JPH0228701B2 - ENJINNOAIDORUKAITENSUSEIGYOSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine idle speed control device.

(Prior art) When controlling the idle speed of an engine, a control valve is installed in a passage that bypasses the throttle valve in the intake passage, and a control valve is installed in a passage that bypasses the throttle valve in the intake passage. Generally, a method is adopted in which the amount of bypass air is controlled by feedback controlling the control valve.

Therefore, when the engine is cold, it is necessary to increase the amount of bypass air to ensure combustion stability, but if the amount of bypass air is covered only by the control valve mentioned above, it is necessary to increase the area of the bypass passage. In this case, there is a problem that the control accuracy of the intake air amount after warm-up becomes low. On the other hand, it is known that an air valve that controls the amount of bypass air in response to temperature is provided separately from the above-mentioned control valve, and the amount of bypass air is reduced as the engine cooling water temperature increases (for example, (Refer to Utility Model Application Publication No. 54-25914). That is, in this system, the idle air intake amount is roughly determined by the air valve according to the operating state of the engine, and the idle air intake amount is controlled with high precision by the control valve.

(Problems to be Solved by the Invention) The present invention is intended to solve the following problems that occur in the method of controlling the idle intake air amount by using the above-mentioned air valve and control valve in combination.

In other words, the upper and lower limits of the feedback control amount of the control valve are predetermined so that even if there is a failure in the control system, idling operation will not become impossible due to too much or too little amount of bypass air, and as shown in FIG. The lower limit value Q _MIN based on the air amount Q _B when no feedback control is performed is constant as shown by the broken line. And, since the air valve opening degree depends on the engine temperature, the amount of bypass air Q _T by both the control valve and the air valve when feedback control is not performed is as follows.
As shown by the one-dot chain line, the higher the engine temperature T, the smaller the amount.

However, since the above-mentioned air valves have a delay in response to changes in engine temperature, during the engine warm-up process, the amount of bypass air by both the above-mentioned valves is reduced corresponding to the elapsed time t from the time of cold start.
Qt has a characteristic that is shifted to the right by the response delay l with respect to the temperature correspondence line Q _T (in this warm-up process, the engine temperature T approximately corresponds to the elapsed time t).
In other words, the difference ΔQ between the bypass air amount Qt and the idle intake air amount Q at which the target idle rotation speed is obtained becomes large on the engine low temperature side. Therefore, even if feedback control is applied to the control valve, the lower limit value Q _MIN of the control amount is constant, so the amount of bypass air by both valves is
As shown by the two-dot chain line, Q _FB may not fall to the target idle intake air amount Q at low temperatures. In other words, the feedback control amount of the control valve is fixed at the lower limit value, and no substantial feedback control is performed, and the target idle rotation speed cannot be obtained while the intake air amount remains large.

On the other hand, it is conceivable to set the lower limit value of the above feedback control amount to a low value in advance, but when the bypass air amount reduction command is constantly issued due to a failure in the control system, the bypass air amount is insufficient. There is a risk that the engine speed may become excessive and the engine may become unable to idle. It is also conceivable to set the amount of bypass air by the air valve to a low value, but if there is a failure in the control system, the problem arises that it is difficult to start the engine due to the lack of amount of bypass air.

(Means for Solving the Problems) The present invention provides an air valve that increases the amount of bypass air flowing through a passage that bypasses a throttle valve in an intake passage of an engine as the engine temperature decreases, as a means for solving the above problems. A control valve that changes the amount of bypass air under feedback control so that the engine speed approaches the target idle speed, and a feedback control amount that controls the control valve in response to the output of a sensor that detects engine temperature. An object of the present invention is to provide an engine idle rotation speed control device that is provided with a control means that sets the lower limit of 1 to a lower value as the engine temperature becomes lower.

(Function) When the engine temperature is low, the lower limit value of the feedback control amount of the control valve is set to a low value, so the correction width of the bypass air amount by the control valve becomes wider on the lower limit side. In other words,
The amount of bypass air can be made smaller than when the engine temperature is high. Therefore, even if the amount of bypass air generated by the air valve becomes large due to a delay in the response of the air valve during the warm-up process of the engine, it is possible to control the amount of bypass air by the control valve to a smaller amount than when the temperature is normal. This makes it possible to reduce the overall amount of bypass air to the target idle intake amount.

On the other hand, even if a command to reduce the amount of bypass air is constantly given to the control valve due to a failure in the control system, the lower limit value of the feedback control amount is low only on the low temperature side where the air valve opening is large. , the problem of not being able to idle can be avoided.

(Effects of the Invention) Therefore, according to the present invention, it is possible to ensure idling operation in the event of a failure in the control valve control system, and to reliably perform feedback control of the idling speed during the warm-up process (low temperature) of the engine. In other words, it becomes possible to control the amount of bypass air so that the target idle rotation speed is obtained.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

In the engine idle speed control device shown in FIG. 1, 1 is the engine body, 2 is the piston 3
The intake passage leading to the upper combustion chamber 4 is also an exhaust passage. Surge tank 6 in intake passage 2
A throttle valve 7 is provided upstream of the throttle valve 7, and first and second bypass passages 8 and 9 are provided which bypass the throttle valve 7 and connect its upstream and downstream sides.

The first bypass passage 8 is provided with a wax-type air valve 10 that is sensitive to the engine temperature, that is, in this example, the engine cooling water temperature, and increases the opening area of the bypass passage 8 as the cooling water temperature decreases. It is provided. On the other hand, the second bypass passage 9 is provided with a duty solenoid type control valve 11 which is subjected to feedback control so that the engine speed approaches the idle speed. The engine body 1 is provided with a water temperature sensor 12 that detects the temperature of the cooling water, and a rotation sensor 13 that detects the engine speed from the rotation of the crank pulley. sensor 1
Controller (control means) 15 based on the output of 3.
The operation is now controlled by

That is, as shown in FIG. 2, the controller 15 includes a zone determination section 16, a target rotation speed setting section 17,
It includes a feedback control amount calculation section 18, a feedback control amount lower limit value setting section 19, a feedback control amount determination section 20, and an output section 21.

The specific content of the control by the controller 15 is shown in a flowchart in FIG.
6, it is first determined whether or not the engine is in the starting zone based on the presence or absence of an engine starting signal. If the engine is in the starting zone, the control valve 11 receives a duty pulse signal corresponding to the amount of bypass air necessary for starting the engine. It is output from the output section 21 (steps S ₁ and S ₂ ). If not in the starting zone,
Depending on whether or not a predetermined time has elapsed after startup,
It is determined whether or not it is in the post-start zone, and if it is in the post-start zone, a duty pulse signal corresponding to the amount of bypass air necessary to ensure combustion stability of the engine is output to the control valve 11 (step S). ₃ , _S4 ). If it is not in the initial set zone after starting, it is determined whether or not it is in the initial set zone based on the presence or absence of the initial set signal, and if it is in the initial set zone, a reference duty pulse signal is output to the control valve 11, and feedback control is performed. (steps _S5 , _S6 ).
In other words, this initial set zone is used to manually set the idle speed during engine maintenance. If it is not in the initial set zone, it is determined whether or not it is in the idle speed control cut zone depending on whether the engine speed is above a predetermined value and whether the clutch and gear are in the on state.If it is in this cut zone,
Feedback control of the control valve 11 is not performed, and if it is not in this cut zone, it is assumed that it is in the feedback zone, that is, the idle zone, and the idle speed is controlled (steps _S7 to
_S9 ).

That is, in the target rotation speed setting section 17, the value T of the water temperature sensor 12 is read, and the value of the target rotation speed (target idle rotation speed) NO is read from the T-NO table shown in FIG. _S10 , _S11 ). Next, the feedback control amount calculation unit 18 compares the actual rotation speed (actual engine rotation speed) Ne read from the rotation sensor 13 with the target rotation speed NO, and if NO>Ne,
Add the absolute value of the difference |NO−Ne|, and NO≦Qe
If so, the feedback control amount GFB'(I) is obtained by subtracting |NO-Ne| (steps _S12 to _S14 ).
Then, in the lower limit value setting section 19, the lower limit value of the feedback control amount is determined from the T-GFB _MIN characteristic table shown in FIG. 5 based on the value T of the water temperature sensor 12.
Read GFB _MIN (Step ₁₅ ). This lower limit
GFB _MIN is set to a lower value as the cooling water temperature T becomes lower. Then, in the feedback control amount determining section 20, the calculated
GTB'(I) and upper limit of feedback control amount
GFB _MAX (constant) as well as the lower limit set above
By comparing with GFB _MIN , GFB _MAX ＞GFB′()＞
If GFB _MIN , then set GFB′() as the feedback control amount GFB(), if GFB′()≧GFB _MAX , set GFB _MAX , and if GFB′()≦GFB _MIN , set GFB _MIN as the feedback control amount. GFB
() (steps _S16 to _S20 ).
Then, the output unit 21 calculates the duty D() corresponding to the feedback control amount GFB() determined above, and outputs the duty D().
The pulse signal ( ) is output to the control valve 11 (step S ₂₁ ).

Therefore, in the case of the above idle speed control device,
By setting the lower limit value GFB _MIN of the feedback control amount according to the cooling water temperature T, the control width of the bypass air amount Q by the control valve 11 decreases as the temperature T decreases, as shown in FIG. It becomes larger to _MIN . As a result, both valves 10 and 11 can be operated without feedback control due to the response delay of the air valve 10.
Even if the amount of bypass air Qt increases on the low temperature side of the engine, feedback control can reduce the amount of bypass air _Qt caused by both valves 10 and 11 until it matches the idle intake air amount Q over the entire temperature range.

On the other hand, even if a bypass air amount reduction command is constantly output due to a failure in the control system of the control valve 11, the lower limit value of the feedback control amount is set low because the air valve 11
Since the opening degree is large and the temperature is low, the problem of insufficient amount of bypass air does not occur.

Although the air valve in the above embodiment is of a wax type, it may also be of a type that controls the amount of bypass air using a bimetal that deforms with changes in engine temperature.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall configuration diagram of an engine idle speed control device, and FIG.
The figure is a block diagram of the control system, Figure 3 is a control flow diagram, Figure 4 is a water temperature table diagram of the target rotation speed, and Figure 5 is a diagram of the water temperature table for the target rotation speed.
The figure is a water temperature table diagram of the lower limit value of the feedback control amount, and FIG. 6 is a characteristic diagram showing the relationship between the amount of bypass air and the temperature (time). 1...Engine body, 2...Intake passage, 7...
Throttle valve, 8, 9... Bypass passage, 10...
...Air valve, 11...Control valve, 1
2...Water temperature sensor, 13...Rotation sensor, 15...
...Controller (control means).

Claims (1)

[Claims] 1. An air valve that increases the amount of bypass air flowing through a passage that bypasses the throttle valve of the engine as the engine temperature decreases, and a control valve that changes the amount of bypass air under feedback control so that the engine speed approaches the target idle speed. The engine is equipped with a temperature sensor that detects the engine temperature, and a control means that receives the output of the temperature sensor and sets the lower limit value of the feedback control amount that controls the control valve to a lower value as the engine temperature decreases. An engine idle speed control device characterized by: