Control apparatus for driving solenoid proportional control valve

Abstract

To reduce losses by reducing the number of switching cycles even at high duty ratios.SOLUTION: A control apparatus for driving solenoid proportional control valve includes a PWM generator that outputs a PWM signal to drive a driving element based on the target signal from a driver, and the PWM generator includes a signal generation circuit that generates the PWM signal, which is a pulse signal with a set duty ratio for each cycle and goes from high level to low level, and a signal conversion circuit that converts the pulse signal of the first cycle out of the first and second cycles adjacent on the time axis in the generated PWM signal from low level to high level while maintaining the duty ratio, and combines the high level of the pulse signal of the first cycle with the high level of the pulse signal of the second cycle after conversion.SELECTED DRAWING: Figure 3

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 an offset duty is added or subtracted from the PWM duty for each PWM period to set the PWM duty to be provided to a PWM circuit so that a predetermined dither current 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 can be obtained with a small number of switching operations. 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 obtain a desired current by reducing the number of switching operations. 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 operations 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, 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 consideration of these points, and its purpose is to reduce losses by suppressing the number of switching operations even in the case of a high duty ratio. [Means for solving the problem]

[0010] In order to solve the above problems, a first aspect of the technology disclosed herein is directed to 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, the control device comprising: a drive element that flows a current through the electromagnetic proportional valve when the drive element is on; a driver that outputs a target signal indicating a target current to be supplied from the drive element to the coil; and a PWM generation unit that outputs a PWM signal that drives the drive element based on the target signal from the driver, the PWM generation unit having a signal generation circuit that generates a PWM signal that is a pulse signal with a duty ratio set for each period and that changes from high level to low level; and a signal conversion circuit that converts the pulse signal of a first period of the generated PWM signal, of a first period and a second period that are adjacent on the time axis, from low level to high level while maintaining the duty ratio, and combines the high level of the pulse signal of the first period and the high level of the pulse signal of the second period after conversion.

[0011] According to this configuration, the high level of the first cycle and the high level of the second cycle, which are adjacent on the time axis, are combined to form a single pseudo-pulse signal in two cycles while maintaining the duty ratio in each cycle, and the number of switching times is halved. In addition, since the high level and low level of the pulse signal are simply swapped on the time axis, this can be applied to both low duty ratio pulse signals and high duty ratio pulse signals. As a result, the number of switching times is reduced even in the case of a high duty ratio, and losses can be reduced.

[0012] Furthermore, by reducing the number of switching operations, high frequency noise caused by switching is suppressed.

[0013] In a second aspect of the technology disclosed herein, in the first aspect, 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 based on a required output of the electromagnetic proportional control valve.

[0014] According to this configuration, since the target current contains a dither 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. In the above configuration, even if the signal is a mixture of a pulse signal with a low duty ratio and a pulse signal with a high duty ratio, one pulse signal can be formed in two cycles in a pseudo manner while maintaining the duty ratio of each cycle. Therefore, even if the target current contains a dither current, the number of switching operations can be reduced, thereby reducing losses.

[0015] In a third aspect of the technology disclosed herein, in the first or second aspect, the conversion circuit inputs an inversion signal to the PWM signal that inverts the high and low levels of the first cycle pulse signal on the time axis, and converts the pulse signal from a low level to a high level.

[0016] According to this configuration, a plurality of pulse signals can be easily converted, which makes it possible to easily achieve the effect of reducing the number of switching operations and thus reducing losses.

[0017] A fourth aspect of the technology 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 to the coil via a drive element, 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 driving the drive element, and a third step of converting the output PWM signal, wherein the second step is a step of outputting a PWM signal so as to change from a high level to a low level in each cycle, and the third step is a step of converting a pulse signal of a first cycle out of a first cycle and a second cycle that are adjacent on the time axis in the PWM signal, so as to change from a low level to a high level while maintaining the duty ratio, and combining the high level of the pulse signal of the first cycle and the high level of the pulse signal of the second cycle after conversion.

[0018] With this configuration, the cycle can be virtually doubled while maintaining the duty ratio for each cycle, and the number of switching operations can be halved. This reduces the number of switching operations even in the case of a high duty ratio, and therefore reduces losses. Effect of the Invention

[0019] As described above, according to the technology disclosed herein, the number of switching operations can be suppressed even in the case of a high duty ratio, so that losses over a long period can be reduced. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of a control device for driving an electromagnetic proportional control valve according to the first embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a waveform of a target current and a PWM signal for achieving the target current. [Diagram 3] FIG. 3 is a schematic diagram showing a method of converting a pulse signal in the conversion circuit. [Figure 4] FIG. 4 is a schematic diagram showing a case where a pulse signal for generating a dither current is converted by a conversion circuit. [Diagram 5] FIG. 5 is a schematic diagram showing a method of converting a pulse signal in a conversion circuit in a control device for driving an electromagnetic proportional control valve according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Exemplary embodiments will now be described in detail with reference to the drawings.

[0022] (Embodiment 1) 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.

[0023] 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.

[0024] 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 unit 40 that outputs a PWM signal consisting of a pulse signal with a duty ratio set for each cycle 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.

[0025] The driver 20 has a CPU and a memory. The driver 20 sets a current in which a dither current is superimposed on an instruction current as a target current. 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 the instruction current but also a dither current for applying a slight vibration to the spool valve in the target current.

[0026] The upper 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 current. The dither amplitude corresponds to the width from the command current to the peak or valley. The driver 20 sets the target current by setting the average current value equivalent to the command current, the dither amplitude, and the dither period.

[0027] The PWM generating unit 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 unit 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.

[0028] 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.

[0029] The lower diagram of Fig. 2 shows a PWM signal generated by the signal generating circuit 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.

[0030] 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 load drive waveform of the RL series circuit. Also, when the PWM signal goes to 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 increases and decays repeatedly, and the current flowing through the coil becomes the target current.

[0031] Here, losses occur when the driving element 10 is switched (when it is switched on and off). For this reason, it is preferable to minimize the number of switching times. In particular, when the duty ratio is high, such as in the rising step of the dither current, the current that flows is large and losses are likely to be large.

[0032] 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.

[0033] 3 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.

[0034] The signal conversion circuit 42 divides the PWM signal output from the signal generation circuit 41 into two periods, with the earlier period being the first period and the later period being the second period. Then, for the pulse signal of the first period, the order of high level and low level is swapped while maintaining the duty ratio. Meanwhile, the pulse signal of the second period is left as it is. As a result, the pulse signal of the first period goes from low level to high level, and the pulse signal of the second period goes from high level to low level. As a result, the high level of the first period and the high level of the second period are consecutive, and the high level of the pulse signal of the first period and the pulse signal of the second period are pseudo-combined.

[0035] In this way, by converting the PWM signal, one pulse signal is formed in two periods in a pseudo manner. As shown in FIG. 3, normally, a two-period pulse signal has a total of four switchings. On the other hand, by converting the PWM signal using a conversion circuit, a two-period pulse signal has a total of two switchings. In other words, the number of switchings is halved. On the other hand, since the duty ratio does not change for each period, the waveform shape of the current output from the driving element 10 by the converted PWM signal is the same as that before the conversion, with only a slight shift in the time axis. Therefore, a desired current can be obtained with fewer switchings than with a normal PWM signal. This reduces losses.

[0036] The signal conversion circuit 42 can convert the PWM signal as long as the duty ratio is not 0% or 100%. Therefore, even in the case of a high duty ratio where the current is large and loss is likely to be large, the number of switching operations can be reduced, thereby reducing loss.

[0037] The signal conversion circuit 42 constantly performs conversion of the PWM signal while the solenoid 100 is activated.

[0038] Fig. 4 shows a state in which a target current including a dither current is generated by the control device 1 according to the first embodiment. Specifically, it shows a state in which the PWM signal shown in Fig. 2 is converted by the signal conversion circuit 42. The solid line in the upper diagram of Fig. 4 is the target current, and the dashed line is the actual current. Note that Fig. 4 starts from the high level portion of the first period for ease of comparison.

[0039] As shown in the lower diagram of FIG. 4, it can be seen that the number of switching times is smaller in both the rising step and the falling step compared to the lower diagram of FIG. 2. In the converted PWM signal, the high level period and the low level period are artificially longer, so the fluctuation in each signal becomes larger. However, since the duty ratio itself in each period is maintained, the average becomes the target current. Therefore, even if the duty ratio differs in each period like a dither current, especially in the case of a PWM signal in which a pulse signal with a high duty ratio and a pulse signal with a low duty ratio are mixed, the control device 1 according to the first embodiment can realize the target current while reducing the number of switching times. Note that in FIG. 4, the PWM signal and the signal of the real current generated thereby are shown roughly (at a fairly low frequency) in order to make the changes easier to see, but in reality, the PWM signal and the real current are fine (high frequency), so even if the fluctuation in the current becomes somewhat large due to the conversion of the PWM signal by the signal conversion circuit 42, it does not cause any particular problem.

[0040] Therefore, in the first embodiment, the solenoid valve 100 is provided with a driving element 10 that flows a current when turned on, a driver 20 that outputs a target signal indicating a target current to be supplied from the driving element 10 to the solenoid valve 100, and a PWM generating unit 40 that outputs a PWM signal to drive the driving element 10 based on the target signal from the driver 20. The PWM generating unit 40 has a signal generating circuit 41 that generates a PWM signal that is a pulse signal with a duty ratio set for each period and changes from high level to low level, and a signal converting circuit 42 that converts the pulse signal of the first period of the first and second periods that are adjacent on the time axis in the generated PWM signal so that the pulse signal of the first period changes from low level to high level while maintaining the duty ratio, and combines the high level of the pulse signal of the first period and the high level of the pulse signal of the second period after the conversion. This makes it possible to form one pulse signal in two periods in a pseudo manner. This makes it possible to form one pulse signal in two periods in a pseudo manner while maintaining the duty ratio when viewed in each period, and the number of switching times is halved. In addition, since the high and low levels of the pulse signal are simply swapped on the time axis, it can be applied to both low and high duty ratio pulse signals. This reduces the number of switching operations even in the case of a high duty ratio, thereby reducing losses.

[0041] Furthermore, by reducing the number of switching operations, high frequency noise caused by switching is suppressed.

[0042] In particular, in the present embodiment 1, the driver 20 outputs a target signal as a target current, which is a current obtained by superimposing a dither current having an amplitude according to the command current on a command current based on the required output of the solenoid 100. If the target current includes a dither current, the duty ratio of the pulse signal changes every cycle. Therefore, the PWM signal becomes a signal in which a pulse signal with a low duty ratio and a pulse signal with a high duty ratio are mixed. In the present embodiment 1, even if the signal includes a pulse signal with a low duty ratio and a pulse signal with a high duty ratio, one pulse signal can be formed in two cycles in a pseudo manner while maintaining the duty ratio of each cycle. Therefore, even if the target current includes a dither current, the number of switching operations can be reduced to reduce losses.

[0043] (Embodiment 2) Hereinafter, the second embodiment will be described in detail with reference to the drawings. In the following description, the same reference numerals will be used to designate the same parts as those in the first embodiment, and detailed description thereof will be omitted.

[0044] In the second embodiment, the operation of the signal conversion circuit 42 is different from that of the first embodiment. Specifically, in the second embodiment, as shown in FIG. 5, the signal conversion circuit 42 inputs an inversion signal that inverts the high level and low level of the PWM signal output from the signal generation circuit 41 with respect to the time axis. When the inversion signal is 1, the pulse signal is inverted. On the other hand, when the inversion signal is 0, the pulse signal is maintained as it is. The inversion signal wave is synchronized with the PWM signal and inverts the PWM signal with respect to the time axis every other period. Since the period of the PWM signal is constant, it is relatively easy to generate an inversion signal synchronized with the PWM signal.

[0045] This inversion signal inverts the high and low levels of the PWM signal with respect to the time axis every other period. As a result, in a first period and a second period of the PWM signal that are adjacent on the time axis, the high level of the first period and the high level of the second period are consecutive. Having consecutive high levels in two adjacent periods reduces the number of switching times of the PWM signal. When the converted PWM signal is viewed in each period, the duty ratio of each period is maintained. Therefore, the current generated by the converted PWM signal follows the target current. Therefore, the number of switching times to generate the target current can be reduced, and losses can be reduced.

[0046] 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.

[0047] For example, in the first and second embodiments, the driver 20 outputs, as the target current, a current in which a dither current is superimposed on an instruction current. However, the present invention is not limited to this, and the driver 20 may output, as the target current, a current that does not include a dither current.

[0048] 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]

[0049] 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 the current supplied to a coil. [Explanation of symbols]

[0050] 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 for driving the driving element based on a target signal from the driver, The PWM generating unit is a signal generating circuit that generates a PWM signal that is a pulse signal having a set duty ratio every period and that changes from a high level to a low level; a signal conversion circuit that converts a pulse signal in a first period of the generated PWM signal between a first period and a second period adjacent to each other on a time axis from a low level to a high level while maintaining a duty ratio, and combines the high level of the pulse signal in the first period and the high level of the pulse signal in the second period after the conversion; having A control device for an electromagnetic proportional control valve.

2. 2. The control device for an electromagnetic proportional control valve according to claim 1, 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.

3. 3. The control device for an electromagnetic proportional control valve according to claim 1, The signal conversion circuit inputs an inversion signal that inverts the high and low levels of the first cycle pulse signal on the time axis to the PWM signal, thereby converting the pulse signal from a low level to a high level.

4. 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 to the electromagnetic proportional control valve via a drive element; 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 second step is a step of outputting a PWM signal so as to change from a high level to a low level in each period; a third step of converting a pulse signal in a first cycle out of a first cycle and a second cycle which are adjacent on a time axis in the PWM signal, from a low level to a high level while maintaining a duty ratio, and combining the high level of the pulse signal in the first cycle after the conversion with the high level of the pulse signal in the second cycle.

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