JP2002070635A - Internal combustion engine controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress heat generation and generation of high-frequency noises in a microcomputer or a power supply circuit, in an internal combustion engine controller using the microcomputer. SOLUTION: In this controller, the microcomputer 40 constituting an ECU 30 for controlling an engine is provided with a divider circuit 52 dividing a reference clock to generate a system clock, and a register 'X' 60 storing a division value of the divider circuit 52. Calculation processing executed by a CPU 42 sets a value of the. register 'X' 60 to be small in a high engine speed and to be large in a low engine speed. As a result, a frequency F1 of the system clock can be reduced in the low engine speed not requiring high- speed calculation to suppress a heat generation amount in the microcomputer 40 or the power supply circuit 36 without affecting engine control. In the low engine speed, the generation of the high-frequency noises can be suppressed to suppress malfunction caused by the high-frequency noises.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an internal combustion engine control device for controlling an internal combustion engine using a microcomputer.

[0002]

2. Description of the Related Art Conventionally, in a control device of an internal combustion engine, particularly an internal combustion engine for an automobile, a control amount of the internal combustion engine such as a fuel injection amount and an ignition timing is calculated using a microcomputer. Also, in this type of internal combustion engine control device, in order to control the internal combustion engine more precisely, the arithmetic processing by the microcomputer has become complicated, and with the complexity of the arithmetic processing, the processing speed of the microcomputer has been increased. There is a demand for higher speed.

[0003]

However, if the operating clock frequency of the microcomputer is increased in response to this demand and the processing speed of the microcomputer is increased, the power consumption of the microcomputer is increased, and the microcomputer and its The amount of heat generated by the power supply circuit that supplies power increases, and this heat generation causes a problem that the microcomputer and its peripheral circuits malfunction.

The amount of heat generated by the microcomputer and the power supply circuit is substantially proportional to the operating clock frequency of the microcomputer, as shown in FIG. In order to prevent such malfunctions due to heat, it is common to provide cooling radiators (heat sinks) in the microcomputer and peripheral circuits. However, providing such radiators increases the cost of the internal combustion engine controller. Is caused.

[0005] Further, since the internal combustion engine control device is provided near the internal combustion engine, it is easily affected by the heat generated by the internal combustion engine. Therefore, the microcomputer and its peripheral circuits may not be sufficiently cooled by the heat radiation using the radiation fins or the like. On the other hand, as a technique for preventing a malfunction caused by heat of a microcomputer, Japanese Patent Laid-Open No.
Japanese Patent Publication No. 5044 proposes detecting the temperature around a microcomputer and changing the operating clock frequency of the microcomputer according to the detected temperature.

That is, in the technology disclosed in this publication,
By lowering the operating clock frequency of the microcomputer as the ambient temperature of the microcomputer increases, the amount of heat generated by the microcomputer and the power supply circuit is reduced, and the microcomputer and its peripheral circuits are prevented from malfunctioning due to heat. is there.

However, the microcomputer used for controlling the internal combustion engine is different from a general microcomputer in that it performs not only an arithmetic processing of a fixed cycle synchronized with an operation clock but also an arithmetic processing synchronized with the rotation of the internal combustion engine. There is a need to. For this reason, when the technology disclosed in the above publication is applied to the internal combustion engine control device, the operation clock frequency becomes too low during the high-speed rotation of the internal combustion engine, so that the arithmetic processing synchronized with the rotation of the internal combustion engine cannot be normally executed. There is.

That is, when the internal combustion engine is rotating at a high speed, the number of processes to be executed by the microcomputer per unit time increases. Therefore, as described in the above-mentioned publication, the operating clock frequency of the microcomputer decreases as the ambient temperature increases. If this is done, the microcomputer will not be able to execute the arithmetic processing necessary for controlling the internal combustion engine, and this will sometimes lead to the control of the internal combustion engine.

According to the technique disclosed in the above publication, when the temperature around the microcomputer is low, the operating clock frequency of the microcomputer is increased to operate the microcomputer at high speed. There is also a problem that it cannot be reduced efficiently.

Further, when the operating clock frequency of the microcomputer is increased in order to increase the processing speed of the microcomputer, as is apparent from FIG. 5B, the high-frequency noise leaking to the surroundings increases, and the high-frequency noise increases. However, the operation of the microcomputer and its peripheral circuits may be adversely affected. However, the technology disclosed in the above publication cannot efficiently suppress such high-frequency noise.

FIG. 5B shows the relationship between the operating clock frequency and the high-frequency noise. As is clear from FIG. 5, the high-frequency noise is substantially proportional to the operating clock frequency of the microcomputer. The present invention has been made in view of such a problem, and in an apparatus for controlling an internal combustion engine using a microcomputer, by reducing the operating clock frequency of the microcomputer without affecting the control of the internal combustion engine, It is an object of the present invention to efficiently reduce both the power consumption of a microcomputer (and the heat generated by the microcomputer and its power supply circuit) and high-frequency noise.

[0012]

According to a first aspect of the present invention, there is provided an internal combustion engine control apparatus, wherein an operation clock setting means sets an operation clock frequency of a microcomputer to a rotational speed of the internal combustion engine. Is set so that the operating clock frequency becomes lower as the value becomes lower.

Therefore, according to the present invention, the power consumption and high frequency noise of the microcomputer can be efficiently reduced without affecting the control of the internal combustion engine using the microcomputer. Hereinafter, the reason will be described.

First, in the internal combustion engine control device of the present invention, the microcomputer realizes a function as control amount calculation means for calculating a control amount of the internal combustion engine according to the operating state of the internal combustion engine by the processing operation. ,As previously mentioned,
When the microcomputer executes arithmetic processing as control amount arithmetic means, it performs arithmetic processing synchronized with the rotation of the internal combustion engine as well as arithmetic processing of a fixed cycle synchronized with the operation clock. This is because the combustion cycle of the internal combustion engine changes according to its rotation, and it is necessary to control the internal combustion engine in synchronization with the rotation.

For this reason, in the internal combustion engine control device,
Usually, the operation clock of the microcomputer is set corresponding to the maximum rotation of the internal combustion engine so that the arithmetic processing synchronized with the rotation of the internal combustion engine can be executed at the time of high speed rotation of the internal combustion engine. However, it is extremely rare that the internal combustion engine is operated near the maximum rotation speed, and is usually operated between a low speed range and a medium speed range. In this region, even if the operation clock of the microcomputer is set lower than at the time of high-speed rotation of the internal combustion engine, the arithmetic processing for controlling the internal combustion engine can be executed without any problem.

Therefore, in the present invention, the microcomputer is used as a control amount calculating means by changing the operating clock frequency of the microcomputer so that the operating clock frequency of the microcomputer decreases as the rotational speed of the internal combustion engine decreases. The operation clock frequency can be set as low as possible while functioning normally.

As a result, according to the present invention, the power consumption of the microcomputer can be reduced, and the heat generation of the microcomputer and the power supply circuit for supplying power to the microcomputer can be suppressed. A malfunction of the circuit can be prevented.

Further, during normal operation of the internal combustion engine in which the internal combustion engine is operated between a low speed range and a medium speed range, the operation clock frequency of the microcomputer is reduced, so that the generation of high frequency noise can be suppressed. The probability of malfunction of the microcomputer and its peripheral circuits can be sufficiently reduced.

Therefore, according to the present invention, it is possible to cope with the complexity of the arithmetic processing to be executed by the microcomputer and to improve the reliability of the internal combustion engine control device itself. Here, as the operation clock setting means, it is sufficient that the operation clock of the microcomputer can be changed according to the rotation speed of the internal combustion engine. For example, using an oscillation circuit that can control the oscillation frequency as a clock generation source,
The oscillation frequency may be controlled in accordance with the rotation speed of the internal combustion engine, but more preferably, the reference clock output from the reference clock generation means is divided at a constant period. Operating clock generating means for generating an operating clock, and frequency dividing value setting means for setting the frequency dividing value of the reference clock by the operating clock generating means to increase as the rotational speed of the internal combustion engine decreases. Good to do.

In other words, if a variable frequency oscillation circuit is used as a clock generation source and its oscillation frequency is controlled, the cost of the clock generation source itself will increase, but as described in claim 2, If an operation clock is generated by dividing the clock, it is not necessary to use a variable frequency oscillation circuit, so that a clock generation source (reference clock generation means) can be realized at low cost. When controlling the oscillation frequency of the variable frequency oscillation circuit,
The arithmetic operation of the microcomputer may be temporarily unstable due to an operation delay of the oscillation circuit. However, as described in claim 2, the operation clock is generated by dividing the frequency of the reference clock. If the frequency division value is switched in accordance with the rotation speed of the internal combustion engine, the operation clock can be quickly switched to the desired frequency, so that the microcomputer can operate stably.

On the other hand, in the internal combustion engine control device according to the third aspect of the present invention, the microcomputer includes a clock generating means for generating a clock by dividing the operation clock, and the clock generating means for the clock. And counting means for counting the generated clock for clocking to count the current time. Then, the clock generation means for clocking calculates the frequency division value when dividing the operation clock in accordance with the frequency division value set by the frequency division value setting means (claim 2) constituting the operation clock setting means. By performing the correction, the operation is performed so that the clock for clocking always has a constant cycle.

That is, as an internal combustion engine control device, a microcomputer conventionally takes in detection signals from various sensors as operating state detecting means, or controls a control amount corresponding to a control amount calculated by an arithmetic processing as a control amount calculating means. When a signal is output, an input / output timing of the signal is configured to be set according to an output from a counting unit that measures the current time.
In this type of internal combustion engine control device, if the counting means for measuring the current time counts the operation clock of the microcomputer as it is, the current time can be normally updated by the counting means due to a change in the operating clock frequency. I can no longer do it.

Therefore, in the internal combustion engine control device according to the third aspect, when the present invention (claims 1 and 2) is applied to this type of internal combustion engine control device, the counting means does not malfunction. As described above, the frequency dividing value set by the frequency dividing value setting means is input to the clock generating means, and the clock generating means generates the frequency dividing value when generating the clock based on the frequency dividing value. Is corrected so that a clock for clocking with a constant period can always be generated.

As a result, according to the internal combustion engine control device of the third aspect, the count value of the counting means for counting the clock for clocking always changes in accordance with the current time. The current time can be accurately grasped from the count value of the means, so that the control accuracy of the internal combustion engine can be ensured.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system configuration diagram showing an overall configuration of an internal combustion engine control device according to an embodiment to which the present invention is applied. It should be noted that the internal combustion engine control device of the present embodiment is a gasoline engine (hereinafter simply referred to as an engine) 1 mounted on an automobile.
Is optimally controlled according to the operation state.

As shown in FIG. 1, in the engine 1, a combustion chamber 5 is formed by a cylinder 2, a piston 3, and a cylinder head 4. In the combustion chamber 5, an ignition plug 6 is provided. An intake system of the engine 1 includes an intake manifold 8 that communicates with the combustion chamber 5 via an intake valve 7, and a fuel injection valve (injector) that injects fuel into the intake manifold 8.
9, an intake pipe 10 communicating with the intake manifold 8, a surge tank 11 for absorbing pulsation of intake air, a throttle valve 12, an air cleaner 13, and an air bypass for controlling the amount of intake air to the engine 1 when the throttle is fully closed. It comprises a valve 28. The exhaust system of the engine 1 has an exhaust manifold 15 that communicates with the combustion chamber 5 via an exhaust valve 14. Further, the engine 1 includes an igniter 1 for outputting a high voltage necessary for ignition.
6, a distributor 17 that distributes and supplies a high voltage generated by the igniter 16 to the ignition plug 6 of each cylinder in conjunction with a crankshaft (not shown).

On the other hand, the engine 1 is provided with a water temperature sensor 20 provided in a cooling system of the engine 1 for detecting a cooling water temperature, and provided in an air cleaner 13 as operating state detecting means for detecting an operating state of the engine 1. Intake air temperature sensor 21 for detecting the temperature of the intake air to be sent, and throttle position sensor 2 for detecting the opening of throttle valve 12
2. An intake pipe pressure sensor 23 communicating with the intake pipe 10 to measure the intake pipe pressure, and an oxygen concentration sensor 2 provided in the exhaust manifold 15 for detecting the residual oxygen concentration in the exhaust gas.
4. A rotation angle sensor 25 is provided in the distributor 17 and outputs a rotation angle signal at each predetermined rotation angle of the camshaft of the distributor 17 (for example, every integer multiple of 0 ° to 30 ° crank angle).

The detection signals from these various sensors are input to an electronic control circuit (hereinafter referred to as ECU) 30. The ECU 30 determines the injector 9, the igniter 16, the air bypass valve based on the input various detection signals. The engine 1 is controlled by driving 28 and the like.

FIG. 2 is a block diagram showing the configuration of the ECU 30. As shown in FIG. 2, the ECU 30 is mainly configured by a microcomputer 40, and includes, as a peripheral circuit thereof, a detection signal from among the various sensors described above.
A waveform shaping circuit 32 for shaping a waveform of a clock signal such as a rotation angle signal, and various actuators (injector 9, igniter 16, air bypass valve 28) to be controlled.
Output driver circuit 34 for outputting a drive signal to the
And a power supply circuit 36 that receives power supply from a vehicle-mounted battery and generates a power supply voltage (constant voltage) Vcc for operating the above-described units.

The microcomputer 40 performs various arithmetic processing for engine control based on the detection signals from the various sensors, and executes a control amount arithmetic means as a control amount arithmetic means.
A PU 42, a ROM 44 in which a control program, initial data and the like are stored in advance, and a RAM 4 for temporarily storing various signals input to the ECU 30 and data necessary for calculation.
6, and an I / O module 48 connected to each of these units via a bus, for taking in detection signals from the various sensors and outputting control signals.

Here, the I / O module 48 receives detection signals from the various sensors directly or the waveform shaping circuit 3.
2, the analog detection signal directly input from the sensor is converted into digital data by a built-in A / D converter (A / D shown in the figure) and taken into the microcomputer 40. It has been like that.

The I / O module 48 includes an input capture register (ICR shown in the figure) for capturing a preset detection signal at a desired timing from among the detection signals from the various sensors, and a control target. Output timing of control signals to various actuators (for example,
An output compare register (OCR shown in the figure) for controlling the ignition timing (output timing of an ignition signal to be output to the igniter 16 via the output driver circuit 34 for ignition timing control) is also provided.

Each of these registers (ICR, OCR)
Stores time information indicating a timing of capturing a detection signal or an output timing of a control signal, which is set by arithmetic processing on the CPU 42 side, and stores the stored time information as a current time counted by a free-run counter 58 described later. When the count value coincides with the count value T0, the detection signal is fetched or the control signal is output.

The microcomputer 40 has a constant frequency F using the externally mounted quartz oscillator 38 as an oscillation source.
Reference clock generation circuit 50 for generating a reference clock of 0
And a frequency dividing circuit 52 that divides a reference clock from the reference clock generating circuit to generate a system clock (frequency: F1) that is an operation clock of the microcomputer 40, and that is generated by the frequency dividing circuit 52. A frequency dividing circuit 56 for generating a clock for clocking by dividing the system clock generated, and a free counter for generating a count value T0 representing the current time by counting the clock for clocking generated by the frequency dividing circuit 56. Run counter 5
8 are provided.

The system clock generated by the frequency dividing circuit 52 and the count value T0 by the free-run counter 58 are stored in the CPU 42 and the I / O module 4 respectively.
8 is input. Furthermore, the microcomputer 40
Is provided with a register “X” 60 for storing the frequency division value of the frequency dividing circuit 52 for generating the system clock, and the frequency dividing circuit 52 divides the value stored in the register “X” 60 As a value, the reference clock is frequency-divided.

The value stored in the register "X" 60 is also taken into the frequency dividing circuit 56, and the frequency dividing circuit 56 divides the frequency dividing value n stored in the timer prescaler register 54 based on the value. Correct and divide the system clock. That is, in the timer prescaler register 54, the frequency dividing value n for the frequency dividing circuit 56 to divide the system clock and generate the clock for clocking is stored. A dividing circuit for dividing the frequency dividing value n stored in the timer prescaler register 54 by the frequency dividing value x of the reference clock stored in the register "X" 60, and dividing the frequency obtained by the dividing circuit. "N /
By dividing the system clock by “x”, even if the value of the register “X” 60 changes and the frequency F1 (in other words, cycle) of the system clock changes, the frequency is output from the frequency dividing circuit 56. The frequency F2 (in other words, the period) of the clock for clocking is always the reference clock F0.
Is configured so as to have a constant frequency (F0 / n) corresponding to.

As described above, in the ECU 30 of the present embodiment,
When the frequency F1 of the system clock is equal to the value of the register “X” 60
Is determined by the value of the register “X” 6
A value corresponding to the engine speed is set to 0 according to the result of the arithmetic processing executed on the CPU 42 side.

Next, a description will be given, with reference to the flowchart shown in FIG. 3, of an arithmetic process executed by the CPU 42 to set the value of the register "X" 60 in accordance with the engine speed. As shown in FIG. 3, in this process, first, in S100 (S represents a step), the rotation angle sensor 2
5, the current engine speed NE obtained based on the detection signal (rotation angle signal) is fetched. At S110, whether the current engine speed NE is larger than a preset threshold value Nx is determined. The engine speed N
If E is larger than the threshold value Nx, a preset X1 is set as the frequency division value x of the reference clock in the frequency dividing circuit 52 for generating the system clock, and this is stored in the register "X" 60. Conversely, when the engine speed NE is equal to or smaller than the threshold value Nx, X2 larger than the above X1 is set as the frequency division value x of the reference clock in the frequency dividing circuit 52 for generating the system clock. This is stored in the register “X” 60, for example.

Here, "X1" is, as shown in FIG.
When the engine speed NE is higher than the threshold value Nx (that is, at the time of high engine speed), the fractional value in the frequency dividing circuit 52 is set to a value smaller than at the time of low engine speed, and the frequency F1 of the system clock is set to the low engine speed. The frequency "f
The value "X2" is set by the frequency dividing circuit 52 when the engine speed NE is equal to or lower than the threshold value Nx (that is, at the time of low engine speed), as shown in FIG. Is set to a value larger than that at the time of high rotation, and the frequency F1 of the system clock is set to a frequency "f12" lower than that at the time of high engine rotation.

Therefore, according to the internal combustion engine control apparatus of the present embodiment, the frequency F1 of the system clock (operation clock) of the microcomputer 40 used for engine control.
Is switched between when the engine 1 is running at low speed and when it is running at high speed. At low speed, the engine 1 is set to a lower value than when it is running at high speed.

For this reason, according to the internal combustion engine control apparatus of the present embodiment, the microcomputer 1
When the engine does not need to execute the arithmetic processing synchronized with the rotation of the engine at high speed, the system clock frequency F1
, The heat generation in the microcomputer 40 and the power supply circuit 36 that supplies power to the microcomputer 40 can be suppressed.

At the time of high engine rotation, which requires high-speed execution of arithmetic processing synchronized with the rotation of the engine 1,
By increasing the frequency F1 of the system clock,
It is possible to prevent the arithmetic processing in the microcomputer 40 from being delayed with respect to the engine rotation.

That is, according to the internal combustion engine control apparatus of the present embodiment, the processing speed of the microcomputer 40 is reduced within a range that does not affect the arithmetic processing synchronized with the engine rotation executed by the microcomputer 40. By lowering the temperature, heat generation in the microcomputer 40 and the power supply circuit 36 can be suppressed. Therefore, according to the present embodiment, it is possible to prevent the microcomputer 40 and its peripheral circuits from malfunctioning due to the heat generated by the microcomputer 40 and the power supply circuit 36, and to reduce the power consumption in the ECU 30.

As described above, according to the internal combustion engine control device of the present embodiment, the system clock of the system clock is not affected within the range that does not affect the arithmetic processing executed by the microcomputer 40 in synchronization with the engine rotation. Since the frequency F1 can be set low, high-frequency noise generated in the ECU 30 can be reduced. Therefore, according to the present embodiment,
The probability that the microcomputer 40 and its peripheral circuits malfunction due to the high-frequency noise can be sufficiently reduced.

In the internal combustion engine control apparatus according to the present embodiment, a free-running counter 58 for clocking is provided in the microcomputer 40, and the I / O module 48
On the side, the input timing of the detection signal and the output timing of the control signal are determined based on the count value T0 of the free-run counter 58, but the clock for clock input to the free-run counter 58 is as described above. The operation of the frequency dividing circuit 56 is set so as to always have a constant period. Therefore, even if the frequency F1 of the system clock is changed, the count value T0 of the free-run counter 58 always changes in accordance with a constant time. Will be updated.

As a result, according to the internal combustion engine control apparatus of the present embodiment, by changing the frequency F1 of the system clock, it is possible to set the timing for capturing the detection signal (time) and the timing for outputting the control signal (time) as desired. There is no deviation from the time, and the input and output of signals can be performed normally.

As described above, according to the present embodiment, it is possible to provide an extremely reliable internal combustion engine control device. In this embodiment, the frequency dividing circuit 52 provided in the microcomputer 40 corresponds to the operation clock generating means according to claim 2, and stores the frequency dividing value x of the frequency dividing circuit 52 in the register "X" 60. CPU
The arithmetic operation 42 (the arithmetic processing shown in FIG. 3) corresponds to the frequency dividing value setting means according to the second aspect, and these components realize the operation clock setting means according to the present invention (the first aspect). Further, the frequency dividing circuit 56 provided in the microcomputer 40 corresponds to the clock generating means of the third aspect, and the free-run counter 58 corresponds to the counting means of the third aspect.

As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various embodiments can be adopted. For example, in the above embodiment, the system clock frequency F1 is switched between two stages of "f11" or "f12" depending on whether or not the engine speed NE exceeds the threshold value Nx.
The number of switching stages of the frequency F1 of the system clock based on the engine speed NE may be set to three or more. In this way, it is possible to switch the frequency F1 of the system clock so that the amount of heat generation and high-frequency noise can be reduced more favorably.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a configuration of an entire internal combustion engine control device according to an embodiment.

FIG. 2 is a block diagram illustrating a configuration of an electronic control circuit (ECU) according to the embodiment.

FIG. 3 is a flowchart showing a calculation process executed by a CPU for setting a system clock (operation clock) of the microcomputer.

FIG. 4 is an explanatory diagram showing a change in the frequency of a system clock that is switched according to the engine speed as a result of the calculation processing in FIG. 3;

FIG. 5 is an explanatory diagram showing a relationship between an operation clock frequency of a microcomputer, a heat generation amount, and high-frequency noise.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine, 25 ... Rotation angle sensor, 30 ... ECU (Electronic control circuit), 32 ... Waveform shaping circuit, 34 ... Output driver circuit, 36 ... Power supply circuit, 40 ... Microcomputer, 42 ... CPU, 44 ... ROM, 46 … RAM, 48
... I / O module, 50 ... Reference clock generation circuit, 5
2: frequency divider circuit, 54: timer prescaler register, 5
6: frequency dividing circuit, 58: free-run counter, 60: register "X".

Claims (3)

[Claims] 1. An operating state detecting means for detecting various operating states of an internal combustion engine including a rotational speed, and realized by a processing operation of a microcomputer, and the internal combustion engine is operated in accordance with the operating state detected by the operating state detecting means. A control amount calculating means for calculating the control amount of the internal combustion engine based on the control amount calculated by the control amount calculating means. An internal combustion engine control device provided with an operation clock setting means for setting an operation clock frequency of the microcomputer so that the operation clock frequency becomes lower as the rotation speed becomes lower according to the rotation speed of the internal combustion engine. . 2. The operation clock setting means for generating the operation clock by dividing the frequency of a reference clock output from the reference clock generation means at a constant cycle; 2. The internal combustion engine control device according to claim 1, further comprising: a frequency division value setting unit that sets a frequency division value of the reference clock such that the frequency division value increases as the rotation speed of the internal combustion engine decreases. 3. 3. The microcomputer according to claim 1, wherein the microcomputer generates a clock for timekeeping by dividing the operation clock, and counts the clock for clocking generated by the clock generating means for clocking. Counting means for clocking the current time according to, wherein the clocking clock generating means is such that the clocking clock always has a constant cycle, according to a frequency division value set by the frequency dividing value setting means, The internal combustion engine control device according to claim 2, wherein a frequency division value at the time of dividing the operation clock is corrected.