pushing force calculating means (for example, a spring displacement amount sensor 64) for calculating a pushing force acting on the indenter based on a detection result of the elastic displacement amount detecting means, and a pushing force calculated by the pushing force calculating means. The pushing force is determined by the pushing force determining means (for example, the determining unit 661) for determining whether or not the force has reached a predetermined critical pushing force less than a preset target pushing force, and the pushing force determining means. When it is determined that the critical pushing force has been reached, a pushing force control means (for example, a load arm operation control unit 67) that controls the force applying means so that the pushing force converges to the target pushing force; The increase rate control means performs feedback control of the force applying means when the determining means determines that the pushing force has not reached the critical pushing force.It is characterized by.
[0007]
Here, a test machine that measures the material properties of a sample based on forming an indentation with an indenter on the sample surface is, for example, a hardness tester that measures hardness, and an electrical resistance of the sample during the formation of the indentation. However, the present invention is not limited thereto, and includes all testing machines having an indentation forming mechanism.
The force applying means includes, for example, a motor drive, a hydraulic pressure, and a piston driven by pneumatic pressure. However, the force applying means is not limited to this, and any force applying means can be used. May be.
The elastic member is a leaf spring, a coil spring or the like.
As the elastic displacement amount detecting means, a linear scale, a capacitor pick (charge capacitance type displacement sensor), an LVDT (operating transformer), an electric micrometer, or the like is used, but is not limited thereto, and the elastic deformation of the elastic member is used. Any material can be used as long as the amount can be measured.
[0008]
  According to the first aspect of the invention, the elastic displacement amount of the elastic member is detected by the elastic displacement amount detection means, and the pushing force acting on the indenter based on the change in the detection result of the elastic displacement amount detection means by the increase rate calculation means. The rate of increase (load speed) is calculated, and the rate of increase follows the target rate of increase based on a comparison between the rate of increase calculated by the rate of increase calculation means and the target rate of increase set in advance by the rate of increase control means. Thus, the force applying means is controlled so that the load speed acting on the sample is always maintained at the target value in the course of the test. Therefore, the hardness test can be accurately performed at a load speed according to the standard.
Also, until the indenter pushing force reaches the critical pushing force, the force applying means is controlled by the increase rate control means so that the load speed of the indenter becomes constant, and after the pushing force of the indenter reaches the critical pushing force, the pushing force is controlled. Since the force applying means is controlled by the force control means so that the pushing force converges to the target pushing force, it is possible to reliably avoid the pushing force of the indenter from overshooting the target pushing force.
[0009]
  The invention according to claim 2For example, as shown in FIGS. 1 to 8, an indentation formation mechanism (10) used in a testing machine for measuring material characteristics of a sample based on forming an indentation on the surface of the sample (S) by an indenter (3). There,
A force applying means (for example, a servo motor 61) for applying a pressing force for forming an indentation on the sample surface to the indenter, and an elasticity for transmitting the force applied by the force applying means to the indenter. Changes in the detection results of the member (for example, the leaf spring 7), the elastic displacement amount detecting means (for example, the spring displacement amount sensor 64) for detecting the elastic displacement amount of the elastic member, and the elastic displacement amount detecting means. An increase rate calculating means (for example, a differentiator 65 or the like) for calculating an increase rate of the pushing force acting on the indenter based on the increase rate calculated by the increase rate calculating means, and a preset target increase rate On the basis of the comparison with the increase rate control means (for example, load arm operation control unit 67 etc.) feedback control the force applying means so that the increase rate follows the target increase rate,
An intrusion amount detecting means (for example, arm position sensor 8) that detects the intrusion amount of the indenter into the sample, and the intrusion amount detected by the intrusion amount detecting means is less than a preset limit intrusion amount. An intrusion amount determining means (for example, a load arm operation control unit 67) that determines whether or not a predetermined critical intrusion amount has been reached, and the intrusion amount has reached the critical intrusion amount by the intrusion amount determining means. An intrusion amount control means (for example, a load arm operation control unit 67) that controls the force applying means so that the intrusion amount converges to the limited intrusion amount when determined, and the increase rate control means Is characterized in that when the intrusion amount determining means determines that the intrusion amount has not reached the critical intrusion amount, feedback control of the force applying means is performed.
[0010]
  According to invention of Claim 2,The elastic displacement amount detection means detects the elastic displacement amount of the elastic member, and the increase rate calculation means calculates the increase rate (load speed) of the pushing force acting on the indenter based on the change in the detection result of the elastic displacement amount detection means. The force applying means is controlled by the increase rate control unit so that the increase rate follows the target increase rate based on a comparison between the increase rate calculated by the increase rate calculating unit and a preset target increase rate. The load speed acting on the sample is always maintained at the target value during the course of the test. Therefore, the hardness test can be accurately performed at a load speed according to the standard.
  Also, until the indentation amount reaches the critical penetration amount, the force applying means is controlled by the increase rate control means so that the load speed of the indenter becomes constant, and after the indentation penetration amount reaches the critical penetration amount, Since the force applying means is controlled so that the intrusion amount of the indenter converges to the limited intrusion amount by the amount determining means, it is possible to reliably avoid the intrusion amount of the indenter from overshooting the target intrusion amount.
[0011]
  The invention described in claim 33. The indentation forming mechanism according to claim 1 or 2, wherein the increase rate calculation means includes the detection result of the elastic displacement amount detection means at an arbitrary time point and the elastic displacement after a predetermined sampling period has elapsed from the time point. The increase rate is calculated based on the difference between the detection result of the amount detection means andIt is characterized by that.
[0012]
  According to invention of Claim 3,Claim 1 or 2Of course, the effects of the described invention can be obtained.The increase rate calculating means calculates the increase rate based on the difference between the detection result of the elastic displacement amount detection means at an arbitrary time and the detection result of the elastic displacement amount detection means after a predetermined sampling period has elapsed from that time point. Since it is calculated, the increase rate can be calculated quickly. Such an increase rate calculating means can be realized by software.
[0013]
  Invention of Claim 4The hardness testing machine (1) is based on the indentation forming mechanism (10) according to any one of claims 1 to 3 and a predetermined measurement result relating to the form of the indentation formed on the sample by the indentation forming mechanism. A hardness calculation means (for example, a hardness calculation unit 9) for calculating the hardness of the sample.It is characterized by that.
[0014]
  According to invention of Claim 4, the indentation formation mechanism in any one of Claims 1-3Therefore, it is possible to provide a hardness tester capable of accurately performing a hardness test at a load speed according to the standard.
Here, for example, the hardness calculating means may calculate the hardness of the sample based on the depth of the indentation, or based on the diagonal length of the indentation in plan view May be calculated.
The hardness tester is, for example, a Rockwell hardness tester, a Vickers hardness tester, a Brinell hardness tester, or a Martens hardness tester.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram illustrating a main configuration of a hardness tester according to an embodiment.
As shown in FIG. 1, a hardness tester 1 includes a tester main body 2, a load arm 4 rotatably supported by the tester main body 2, and an indenter 3 attached to a free end, and an indenter 3. Is provided below the test machine main body 2 and is provided below the sample stage 5 on which the sample S is placed and the load arm 4, and the free end side of the load arm 4 is rotated to form an indentation on the sample surface. Indentation forming mechanism portion configured by a load arm actuating portion 6 for applying a force for applying a pressing force and a leaf spring 7 for transmitting the force generated when the load arm actuating portion 6 is actuated to the load arm 4 10 and an arm position sensor 8 that measures the depth of the indentation formed by the indenter 3, and a hardness calculation unit 9 that calculates the hardness of the sample S based on the measurement by the arm position sensor 8 (FIG. 3). See).
[0018]
Further, the hardness tester 1 includes an input device (not shown) for inputting test conditions such as a target pushing force and a load speed, a test condition input screen (see FIG. 7) described later, and a hardness calculation unit 9. And an output device 11 (see FIG. 3) that displays and outputs the hardness calculated by.
These input device and output device may be externally attached to the hardness tester 1 in a detachable manner.
[0019]
The testing machine main body 2 includes a load arm operating unit 6 and an electrical component 21 serving as a drive source for the load arm operating unit 6. The load arm 4 is rotatably supported on the testing machine main body 2 by a cross spring 41 or a rolling bearing, and an indenter 3 is detachably attached to a free end portion. The load arm 4 is integrated with a leaf spring 7. A groove 7a is provided along the longitudinal direction between the leaf spring 7 and the load arm 4, and the tip of the groove 7a on the indenter 3 side is open.
[0020]
The sample stage 5 is provided with a square screw 51 on its lower surface, and is attached to the tester main body 2 by the square screw 51 so as to be movable up and down. Furthermore, an autobrake mechanism 52 that automatically stops the sample stage 5 when the sample S and the indenter 3 come into contact with each other is provided. The load arm actuating unit 6 includes a servo motor 61 as an electric actuating means, a ball screw 62, and a fixing jig 63 attached to the tip of the ball screw 62 and fixed to the leaf spring 7. Therefore, when the servo motor 61 is driven and the ball screw 62 moves up and down, the load arm 4 integrated with the leaf spring 7 is rotated. The fixing jig 63 connects the load arm 4 and the load arm actuating portion 6, and the axis of the leaf spring 7 and the axis of the load arm actuating portion 6 due to the rotational movement of the load arm 4 and the elastic deformation of the leaf spring 7 are incorrect. It has a function of absorbing alignment, and is composed of, for example, a thin plate, a wire such as a piano wire, a combination of a knife edge and a cross spring, a universal joint, or the like.
[0021]
As shown in FIG. 2, the operation control of the load arm 4 is performed by a spring displacement sensor 64 attached to the load arm 4 and the leaf spring 7 to detect the opening amount thereof, that is, the amount of spring deformation of the leaf spring 7. A differentiator 65 for differentiating the detection result of the spring displacement sensor 64 with respect to time, a switching unit 66 for selectively adopting and outputting the detection result of the spring displacement sensor 64 or the differentiation result of the differentiator 65, and this switching unit 66 This is performed by a load arm operation control unit 67 that performs feedback control of the servo motor 61 based on the output from.
[0022]
The spring displacement sensor 64 is composed of, for example, a displacement sensor unit (linear scale) that optically reads a glass scale. By the downward operation of the ball screw 62, the spring displacement sensor 64 detects the amount of opening of the groove 7a between the leaf spring 7 and the load arm 4. The amount of spring displacement is detected, and the detected amount of spring displacement is A / D converted and output to the switching unit 66.
Here, the amount of spring displacement is equivalent to the pressing force of the indenter 3 or the test load applied to the sample S.
[0023]
The differentiator 65 is realized by software, and the spring displacement detected by the spring displacement sensor 64 at the current time and the spring displacement detected by the spring displacement sensor 64 before the predetermined sampling period from the current time. Is approximately calculated as a time derivative of the amount of spring displacement. That is, in the differentiator 65, time-series data obtained by discretely obtaining the detection results of the spring displacement sensor 64 at a predetermined sampling period are differentiated.
The differentiator 65 can also realize analog hardware using a differentiation circuit or the like, or the above digital sequence by hardware.
[0024]
The switching unit 66 includes a determination unit 661 that determines whether or not the pressing force detected by the spring displacement amount sensor 64 has reached a predetermined critical pressing force that is less than a preset target pressing force. When it is determined that the pushing force has not reached the critical pushing force, the differential result of the differentiator 65 is output to the load arm operation control unit 67, while the pushing force has reached the critical pushing force by the judging unit 661. Is determined, the detection result of the spring displacement sensor 64 is output to the load arm operation control unit 67.
The determination unit 661 can be realized by a comparison determination instruction by software, or can be realized by hardware such as a comparator.
[0025]
The load arm operation control unit 67 includes a first servo gain calculation circuit 671, a load control circuit 672, a second servo gain calculation circuit 673, a load arm position control circuit 674, a D / A converter 675, and a servo motor drive circuit 676. , Etc.
[0026]
The first servo gain calculation circuit 671 is based on the amount of change in load and the indenter 3 based on the amount of spring displacement or load speed output from the switching unit 66 and the arm position signal detected by the arm position sensor 8. A spring constant is calculated from the change in the intrusion amount to determine an initial servo gain (Gf).
Further, the first servo gain calculation circuit 671 increases the servo gain Gf when there is no error change during a predetermined number of feedback steps, and restores the original value when the servo gain Gf exceeds a predetermined value. I do. The servo gain Gf determined by the first servo gain calculation circuit 671 is output to the load control circuit 672. The first servo gain calculation circuit 671 includes a memory (not shown) that stores calculation results.
[0027]
The load control circuit 672 compares the output from the switching unit 66 with a preset target load, and adds the servo gain Gf calculated by the first servo gain calculation circuit 671 to the load control signal corresponding to these differences. Multiply and output to D / A converter 675.
[0028]
The second servo gain calculation circuit 673 is based on the spring displacement amount or load speed output from the switching unit 66 and the arm position signal detected by the arm position sensor 8 and the intrusion of the indenter 3. A spring constant is calculated from the change in quantity to determine an initial servo gain (Gp).
[0029]
The load arm position control circuit 674 compares the arm position signal detected by the arm position sensor 8 with preset target position data, and multiplies the position control signal corresponding to the difference by the servo gain Gp to obtain D / Output to the A converter 675.
[0030]
The servo motor drive circuit 676 receives the load control signal and the position control signal D / A converted by the D / A converter 675 as input, amplifies them with a current amplifier 676a in consideration of differential elements and integral elements, and then servo motors To 61.
[0031]
Similarly to the spring displacement sensor 64, the arm position sensor 8 is composed of, for example, a displacement sensor unit (linear scale) that optically reads a glass scale, and measures the amount of movement of the load arm 4 in the vertical direction.
Here, the amount of movement of the load arm 4 in the vertical direction is equivalent to the amount of penetration of the indenter 3 into the sample S.
[0032]
As shown in FIG. 3, the hardness calculation unit 9 includes an amplifier 91, an A / D converter 92, an arithmetic circuit 93, an output circuit 94, and the like.
[0033]
The amplifier 91 amplifies the arm position displacement signal detected by the arm position sensor 8 and outputs the amplified signal to the A / D converter 92. The A / D converter 92 A / D converts the amplified arm position displacement signal and outputs it to the arithmetic circuit 93. The arithmetic circuit 93 calculates the hardness by calculating the A / D converted arm position displacement signal according to a built-in arithmetic program, and outputs the hardness to the output circuit 94. The output circuit 94 processes the hardness data calculated by the arithmetic circuit 93 into data of a predetermined output format and outputs the data to the output device 11 connected to the hardness tester 1.
Here, the output device 11 is, for example, a display device that monitors hardness data, or a printing device that prints and outputs hardness data on paper.
[0034]
Then, by driving the servo motor 61 controlled by the servo motor drive circuit 676, the ball screw 62 rotates and operates downward. At this time, the leaf spring 7 attached to the ball screw 62 and the load arm 4 integrated therewith rotate downward, and the indenter 3 attached to the free end of the load arm 4 comes into contact with the sample S. At this time, the opening amount of the groove portion 7a between the leaf spring 7 and the load arm 4 is detected by the spring displacement amount sensor 64 as a spring displacement amount signal, and the detected spring displacement amount signal is amplified and a servo gain calculation circuit 651 is obtained. Is output.
[0035]
Next, the operation of the hardness tester 1 will be described with reference to the flowcharts shown in FIGS.
First, the operation in the constant load speed control (load speed feedback control) will be described with reference to FIG.
As a premise, when the power is turned on, a test condition input screen 70 as shown in FIG. 7 is displayed on a display device (not shown). In FIG. 7, reference numeral 71 denotes an input frame for inputting a target test force (target pushing force) [N] of the indenter. Reference numeral 72 denotes a check box for selecting whether or not to limit the intrusion amount of the indenter in advance. Reference numeral 73 denotes an input frame for inputting the limit value [μm] when limiting the intrusion amount of the indenter.
[0036]
Reference numeral 74 denotes a check box for selecting whether the test condition is designated by the load speed or the load time. Reference numeral 75 denotes an input frame for inputting the load speed [N / sec] when the test condition is designated by the load speed. Reference numeral 76 denotes an input frame for inputting the load time [sec] when the test condition is designated by the load time. When the load time is input here, the load speed is calculated by dividing the target test force input to the input frame 71 by the load time, and the calculated load speed is input to the input frame. 75 is automatically displayed. Reference numeral 77 denotes an input frame for inputting a time [sec] for holding the load when the test force of the indenter reaches the target test force.
[0037]
Here, the user inputs the target test force into the input frame 71 using an input device (not shown). As a result, the target test force is substituted into the parameter “targetF” and set in a memory (not shown) built in the hardness tester 1.
Next, the user inputs the load time in the input frame 76 or inputs the load speed in the input frame. As a result, the target load speed is substituted into the parameter “targetVF” and set in a memory (not shown).
[0038]
Under the premise as described above, in step S1, the load arm operation control unit 67 initializes each variable. That is, the load arm operation control unit 67 initializes values such as servo gain (Gain; Gf), arm position (DIFP), load, that is, the pushing force (DIFF) of the indenter 3.
More specifically, the initial value of the servo gain (Gf) is 1, and the initial value of the arm position and overload is 0.
[0039]
When performing a standard test (Rockwell, Vickers and Brinell scales), it is inconvenient to use the setting method for generating an arbitrary test force described above. Therefore, the test force to be generated is set by selecting a test scale, and the load time is determined by setting the load speed. Alternatively, a setting interface is provided in which the load time is set and the load speed is determined.
[0040]
Next, in step S <b> 2, the pushing force, that is, the load that is the detection result of the spring displacement amount sensor 64 is input to the determination unit 661. At this time, since the load is initialized to 0, the determination unit 661 determines that the load has not yet reached the critical pushing force. Accordingly, the calculation result of the differentiator 65 is selected by the switching unit 66 and input to the load arm operation control unit 67.
[0041]
The value of the critical indentation force is not particularly limited as long as it is less than the target test force (targetF), but if this value is too large, the target test force may be overshot. On the other hand, if this value is too small, the area of constant load speed control is reduced. Therefore, it is desirable to predetermine an optimum value for this value in consideration of the ability of the servo motor 61 and the material of the sample. The critical pushing force may be automatically calculated based on the various parameters described above. Or it is good also as determined by the arbitrary setting by a user.
In the present embodiment, the critical indentation force is 90 percent of the target test force (targetF × 0.9).
[0042]
Here, the calculation performed by the differentiator 65 will be specifically described with reference to FIG. In each step of FIG. 6, the temporary parameter “TempF” stores the amount of spring displacement (pushing force) detected at the time of the previous one cycle from the current time. The parameter “force sensor value” stores a spring displacement value (pushing force) detected at the present time. The parameter “load speed” stores a time differential (difference) value of the spring displacement amount at the present time. This parameter is used in a later feedback control routine.
[0043]
Specifically, in step S61, the differentiator 65 subtracts the amount of spring displacement detected at the present time from the amount of spring displacement detected one cycle before, and substitutes the subtraction result into “load speed”. Next, in step S62, the spring displacement amount detected at the present time is stored in “TempF” for use as a spring displacement amount one cycle later, that is, in the next routine.
Such processes of step S61 and step S62 are executed every time the process of step S2 of FIG. 4 is performed.
[0044]
Referring back to FIG. 4, in step S3, the load control circuit 672 outputs a control signal obtained by multiplying the difference between the current load speed value and the target load speed (targetVF) by the servo gain (Gf). Output to the A converter 675. Accordingly, the servo motor 61 is driven by the servo motor driving circuit 676 and the indenter 3 enters the sample S.
[0045]
Next, in step S4, the determination unit 661 determines whether or not the current load has reached the critical pushing force. When the determination unit 661 determines that the current load has not yet reached the critical pushing force (step S4; NO), the process returns to step S1 again. On the other hand, when it is determined that the current load has reached the critical pushing force (step S4; YES), the process proceeds to step S5, and target force generation control described later is performed.
[0046]
According to the load speed constant control described above, as shown in FIG. 8A, the load speed of the load applied to the sample is kept constant until it reaches 90 percent of the target load (critical pressing force).
[0047]
Next, target force generation control (force feedback control) will be described with reference to FIG.
First, in step S6, the load arm operation control unit 67 initializes each variable.
That is, the value of servo gain (Gain; Gf) is initialized to 1, and the value of error (Err) is initialized to 0.
[0048]
Next, in step S7, the load arm operation control unit 67 stores the detection results of the spring displacement sensor 64 and the arm position sensor 8 in the current state in a built-in memory (not shown). This is for use in load control in the next routine.
[0049]
Next, in step S8, the load arm operation control unit 67 assigns the detection result of the arm position sensor 8 in the current state to the parameter “DIFP” and also sets the detection result of the spring displacement sensor 64 in the current state to the parameter “DIFF”. Assign to.
Next, the servo gain (Gain) in the target force generation control (force feedback control) is calculated by Gain = A × “spring constant of the system including characteristics of the sample and the tester”. A is an arbitrary constant.
Here, since the load value and arm position can be obtained in this testing machine, the above-mentioned “spring constant of the system including the characteristics of the sample and testing machine” indicates the change in load per unit time as the arm per unit time. It is obtained by dividing by the change in position.
Specifically, the load arm operation control unit 67 determines the servo gain (Gain) in the target force generation control (force feedback control) by the following equation (1).
Gain = A x (DIFF-load value) / (DIFP-arm position) (1)
Here, A is an arbitrary constant.
[0050]
Next, in step S9, the load arm operation control unit 67 calculates an error (Err), that is, a difference between the actual load value and the target load value by the following equation (2).
Err = Gain x load value-TargetF (2)
[0051]
Next, in step S10, the load arm operation control unit 67 determines whether an error remains. That is, the load arm operation control unit 67 determines whether or not the difference between the comparison error (Err1) obtained in the previous feedback routine and the current error (Err) is “0”.
Here, whether or not there is an error is determined by determining that an error remains when the error difference is continuously “0” in a predetermined number of feedback routines (for example, five times). Also good. The servo gain may be increased stepwise (for example, every 0.2).
When the load arm operation control unit 67 determines that the difference is “0” (step S10; NO), the load arm operation control unit 67 proceeds to step S12.
On the other hand, when it is determined that the difference is not “0” (step S10; YES), the load arm operation control unit 67 proceeds to step S11. In step S11, the load arm operation control unit 67 performs a process of increasing the servo gain by a predetermined value, and then proceeds to step S12.
[0052]
Next, in step S12, the load arm operation control unit 67 determines whether the servo gain exceeds the allowable upper limit value.
When the load arm operation control unit 67 determines that the servo gain does not exceed the allowable upper limit (step S12; NO), the load arm operation control unit 67 proceeds to step S14.
On the other hand, when it is determined that the servo gain has exceeded the allowable upper limit value (step S12; YES), the load arm operation control unit 67 proceeds to step S13 and performs a process of lowering the servo gain by a predetermined value. The process proceeds to step S14.
[0053]
Next, in step S14, the load arm operation control unit 67 determines whether or not the test force is being held.
When the load arm operation control unit 67 determines that the test force is being held (step S14; YES), the load arm operation control unit 67 proceeds to step S17.
On the other hand, when the load arm operation control unit 67 determines that the test force is not being held (step S14; NO), the process proceeds to step S15.
[0054]
In step S15, the load arm operation control unit 67 determines whether or not the pushing force of the indenter 3 in the current state has reached the target test force. When it is determined that the pushing force is not the target test force (step S15; NO), the load arm operation control unit 67 returns to step S7 and repeats the process again.
On the other hand, when it is determined that the pushing force has reached the target test force (step S15; YES), the load arm operation control unit 67 proceeds to step S16 and starts a timer to maintain the test force. Then, it returns to step S7 and continues the process after step S7.
[0055]
On the other hand, as a result of the determination in step S14, when the process proceeds to step S17, the load arm operation control unit 67 determines whether or not the timer has reached the holding time. In this timer, the holding time [sec] input in the input frame of the test condition input screen 70 is set.
When the load arm operation control unit 67 determines that the timer does not reach the holding time (step S17; NO), the load arm operation control unit 67 returns to step S7 and continues the process.
On the other hand, when it is determined that the timer has reached the holding time (step S17; YES), the load arm operation control unit 67 ends the target force generation control.
[0056]
According to the target force generation control (force food back control) described above, as shown in FIG. 8A, 90% of the target load converges to the target load without overshooting, and the target weight is It is held for a predetermined holding time.
[0057]
Note that, after the constant load speed control (load speed feedback control), position feedback control may be performed instead of the target force generation control (force food back control).
As a condition for switching from constant load speed control (speed feedback control) to position feedback control, instead of step S4 in FIG. 4, the detection result of the arm position sensor 8, that is, the intrusion amount of the indenter is 90% of LIM_DEPTH (LIM_DEPTH × 0). .9) is preferably performed. Here, the variable LIM_DEPTH is a parameter representing the limited intrusion amount [μm] input to the input frame 73 in the test condition input screen 70 shown in FIG.
In step S9 of FIG. 5, the following equation (3) is calculated instead of equation (2).
Err = Gain × arm position−LIM_DEPTH (3)
Further, instead of the processing of step S15 in FIG. 5, it is determined whether or not the detection result of the arm position sensor 8, that is, the intrusion amount of the indenter 3 in the current state has reached the limit intrusion amount (LIM_DEPTH).
As described above, when the position feedback control is performed instead of the target force generation control (force hoodback control), as shown in FIG. The entered indenter 3 converges to the limit intrusion amount without overshooting the limit intrusion amount, and the target load is held for a predetermined holding time.
[0058]
After the target force generation control (force feedback control) or position feedback control is completed, the indentation depth, that is, the intrusion amount of the indenter 3 is measured by the arm position sensor 8 as an arm position signal. Amplified by the amplifier 91, A / D converted by the A / D converter 92, and output to the arithmetic circuit 93.
[0059]
Next, the arithmetic circuit 93 calculates the hardness of the sample S from the arm position signal subjected to A / D conversion by an arithmetic operation based on an internal arithmetic program. The calculated hardness data is monitored by the output device 11 via the output circuit 94.
[0060]
According to the hardness tester 1 described above, the following effects can be obtained.
(1) The elastic displacement amount of the leaf spring 7, that is, the opening amount of the groove 7a is detected by the spring displacement amount sensor 64, and the detection result of the spring displacement amount sensor 64 is differentiated by the differentiator 65, whereby the load speed in the current state is detected. The load arm operation control unit 67 performs feedback control of the servo motor 61 so that the load speed follows the target load speed based on the comparison between the calculation result of the differentiator 65 and a preset target load speed. Therefore, the load speed acting on the sample S is always maintained at the target load speed in the course of the test. Therefore, the hardness test can be accurately performed with a load speed according to the standard.
[0061]
(2) The servomotor 61 is speed-feedback controlled so that the load speed is constant until the pushing force of the indenter 3 reaches the critical pushing force by the load arm operation control unit 67, while the pushing force of the indenter 3 is critical. After reaching the indentation force, force feedback control is performed so that the indentation force converges to the target indentation force, so that the hardness test can be accurately performed at a load speed according to the standard. It can be surely avoided that the pushing force overshoots the target pushing force.
[0062]
(3) The load motor operation control unit 67 performs speed feedback control of the servo motor 61 so that the load speed is constant until the pushing force of the indenter 3 reaches the critical pushing force, while the pushing force of the indenter 3 is critical. After reaching the indentation force, position feedback control is performed so that the intrusion amount of the indenter 3 converges to the limited intrusion amount, so that the hardness test can be performed accurately with a load speed as specified, of course. It is possible to reliably avoid that the amount of intrusion overshoots the target amount of intrusion.
[0063]
(4) The differentiator 65 loads based on the difference between the detection result of the spring displacement sensor 64 at an arbitrary time and the detection result of the spring displacement sensor 64 after a predetermined sampling period has elapsed from that time. Since the speed is approximately calculated, the load speed is calculated quickly, and the speed feedback control is not delayed. Thereby, the controllability of the load arm operation control unit 67 is improved and the reliability of the test conditions is also improved.
[0064]
In the above embodiment, linear scales are used for both the spring displacement sensor 64 and the arm position sensor 8, but the present invention is not limited to this. For example, a capacitor pick (charge capacity displacement sensor), LVDT (actuation) A transformer), an electric micrometer, or the like may be used.
Further, instead of the leaf spring 7, a coil spring, an assembled leaf spring, an integral spring, rubber or the like may be used. Further, in the case where a relatively large load is applied to the sample S, the leaf spring 7 may be a both-end support beam.
[0065]
【The invention's effect】
According to the present invention, since the load speed acting on the sample is always maintained at the target value in the course of the test, the hardness test can be accurately performed with the load speed according to the standard.
[Brief description of the drawings]
FIG. 1 is a side view showing a configuration of a main part of a hardness tester to which the present invention is applied.
FIG. 2 is an internal block diagram of the hardness tester shown in FIG.
FIG. 3 is a block diagram showing a main configuration of a hardness calculation unit provided in the hardness tester shown in FIG. 1;
FIG. 4 is a flowchart for explaining speed feedback control by the hardness tester shown in FIG. 1;
FIG. 5 is a flowchart for explaining force feedback control by the hardness tester shown in FIG. 1;
6 is a flowchart for explaining the operation of a differentiator provided in the hardness tester shown in FIG. 1. FIG.
7 is a diagram showing a test condition input screen displayed on a display device connected to the hardness tester shown in FIG. 1. FIG.
FIG. 8A is a diagram for explaining speed feedback control and force feedback control by a hardness tester, and FIG. 8B is a diagram for explaining speed feedback control and position feedback control by a hardness tester. FIG.
[Explanation of symbols]
1 Hardness tester
3 Indenter
7 Leaf spring (elastic member)
8 Arm position sensor (intrusion detection means)
9 Hardness calculation part (hardness calculation means)
10 Indentation formation mechanism
61 Servo motor (force applying means)
64 Spring displacement sensor (elastic displacement detection means, pushing force calculation means)
65 Differentiator (Increase rate calculation means)
67 Load arm operation control section (increase rate control means, pushing force judgment position means)
661 determination unit (pushing force determination means)
S sample

Claims (4)

An indentation formation mechanism used in a testing machine that measures material properties of a sample based on forming an indentation on the sample surface with an indenter,
A force applying means for applying a force for applying an indentation force to the indenter to form an indentation on the sample surface;
An elastic member for transmitting the force applied by the force applying means to the indenter;
Elastic displacement amount detecting means for detecting an elastic displacement amount of the elastic member;
An increasing rate calculating means for calculating an increasing rate of the pushing force acting on the indenter based on a change in a detection result of the elastic displacement detecting means;
Based on a comparison between the increase rate calculated by the increase rate calculation means and a preset target increase rate, an increase rate that feedback-controls the force applying unit so that the increase rate follows the target increase rate Control means;
A pushing force calculating means for calculating a pushing force acting on the indenter based on a detection result of the elastic displacement amount detecting means;
A pushing force determining means for determining whether or not the pushing force calculated by the pushing force calculating means has reached a predetermined critical pushing force less than a preset target pushing force;
A pushing force control means for controlling the force applying means so that the pushing force converges to the target pushing force when the pushing force judging means determines that the pushing force has reached the critical pushing force; Prepared,
The indentation forming mechanism characterized in that the increase rate control means performs feedback control of the force applying means when the pushing force determining means determines that the pushing force has not reached the critical pushing force . An indentation formation mechanism used in a testing machine that measures material properties of a sample based on forming an indentation on the sample surface with an indenter,
A force applying means for applying a force for applying an indentation force to the indenter to form an indentation on the sample surface;
An elastic member for transmitting the force applied by the force applying means to the indenter;
Elastic displacement amount detecting means for detecting an elastic displacement amount of the elastic member;
An increasing rate calculating means for calculating an increasing rate of the pushing force acting on the indenter based on a change in a detection result of the elastic displacement detecting means;
Based on a comparison between the increase rate calculated by the increase rate calculation means and a preset target increase rate, an increase rate that feedback-controls the force applying unit so that the increase rate follows the target increase rate Control means;
An intrusion amount detecting means for detecting an intrusion amount of the indenter into the sample;
An intrusion amount determination means for determining whether or not the intrusion amount detected by the intrusion amount detection means has reached a predetermined critical intrusion amount less than a preset limit intrusion amount;
An intrusion amount control means for controlling the force applying means so that the intrusion amount converges to the limited intrusion amount when the intrusion amount is determined to have reached the critical intrusion amount by the intrusion amount determination means; With
The indentation forming mechanism characterized in that the increase rate control means performs feedback control of the force applying means when the penetration amount determination means determines that the penetration amount has not reached the critical penetration amount . The indentation formation mechanism according to claim 1 or 2,
The increase rate calculation means is based on a difference between a detection result of the elastic displacement amount detection means at an arbitrary time point and a detection result of the elastic displacement amount detection means after a predetermined sampling period has elapsed from the time point. An indentation formation mechanism that calculates the rate of increase .   Indentation formation mechanism according to any one of claims 1 to 3,
  Hardness calculation means for calculating the hardness of the sample based on a predetermined measurement result relating to the form of the impression formed on the sample by the indentation formation mechanism;
  A hardness tester characterized by comprising:

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