Electronic Control Unit

Abstract

To provide an electronic controller capable of starting a pump motor as quickly as possible according to the characteristics of a motor or urea water.SOLUTION: According to an electronic controller, a microcomputer performs testing of confirming the turning operation of a pump motor before starting pressure control by PWM-controlling the driving of a pump motor for the pressure control of urea piping (S4). Forced commutation processing is subsequently carried out in such a manner that the rotation number of the motor is made to reach the target rotation number when performing the pressure control (S11). Then, during the testing, the microcomputer compares the rotation number detected when driving the pump motor by a PWM signal of a testing drive duty ratio with the reference rotation number corresponding to the PWM signal of the testing drive duty ratio to correct a forced commutation duty ratio according to results obtained by the foregoing comparison S9).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electronic control device for controlling a pump motor for controlling the pressure in a urea pipe. [Background technology]

[0002] In order to improve purification performance, urea SCR (Selective Catalytic Reduction) systems used in vehicle exhaust gases, etc., are required to increase pipe pressure in a short time after startup so that urea water can be injected.To achieve this, it is important to start the motor for the pump that pumps the urea water at high speed for a short time, and ideally, the motor should be operated at a speed close to the rated speed immediately after startup.

[0003] However, if the motor or urea water characteristics change due to temperature changes, etc., the motor speed will change even if the motor is driven with the same duty ratio during PWM control. Therefore, under conditions of motor / urea water characteristics that result in a high rotation speed, overspeed during forced commutation may exceed the rated motor speed. To avoid this situation, the target rotation speed immediately after startup must be set lower than the rated rotation speed, which increases the time it takes to reach a high rotation speed after startup. On the other hand, under conditions of motor / urea water characteristics that result in a low rotation speed, the rotation speed does not rise to the target rotation speed during forced commutation, and the time it takes to reach the target rotation speed increases. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-48328 A [Patent Document 2] JP 2008-148379 A Summary of the Invention [Problem to be solved by the invention]

[0005] Both Patent Documents 1 and 2 are techniques for starting a motor in a short time. The method disclosed in Patent Document 1 can correct the duty difference of the inverter circuit, but cannot correct the fluctuation due to the change in the characteristics of the motor or the urea water. In addition, as disclosed in Patent Document 2, if a method is used in which the current limit level during forced commutation is increased to allow a large current to flow, it is possible to start the motor at a high rotation speed. However, since the motor / urea water characteristics that result in the above-mentioned high rotation speed exceed the rated rotation speed, the current limit must be set according to the motor / urea water characteristics that result in a high rotation speed, and the time required to reach the target rotation speed cannot be shortened at a target rotation speed close to the rated rotation speed.

[0006] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide an electronic control device that can start a pump motor in the shortest possible time in accordance with the characteristics of the motor and urea water. [Means for solving the problem]

[0007] According to the electronic control device of claim 1, the control unit performs PWM control of the drive of the pump motor for controlling the pressure in the urea pipe, and performs forced commutation processing so that the rotation speed of the pump motor reaches the target rotation speed.

[0008] And the control unit: Before the forced commutation process During a test period, the rotation speed detected when the pump motor is driven by a PWM signal of a test drive duty ratio is compared with a reference rotation speed corresponding to the PWM signal of the test drive duty ratio, and the forced commutation duty ratio of the PWM signal set during forced commutation processing is corrected according to the comparison result. With this configuration, the forced commutation duty ratio can be appropriately corrected according to the detected pump motor rotation speed during the test period, making it possible to start the pump motor in the shortest possible time without exceeding the rated rotation speed. [Brief description of the drawings]

[0009] [Figure 1]1 is a flowchart illustrating a start-up control process for a pump motor according to a first embodiment. [Diagram 2] Flowchart showing the forced commutation duty correction process [Diagram 3] Timing chart showing pump motor start control [Figure 4] Diagram equivalent to Figure 3 when the forced commutation duty ratio is not corrected [Diagram 5] A diagram showing the configuration of an electronic control device. [Figure 6] 11 is a flowchart showing the content of forced commutation duty correction processing according to the second embodiment. [Figure 7] 11 is a flowchart showing the content of forced commutation duty correction processing according to the third embodiment. [Figure 8] Timing chart showing pump motor start control [Figure 9] 13 is a flowchart showing the content of forced commutation duty correction processing according to the fourth embodiment. [Figure 10] FIG. 13 is a diagram showing the relationship between the rotation speed and the drive duty ratio when the motor characteristics are ideal. [Figure 11] Figure 10: Equivalent diagram to actual motor characteristics [Figure 12] Diagram explaining the procedure for correcting the forced commutation duty ratio (part 1) [Figure 13] Diagram explaining the procedure for correcting the forced commutation duty ratio (part 2) [Figure 14] Diagram explaining the procedure for correcting the forced commutation duty ratio (part 3) [Figure 15] FIG. 13 is a timing chart showing a start-up control of a pump motor according to a fifth embodiment. [Figure 16] Flowchart showing the forced commutation duty correction process [Figure 17] A diagram explaining the process of correcting the forced commutation duty ratio by linear interpolation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (First embodiment) As shown in Fig. 5, an electronic control device 1 of this embodiment performs PWM (Pulse Width Modulation) control of the drive of a three-phase brushless DC motor 2. The motor 2 is a pump motor for controlling the pressure of a urea pipe in a urea SCR system applied to vehicle exhaust gas. The electronic control device 1 includes a microcomputer 3, a control IC 4, and an inverter circuit 5. The inverter circuit 5 is configured by connecting N-channel MOSFETs 6, which are switching elements, in a three-phase bridge configuration. Three FETs 6H on the power supply side are high-side switches, and three FETs 6L on the ground side are low-side switches.

[0011] A resistor 7 is connected between the power supply VB and the drain of the FET 6H, and the power supply VB is connected to an input terminal of the microcomputer 3 via a resistor 8. A resistor 9 and a capacitor 10 are connected in parallel between the input terminal and the ground. The microcomputer 3 detects the voltage of the power supply VB by a value obtained by dividing the voltage by the resistors 8 and 9. A resistor 11 is connected between the source of the FET 6L and the ground, and both ends of the resistor 11 are connected to the input terminal of the microcomputer 3 via resistors 12 and 13, respectively. A capacitor 14 is connected between these input terminals. The microcomputer 3 detects the terminal voltage of the resistor 11 to detect the current flowing through the inverter circuit 5.

[0012] The microcomputer 3, which corresponds to the control unit, inputs voltage command values ​​for each of the U, V, and W phases to the control IC 4, which generates a PWM signal for each phase by comparing the voltage command values ​​with the voltage of the carrier signal. The PWM signal is input to the gate of each FET 6.

[0013] Each phase output terminal of the inverter circuit 5 is connected to the other end of each phase coil 15U, 15V, 15W, which has one end of the motor 2 commonly connected, via the U-, V-, and W-phase terminals of the electronic control device 1. The U-, V-, and W-phase terminals are each connected to an input terminal of the control IC 4. In addition, a series circuit of resistor elements 16 and 17 is connected in parallel to the inverter circuit 5, and their common connection point is connected to the input terminal of the control IC 4. The control IC 4 compares each phase terminal voltage of the motor 2 with the midpoint voltage of the power supply VB divided by the resistor elements 16 and 17, and inputs a rotor position signal of the motor 2 to the microcomputer 3. The microcomputer 3 performs position sensorless control of the motor 2 based on the input rotor position signal.

[0014] A sensor signal from a temperature sensor 18 that detects the temperature of a urea water tank (not shown) is input to the microcomputer 3. The microcomputer 3 controls the supply of electricity to a heater 19 that is disposed to heat the motor 2, the urea pipe, the urea tank, etc.

[0015] Next, the operation of this embodiment will be described. As shown in Fig. 1, when the microcomputer 3 starts the start determination of the urea pump motor 2 (S1), if the temperature of the urea water is below 0°C (S2; Yes), it energizes the heater 19 to perform thawing control (S3), and if the temperature is higher than 0°C (No), it rotates the motor 2 and performs testing to check its operation in advance (S4). During the testing, which corresponds to the test period, a PWM signal with a test drive duty ratio set for the test is output to rotate the motor 2.

[0016] Next, the rotation speed of motor 2 detected during testing is compared with the abnormality determination rotation speed (S5). The abnormality determination rotation speed is a rotation speed that is set to determine whether motor 2 is not rotating normally due to freezing or the like. If it is less than the abnormality determination rotation speed (No), the number of times thawing control has been performed is determined (S6), and if it is equal to or greater than the abnormality determination rotation speed (Yes), the abnormality determination current is determined (S8). In step S6, if the number of times thawing control has been performed is two or less, thawing control (S3) is performed again, and if it has been three times, it is determined that a motor abnormality has occurred (S7) and control ends.

[0017] In step S8, the motor current detected during testing is compared with the abnormality determination current value, and if it is greater than the abnormality determination current value (No), the process proceeds to step S7, and if it is equal to or less than the abnormality determination current value (Yes), the process corrects the duty ratio during forced commutation (S9).

[0018] Then, the motor is forcibly commutated with the corrected forced commutation duty ratio to start the motor (S10), and the process transitions to rotation speed feedback control, where the PWM duty that drives motor 2 is continuously changed so that the pump does not step out, and the target rotation speed is controlled (S11). Then, immediately after the target rotation speed is reached, motor 2 is rotated at high speed to rapidly increase the pressure, and when the pressure starts to rise, the rotation speed is reduced, and the rotation speed is adjusted to reach the target pressure, and thereafter the rotation speed is controlled so that the pressure is maintained (S12).

[0019] 2, in the forced commutation duty correction process in step S9, the rotation speed of the motor 2 detected during testing is compared with a value obtained by multiplying a reference rotation speed corresponding to the test drive duty ratio by 1.05 (S21), and if it is equal to or greater than the 1.05 value (Yes), the forced commutation duty ratio is corrected to a value smaller than a predetermined reference duty ratio (S22), and if it is smaller than the 1.05 value (No), the reference rotation speed is compared with a value obtained by multiplying 0.95 (S23). If it is smaller than the 0.95 value, the forced commutation duty ratio is corrected to a value larger than the reference duty ratio (S24), and if it is equal to or smaller than 0.95, the forced commutation duty ratio is set to the same value as the reference duty ratio (S25).

[0020] Figure 4 is a timing chart of start-up control assuming that only the operation of motor 2 is checked during testing, and forced commutation duty correction processing is not performed. Regardless of the rotation speed detected during testing, the pump motor is forcibly commutated at a preset forced commutation duty ratio, i.e., the reference duty ratio, so in the case of pump / urea water characteristics where the rotation speed during testing is high, overspeeding beyond the rated rotation speed of the motor occurs. Also, in the case of pump / urea water characteristics where the rotation speed during testing is low, with forced commutation, the motor rotation speed does not increase to the target rotation speed, the duty transition time becomes longer, and the time to reach the target rotation speed becomes longer.

[0021] Fig. 3 is a timing chart of start-up control when forced commutation duty correction processing is performed. When testing starts, the motor 2 rotates, but depending on the characteristics of the motor 2 and the urea water, even with the same drive duty ratio, the rotation speed may be equal to the reference rotation speed shown by the solid line, may be higher than the reference rotation speed shown by the dashed line, or may be lower than the reference rotation speed shown by the dashed line.

[0022] The rotation speed value at this time is compared with a reference rotation speed, and if it is within ±5% of the reference rotation speed, it is deemed to be equivalent. If it is higher than the reference rotation speed, the forced commutation duty ratio is corrected to the same value as the reference duty ratio, to a value smaller than the reference duty ratio, and if it is lower than the reference rotation speed, to a value larger than the reference duty ratio.

[0023] After that, when the motor is forcibly commutated with the corrected forced commutation duty, the error from the target rotation speed can be kept small regardless of the characteristics of the motor or urea water by correcting the duty at the testing rotation speed. After forced commutation, rotation speed feedback control is started and a duty transition process is performed that continuously changes the drive duty so that the target rotation speed is reached, and after the target rotation speed is reached, the process transitions to pressure boost and hold control. By keeping the error from the target rotation speed with forced commutation small, the time to reach the target rotation speed is shortened.

[0024] As described above, according to this embodiment, in the electronic control device 1, before starting pressure control by PWM controlling the drive of the pump motor 2 for controlling the pressure in the urea pipe, the microcomputer 3 performs testing to check the rotation operation of the pump motor 2. After that, a forced commutation process is performed so that the rotation speed of the motor 2 reaches the target rotation speed when the pressure control is performed.

[0025] During testing, the microcomputer 3 compares the rotation speed detected when the pump motor 2 is driven by the PWM signal of the test drive duty ratio with the reference rotation speed corresponding to the PWM signal of the test drive duty ratio, and corrects the forced commutation duty ratio according to the comparison result. With this configuration, the forced commutation duty ratio can be appropriately corrected according to the rotation speed of the pump motor 2 detected during testing, making it possible to minimize the time it takes for the rotation speed of the pump motor 2 to reach the target rotation speed, and to control the rotation speed so that it does not exceed the rated rotation speed.

[0026] Second embodiment In the following, the same parts as those in the first embodiment are denoted by the same reference numerals and their explanations are omitted, and only the different parts are explained. As shown in Fig. 6, in the second embodiment, when the microcomputer 3A judges "Yes" in steps S21 and S23 in the forced commutation duty correction process, the forced commutation duty ratio is set to the reference duty ratio multiplied by the ratio between the reference rotation speed and the rotation speed detected during testing (S26).

[0027] When the driving conditions according to the characteristics of the motor 2 and the urea water are the same, there is a linear correlation between the duty ratio in the PWM control and the rotation speed of the motor 2. Therefore, by performing the correction as in the second embodiment, it is possible to suppress the fluctuation in the rotation speed during forced commutation.

[0028] Third embodiment 7, in the third embodiment, when the microcomputer 3B judges "Yes" in steps S21 and S23 in the forced commutation duty correction process, the forced commutation duty ratio is corrected to a value obtained by multiplying the reference duty ratio by a rotation speed correction term corresponding to the difference in the rotation speeds, and by the power supply voltage detected during testing and the power supply voltage detected during forced commutation (S27). When the microcomputer 3B judges "No" in step S23, the forced commutation duty ratio is corrected to a value obtained by multiplying the reference duty ratio by the ratio between the power supply voltage detected during testing and the power supply voltage detected during forced commutation (S28).

[0029] 8 shows a timing chart of start control in the case where correction is made according to the rotation speed and power supply voltage of the motor 2 in the third embodiment. Even if the rotation speed detected during testing is the same, if the power supply voltage drops as shown by the dashed line during subsequent forced commutation, the rotation speed during forced commutation will drop if forced commutation is performed with the same forced commutation duty ratio as when the power supply voltage is constant. Therefore, by correcting the forced commutation duty ratio to a larger value when the power supply voltage is dropping and correcting the forced commutation duty to a smaller value when the power supply voltage is rising, it is possible to suppress fluctuations in the rotation speed during forced commutation even when the power supply voltage fluctuates.

[0030] (Fourth embodiment) As shown in FIG. 9, in the fourth embodiment, when the microcomputer 3C judges “Yes” in steps S21 and S23 in the forced commutation duty correction process, the forced commutation duty is corrected by multiplying a value obtained by subtracting a correction constant from a reference duty ratio by the ratio between a reference rotation speed and the rotation speed detected in testing, and adding the correction constant to the result (S29).

[0031] 10 and 11 are examples of the relationship between the duty ratio of the PWM signal that drives a motor and the motor rotation speed. In a motor with ideal loss-free characteristics as shown in FIG. 10, the relationship between the drive duty ratio and the rotation speed is proportional, but in an actual motor as shown in FIG. 11, the relationship between the drive duty ratio and the rotation speed is linear but not completely proportional. Therefore, the accuracy of the correction can be improved by setting the value of the constant term of the function obtained by linearly regressing the relationship between the drive duty ratio and the rotation speed as a complementary constant and performing a calculation that takes the correction constant into account when correcting the forced commutation duty.

[0032] For example, when the relationship between the duty ratio and the motor rotation speed is a linear function as shown in Fig. 12, by subtracting a value equivalent to the intercept as a correction constant, the relationship between the two becomes proportional as shown in Fig. 13. In this state, the forced commutation duty ratio is corrected from the rotation speed obtained during testing. After correction, the actual forced commutation duty ratio is determined by adding the subtracted correction constant as shown in Fig. 14.

[0033] As described above, according to the fourth embodiment, when the forced commutation duty ratio is corrected, a value corresponding to the intercept in the case where the relationship between the duty ratio and the motor rotation speed is a linear function is subtracted as a correction constant, and the actual forced commutation duty ratio is determined by adding the correction constant after the correction. This makes it easy to perform the correction.

[0034] Fifth embodiment As shown in FIG. 15, in the fifth embodiment, the microcomputer 3D obtains the rotational speeds 1 and 2 by changing the test drive duty ratio, for example, from small to large, during testing. The reference rotational speeds 1 and 2 are determined according to whether the test drive duty ratio is small or large. Then, in step S31 shown in FIG. 16, it is determined whether the rotational speed 1 at the testing rotational speed is 1.05 times the reference rotational speed 1 or less, and the rotational speed 2 at the testing rotational speed is 1.05 times the reference rotational speed 2 or less. If it is determined as "Yes" here, it proceeds to step S33, and it is determined whether the rotational speed 1 at the testing rotational speed is 0.95 times the reference rotational speed 1 or more, and the rotational speed 2 at the testing rotational speed is 0.95 times the reference rotational speed 2 or more. If it is determined as "Yes" here, it proceeds to step S25.

[0035] If the determination in step S31 or S33 is "No", the forced commutation duty ratio is corrected as follows (S32): "Testing duty ratio" is a test drive duty ratio. (Forced commutation duty ratio) = (Target RPM - Testing RPM 2) ×{(Testing duty ratio 2)-(Testing duty ratio 1)} / {(Testing rotation speed 2)-(Testing rotation speed 1) + (Testing duty ratio 2)}

[0036] That is, as shown in FIG. 17, by obtaining testing rotation speeds 1 and 2 corresponding to testing duty ratios 1 and 2, the forced commutation duty ratio corresponding to the target rotation speed is calculated by linear interpolation.

[0037] As described above, according to the fifth embodiment, the microcomputer 3D changes the test drive duty ratio to a plurality of values ​​during testing, detects the rotation speed of the pump motor corresponding to each test drive duty ratio, and determines whether or not to correct the forced commutation duty ratio according to the value of the rotation speed. When correcting the forced commutation duty ratio, the forced commutation duty ratio is determined based on the result of linear interpolation performed on the relationship between the plurality of test drive duty ratios and the corresponding rotation speeds. This allows the forced commutation duty ratio to be corrected with high accuracy.

[0038] (Other embodiments) The processes in steps S2 and S3 may be performed as necessary. The correction according to the ratio of the power supply voltages in the third embodiment may be applied to the fourth and fifth embodiments. Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure. [Explanation of symbols]

[0039] In the drawing, 1 indicates an electronic control device, 2 indicates a pump motor, 3 indicates a microcomputer, and 4 indicates a control IC.

Claims

1. A pump motor (2) for controlling the pressure of the urea pipe; A rotation speed detection unit (10, 16, 17) for detecting the rotation speed of the pump motor; A control unit (3, 3A to 3D) that controls the drive of the pump motor by PWM (Pulse Width Modulation), the control unit has a test period for confirming a rotation operation of the pump motor before performing a forced commutation process of the pump motor so as to make the rotation speed reach a target rotation speed, an electronic control device that, during the test period, compares a rotation speed of the pump motor detected when the pump motor is driven by a PWM signal of a test drive duty ratio with a reference rotation speed corresponding to the PWM signal of the test drive duty ratio, and corrects a forced commutation duty ratio of the PWM signal that is set during the forced commutation processing in accordance with a result of the comparison.

2. 2. The electronic control device according to claim 1, wherein the control unit (3A) corrects the forced commutation duty ratio in accordance with a ratio between the rotation speed of the pump motor detected during the test period and the reference rotation speed.

3. 2. The electronic control device according to claim 1, wherein the control unit (3C) corrects the forced commutation duty ratio by adding a predetermined correction constant to a result obtained by subtracting a predetermined correction constant from a reference duty ratio, multiplying the result by the ratio.

4. 4. The electronic control device according to claim 1, wherein the control unit (3B) corrects the forced commutation duty ratio also in response to a result of comparing a power supply voltage during the test period with a power supply voltage during the forced commutation process.

5. 2. The electronic control device according to claim 1, wherein the control unit (3D) changes the test drive duty ratio to a plurality of values ​​during the test period, detects the pump motor rotation speeds corresponding to the respective test drive duty ratios, and determines whether or not to correct the forced commutation duty ratio in accordance with the values ​​of the rotation speeds.

6. 6. The electronic control device according to claim 5, wherein when correcting the forced commutation duty ratio, the control unit determines the forced commutation duty ratio based on a result of linear interpolation performed on a relationship between a plurality of test driving duty ratios and the corresponding rotation speeds.

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