JP2773551B2 - Piezoelectric element charge control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge control circuit for a piezoelectric element, and more particularly to a charge control circuit for a piezoelectric element having an error integration circuit for integrating an error between an actual charge and a target charge of the piezoelectric element. It relates to a control circuit.

[0002]

2. Description of the Related Art A piezoelectric element used for a pressurizing actuator of a fuel injection valve of an internal combustion engine can obtain a required air-fuel ratio even when the amount of expansion and contraction with respect to a drive signal of the same level changes due to temperature change, aging and the like. Needs to be corrected for Therefore, in consideration of the fact that the amount of expansion and contraction of the piezoelectric element and the amount of charge have conventionally corresponded, the drive current of the piezoelectric element is integrated, and the amount of expansion and contraction of the piezoelectric element is indirectly detected based on the integrated value. There is known a piezoelectric element control circuit in which a drive voltage is feedback-controlled based on the detection result (JP-A-60-43146).

[0003] In general, the feedback system model as shown in FIG. 17, is supplied to the circuit 2 of the transfer function G (s) of the input voltage V _i through the subtracter 1, and the output voltage V _u of the circuit 2 Of the transfer function H (s) through the feedback circuit 3, and the voltage V _FB obtained by feedback is input to the subtracter 1.

Since the transfer function of the entire feedback system model is expressed by G (s) / {1 + G (s) .H (s)}, the circuit of FIG. 17 can be rewritten as FIG. At this time, if H (s) = K ₁ and G (s) = ∞, the transfer function of this system is approximated by 1 / K ₁ and becomes stable. However, in practice, G (s) = ∞ and an error occurs, so an integral term is provided as G (s) = 1 / s. As a result, a delay occurs, but an error can be eliminated.

[0005] In view of the above, specifically, FIG.
As shown in FIG. 9, feedback is performed using an integrating circuit including an operational amplifier 5, a resistor 6 connected to the inverting input terminal thereof, and a capacitor 7 connected between the output terminal and the inverting input terminal of the operational amplifier 5. The integrated value of the drive current of the piezoelectric element in the above-described conventional circuit is obtained by the above-described integration circuit.

[0006]

[0007] However, in the conventional control circuit described above, although using an integrating circuit shown in FIG. 19, the integration circuit for an integrator circuit with respect to time, the input voltage V _i is constant The required integral voltage can be obtained only in the case of the period. However, when controlling the charge amount of the piezoelectric element used for the pressurizing actuator of the fuel injection valve of the internal combustion engine, the input voltage V _i
Is input asynchronously according to the ignition timing and the like, so that a required integrated voltage cannot be obtained, and accurate charge charge amount control cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide a piezoelectric element charge control circuit which solves the above-mentioned problem by providing two continuously connected sample and hold circuits in a feedback path. With the goal.

[0008]

[MEANS FOR SOLVING THE PROBLEMS]
FIG. 1 shows a configuration diagram of the principle of the light. FIG.
FIG. 2 is a diagram illustrating the principle of the invention described above, wherein the addition circuit 11 and the gain 1 are increased.
Width unit 12, first sample and hold circuit 13, and second
An error integration circuit including a sample hold circuit 14 is provided.
2 shows a control circuit for controlling a charge amount of a piezoelectric element. The adder circuit 11
The error I between the charge amount charged to the piezoelectric element and the target charge amount
The output signal B of the sample hold circuit 14
You. The amplifier 12 amplifies the output signal of the adder circuit 11 and
It is assumed that the output signal of the difference integration circuit is O. 1st sample hall
Circuit 13 outputs the output signal O of the error integrating circuit to the piezoelectric element.
The first timer synchronized with the sampling timing of the charge amount of
Imming pulse T₁Hold after sampling. No.
The second sample and hold circuit 14 is a first sample hole.
The output signal A during the hold period of the
Pulse T ₁Second timing pulse T synchronized with_Two
Hold after sample.

FIG. 1B is a block diagram showing the principle of the present invention. In the figure, the same components as those in FIG. 1A are denoted by the same reference numerals, and the description thereof will be omitted. The feature of the error integrating circuit shown in FIG.
The switching means 15 inputs a signal E of a predetermined level as an initial value to the first sample and hold circuit 13 at the start of operation of the error integration circuit, and then switches and outputs the output signal D of the amplifier 12 to the first sample and hold circuit 13. I do.

[0010]

When the input error I (n) of the error detection circuit is input not periodically but aperiodically, its output error integrated value S
(N) is represented by the following equation.

[0011]

(Equation 1)

As can be seen from the above equation, the error integrated value S
(N) is the input error I (n) and the error integrated value S up to the previous time.
It is obtained by adding (n-1).

Therefore, in the present invention, as shown in FIGS. 1A and 1B, the adder circuit 11 adds the error integrated value B up to the previous time to the input error I. FIG.
In the circuit (A), when the input error I is I (n-1) as shown in FIG. 2, the output signal O amplified and taken out by the amplifier 12 is S (n-1). The output signal S (n-1) is input to the first sample-and-hold circuit 13, after being low-level period sampling of the first timing pulses T ₁ shown in FIG. 2, is a high-level period and hold the T ₁ . Therefore, the output signal A of the first sample-and-hold circuit 13 is defined at the timing pulses T ₁ of the high-level period S (n-1) as shown in FIG.

The second sample and hold circuit 14 is shown in FIG.
As shown, the first timing pulse T ₁The second synchronized with
Timing pulse T_TwoSignal A during the low level period of
(= S (n-1)) and T_TwoHigh level period
By holding the inter-sample value, B
The signal indicated by is output. As a result, the second sample
Signal B (= S (n-1)) extracted from the hold circuit 14
Represents the input error I (= I (n)) at this time and the addition circuit 11
, And then input to the amplifier 12.

The above-mentioned timing pulses T ₁ and T ₂ are synchronized with the sampling timing of the charge amount of the piezoelectric element, and are generated in synchronization with the aperiodic input error I. Then, the integration operation is performed. In the circuit of the present invention shown in FIG. 1 (B), as indicated by SW in FIG. 3, a signal E of a predetermined level is provided from time t ₁ to t ₂ at the start of operation of the error integration circuit.
T a for the switching means 15 selectively outputs as the initial value, the output signal O of the error detecting circuit from time t ₁ as shown in FIG. 3
_The initial value E is output up to 2.

As shown in FIG. 3, the first sample and hold circuit 13 sets the initial value E to a first timing pulse T
₁ to sample and hold outputs a signal A, the second sample and hold circuit 14 this signal A (= E) a second
Sample and hold timing pulse T ₂ of the and outputs a signal B. At time t ₂ , the switching means 15 switches so as to input the output signal D of the amplifier 12 to the first sample and hold circuit 13 as indicated by SW in FIG.

As a result, the switching means 15 outputs O in FIG.
As indicated by, and then from the time t ₂ timing pulse T ₂
It is but until it is entered twice retrieved value obtained by adding the input error I ₁ to the initial value E, thereafter taken out sum signal of the input error and the previous output signal each time the timing pulse T ₂ is input . In the present invention, since a certain initial value E is taken out immediately after the operation of the integrating circuit is started, the response is fast.

[0018]

FIG. 4 is a circuit diagram showing an embodiment of a main part of the present invention. In the figure, terminals 21, 22, 23, 24, and 25 are an initial setting signal, a timing signal, a charge current value of the piezoelectric element, a charge designation value indicating a target charge amount, and an initial value corresponding to the above-mentioned predetermined level signal E, respectively. Values are entered respectively. The initialization signal input to the terminal 21 is a reset signal generated by turning on an ignition switch of the internal combustion engine when the piezoelectric element is used as a pressurizing actuator of a fuel injection valve of the internal combustion engine as described later. is there. The timing signal input to the terminal 22 is, for example, a fuel injection signal. In this embodiment, the initial setting timing generation circuit 26, the error integration and current integration timing generation circuit 2
7, current integration circuit 28, charge hold circuit 29, error calculation circuit 30, error integration circuit 31, gate circuits 32, 3
3. It comprises switch circuits 34 and 35. The switch circuit 34 constitutes the switching means 15 described above.

The initial setting timing generating circuit 26 comprises a monostable multivibrator 36, a flip-flop 37 and an inverter 38.
6 is connected to the clock terminal of the flip-flop 37, and the terminal 21 is connected to the reset terminal of the flip-flop 37 via the inverter 38.

The error integration and current integration timing generation circuit 27 includes an inverter 39 and a monostable multivibrator 4.
0, 41 and 42, and a flip-flop 43. The terminal 22 is connected to the input terminal A of the monostable multivibrator 40 via the inverter 39. The Q output terminal of the monostable multivibrators 40 and 41 is connected to the monostable of the next stage. The input terminals XB of the multivibrators 41 and 42 are connected, the reset terminal of the flip-flop 43 is connected to the terminal 22, and the clock terminal of the flip-flop 43 is connected to the Q output terminal of the monostable multivibrator 41.

The current integrating circuit 28 is an integrating circuit comprising a resistor 44, an operational amplifier 45, a capacitor 46 and a switch circuit 47. A parallel circuit of the capacitor 46 and the switch circuit 47 is provided between the output terminal and the inverting input terminal of the operational amplifier 45. It is connected.

The current integration circuit 28 integrates the input charging current value while the switch circuit 47 is off, and
During the ON period, the charge stored in the capacitor 46 is discharged through the switch circuit 47 to reduce the output to zero and prepare for the next integration operation. The output terminal of the operational amplifier 45 is a resistor 48
Is connected to the connection point between the input terminal of the sample and hold circuit 49 and the switch circuit 35. The resistance of the resistor 48 is set to a value sufficiently larger than the internal resistance when the switch circuit 35 is turned on.

The error calculating circuit 30 has one end of each of the resistors 50 and 51 connected to the inverting input terminal of the operational amplifier 52, the non-inverting input terminal of the operational amplifier 52 grounded via the resistor 53, and the output of the operational amplifier 52. The configuration is such that a resistor 54 is connected between the terminal and the inverting input terminal. Resistance 50
Is connected to the terminal 24, and the other end of the resistor 51 is connected to the terminal of the sample and hold circuit 49. The error calculation circuit 30 calculates a deviation (error) between a charging current flowing from the terminal 23 to the piezoelectric element and a charge indication value from the terminal 24.

The error integrating circuit 31 has an output terminal of an operational amplifier 52 connected to an operational amplifier 56 and resistors 57 to 5 via a resistor 55.
Output terminal 63 via a non-inverting amplifier having a gain of 9
And the input terminal of the sample and hold circuit 60,
Further, the output of the sample hold circuit 60 is connected to the non-inverting input terminal of the operational amplifier 56 via the sample hold circuit 61 and the resistor 62.

The common connection point of the resistors 55 and 62 corresponds to the adder circuit 11, and includes an operational amplifier 56 and resistors 57 to 59.
Corresponds to the amplifier 12 having the gain of 1, and the sample and hold circuits 60 and 61 correspond to the sample and hold circuits 13 and 14. A switch circuit 34 connected between the terminal 25 and the output terminal 63 constitutes the switching means 15. The output terminal 63 is a DC-DC of FIG.
It is connected to the input terminal of converter 72.

Sample hold circuits 49, 60 and 61
Is constituted by an integrated circuit (IC) having a known configuration. For example, the AD585A can be used. The input signal is sampled while the high-level signal is applied to the hold terminal, and the low-level signal is applied to the hold terminal. During the application period, the sampled value is held.

Next, the operation of this embodiment will be described. First, a low-level reset signal generated by turning on an ignition switch is input to a terminal 21 as an initialization signal. Then, the initial setting signal is applied to the reset terminal of the flip-flop 37 via the inverter 38, and resets it. As a result, a low-level signal is extracted from the Q output terminal of the flip-flop 37, and the switch circuits 34 and 35 are turned on, respectively.

When the switch circuit 34 is turned on, the terminal 2
The signal (initial value) E of a predetermined level from 5 is applied to the input terminal of the sample and hold circuit 60 through the switch circuit 34. The signal E at the predetermined level is supplied to the error integration circuit 31.
Is set in advance to a value near the signal level in the steady state. On the other hand, when the switch circuit 35 is turned on, the terminal 2
4 is applied to the input terminal of the sample and hold circuit 49 via the switch circuit 35. Terminal 21
Gate circuit 32 in response to a low-level initialization signal.
Since each of the output timing signals T ₁ and T ₂ becomes high level, the sampling and holding circuit 49,
60 and 61 perform a sampling operation.

The above-mentioned initialization signal rises from a low level to a high level after a predetermined time, and is thereafter maintained at a high level. The rise of the initial setting signal, the monostable multivibrator 36 for a predetermined time determined by the resistor R ₄ and a capacitor C _4, and outputs a low level signal from the XQ output terminal. The flip-flop 37 applies a signal from the XQ output terminal of the monostable multivibrator 36 to the clock terminal, and outputs a high-level signal to the data input terminal when the clock terminal rises from a low level to a high level after the predetermined time. Latching, thereby outputting a high-level signal from the output terminal Q, turning off the switch circuits 34 and 35, respectively.

On the other hand, a timing signal synchronized with the injection timing of the fuel injection valve from the terminal 22 starts to be input to the terminal 22. This timing signal is an aperiodic signal as shown in FIG. 5 (A), and is applied to the input terminal A of the monostable multivibrator 40 and the control terminal of the switch circuit 47 through the inverter 39. As shown in FIG. 5B, a high-level signal P _{1 for a} predetermined time determined by the resistor R ₁ and the capacitor C ₁ is output from the Q output terminal of the stable multivibrator 40,
The switch circuit 47 is turned off, and the current integration is started by the current integration circuit 28. Predetermined time P ₁ described above is set with a margin to the time integrating operation of the current integration circuit 28 is ended.

The Q output signal of the monostable multivibrator 40 is input to the input terminal XB of the monostable multivibrator 41, and the monostable multivibrator 4 falls at the falling edge.
1 is triggered and Q and X of the monostable multivibrator 41 are
Figure from the output terminals of the Q 5 (C), to output a pulse having a predetermined time width P ₂ determined by the resistor R ₂ and capacitor C ₂ as shown in (D). In this predetermined time P ₂ is a sample-hold circuit 49 and 61, the input is set to a time which is stable sampling.

The output signal of the Q output terminal of the monostable multivibrator 41 (FIG. 5C) is applied to the input terminal XB of the monostable multivibrator 42, and the falling of the signal triggers the monostable multivibrator 42, resistor R ₃ and to output the signal shown in FIG. 5 (F) for a predetermined time P ₃ low level determined by the capacitor C _3. In this predetermined time P ₃ is a sample and hold circuit 60, the input is set to a time which is stable sampling.

The Q of the monostable multivibrator 41
The output signal of the output terminal (FIG. 5 (C)) is applied to the clock terminal of the flip-flop 43, and latches the high-level signal of the data input terminal at the rising edge. The output signal of the Q output terminal of the flip-flop 43 is applied to the enable terminal of the monostable multivibrator 42 to enable the high-level period and to disable the low-level period.

The flip-flop 43 is set by the rise of the timing signal (FIG. 5A) from the terminal 22. Therefore, the flip-flop 43 is provided to enable the operation of the monostable multivibrator 42 only when the Q output signal of the monostable multivibrator 41 rises, and the noise may cause the monostable multivibrator 42 to malfunction. To prevent

As described above, the output signal (FIG. 5) extracted from the XQ output terminal of the monostable multivibrator 42
(F)) is supplied to the gate circuit 33, where the terminal 21
FIG. 5 is obtained by performing a NAND operation with a high-level signal.
After being the signal shown in (G), wherein applied to a first hold terminal of the sample hold circuit 60 as a timing pulse T _1, the sampled values to the high-level period to hold the next low-level period.

The output of the monostable multivibrator 41 is
The signal shown in FIG.
The gate circuit 32 negates the high level signal from the terminal 21.
After the logical product is taken and the signal shown in FIG.
The second timing pulse T _TwoAs sample hold
Applied to the hold terminals of circuits 49 and 61. In addition,
The timing pulse T shown in FIGS.₁, T_Two
Is the timing pulse T shown in FIGS.₁, T_Two
, But have substantially the same polarity. Meanwhile, the end
The charging current to the piezoelectric element input to the element 23 is
The switch circuit 47 is turned off simultaneously with the falling of the
After being integrated by the current integration circuit 28,
It is supplied to a sample and hold circuit 49 through a resistor 48.
Here, it is held after the sample. This sump
Of the signal held after sampling by the
The value indicates the amount of charge of the piezoelectric element,
Via the resistor 51 and the charge indication value input from the terminal 24
Then, the signals are added (substantially subtracted) to obtain an error signal.

That is, the error signal is a signal of a level corresponding to the error between the actual charge amount of the piezoelectric element and the target charge instruction value.
After being inverted and amplified by the circuit composed of the circuits 3 and 54, the input signal I is supplied to the non-inverting input terminal of the operational amplifier 56 via the resistor 55. On the other hand, a signal (corresponding to the signal B) from the sample hold circuit 61 is input to the non-inverting input terminal of the operational amplifier 56 via the resistor 62.

The circuit including the operational amplifier 56 and the resistors 57 to 59 non-inverts the addition signal of the error signal I input via the resistor 55 and the signal B input from the sample hold circuit 61 via the resistor 62. amplified, while outputting the resulting signal output signal to the terminal 63 (voltage instruction value) as O, and input to the sample-and-hold circuit 60, where the high-level period of the Figure 5 timing pulses T ₁ shown in (G) in it is held at the low level period of the sample after T _1.
The output signal A of the sample and hold circuit 60 is input to the sample-and-hold circuit 61, the sample after T where a high level period of the timing pulse T ₂ shown in FIG. 5 (E)
It is held during the low level period of ₂ .

According to the present embodiment, the timing signal input to the terminal 22 and the charging current input to the terminal 23 are synchronized with each other and are input non-periodically. In this case, since the integration operation can be performed in synchronization with the sample timing, an accurate error integrated value can be obtained at the output terminal 63. Therefore, according to the present embodiment, the PID control accuracy can be improved.

FIG. 6 is a time chart showing the timing pulse T ₂ , the input error signal I, the output signal O, and the output signal B of the sample and hold circuit 61, respectively. As shown in the figure, a signal obtained by integrating the input error signal I is taken out as an output signal. FIG. 7 shows the timing pulse T ₂
The shows a time chart of the error integrator 31 when a long period than the timing pulses T ₂ of the FIG. As shown in FIG. 7, the sampling interval becomes longer when the timing pulse T ₂ is the long period, the waveform of the output signal O has a waveform having a larger level difference.

FIG. 8 shows a time chart of this embodiment immediately after the initial setting. Period P _a has a value immediately after the initial setting, the output signal A of the sample and hold circuits 60, 61, B is respectively the signal level E. Subsequently, the switch circuit 34
There is turned off, in a period P _b to the second timing pulse T ₂ after the input of the first timing pulses T _1, T ₂ is input, only the signal A is added to the input signal I, the second During the period P _c of timing pulses T _1, T ₂ later is input, if the input signal I is constant, the signal a, B goes by successively adding I have the potential difference between the input signal I to each other.

According to the present embodiment, the value E corresponding to the error integrated value in the steady state is input at the time of the initial setting, so that the electric charge is not accumulated in the integrating circuit as in the prior art. In order to start the integration from the integration value zero, the output does not start from zero and the response does not become slow. It is also possible to hold the learned values of the previous values in the sample and hold circuits 60 and 61 and start based on the learned values.

By the way, the output signal O of the error integration circuit 31 is supplied to the DC input terminal 63 of the circuit shown in FIG.
It is applied as a voltage instruction value Vi to -DC converter 72 where it is converted into high voltage V _O according to Vi. D
The output high voltage V _O of the C-DC converter 72 is applied to the power supply capacitor 73 to charge it. On the other hand, the thyristors 75 and 76 in FIG. 9 are configured to be switching-controlled by an ignition circuit (not shown) connected to the gate, and when one is on, the other is off, and
Switching control is performed so that on and off are alternately repeated.

When the thyristor 75 is turned on, the charge of the power supply capacitor 73 is applied to the piezoelectric element 78 through the choke coil 74 and the thyristor 75. That is, when the thyristor 75 is on, the current I
₁ flows, and a voltage V _P higher than V ₀ is stored in the piezoelectric element 78 which is a capacitive load due to resonance.

Thereafter, when the thyristor 76 is turned on, the charging load of the piezoelectric element 78 is discharged through the thyristor 76 and the choke coil 77. Therefore, when the thyristor 76 is turned on, the discharge current I ₂ to the orientation shown flows into the thyristor 76 and the choke coil 77, the terminal voltage V _P of the piezoelectric element 78 by the overshoot is reduced to a negative voltage.

When the voltage V _O is 320 V, FIG.
A current I ₁ having a peak value of 6 A flows when the thyristor 75 is turned on as shown in FIG. 7B, and a current I _{2 having a} peak value of 6 A is made when the thyristor 76 is turned on as shown in FIG. flows, thereby the terminal voltage V _P of the piezoelectric element 78 is a positive-side peak value as shown in (a) is 6
It becomes a pulse-like waveform having a peak value of 00 V and a negative peak value of -200 V. The charging current I ₁ of the piezoelectric element 78 described above is 4
Is also input to the terminal 23 of the.

FIG. 11 is a circuit diagram of the first embodiment of the present invention, which collectively shows FIGS. 4 and 9 in this case. 4, the same components as those in FIGS. 4 and 9 are denoted by the same reference numerals,
The description is omitted. In FIG. 11, a timing generation circuit 101 is a circuit section including an initialization timing generation circuit 26 and an error differentiation and current integration timing generation circuit 27 in FIG. 4, and a control section 102 in FIG. All circuit sections except the generating circuits 26 and 27.

The input terminal 23 of the control unit 102 (that is, the input terminal of the current integration circuit 28) is connected to the current transformer of FIG.
It said charging current I ₁ taken out of the 103 is supplied.
As a result, the DC-
The output high voltage V _O of the DC converter 72 is equal to the charging current I _1.
Is feedback-controlled so as to become the charge instruction value. Since the capacitance of the piezoelectric element 78 changes depending on the temperature, the amount of charge per energization fluctuates if the output high voltage V ₀ of the DC-DC converter 72 is constant. However, the amount of charge can be stabilized by the above feedback. it can.

The piezoelectric element 78 is used, for example, as a pressurizing actuator of a fuel injection valve 80 shown in FIG. In the figure, inside a housing 81 of the fuel injection valve 80,
A needle 83 slidably inserted to control opening and closing of the nozzle port 82, a needle pressurizing chamber 85 formed around a conical pressure receiving surface 84 of the needle 83, and slidably inserted into the housing 81. Piston 86 and housing 8
And a disc spring 87 for urging the piston 86 toward the piezoelectric element 78.
And a pressure control chamber 88 formed between the needle 83 and the piston 86, and a compression spring 89 for urging the needle 83 toward the nozzle port 82.

The pressure control chamber 88 communicates with a needle pressurizing chamber 85 via a throttle passage 90 formed around a needle 83, and the needle pressurizing chamber 85 is connected to a high-pressure chamber via a fuel passage 91 and a fuel distribution pipe 92. It communicates with the pressure accumulating chamber 93 filled with fuel. Accordingly, high-pressure fuel in the pressure accumulating chamber 93 is guided into the needle pressurizing chamber 85, and a part of the high-pressure fuel is sent into the pressure control chamber 88 via the throttle passage 90. The fuel pressure in the needle pressurizing chamber 85 and the fuel pressure in the pressure control chamber 88 are almost as high as those in the accumulator chamber 93.

When the electric charge is charged in the piezoelectric element 78, the piezoelectric element 78 contracts, and as a result, the piston 86 rises, so that the fuel pressure in the pressure control chamber 88 drops rapidly. As a result, the needle 83 moves up, and fuel is injected from the nozzle port 82.

Next, when the charge of the piezoelectric element 78 is discharged, the piezoelectric element 78 expands, so that the piston 86 descends, and the fuel pressure in the pressure control chamber 88 rapidly increases.
As a result, the needle 83 descends to close the nozzle port 82, and the fuel injection is stopped.

As described above, according to the present embodiment shown in FIG. 4, by using the sample and hold circuits 49, 60 and 61 having high impedance, the sample value can be held for a long time. Even if the input signal is not input for a long time, an accurate error integrated value can be held. Except for the temperature drift, there is no drift of the integrated value due to the offset shift peculiar to the integration circuit. Further, in the present embodiment, a digital circuit can be easily formed by combining an A / D converter, a D / A converter, and a latch circuit, and the algorithm of the present embodiment can be incorporated in a computer as controller software. it can.

By the way, the capacitance value of the piezoelectric element 78 depends on the temperature, and the capacitance value increases as the temperature increases, and varies about twice within the operating temperature range. FIG. 13 is a circuit diagram of a second embodiment of the present invention in which a temperature drift due to the temperature dependence of the capacitance value of the piezoelectric element 78 can be removed. In the figure, the same components as those of FIG. 11 are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 13, the temperature sensor 104 detects the temperature of the piezoelectric element 78 and supplies the detected temperature value to the memory 105 as an address signal. The memory 105 stores in advance a correction map for correcting the temperature characteristics of the piezoelectric element 78 such that the voltage decreases as the temperature increases as shown in FIG. The memory 105 refers to the correction map based on the detected temperature value, and sets the corresponding voltage value as the initial value via the terminal 25 via the control unit 102.
Supply to

Thus, according to the present embodiment, the initial value based on the correction map in the memory 105 is supplied at the time of initial setting, so that the charge amount of the piezoelectric element 78 is charged from the initial state including the temperature drift. It is possible to stably operate a system that controls a value according to the indicated value. Accordingly, in the case of an internal combustion engine in which the piezoelectric element 78 is used as a pressurizing actuator of the fuel injection valve 80 as shown in FIG. 12, optimal and accurate fuel injection amount control can be performed immediately after starting.

Even in the case of an internal combustion engine in which the fuel injection valve 80 is provided for each of a plurality of cylinders, the temperature of the piezoelectric element used as the pressurizing actuator of the fuel injection valve 80 has a small difference between the cylinders. 104 need only be provided for a specific one of the cylinders. Further, even when an input signal is not input for a long time that can hold the error integrated value, an optimum initial voltage value can be generated from the memory 105, so that the error integrated value can be reset quickly. .

FIG. 15 is a circuit diagram showing a third embodiment of the present invention. In the figure, the same components as those of FIG. 11 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 15, the input terminal
A drive signal (for example, power supply voltage) for turning on / off the operation of the entire circuit is input to 111. When the drive signal is interrupted (for example, at the time of falling), the off-time timer 112 is started, and when the input of the drive signal is restarted (for example, at the time of rising), the value of the off-time timer 112 is output.

The cut-off timer 112 measures the cut-off time (cut-off time) of the drive signal, and uses the measured cut-off time (digital value) as an address signal when re-inputting the drive signal.
Supply to 113. The voltage instruction value generated by the control unit 102 and extracted from the output terminal 63 is further supplied to the memory 113 as an address signal.

The memory 113 is stored in advance based on the voltage indication value (ie, the final voltage indication value) at the start of the cut-off time measurement by the cut-off time timer 112 and the measurement cut-off time until the drive signal is re-input. A voltage value is calculated with reference to a correction map as shown in FIG. 16 and supplied to the control unit 102 via the terminal 25 as the initial value.

The temperature of the piezoelectric element 78 becomes high during operation, and is cooled after the operation is completed. Therefore, the above cut-off time,
That is, as the elapsed time from the end of the operation of the piezoelectric element 78 to the point of restarting the operation of the piezoelectric element 78 is longer, the temperature of the piezoelectric element 78 is decreased from a high temperature to the vicinity of the temperature of the ambient atmosphere (normal temperature). The longer the value, the longer. This is because the final voltage instruction value corresponds to the temperature of the piezoelectric element 78 at the time when the operation of the piezoelectric element 78 ends. Therefore,
As shown in FIG. 16, the correction map stored in the memory 113 corrects the change in the capacitance value of the piezoelectric element 78 to a small value according to the temperature as the cutting time becomes longer. It becomes a large value and is represented by characteristics as indicated by I, II, and III according to the final voltage instruction value.

As described above, according to the present embodiment, the piezoelectric element 7
8, the temperature and the capacitance value of the piezoelectric element 78 are estimated based on the final voltage instruction value at the end of the operation and the elapsed time (cutoff time) after the end of the operation. Since the voltage value such that the capacitance value becomes a predetermined value is calculated from the correction map and used as the initial value for the error integration circuit 31, the drift including the temperature dependence of the capacitance value of the piezoelectric element 78 is automatically removed. Yes, the system operates stably from the initial state.

The above-described second and third embodiments can be added without changing the conventional system, and can be incorporated in a timing control microcomputer in the form of software.

[0064]

As described above, according to the first aspect of the present invention, since the integration operation can be performed in synchronization with the sample timing, an accurate error can be obtained even when the input signal is input non-periodically. An integral value can be obtained. Further, according to the second aspect of the present invention, since the predetermined voltage is input in advance at the time of the initial setting, the error integrated value can be obtained with a quicker response than in the related art. Further, according to the third and fourth aspects of the present invention, it is possible to correct the drift of the charge amount due to the temperature dependence of the capacitance value of the piezoelectric element and to control the optimum charge amount from the initial state. Have

[Brief description of the drawings]

FIG. 1 is a principle configuration diagram of a main part of the present invention.

FIG. 2 is a time chart for explaining the operation of FIG.

FIG. 3 is a time chart for explaining the operation of FIG. 1 (B).

FIG. 4 is a circuit diagram of an embodiment of a main part of the present invention.

FIG. 5 is a time chart for explaining the operation of FIG. 4;

FIG. 6 is a time chart illustrating an example of an input signal, a timing pulse, and an output signal of FIG. 4;

FIG. 7 is a time chart illustrating another example of the input signal, the timing pulse, and the output signal of FIG. 4;

FIG. 8 is a time chart for explaining the operation at the time of initial setting and an example immediately after that in FIG. 4;

FIG. 9 is a circuit diagram of an example of a control circuit for a piezoelectric element to which an error integration value is input according to the present invention.

FIG. 10 is a time chart for explaining the operation of FIG. 9;

FIG. 11 is a circuit diagram of a first embodiment of the present invention.

FIG. 12 is a diagram illustrating an application example of an example of a piezoelectric element.

FIG. 13 is a circuit diagram of a second embodiment of the present invention.

FIG. 14 is an explanatory diagram of a correction map used in FIG.

FIG. 15 is a circuit configuration diagram of a third embodiment of the present invention.

FIG. 16 is an explanatory diagram of a correction map used in FIG.

FIG. 17 is a diagram showing a general feedback system model.

FIG. 18 is a diagram in which the model of FIG. 17 is rewritten.

FIG. 19 is a diagram illustrating an example of a circuit that realizes the circuit of FIG. 18;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Addition circuit 12 Amplifier 13 and 60 1st sample-and-hold circuit 14 and 61 2nd sample-and-hold circuit 15 Switching means 23 Charging current value input terminal 24 Charge indication value input terminal 25 Initial value input terminal 31 Error integration circuit 36 and 40 , 41, 42 monostable multivibrator 37, 43 flip-flop 49 sample hold circuit 63 voltage indication value output terminal 78 piezoelectric element 101 timing generation circuit 102 control unit 103 current transformer 104 temperature sensor 105, 113 memory 112 disconnection time timer

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F02D 41/00-41/40 H01L 41/083

Claims (4)

(57) [Claims] 1. A piezoelectric element charge charge amount control circuit for supplying an error between a charge amount charged to a piezoelectric element and a target charge amount to the piezoelectric element through an error integration circuit, the error integration circuit comprising: A first sample and hold circuit that samples and holds the output signal of the first sample and hold with a first timing pulse synchronized with the sampling timing of the charge amount of the piezoelectric element; and outputs the output signal of the first sample and hold circuit during a hold period. A second sample-and-hold circuit for holding after sampling with a second timing pulse synchronized with the first timing pulse; and a second sample-and-hold circuit for detecting an error between a charge amount charged to the piezoelectric element and the target charge amount. And an amplification circuit for amplifying the output signal of the addition circuit to obtain an output signal of the error integration circuit. The piezoelectric element charging charge amount control circuit, characterized in that the more becomes configurations when. 2. At the start of the operation of the error integration circuit, a signal of a predetermined level is input to the first sample and hold circuit as an initial value, and then the output signal of the amplifier is applied to the first sample and hold circuit.
2. The circuit according to claim 1, further comprising switching means for switching and inputting to the sample and hold circuit. 3. A temperature detecting means for detecting the temperature of the piezoelectric element, and a voltage having a characteristic that the higher the detected temperature is, the smaller the value is, as the initial value, based on the detected temperature of the temperature detecting means. 3. The control circuit according to claim 2, further comprising an initial value generating means. 4. The value of the output signal of the amplifier at the end of the operation of controlling the amount of charge of the piezoelectric element, and the elapsed time from the end of the operation to the end of the operation of controlling the amount of charge of the piezoelectric element again. The initial value setting means for outputting, as the initial value, a voltage having a characteristic that the longer the operation end elapsed time is, the larger the value is, and the larger the value at the end of the operation is, the larger the value is. 3. The charge control circuit according to claim 2, wherein: