JP2008008254A - Control device for negative pressure generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for a negative pressure generator capable of suppressing fluctuation in the engine speed of an internal combustion engine when the engine speed of the internal combustion engine is fluctuated to be lowered in the internal combustion engine with the negative pressure generator used together, and further concretely, capable of preventing the engine stalling of the internal combustion engine, or capable of improving the combustion state of the internal combustion engine, and also suppressing fluctuation in the engine speed. <P>SOLUTION: In an ECU 40A controlling the negative pressure generator 100 composed of an ejector 30 and a VSV (Vacuum Switching Valve) 1 changing an amount of intake air circulating in the ejector 30, as a fluctuation suppressing means controlling the VSV 1 to suppress fluctuation in the engine speed Ne when the engine speed Ne is fluctuated to be lowered, an engine stalling preventing means is provided which controls the VSV 1 to increase the amount of intake air circulating in the ejector 30 when engine speed Ne is drops lower than a first predetermined engine speed α1 during idling and fluctuation in the engine speed Ne before and after the lowering is wider than a first fluctuation degree β1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for a negative pressure generating device, and more particularly to a control device for a negative pressure generating device that controls a negative pressure generating device configured with an ejector.

  Conventionally, in a vehicle, a negative pressure larger than the negative pressure to be taken out from the intake passage of the intake system of the internal combustion engine communicating with each cylinder from the atmosphere (hereinafter also simply referred to as the intake system of the internal combustion engine) is supplied to the brake booster. An ejector is used to do this. The ejector is generally disposed in a bypass path that bypasses the throttle valve, and generates a larger negative pressure due to the venturi effect. As a technique using this ejector, for example, Patent Document 1 discloses a negative pressure source device for a negative pressure booster using an ejector.

JP-A-62-221445

  By the way, the rotational speed of the internal combustion engine may fluctuate so as to decrease due to various factors. Specifically, for example, when the engine is idling, the rotational speed of the internal combustion engine is generally maintained at a target rotational speed by ISC (Idle Speed Control) control. However, if the intake air amount decreases due to unpredictable disturbance or the like, the rotational speed temporarily May decrease. Further, in this case, when the intake air amount is drastically reduced, the ISC control alone does not sufficiently suppress the fluctuation of the rotational speed and the combustion state becomes unstable, and the worst engine stalls in a low rotational speed region such as the idle rotational speed. There is a risk of it. In addition, since the atomization of the injected fuel deteriorates when it is cold, the injected fuel may adhere to the cylinder wall surface or the like and may not contribute to combustion. For this reason, when it is cold, a combustion state may deteriorate and the rotation speed of an internal combustion engine may fall. In this case, since the negative pressure of the intake system decreases as the rotational speed decreases, the flow rate of intake air decreases. When the flow velocity of the intake air is reduced, the atomization of the fuel is further deteriorated. In this case, the rotational speed is further reduced. That is, when the combustion state deteriorates, such a vicious cycle is repeated, and as a result, the deterioration of the combustion state may be prolonged.

  Therefore, the present invention has been made in view of the above problems, and when the internal pressure engine is used together with the negative pressure generator, the rotational speed of the internal combustion engine varies when the rotational speed of the internal combustion engine decreases. An object of the present invention is to provide a control device for a negative pressure generating device that can be suppressed, and more specifically, can prevent engine stall, or improve the combustion state of the internal combustion engine and suppress fluctuations in rotational speed. To do.

  In order to solve the above-described problems, the present invention provides an ejector that generates a negative pressure larger than the negative pressure to be taken out from an intake passage of an intake system of an internal combustion engine, and an intake air amount that changes the amount of intake air flowing through the ejector A negative pressure generator control device for controlling a negative pressure generator configured to include a change means, and when the rotational speed of the internal combustion engine fluctuates so as to decrease, the rotational speed of the internal combustion engine It is characterized by comprising fluctuation suppressing means for controlling the intake air amount changing means so as to suppress the fluctuation of the intake air. The present invention can increase the intake air amount by controlling the intake air amount changing means so as to increase the intake air amount, and control the intake air amount changing means so as to reduce the intake air amount. Focusing on the fact that the negative pressure of the intake system can be increased, it is intended to suppress this fluctuation when the engine speed fluctuates so as to decrease by utilizing these properties. According to the present invention, even when the rotational speed of the internal combustion engine fluctuates so as to decrease, the fluctuation of the rotational speed can be suppressed by increasing the intake air amount or by increasing the negative pressure of the intake system of the internal combustion engine. It is.

  Further, in the present invention, the fluctuation suppressing means is an engine stall prevention means for preventing engine stall of the internal combustion engine, and the engine stall prevention means is configured so that the rotational speed of the internal combustion engine is greater than a first predetermined rotational speed when idling. And the intake air amount changing means is controlled so that the amount of intake air flowing through the ejector increases when the fluctuation degree of the rotational speed of the internal combustion engine before and after the reduction is larger than the first fluctuation degree. May be. Specifically, by utilizing the property that the intake air amount can be increased as in the present invention, in the case where the rotation speed is decreased due to a sudden decrease in the intake air amount in a state where the rotation speed is low, such as during idling. It is possible to prevent engine stall and suppress fluctuations in the rotational speed. In the present invention, the change in the rotation speed after subtracting the rotation speed before the change from the rotation speed after the change is defined as the fluctuation in the rotation speed. Therefore, when the fluctuation degree is larger than the first fluctuation degree, the engine is There is a risk of doing.

  According to the present invention, the fluctuation suppressing means is a combustion state improving means for improving the combustion state of the internal combustion engine, and the combustion state improving means deteriorates the combustion state of the internal combustion engine when cold In addition, the intake air amount changing means may be controlled so that the amount of intake air flowing through the ejector decreases. Specifically, when the air-fuel mixture is diluted due to the fuel adhering to the wall surface of the fuel injected in the cold and the combustion state deteriorates, the property of increasing the negative pressure of the intake system of the internal combustion engine as in the present invention is utilized. By doing so, it is possible to increase the flow rate of the intake air and promote fuel atomization. Thereby, since a combustion state can be improved, the fluctuation | variation of rotation speed can also be suppressed. Note that, for example, intentionally diluting the air-fuel mixture for the purpose of improving fuel efficiency and performing lean combustion itself does not deteriorate the combustion state, so the present invention does not include such a case, but it is a case of lean combustion. However, the combustion state may be deteriorated due to the dilution of the air-fuel mixture due to adhesion of the injected fuel to the wall surface, etc.In such a case, the combustion state in the present invention is deteriorated due to the dilution of the air-fuel mixture. It is included.

  Further, in the present invention, when the combustion state of the internal combustion engine deteriorates, the rotational speed of the internal combustion engine during idling within a predetermined period after completion of the start of the internal combustion engine is lower than a second predetermined rotational speed, And the case where the fluctuation | variation degree of the rotation speed of the said internal combustion engine before and behind fall is larger than a 2nd fluctuation | variation degree may be sufficient. Here, the fuels used in the internal combustion engine are generally light fuels with high volatility (hereinafter simply referred to as light fuels) and heavy fuels with low volatility (hereinafter simply referred to as heavy fuels). There is. When heavy fuel is used, the atomization of the injected fuel tends to be insufficient, so that the combustion state may be deteriorated and the rotational speed may be lowered particularly in the cold immediately after the start is completed. On the other hand, according to the present invention, since the fuel atomization can be promoted by increasing the negative pressure of the intake system of the internal combustion engine, it is possible to improve the combustion state of the internal combustion engine and suppress fluctuations in the rotational speed. . Further, by capturing the deterioration of the combustion state by the fluctuation of the rotational speed as in the present invention, it is possible to improve the combustion state of the internal combustion engine with high responsiveness and to suppress the fluctuation of the rotational speed. It should be noted that the deterioration of the combustion state is not limited to this, and can be grasped by, for example, fluctuations in the air-fuel ratio. Further, in the present invention, a value obtained by subtracting the rotation speed before the change from the rotation speed after the change is defined as the fluctuation degree of the rotation speed, so that the combustion state is changed when the fluctuation degree is larger than the second fluctuation degree. It will be getting worse.

  When the fluctuation suppressing means is an engine stall prevention means, the engine stall prevention means fully opens the flow path when the intake air amount changing means is realized by, for example, a flow control valve that can change the degree of shielding of the flow path. By controlling this flow control valve so as to communicate with the intake air, the amount of intake air can be maximized. Thereby, the fluctuation | variation of rotation speed can be suppressed suitably. Further, the present invention is not limited to this, and the engine stall prevention means may communicate the flow path by controlling the intake air amount changing means so as to shield the flow path at a predetermined degree so as not to completely stop the function of the ejector, for example. . In this case, the predetermined degree may be reduced as the degree of fluctuation in the rotational speed is large or the degree of rotational speed is low, depending on the degree of fluctuation in the rotational speed or the magnitude of the rotational speed. Is possible. In addition, when the intake air amount changing means is realized by, for example, a control valve that can change the flow path to fully open or fully closed, the engine stop prevention means controls the control valve to fully open to maximize the intake air amount. Can be increased.

  Further, when the fluctuation suppressing means is a combustion state improving means, when the intake air amount changing means is realized by, for example, a flow rate adjusting valve capable of changing the degree of shielding of the flow path, the combustion state improving means is the flow path. By controlling this flow control valve so as to shield the valve fully closed, the amount of intake air can be made zero. Thereby, the fluctuation | variation of rotation speed can be suppressed suitably. Further, the present invention is not limited to this, and the combustion state improving means may control the intake air amount changing means so as to shield the flow path at a predetermined degree so as not to completely stop the function of the ejector, for example. In this case, the predetermined degree may be increased as the degree of fluctuation in the rotational speed is large or the degree of rotational speed is low, depending on the degree of fluctuation in the rotational speed or the magnitude of the rotational speed. Is possible. In addition, when the intake air amount changing means is realized by, for example, a control valve that can change the flow path to fully open or fully closed, the combustion state improving means controls the control valve to fully close so that the intake air amount Can be made zero.

  According to the present invention, it is possible to suppress fluctuations in the rotational speed of the internal combustion engine when the internal combustion engine that is used together with the negative pressure generator varies so that the rotational speed of the internal combustion engine decreases. It is possible to provide a control device for a negative pressure generator that can prevent engine stall or improve the combustion state of the internal combustion engine and suppress fluctuations in the rotational speed.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram schematically showing a control device for a negative pressure generating device according to the present embodiment, which is realized by an ECU (Electronic Control Unit) 40A, together with the negative pressure generating device 100. The components shown in FIG. 1 including the internal combustion engine 50 are mounted on a vehicle (not shown). The intake system 10 of the internal combustion engine 50 includes an air cleaner 11, an air flow meter 12, an electric throttle 13, an intake manifold 14, an intake port (not shown) communicating with each cylinder (not shown) of the internal combustion engine 50, and the configuration thereof. For example, intake pipes 15a, 15b and the like are appropriately disposed between the two. The air cleaner 11 is configured to filter the intake air supplied to each cylinder of the internal combustion engine 50, and communicates with the atmosphere via an air duct (not shown). The air flow meter 12 is configured to measure the intake flow rate and outputs a signal corresponding to the intake flow rate.

  The electric throttle 13 includes a throttle valve 13a, a throttle body 13b, a valve shaft 13c, and an electric motor 13d. The throttle valve 13a is configured to adjust the total intake flow rate supplied to each cylinder of the internal combustion engine 50 by changing the opening. The electric throttle 13 is also configured to adjust the intake flow rate in order to control the idle speed. The throttle body 13b is composed of a cylindrical member in which an intake passage is formed, and pivotally supports a valve shaft 13c of a throttle valve 13a disposed in the intake passage. The electric motor 13d is configured to change the opening degree of the throttle valve 13a under the control of the ECU 40A, and a step motor is adopted as the electric motor 13d. The electric motor 13d is fixed to the throttle body 13b, and its output shaft (not shown) is connected to the valve shaft 13c. The opening degree of the throttle valve 13a is detected by the ECU 40A based on an output signal from an encoder (not shown) incorporated in the electric throttle 13 (hereinafter simply referred to as an encoder).

  The throttle mechanism is preferably a throttle-by-wire system in which a throttle valve 13a such as an electric throttle 13 is driven by an actuator. However, the present invention is not limited to this. For example, a mechanical throttle mechanism in which the opening of the throttle valve 13a is changed in conjunction with an accelerator pedal (not shown) via a wire or the like instead of the electric throttle 13 may be applied. Good. The intake manifold 14 is configured to branch one intake passage on the upstream side corresponding to each cylinder of the internal combustion engine 50 on the downstream side, and distributes intake air to each cylinder of the internal combustion engine 50.

  The brake device 20 includes a brake pedal 21, a brake booster 22, a master cylinder 23, and a wheel cylinder (not shown). The brake pedal 21 operated by the driver to brake the rotation of the wheel is connected to an input rod (not shown) of the brake booster 22. The brake booster 22 is configured to generate an assist force with a predetermined boost ratio with respect to the pedal depression force, and a negative pressure chamber (not shown) internally partitioned on the master resin 23 side To the intake passage of the intake manifold 14. The output rod (not shown) of the brake booster 22 is further connected to the input shaft (not shown) of the master cylinder 23. The master cylinder 23 receives the assist force in addition to the pedal depression force. Hydraulic pressure is generated according to the applied force. The master cylinder 23 is connected to each wheel cylinder provided in a disc brake mechanism (not shown) of each wheel via a hydraulic circuit, and the wheel cylinder generates a braking force with the hydraulic pressure supplied from the master cylinder 23. . The brake booster 22 is not particularly limited as long as it is a pneumatic type, and may be a general one.

  The ejector 30 is configured to generate a negative pressure larger than the negative pressure to be taken out from the intake system 10, more specifically, the intake manifold 14, and supply it to the negative pressure chamber of the brake booster 22. The ejector 30 has an inflow port 31a, an outflow port 31b, and a negative pressure supply port 31c. Among these, the negative pressure supply port 31c is connected to the negative pressure chamber of the brake booster 22 by the air hose 5c. The inflow port 31a is connected to the intake passage of the intake pipe 15a by an air hose 5a, and the outflow port 31b is connected to the intake passage of the intake manifold 14 by an air hose 5b so as to sandwich the electric throttle 13, more specifically the throttle valve 13a. ing. Thus, a bypass path B that bypasses the electric throttle 13 is formed by the air hoses 5 a and 5 b including the ejector 30. When the ejector 30 is not functioning, the negative pressure chamber of the brake booster 22 is connected to the intake manifold 14 via the air hose 5b, the outlet port 31b of the ejector 30, the negative pressure supply port 31c, and the air hose 5c. Negative pressure is supplied.

  A VSV (vacuum switching valve) 1 is interposed in the air hose 5a. The VSV 1 is configured to communicate and block the bypass path B under the control of the ECU 40A. In the present embodiment, a 2-position 2-port normally closed solenoid valve is employed. However, the present invention is not limited to this, and the VSV 1 may be another appropriate electromagnetic valve or the like, and may be, for example, a flow rate adjustment valve that can control the degree of shielding of the flow path. Further, the VSV 1 is configured to change the amount of intake air flowing through the ejector 30 and to function or stop the function of the ejector 30 by communicating and blocking the bypass passage B. In the present embodiment, the intake air amount changing means is realized by VSV1.

  FIG. 2 is a diagram schematically showing the internal configuration of the ejector 30. The ejector 30 includes a diffuser 32 inside. The diffuser 32 includes a tapered taper portion 32a, a divergent taper portion 32b, and a negative pressure extraction portion 32c corresponding to a passage communicating these. The tapered taper portion 32a is opened so as to face the inflow port 31a, and the divergent taper portion 32b is opened so as to face the outflow port 31b. Moreover, the negative pressure extraction part 32c is connected to the negative pressure supply port 31c. The inflow port 31a is provided with a nozzle 33 for injecting the inflowing intake air toward the tapered portion 32a. The intake air injected from the nozzle 33 flows through the diffuser 32, and further from the outflow port 31b to the air hose 5b. To leak. At this time, a high-speed jet is generated in the diffuser 32 to generate a large negative pressure in the negative pressure extraction portion 32c due to the venturi effect, and this negative pressure is further reduced from the negative pressure supply port 31c through the air hose 5c to the negative pressure chamber. To be supplied. Due to the function of the ejector 30, the brake booster 22 can obtain a larger negative pressure than when the brake booster 22 is taken out from the intake manifold 14. The internal flow path between the negative pressure extraction part 32c and the negative pressure supply port 31c, the internal flow path between the outflow port 31b and the negative pressure supply port 31c, and the air hose 5c connection part of the brake booster 22 The provided reverse support valves 34 are for preventing backflow. Further, the ejector 30 is not limited to the one having the internal structure shown in FIG. 2, and an ejector having another different internal structure may be applied instead of the ejector 30.

  The internal combustion engine 50 includes a combustion injection valve (not shown), and the fuel injection valve is opened at an appropriate injection timing under the control of the ECU 40A and is closed after an appropriate injection time has elapsed. Fuel is supplied to the fuel injection valve from a fuel pump (not shown), and the fuel pump pressurizes the fuel to an appropriate fuel injection pressure under the control of the ECU 40A. Thus, the fuel injection valve injects an appropriate amount of fuel at an appropriate timing. The arrangement of the fuel injection valve is not particularly limited. For example, even if the combustion injection valve is arranged to inject fuel directly into the cylinder, it is arranged to inject fuel into the intake port. Also good. The internal combustion engine 50 may include both a fuel injection valve for directly injecting fuel into the cylinder and a fuel injection valve for injecting fuel into the intake port.

  The ECU 40A includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output circuit, and the like (not shown). The ECU 40A mainly has a configuration for controlling the internal combustion engine 50. In this embodiment, the ECU 40A also controls the VSV 1, the electric throttle 13, and the like. In addition to the VSV 1 and the electric throttle 13, various control objects are connected to the ECU 40A via a drive circuit (not shown). Further, the ECU 40A detects the VSV1 state detection sensor (not shown) for detecting the operating state of the VSV1, the accelerator sensor (not shown) for detecting the state of the encoder and the accelerator pedal, and the rotational speed Ne of the internal combustion engine 50. Various sensors such as a crank angle sensor (not shown) and a water temperature sensor (not shown) for detecting the water temperature of the internal combustion engine 50 are connected.

  The ROM is configured to store a program in which various processes executed by the CPU are described. In this embodiment, the ROM circulates the ejector 30 under various conditions in addition to the program for controlling the internal combustion engine 50. A VSV1 control program for controlling the VSV1 so as to change the amount of intake air and to cause the ejector 30 to function or stop functioning (hereinafter also simply referred to as opening or closing VSV1) is also stored. However, these programs may be combined together. In this embodiment, the VSV1 control program is configured to include a fluctuation suppressing program for controlling the VSV1 so as to suppress fluctuations in the rotational speed Ne when the rotational speed Ne fluctuates so as to decrease. ing. Further, in the present embodiment, the fluctuation suppressing program specifically includes the idling rotation speed Ne lower than the first predetermined rotation speed α1, and the fluctuation degree of the rotation speed Ne before and after the decrease is the first. The engine is an engine stall prevention program for controlling the VSV 1 so that the amount of intake air flowing through the ejector 30 increases when the degree of variation β1 (<0) is greater. In the present embodiment, various control means, detection means, determination means, and the like are realized by the CPU, ROM, RAM (hereinafter also referred to as CPU, etc.) and the above-described various programs. Thus, the fluctuation suppressing means and the engine stall preventing means are realized. In the present embodiment, the negative pressure generator 100 is realized by the VSV 1 and the ejector 30.

  Next, a process performed by the ECU 40A when controlling the VSV 1 to prevent the internal combustion engine 50 from stalling when the intake air amount suddenly decreases during idling will be described in detail with reference to the flowchart shown in FIG. The ECU 40A controls the VSV 1 by repeatedly executing the process shown in the flowchart in a very short time based on the engine stall prevention program stored in the ROM. The CPU executes a process of determining whether or not the idling is ON, that is, whether or not it is idling (step 11). Whether or not the idling is ON can be determined based on, for example, an output signal of an accelerator sensor. If a negative determination is made in step 11, it is determined that the rotational speed Ne is sufficiently large and the possibility that the internal combustion engine 50 is stalled is low, and the CPU executes a process for closing VSV1 (step 15). If VSV1 is already closed, this step may be skipped.

  On the other hand, if the determination in step 11 is affirmative, the CPU executes a process of determining whether or not the rotational speed Ne is smaller than the first predetermined rotational speed α1 (step 12). The first predetermined rotational speed α1 is set to a rotational speed at which there is a possibility that the engine stalls even if the intake air amount suddenly decreases due to an unpredictable disturbance or the like, and the response is not in time only by the ISC control. . If the determination in step 12 is negative, there is a low possibility that the engine stalls. On the other hand, if an affirmative determination is made in step 12, the CPU executes a process of determining whether or not the variation degree of the rotational speed Ne is greater than a first predetermined degree β1 (<0) (step 13). The first predetermined degree β1 is set to such a degree that if the intake air amount actually decreases due to an unpredictable disturbance or the like, if the intake air amount further decreases, the ISC control alone will not be able to cope with it and the engine may be stalled. . When the determination is made using the magnitude of the fluctuation level of the rotation speed Ne instead of the fluctuation degree of the rotation speed Ne, the magnitude of the fluctuation degree of the rotation speed Ne is the magnitude of the first predetermined degree β1 in step 11. Alternatively, it may be determined whether or not it is larger than the above.

  If the determination in step 13 is negative, there is a low possibility that the engine stalls. On the other hand, if the determination in step 13 is affirmative, the CPU executes a process for opening VSV 1 (step 14). As a result, the intake air amount can be increased, so that the internal combustion engine 50 can be prevented from being stalled and fluctuations in the rotational speed Ne can be suppressed. When VSV1 is realized by a flow rate control valve that can change the degree of shielding of the flow path, instead of opening VSV1 in step 14, for example, a predetermined degree so as not to completely stop the function of ejector 30. It is also possible to control the VSV 1 so as to shield the flow path. In this case, a program for controlling the VSV 1 may be stored in the ROM so as to shield the flow path at a predetermined degree as the engine stall prevention program. As described above, when the internal combustion engine 50 used together with the negative pressure generator 100 changes so that the rotational speed Ne decreases, the fluctuation of the rotational speed Ne can be suppressed. More specifically, the internal combustion engine 50 is stalled. It is possible to realize the ECU 40A that can prevent this and suppress fluctuations in the rotational speed Ne.

  The ECU 40B according to the present embodiment distributes the ejector 30 when the fluctuation suppressing program is deteriorated due to, for example, a lean air-fuel mixture when the combustion state of the internal combustion engine 50 is cold instead of the engine stall prevention program. The ECU 40A is the same as the ECU 40A according to the first embodiment except that it is a combustion state improvement program for controlling the VSV 1 so that the amount of intake air is reduced. Here, since the atomization of the injected fuel is deteriorated when it is cold, the injected fuel may adhere to the cylinder wall surface and the like and may not contribute to combustion. For this reason, when it is cold, the air-fuel mixture becomes lean, so that the combustion state is deteriorated and the rotational speed Ne may be reduced. In this case, since the negative pressure of the intake manifold 14 decreases as the rotational speed Ne decreases, the intake air flow rate decreases. Moreover, since the atomization of the fuel is further deteriorated when the flow velocity of the intake air is decreased, the rotational speed Ne is further decreased, and as a result of repeating such a vicious cycle, the deterioration of the combustion state may be prolonged. In addition, when heavy fuel is used, atomization of the injected fuel tends to be insufficient, so that the combustion state deteriorates and the rotational speed Ne decreases particularly during the cold immediately after the start is completed. is there.

  For this reason, in the present embodiment, the combustion state improving program assumes that when the combustion state of the internal combustion engine 50 has deteriorated, specifically, the idling speed Ne within the predetermined period after the completion of the start of the internal combustion engine 50 is the second. In order to control the VSV 1 so that the amount of intake air flowing through the ejector 30 is reduced when the degree of fluctuation of the rotational speed Ne before and after the reduction is greater than the second fluctuation degree β2 that is lower than the predetermined speed α2. It is a program. Moreover, each structure with which a vehicle is provided is the same as each structure shown in Example 1 except ECU40A. In this embodiment, the combustion state improving means is realized by the CPU and the like and the combustion state improving program.

  Next, when the internal combustion engine 50 controls the VSV 1 to improve the combustion state when the combustion state deteriorates within a predetermined period after the completion of the start of the internal combustion engine 50, the process performed by the ECU 40B is used with the flowchart shown in FIG. Will be described in detail. The process shown in this flowchart is executed within a predetermined period (for example, 30 seconds) after the start of the internal combustion engine 50 is completed. The CPU executes a process of determining whether or not the water temperature is lower than a predetermined value γ, that is, whether or not it is cold (step 21). This predetermined value γ is set to a value (for example, 70 ° C.) indicating that it is cold. If the determination in step 21 is negative, it is determined that there is little risk of deterioration of the combustion state because warming is complete and warm, and the CPU executes processing for closing VSV1 (step 24). This step is provided because the deterioration determination of the combustion state in step 22 described later may be widely performed during cold weather. Further, the reason why the VSV 1 is closed in this step is to improve the fuel efficiency performance in the warm state. If VSV1 is already closed, this step may be skipped.

  On the other hand, if the determination in step 21 is affirmative, the CPU executes processing for determining whether or not the combustion state has deteriorated (step 22). Specifically, in this step, whether or not the rotational speed Ne at idling has decreased below the second predetermined rotational speed α2 and, if it has decreased, the degree of variation of the rotational speed Ne before and after the decrease is the second fluctuation. It is determined whether or not the degree is greater than β2. The second predetermined rotational speed α2 is set to a rotational speed that can be lowered when the deterioration of the combustion state proceeds viciously due to the use of heavy fuel or the like. Then, the second predetermined rotation speed α2 is preferably set to an appropriate rotation speed from the viewpoint of detecting early deterioration of the combustion state within a range where there is no possibility of erroneous determination. Further, the second predetermined degree β2 is set to such a degree that it can fluctuate when the deterioration of the combustion state proceeds viciously due to the use of heavy fuel or the like. On that basis, the second variation degree is preferably set to an appropriate degree from the viewpoint of detecting a state where the vicious circle is still progressing and there is a possibility that the deterioration of the combustion state may be prolonged. . When the determination is made using the magnitude of the fluctuation level of the rotation speed Ne instead of the fluctuation degree of the rotation speed Ne, the magnitude of the fluctuation degree of the rotation speed Ne is larger than the second predetermined degree β2 in this step. Alternatively, it may be determined whether or not it is larger than the above.

  If a negative determination is made in step 22, it is determined that the combustion state is not particularly deteriorated, and the CPU executes a process for opening VSV1 (step 23). Note that this step may be skipped if the VSV 1 is already open. On the other hand, if an affirmative determination is made in step 22, the CPU executes processing for closing VSV 1 (step 24). As a result, the negative pressure in the intake manifold 14 increases and the flow rate of the intake air can be increased, so that the atomization of the fuel can be promoted, thereby improving the combustion state and suppressing fluctuations in the rotational speed. When VSV1 is realized by a flow rate control valve or the like that can change the degree of shielding of the flow path, instead of closing VSV1 in step 24, for example, a predetermined degree so as not to completely stop the function of ejector 30. It is also possible to control the VSV 1 so as to shield the flow path. In this case, a program for controlling the VSV 1 may be stored in the ROM so as to shield the flow path at a predetermined degree as a combustion improvement program.

  By the way, not only within a predetermined period after the start of the internal combustion engine 50 but also when the fuel injection amount increases during the acceleration operation, the air-fuel mixture temporarily becomes lean due to adhesion of the injected fuel to the wall surface or the like. As a result, hesitation may occur. This hesitation is particularly likely to occur during cold weather when fuel atomization worsens. For this reason, as the combustion deterioration determination in step 22, for example, it may be determined instead of whether or not the fuel injection amount has increased during the acceleration operation. Specifically, whether or not the fuel injection amount has increased during the acceleration operation can be determined based on, for example, whether or not the accelerator pedal has been depressed based on the output signal of the accelerator sensor. If an affirmative determination is made in this case, the atomization of the fuel can be promoted by executing processing for closing the VSV 1 by the CPU in step 24, thereby improving the combustion state and suppressing fluctuations in the rotational speed. Can do.

  In this case, the process shown in the flowchart is not limited to a predetermined period after the completion of the start of the internal combustion engine 50 but is widely performed in the cold state. In this case, it is preferable that the process shown in the flowchart is performed when it is determined that the combustion state has deteriorated within a predetermined period after the start of the internal combustion engine 50 is completed. As a result, it can be predicted that hesitation will occur with high probability during cold acceleration. As described above, when the internal combustion engine 50 used together with the negative pressure generator 100 changes so that the rotational speed Ne decreases, the fluctuation of the rotational speed Ne can be suppressed. More specifically, the combustion state of the internal combustion engine 50 It is possible to realize the ECU 40B capable of improving the engine speed and suppressing the fluctuation of the rotational speed Ne.

  The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.

2 is a diagram schematically showing a control device for a negative pressure generating device realized by an ECU 40A together with the negative pressure generating device 100. FIG. 3 is a diagram schematically showing an internal configuration of an ejector 30. FIG. It is a figure which shows the process performed by ECU40A with a flowchart. It is a figure which shows the process performed by ECU40B with a flowchart.

Explanation of symbols

1 VSV
30 Ejector 40 ECU
50 Internal combustion engine 100 Negative pressure generator

Claims (4)

Negative pressure configured to include an ejector that generates a negative pressure larger than the negative pressure to be taken out from the intake passage of the intake system of the internal combustion engine, and an intake air amount changing means that changes the amount of intake air flowing through the ejector A negative pressure generator control device for controlling the generator,
Negative pressure generation characterized by comprising fluctuation suppressing means for controlling the intake air amount changing means so as to suppress fluctuations in the rotational speed of the internal combustion engine when the rotational speed of the internal combustion engine fluctuates so as to decrease Control device for the device. The fluctuation suppression means is an engine stall prevention means for preventing engine stall of the internal combustion engine, and the engine stall prevention means reduces the rotational speed of the internal combustion engine below a first predetermined rotational speed during idling, and The intake air amount changing means is controlled so that the amount of intake air flowing through the ejector increases when the degree of fluctuation of the rotational speed of the internal combustion engine before and after the decrease is larger than the first fluctuation degree. The control apparatus of the negative pressure generator of Claim 1. The fluctuation suppressing means is a combustion state improving means for improving the combustion state of the internal combustion engine, and the combustion state improving means is configured to switch the ejector when the combustion state of the internal combustion engine deteriorates during the cold state. 2. The control device for a negative pressure generating device according to claim 1, wherein the intake air amount changing means is controlled so as to reduce the amount of intake air flowing. When the combustion state of the internal combustion engine deteriorates, the rotational speed of the internal combustion engine during idling within a predetermined period after the start of the internal combustion engine is lower than a second predetermined rotational speed, and before and after the decrease. 4. The control device for a negative pressure generating device according to claim 3, wherein the fluctuation degree of the rotational speed of the internal combustion engine is larger than the second fluctuation degree.

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