CN109339960B - Method and device for regulating idle speed of engine - Google Patents

Abstract

The invention provides aA method of regulating idle speed of an engine, comprising: the ECM sends an idle speed instruction to the engine to enable the engine to enter an idle speed state; ECM at standard idle speed N₀Regulating and controlling the idle speed N of the engine for the target speed; the ECM acquires the idle speed N of the engine, the exciting current i output by an exciting device at the idle speed N and the corresponding standard idle speed N₀Idle speed threshold value N_maxAnd corresponding to a standard idling speed N₀And an idle speed threshold N_maxExcitation current threshold value i_max(ii) a The ECM compares the obtained excitation current i with an excitation current threshold i_maxAccording to the obtained exciting current i and the exciting current threshold value i_maxThe magnitude relation of (a) adjusts the idle speed N of the engine. The invention also relates to a device for regulating and controlling the idle speed of the engine, which can achieve the purposes of low cost, high reliability and comfort through function development and program calibration under the condition of not changing the existing AMS hardware.

Description

Method and device for regulating idle speed of engine

technical field

The present invention relates to the field of vehicle engines, and in particular, to a method and a device for regulating the idle speed of an engine.

Background technique

The idle state refers to a working condition when the engine is idling. In fact, if the idle speed of the engine is too low, the car will turn off when it is temporarily stopped (such as stopping at a red light, turning the car, and decelerating). However, if the idle speed of the engine is too high, it will increase the fuel consumption, increase the working temperature of the engine, accelerate the wear of the engine, and there will be a large impact sound when shifting gears, which will cause great damage to the car.

With the increasing requirements of national policies on fuel consumption targets, some new technologies are emerging one after another, such as AMS (Alternator Management System, intelligent power generation management system), ISS (Intelligent Start/Stop, intelligent start-stop system), 48V BSG Wait. In order to save fuel and improve the driving comfort of customers, an intelligent power generation management system is added to the vehicle. As an important component of the intelligent power generation management system, the performance of its key component, the gear train, has also become critical.

In the prior art, the one-way pulley is assembled on the generator. When the generator rotates in the reverse direction, the pulley will be disengaged from the generator to prevent the generator from reversing during deceleration; The spring structure in the isolation isolator) can slowly increase the mass of the generator to the wheel train, so as to reduce the impact on the wheel train and improve the driving comfort.

Further, because the existing intelligent power generation function is only used in the case of rapid acceleration and rapid deceleration, and is not used in other working conditions, the application scope of the intelligent power generation function is limited. Especially when the three-cylinder engine is matched with the generator separation vibration isolator, when the engine is at low idle speed under idle speed conditions, due to the special structure of the generator separation vibration isolator, and the low idle speed angular vibration of the 3-cylinder engine is large (3-cylinder engine characteristics : The lower the standard idle speed of the engine, the greater the angular vibration), which will cause the low idle speed condition of the generator separation isolator and the excessive current output of the generator to occur at the same time, which not only makes the energy consumption too high, but also affects the The reliability of the generator isolation isolator has an impact, which in turn limits the use of the generator isolation isolator. However, if the generator separation isolator is removed, the driving comfort is affected. However, if the OAD (Overrun Alternator Decoupler, generator overrun isolator) pulley with higher reliability is used, the cost will increase. Obviously, none of the above solutions are ideal.

SUMMARY OF THE INVENTION

In view of this, it is necessary to provide a method and device for regulating the idle speed of an engine that can make the AID pulley work within a safe range to ensure both driving comfort and reliability of the AID pulley.

The invention provides a method for regulating the idle speed of an engine, comprising:

The ECM sends an idle command to the engine to make the engine enter the idle state;

The ECM controls the idle speed N of the engine with the standard idle speed N ₀ as the target speed;

The ECM obtains the idle speed N of the engine, the excitation current i output by the excitation device at the idle speed N, the idle speed threshold N _max corresponding to the standard idle speed N _{0 , and the excitation current threshold i corresponding to the standard idle speed N 0 and} the idle speed threshold N _{max max} ;

The ECM compares the acquired excitation current i and the excitation current threshold i _max , and adjusts the idle speed N of the engine according to the acquired excitation current i and the excitation current threshold i _max . Further, the corresponding relationship between the standard idle speed N ₀ and the idle speed threshold N _max and the output current threshold I _max of the generator and the excitation current threshold i _max is stored in the ECM, and the excitation current i is determined by reading the excitation current i and the excitation current. The magnitude relationship of the current threshold value i _max , obtain the magnitude relationship between the output current I of the generator and the output current threshold value I _max , and adjust the idle speed N of the engine, wherein, the standard idle speed N ₀ is obtained according to experiments when the comprehensive performance is optimal The idle speed, the idle speed threshold N _max is the maximum idle speed that can be endured according to the standard idle speed N ₀ and obtained according to the experiment.

Further, the standard idle speed N ₀ of the engine and the idle speed threshold N _max of the engine are stored in the ECM in advance; the ECM also stores a first output current threshold I _max1 corresponding to the standard idle speed N ₀ of the engine, the excitation The current threshold value i _max includes a first excitation current threshold value i _max1 corresponding to the first output current threshold value I _max1 , and the first excitation current threshold value i _max1 is stored in the ECM.

Further, if the excitation current i read by the ECM is less than the first excitation current threshold value i _max1 , the output current I of the generator is within the range of the first output current threshold value I _max1 , the ECM does not regulate the idle speed N of the engine, and the engine keeps the current The idle speed N remains unchanged.

Further, if the excitation current i read by the ECM is greater than or equal to the first excitation current threshold value i _max1 , and the output current I of the generator exceeds the range of the first output current threshold value I _max1 , the ECM sends a rotational speed increase command to the engine to increase the speed of the engine. The target speed is increased from the standard idle speed N ₀ to the idle speed threshold N _max .

Further, the ECM also stores a second output current threshold value I _max2 obtained through experiments and corresponding to the idle speed threshold value N _max , and the excitation current threshold value i _max further includes a second output current threshold value I _max2 corresponding to the The second excitation current threshold i _max2 is _obtained through experiments and stored in the ECM; if the output current I of the generator decreases, the excitation current i read by the ECM is less than or equal to the second excitation current threshold i _max2 , the ECM sends a rotational speed increase cancel command to the engine, and the idle rotational speed N of the engine decreases.

The present invention also provides a device for regulating the idle speed of an engine, comprising an engine, a generator assembly attached to the engine, and an ECM for regulating the engine, wherein the generator assembly is provided with a generator and a generator connected to the generator. Signal-connected excitation device, the excitation device can output the corresponding excitation current i according to the output current I of the generator; the ECM is connected to the engine through signal communication, and sends an idle speed command to the engine to regulate and control the engine. Read the idle speed N of the engine; the excitation device is connected to the ECM through signal communication, and outputs an excitation current i to the ECM; the ECM regulates the idle speed N of the engine with the standard idle speed N ₀ as the target speed, and According to the stored standard idle speed N ₀ and the idle speed threshold N _max corresponding to the standard idle speed N ₀ , obtain the excitation current threshold i _max corresponding to the standard idle speed N ₀ and the idle speed threshold N _max respectively, according to the read The magnitude of the relationship between the obtained excitation current i and the excitation current threshold i _max is compared to determine the magnitude of the output current I of the generator and the output current threshold I _max , and the idle speed N of the engine is adjusted.

Further, the excitation current threshold i _max includes a first excitation current threshold i _max1 corresponding to the standard idle speed N ₀ of the engine. If the excitation current i read by the ECM is less than the first excitation current threshold i _max1 , the The ECM does not regulate the idle speed N of the engine, and the engine keeps the current idle speed N unchanged.

Further, the excitation current threshold i _max includes a first excitation current threshold i _max1 corresponding to the standard idle speed N ₀ of the engine. If the excitation current i read by the ECM is greater than or equal to the first excitation current threshold i _max1 , The ECM sends a speed increase command to the engine to increase the target speed of the engine from the standard idle speed N ₀ to the idle speed threshold N _max .

Further, the excitation current threshold value i _max further includes a second excitation current threshold value i _max2 corresponding to the idle speed threshold value N _max . If the output current I of the generator decreases, the excitation current i read by the ECM is less than or equal to the For the second excitation current threshold i _max2 , the ECM sends a rotational speed increase cancel command to the engine, and the idle rotational speed N of the engine decreases.

For the specific content of the generator, the engine and other body components, reference may be made to the prior art, and details will not be repeated here.

To sum up, in the present invention, when the engine is idling, the ECM compares the excitation current and the threshold of the excitation current to determine that if the output current of the generator exceeds the tolerable range of the generator separation isolator, the standard idle speed of the engine is increased to reduce the output current. To avoid low idle speed, the large torsional vibration of the engine and the high consumption of the generator appear at the same time, reducing the double pressure on the generator separation isolator (especially for a 3-cylinder engine).

The above description is only an overview of the technical solutions of the present invention, in order to be able to understand the technical means of the present invention more clearly, it can be implemented according to the content of the description, and in order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand , the following specific preferred embodiments, and in conjunction with the accompanying drawings, are described in detail as follows.

Description of drawings

1 is a schematic structural diagram of a specific embodiment of a device for regulating the standard idle speed of an engine provided by the present invention;

Fig. 2 is the structural representation of the generator and generator separation vibration isolator installation of the generator assembly in Fig. 1;

FIG. 3 is a flow chart of a specific embodiment of a method for regulating the idle speed of an engine provided by the present invention.

Detailed ways

In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the present invention is described in detail below with reference to the accompanying drawings and preferred embodiments.

As shown in FIGS. 1 and 2 , the present invention provides a device for regulating the idle speed of an engine, which includes a generator assembly 10 attached to the engine and an ECM (Engine Control Module, Chinese: Engine Control Module) for regulating the engine.

In detail, the generator assembly 10 includes a generator 11 capable of outputting a current I; the generator assembly 10 is further provided with an excitation device connected to the generator 11 to directly transmit an excitation current signal to the ECM.

The standard idle speed N ₀ of the engine and the idle speed threshold N _max have a one-to-one correspondence with the output current threshold I _max of the generator 11 and the excitation current threshold i _max of the excitation device, and the excitation device can be based on the output current I of the generator. Output the corresponding excitation current i. In this embodiment, the output current threshold I _max of the generator 11 includes the first output current threshold I _max1 and the second output current threshold I _max2 , and the excitation current threshold i _max of the excitation device includes the first excitation current threshold i _max1 and the second excitation current threshold i _max2 . The standard idle speed N ₀ of the engine corresponds to the first output current threshold I _max1 of the generator 11 and the first excitation current threshold i _max1 of the excitation device, and the idle speed threshold N _max of the engine corresponds to the second output current threshold of the generator 11 I _max2 and the second excitation current threshold i _max2 of the excitation device.

In this embodiment, the excitation device is connected to the ECM through signal (current signal) communication. Specifically, the excitation device is connected to the ECM for bidirectional communication; the ECM can directly read the excitation current i output by the excitation device; conversely, the excitation device can also adjust the excitation current i according to the speed increase control signal (acceleration signal) transmitted by the ECM.

The engine and the ECM are communicated and connected through signals (command signals, current signals). Specifically, the engine and the ECM are connected in two-way communication, and the ECM (Engine Control Module, engine control module) can control the engine to enter an idle state by sending an idle command to the engine; it can also regulate the idle speed N of the engine by taking the standard idle speed N ₀ as the target speed. , adjust the idle speed N to the standard idle speed N ₀ , or adjust the idle speed N to the vicinity of the standard idle speed N ₀ , and at the same time, when the engine idle speed N is near the standard idle speed N ₀ , obtain the standard stored in the ECM and the engine The first output current threshold I _max1 and the idle speed threshold N _max of the generator 11 corresponding to the idle speed N ₀ , and the first excitation current threshold i _max1 corresponding to the first output current threshold I _max1 ; further, the ECM can also obtain a The second output current threshold value I _max2 of the generator corresponding to the idle speed threshold value N _max and the second excitation current threshold value i _max2 corresponding to the second output current threshold value I _max2 .

In the present invention, the ECM can also send an acceleration or cancel acceleration signal to the engine to regulate the idle speed of the engine according to the acquired excitation current i and the magnitude relationship between the first excitation current threshold i _max1 and the second excitation current threshold i _max2 stored in the ECM N.

In this embodiment, the generator 11 is provided with a generator separation vibration isolator 13, and the generator separation vibration isolator 13 is connected to the generator shaft through bolts; the device for regulating the idle speed of the engine further includes a belt 20 and a tensioner 30 , crankshaft 40 and air conditioner compressor 50, belt 20 bypasses the pulley of crankshaft 40, the pulley of air conditioner compressor 50, the generator separation isolator 13 of generator 11, and the pulley of tensioner 30 in turn to form power generation The wheel train of the engine 11 can improve the comfort of the vehicle, and the reliability of the wheel train is mainly judged according to the output current I of the generator 11 and the idle speed N of the engine.

In detail, in the present invention, the tensioner 30 is a holding device on the belt drive system, that is, the belt 20 can have a proper tension during the transmission process, so as to avoid the belt 20 from slipping or the occurrence of tooth skipping and tooth dislocation. Naturally, in other embodiments, the gear train of the generator 11 may also be a generator isolation vibration isolator (AID pulley) structure that does not include the tensioner 30. For details, reference may be made to the prior art, which is not limited here. .

For the specific content of the generator 11 , the engine and other vehicle body components, reference may be made to the prior art, and details will not be repeated here.

It can be understood that the main purpose of the present invention is: under the idle speed condition of the vehicle, if the idle speed of the engine (in the idle speed condition, the idle speed of the engine during normal operation is near the standard idle speed N ₀ ) is too low, it will cause The angular vibration of the vehicle is large, and the output current of the generator is too large, which can easily lead to the failure of the generator isolation isolator 13. Therefore, the ECM in the present invention needs to be able to control the engine according to the output current I of the generator. The size of the idle speed N (based on the standard idle speed N ₀ ) to avoid the situation of low idle speed and high current. However, since the ECM cannot directly read the output current I of the generator, it can directly read the magnitude of the excitation current i transmitted by the excitation device, and at a certain temperature and speed, the excitation current i and the output current I of the generator There is a one-to-one correspondence, when the idle speed and temperature are constant, the output current I of the generator increases with the increase of the excitation current i, and decreases with the decrease of the excitation current i. Therefore, in the present invention, the ECM _infers (obtains/obtains) the magnitude of the generator's The size of the output current I and the output current threshold I _max (mainly to determine whether the output current I is too large), according to the relationship between the output current I of the generator and the output current threshold I _max , the idle speed N of the engine is regulated, and the output of the generator is adjusted. The current I achieves the purpose of avoiding the simultaneous occurrence of high current and low idle speed.

Referring to Figure 3, the present invention also provides a method for regulating the idle speed of an engine, the method comprising:

The ECM sends an idle command to the engine to make the engine enter the idle state;

The ECM controls the idle speed N of the engine with the standard idle speed N ₀ as the target speed (adjusted to the standard idle speed N ₀ or adjusted to the vicinity of the standard idle speed N ₀ );

The ECM obtains the idle speed N of the engine, the excitation current i output by the excitation device corresponding to the idle speed N, the idle speed threshold N _max corresponding to the standard idle speed N _{0 , and the excitation corresponding to the standard idle speed N 0 and} the idle speed threshold N _max current threshold i _max ;

The ECM compares the magnitude relationship between the obtained excitation current i and the excitation current threshold i _max , and adjusts the idle speed N of the engine according to the obtained magnitude relationship between the excitation current i and the excitation current threshold i _max .

Specifically, the ECM stores the standard idle speed N ₀ of the engine and the first output current threshold I _max1 of the generator at the standard idle speed N ₀ (that is, the power generation that the generator separation vibration isolator cannot withstand at the standard idle speed N ₀ ) The maximum output current of the engine), and the MAP map (map) of the corresponding first excitation current threshold i _max1 , and the ECM also stores the idle speed threshold N _max corresponding to the standard idle speed N ₀ , the standard idle speed N ₀ is the idle speed when the comprehensive performance is optimal obtained from experiments, and the idle speed threshold N _max is the maximum idle speed that the AID pulley can withstand in combination with the standard idle speed N ₀ and obtained from experiments. In this way, the ECM in the present invention can infer the magnitude relationship between the output current I of the generator and the first output current threshold I _max1 of the generator by reading the magnitude relationship between the excitation current i and the first excitation current threshold value i _max1 , so as to determine the magnitude relationship between the output current I of the generator and the first output current threshold value I max1 of the generator. The magnitude relationship determines whether it is necessary to adjust the idle speed N and target speed of the engine, so that the output current I of the generator changes due to the change of the idle speed N of the engine, so as to avoid the simultaneous occurrence of high current and low idle speed.

Specifically, the regulation of the engine idle speed by the ECM includes the following situations:

The first case (focus on Figure 3):

If the excitation current i obtained by the ECM is less than the first excitation current threshold value i _max1 , that is, the output current I of the generator is within the range of the first output current threshold value I _max1 , at this time, the ECM does not regulate the idle speed N of the engine, and the engine Keep the current idle speed N unchanged.

The second case (focus on Figure 3):

If the excitation current i obtained by the ECM is greater than or equal to the first excitation current threshold i _max1 , that is, the output current I of the generator exceeds the range of the output current that the AID pulley can withstand, at this time, the ECM sends a speed increase to the engine by The instruction is to increase the target engine speed from the standard idle speed N ₀ to the idle speed threshold N _max to avoid the simultaneous occurrence of the situation that the engine idle speed is too low and the generator output current I is too large.

In the second case, on the basis of increasing the target engine speed from the standard idle speed N ₀ to the idle speed threshold N _max , the MAP also includes a second output corresponding to the idle speed threshold N _max obtained through experiments The current threshold value I _max2 , and the excitation device also includes a second excitation current threshold value i _max2 corresponding to the idle speed threshold value N _max and the second output current threshold value I _max2 . The third case of further regulating the idle speed of the engine on the basis of N _max ) (refer to Figure 3 for emphasis), including the following:

After the target engine speed is increased from the standard idle speed N ₀ to the idle speed threshold N _max , the output current I of the generator decreases because the battery has been charged or the user has turned off some on-board electrical appliances, while the excitation current read by the ECM When i is reduced to less than or equal to the second excitation current threshold i _max2 , the ECM will send a speed increase cancellation command to the engine, and the idle speed N and target speed of the engine will decrease. At this time, due to the small output current I, the AID pulley will The impact of the generator is also small, so the fuel consumption can be reduced by reducing the idle speed N of the engine, and it is also ensured that the generator separation vibration isolator 13 always works within a safe range. In a preferred embodiment, the idle speed N of the engine at this time is reduced from the idle speed threshold N _max after the increase to the standard idle speed N ₀ before the increase.

The present invention is now introduced with a specific embodiment:

During the durability test of a certain model, the generator one-way pulley was damaged. The analysis reason is: the output current of the generator is too large when the engine is idling. The improvement plan is:

First, the ECM sends an idle speed command to the engine, and the engine is in an idle state; considering the influence of comprehensive factors such as fuel consumption and NVH, the standard idle speed N ₀ of the engine is selected through tests, and the ECM is set to make the engine idle speed N in the standard Near the idle speed N ₀ , further use the ECM to read the MAP map of the corresponding relationship between the idle speed N of the engine, the output current I of the generator and the excitation current i of the excitation device, and regulate the idle speed N of the engine. The specific steps to obtain the MAP map are as follows:

At the standard idle speed N ₀ of the engine, measure the maximum output current I of the generator that the generator separation vibration isolator (AID pulley) cannot withstand. For example, when the standard idle speed N ₀ of the engine is 900rpm, measure the power The first output current threshold value Imax ₁ of the machine (the maximum current that the AID pulley can withstand) is 100A, and at this time, the corresponding first excitation current threshold value imax ₁ is unknown;

Then, in combination with the standard idle speed N ₀ , it is determined through experiments that the idle speed threshold N _max at the engine standard idle speed N ₀ is 1000 rpm _; The second output current threshold I _max2 of the generator is 70A. At this time, the corresponding second excitation current threshold value i _max2 is unknown, as shown in the following table:

Idle speed (N) Excitation current (i) Output current (I) 900rpm i_max1 100A 1000rpm i_max2 70A

Further, on the generator performance bench, the first excitation current threshold i _max1 =3.3A and the second excitation current threshold i _max2 =3.1A are measured, so a complete MAP map is obtained, as follows,

Idle speed (N) Excitation current (i) Output current (I) 900rpm 3.3A 100A 1000rpm 3.1A 70A

After measuring the complete MAP map, when the standard idle speed N ₀ of the engine is 900rpm, the obtained MAP map is written and stored in the ECM, and the adjustment strategy for the idle speed N is written and stored in the ECM.

The adjustment strategy for the idle speed N is:

The ECM sends an idle command to the engine to make the engine idle. In the idle state, when the standard idle speed N ₀ of the engine is 900rpm, if the excitation current i read (obtained) by the ECM is less than the first excitation current threshold imax ₁ , that is, less than 3.3A, the ECM does not regulate the idle speed of the engine The rotational speed, that is, when the output current I of the generator is within the normal working range, the idle rotational speed N of the engine keeps the current idle rotational speed N unchanged.

If the excitation current i read (obtained) by the ECM is greater than or equal to the first excitation current threshold imax ₁ , that is, greater than 3.3A, the ECM sends a rotational speed increase command to the engine, that is, when the output current I of the generator exceeds its When it can work normally, increase the target engine speed from the standard idle speed of 900rpm to the idle speed threshold of 1000rpm to avoid the simultaneous occurrence of low idle speed and high current.

After the idle speed N of the engine running increases to the idle speed threshold N _max stored in the ECM, that is, 1000 rpm, the output current I of the generator decreases due to the completion of charging or the user turns off the on-board electrical appliances. If the excitation current i obtained by the ECM at this time is If it is less than the second excitation current threshold imax ₂ (3.1A), the ECM sends a speed increase cancel command to the engine to reduce the target engine speed from the idle speed threshold of 1000rpm to the standard idle speed before the increase of 900rpm.

To sum up, the present invention adjusts the idle speed of the engine by comparing the magnitude relationship between the excitation current and the excitation current threshold through the ECM when the engine is at an idle speed, so that the output current of the generator and the energy consumption of the generator are always in the AID band. Within the safe range that the pulley can bear, if it exceeds the bearable range of the AID pulley, increase the idle speed to avoid the simultaneous occurrence of low speed, large torsional vibration and high consumption of the generator, so as to reduce the double pressure on the AID pulley. (Especially for 3-cylinder engine); and for the existing AMS (Alternator Management System, Chinese: Power Management System) hardware does not change, only through the development of functions and program calibration, can achieve low cost, high reliability and comfort sexual purpose.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. , without departing from the scope of the technical solution of the present invention, when the technical content disclosed above can be used to make some changes or modifications to equivalent embodiments of equivalent changes, as long as it does not depart from the technical solution content of the present invention, according to the technical solution of the present invention Substantially any simple modifications, equivalent changes and modifications made to the above embodiments still fall within the scope of the technical solutions of the present invention.

Claims (8)

1. a method for regulating and controlling the idle speed of an engine, is characterized in that, comprising: The ECM sends an idle command to the engine to make the engine enter the idle state; The ECM controls the idle speed N of the engine with the standard idle speed N ₀ as the target speed; The ECM obtains the idle speed N of the engine, the excitation current i output by the excitation device at the idle speed N, the idle speed threshold N _max corresponding to the standard idle speed N _{0 , and the excitation current threshold corresponding to the standard idle speed N 0 and} the idle speed threshold N _max i _max ; The ECM compares the acquired excitation current i and the excitation current threshold i _max , and adjusts the idle speed N of the engine according to the acquired excitation current i and the excitation current threshold i _max ; The ECM stores the corresponding relationship between the standard idle speed N ₀ and the idle speed threshold N _max and the output current threshold I _max of the generator and the excitation current threshold i _max . By reading the excitation current i, the excitation current i and the excitation current threshold i are determined. The magnitude relationship of _max is obtained, the magnitude relationship between the output current I of the generator and the output current threshold I _max is obtained, and the idle speed N of the engine is regulated, wherein the standard idle speed N0 is the idle speed obtained according to the experiment when the overall performance is optimal, and the idle speed The rotational speed threshold Nmax is the maximum idling rotational speed that can be endured based on the standard idle rotational speed N0 and obtained through experiments; The standard idle speed N ₀ of the engine and the idle speed threshold N _max of the engine are stored in the ECM in advance; the ECM also stores a first output current threshold I _max1 corresponding to the standard idle speed N ₀ of the engine, the excitation current threshold i _max includes a first excitation current threshold i _max1 corresponding to the first output current threshold I _max1 , and the first excitation current threshold i _max1 is stored in the ECM. 2. The method for regulating and controlling the idle speed of an engine according to claim 1, wherein if the excitation current i read by the ECM is less than the first excitation current threshold value i _max1 , the output current I of the generator is at the first output current threshold value I Within the range of _max1 , the ECM does not regulate the idle speed N of the engine, and the engine keeps the current idle speed N unchanged. 3. The method for regulating the idle speed of an engine according to claim 1, wherein if the excitation current i read by the ECM is greater than or equal to the first excitation current threshold i _max1 , the output current I of the generator exceeds the first output current Within the range of the threshold I _max1 , the ECM sends a rotational speed increase command to the engine to increase the target rotational speed of the engine from the standard idle rotational speed N ₀ to the idle rotational speed threshold N _max . 4. The method for regulating the idle speed of an engine according to claim 3, wherein the ECM also stores a second output current threshold _Imax2 obtained through experiments and corresponding to the idle speed threshold _Nmax , and the excitation The current threshold value i _max further includes a second excitation current threshold value i _max2 corresponding to the second output current threshold value I _max2 , the second excitation current threshold value i _max2 is obtained through experiments and stored in the ECM; The output current I decreases, the excitation current i read by the ECM is less than or equal to the second excitation current threshold i _max2 , the ECM sends a speed increase cancel command to the engine, and the idle speed N of the engine decreases. 5. A device for regulating and controlling the idle speed of an engine, characterized in that it comprises an engine, a generator assembly (10) attached to the engine, and an ECM for regulating and controlling the engine, and the generator assembly (10) is provided with a power generator A generator (11) and an excitation device signally connected to the generator (11), the excitation device can output a corresponding excitation current i according to the output current I of the generator; the ECM communicates with the engine through a signal Communication connection, send idle speed command to the engine, regulate and read the idle speed N of the engine; the excitation device is connected with the ECM through signal communication, and outputs the excitation current i to the ECM; the ECM rotates at the standard idle speed N ₀ is the target speed to regulate the idle speed N of the engine, and according to the stored standard idle speed N ₀ and the idle speed threshold N _max corresponding to the standard idle speed N ₀ , obtain respectively the standard idle speed N ₀ and the idle speed threshold N The excitation current threshold i _max corresponding to _max , according to the magnitude relationship between the excitation current i and the excitation current threshold i _max obtained by comparing the read excitation current i to determine the magnitude of the output current I of the generator and the output current threshold I _max , and adjust the output current of the engine. idle speed N; The generator (11) is provided with a generator separation vibration isolator (13), and the generator separation vibration isolator (13) is connected to the generator shaft through bolts; the device for regulating the idle speed of the engine further comprises a belt (20), a tensioner The belt (20) bypasses the pulley of the crankshaft (40), the pulley of the air conditioner compressor (50), and the generator (11) to generate electricity in turn. The pulley of the vibration isolator (13) and the tensioner (30) are separated from the machine to form the gear train of the generator (11). 6 . The device for regulating engine idle speed according to claim 5 , wherein the excitation current threshold i _max includes a first excitation current threshold i _max1 corresponding to the standard idle speed N ₀ of the engine, if the ECM The read excitation current i is smaller than the first excitation current threshold i _max1 , the ECM does not regulate the idle speed N of the engine, and the engine keeps the current idle speed N unchanged. 7 . The device for regulating engine idle speed according to claim 5 , wherein the excitation current threshold i _max includes a first excitation current threshold i _max1 corresponding to the standard idle speed N ₀ of the engine, if the ECM When the read excitation current i is greater than or equal to the first excitation current threshold i _max1 , the ECM sends a speed increase command to the engine to increase the target engine speed from the standard idle speed N ₀ to the idle speed threshold N _max . 8. The device for regulating and controlling the idle speed of an engine according to claim 7, wherein the excitation current threshold value _imax further comprises a second excitation current threshold value _imax2 corresponding to the idle speed threshold value _Nmax . The output current I decreases, the excitation current i read by the ECM is less than or equal to the second excitation current threshold i _max2 , the ECM sends a speed increase cancel command to the engine, and the idle speed N of the engine decreases.

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