Thrust testing method of linear motor for Stirling cryocooler

Abstract

The invention relates to the technical field of linear motor detection, in particular to a thrust testing method of a linear motor for a Stirling cryocooler. The thrust testing method of the linear motor for the Stirling cryocooler comprises the following steps that S1, a linear motor testing tool is installed on a supporting base of a linear motor thrust testing device, and it is guaranteed that a mandrel of the linear motor testing tool is in a horizontal state; s2, manually controlling the lead screw sliding table assembly to drive the force sensor to move relative to the linear motor test tool until a tiny gap exists between the force sensor and the mandrel, and skipping the step in the subsequent motor test; and S3, the computer sends an instruction that the lead screw sliding table assembly drives the power sensor to move towards the linear motor testing tool at a low speed and a constant speed to the driver. According to the thrust test method, the instruction sending frequency is greatly reduced, and higher instantaneity is achieved when the amplifier continuously sends the data and the computer continuously reads the serial port data, so that the test efficiency can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of linear motor detection, and in particular to a thrust testing method for a linear motor used in a Stirling refrigerator. Background Art

[0002] The linear motor used in a Stirling refrigerator is specifically used in its linear compressor to drive the compressor piston. It adopts an opposed structure, with two linear motors on each side. The compressor piston is connected to the linear motor rotor and supported by a spring. Therefore, the symmetry of the left and right motors greatly affects the inherent vibration of the entire machine. Since it is difficult to achieve complete symmetry in linear motors at the current level, the main method currently used by Stirling refrigerator manufacturers is to select a pair of motors with the closest performance from a batch of motors for adjustment. Originally, a spring tension and compression testing machine was purchased for testing. The method required marking the equilibrium position of the motor in the horizontal position with a marker pen, then vertically balancing it and passing a small current to achieve the equilibrium position before testing. The equilibrium position marking and passing a small current to find the equilibrium position cannot completely avoid the problem of poor test thrust consistency caused by human visual errors, which increases the difficulty of subsequent screening of complete machine units.

[0003] Chinese invention patent application number "202410633882.9" describes a method for testing the thrust of a linear motor. The method specifically includes the following steps: Step 1: Install the linear motor test fixture onto the support base of the thrust test device, ensuring that the core shaft of the linear motor test fixture is in a horizontal state, and the mover is in its initial state. Step 2: Control the screw slide assembly with the force sensor to move toward the linear motor test fixture at a set step distance. Each movement reads the force sensor value F and determines the relationship between the force sensor value F and the set upper threshold value. If the force sensor value F is greater than or equal to the set upper threshold value, it indicates that the force sensor and the end of the core shaft meet the contact condition. If the force sensor value F is less than the set upper threshold value, the screw slide assembly is controlled to continue moving the force sensor toward the linear motor test fixture until the contact condition is met. Step 3: When the force sensor and the end of the core shaft meet the contact conditions, control the screw slide assembly with the power sensor to move in the direction away from the linear motor test fixture according to the set step distance two, read the force sensor value F and judge the relationship between the force sensor value F and the set threshold; if the force sensor value F falls within the set threshold (excluding the threshold boundary), it indicates that the force sensor and the end of the core shaft have just contacted; if the force sensor value F is greater than or equal to the upper limit of the set threshold, control the screw slide assembly with the power sensor to move again in the direction away from the linear motor test fixture by the set step distance two, the set step distance two is less than the set step distance one, then read the force sensor value and judge the relationship between the force sensor value and the set threshold again, if the force sensor value is still greater than or equal to the upper limit of the set threshold at this time, control the screw slide assembly with the power sensor to move again in the direction away from the linear motor test fixture by the set step distance two until the force sensor value falls within the set threshold. If the force sensor value is less than the lower threshold, the screw slide assembly with the force sensor is controlled to move toward the linear motor test fixture by step three, where step three is half of step two. The force sensor value is then read again and the relationship between the force sensor value and the set threshold is again determined until the force sensor value falls within the set threshold. Step 4: The stator coil is energized and current is input according to the multiple sets of current values. Each time current is input, the force sensor value is recorded. Finally, the multiple sets of force sensor values are inserted into the specific thrust calculation formula to obtain the specific thrust of the linear motor.

[0004] As can be seen, in this technical solution, the computer first needs to issue a movement instruction to the screw slide assembly, controlling the screw slide assembly to move the force sensor once according to the step distance. The computer then reads the value of the force sensor and compares it with the value set in the computer. Based on the comparison result, the next movement direction and step distance of the screw slide assembly are determined. The entire measurement process requires multiple iterations, which is time-consuming and inefficient. Summary of the Invention

[0005] (1) The problem to be solved by the present invention is that the entire measurement process of the above-mentioned thrust test method requires multiple iterations, which is time-consuming, inefficient, requires multiple instructions to be sent, and has long intervals.

[0006] (2) Technical solution

[0007] A method for testing the thrust of a linear motor for a Stirling refrigerator comprises the following steps:

[0008] S1: Install the linear motor test fixture onto the support base of the linear motor thrust test device, ensuring that the core shaft of the linear motor test fixture is in a horizontal state;

[0009] S2: Manually control the screw slide assembly with the force sensor to move relative to the linear motor test fixture until a small gap is formed between the force sensor and the core shaft. This step will be skipped in subsequent motor tests.

[0010] S3: The computer sends a command to the driver to move the screw slide assembly with the power sensor toward the linear motor test fixture at a low and uniform speed;

[0011] S4: While the force sensor is moving, the amplifier of the force sensor sends the measured data to the serial port IO buffer at set intervals, and the computer reads the character string in the IO buffer in real time and converts it into a test value. The test value is then compared with the stop threshold. If the read test value is greater than the stop threshold, the computer sends a stop command to the lead screw slide assembly; if the test value is less than the stop threshold, the computer continues to read the character string in the serial port IO buffer and converts it into a test value until the read test value is greater than the stop threshold.

[0012] After the screw slide assembly stops, the force sensor just contacts the end of the core shaft;

[0013] S5: The stator coil is energized and current is input according to the set multiple sets of current values. Each time the current is input, the value of the force sensor is recorded. Finally, the obtained multiple sets of force sensor values are inserted into the specific thrust calculation formula to obtain the specific thrust of the linear motor.

[0014] S6: The computer controls the screw slide assembly with the power sensor to move 0.5 mm away from the linear motor test fixture, and then starts testing the next motor from step S1.

[0015] According to one embodiment of the present invention, the setting range in step S2 is 0.5 mm-1 mm.

[0016] According to one embodiment of the present invention, in the step S3, when the computer controls the screw slide assembly with the power sensor to move at a low and uniform speed toward the linear motor test fixture, the screw slide assembly with the power sensor is set to move at a uniform speed at the lowest speed of the driver.

[0017] According to one embodiment of the present invention, in step S3, while the force sensor is moving, the amplifier of the force sensor sends the measured data to the serial port IO buffer every 14ms-15ms.

[0018] According to one embodiment of the present invention, in step S4, the computer reads the character string in the IO buffer in real time and converts it into a test value, and then compares the test value with the stop threshold, including:

[0019] The computer cyclically queries the number of cache bytes in the serial port IO cache until the number of cache bytes in the serial port IO cache is greater than 10 bytes. The computer reads the string in the serial port IO cache once and converts the first complete frame of multiple data into a force sensor test value. The force sensor test value is compared with the stop threshold.

[0020] According to an embodiment of the present invention, the stopping threshold is 0.01-0.02N.

[0021] According to one embodiment of the present invention, the following steps are further included between steps S4 and S5:

[0022] After the screw stops, the computer reads the buffered data of the serial port IO again, takes the first complete frame of data and converts it into a test value. Then, the test value is compared with the set threshold. If the test value falls within the set threshold, it indicates that the force sensor has just made contact with the end of the core shaft.

[0023] The value within the stop threshold is less than the set lower threshold value.

[0024] According to an embodiment of the present invention, the set threshold is 0.02N-0.05N.

[0025] According to an embodiment of the present invention, in step S4, when the computer reads the character string in the serial port IO buffer, it converts the first complete frame data therein into a test value and compares it with the stop threshold.

[0026] According to one embodiment of the present invention, each time a current is input in step S5, recording the value of the force sensor includes the following steps:

[0027] Clear the IO cache and wait for 300ms-500ms. Then the computer reads the data in the IO cache and converts it into a test value array and takes the last five data to calculate the standard deviation. Then the standard deviation is compared with the set value. If it is less than the set threshold, the average of the five test values is calculated as the value of the force sensor; if it is greater than the set value, the above steps are repeated.

[0028] Beneficial effects of the present invention:

[0029] Compared with the previous thrust testing methods, the thrust testing method of the present invention has the following advantages: First, the thrust testing method greatly reduces the number of times instructions are sent, and the amplifier continuously sends data and the computer cyclically reads serial port data with higher immediacy, thereby effectively improving the test efficiency.

[0030] Second: There is no need to add the operation of screw retraction, the test time is short and the test efficiency is high.

[0031] Third: Each time the power is turned on, the value of the force sensor can be quickly obtained without waiting for 3s-5s, thereby shortening the test time and improving the test efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 A flow chart of the first linear motor thrust testing method provided in the first embodiment of the present invention;

[0034] Figure 2 Flowchart of the residual linear motor thrust testing method provided in Example 1 of the present invention;

[0035] Figure 3 A schematic diagram of a method for obtaining force sensor values by passing current through a stator coil according to a first embodiment of the present invention;

[0036] Figure 4 A structural diagram of a linear motor test fixture provided in Example 2 of the present invention;

[0037] Figure 5 A side view of a linear motor test fixture provided in the second embodiment of the present invention;

[0038] Figure 6 A structural diagram of a thrust testing device for a linear motor for a Stirling refrigerator provided in the second embodiment of the present invention;

[0039] Figure 7 This is a schematic diagram of the connections between the computer, amplifier, force sensor, and stepper motor provided in an embodiment of the present invention.

[0040] Icons: 1. Housing; 2. Linear motor test fixture; 201. First end cover; 202. Second end cover; 203. Stator; 204. Mover; 205. Core shaft; 206. Linear motion ball bearing; 207. Bolt; 208. Spring; 209. Nut; 210. Fixing ring; 211. U-shaped notch; 3. Slider; 4. Stepper motor; 5. Column; 6. Force sensor; 7. Laser displacement sensor; 8. Support plate; 9. Amplifier; 10. Computer. DETAILED DESCRIPTION

[0041] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0042] Example 1:

[0043] like Figure 1 As shown, the first embodiment of the present invention provides a method for testing the thrust of a linear motor for a Stirling refrigerator, comprising the following steps:

[0044] Step 1: Install the linear motor test fixture 2 onto the support base of the linear motor thrust test device, ensuring that the core shaft 205 of the linear motor test fixture 2 is in a horizontal state.

[0045] Step 2: Before testing the first motor, confirm that there is only a small gap (less than 1 mm) between the force sensor 6 and the end of the core shaft 205. If the gap is too large, manually control the screw slide assembly with the force sensor 6 to move relative to the linear motor test fixture 2 until a small gap is visible between the force sensor 6 and the core shaft 205. Skip this step for subsequent motor tests.

[0046] The small gap is about 0.5 mm to 1 mm, preferably 0.5 mm. The purpose of this step is to quickly move the force sensor 6 close to the core shaft 205 in the linear motor test fixture 2 to shorten the test time.

[0047] Step 3: The computer 10 sends an instruction to the driver for the screw slide assembly with the power sensor 6 to move at a low and uniform speed toward the linear motor test fixture 2.

[0048] In this embodiment, the computer 10 controls the screw slide assembly to move the power sensor 6 toward the linear motor test fixture 2 at a uniform speed at the lowest speed. The lowest speed of the screw slide assembly in this embodiment is 0.125 mm / s.

[0049] Step 4: While the force sensor 6 is moving, the amplifier 9 of the force sensor 6 continuously sends the measured data to the serial port IO buffer at set intervals. The computer 10 continuously reads the character string in the serial port IO buffer and converts it into a test value F. The test value F is then compared with the stop threshold. If the read test value F is greater than the stop threshold, the computer 10 sends a stop command to the lead screw slide assembly to the driver; if the test value F is less than the stop threshold, the computer 10 continues to read the character string in the serial port IO buffer and converts it into a test value F until the read test value F is greater than the stop threshold.

[0050] In some embodiments, the amplifier 9 of the force sensor 6 sends the measured data to the serial port IO buffer every 14ms-15ms, preferably every 15ms.

[0051] It should be noted that in this embodiment, the baud rate is 9600, which translates to 9600 bits / second. Since 1 byte equals 10 bits, the speed is 960 bytes / second. Assuming a data frame consists of 12 bytes, the time required for amplifier 9 to transmit a 12-byte data frame is 12 / 960 = 0.0125 seconds, or 12.5 milliseconds. Therefore, to prevent data frame loss, amplifier 9 maintains a transmission interval of at least 12.5 milliseconds. The baud rate can be increased to shorten this interval, achieving even higher real-time performance. For example, if the baud rate is set to 19200, the time required for 12 bytes is 0.0625 seconds, or 6.25 milliseconds, and the transmission interval can be set to 7 seconds.

[0052] After the screw slide assembly stops, the force sensor 6 just contacts the end of the core shaft 205;

[0053] In some embodiments, the stopping threshold is 0.01N-0.02N, preferably 0.01N.

[0054] The computer 10 continuously reads the character string buffered by the serial port IO, and compares the value of the force sensor 6 with the stop threshold each time the reading is performed, including:

[0055] The computer 10 cyclically queries the cache byte number N of the serial port IO until N is greater than 10 bytes. Then the computer 10 reads the character string in the serial port IO cache once and converts the first complete frame into the force sensor 6 test value F and compares it with the stop threshold.

[0056] It should be noted that the amplifier 9 in this embodiment uses an internal timer to trigger data acquisition every 15ms, converting the analog signal into a digital signal (ADC), encapsulating it into a serial data frame, and sending the data bit by bit to the serial port 10 at the configured baud rate (9600bps). The computer 10 uses a while loop to continuously query the number of bytes in the serial port buffer.

[0057] Step 5: After the lead screw stops, the computer 10 reads the cached data of the serial port IO again, takes the first complete frame of data and converts it into a test value, and then compares the test value with the set threshold. If the test value falls within the set threshold, it indicates that the force sensor 6 has just contacted the end of the core shaft 205.

[0058] Among them, the threshold is set to 0.02N-0.05N.

[0059] It should be noted that, in this embodiment, the reason for setting the stop threshold to 0.01N is that: after the computer 10 sends a stop command to the screw slide assembly, it takes a certain amount of time for the screw slide assembly to stop completely from receiving the stop command, and an excessively large stop threshold will cause the value of the force sensor 6 to be greater than 0.05N after the screw slide assembly stops. Therefore, it is necessary to add the operation of retracting the screw, which will extend the test time and reduce the efficiency.

[0060] Specifically, in this embodiment, a lead screw with a lead of 5 mm is used, and it moves at a minimum speed of 0.025 revolutions per second, that is, it moves at a speed of 5*0.025=0.125 mm / s. The stop response time of the lead screw is 100 ms. Therefore, from the time the stop command is received to the time the lead screw stops completely, the additional distance moved by the force sensor 6 is 0.125X0.1=0.0125 mm, and the additional force of the force sensor 6 moving 0.0125 mm is 0.01 N.

[0061] For ease of understanding, assume that the value of force sensor 6 when read by computer 10 is 0.015N. Since 0.015N is greater than the stop threshold (0.01N), computer 10 sends a stop command to the driver toward the screw slide assembly. From the time the stop command is received to the time the screw stops completely, force sensor 6 moves an additional 0.0125mm, and the force value may increase by 0.01N. The actual force sensor 6 data is 0.015N+0.01N=0.025N, which just falls within the set threshold of 0.02N-0.05N. This does not require the operation of increasing the screw back, shortens the test time, and increases the test efficiency. After multiple verifications without problems, it can be considered that the force value after stopping is within the set threshold range, and there is no need to read the force value again. Subsequent motor tests can skip this step.

[0062] Step 6: The stator coil is energized and current is input according to the set multiple sets of current values. Each time current is input, the value of the force sensor 6 is recorded. Finally, the obtained multiple sets of force sensor 6 values are inserted into the specific thrust calculation formula to obtain the specific thrust of the linear motor.

[0063] Step 7: The computer controls the stepper screw assembly to move the sensor backward 0.5 mm, and the next motor is tested from the first step.

[0064] It should be noted that if Figure 2 As shown, after each current input, the IO cache is cleared and waited for 300ms-500ms, then the computer 10 reads the data in the IO cache and takes the last five data to calculate the standard deviation, and then compares the standard deviation with the set value. If it is less than the set value, the average value of the five data is calculated as the value of the force sensor 6; if it is greater than the set value, the above steps of clearing the cache, waiting for 300ms-500ms, calculating the standard deviation, and comparing the standard deviation with the set value are repeated until the standard deviation is less than the set value.

[0065] It is worth noting that in the previous test method, each time the stator coil is energized, it is necessary to wait for the force value to stabilize after the power is turned on (usually it takes 3s-5s to wait), and the computer 10 sends a force value reading instruction and then reads the force value, which takes a long time. Different from this, in the present application, after each current is input, a While loop is added, the IO cache is cleared in the loop and waits for 500ms, and then the computer 10 reads the data in the IO cache and takes the last five data to calculate the standard deviation until the standard deviation is less than 0.02, which indicates that the data is stable. When the standard deviation is small, it means that most of the data points are close to the average value, and the data is more representative. The average value of these five data is then calculated as the value of the force sensor 6. In this way, after each power-on, there is no need to wait 3s-5s to quickly obtain the value of the force sensor 6, thereby shortening the test time and improving the test efficiency.

[0066] In summary, compared with previous thrust test methods, the thrust test method of the linear motor for Stirling refrigerator greatly reduces the time and number of device communications, and is more efficient and faster.

[0067] As a specific embodiment, the thrust test method of the linear motor for Stirling refrigerator is as follows. When the first motor is tested:

[0068] Step 1: Install the first linear motor test fixture 2 onto the support base of the linear motor thrust test device, ensuring that the core shaft 205 of the linear motor test fixture 2 is in a horizontal state.

[0069] Step 2: Confirm that there is a small, visible gap between the force sensor 6 and the end of the mandrel 205. If the gap is too large, manually control the screw slide assembly with the force sensor 6 to move relative to the linear motor test fixture 2 until a small, visible gap exists between the force sensor 6 and the end of the mandrel 205.

[0070] Step 3: The computer 10 sends an instruction to the driver to move the screw slide assembly with the power sensor 6 toward the linear motor test fixture 2 at a minimum speed of 0.125 mm / s.

[0071] Step 4: While force sensor 6 is moving, amplifier 9 of force sensor 6 sends measured data to the serial port IO buffer every 15ms. Computer 10 cyclically queries the serial port IO buffer byte count N and determines whether the serial port IO buffer byte count N is greater than 10 bytes. Once the serial port IO buffer byte count N is greater than 10 bytes, computer 10 reads the string in the serial port IO buffer once, converts the first complete frame of data into the test value F of force sensor 6, and then compares it with the stop threshold (0.01N). If the test value F of force sensor 6 is greater than the stop threshold, computer 10 program sends a stop command to the screw assembly. If the test value F is less than the stop threshold, computer 10 continues to read the string in the serial port IO buffer and converts it into the force sensor 6 test value F until the force sensor 6 test value F is greater than the stop threshold.

[0072] Step 5: After the lead screw stops, debugging is required for the first motor test (skip this step for subsequent motor tests). The computer 10 reads the cached data of the serial port IO again, converts the data of the first complete frame into the test value F of the force sensor 6, and then compares the test value F of the force sensor 6 with the set threshold (0.02N-0.05N). If the test value F of the force sensor 6 falls within the set threshold, it indicates that the force sensor 6 has just contacted the end of the core shaft 205. Otherwise, the force sensor 6 moves backward a certain distance. This distance needs to be determined by repeated experiments during the first test. In this embodiment, it is usually chosen to move back 0.01mm. Alternatively, the stop threshold value can be reduced to allow the force sensor 6 to stop earlier. In this embodiment, the stop threshold value of 0.01N meets the requirements.

[0073] Step 6: The stator coil is energized and current is input according to the multiple sets of set current values. After each current input, the previous IO buffer is cleared and a wait of 300-500ms is performed. The computer 10 then reads the data in the IO buffer and calculates the standard deviation of the last five data points. This standard deviation is then compared with the set value. If it is less than the set value, the average of these five data points is calculated as the value of force sensor 6. If it is greater than the set value, the above steps of clearing the buffer, waiting 300-500ms, calculating the standard deviation, and comparing the standard deviation with the set value are repeated until the standard deviation is less than the set value. The value of force sensor 6 is then recorded and the multiple sets of force sensor 6 values obtained are finally inserted into the specific thrust calculation formula to obtain the specific thrust of the linear motor.

[0074] The specific thrust calculation formula is: Among them, 1, 2 and N are current values, F1, F2 and F N , which are the values measured by the force sensor 6 when the current is 1A, 2A and NA respectively.

[0075] Step 7: The computer controls the screw assembly to move back 0.5mm, and the next motor is tested from the first step.

[0076] After the first motor test is completed, the subsequent motor thrust test plan follows the process Figure 2 To test:

[0077] Specifically:

[0078] Step 1: Install the linear motor test fixture 2 onto the support base of the linear motor thrust test device, ensuring that the core shaft 205 of the linear motor test fixture 2 is in a horizontal state.

[0079] Step 2: The computer 10 sends an instruction to the driver to move the screw slide assembly with the power sensor 6 toward the linear motor test fixture 2 at a minimum speed of 0.125 mm / s.

[0080] Step 3: While force sensor 6 is moving, amplifier 9 of force sensor 6 sends measured data to the serial port IO buffer every 15ms. Computer 10 cyclically queries the number of bytes N cached in serial port IO and determines whether the number of bytes N cached in serial port IO is greater than 10 bytes, until the number of bytes N cached in serial port IO is greater than 10 bytes. If it is greater than 10 bytes, computer 10 reads the string in serial port IO once, converts the first complete frame of data in the data into the test value F of force sensor 6, and compares it with the stop threshold (0.01N); if the test value F of force sensor 6 is greater than the stop threshold, computer 10 program sends a stop command to the screw assembly to stop the screw; if the test value F is less than the stop threshold, computer 10 continues to read the string in serial port IO buffer and converts it into the test value F of force sensor 6 until the test value F of force sensor 6 is greater than the stop threshold.

[0081] Step 4: The stator coil is energized and current is input according to the multiple sets of set current values. After each current input, the previous IO buffer is cleared and a wait of 300-500ms is performed. The computer 10 then reads the data in the IO buffer and calculates the standard deviation of the last five data points. This standard deviation is then compared with the set value. If it is less than the set value, the average of these five data points is calculated as the value of force sensor 6. If it is greater than the set value, the above steps of clearing the buffer, waiting 300-500ms, calculating the standard deviation, and comparing the standard deviation with the set value are repeated until the standard deviation is less than the set value. The value of force sensor 6 is then recorded and the multiple sets of force sensor 6 values are finally inserted into the specific thrust calculation formula to obtain the specific thrust of the linear motor.

[0082] Step 5: The computer controls the screw assembly to move back 0.5mm.

[0083] In summary, the thrust testing method of the present application has the following advantages over previous thrust testing methods:

[0084] First: In the previous thrust test method, the computer 10 first sends a movement instruction to the screw slide assembly, controls the screw slide assembly to move the force sensor 6 once, and then immediately sends a stop instruction to the screw slide assembly. Then the computer 10 reads the value of the force sensor 6 and compares it with the value set in the computer 10. According to the comparison result, the next movement direction and movement distance of the screw slide assembly are determined. Since sending and receiving instructions require time, and the hardware processing instructions also have a response time, sending commands multiple times will result in a long response time for sending and receiving the entire command, reducing the test efficiency. In this application, the screw slide assembly always moves at a low and uniform speed. At the same time, the amplifier 9 sends the measured data to the serial port IO buffer every 15ms. The computer 10 continuously reads the amount of data in the serial port IO buffer and compares the read value of the force sensor 6 with the stop threshold until the read value of the force sensor 6 is greater than the stop threshold. Then the computer 10 sends a stop instruction to the screw slide assembly to the driver. It can be seen that this test method greatly reduces the number of instruction transmissions, and the amplifier 9 continuously sends data and the computer 10 cyclically queries the serial port data with higher immediacy, thus effectively improving the test efficiency.

[0085] Second: In the previous thrust test method, it is inevitable to add the operation of retracting the screw, but in this application, there is no need to add the operation of retracting the screw, the test time is short, and the test efficiency is high.

[0086] Third, in conventional thrust testing methods, each time the stator coil is energized, it takes a long time to wait for the force value to stabilize (usually 3-5 seconds) before the computer 10 sends a force reading instruction and then reads the force value. However, in the present application, after each power-on, the force sensor 6 value can be quickly obtained without waiting for 3-5 seconds, thereby shortening the test time and improving test efficiency.

[0087] Example 2:

[0088] like Figure 4-Figure 7 As shown, the second embodiment of the present invention provides a thrust testing device for a linear motor for a Stirling refrigerator, including a screw slide assembly, a force sensor 6 , a linear motor testing fixture 2 , an amplifier 9 and a computer 10 .

[0089] The lead screw slide assembly includes a slider 3, on the upper surface of which is mounted a vertically arranged column 5 in the shape of a rectangular plate. A horizontally arranged force sensor 6 is mounted on the column 5, perpendicular to the column 5. The slider 3 is used to move the force sensor 6 toward or away from the linear motor test fixture 2. It should be noted that after the linear motor test fixture 2 is mounted on the support base, the core shaft 205 and the force sensor 6 are at the same height.

[0090] Preferably, Figure 4 and Figure 5 As shown, the linear motor test fixture 2 includes a first end cover 201, a second end cover 202, a core shaft 205, a mover 204 and a stator 203, wherein the first end cover 201 and the second end cover 202 have the same structure, and the stator 203 is installed between the first end cover 201 and the second end cover 202. Specifically, Figure 2 From the perspective of , the outer wall of the end stop on the right side of the first end cover 201 is gapped with the inner wall of the left end of the stator 203 and is close to the left end face of the stator 203, and the outer wall of the left end stop of the second end cover 202 is gapped with the inner wall of the right end of the stator 203 and is close to the right end face of the stator 203. A cylindrical cavity is formed between the first end cover 201, the stator 203 and the second end cover 202. The mover 204 is located in the cylindrical cavity, and the mover 204 and the stator 203 are coaxially arranged. When the stator 203 is energized, the mover 204 can move along the axis of the cylindrical cavity. A circular hole for the core shaft 205 to pass through is provided at the center of the first end cover 201 and the second end cover 202.

[0091] The core shaft 205 is installed in the stator 203 and is coaxial with the stator 203 . One end of the core shaft 205 passes through the circular hole of the first end cover 201 , and the other end of the core shaft 205 passes through the circular hole of the second end cover 202 .

[0092] It should be noted that when installing the core shaft 205, first insert the core shaft 205 into the center hole of the mover 204, the mating surface of the core shaft 205 is clearance-matched with the inner hole of the mover 204, the step surface of the core shaft 205 is tightly attached to the step surface of the center hole of the mover 204, and the outside is locked with a locking nut.

[0093] Preferably, in order to reduce the friction between the core shaft 205 and the two end covers and reduce the influence of friction on the thrust test results of the linear motor, linear motion ball bearings 206 are installed in the circular holes of the first end cover 201 and the second end cover 202.

[0094] Preferably, Figure 5 As shown, a fixing ring 210 is provided on the outer wall of the first end cover 201 and the second end cover 202. The fixing ring 210 is a circular ring and is coaxially arranged with the end cover. A plurality of U-shaped notches 211 are evenly opened on the fixing ring 210 around its axis.

[0095] In this way, when assembling the linear motor test fixture 2, first assemble the core shaft 205 and the mover 204, then insert the mover 204 into the stator 203, and then put the first end cover 201 on the core shaft 205 from the left end, and match it with the left end stop of the stator 203, then put the second end cover 202 on the core shaft 205 from the right end, and match it with the right end stop of the stator 203, finally use the bolt 207 to pass through a U-shaped notch 211 of the first end cover 201, and the bolt 207 passes through the U-shaped notch 211 corresponding to the second end cover 202, and finally use the nut 209 to lock it.

[0096] Optionally, considering that after the first end cover 201 and the second end cover 202 are connected using the bolt 207 and the nut 209, it is difficult to loosen the nut 209 when it is locked during subsequent disassembly, making disassembly more troublesome.

[0097] Therefore, if Figure 4 As shown, a spring 208 is inserted into the bolt 207, and the bolt 207 and the spring 208 are pressed against the U-shaped notch 211 of the first end cover 201. At the same time, the bolt 207 passes through the U-shaped notch 211 of the second end cover 202. Then, the nut 209 is screwed onto the bolt 207 so that the spring 208 has a suitable pre-tightening force. Finally, the nut 209 is welded or bonded to the end of the bolt 207.

[0098] During subsequent disassembly, first push the bolt 207 to tighten the spring 208, and then move the bolt 207 to the right to separate the nut 209 from the fixing ring 210 of the second end cover 202. Finally, directly remove the bolt 207.

[0099] During subsequent assembly, first insert the end of the bolt 207 with the spring into the U-shaped notch 211 of the first end cover 201 at an angle, then push the bolt 207 to compress the spring 208, and finally insert the end of the bolt 207 with the nut 209 into the U-shaped notch 211 of the second end cover 202. Finally, loosen the bolt 207. Under the resetting action of the spring 208, the end of the bolt 207 with the nut 209 can be tightly against the U-shaped notch 211 of the second end cover 202, which reduces the time for tightening the screws and greatly improves the assembly efficiency.

[0100] It should be noted that the rotation of the stepper motor 4 in the lead screw slide assembly causes the slider 3 to move, and the movement direction is related to the rotation direction of the stepper motor 4 (when the stepper motor 4 rotates clockwise, the slider 3 moves to the right, and vice versa, it moves to the left. Its movement speed is related to the lead of the lead screw slide.

[0101] Preferably, Figure 6As shown, a support base is mounted on the housing 1 for mounting the linear motor test fixture 2. Specifically, the support base includes two support plates 8. The bottom of the support plate 8 is in an inverted U-shape, which facilitates spanning the housing 1. The support plate 8 has an arcuate groove near the top for accommodating the linear motor test fixture 2. A plurality of screw holes for mounting ball spring screws are provided on the support plate 8 near the force sensor 6.

[0102] Furthermore, only the left support plate 8 is installed with a ball-shaped spring screw, and the ball of the ball-shaped spring screw exceeds the right end surface of the left support plate 8. In this way, when the linear motor test tool 2 is placed in, the ball-shaped spring screw will be compressed, so that the linear motor test tool 2 is pressed against the right, ensuring that the linear motor test tool 2 will not be displaced during the test, and the subsequent disassembly of the linear motor test tool 2 is also very convenient.

[0103] When installing the linear motor test fixture 2 on the support seat, first place the linear motor test fixture 2 horizontally on the two support plates 8. The first end cover 201 on the linear motor test fixture 2 compresses the ball spring screw, and the ball spring screw gives the linear motor test fixture 2 a rightward force, so that the linear motor test fixture 2 is fastened between the two support plates 8. Due to the pre-tightening of the ball spring screw, the linear motor test fixture 2 will not move left and right, and the ball spring screw does not need to be tightened every time. Once adjusted, there is no need to adjust it again. In this way, the linear motor test fixture 2 can be firmly fixed on the support seat, the linear motor test fixture 2 will not shake, and the subsequent disassembly of the linear motor test fixture 2 is also very convenient.

[0104] It should be noted that the distance between the left side of the fixing ring 210 of the first end cover 201 in the linear motor test fixture 2 and the right side of the fixing ring 210 on the second end cover 202 is slightly smaller than the distance between the two support plates 8. In this way, when the linear motor test fixture 2 is placed between the two support plates 8, the right fixing ring 210 in the linear motor test fixture 2 is tightly attached to the inner side surface of the right support plate 8.

[0105] It should be noted that the thrust testing device for the linear motor further includes a DC power supply, which is connected to the coil on the stator 203 .

[0106] Preferably, in this embodiment, the stepper motor 4 is connected to the computer 10 via a signal connection, the force sensor 6 is electrically connected to the amplifier 9, and the amplifier 9 is connected to the computer 10 via a serial port RS485 signal connection.

[0107] For the convenience of description, Figure 6 The support plate 8 close to the slider 3 is named as the first support plate, and the support plate 8 far from the slider 3 is named as the second support plate.

[0108] Optionally, a laser displacement sensor 7 is installed on the slider 3, and the laser displacement sensor 7 points to the left end face of the first support plate. The laser displacement sensor 7 is connected to the control module signal in the computer 10. It should be noted that after the linear motor test fixture 2 is installed on the support seat, the distance between the left end face of the core shaft 205 of the linear motor and the left end face of the first support plate is fixed, and the horizontal distance between the right end face of the force sensor 6 and the laser displacement sensor 7 is also fixed. Therefore, when the laser displacement sensor 7 moves to the right to the set position, the force sensor 6 can be just 0.5mm away from the left end face of the core shaft 205. By using the laser displacement sensor 7 in conjunction with the screw slide assembly, the force sensor 6 can be quickly moved to just 1mm away from the left end face of the core shaft 205.

[0109] In addition, the laser displacement sensor 7 may not be used, and the distance between the force sensor 6 and the end of the core shaft 205 may be observed by human eyes, or the force sensor 6 may be brought close to the end of the core shaft 205 by controlling the movement stroke of the screw slide assembly.

[0110] In the description of the present invention, it should be noted that the terms "upper" and "lower" and other terms indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0111] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium, or they can refer to connections between the internal parts of two components. A person of ordinary skill in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for testing the thrust of a linear motor for a Stirling refrigerator, characterized in that: The steps include: S1: Install the linear motor test fixture onto the support base of the linear motor thrust test device, ensuring that the core shaft of the linear motor test fixture is in a horizontal state; S2: Manually control the screw slide assembly with the force sensor to move relative to the linear motor test fixture until a small gap is formed between the force sensor and the core shaft. This step will be skipped in subsequent motor tests. S3: The computer sends a command to the driver to move the screw slide assembly with the power sensor toward the linear motor test fixture at a low and uniform speed; S4: While the force sensor is moving, the amplifier of the force sensor sends the measured data to the serial port IO buffer at set intervals, and the computer reads the character string in the IO buffer in real time and converts it into a test value. The test value is then compared with the stop threshold. If the read test value is greater than the stop threshold, the computer sends a stop command to the lead screw slide assembly; if the test value is less than the stop threshold, the computer continues to read the character string in the serial port IO buffer and converts it into a test value until the read test value is greater than the stop threshold. After the screw slide assembly stops, the force sensor just contacts the end of the core shaft; S5: The stator coil is energized and current is input according to the set multiple sets of current values. Each time the current is input, the value of the force sensor is recorded. Finally, the obtained multiple sets of force sensor values are inserted into the specific thrust calculation formula to obtain the specific thrust of the linear motor. S6: The computer controls the screw slide assembly with the power sensor to move 0.5 mm away from the linear motor test fixture, and then starts testing the next motor from step S1.

2. The method for testing the thrust of a linear motor for a Stirling refrigerator according to claim 1, wherein: The setting range in step S2 is 0.5 mm to 1 mm.

3. The method for testing the thrust of a linear motor for a Stirling refrigerator according to claim 1, wherein: In the step S3, when the computer controls the screw slide assembly with the power sensor to move at a low and uniform speed toward the linear motor test fixture, the screw slide assembly with the power sensor is set to move at a uniform speed at the lowest speed of the driver.

4. The method for testing the thrust of a linear motor for a Stirling refrigerator according to claim 3, wherein: In step S3, while the force sensor is moving, the amplifier of the force sensor sends the measured data to the serial port IO buffer every 14ms-15ms.

5. The method for testing the thrust of a linear motor for a Stirling refrigerator according to claim 1, wherein: In step S4, the computer reads the character string in the IO buffer in real time and converts it into a test value, and then compares the test value with the stop threshold, including: The computer cyclically queries the number of cache bytes in the serial port IO cache until the number of cache bytes in the serial port IO cache is greater than 10 bytes. The computer reads the string in the serial port IO cache once and converts the first complete frame of multiple data into a force sensor test value. The force sensor test value is compared with the stop threshold.

6. The method for testing the thrust of a linear motor for a Stirling refrigerator according to claim 5, wherein: The stopping threshold is 0.01-0.02N.

7. The method for testing the thrust of a linear motor for a Stirling refrigerator according to claim 6, wherein: The following steps are included between steps S4 and S5: After the screw stops, the computer reads the buffered data of the serial port IO again, takes the first complete frame of data and converts it into a test value. Then, the test value is compared with the set threshold. If the test value falls within the set threshold, it indicates that the force sensor has just made contact with the end of the core shaft. The value within the stop threshold is less than the set lower threshold value.

8. The method for testing the thrust of a linear motor for a Stirling refrigerator according to claim 7, wherein: The set threshold is 0.02N-0.05N.

9. The method for testing the thrust of a linear motor for a Stirling refrigerator according to claim 1, wherein: In step S4, when the computer reads the character string in the serial port IO buffer, it converts the first complete frame data therein into a test value and compares it with the stop threshold.

10. The method for testing the thrust of a linear motor for a Stirling refrigerator according to claim 1, wherein: Each time a current is input in step S5, recording the value of the force sensor includes the following steps: Clear the IO cache and wait for 300ms-500ms. Then the computer reads the data in the IO cache and converts it into a test value array and takes the last five data to calculate the standard deviation. Then the standard deviation is compared with the set value. If it is less than the set threshold, the average of the five test values is calculated as the value of the force sensor; if it is greater than the set value, the above steps are repeated.

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