Control apparatus for driving solenoid proportional control valve

Abstract

To reduce the number of switching cycles to reduce losses.SOLUTION: A signal conversion circuit performs a first conversion in which, for a PWM signal consisting of a pulse signal of a duty ratio set for each cycle based on a target signal, the duty ratio of the first specified cycle in which the duty ratio is greater than 0% and less than or equal to the first predetermined duty ratio is set to 0% and the duty ratio of pulse signals in the next and subsequent cycles increase by the amount of the first differential duty ratio corresponding to the duty ratio of the truncated pulse signal in the first specified cycle, and a second conversion in which a duty ratio of the second specified cycle in which the duty ratio is greater than or equal to the second specified duty ratio and less than 100% is set to 100% and the duty ratio of the pulse signals in the next and subsequent cycles is reduced by the amount of the second differential duty ratio corresponding to the duty ratio of the pulse signal rounded up in the second specified cycle.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The technology disclosed herein belongs to the technical field of a control device for driving an electromagnetic proportional control valve. [Background technology]

[0002] Proportional electromagnetic control valves are known that control the pressure of a working fluid by changing the valve opening in proportion to the current supplied to a coil. The operation of a proportional electromagnetic control valve is performed by inputting a PWM signal set to a predetermined duty ratio to a drive element.

[0003] For example, Patent Document 1 discloses a switching device that determines a load factor calculation unit that calculates a load factor indicating the load state of a load to which output power from a DC / DC converter is supplied, and a thinning pattern of a pulse signal that is determined in association with the load factor so that fewer pulses are output from pulses of a predetermined period as the load factor decreases, and a pulse width correction coefficient that is determined so that the pulse width of the pulse signal becomes larger as the load factor decreases; the switching device thins out pulses of the pulse signal based on the thinning pattern and corrects the pulse width of the pulse signal with the correction coefficient.

[0004] Furthermore, Patent Document 2 discloses a method of driving a solenoid valve in which a PWM duty for obtaining a target solenoid valve drive current is calculated for each dither current period, and the PWM duty to be provided to a PWM circuit is set by adding or subtracting an offset duty to the PWM duty for each PWM period so that a predetermined dither current waveform is obtained over multiple PWM cycles. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2010-161862 A [Patent Document 2] Patent No. 3922397 Summary of the Invention [Problem to be solved by the invention]

[0006] When controlling an electromagnetic proportional control valve by PWM control, the drive element is frequently and repeatedly turned on and off. When the drive element is switched on and off, loss occurs, so it is preferable to keep the number of switching times as small as possible.

[0007] In the method described in Patent Document 1, when the duty ratio is low, the pulses are thinned out and the pulse width is widened, so that a desired current waveform can be formed with a small number of switching times. However, when the duty ratio is high, the pulses can hardly be thinned out and the correction coefficient is also small, so it is difficult to form a desired current waveform by reducing the number of switching times. Since more current flows when the duty ratio is high than when the duty ratio is low, the effect of reducing the number of switching times is large. Therefore, the method described in Patent Document 1 is not completely ineffective in reducing losses, but the effect is small.

[0008] As described in Patent Document 2, when realizing a dither current waveform, a signal with a high duty ratio and a signal with a low duty ratio are repeated. For this reason, when using a dither current in particular, the method described in Patent Document 1 is insufficient in terms of the effect of reducing losses over a long period.

[0009] The technology disclosed herein has been made in view of the above points, and its purpose is to reduce the number of switching operations and to reduce losses. [Means for solving the problem]

[0010] In order to solve the above problems, in a first aspect of the technology disclosed herein, a control device for an electromagnetic proportional control valve that drives an electromagnetic proportional control valve that controls the pressure of a working fluid with a valve opening proportional to a current includes a drive element that flows a current to the electromagnetic proportional valve when the drive element is turned on, a driver that outputs a target signal indicating a target current to be supplied from the drive element to the electromagnetic proportional control valve, and a PWM generation unit that outputs a PWM signal having a continuous pulse signal for driving the drive element based on the target signal from the driver, the PWM generation unit having a signal generation circuit that generates the pulse signal with a set duty ratio every cycle, and a signal conversion circuit that converts the generated PWM signal, and the signal conversion circuit has a digital The pulse width modulation circuit is configured to execute a first conversion in which the duty ratio of a first specific period in which the duty ratio is greater than 0% and less than a first predetermined duty ratio is set to 0%, and the duty ratio of the pulse signal in the next and subsequent periods is increased by a first differential duty ratio equivalent to the duty ratio of the pulse signal rounded down in the first specific period; and a second conversion in which the duty ratio of a second specific period in which the duty ratio is greater than or equal to a second predetermined duty ratio higher than the first predetermined duty ratio and less than 100% is set to 100%, and the duty ratio of the pulse signal in the next and subsequent periods is decreased by a second differential duty ratio equivalent to the duty ratio of the pulse signal rounded up in the second specific period.

[0011] Since the control of the electromagnetic proportional control valve is basically performed in a long cycle, even if the pulse signal of each cycle is converted, as long as the period of the high level signal and the period of the low level signal are appropriately set in the long cycle, there is no particular problem in the control of the electromagnetic proportional control valve.

[0012] With this configuration, in the first conversion, pulse signals with a very small duty ratio are set to a duty ratio of 0%. The pulse signal portion rounded down in the first conversion is absorbed into the pulse signal in the next period and thereafter. In the second conversion, pulse signals with a very large duty ratio are set to a duty ratio of 100%. The pulse signal portion rounded up in the second conversion is removed from the pulse signal in the next period and thereafter. This reduces the number of switching operations, thereby reducing losses.

[0013] Furthermore, by reducing the number of switching operations, high frequency noise caused by switching is suppressed.

[0014] Also, it takes some time for the driving element to switch. Therefore, when the duty ratio of the pulse signal is quite small, the period of the high level signal may be too short, and the driving element may be turned off before it is completely turned on. Also, when the duty ratio of the pulse signal is quite large, the period of the low signal may be too short, and the driving element may be turned on before it is completely turned off. In these cases, the driving element is not working, and only losses due to switching occur. In the above configuration, the high level signal can be set to an appropriate length, and the low level signal can be set to an appropriate length, so that it is possible to suppress only losses from occurring.

[0015] In a second aspect of the technology disclosed herein, in the first aspect, when the duty ratio of the pulse signal in the next cycle after the first specific cycle is increased by the first differential duty ratio, resulting in the duty ratio being equal to or greater than the second predetermined duty ratio and less than 100%, the signal conversion circuit performs the second conversion on the pulse signal in that cycle, and when the duty ratio of the pulse signal in the next cycle after the second specific cycle is decreased by the second differential duty ratio, resulting in the duty ratio being greater than 0% and equal to or less than the first predetermined duty ratio, the signal conversion circuit performs the first conversion on the pulse signal in that cycle.

[0016] According to this configuration, the pulse signal in each period is composed of a high level signal of an appropriate length and a low level signal of an appropriate length, which makes it possible to more effectively suppress losses.

[0017] In a third aspect of the technology disclosed herein, in the first aspect, the first predetermined duty ratio is set to a larger value when the slew rate of the driving element is low compared to when the slew rate is high, and the second predetermined duty ratio is set to a smaller value when the slew rate of the driving element is low compared to when the slew rate is high.

[0018] With this configuration, when the slew rate of the drive element is low, it is possible to prevent the drive element from being turned off before it is completely on, or the drive element from being turned on before it is completely off, thereby making it possible to more effectively suppress losses.

[0019] In a fourth aspect of the technology disclosed herein, in any one of the first to third aspects, the driver outputs a target signal as a target current, which is a current waveform in which a dither current having an amplitude corresponding to a command current is superimposed on a command current based on a required output of the electromagnetic proportional control valve.

[0020] According to this configuration, since the dither current is included in the target current, the duty ratio of the pulse signal changes every cycle. Therefore, the PWM signal is a signal in which a pulse signal with a low duty ratio and a pulse signal with a high duty ratio are mixed. Therefore, the first conversion and the second conversion can be effectively used for a part of the pulse signals of the PWM signal for generating the dither current. As a result, the number of switching operations can be reduced, and the effect of reducing losses can be more appropriately achieved.

[0021] In a fifth aspect of the technology disclosed herein, in the fourth aspect, when the first conversion results in a duty ratio of 0% and the actual current falls below the lower limit of the target current, the signal conversion circuit prohibits the first conversion even if the duty ratio is equal to or less than the first specified duty ratio, and when the second conversion results in a duty ratio of 100% and the actual current exceeds the upper limit of the target current, the signal conversion circuit prohibits the second conversion even if the duty ratio is equal to or more than the second specified duty ratio.

[0022] According to this configuration, the target current can be achieved while suppressing the number of switching operations.

[0023] In a sixth aspect of the technology disclosed herein, in the fourth aspect, the signal conversion circuit stops the first conversion for the pulse signal having a period corresponding to the end of each period of the dither current even if the duty ratio is equal to or less than the first predetermined duty ratio, and stops the second conversion even if the duty ratio is equal to or more than the second predetermined duty ratio.

[0024] According to this configuration, the first conversion and the second conversion are performed only in each period of the dither current. Therefore, the first differential duty ratio and the second differential duty ratio are not carried over to the dither current of the next period. This makes it possible to realize the target current while suppressing the number of switching operations.

[0025] A seventh aspect of the technique disclosed herein is directed to a method for controlling an electromagnetic proportional control valve by a controller that drives an electromagnetic proportional control valve that controls the pressure of a working fluid with a valve opening proportional to a current, and includes a first step of outputting a target signal indicating a target current to be supplied from a drive element to the electromagnetic proportional control valve, a second step of outputting a PWM signal consisting of a pulse signal having a duty ratio set for each cycle based on the target signal and for driving the drive element, and a third step of converting the output PWM signal, and the third step converts the PWM signal into a PWM signal having a duty ratio greater than 0% and a first predetermined duty ratio greater than 0%. setting the duty ratio of a first specific period which is equal to or less than the first specific duty ratio to 0%, and increasing the duty ratio of the pulse signal in the next and subsequent periods by a first differential duty ratio equivalent to the duty ratio of the pulse signal rounded down in the first specific period; setting the duty ratio of a second specific period which is equal to or more than a second predetermined duty ratio which is higher than the first predetermined duty ratio and less than 100% to 100%, and decreasing the duty ratio of the pulse signal in the next and subsequent periods by a second differential duty ratio equivalent to the duty ratio of the pulse signal rounded up in the second specific period.

[0026] This configuration also reduces the number of switching operations and allows the high-level signal and the low-level signal to have appropriate lengths, so that loss can be effectively reduced. Effect of the Invention

[0027] As described above, according to the technology disclosed herein, it is possible to reduce the number of switching operations and to reduce losses over a long period of time. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a block diagram illustrating a schematic configuration of a control device for driving an electromagnetic proportional control valve according to an exemplary embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a current waveform of a target current and a PWM signal for realizing the current waveform. [Diagram 3]FIG. 3 is a diagram illustrating switching waveforms of the drive element when the duty ratio of the pulse signal is smaller than a first predetermined duty ratio and when the duty ratio of the pulse signal is larger than a second predetermined duty ratio. [Figure 4] FIG. 4 is a schematic diagram showing a method of converting a pulse signal in the signal conversion circuit. [Diagram 5] FIG. 5 is a schematic diagram illustrating an example of conversion of a pulse signal. [Figure 6] FIG. 6 is a schematic diagram illustrating another example of conversion of a pulse signal. [Figure 7] FIG. 7 is a schematic diagram illustrating yet another example of conversion of a pulse signal. [Figure 8] FIG. 8 is a diagram showing a current waveform when the first conversion and the second conversion are performed on a pulse signal that satisfies the prohibition condition. [Figure 9] FIG. 9 is a diagram showing a current waveform when the first conversion and the second conversion are not performed on a pulse signal that satisfies the prohibition condition. [Figure 10] FIG. 10 is a flowchart showing the processing operation of the PWM generating unit. [Figure 11] FIG. 11 is a flowchart showing the processing operation of the signal conversion circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Exemplary embodiments will now be described in detail with reference to the drawings.

[0030] Overall Structure FIG. 1 shows a schematic configuration of a control device 1 for a solenoid valve 100, which is an electromagnetic proportional control valve. The solenoid valve 100 is, for example, a control valve for adjusting hydraulic pressure in an automatic transmission of an automobile. The solenoid valve 100 has a coil. Since the configuration of the solenoid valve 100 itself is publicly known, detailed description will be omitted. However, when a current is supplied to the coil, the solenoid valve 100 adjusts the opening by moving a spool valve by a magnetic force generated from the coil, thereby adjusting the hydraulic pressure. At this time, the current supplied to the coil and the generated magnetic force are approximately proportional to each other, so the hydraulic pressure adjusted by the solenoid valve 100 changes in proportion to the current supplied to the coil.

[0031] The control device 1 includes a driving element 10 connected in series to a coil of a solenoid valve 100. The driving element 10 is, for example, a MOSFET, and supplies a current to the coil when it is on.

[0032] The control device 1 has a controller 2 that operates the driving element 10. The controller 2 includes a driver 20 that outputs a target signal indicating a target current to be supplied from the driving element 10 to the coil, and a PWM generating circuit 40 that outputs a PWM signal consisting of a pulse signal with a duty ratio set for each period from the driver 20 based on the target signal. The control device 1 also includes a sense resistor 50 and a current detection circuit 51 that detect an actual current value supplied to the solenoid valve 100, an AD conversion circuit 52 that converts the detection result of the current detection circuit 51 into an AD conversion, and a PI control circuit 30 for feedback control based on the detection result of the current detection circuit 51. The controller 2, the current detection circuit 51, and the AD conversion circuit 52 may each be configured as an independent chip, or may be integrated into one chip.

[0033] The driver 20 has a CPU and a memory. The driver 20 sets a waveform in which a dither current is superimposed on an instruction current of a constant current value as a target current waveform. It is known that the solenoid valve 100 generates hysteresis between the current and the hydraulic pressure due to frictional resistance between the case of the solenoid valve 100 and the spool valve. It is also known that applying a slight vibration to the spool valve is effective in eliminating this hysteresis. For this reason, the driver 20 includes not only an instruction current but also a dither current for applying a slight vibration to the spool valve in the target current.

[0034] The right diagram in FIG. 2 shows an example of the target current. The target current has a triangular wave shape consisting of a command current and a dither current according to the required output of the solenoid valve 100. The dither current is specified by a dither period set to a length several times the period of the PWM signal, and a dither amplitude set according to the command current and the dither period. The command current corresponds to the average value of one period of the target waveform. The dither amplitude corresponds to the width from the command current to a peak or valley. The driver 20 sets the target current by setting the average current value corresponding to the command current, the dither amplitude, and the dither period.

[0035] The PWM generating circuit 40 generates and outputs a PWM signal so as to realize a target current by on / off control of the driving element 10. The PWM generating circuit 40 has a signal generating circuit 41 that actually generates the PWM signal, and a signal converting circuit 42 that converts the signal generated by the signal generating circuit 41.

[0036] The signal generating circuit 41 sets a duty ratio for each period based on the target current. The signal generating circuit 41 generates a pulse signal for each period based on the set duty ratio. The signal generating circuit 41 generates a pulse signal that changes from high level to low level for each period. Note that the "pulse signal" here refers to a signal for each period of the PWM signal.

[0037] The left diagram in Fig. 2 shows a PWM signal generated by the signal generating unit 41 based on the target current. When the PWM signal is at a high level, the driving element 10 is turned on, and when the PWM signal is at a low level, the driving element 10 is turned off. The PWM signal has a high duty ratio in the rising step, which is the part of the target current that rises to the right, so the high-level period is longer than the low-level period. On the other hand, the PWM signal has a low duty ratio in the falling step, which is the part of the target current that falls to the right, so the low-level period is longer than the high-level period.

[0038] When the driving element 10 is turned on while the PWM signal is at a high level, a current flows through the coil of the solenoid valve 100. At this time, the current flowing through the coil increases according to the RL load driving waveform. Also, when the PWM signal becomes a low level and the driving element 10 changes from on to off, a flyback current is generated due to the back electromotive force generated in the coil. As described above, when the flyback current is consumed, the current decays. By repeatedly turning on and off the driving element 10 by the PWM signal, the current flowing through the coil repeatedly increases and decays. As a result, the waveform of the current flowing through the coil takes a shape that conforms to the target current, as shown in the center diagram of FIG. 2.

[0039] <Switching loss> Here, losses occur when the driving element 10 is switched (when it is switched on and off). Specifically, as shown in Fig. 3, when the PWM signal goes to high level, the driving element 10 turns on. Since it takes some time for the driving element 10 to switch on, the driving element 10 turns on with a slight delay after the PWM signal goes to high level. The power consumed until the driving element 10 turns on becomes the switching loss.

[0040] In order to reduce switching loss, it is preferable to keep the number of switching operations as small as possible. Losses are particularly likely to occur when the duty ratio is large, such as at the end of a rising step of the dither current, or when the duty ratio is small, such as at the end of a falling step (i.e., the end of the dither cycle).

[0041] For example, as shown in Fig. 3, when the duty ratio is small and the high level time is short, the driving element 10 is turned off before it is fully turned on. On the other hand, when the duty ratio is large and the low level time is short, the driving element 10 is turned on again before it is fully turned off. In these cases, the driving element 10 only generates losses.

[0042] Signal conversion processing Therefore, in this embodiment, the signal conversion circuit 42 converts the PWM signal generated by the signal generation circuit 41, thereby reducing the number of switching operations.

[0043] 4 shows the processing by the signal conversion circuit 42. The PWM signal before conversion is a pulse signal with a duty ratio set for each period. Therefore, unless the duty ratio is 0% or 100%, there are two switching events per period: one from low level to high level and one from high level to low level.

[0044] The signal conversion circuit 42 performs two conversions, a first conversion and a second conversion, on the PWM signal.

[0045] In the first conversion, the duty ratio of a first specific period in which the duty ratio is greater than 0% and equal to or less than a first predetermined duty ratio (D1%) is set to 0%, and the duty ratio of the pulse signal in the next and subsequent periods is increased by a first differential duty ratio equivalent to the duty ratio of the pulse signal truncated in the first specific period. As shown in FIG. 3, the first differential duty ratio corresponds to the duty ratio of the first specific period. The first predetermined duty ratio is set based on the slew rate of the driving element 10. Specifically, the higher the slew rate of the driving element 10, the smaller the first predetermined duty ratio is set to. More specifically, when the power supply voltage is set to V in , the rising slew rate of the driving element 10 is SR r , each period of the PWM signal is t pwm As, D1={(V in / SR r ) / t pwm}×100 As a result of the first conversion, the number of switching operations in the first specific period becomes 0.

[0046] In the second conversion, the duty ratio of the second specific period, which is equal to or greater than a second predetermined duty ratio (D2%) higher than the first predetermined duty ratio but less than 100%, is set to 100%, and the duty ratio of the pulse signal in the next and subsequent periods is reduced by a second differential duty ratio equivalent to the duty ratio of the pulse signal rounded up in the second specific period. As shown in FIG. 3, the second differential duty ratio corresponds to a value obtained by subtracting the duty ratio of the second specific period from 100%. The second predetermined duty ratio is set based on the slew rate of the driving element 10. Specifically, the higher the slew rate of the driving element 10, the larger the second predetermined duty ratio is set to. More specifically, the falling slew rate of the driving element 10 is set to SR f , each period of the PWM signal is t pwm As, D2=[{t pwm -(V in / SR f )} / t pwm ] x 100 By the second conversion, the number of switching operations in the second specific period becomes one.

[0047] In this way, by performing the first and second conversions on the PWM signal, the number of switching operations is reduced, which reduces losses. On the other hand, the pulse signal that was truncated in the first conversion and the pulse signal that was rounded up in the second conversion are compensated for by the pulse signal in the next period and thereafter, so the overall current waveform does not deviate significantly from the target current.

[0048] When the signal conversion circuit 42 is unable to fully compensate for the pulse signal truncated in the first conversion and the pulse signal rounded up in the second conversion with the pulse signal of the next period, it compensates for the remaining portion of the pulse signal in the period after next.

[0049] Specifically, as shown in the upper diagram of Figure 5, in the PWM signal before conversion, the duty ratio in the first period is X1%, the duty ratio in the second period is Y1%, and the duty ratio in the third period is Z1%. X1% is equal to or greater than the second predetermined duty ratio. Y1% is a value smaller than the absolute value of the difference between 100% and X%.

[0050] From the state before conversion, the signal conversion circuit 42 first executes a second conversion to make the duty ratio of the first period 100% and reduce the duty ratio of the second period by the second differential duty ratio rounded up in the first period.

[0051] The second differential duty ratio is (100-X1)%. Since Y1% is smaller than (100-X1)%, the pulse signal rounded up in the second conversion cannot be fully compensated in the second period. In this case, as shown in the lower diagram of FIG. 5, the signal conversion circuit 42 reduces the duty ratio of the second period to 0% and compensates in the third period for the pulse signal that could not be fully compensated in the second period. The duty ratio corresponding to the pulse signal that could not be fully compensated in the second period is (100-X1-Y1)%. The signal conversion circuit 42 reduces the duty ratio of the third period by (100-X1-Y1)%. This shortens the time of the high-level signal in the third period. This compensates for all of the pulse signals that were rounded up in the second conversion for the first period.

[0052] When the pulse signal truncated in the first conversion is compensated for with the pulse signal of the next period, and the duty ratio of the compensated pulse signal of the next period is equal to or smaller than a first predetermined duty ratio, the signal conversion circuit 42 performs the first conversion on the pulse signal of the next period.

[0053] Specifically, as shown in the upper diagram of Figure 6, in the PWM signal before conversion, the duty ratio is X2% in the first period, Y2% in the second period, and Z2% in the third period. X2% is equal to or less than the first predetermined duty ratio.

[0054] From the state before conversion, the signal conversion circuit 42 executes the first conversion to set the duty ratio of the first period to 0% and to increase the duty ratio of the second period by the first differential duty ratio rounded down in the first period. As a result, the duty ratio of the second period becomes (Y2+X2)%, which is equal to or less than the first predetermined duty ratio.

[0055] The signal conversion circuit 42 executes the second conversion again to set the duty ratio of the second period to 0%, and increases the duty ratio of the third period by the first differential duty ratio that was cut off in the current second period. Here, the first differential duty ratio is (Y2+X2)%. Therefore, the duty ratio of the third period becomes (Z2+Y2+X2)%. (Z2+Y2+X2)% is greater than the first predetermined duty ratio. This compensates for all of the pulse signals that were cut off in the first conversion for the first and second periods.

[0056] In this way, by repeating the first conversion until the pulse signal is no longer subject to the first conversion, the length of the high-level signal included in the PWM signal can be made appropriate, thereby effectively reducing the pulse signal that only generates losses.

[0057] The signal conversion circuit 42 determines whether to execute the first conversion, execute the second conversion, or maintain the duty ratio every time the duty ratio is calculated. Therefore, a pulse signal that was not the target of the first conversion or the second conversion before the conversion may become the target of the first conversion or the second conversion as a result of the first conversion or the second conversion in the previous cycle. An example will be described with reference to FIG. 7.

[0058] As shown in the upper diagram of Figure 7, in the PWM signal before conversion, the duty ratio of the first period is X3%, the duty ratio of the second period is Y3%, and the duty ratio of the third period is Z3%. X3% is equal to or greater than the second predetermined duty ratio, so the first specific period is subject to the second conversion. On the other hand, Y3% and Z3% are greater than the first predetermined duty ratio and smaller than the second predetermined duty ratio, so the second and third periods are not subject to the first and second conversions.

[0059] From the state before conversion, the signal conversion circuit 42 determines whether the pulse signal of the first period is the target of conversion. Since the first period corresponds to the second specific period, the signal conversion circuit 42 executes the second conversion on the pulse signal of the first period. The signal conversion circuit 42 reduces the duty ratio of the second period by the second differential duty ratio rounded up in the first period. This shortens the time of the high-level signal in the second period. As shown in the middle diagram of FIG. 7, after the second conversion is executed, the duty ratio of the second period becomes equal to or less than the first predetermined duty ratio.

[0060] Next, the signal conversion circuit 42 determines whether the current pulse signal of the second period is a target for conversion. The second period corresponds to the first specific period as a result of the second conversion on the first period. The signal conversion circuit 42 executes the first conversion on the current pulse signal of the second period. The signal conversion circuit 42 increases the duty ratio of the third period by the first differential duty ratio truncated in the second period. The first differential duty ratio is {Y3-(100-X3)}%.

[0061] Next, the signal conversion circuit 42 judges whether the current pulse signal of the third period is a target for conversion. Here, even after the first conversion is performed on the pulse signal of the second period, the pulse signal of the third period has a duty ratio greater than the first predetermined duty ratio and smaller than the second predetermined duty ratio, so it is not a target for the first conversion and the second conversion. Therefore, as shown in the lower diagram of FIG. 7, the signal conversion circuit 42 maintains the duty ratio of the third period. If the duty ratio of the third period becomes equal to or greater than the second predetermined duty ratio as a result of the first conversion on the second period, the signal conversion circuit 42 performs the second conversion on the pulse signal of the third period. Also, even after the first conversion is performed on the second period, if the duty ratio of the third period is equal to or less than the first predetermined duty ratio, the signal conversion circuit 42 performs the first conversion on the pulse signal of the third period.

[0062] In this way, the signal conversion circuit 42 reduces the number of switching operations by performing the first conversion and the second conversion as much as possible. On the other hand, when any of the following first, second, and third prohibition conditions is satisfied, the signal conversion circuit 42 prohibits the first conversion even if the duty ratio is equal to or less than the first predetermined duty ratio, and prohibits the second conversion even if the duty ratio is equal to or more than the second predetermined duty ratio.

[0063] The first prohibition condition is that the first conversion results in a duty ratio of 0% resulting in the actual current falling below the lower limit of the target current. The second prohibition condition is that the second conversion results in a duty ratio of 100% resulting in the actual current rising above the upper limit of the target current. The third prohibition condition is that the pulse signal is a pulse signal with a period corresponding to the end of each period of the dither current. The lower limit of the target current is the command current minus the dither amplitude. The upper limit of the target current is the command current plus the dither amplitude.

[0064] Fig. 8 shows a case where the first conversion and the second conversion are performed even if any one of the first, second, and third prohibition conditions is satisfied. "First" in Fig. 8 indicates that the first conversion has been performed, and "second" indicates that the second conversion has been performed. The "final period" is the period of the PWM signal that corresponds to the end of the dither period.

[0065] As shown in Fig. 8, as a result of the second conversion, it can be seen that the actual current exceeds the upper limit value of the target current. Also, as a result of the first conversion for the final period, it can be seen that the actual current falls below the lower limit value of the target current. If the actual current exceeds the upper limit value of the target current or falls below the lower limit value of the target current, the controllability of the solenoid valve 100 deteriorates. For this reason, the signal conversion circuit 42 prohibits the first conversion and the second conversion when the first prohibition condition or the second prohibition condition is satisfied.

[0066] As shown in Fig. 8, as a result of performing the first conversion for the final period, the pulse signal of the dither current of the previous period is carried over to the dither current of the next period. If the pulse signal crosses over the dither period, deviations from the target current accumulate, and ultimately the waveform of the actual current may deviate significantly from the target current. For this reason, the signal conversion circuit 42 prohibits the first conversion and the second conversion when the third prohibition condition is satisfied.

[0067] FIG. 9 shows a case where the first conversion and the second conversion are prohibited when any one of the first, second, and third prohibition conditions is satisfied.

[0068] It can be seen that the first conversion and the second conversion are prohibited for some periods of the PWM signal, and as a result, the actual current falls within the range of the target current. The number of switching times is increased compared to the case of FIG. 8. However, compared to the case where the first conversion and the second conversion are not performed at all (see FIG. 2), the number of switching times is reduced. Therefore, it is possible to reduce losses while maintaining the controllability of the solenoid valve 100.

[0069] When the first and second prohibition conditions are met, the pulse signal of the cycle subject to the prohibition condition is not rounded down or rounded up. Compensation (increase or decrease in duty ratio) for rounding down or rounding up the pulse signal of the immediately preceding cycle is also performed on the pulse signal of the target cycle.

[0070] Next, the processing operation of the signal conversion circuit 42 will be described with reference to the flow charts of FIGS.

[0071] First, in step S1, a pulse signal for one cycle is input to the signal conversion circuit 42 from the signal generation circuit 41. The duty ratio of the pulse signal input here (hereinafter referred to as an initial duty ratio) is a duty ratio calculated by the signal generation circuit 41 based on a target signal from the driver 20.

[0072] Next, in step S2, the signal conversion circuit 42 calculates a tentative duty ratio. The tentative duty ratio is a value obtained by adding a differential duty ratio calculated in the previous or previous cycle to the initial duty ratio of the cycle. The differential duty ratio also includes a duty ratio corresponding to a pulse signal that was rounded down or rounded up in the cycle before last and was not fully compensated for in the previous cycle. The sign of the differential duty ratio is positive when a first conversion is performed in the signal conversion process described below, whereas it is negative when a second conversion is performed in the signal conversion process described below. When the pulse signal is a pulse signal with a cycle corresponding to the beginning of the dither cycle, the differential duty ratio is set to 0.

[0073] Next, in step S3, the signal conversion circuit 42 performs a signal conversion process on the pulse signal of that cycle. The signal conversion process will be described in detail later.

[0074] Next, in step S4, the signal conversion circuit 42 sets the tentative duty ratio after the signal conversion process is completed as the final duty ratio of the period.

[0075] Next, in step S5, the signal conversion circuit 42 calculates a differential duty ratio. The differential duty ratio corresponds to the first differential duty ratio rounded down in the signal conversion process of step S3, or the second differential duty ratio rounded up in the signal conversion process of step S3. When the differential duty ratio is the first differential duty ratio, the sign is made positive, whereas when the differential duty ratio is the second differential duty ratio, the sign is made negative. When the tentative duty ratio is maintained in the signal conversion process of step S3, the differential duty ratio is made 0%.

[0076] Then, in step S6, the signal conversion circuit 42 outputs a pulse signal with the final duty ratio.

[0077] After step S6, the signal conversion circuit 42 returns and performs the same processes of steps S1 to S6 on the pulse signal of the next period.

[0078] Next, the signal conversion process will be described in detail.

[0079] First, in step S31, the signal conversion circuit 42 judges whether the period is the final period, i.e., the period corresponding to the end of the dither period. If the period is not the final period (YES), the signal conversion circuit 42 proceeds to step S32. On the other hand, if the period is the final period (NO), the signal conversion circuit 42 proceeds to step S38.

[0080] In step S32, the signal conversion circuit 42 judges whether the tentative duty ratio is greater than 0% and equal to or less than the first predetermined duty ratio D1%. If the tentative duty ratio is greater than 0% and equal to or less than the first predetermined duty ratio D1%, that is, YES, the signal conversion circuit 42 proceeds to step S33. On the other hand, if the tentative duty ratio is 0% or greater than the first predetermined duty ratio, that is, NO, the signal conversion circuit 42 proceeds to step S35.

[0081] In step S33, the signal conversion circuit 42 judges whether the actual current is equal to or greater than the lower limit of the target current when the first conversion is performed on the pulse signal of the cycle. The signal conversion circuit 42 judges whether the actual current is equal to or greater than the lower limit of the target current based on the actual current value up to the previous cycle detected by the sense resistor 50 and the current detection circuit 51. If the actual current is equal to or greater than the lower limit of the target current (YES), the signal conversion circuit 42 proceeds to step S34. On the other hand, if the actual current is lower than the lower limit of the target current (NO), the signal conversion circuit 42 proceeds to step S38.

[0082] In step S34, the signal conversion circuit 42 performs the first conversion on the pulse signal of the cycle, and sets the tentative duty ratio to 0%. After step S34, the process returns.

[0083] In step S35, the signal conversion circuit 42 judges whether the tentative duty ratio is equal to or greater than the second predetermined duty ratio and less than 100%. If the tentative duty ratio is equal to or greater than the second predetermined duty ratio and less than 100%, that is, YES, the signal conversion circuit 42 proceeds to step S36. On the other hand, if the tentative duty ratio is less than the second predetermined duty ratio or is 100%, that is, NO, the signal conversion circuit 42 proceeds to step S38.

[0084] In step S36, the signal conversion circuit 42 judges whether the actual current is equal to or less than the upper limit of the target current when the second conversion is performed on the pulse signal of the cycle. The signal conversion circuit 42 judges whether the actual current is equal to or less than the upper limit of the target current based on the actual current value detected by the sense resistor 50 and the current detection circuit 51. If the actual current is equal to or less than the upper limit of the target current (YES), the signal conversion circuit 42 proceeds to step S37. On the other hand, if the actual current exceeds the upper limit of the target current (NO), the signal conversion circuit 42 proceeds to step S38.

[0085] In step S37, the signal conversion circuit 42 performs the second conversion on the pulse signal of the period, and sets the tentative duty ratio to 100%. After step S37, the process returns.

[0086] In step S38, the signal conversion circuit 42 maintains the tentative duty ratio. After step S38, the process returns.

[0087] As described above, the control device 1 can reduce the number of switching operations by performing the first conversion and the second conversion. In addition, the control device 1 can reduce the number of pulse signals that only cause losses. Therefore, the control device 1 can reduce losses caused by the switching of the driving element 10.

[0088] Effects of the embodiment Therefore, in this embodiment, the control device 1 includes a drive element 10 that causes a current to flow through the solenoid proportional valve when the drive element 10 is on, a driver 20 that outputs a target signal indicating a target current to be supplied from the drive element 10 to the solenoid valve 100, and a PWM generation circuit 40 that outputs a PWM signal, which is a series of pulse signals for driving the drive element 10, from the driver 20 based on the target signal. The PWM generation circuit 40 has a signal generation circuit 41 that generates a pulse signal of a set duty ratio every cycle, and a signal conversion circuit 42 that converts the generated PWM signal. The signal conversion circuit 42 converts the generated PWM signal into a pulse signal having a duty ratio greater than 0% and a duty ratio greater than 100%. The control device 1 executes a first conversion in which the duty ratio of a first specific period that is equal to or less than a predetermined duty ratio is set to 0%, and the duty ratio of the pulse signal in the next and subsequent periods is increased by a first differential duty ratio corresponding to the duty ratio of the pulse signal rounded down in the first specific period, and a second conversion in which the duty ratio of a second specific period that is equal to or greater than a second predetermined duty ratio that is higher than the first predetermined duty ratio and less than 100% is set to 100%, and the duty ratio of the pulse signal in the next and subsequent periods is decreased by a second differential duty ratio corresponding to the duty ratio of the pulse signal rounded up in the second specific period. This allows the control device 1 to reduce the number of switching operations. The control device 1 can also reduce pulse signals that only cause losses. On the other hand, the control device 1 can control the solenoid valve 100 at a level that does not cause any particular problems, since the period of the high level signal and the period of the low level signal are appropriately set when viewed in a long period. Therefore, the control device 1 can reduce the number of switching operations of the drive element 10 and reduce losses while adjusting the waveform of the actual current to conform to the target current.

[0089] Furthermore, by reducing the number of switching operations, high frequency noise caused by switching is suppressed.

[0090] In addition, in this embodiment, when the duty ratio of the pulse signal in the next period after the first specific period is increased by the amount of the first differential duty ratio, and the duty ratio is equal to or greater than the second predetermined duty ratio and less than 100%, the signal conversion circuit 42 performs the second conversion on the pulse signal in the period, and when the duty ratio of the pulse signal in the next period after the second specific period is decreased by the amount of the second differential duty ratio, and the duty ratio is greater than 0% and equal to or less than the first predetermined duty ratio, the signal conversion circuit 42 performs the first conversion on the pulse signal in the period. As a result, the pulse signal in each period of the PWM signal is composed of a high-level signal of an appropriate length and a low-level signal of an appropriate length. As a result, the control device 1 can more effectively suppress losses.

[0091] Furthermore, in this embodiment, when the slew rate of the driving element 10 is low, the first predetermined duty ratio is set to a larger value than when the slew rate is high, and when the slew rate of the driving element 10 is low, the second predetermined duty ratio is set to a smaller value than when the slew rate is high. This makes it possible to prevent the driving element 10 from being turned off before being fully on or turned on before being fully off when the slew rate of the driving element 10 is low. As a result, the control device 1 can more effectively suppress losses.

[0092] In this embodiment, the signal conversion circuit 42 prohibits the first conversion even if the duty ratio is equal to or less than the first predetermined duty ratio when the actual current falls below the lower limit of the target current as a result of making the duty ratio 0% by the first conversion, and prohibits the second conversion even if the duty ratio is equal to or greater than the second predetermined duty ratio when the actual current exceeds the upper limit of the target current as a result of making the duty ratio 100% by the second conversion. This makes it possible to prevent the actual current from overshooting the target current. As a result, the control device 1 can accurately achieve the target current while suppressing the number of switching operations.

[0093] In this embodiment, the signal conversion circuit 42 prohibits the first conversion for the pulse signal having a period corresponding to the end of each period of the dither current even if the duty ratio is equal to or less than the first predetermined duty ratio, and prohibits the second conversion even if the duty ratio is equal to or more than the second predetermined duty ratio. As a result, the first conversion and the second conversion are performed only within each dither period, and the first differential duty ratio and the second differential duty ratio are not carried over to the next dither period. As a result, the control device 1 can accurately realize the target current while suppressing the number of switching operations.

[0094] (Other embodiments) The technology disclosed herein is not limited to the above-described embodiment, and may be substituted without departing from the spirit and scope of the claims.

[0095] For example, in the first and second embodiments, the driver 20 outputs a waveform in which a dither current is superimposed on an instruction current as a target current. However, the driver 20 may output a waveform that does not include a dither current as a target current.

[0096] The above-described embodiments are merely illustrative and should not be construed as limiting the scope of the present disclosure. The scope of the present disclosure is defined by the claims, and all modifications and variations within the scope of the claims are within the scope of the present disclosure. [Industrial Applicability]

[0097] The technology disclosed herein is useful as a control device for an electromagnetic proportional control valve that drives an electromagnetic proportional control valve that controls the pressure of a working fluid with a valve opening proportional to an electric current. [Explanation of symbols]

[0098] 2. Controller 10 Driving element 20 Drivers 40 PWM generation section 41 Signal generation circuit 42 Signal conversion circuit 100 Solenoid valve (electromagnetic proportional control valve)

Claims

1. A control device for an electromagnetic proportional control valve that drives an electromagnetic proportional control valve that controls the pressure of a working fluid with a valve opening proportional to an electric current, A drive element that, when turned on, passes a current through the solenoid proportional valve; a driver that outputs a target signal indicating a target current to be supplied from the drive element to the electromagnetic proportional control valve; a PWM generating unit that outputs a PWM signal that is a continuous pulse signal for driving the driving element based on a target signal from the driver, The PWM generating unit is a signal generating circuit for generating the pulse signal having a set duty ratio every cycle; a signal conversion circuit that converts the generated PWM signal; having The signal conversion circuit includes: a first conversion for changing the duty ratio of a first specific period in which the duty ratio is greater than 0% and equal to or less than a first predetermined duty ratio to 0%, and for increasing the duty ratio of the pulse signal in a next period and thereafter by a first differential duty ratio corresponding to the duty ratio of the pulse signal truncated in the first specific period; a second conversion for setting the duty ratio of a second specific period, which is equal to or greater than a second predetermined duty ratio higher than the first predetermined duty ratio and less than 100%, to 100%, and reducing the duty ratio of the pulse signal in a next period and thereafter by a second differential duty ratio corresponding to the duty ratio of the pulse signal rounded up in the second specific period; A control device for an electromagnetic proportional control valve, comprising:

2. 2. The control device for an electromagnetic proportional control valve according to claim 1, The signal conversion circuit includes: when the duty ratio of the pulse signal in the next or subsequent cycle of the first specific cycle is increased by the first differential duty ratio, so that the duty ratio becomes equal to or greater than the second predetermined duty ratio and less than 100%, the second conversion is performed on the pulse signal in the cycle; a first conversion step for converting a duty ratio of a pulse signal from a period after the second specific period to a period after the first specific period, the first conversion step being performed on the pulse signal in the period after the first specific period when the duty ratio is reduced by the second differential duty ratio so that the duty ratio is greater than 0% and equal to or less than the first specified duty ratio.

3. 2. The control device for an electromagnetic proportional control valve according to claim 1, the first predetermined duty ratio is set to a larger value when the slew rate of the drive element is low compared to when the slew rate is high, 2. A control device for an electromagnetic proportional control valve, wherein the second predetermined duty ratio is set to a smaller value when a slew rate of the drive element is low compared to when the slew rate is high.

4. The control device for an electromagnetic proportional control valve according to any one of claims 1 to 3, The control device for an electromagnetic proportional control valve, wherein the driver outputs a target signal as a target current, which is a current obtained by superimposing a dither current having an amplitude corresponding to a command current on a command current based on a required output of the electromagnetic proportional control valve.

5. 5. The control device for an electromagnetic proportional control valve according to claim 4, The signal conversion circuit includes: When the duty ratio is reduced to 0% by the first conversion and the actual current falls below a lower limit value of the target current, the first conversion is prohibited even if the duty ratio is equal to or less than the first predetermined duty ratio; When the duty ratio is set to 100% by the second conversion and an actual current exceeds an upper limit value of the target current, the second conversion is prohibited even if the duty ratio is equal to or greater than the second predetermined duty ratio. A control device for an electromagnetic proportional control valve.

6. 5. The control device for an electromagnetic proportional control valve according to claim 4, a signal conversion circuit that prohibits the first conversion for a pulse signal having a period corresponding to an end of each period of the dither current even if the duty ratio of the pulse signal is equal to or less than the first predetermined duty ratio, and that prohibits the second conversion for a pulse signal having a period corresponding to an end of each period of the dither current even if the duty ratio of the pulse signal is equal to or less than the second predetermined duty ratio.

7. A method for controlling an electromagnetic proportional control valve by a controller that drives an electromagnetic proportional control valve that controls a pressure of a working fluid with a valve opening proportional to an electric current, comprising the steps of: a first step of outputting a target signal indicating a target current to be supplied from a drive element to the electromagnetic proportional control valve; a second step of outputting a PWM signal, which is a pulse signal having a duty ratio set for each period based on the target signal and drives the driving element; and a third step of converting the output PWM signal, The third step is a duty ratio of a first specific period in which the duty ratio is greater than 0% and equal to or less than a first predetermined duty ratio is set to 0%, and the duty ratio of the pulse signal in the next and subsequent periods is increased by a first differential duty ratio corresponding to the duty ratio of the pulse signal truncated in the first specific period; a duty ratio of a second specific period in which the duty ratio is equal to or greater than a second predetermined duty ratio higher than the first predetermined duty ratio and less than 100% is set to 100%, and the duty ratio of the pulse signal in the next and subsequent periods is reduced by a second differential duty ratio corresponding to the duty ratio of the pulse signal rounded up in the second specific period; 4. A method for controlling an electromagnetic proportional control valve, comprising the steps of:

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