JPS6057076A - Electric current controller of electromagnet valve solenoid - Google Patents

Abstract

PURPOSE:To diminish hardware drastically in its quantity, by setting an electric current detecting resistor wich detects an ON-electric current, in a closed loop. CONSTITUTION:An arithmetic and logic unit 6, at first, reads a prescribed value E, calculates the first duty ratio D, and determines the first period of time of ON. Next, the arithmetic and logic unit 6 sets the output of a port 9 to 1, and makes a transistor 3 switch on. The electric current of an electromagnet valve solenoid 1 increases exponential-functionally, only for a period from when the transistor 3 is switched on until it is switched off next. When the transistor 3 is switched on, at each determined periodic time from this ON-time, and when the transistor 3 is switched off, the arithmetic and logic unit 6 reads the output values from AD transducer 8, and memorizes each value, for a while. After the first period of time of ON has passed, the arithmetic and logic unit 6 sets the output of the port 9 to 0, and makes the transistor 3 switch off.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an improvement in a current control device for a solenoid valve solenoid that controls the energizing current of the solenoid valve to change the degree of opening and closing of the solenoid valve.

Conventional technology and problems Conventional solenoid valves that are controlled by direct current can only operate in two modes: open when energized and closed when de-energized, but in recent years mechanical improvements have been made to solenoid valves and By intermittent current flow at a specified frequency, it becomes possible to arbitrarily control the opening of a solenoid valve, and it has come to be applied to continuous control of the air flow rate of an internal combustion engine. However, the solenoid valve solenoid has a series circuit of an inductance L and a resistance R for equal deflection as shown in Figure 1, and it takes time to reach the specified current after turning on the switch SW.
At the moment when W is turned off, high voltage is generated in the switch part to maintain the previous current, which may cause an arc to fly. Therefore, as shown in Figure 2, the diode D that releases the solenoid current due to the back electromotive force is normally connected to the solenoid valve solenoid S.
Connect in parallel with N. Therefore, the current of the solenoid valve solenoid SN is a current iI flowing through the switch SW to the ground side when the switch is on, and a current i? flowing through the diode D when the switch is off. The opening degree of the solenoid valve is determined by the combined current 1. + i, determined. Therefore, in order to know the correct current value, on-current 1. .

Off-state current 12 must be detected.

FIG. 6 is an electric circuit diagram of a conventional solenoid valve solenoid current control device that detects both the on-current l and the off-current 12 and controls the solenoid valve according to input information such as the opening degree of the solenoid valve. In order to detect both the current and the off-state current 12, a current detection resistor is connected between the solenoid valve solenoid SN and the switching transistor TR2 and in parallel with the diode D.

Current detection resistor R8σ] terminal voltage is generated in resistor R2 by a current mirror circuit consisting of transistor TRt, etc., so the terminal voltage of resistor R2 is converted into a digital quantity by A/D converter ADC, and the main Calculate the value of current 'I + off-current i- and its average value, and calculate 1 J from the average car specified value (DC voltage or digital input).
If IJ'X is smaller, the on-time of the switching transistor TRs is lengthened, and if IJ'X is thicker, the on-time is shortened to correct the average current. In addition, in Fig. S, ■ is the DC power supply, RI, Rs are the resistances, DI, D2
is a diode, AMP is an amplifier, and this amplifier AM
The output pulse of P, that is, the switching transistor TRz
The repetition frequency of the driving pulse is usually 1007 to 1KH.
z, depending on the characteristics of the solenoid valve) J? It is a fixed thing that is determined.

By the way, in the conventional device shown in FIG. 6, in order to detect both the on-current 'Is and the off-current 12, in addition to the current detection resistor Rx, the transistor TRs, 9 diodes DI, D2 are used.
.

It requires components such as resistors R1 to Rj, and the on-current 11. The off-state current l cannot be detected. This is due to the fact that the current detection resistor RX is used in a floating state, variations in the base-emitter voltage VBK of the transistor TR, forward voltage drop v,1 of the diode D1, etc., and differences in temperature characteristics. The voltage generated by the resistor R2 is the voltage generated by the diode D.
This is due to the fact that the forward voltage drop vv2 cannot be greater than 2.

Purpose of the Invention The present invention improves these conventional drawbacks, and
The purpose is to provide a current control device for an electromagnetic valve solenoid that can significantly reduce hardware costs while having control accuracy equal to or higher than conventional devices.

Structure of the Invention FIG. 4 is an explanatory diagram of the structure of the present invention. A switching element SW is inserted into a closed loop circuit between the solenoid valve solenoid SN and the DC power supply V, and a current detection resistor CS is connected to one end of the switching element SW to detect the on-current i flowing through the solenoid valve solenoid SN while the switching element SW is on. Grounded and placed in a closed loop. The detected value of the current detection resistor CS is A/D
It is converted into a digital quantity by the converter AD, and the on-current average value calculating means MS1 calculates the average value of the on-current i1 from the value, and the off-current average value estimating means MSt calculates the value of the diode D while the switching element is off from that value. The average value of the off-state current 12 flowing through the electromagnetic valve solenoid SN is estimated. Further, the average value calculation means MSs calculates the on-current 11 and the off-current i from the on-current average value and the estimated average off-current value.
, the duty ratio calculating means DT calculates the duty ratio of the driving pulse of the switching element from the average value and the designated value input from the outside, and calculates the duty ratio of the driving pulse of the switching element via the driving circuit AMP. to drive.

Embodiment of the Invention FIG. 5 is a block diagram showing an example of the 11-ware configuration of the current control device of the present invention, in which 1 is a solenoid valve solenoid, 2 is a DC power source, 6 is a switching element such as a transistor, and 4 is a A current detection resistor, 5 a diode, 6 an arithmetic circuit consisting of a microcomputer, 7 a drive circuit for transistor B, and 8 an A/D converter. When the output port 9 of the arithmetic circuit 6 becomes 1'', the transistor 3 is turned on by the output of the drive circuit 7, and current (
When on-current) il flows and the output port 9 of the arithmetic circuit 6 becomes "0", the transistor 6 turns off and the diode 5
Current (off current) to solenoid valve solenoid 1 via t2
flows. During the ON period of the transistor 6, the arithmetic circuit 6 reads the output of the A/D converter 8 which converts the terminal voltage vX of the current detection resistor 4 into a digital value via the input port 10, and uses this input data as the ON current. The on-state current 1. The value of the off-state current 12 is estimated from the value of , and the average value of the composite current 14+i2 is calculated. Then, this calculated average value and the specified value E inputted from the outside are
If the average value is smaller than the specified value E, the duty ratio (
On period/(On period + Off period)) is increased, and if the average value is greater than the designated value E, the duty ratio of the next drive pulse is decreased.

FIG. 6 is an operation flowchart of the arithmetic circuit 6, and 81
~S15 indicates each step.

When the arithmetic circuit 6 is activated by means not shown, it first reads the designated value E (Sl). This specified value E is for externally specifying the opening degree of the solenoid valve, and is given as a digital amount in this embodiment. Next, the arithmetic circuit 6 calculates the first duty ratio by multiplying the designated value E by the coefficient k.
2) The first on-time 1. is determined by multiplying the preset fixed period (driving period of the transistor 6) of the solenoid valve by its duty ratio T. is determined (S3). Incidentally, the above coefficient is a coefficient for calculating the duty ratio DQ from the specified value E, and a standard value is set in advance in a memory or the like in the arithmetic circuit 6.

Next, the arithmetic circuit 6 sets the output port 9 to 1' and turns on the transistor 3 (S4). Figure 7 shows an example of the current flowing through the solenoid valve solenoid 1, with the vertical axis representing the current value and the horizontal axis representing the time t when the transistor 3 was first turned on. The current of the electromagnetic valve solenoid 1 increases exponentially by the time t from when the transistor 3 is turned on (to) until the next time the transistor 3 is turned off. The arithmetic circuit 6 calculates when the transistor 3 is turned on (
1, ), and from this point on, the output value of the A/D converter 8 is read at every predetermined period of 1 s and at the time (tn) when the transistor 6 is turned off (85 to 89), and each read value is Address M of internal memory, etc. - Temporarily stored in Mn. For example, in FIG. 7, from time tO+ tO to 7 times every t3 elapses and tt(tn
) current value i at time 819. -i7. The value of in is sampled. Note that the shorter the sampling period, the higher the detection accuracy.

Next, when the first ON period t1 has elapsed, the arithmetic circuit 6 sets the output port 9 to 10'' and turns off the transistor 6 (810).
The conduction current is determined by the time ('r t
t) decreases exponentially.

When the first off period (T-t□) has elapsed (sll), the arithmetic circuit 6 turns on the A/D immediately before the transistor 60 turns on.
The value of the converter 8 is read (812) and temporarily stored at address Mx in an internal memory or the like.

Based on the current value requested for the above processing, the arithmetic circuit 6 calculates
In step 814, the next on period (tz)? : is calculated, and this calculation is executed, for example, according to the flow shown in the eighth factor. That is, in FIG. 8, 820
to 834 indicate each step, and in step S2D, the arithmetic circuit 6 calculates the middle time (t
Calculate the current value at z2). This can be represented by the current value at the time closest to t〆2 among the sampled values from io to 1f.

Next, the arithmetic circuit 6 determines the path of the on-current i from the current value corresponding to tV'2 (S21). For example, as shown in FIG. 9, when the on-current i changes as shown by the solid line 20, the off-current 12 changes as shown in the solid line 21, and the on-current i changes as shown in the broken line 22. When the off-state current 12 changes as shown by the dashed line 26, and when the on-state current 11 changes as shown in the dashed-dotted line 24, the off-current i large changes as shown in the dashed-dotted line 25, so it corresponds to t/2. From the current value, on-current 1. Use a map etc. to determine which of the three paths above
This is to infer a change in intention. And off-state current i!
If it is close to the path of the broken line 23, set a as the proportionality constant P, which will be described later (822*523), and the off-state current 12 is close to the path of the solid line 2.
If the path is close to 1, set b as the proportionality constant P.8
24, 825), if the off-state current 12 is close to the path of the dashed dotted line 25, C is set as the proportionality constant P (826, 5
27).

Next, the arithmetic circuit 6 calculates the average value i OFF of the off-state current l using the following equation (828).

1opr = (in-ix) Xp+ i, +++
(1) Here, ln is the current value immediately before the transistor 3 is turned off, and iX is the current value when the transistor 3 is turned on again.

As can be seen from equation (1), the proportionality constant P is the average value l. 7F
This constant is calculated from the difference between in and lx, which is the difference between , b, and e. Although six paths for on-current and off-current are set above, more paths for on- and off-current can be assumed by increasing the number of detection points for path discrimination (corresponding to t〆2). , it is possible to reduce the approximation error.

Next, the arithmetic circuit 6 calculates the average value l of the on-current i. M is calculated using the following formula (829).

Next, the previous on-current ij and off-current 12 are calculated using the following formula.
0 Calculate the average current 1 m of the total value (S?) 0).

1oNX t+ tovl, ('r-t)tm----
f3) Here, t is the previous on period, and T is the period of the drive pulse of the transistor 6.

Next, the arithmetic circuit 6 reads the designated value E, updates the value (831), and calculates the theoretical average value 1e for the designated value E using the following equation (532).

ie = E g is a proportionality constant between E and ie.

Next, the arithmetic circuit 6 calculates the previous average value 1m and the theoretical average value 1m.
e and the difference Δi are expressed as ΔI=im−1e−−−(5) (S3+), and then the current on period t!
is calculated by the following formula (S54).

Here, q is a correction coefficient determined by actual measurement.

That is, if the previous average current im is larger than the theoretical average value 1e calculated based on the designated value E, Δi becomes positive and the next on-period t2 is shortened, and if it is smaller, Δi becomes a negative value. The next on-period t, will be increased.

Now, when the arithmetic circuit 6 calculates the next on-period using the above process, it stores the current value iz when the transistor 60 is turned on again in the address MO as the lo value used for calculating the next on-period. S15), the process returns to step s6. Therefore, the processes of steps s6 to 815 are repeated.

Note that the path of the off-state current i passes through the triangles u, V, and W, as shown in FIG. 9, for example, so if some error is acceptable, the average value of the off-state current 12 is i. The FF may be calculated by the following equation regardless of the path of the on-current.

'0FF= (in-t

As described in detail, according to the present invention, only the on-current of the solenoid valve solenoid is detected by the current detection resistor, and the off-current is estimated from the on-current value. It requires very little hardware, and since it does not detect off-current, one end of the current detection resistor can be grounded, which has the advantage of improving on-current detection accuracy compared to conventional methods.
The overall control accuracy can be made equal to or higher than that of the conventional method.

[Brief explanation of the drawing]

1 and 2 are configuration explanatory diagrams of a solenoid valve solenoid, FIG. 6 is an electric circuit diagram of a conventional solenoid valve solenoid current control device, FIG. 4 is a configuration explanatory diagram of the present invention, and FIG. 5 is a diagram of the present invention. 6 and 8 are operational flowcharts of the arithmetic circuit, FIG. 7 is a diagram showing an example of the waveform of the current flowing through the solenoid valve solenoid, and FIG. FIG. 9 is a diagram explaining the principle of off-state current estimation. 1 is a solenoid valve solenoid, 2 is a DC power source, 3 is a transistor, 4 is a current detection resistor, 5 is a diode, and 6 is an arithmetic circuit. Patent Applicant Fujitsu Ten Ltd. Agent: Patent Attorney Tamamushi Go, one person outside the department Figure 1 Figure 2 Figure 4 Factor 5 Figure 7 Figure 9

Claims (1)

[Claims] An electromagnetic valve that controls the duty ratio of a drive pulse with a predetermined repetition frequency of a switching element inserted in a closed loop between the solenoid valve solenoid and a DC power supply so that the average value of the energizing current of the solenoid valve solenoid matches the value corresponding to the specified value. In a current control device for a valve solenoid, a current detection resistor whose one end is grounded detects the on-current flowing through the electromagnetic valve solenoid while the switching element is on, and A that converts a detected value of the current detection resistor into a digital quantity. /On' which reads the output value of the D converter and calculates the average value of the on-state current.
current average value calculating means; and an off-current average for estimating an average value of an off-current flowing through a diode connected in parallel to the solenoid valve solenoid while the switching element is off from the immediately preceding on-current value. a value estimating means, an average value calculating means for calculating an average value of the sum of the on current and the off current from the estimated average value of the off current and the on current average value, and an average value calculated by the average value calculating means. and duty ratio calculation means for calculating a duty ratio of the drive pulse from the specified value and the specified value.