JPS62189345A - Idling speed control method for internal combustion engine - Google Patents

Abstract

PURPOSE:To make it possible to smoothly shift an engine speed to an idling speed, by calculating a control valve command value at deceleration according to a deceleration rate, an engaged condition of an external load, and an engine cooling water temperature. CONSTITUTION:When an engine speed becomes lower than a set value slightly higher than an idling speed, an electronic control device 40 calculates a control quantity Isa for a solenoid 16 of a control valve 30 according to a deceleration rate of the engine speed, an engaged condition of an external load associated with an engine, and a cooling water temperature to be detected by an engine cooling water temperature sensor 21. When the control quantity Isa is greater than the sum of a learning value Ixref as a control quantity under a stable idling condition and a warm-up signal Itw, a command value Icmd for the control valve 30 is calculated by using the value Isa instead of the sum obtained above or a feedback control term Ifb. Accordingly, the command value Icmd may be increased according to the deceleration rate, and the engine speed is prevented from greatly decreasing from the idling speed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for controlling the idle speed of an internal combustion engine, and in particular, when the engine speed suddenly drops from a high speed, The throttle control valve is installed in a bypass passage that communicates the upstream and downstream of the throttle valve installed in the engine. The present invention relates to a method for controlling the idle speed of an internal combustion engine so as to shift to a target idle speed of a mode.

(Prior Art) Conventionally, when the throttle valve installed in the intake passage of an internal combustion engine is kept in a nearly closed state and the operation is continued, that is, during so-called idling operation or at low load, the upstream and downstream of the throttle valve are connected. A control valve provided in a communicating bypass passage controls the intake air amount of the internal combustion engine, thereby controlling the idle speed of the internal combustion engine.

By the way, it is generally well known that even in electronically controlled fuel injection internal combustion engines, when the amount of intake air increases, the amount of fuel injected also increases, and as a result, the air-fuel mixture becomes heavier. .

By the way, the opening degree of this control valve is controlled in a closed loop when the throttle valve is almost closed and the engine speed is in a predetermined idle speed range.

That is, the excitation current supplied to the solenoid that proportionally controls the opening degree of the control valve is basically determined based on the solenoid current command value Icmd obtained by the following first equation.

I cmcl = I fb(n) - (Equation 1) However, Ifb(n)... target idle rotation speed N ref,
Based on the deviation from the actual engine speed Ne, the proportional (
PID feedback control term for performing integral (1 term), differential (D term) control. n is incremented by 1 each time a TDC pulse is output.

Further, the opening degree of the control valve is controlled in an open loop when the throttle valve is in an open state or when the engine speed is not in a predetermined idle speed range.

(Problems to be Solved by the Invention) The above-described conventional techniques had the following problems.

For example, after controlling the throttle valve in the open direction to make the engine speed high, the throttle valve is almost closed, and the internal combustion engine is placed in a no-load state (neutral range or clutch depressed state). Then, the engine speed rapidly decreases.

When the engine speed enters the expected idle speed range, as described above, the opening control of the control valve changes from the open loop control state to the feedback control state so that the engine speed approaches the target idle speed. to move to.

However, even if the control valve opening degree is set to a predetermined angle, there is a slight response delay until the amount of air-fuel mixture corresponding to the angle is actually supplied into the cylinder, and under no-load conditions as described above, , because the decreasing trend of the engine speed is very steep, a situation occurs in which the engine speed temporarily drops below the target idle speed, and then stabilizes at the target idle speed due to feedback control. Ta.

In addition, in order to obtain high output, if a chamber is installed between the throttle valve and the cylinder of the engine, the response delay described above will become large, so the drop in engine speed will occur. The tendency is to become stronger.

The present invention has been made to solve the above-mentioned problems.

(Means and Effects for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a method for determining the deceleration, the connection state of an external load to the engine, and the engine cooling water temperature when the engine speed is decelerated. The control valve command value is calculated according to the engine speed, and the control valve command value is increased as the engine speed decreases more rapidly, so that the engine speed smoothly transitions to the idle speed. There are characteristics.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 3 is a schematic diagram of an idle speed control device for an internal combustion engine to which the method of the present invention is applied. FIG. 3 shows an example of an idle speed control TL device for an internal combustion engine, which is applied to an internal combustion engine in which a chamber 39 is provided between a throttle valve 32 and an injection nozzle 34 in order to obtain high output. ing.

In the figure, the intake air amount in the intake manifold 33 during idling operation when the throttle valve 32 is almost fully open is determined by the control valve 30 provided in the bypass passage 31 that communicates the upstream and downstream of the throttle valve 32. 1tilJ m.

The opening degree of this control valve 30 is determined according to the current flowing through the solenoid 16.

The amount of fuel injected from the injection nozzle 34 is determined according to the amount of intake air in the intake manifold 33 by known means. The piston 38 within the cylinder 35 repeatedly reciprocates to apply rotational force to the crankshaft 36.

Further, the TDC sensor 5 generates a pulse when the piston of each cylinder reaches 90 degrees before the top dead center. In other words, the TDC sensor 5 outputs the same number of pulses as the number of cylinders (hereinafter referred to as TDC pulses) every time the crankshaft 36 rotates twice, and supplies them to the electronic control device 40.

The throttle opening sensor 4 detects the throttle opening and supplies a throttle opening signal corresponding to this to the electronic control device 40 as a digital signal.

Engine coolant temperature detection sensor 21 detects engine coolant temperature and supplies it to electronic control device 40 .

The air conditioner compressor 23 is directly connected to the crankshaft 36 via the electromagnetic clutch 22. The air conditioner compressor 23 controls the temperature of the air outlet,
Alternatively, a sensor (not shown) for detecting the temperature inside the vehicle is provided, and the sensor supplies the temperature signal to the electronic control device 40.

The electromagnetic clutch 22 is controlled on/off by an electronic control device 40 according to the temperature.

FIG. 4 is a block diagram showing an example of the internal configuration of the electronic TiIl device 40 of FIG. 3. As shown in FIG. In the figure, the third
The same reference numerals as in the figures refer to the same or equivalent items.

The electronic control device 40 includes a microcomputer 53 consisting of a central processing unit (CPU) 50, a storage device (memory) 51, and an input/output processing circuit (interface) 52, and a microcomputer 53 that operates according to a command from the microcomputer 53 (solenoid current command value Jcmd). The control valve drive circuit 54 includes a control valve drive circuit 54 that controls the current flowing through the solenoid 16, and an electromagnetic clutch drive circuit 25.

The electromagnetic clutch drive circuit 25 outputs an on/off signal for the electromagnetic clutch 22 in accordance with the temperature detected by a sensor provided in the air conditioner compressor 23.

The control valve drive circuit 54 outputs a control signal for controlling the current flowing through the solenoid 16 according to the J cmd. As a result, the opening degree of the control valve 30 (FIG. 2) is
cmd, and by extension, the idle rotation speed is also controlled according to 1 cmd.

Next, the control method of the present invention will be explained.

FIG. 1 is a flowchart illustrating the operation of an embodiment of the present invention. The operation of the flowchart in the same figure is
Starts with a pulse interrupt.

In FIG. 1, in step S1, it is determined whether the engine is being started. The determination that the engine is not starting can be made, for example, based on the conditions that the starter switch is off and the engine speed has reached the idle target speed of about 17'2.

Next, in step S2, it is determined whether or not the automatic transmission of the vehicle is in the D range (drive range). If the automatic transmission is in the D range (drive range), the program proceeds to step S8; Move to.

Note that if the vehicle is not equipped with an automatic transmission, the process directly proceeds from step S1 to step S3.

In step S8, it is determined whether the vehicle speed 1 switch is turned on, in other words, whether the vehicle speed of the vehicle exceeds a certain speed (for example, 15 km/h). If the vehicle speed v1 switch is turned on, the program moves to step S9, and if it is not turned on, the program moves to step S3.

In step S3, the reciprocal of the engine speed Ne (
In other words, the output interval time (Me) of the TDC pulses output from the TDC sensor 5 (FIG. 3) is compared with the reciprocal Ma of the idle determination rotation speed Na stored in the memory in the electronic control unit 40. be done. The idle determination rotation speed Na is a value set to be slightly larger than the idle target rotation speed N ref.

If Me is larger than Ma - that is, if the engine speed Ne is lower than the idle determination speed Na,
The process moves to step S4. If Me is equal to or smaller than Ma, the program moves to step S9.

In step S4, the opening degree θt of the throttle valve 32
It is determined whether h is smaller than an angle θ1dlh, which is defined as the throttle valve being substantially closed. If θth is smaller than θ1dlh, that is, if the throttle valve 32 is substantially closed, the program moves to step S5, and if it is not fully open, the program moves to step S9.

Steps S2 to S4 and S8 are for determining whether the engine is in an idling state after completion of starting, and whether the throttle valve is opened and the engine is starting, accelerating, cruising, or decelerating, or continues in an idling state. Step on the steps.

When it is determined in steps S2 to S4 and S8 that the engine is in the idle operating state, in step S5 the electronic control unit 40 (FIG. 2) enters the closed loop mode, and when calculating cmd, which will be described later. Ifb(n), which is the basic value of , is calculated. The operation in step S5 will be described later with reference to FIG.

In one embodiment of the present invention, the current command value cmd of the linear solenoid 16 is set as follows every time a TDC pulse is output, regardless of whether the electronic control unit 40 is in open loop mode or closed loop mode. It is calculated using the following formula.

Icmd = (Ifb(n) +Ie +Ips
at 10Iac)Xi(pad...(
(2) In the first equation, e is an electrical load correction value determined depending on the size of the electrical load connected to the battery, and II) S is whether the power steering switch is turned on or not. Hat is the D range correction value determined depending on whether the automatic transmission is in the D range, IaC
is an air conditioner correction value determined depending on whether or not the air conditioner is turned on, and K pad is an atmospheric pressure correction value determined depending on the atmospheric pressure. Further, the code n is incremented by 1 each time a TDC pulse is output.

As mentioned above, in the closed loop mode, Ifb(n) in the first equation is calculated in step S5, and in the oven loop mode, it is defined in step S10.

Next, one method of calculating I fb(n) in the closed loop mode shown in step S5 will be explained in the sixth section.
This will be explained using the flowchart shown in the figure.

First, in step 321, the output interval time Me(n) of TDC pulses output from the TDC sensor 5, that is, the reciprocal of the engine rotation speed is read.

In step 322, the read Me(n) and
Reciprocal of target rotation speed N ref or equivalent amount M
A deviation ΔMef from ref is calculated.

In step S23, the Me(n) and the previous measured value Me in the same cylinder as the Me(n) are
(If the engine is a 6-cylinder engine, Me(
n-6)) - that is, the period change rate ΔMe is calculated.

In step S24, the ΔMe and ΔMef
, and preset control gains (integral term control gain Kint, proportional term control gain Kl) m, and differential term control gain Kdm>, the integral term Ii, the proportional term ■p1, and the differential term Id are calculated as shown in the figure. It is calculated according to the formula shown inside.

In step S25, 1 ai (n) is Ia
It is defined as the value obtained by adding the integral term Ii to i(n-1).

Then, in step S26, Ip and ■d calculated in step 324 are added to Jai(n) calculated in step S25, and the result is defined as Ifb(n).

Returning to FIG. 1 again, in step S6, a warm-up signal itw is searched in accordance with the engine coolant temperature at that time. Note that the warm-up signal (tw will be described later with respect to step S9). This search is not performed if the engine has already been warmed up.

Next, in step S7, an erasure value I xref (n) defined, for example, by the third equation described later is calculated.

IXref(n) = Iai(n) XCCrr /
m+ I xref(n-1) x (m -Ccrr
)/m...(Third Formula) In the above formula, m and Cxrr are arbitrarily set positive integers, and are set so that m>CCrr.

Note that the calculation of the cancellation value in step S7 is performed when no load is connected to the internal combustion engine, or when the connected load is extremely light, and after warm-up is completed. The learned value is a control signal for the solenoid 16 when no load is connected to the internal combustion engine, or when the connected load is extremely light and the rotation of the engine is stable.

When the process moves from step S3, S4 or S8 to step S9, the electronic control device 40
The open loop mode is entered, and the learning value Hxrer calculated in the closed loop mode, that is, step S7
If the engine is not yet warmed up, the warm-up signal (correction value) Hw is searched and read out according to the learned value IXref calculated in , and the engine coolant temperature TW. The warm-up signal Hw is set to the learned value Ix before the warm-up is completed.
This is a value added to ref, and is a numerical value for correcting the learned value JXref according to the engine coolant temperature.

Then, in step S10, the sum of the learning value IXref and the warm-up signal Itw is defined as l fb(n). After that, the process moves to step 311.

Details of the processing contents of step 811 are shown in FIG.

In step S31 of FIG. 2, the TDC pulse output interval time Me measured the last time this processing step was performed
However, it is determined whether or not the currently measured Me exceeds Ma when the reciprocal number Ma of the idle determination rotation speed Na is below. In other words, the engine speed Ne is the idle determination speed Na.
It is determined whether or not the value has fallen below .

If the engine rotation speed Ne is lower than the idle determination rotation speed Na, in step 332, the electromagnetic clutch 22 for the air conditioner is turned on/off and the engine coolant temperature TW is
The correction term K15a is searched accordingly.

The correction term K15a is a function of the engine coolant temperature TW, and also depends on whether the electromagnetic clutch 22 (FIG. 3) is in the off state (disengaged state of 11) or on state (engaged state).
As shown in the curves K15aO and )(isa'l in FIG. 5, respectively), two types of tables are set depending on whether

After the correction term 1<isa is searched, in step S33, the product of the detected correction term K15a and the amount of change ΔMe in the output interval time Me of the TDC pulse is calculated as Isa
is defined as The amount of change ΔMe is the output interval time Me of the TDC pulse detected in this previous processing step.
This is the difference between the output interval time Me of the TDC pulse detected in this processing step, and the deceleration of the engine rotation speed is determined.

Therefore, if the deceleration of the engine speed is large, the calculated value of ISa will also be large.

Next, in step S34, it is determined whether the ISa is larger than the fixed value 1sa1m.

Only when Isa is larger than the fixed value 1sa+m, Isa+m is set as ISa in step S35.

In step S31, the previous Me is less than or equal to Ma,
If it is not determined that Me is greater than or equal to Ma this time, that is, for example, for a bond for which lsa has been set in step 533i or step S35, step S
36, the previously calculated Hsa, i.e. l5a
The fixed value ΔIsa is subtracted from (n-1), and the current H
sa, ie, Isa(n), is defined.

Returning to FIG. 1 again, in step S12,
Isa calculated in step S1'l is the learned value l
It is determined whether or not the value is greater than the sum of xref and warm-up signal tw. If the engine has been warmed up, ISa is compared with the learned value 1xref.

If isa is larger than the sum of ■Xref and ItW, Ifb(n) is defined as Isa in step S13.

Then, in step S''14, Icmd is calculated from the second equation, and in step S15, cmrj is
The control valve solenoid 16 of the bypass passage 31 is controlled.

In step 312, Jsa is 1xrer and It
If the sum is smaller than the sum of w, the process proceeds to step S
Step S12 directly proceeds to step S14.

Now, in the explanation regarding FIG. 5, the table K15a, which is set according to the engine coolant temperature Tw and searched to calculate Isa, is used for two cases, one when the electromagnetic clutch 22 of the air conditioner is on and the other when it is off. Although the present invention is limited to only one type, the present invention is not limited to this, and many more types may be set depending on the state of the external load connected to the engine.

In addition, the Isa is calculated as soon as the engine speed Ne becomes lower than the scheduled rotation speed Na, and after that, the fixed value △1sa is reduced from isa every time a TDC pulse is generated. However, for example, once ■Sa is calculated, ISa@ is calculated every time a TDC pulse is output according to the deceleration state of the engine speed Ne until the deceleration of the engine speed Ne becomes gradual. You may also do this.

Roughly, the subtraction of the fixed value ΔIsa may be performed as time passes.

(Effects of the Invention) As is clear from the above description, according to the present invention, the following effects are achieved. That is, no matter what operating mode the electronic control unit of the engine is in, when the engine speed falls below the engine speed set to a value slightly higher than the idle speed, ICn1
Before controlling the control valve solenoid 16 in the bypass passage in step d, the control 1isa is calculated according to the deceleration of the engine speed, the connection state of the external load to the engine, and the engine coolant temperature, and the control amount ISa is is larger than the controlled amount during stable idling, that is, the sum of the learned value ■Xref and the warm-up signal Itw, Icmd is calculated by using Jsa instead of the sum of the learned value Since it is calculated, when the deceleration of the rotational speed of the engine is large, i cmd can be increased in accordance with the deceleration. As a result, the engine speed of the engine does not fall much below the idle speed, and the engine can smoothly transition from a deceleration state to an idling state.

[Brief explanation of drawings]

FIG. 1 is a flowchart explaining the operation of an embodiment of the present invention, FIG. 2 is a flowchart showing details of step S11 shown in FIG. 1, and FIG. 3 is an idle rotation to which the method of the present invention is applied. 4 is a block diagram showing an integrated example of the electronic control device in FIG. 3; FIG. 5 is a graph showing the relationship between the correction term K15a and the engine coolant temperature TV; The figure shows step S shown in FIG.
5 is a flowchart showing an example of the processing operation in step 5. 4... Throttle opening sensor, 5... TDC sensor, 16... Solenoid, 21... Engine coolant temperature detection sensor, 22... Electromagnetic clutch, 23... Air conditioner compressor, 30... ...Control valve, 31...
Bypass passage, 32...Throttle valve, 40...Electronic control device, 53...Microcomputer agent Patent attorney Michito Hiraki and 1 other person Figure 5 Engine cooling water temperature ~

Claims (5)

[Claims] (1) The internal combustion engine has a control valve provided in a bypass passage that communicates the upstream and downstream of the throttle valve of the internal combustion engine, and controls the opening degree of the control valve according to the control valve command value. In an internal combustion engine idle speed control method that controls the idle speed of the internal combustion engine by controlling the intake air amount of the engine, when the engine speed is decelerated at a speed higher than the target idle speed, Detecting a connection state of an external load to the internal combustion engine; detecting a cooling water temperature of the internal combustion engine; 1. A method for controlling an idle rotation speed of an internal combustion engine, characterized in that the control valve command value is calculated based on the control valve command value. (2) The initial value of the control valve command value to be calculated is calculated when the engine speed falls below a predetermined speed that is higher than the target idle speed. The method for controlling the idle speed of an internal combustion engine as described. (3) The control valve command value to be calculated is characterized in that after the initial value is calculated, it is calculated by subtracting a predetermined value from the initial value every time a TDC pulse is output. A method for controlling the idle speed of an internal combustion engine according to claim 1 or 2. (4) The control valve command value to be calculated is calculated by subtracting a predetermined value from the initial value as time passes after the initial value is calculated. A method for controlling the idle speed of an internal combustion engine according to item 1 or 2 of the range. (5) The control valve is controlled based on the calculated control valve command value when the calculated control valve command value is larger than the control valve command value during idling operation. A method for controlling the idle speed of an internal combustion engine according to any one of claims 1 to 4.