JPH0544743Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an output correction control device for a hot-wire flowmeter that measures the intake air amount of an internal combustion engine.

[Prior art]

Generally, in the case of automobile engines, in order to measure the amount of intake air used as a calculation factor for fuel injection pulses, a hot wire flowmeter is used, which has a hot wire resistor 1 disposed in the intake passage, for example, as shown in FIG. is used.

Here, the hot wire resistor 1 includes a plug-in frame 2 disposed in the intake passage, a hot wire resistor 3 made of platinum wire stretched between the frame 2, and pins 4, 4.
The temperature compensating resistor 5 is arranged through the temperature compensating resistor 5. The hot wire flow meter is configured to include a bridge circuit consisting of the hot wire resistor 3, temperature compensation resistor 5, flow rate adjustment resistor, and output resistor (none of which are shown), and increases the intake air flow rate (flow rate). By utilizing the fact that the degree of cooling of the hot wire resistor 3 increases and the resistance value decreases, the intake air amount is read from the voltage value of the output resistance.

[Problem that the invention attempts to solve]

However, since the hot wire resistor 1 is disposed in the intake passage, it is easily contaminated by deposits such as dust in the intake air and blow-by, and as shown in FIG. When it is dirty, as the intake air amount Q increases compared to the normal state, the output voltage V decreases, that is, the detection characteristics deteriorate, and the influence becomes greater (see FIG. 3).

However, the basic injection amount T _P by the fuel injector is T _P = K × Q / N ... (1) However, N: engine rotation speed K: constant, but if the intake air amount Q The fact that it decreases as the fuel consumption increases means that the basic injection amount T _P in equation (1) also decreases, and in relation to the air-fuel ratio, there is a strong tendency toward lean, leading to problems such as poor starting and poor acceleration. be.

To solve this problem, when the predetermined burnout condition is reached, the ignition switch is turned off.
In connection with the operation, there is also known a device in which a large current is passed through the hot wire resistor to burn off deposits on the hot wire resistor at high temperature.

However, when burning off deposits at high temperatures, the problem is that if the burning process is repeated many times, the hot wire resistor made of platinum will deteriorate prematurely, leading to wire breakage. be.

The present invention was developed in view of these problems, and the output characteristics of a hot wire flowmeter are designed to learn whether the output characteristics of the hot wire resistance have changed from the initial state and to correct the output characteristics by adding the change value when contamination occurs. An object of the present invention is to provide a correction control device.

[Means for solving problems]

In order to solve the above problems, the present invention, as shown in the functional block diagram of FIG. a throttle valve switch that detects the opening degree of the throttle valve; a storage means that stores characteristic values first outputted from the hot wire flow meter and the throttle valve switch as initial values A ₀ and B ₀ ; Based on the characteristic values A ₁ and B ₁ output from the hot wire flowmeter and the throttle valve switch after using the meter, the difference α between the characteristic values A ₀ and A ₁ is determined.
a calculation means for calculating α=A ₀ −A ₁ , and a difference value α outputted from the calculation means is compared with a predetermined value, and when it is equal to or greater than the predetermined value, it is determined that dirt has occurred in the hot wire resistor. and a correction calculation for calculating a corrected characteristic value A _{2 as A 2 =} A ₁ + α from the characteristic value A ₁ and the difference value α when the stain occurrence is determined by the stain determination unit. It consists of means and means.

[Effect]

With this configuration, the difference value (change value) α can be added to the characteristics when dirt occurs, so the characteristics in the initial state of use can be maintained at all times, and the tendency to become lean can be prevented. be able to.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 2 to 5.

First, in FIG. 2, reference numeral 11 denotes a hot wire flowmeter, and the hot wire flowmeter 11 includes a hot wire resistor 11A disposed in the intake passage as part of a bridge circuit.
The output voltage corresponding to the intake air amount Q is set so that when there is no deposit on the hot wire resistor 11A at the initial stage, the initial characteristic is as shown by A in FIG. It is designed to output V.

Reference numeral 12 denotes a throttle valve switch, which detects the opening of the throttle valve that sets the opening of the intake passage, and outputs an opening signal shown by throttle valve switch characteristic C in FIG. . It should be noted that since the throttle valve switch 12 is normally installed in a clean place, its characteristics remain approximately constant even after use.

Reference numeral 13 denotes a correction control device composed of, for example, a microcomputer, and the correction control device 13
consists of a processing circuit consisting of a CPU, a storage circuit consisting of RAM, ROM, etc., and an input/output circuit.The input side is connected to the hot wire flowmeter 11 and the throttle valve switch 12, and the output side is connected to the injection amount, which will be described later. It is connected to the arithmetic unit 14. Here, the said
Initial values A ₀ and B ₀ from the hot wire flowmeter 11 and the throttle valve switch 12 are stored in the RAM as a data table through the process shown in FIG.
The programs shown in FIGS. 4 and 5 are stored in the ROM. Then, the CPU performs a correction calculation process according to the program, and when dirt occurs, operates to correct the dirt occurrence characteristic B to the initial characteristic A in FIG. 3.

Furthermore, 14 is an injection amount calculation device, and the injection amount calculation device 14 calculates the intake air amount Q obtained based on the output characteristics of the hot wire flowmeter 11 outputted from the correction control device 13, and the crank angle sensor (not shown). Based on the engine rotation speed N, the basic injection amount T _P and various correction amounts are calculated based on the above-mentioned equation (1), and a fuel injection pulse is output to the fuel injector 15.

Although the present embodiment is configured as described above, the processing operation by the correction control device 13 will be explained with reference to the characteristic diagram shown in FIG. 3 and the programs shown in FIGS. 4 and 5.

First, the initial value storage operation at the initial time when the hot wire resistor 11A is not contaminated (normal state) will be described with reference to FIG.

When the process starts, the initial output B ₀ output from the throttle valve switch 12 in step 1 is
At the same time, in step 2, the initial output _A0 output from the hot wire flowmeter 11 is read, and in step 3,
Create an initial map as a data table in RAM. This data table is created as a map in which the initial characteristic A of the hot wire flowmeter 11 and the characteristic C of the throttle valve switch 12 in FIG. 3 are made into a matrix. Therefore, steps 1 to 3 in FIG. 4 are specific examples of the storage means according to the present invention.

Next, the correction calculation process for the output signal output from the hot wire flowmeter 11 will be described with reference to FIG.

First, when the process is started by turning on the engine switch (not shown), the initial outputs A ₀ and B ₀ are read from the initial map in step 11, and the process is started in step 12.
Output from throttle valve switch 12 when in use
At the same time as reading B ₁ , in step 13 the hot wire flowmeter 11
Read output A ₁ when using. Then, in the next step 14, the initial output A ₀ on the initial map B ₀ which is equal to the output B ₁ during use is derived, and the difference value α between the output value A ₀ and the output A ₁ during use is calculated as α=A Calculate as ₀ −A ₁ ...(2). Therefore, steps 11 to 14 are specific examples of the calculation means according to the present invention.

Next, in step 15, the difference value α calculated using equation (2)
Based on , it is compared whether the difference value α exceeds a predetermined range of k%, for example 3%, with respect to the initial output value A ₀ . If the range of k% is not exceeded, the hot wire resistance 11A is assumed to be in a normal state and no contamination has occurred, and the process moves to step 16, where the in-use output _A1 read from the hot wire flowmeter 11 is calculated. It is output as is to the injection amount calculation device 14. On the other hand, when the above k% range is exceeded, the initial output
The difference from _A0 becomes large, and it is determined that the hot wire resistor 11A is contaminated, and the process moves to step 17. Therefore, step 15 is a specific example of the dirt determining means of the present invention.

Furthermore, if the value exceeds the k% range as described above, the corrected output _A2 is calculated from the in-use output A1 read in step 17 and the difference value α calculated in step 14, _{A2 =} Calculate as A ₁ + α ...(3). Therefore, by adding and correcting the difference value α as the change value α to the output A ₁ during use, the characteristic B at the time of dirt occurrence in FIG. 3 is processed to become the characteristic B at the initial time. After this calculation is performed, the corrected output _A2 is outputted to the injection amount calculation device 14 via step 16. In addition,
Step 17 is a specific example of the correction calculation means according to the present invention.

In this way, the characteristic value of the hot wire flowmeter 11 output to the injection amount calculation device 14 through the process of step 16 is always maintained within k% with respect to the initial value _A0 , and the injection amount calculation device 14 The device 14 uses the input characteristic value A ₁ or A ₂ as an intake air amount signal corresponding to the intake air amount Q, calculates the basic injection amount T _P using equation (1), and outputs it to the fuel injector 15. It is possible to prevent the lean trend from occurring.

In the example, the initial map was created in step 3 in Fig. 4, but the initial output
All that is required is to memorize A ₀ and B ₀ , and the creation of the initial map is only one specific example of a memorization method. Furthermore, in step 17 in FIG. 5, after calculating the correction output _A2 , it has been described that it is immediately outputted to the injection amount calculation device 14 from step 16, but the feedback is fed back to step 15 and the determination at step 15 is performed again. The configuration may be such that the output is output from step 16 after the process is completed. Furthermore, the steps
15, k% (for example,
3%), but the determination may be made directly based on a predetermined voltage value (for example, 0.5V).

[Effect of idea]

The output correction control device for a hot-wire flowmeter according to the present invention is as described in detail above, and constantly monitors the output characteristics of the hot-wire flowmeter during use, and performs correction calculations to maintain the initial characteristics when dirt occurs. Because of this structure, even when the hot wire resistor is dirty with deposits, it prevents the occurrence of a significant lean tendency and ensures the desired starting and
Acceleration performance can always be maintained in the initial state of use.

[Brief explanation of the drawing]

Figure 1 is a functional block diagram showing the configuration of the present invention.
Figures 2 through 5 relate to embodiments of the present invention, with Figure 2 being a block diagram showing the circuit configuration of this embodiment, and Figure 3 showing the output characteristics of the hot wire flowmeter and throttle valve switch with respect to the amount of intake air. A line diagram showing
FIG. 4 is a flowchart showing the initial value storage operation, FIG. 5 is a flowchart showing the correction calculation process, and FIG. 6 is an external explanatory diagram showing the state of dirt on the plug-in hot wire resistor. 11...Hot wire flowmeter, 11A...Hot wire resistance, 1
2... Throttle valve switch, 13... Correction control device, 14... Injection amount calculation device, A... Initial characteristics, B... Characteristics when dirt occurs, C... Throttle valve switch characteristics.

Claims (1)

[Scope of utility model registration request] A hot-wire flowmeter including a hot-wire resistance disposed in an intake passage of an internal combustion engine, a throttle valve switch for detecting the opening degree of a throttle valve disposed in the intake passage, and the hot-wire flowmeter and the throttle valve. The initial value is the characteristic value output from the switch.
Based on the storage means for storing A ₀ and B ₀ and the characteristic values A ₁ and B ₁ output from the hot wire flowmeter and the throttle valve switch after using the hot wire flowmeter,
A calculating means for calculating the difference α between the characteristic values A ₀ and A ₁ as α=A ₀ −A ₁ , and comparing the difference value α outputted from the calculating means with a predetermined value, and when the difference value α is equal to or greater than the predetermined value, the above-mentioned a stain determining means that determines that stain has occurred on the hot wire resistance; and when the stain determining means determines that stain has occurred, the characteristic value A ₁ and the difference value α
An output correction control device for a hot-wire flowmeter, comprising correction calculation means for calculating a correction characteristic value A ₂ as A ₂ =A ₁ +α.