JPH06257479A - Control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a control device for an internal combustion engine, which costs low, improves fuel consumption and exhaust performance, and can use another liquid fuel such as gasoline in combination. CONSTITUTION:When a switching operation from a CNG fuel supplying condition to a gasoline fuel supplying condition is carried out (S46), a residual CNG fuel amount QfcT is computed on the basis of the final flow rate Qfc1Final in the CNG fuel supplying condition right before switching ($61), and the basic gasoline fuel supply rate QfgT1 is computed by subtracting the residual CNG fuel QfcT and adding a wall flow amount in gasoline fuel supply starting (S62). Then, a feedback correction is carried out (S64), and switching is carried out when finish of switching is determined on the basis of the residual CNG fuel (S65).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine which includes at least a gas fuel supply device for supplying gas fuel and also has a liquid fuel supply device for supplying liquid fuel. Regarding the device.

[0002]

2. Description of the Related Art Gasoline, light oil, etc. are mainly used as a fuel for an internal combustion engine. In view of various problems such as pollution by harmful exhaust substances and exhaustion of resources, C has recently been used as an alternative fuel.
NG (compressed natural gas), LNG (liquefied natural gas), etc. are receiving attention. Here, as an electronically controlled fuel supply device for supplying a fuel other than gasoline as a fuel, Japanese Patent Laid-Open No. Sho 64-64
JP-A-36956 discloses an engine that supplies LNG / hydrogen fuel that is a gas fuel, provides a premix (chamber) supply system at the time of fuel switching, and controls the opening / closing valve of each fuel to request combustion at the time of switching. Soften the difference in characteristics in the premix chamber,
Switching is in progress.

Further, Japanese Utility Model Laid-Open No. 3-47453 discloses an engine for supplying LNG which is a gas fuel, and controls to completely use up the fuel in the fuel supply system when the engine is stopped. In addition, Japanese Utility Model Publication No. 63-125154 discloses that
An engine that supplies LNG / methanol reformed gas that is a gas fuel using the same vaporizer is disclosed, and smooth fuel switching upstream of the vaporizer is performed without causing fuel exhaustion.

Further, Japanese Patent Application Laid-Open No. 3-210037 discloses an engine for supplying gasoline / alcohol as a liquid fuel, and a fuel sensor (oxygen concentration meter) for gasoline and alcohol is used to obtain a mixing ratio of fuels to determine the concentration. The average value of the corresponding fuel correction amount is calculated and the fuel is supplied.

[0005]

However, in such a control device for an internal combustion engine, an ordinary carburetor having a constant bore is used to supply gas fuel.
Since they are trying to obtain the required flow metering performance and pressure regulation performance, their dynamic range is narrow and it is not possible to adapt to a wide range of operating conditions.

Further, there is a drawback in using a gas fuel and a liquid fuel as a mixture, as described below. That is, liquid fuel has a delay related to fuel adherence to the side wall of the combustion chamber and control responsiveness, whereas gaseous fuel mixes with air earlier than liquid fuel does not have such a delay. In addition, since differences in the physical properties of liquid fuel and gas fuel have not been taken into consideration in the past, in engines that use both gas and liquid as fuel, obtain low emissions, low fuel consumption, and high output. Is difficult.

Further, even in a gas fuel supply device for supplying only gas as fuel, in order to improve the operation performance of the gas fuel supply device, the dynamic range is expanded and the cylinders are uniformly distributed. Is desirable, but
Since the device becomes large, it cannot be sufficiently expanded, and therefore, there is a problem that the transient response cannot be improved and the air-fuel ratio feedback control cannot be properly performed.

The present invention has been made by paying attention to such conventional problems. It does not increase the size of the apparatus, it is low in cost and highly reliable, and the fuel consumption and exhaust performance can be improved. It is an object of the present invention to provide a control device for an internal combustion engine, which includes at least a gas fuel supply device capable of achieving the above, and which can be used together with a liquid fuel such as gasoline.

[0009]

Therefore, as shown in FIG. 1, a control device for an internal combustion engine according to the present invention is divided into a pressure adjusting portion for adjusting a gas fuel pressure and a downstream side of the pressure adjusting portion. Formed in the gas passage after the branch passages have joined together, and a flow rate adjusting portion which is interposed in each of the branch passages formed by A gas fuel supply device including a multi-trachea that guides the gas fuel to each cylinder, engine operating state detecting means for detecting an engine operating state, and a plurality of solenoid valves of the plurality of solenoid valves according to the engine operating state. And a gas fuel supply amount control means for controlling opening and closing to control the gas fuel supply amount.

Further, among the plurality of solenoid valves for adjusting the gas fuel flow rate, at least the small flow rate adjusting solenoid valve may perform duty control at a predetermined control cycle. Further, the plurality of solenoid valves include n solenoid valves each having a different flow rate, and the flow rate of another solenoid valve is set to 2 ⁿ with respect to the minimum flow rate of the ⁿ solenoid valves. You may be allowed to.

Further, the plurality of solenoid valves having different valve opening flow rates are duty-controlled, and the duty control of each solenoid valve is controlled so that the total flow rate of all the solenoid valves in the open state is kept substantially constant over time. The phase may be set. Further, as shown in FIG. 2, an internal combustion engine control device according to the present invention includes the gas fuel supply device, an engine operating state detection means, and a gas fuel supply amount control means, and supplies liquid fuel to each cylinder. Liquid fuel supply device, liquid fuel supply amount control means for controlling the liquid fuel supply amount according to the engine operating state, and fuel switching means for switching fuel supplied to the engine to gas fuel or liquid fuel according to the engine operating state And, including.

Further, the fuel switching means may switch the fuel after confirming that the fuel switching conditions are satisfied after the fuel switching request. Further, the fuel switching means,
In the fuel system before switching the fuel supply, after the supply of the fuel supply source on the upstream side is cut off, the remaining fuel is completely supplied from the fuel supply source to the fuel supply unit that directly supplies the fuel to the engine on the downstream side. The fuel switching confirmation means for confirming that the fuel switching is completed, and the operation stopping means for stopping the operation of the fuel supply unit after confirmation of the completion of the fuel switching. Based on the fuel supply amount of the supplied fuel and the set fuel supply amount when only the switched fuel is supplied according to the operating state immediately after the completion of the switching, the fuel system before the switching is completed before the completion of the switching. It may be configured to include mixed fuel supply amount setting means for setting the fuel supply amount of the switched fuel supplied together with the residual fuel.

Further, the fuel switching confirmation means confirms completion of switching from the gas fuel to the liquid fuel based on the gas fuel supply delay time constant relating to the gas fuel, and the fuel switching confirmation means switches from the gas fuel to the liquid fuel. When the fuel supply amount related to the liquid fuel to be supplied immediately after the switching is confirmed after the switching is confirmed, the gas fuel supply delay time constant related to the gas fuel and the liquid fuel supply delay time constant related to the liquid fuel are calculated. Based on the above, the fuel supply amount of the liquid fuel supplied together with the residual fuel of the gas fuel system before the completion of the switching may be set.

Further, the fuel switching confirmation means confirms the completion of switching from the liquid fuel to the gas fuel based on the liquid fuel supply delay time constant related to the liquid fuel, and the fuel switching confirmation means makes the switching from the liquid fuel to the gas fuel. When the fuel supply amount related to the gas fuel supplied immediately after the switching is confirmed after the switching is confirmed, the liquid fuel is supplied before the switching is completed based on the liquid fuel supply delay time constant related to the liquid fuel. You may make it set the fuel supply amount regarding the gas fuel supplied with the residual fuel of a system.

Further, when the operating state detected by the engine operating state detecting means is an operating state in which the cooling water temperature is lower than a predetermined temperature, the gas fuel supply control is performed, and at the time of starting and during the gas fuel supply control. It is also possible to perform duty control with a fine cycle width in the operating area below the load area and to perform duty control with a large cycle width in the high load area.

It is also possible to include an ignition timing setting means for setting the ignition timing based on the engine operating state after the completion of fuel switching is confirmed by the fuel switching confirmation means. Further, it may be configured to include an exhaust gas recirculation rate setting unit that sets an exhaust gas recirculation rate based on the engine operating state after the fuel switch confirmation unit confirms the completion of fuel switching.

The gas fuel may be CNG fuel and the liquid fuel may be gasoline fuel.

[0018]

With the above arrangement, in the control device for an internal combustion engine according to the present invention, the gas fuel supply amount control means selects opening / closing of a plurality of solenoid valves provided in the flow rate adjusting unit according to the engine operating state. Then, the gas fuel supply amount is controlled. Further, when at least the small flow rate adjusting solenoid valve among the plurality of solenoid valves for adjusting the gas fuel flow rate performs duty control at a predetermined control cycle, it becomes possible to control a fine control width by the duty control. It is possible to improve controllability.

Further, a plurality of solenoid valves for adjusting the gas fuel flow rate are included, including n solenoid valves having different flow rates, and the solenoid valve having the minimum flow rate out of the n solenoid valves is provided with another solenoid valve. When the flow rate is set to 2 ⁿ , it is possible to obtain a wide variety of fully open flow rates by combining various solenoid valves. That is, if the predetermined fully open flow rate is a, then a × 2
= 2a, ax2 ² = 4a, ax2 ³ = 8a, ax2 ⁴ =
By including a solenoid valve having a fully open flow rate such as 16a, a, 2a, 3a (= a + 2a), 4a, 5a
(= A + 4a), 6a (= 2a + 4a), 7a (= a +
2a + 4a), ..., It is possible to obtain all flow rates. In other words, with the minimum flow rate as the unit flow rate, the total flow rate can be variably set for each unit flow rate.

Further, the plurality of solenoid valves having different valve opening flow rates are duty-controlled respectively, and the duty control of each solenoid valve is controlled so that the total flow rate of all the solenoid valves in the open state is kept substantially constant over time. By setting the phase, the change in the flow rate between the open / closed states due to the duty control is reduced, and the controllability can be improved without being affected by the opening / closing of the large flow rate adjusting solenoid valve.

Furthermore, the internal combustion engine control device according to the present invention is provided with the gas fuel supply device, the engine operating state detection means, and the gas fuel supply amount control means, and the liquid fuel supply device, the liquid fuel supply amount control means, and A fuel switching means for switching the fuel supplied to the engine to a gas fuel or a liquid fuel is further included. Further, after confirming that the fuel switching condition is satisfied after the fuel switching request, the fuel switching means In the fuel system before switching the fuel supply, after switching off the supply of the upstream fuel supply source to the fuel supply unit that directly supplies the fuel from the fuel supply source to the downstream engine. Fuel switching confirmation means for confirming that the remaining fuel has been completely supplied, and operation stopping means for stopping the operation of the fuel supply section after confirmation of completion of the fuel switching are included. In the system, based on the fuel supply amount of the fuel supplied immediately before the fuel switching by the fuel switching confirmation means and the set fuel supply amount when only the fuel after switching is supplied according to the operating state immediately after the completion of the switching. And a mixed fuel supply amount setting means for setting the fuel supply amount related to the fuel after switching, which is supplied together with the residual fuel in the fuel system before switching, before the completion of switching. This will be described with reference to the flowchart shown in FIG.

In step 21 (denoted as S21 in the figure; the same applies hereinafter), the existence of gas fuel and liquid fuel is confirmed, which fuel is to be used is selected, and the existence of gas fuel is confirmed. At the same time, the safety valve is brought into a working state, and when the presence of the liquid fuel is confirmed, the liquid fuel supply system to the injector as the fuel supply section works. That is, the fuel switching means switches the fuel supplied to the engine to the gas fuel or the liquid fuel.

Next, when the fuel switching request is confirmed in step 22, the process proceeds to step 24, and control for switching from CNG fuel to gasoline fuel is performed, or the process proceeds to step 28 to switch from gasoline fuel to CNG fuel. Control is performed. Then, in step 25 or step 29, if it is confirmed that the residual fuel has been supplied up to the fuel supply section even after the supply of the fuel supply source on the upstream side is cut off, step 27 or step is performed after the confirmation. At 31,
The operation of the fuel supply unit is stopped.

On the other hand, in step 24 or step 28, in the fuel system after the fuel supply switching, the fuel supply amount of the fuel supplied immediately before the fuel switching is taken into consideration, and the fuel system before the switching is completed before the switching is completed. The fuel supply amount of the switched fuel supplied together with the residual fuel is set. Meanwhile, step
When it is determined in 22 whether the fuel is selected or not, when the fuel is not selected, the process proceeds to Step 23, and the supply of the determined fuel is continued.

When the gas fuel is switched to the liquid fuel, the completion of the switching is confirmed based on the consumption of the gas fuel in the supply pipe such as a manifold. When the switching from the gas fuel to the liquid fuel is confirmed, when calculating the fuel supply amount of the liquid fuel supplied immediately after the switching, the gas fuel supply delay time constant of the gas fuel and the liquid of the liquid fuel are calculated. By calculating the fuel supply amount of the liquid fuel supplied before the completion of the switching based on the fuel supply delay time constant, the time and wall flow until the gas fuel in the supply pipe such as a manifold is consumed. The influence of the liquid fuel adhering to the intake passage is taken into consideration.

Further, when the liquid fuel is switched to the gas fuel, the completion of the switching is confirmed based on the wall flow, and the switching from the liquid fuel to the gas fuel is confirmed by the fuel switching confirmation means. When calculating the fuel supply amount related to the gas fuel supplied immediately after the switching, the fuel supply related to the gas fuel supplied before the completion of the switching is calculated based on the liquid fuel supply delay time constant related to the liquid fuel. By calculating the amount, the influence of the liquid fuel adhering to the intake passage as a wall flow is considered.

Further, when the cooling water temperature detected by the engine operating state detecting means is lower than the predetermined temperature, the gas fuel supply control is carried out so that the operating condition in the low temperature range where the vaporization of the liquid fuel is not good, Gaseous fuel with good vaporization is supplied. In addition, by performing duty control with a fine cycle width at the time of starting and in the operation area below the medium load area, and performing a duty control with a large cycle width in the high load area, the control cycle of the duty control becomes longer, O of the duty control valve by duty control
The number of times of N / OFF is reduced, so that the life of the duty control valve can be extended.

Further, after the completion of the fuel switching is confirmed by the fuel switching confirmation means, the ignition timing and the exhaust gas recirculation rate corresponding to the fuel after the switching are set, so that the combustion is stabilized and the emission is good. Become.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.
It In FIG. 4 showing the configuration of one embodiment, the intake air of the engine 11
Intake air flow rate Q in passage 12 _airAir flow sensor that detects
Intake air flow rate in conjunction with the motor 13 and accelerator pedal
Q_airA throttle valve 14 for controlling the
Electromagnetic components that make up the liquid fuel supply device for each cylinder
Type fuel injection valve 15 is provided.

The fuel injection valve 15 is driven to open by an injection pulse signal from a control unit 16 having a built-in microcomputer, is fed from a fuel pump (not shown) under pressure, and is gasoline as liquid fuel controlled to a predetermined pressure by a pressure regulator. Fuel is supplied by injection. Further, a water temperature sensor 17 for detecting the cooling water temperature Tw in the cooling jacket of the engine 11 is provided, and an air-fuel ratio sensor 19 for detecting the air-fuel ratio of the intake air-fuel mixture by detecting the oxygen concentration in the exhaust gas of the exhaust passage 18. And a three-way catalyst 20 that purifies the exhaust gas by oxidizing CO and HC and reducing NO _X in the exhaust gas.

Further, a throttle sensor 23 for detecting the opening of the throttle valve 14 is attached. A crank angle sensor 21 is built in a distributor (not shown in FIG. 4), and the crank unit angle signal output from the crank angle sensor 21 in synchronization with the engine rotation is counted for a certain period of time or the crank reference angle is calculated. The engine speed N is detected by measuring the cycle of the angular signal.

That is, the air flow meter 13, the water temperature sensor 1
7, the throttle sensor 23 and the crank angle sensor 21 constitute an engine operating state detecting means. An ignition signal is sent to the spark plug of the engine 11 by the ignition circuit 25, and the exhaust gas of the engine 11 is recirculated to the intake passage 12 by the EGR device 27. Furthermore, the engine 11 also includes a CNG fuel supply device 41 that supplies CNG fuel as a gas fuel, and has the configuration described below. That is, the CNG fuel is stored in the CNG fuel tank 42, but the CNG fuel tank 42 stores the CN.
An on-off valve 43 for opening and closing the supply of CNG fuel from the G fuel tank 42 is provided, and the CNG in the CNG fuel tank 42 is provided.
The heat exchanger 44 that absorbs heat for warming the fuel is the intake passage
It is arranged in 12.

The CNG fuel tank 42 is connected to the gas supply passage 45 communicating with the engine 11 from the CNG fuel tank 42.
A pressure sensor 46 for detecting the supply pressure from the CNG fuel tank 42, a safety valve 47 for opening the CNG fuel to the atmosphere to prevent damage to the engine 11 when the supply pressure from the CNG fuel tank 42 exceeds a predetermined pressure, approximately 200 kg / cm 2. A decompression device 48 for decompressing the CNG fuel pressure in the CNG fuel tank 42, which is a pressure of ^{3 to} a pressure of 2 kg / cm ³ , is provided in the order described above.

Further, the gas supply passage 45 on the downstream side of the decompression device 48 is branched, and a sonic valve unit 50 for adjusting the basic flow rate as shown in FIG. 5 is interposed in the branched portion. The basic flow rate adjusting sonic valve unit 50 has, for example, six types of duty control sonic valves 51, 52, ... 56 (hereinafter referred to as sonic valves 51, 52, ... Therefore, the flow rate can be controlled over various types by controlling the duty of each sonic valve. In this embodiment, the sonic valve 52 has twice the full-flow capacity as the sonic valve 51.
The flow rate of the sonic valve 53 is set to 2 ² = 4 times that of the sonic valve 51, and the sonic valve 54 is set to 2 ³ = 8 times that of the sonic valve 51.

The basic flow rate adjusting sonic valve unit 50 is driven by the drive unit 60. Further, a manifold (division pipe) 49 for supplying the gas fuel whose flow rate is controlled by the basic flow rate adjusting sonic valve unit 50 is provided for each cylinder in the downstream manifold portion after the merging of the branch portions. There is.

Sonic valve unit 50 for basic flow rate adjustment
Is opened by driving the drive unit 60 with the injection pulse signal from the control unit 16 described above, and injects the CNG fuel supplied from the CNG fuel tank 42 into the engine 11. Further, the control unit 16 stores a ROM _g that stores an ignition timing map, an exhaust gas recirculation amount setting map, a basic air-fuel mixture map, etc. for performing the control and various controls for gasoline fuel and various controls for CNG fuel described later. 57, a ROM _CNG 58 and a microcomputer unit (CPU _{g + CNG} ) 59 for performing the control are provided.

In the fuel supply system having the above construction, first, the control (gas fuel supply amount control means according to the present invention) performed by the control unit 16 as a control system for supplying only the CNG fuel to the engine 11 will be described. This will be described with reference to the flowchart shown in FIG. FIG. 6 shows a CNG basic control routine, and the execution cycle of this routine is also controlled by the control unit 16.

In step 1 (denoted as S1 in the figure, the same applies hereinafter), the on-off valve 43 is opened and the CNG fuel tank 42 to C are opened.
Start supplying NG fuel. In step 2, the pressure sensor 46 detects the supply pressure from the CNG fuel tank 42, and in step 3, it is determined whether the residual pressure in the CNG fuel tank 42 is equal to or higher than a predetermined pressure.

In step 3, the CNG fuel tank 42
If it is determined that the residual pressure of the above is not higher than the predetermined pressure, the process proceeds to step 14, the on-off valve 43 is closed because there is no CNG fuel as fuel, and an alarm is issued to notify the driver of the gas supply stop. Then, it progresses to step 15 and stops operation by CNG fuel. When it is determined in step 3 that the residual pressure in the CNG fuel tank 42 is equal to or higher than the predetermined pressure, the process proceeds to step 4 and below to operate the engine 11 with CNG fuel. First, in step 4, communication with the safety valve 47 is performed. When the supply pressure from the CNG fuel tank 42 becomes equal to or higher than a predetermined pressure, the CNG fuel can be opened to the atmosphere and damage to the engine 11 is prevented.

In step 5, the air flow meter 13
The intake air flow rate Q _air is detected by
The engine rotation speed N is detected by the detection signal from 21, and the cooling water temperature Tw of the engine 11 is detected by the water temperature sensor 17. In step 6, the basic fuel flow rate _Qf0 is calculated according to the following equation. Q _f0 = k × Q _air / N + Qt + Qr where Qt is the corrected fuel flow rate related to the cooling water temperature Tw of the engine 11, and Qr is the load correction amount in the high load region when the throttle valve 14 is fully opened.

Further, in step 6, in order to obtain the basic fuel flow rate Q _f0 , six kinds of sonic valves 51,
Determine how to control the duty of 52, ... 56. Here, duty control of the sonic valves 51, 52, ... 56 will be described with reference to FIGS. 7, 8 and 9.

In the present embodiment, each duty ratio is determined with reference to the allocation map that has been allocated in advance. In this embodiment, the cylinder to which fuel is supplied is 720 °.
It is determined for each CA (crank angle) signal, and the duty control is performed at an angle of 180 ° CA or less depending on operating conditions. That is, during the minimum flow rate during idle operation or the like, duty control is performed in a fine cycle to ensure sufficient control responsiveness. Further, at the time of maximum flow rate such as high speed full load, duty control is performed at a large cycle to prevent transient movement of the sonic valves 51, 52, ... 56 due to the duty control to extend the life.

Here, how to control each sonic valve in order to specifically obtain a predetermined flow rate will be described. As shown in FIG. 7, for example, the required basic fuel flow rate Q _f0 is 23 m.
If it is ³ / h, the sonic valve 56 (fully open flow rate 32 m ³ / h) is fully closed Sonic valve 55 (fully open flow rate 16 m ³ / h) is fully open Sonic valve 54 (fully open flow rate 8 m ³ / h) is duty ratio 50% Sonic valve 53 (fully open flow rate 4 m ³ / h) has a duty ratio of 50% Sonic valve 52 (fully open flow rate 2 m ³ / h) has a duty ratio of 50%, and sonic valve 51 (fully open flow rate 1 m ³ / h)
Controls each valve by performing fine adjustment by feedback control (described later).

Further, for example, the required basic fuel flow rate Q _f0 is 45 m.
Even when it is ³ / h, as shown in FIG. 8, it is possible to obtain a desired fuel flow rate by controlling the opening of the sonic valves 56, 55, 51. In the present embodiment, the sonic valve 52 has twice the full-flow capacity as the sonic valve 51, and the sonic valve 53 has four times the sonic valve 51.
The sonic valve 54 has eight times the sonic valve 51, and the flow rate of each sonic valve is set.
By using them in combination as shown in FIG. 9, it becomes possible to configure the basic flow rate adjusting sonic valve unit 50 having a wide dynamic range.

Further, the duty control of the basic flow rate adjusting sonic valve unit 50 with respect to the required basic fuel flow rate Q _f0 is stored as a map in the ROM and can be easily controlled by a table lookup operation. Here, the description returns to FIG. Therefore, in step 6, in order to obtain the basic fuel flow rate Q _f0 , the duty ratios of the six types of sonic valves 51, 52, ... 56 are searched from the map and set as shown in the following equation. .

Q _f1 = Q _f0 Q _f1 = V ₅₁ D ₅₁ + V ₅₂ D ₅₂ + V ₅₃ D ₅₃ + V ₅₄ D ₅₄ + V ₅₅
D ₅₅ + V ₅₆ D ₅₆ However, V _n, etc. is the fully open flow rate of the sonic valve n, and D
_{n and the} like are duty ratios of the sonic valve n. Next, at step 8, the air-fuel ratio sensor 19 detects the oxygen concentration in the exhaust gas to detect the air-fuel ratio of the intake air-fuel mixture, and a feedback correction coefficient DeltaA / F set by another routine based on the detected air-fuel ratio. Read in. Here, the feedback control is a sonic valve having a minimum flow rate.
Corresponding to the duty ratio of 51 being continuously changed in a specific short cycle, the final gas fuel flow rate Q _f2 is determined according to the following equation. (Step 9).

Q _f2 = Q _f1 × Delta A / F In step 10, the calculated final gas fuel flow rate Q _f2
Is set in the output register. As a result, when the gas fuel supply timing of the predetermined engine rotation cycle is reached, the drive pulse signal having the calculated pulse width of the gas fuel flow rate Q _f2 is sent by the drive unit 60 to each sonic valve unit 50 for adjusting basic flow rate. Valve 51 ~
Given to 56, the fuel is supplied.

Next, at step 11, the ignition timing ADV,
The optimum exhaust gas recirculation rate and the like are read from the ignition timing map 26, the EGR rate allocation map 29, etc. according to the operating conditions, and are output to the ignition circuit 25 and the EGR device 27 to control the ignition timing and the exhaust gas recirculation, respectively. Then, in step 12, it is determined whether or not to continue the above control. In the present embodiment, the duty control of the basic flow rate adjusting sonic valve unit 50 is performed for all of the sonic valves 51 to 56 as described above.
Even if 56, 55, 54 and 53 are ON / OFF controlled and only the sonic valves 52 and 51 are duty-controlled, the control logic is the same and contributes to cost reduction.

Further, in this embodiment, as shown in FIGS. 7 and 8, the sonic valves 51 to 56, which have the maximum flow rate when the basic flow rate is determined, are fully opened (always ON) and occupy the entire flow rate. The amount of bias is fixed to a large extent to suppress fluctuations in fuel flow rate. Furthermore, for that purpose, a sonic valve with a smaller flow rate (for example, sonic valve 51,
52, 53, etc.) are combined so that they are closed when the sonic valve with a large flow rate is open, and open when the sonic valve with a large flow rate is closed, in a so-called opposite phase. Are controlled. That is, when duty-controlling a plurality of sonic valves 51 to 56 having different valve opening flow rates, the total flow rate of all the sonic valves in the open state is substantially constant over time (for example, 23 m ³ / h in FIG. 7,
In FIG. 8, the duty control phases of the sonic valves 51 to 56 are set so as to be maintained at 45 m ³ / h). As a result, the fuel flow rate fluctuation (pulsation) of the gas fuel after passing through the basic flow rate adjusting sonic valve unit 50 can be prevented.

By controlling in this way, the final gas fuel flow rate Q _f2 is output as shown in FIG. 10. In this embodiment, in order to obtain the gas fuel flow rate of 23 m ³ / h,
Sonic valve 55 should be fully open and sonic valve 54 should be 180
The CA is opened for each CA, the sonic valves 53 and 52 are opened for the CA in which the sonic valve 54 is closed, and the sonic valve 51 is finely adjusted by feedback control. As a result, the flow rate fluctuation range is ± 1 m ³ / h,
The flow rate fluctuation rate is as small as ± 4%, which shows that the controllability is improved.

Next, in the fuel supply device having the above-mentioned structure,
The control performed by the control unit 16 as a control device that switches between CNG fuel and gasoline fuel and supplies it to the engine 11 will be described with reference to a flowchart. First, the control when the CNG fuel or the gasoline fuel is manually switched and supplied independently will be described with reference to the flowchart shown in FIG.

In step 41, the on-off valve 43 is opened to set CNG.
The supply of CNG fuel from the fuel tank 42 is started. In step 42, the pressure sensor 46 detects the supply pressure from the CNG fuel tank 42. In step 43, the ignition timing ADV is read from the ignition timing map 61 according to the operating conditions.

In step 45, it is determined whether the engine 11 is operating. In step 46, it is determined whether the CNG fuel supply or the gasoline fuel supply is switched by the manual switching operation. In the following description, in order to clarify the description, the description will be given separately for various operating conditions.

First, the case where the CNG fuel supply state is switched by the manual switching operation in step 46 will be described. In this case, the process proceeds to step 47. In step 47, the pressure sensor 46 detects the supply pressure from the CNG fuel tank 42, and
The residual pressure of the fuel is confirmed, and it is determined whether or not to supply the CNG fuel as it is. When the residual pressure of the CNG fuel is confirmed, it is determined that the CNG fuel is continuously supplied as it is, and the process proceeds to step 48.

In step 48, the control unit 16
The injection pulse signal from the drive unit 60 drives the drive unit 60 to adjust the basic flow rate of the sonic valve unit.
Since the valve 50 is driven to open and the CNG fuel supplied from the CNG fuel tank 42 is injected and supplied to the engine 11, it is determined whether or not the drive unit 60 is maintained in the ON state.

In step 49, the above-mentioned CNG basic control routine described with reference to FIG. 6 is executed, and injection supply of CNG fuel to the engine 11, ignition timing control, and exhaust gas recirculation control are executed. In step 50, it is determined whether the operation of the engine 11 is stopped, and if the operation is continued without being stopped, the process returns to step 41.

Next, description will be made of the case where the gasoline fuel supply state is switched by the manual switching operation in step 46. In this case, the process proceeds to step 51. In step 51, it is judged whether or not the injection pulse signal from the control unit 16 is maintained in the ON state to drive the fuel injection valve 15 to open. In step 52,
Similar to the conventional fuel supply device for a gasoline fuel engine, injection supply of gasoline fuel to the engine 11, ignition timing control, and exhaust gas recirculation control are executed.

In step 50, it is judged whether the operation of the engine 11 is stopped, and if the operation is continued without being stopped, the process returns to step 41. Next, the control when the switching operation is performed from the CNG fuel supply to the gasoline fuel supply or from the gasoline fuel supply to the CNG fuel supply by the manual switching operation will be described with reference to the flowcharts shown in FIGS. 12 and 13. . It should be noted that steps having the same effects as those of the routine shown in FIG. 11 are denoted by the same step numbers and description thereof is omitted.

First, the case where the switching operation from the CNG fuel supply state to the gasoline fuel supply state is performed by the manual switching operation in step 46 will be described with reference to FIG. In this case, in step 51, it is judged whether the injection pulse signal from the control unit 16 has been switched from the OFF state to the ON state in order to drive the fuel injection valve 15 to open, and the switching control is performed to the ON state. If it is determined that the result is yes, the process proceeds to step 61.

Even after the switching operation from the CNG fuel supply state to the gasoline fuel supply state is performed, C is present in the passage downstream of the safety valve 47 provided in the gas supply passage 45 to the engine 11.
The NG fuel remains, and the residual CNG fuel is supplied to the engine 11 as it is. Therefore, first in step 61,
The residual CNG fuel amount QfcT is calculated. That is, a time constant Tau (represented by a damping function) for consuming the residual CNG fuel is determined by a map or calculation for each final flow rate Qfc1 _Final in the CNG fuel supply state immediately before switching, and this is designated as QfcT. .

QfcT = Qfc1 _Final × Tau In step 62, the basic gasoline fuel supply amount QfgT1 is calculated. Therefore, first, the required gasoline fuel amount Qfg1 at the start of the gasoline fuel supply is calculated. Immediately after the switching operation is performed to the gasoline fuel supply state, there is no wall flow in the downstream manifold portion where the fuel injection valve 15 is provided, and immediately after the switching operation, the fuel that adheres to the manifold portion as the wall flow Exists. Here, the time constant Taug1 for the fuel to adhere as a wall flow is determined by a map or calculation for each required amount Qfg1 in the gasoline fuel supply state. Therefore, the required gasoline fuel amount at the start of the gasoline fuel supply is Qfg1 × (1 + Taug1).

As a result, the basic gasoline fuel supply amount Qfg
T1 is the amount obtained by subtracting the residual CNG fuel QfcT and adding the wall flow, and is as shown below. QfgT1 = Qfg1 × (1 + Taug1) −QfcT = Qfg1 × (1 + Taug1) −Qfc1 _Final × Tau Here, even during the switching operation from the CNG fuel supply state to the gasoline fuel supply state, the air-fuel ratio feedback by the air-fuel ratio sensor 19 is performed. Correction is done. Therefore, step 63
Then, the feedback correction coefficient DeltaA / F set based on the detected air-fuel ratio by another routine is read. As a result, the final gasoline fuel supply amount QfgT2 is determined according to the following equation. (Step 64).

QfgT2 = QfgT1 × DeltaA / F That is, steps 61, 62 and 64 function as a mixed fuel supply amount setting means. In step 65, it is determined whether or not the residual CNG fuel amount QfcT calculated in step 61 has been consumed. That is, since the time constant Tau is represented by an attenuation function, the value of Tau is gradually reduced, and therefore it is determined whether or not the switching is completed by determining whether or not QfcT = 0. It becomes possible to judge whether or not.

That is, steps 61 and 65 function as fuel switching confirmation means. Here, if it is determined that the switching is completed (YES), the process proceeds to step 66, where the fuel supply control related to the switching operation from the CNG fuel supply state to the gasoline fuel supply state is stopped, and the gasoline fuel supply state is stopped. And That is, in step 67, the on-off valve 43 is closed, or after issuing an alarm notifying the driver that the supply of gas has stopped, the routine proceeds to step 68, where communication with the safety valve 47 is closed.

In step 69, the drive unit 60, which has been in the ON state for opening and driving the basic flow rate adjusting sonic valve unit 50, is brought into the OFF state and the operation is stopped. That is, step 69 functions as the operation stopping means. Then, the process proceeds to step 52 and thereafter.

On the other hand, if it is determined in step 65 that the switching has not been completed, the routine proceeds to step 70, where the ignition timing AD
V, the optimum exhaust gas recirculation rate, etc. are read from the ignition timing map 61, the EGR rate allocation map 62, etc. according to the operating conditions, and the ignition timing and exhaust gas recirculation are respectively corrected. That is, step 70 functions as the ignition timing setting means and the exhaust gas recirculation rate setting means.

Next, a case where the switching operation from the gasoline fuel supply state to the CNG fuel supply state is performed by the manual switching operation in step 46 will be described with reference to FIG. In step 47, the pressure sensor 46 detects the supply pressure from the CNG fuel tank 42 to confirm the residual pressure of the CNG fuel, and determines whether or not the CNG fuel can be supplied as it is. And CN
When the residual pressure of the G fuel is confirmed, it is possible to switch to the CNG fuel as it is, and the routine proceeds to step 71. That is, in step 71, after the fuel switching request, it is confirmed whether or not the fuel switching conditions are satisfied, and then the fuel switching is performed.

At step 71, it is judged whether the drive unit 60 for opening and driving the basic flow rate adjusting sonic valve unit 50 is switched from the OFF state to the ON state, and it is judged that the switching control is performed to the ON state. Then, the process proceeds to step 72. From gasoline fuel supply state to CN
Even after the switching operation to the G fuel supply state is performed, the fuel injection valve
The attached wall flow fuel remains in the downstream manifold portion where 15 is provided, and the residual gasoline fuel is directly supplied to the engine 11. Therefore, first in step 72,
The residual gasoline fuel amount QfgT is calculated.

That is, the time constant Taug2 (represented by a damping function) for consuming the residual gasoline fuel is determined by a map or calculation for each final flow rate Qfg1 _Final in the CNG fuel supply state immediately before switching, and this is determined. QfgT. QfgT = Qfg1 _Final × Taug2 In step 73, the basic CNG fuel supply amount QfcT1 is calculated. Here, immediately after the switching operation to the CNG fuel supply state is performed, there is almost no control delay or the like regarding the CNG fuel supply, so the basic CNG fuel supply amount QfcT1 is
The residual gasoline fuel amount QfgT is subtracted from the initial injection amount Qfc1 of the CNG fuel, as shown below.

QfgT1 = Qfc1−QfgT = Qfc1−Qfg1 _Final × Tau Here, the air-fuel ratio feedback correction by the air-fuel ratio sensor 19 is performed even during the switching operation from the gasoline fuel supply state to the CNG fuel supply state. Therefore, step 74
Then, the feedback correction coefficient DeltaA / F set based on the detected air-fuel ratio by another routine is read. As a result, the final CNG fuel supply amount QfcT2 is determined according to the following equation. (Step 75).

QfcT2 = QfcT1 × DeltaA / F That is, steps 72, 73 and 75 perform the function of the mixed fuel supply amount setting means. In step 76, it is determined whether or not the residual gasoline fuel amount QfgT calculated in step 72 has been consumed. That is, since the time constant Taug2 is represented by a damping function, the value of the Taug2 is gradually reduced, and it is determined whether or not the switching is completed by determining whether or not QfgT = 0. It becomes possible to judge whether or not.

That is, steps 72 and 76 function as fuel switching confirmation means. Here, if it is determined that the switching is completed (YES), the process proceeds to step 77, the fuel supply control related to the switching operation from the gasoline fuel supply state to the CNG fuel supply state is stopped, and the CNG fuel supply state is stopped. And That is, in step 78, it is confirmed that communication with the safety valve 47 is open, damage to the engine 11 is prevented, and then the process proceeds to step 79, in which the operation of the fuel injection valve 15 for supplying gasoline fuel is stopped.

That is, step 79 has the function of the operation stopping means. Then, the process proceeds to step 49 and thereafter. On the other hand, if it is determined in step 76 that the switching has not been completed,
In step 70, the ignition timing ADV, the optimal exhaust gas recirculation rate, etc. are read from the ignition timing map 61, the EGR rate allocation map 62, etc., according to the operating conditions, and the ignition timing and exhaust gas recirculation are respectively corrected.

That is, step 70 functions as an ignition timing setting means and an exhaust gas recirculation rate setting means. Next, as another embodiment, the CN is operated by automatically switching the fuel.
Control when switching from G fuel supply to gasoline fuel supply or from gasoline fuel supply to CNG fuel supply will be described. Here, the operation different from the flowcharts shown in FIGS. 11 to 13 is performed in step 46.
Since it is only the step of the switching determination related to the manual switching operation in the above, the description of the other steps will be omitted.

Here, the conditions for making the fuel switching determination include whether the output is high, whether it is necessary to reduce exhaust gas, and whether it is necessary to improve fuel efficiency. There is. That is, as to whether or not the output is high, it is determined whether or not the throttle valve 14 is fully open or near full opening, and in that case, CNG fuel is supplied. Regarding whether or not it is necessary to reduce the exhaust gas, CNG fuel is supplied when the catalyst 20 has not reached the activation temperature. Also,
Regarding whether it is necessary to improve fuel efficiency,
When the residual pressure of the CNG fuel is confirmed by the pressure sensor 46, C
Supply NG fuel.

Further, the control unit switches the fuel supply control for each operation area as shown in FIG. That is, in the low water temperature region, the CNG fuel vaporizes better than the gasoline fuel, so that the exhaust performance is improved as the CNG fuel supply control. Then, in the CNG fuel supply control, it is determined that the engine 11 is warming up until the water temperature rises to a predetermined temperature (generally 50 to 60 ° C.), and at the time of starting and restarting. And low,
When driving in urban areas in the medium load range, the above-mentioned air-fuel ratio feedback control is used to improve fuel efficiency and exhaust performance.

On the other hand, in a higher rotation range, that is, in a high load range, in order to improve the durability of the basic flow rate adjusting sonic valve unit 50, a large duty cycle is selected (eg 180 ° CA or less). By setting the duty control with 180 cycles as one cycle), the number of times of duty control is reduced,
Switch to rough CNG fuel supply control. At this time, even if the control cycle is set to 180 ° CA, the control cycle time is not long because it is in the high rotation range, and the control characteristics do not deteriorate.

That is, by adopting these two air-fuel ratio feedback controls, it is possible to reduce the number of combinations of a plurality of sonic valves constituting the basic flow rate adjusting sonic valve unit 50, and to realize a lower cost fuel supply device. I am trying. Further, if the CNG fuel supply control is continued at high rotation and high output, the gaseous fuel may diffuse in the intake system, and the volume efficiency of air intake may decrease, resulting in a decrease in output. The control is switched to the gasoline supply control to achieve higher output.

As described above, according to this embodiment,
With respect to the sonic valve having the minimum flow rate, the other sonic valve whose flow rate is set to 2 ⁿ is duty-controlled according to the engine operating state, so that the dynamic range can be expanded. In addition, the gas supply passage 45 to the engine 11
Remaining CNG fuel amount QfcT and fuel injection valve 15
In consideration of the residual gasoline fuel amount QfgT, etc. that adheres to the downstream manifold portion where is installed as a wall flow, the time constant Tau represented by an attenuation function for consuming the residual CNG fuel, and the residual CNG fuel are Since the time constant Tau represented by the damping function for consumption is used to eliminate the influence on the air-fuel ratio related to the residual fuel before switching at the time of fuel switching, the fuel control accuracy is high and good exhaust gas is obtained. It is possible to secure performance and drivability.

Further, in the fuel supply device for the gas / liquid fuel engine according to the present embodiment, the control sensors can be shared in common, and the cost increase can be suppressed.

[0081]

As described above, according to the present invention,
The solenoid valve with the minimum flow rate is configured to control the duty of multiple solenoid valves whose flow rate is set to 2 ⁿ according to the operating conditions, so the response is good and the flow rate range is wide. It is possible to provide a gas fuel supply device having the above, and it is possible to provide engine control with high fuel control accuracy and a wide dynamic range at low cost.

Further, the control device for the internal combustion engine is configured to include fuel switching means for switching the fuel supplied to the engine to the gas fuel or the liquid fuel according to the engine operating state, and further, the fuel switching means is adapted to supply the fuel. In the fuel system before switching, after shutting off the supply of the fuel supply source on the upstream side, it is confirmed that the residual fuel is completely supplied from the fuel supply source to the fuel supply unit for directly supplying fuel to the engine on the downstream side. The fuel switching confirmation means for confirming and the operation stopping means for stopping the operation of the fuel supply unit after confirming the completion of the fuel switching are provided, and the fuel system after the fuel supply switching is supplied immediately before the fuel switching by the fuel switching confirmation means. The fuel system before the switching is completed before the completion of the switching based on the fuel supply amount of the fuel that has been stored and the set fuel supply amount when only the fuel after the switching is supplied according to the operating state immediately after the completion of the switching. Since it is configured to include the mixed fuel supply amount setting means for setting the fuel supply amount of the switched fuel supplied together with the residual fuel, it becomes possible to secure good exhaust performance and operability. By using two kinds of fuels, it is possible to make the most of the advantage of operating with each fuel and to achieve low fuel consumption, improved exhaust performance, and high output as a vehicle by automatic switching of fuel selection.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration according to claim 1 of the present invention.

FIG. 2 is a block diagram showing a configuration according to claim 5 of the present invention.

FIG. 3 is a flow chart illustrating an operation according to claim 5 of the present invention.

FIG. 4 is a system configuration diagram showing the configuration of an embodiment of the present invention.

FIG. 5 is a system configuration diagram showing the configuration of a basic flow rate adjusting sonic valve unit in the embodiment.

FIG. 6 is a flowchart showing the contents of control performed by the control unit in the above embodiment.

FIG. 7 is a time chart explaining the operation of the basic flow rate adjusting sonic valve unit in the embodiment.

FIG. 8 is a time chart explaining the operation of the basic flow rate adjusting sonic valve unit in the embodiment.

FIG. 9 is a characteristic diagram showing a combination of sonic valves of a basic flow rate adjusting sonic valve unit in the embodiment.

FIG. 10 is a time chart showing the flow characteristics of the gas fuel flow rate in the above embodiment.

FIG. 11 is a flowchart showing the contents of control performed by the control unit in the above embodiment.

FIG. 12 is a flowchart showing the contents of control performed by the control unit in the above embodiment.

FIG. 13 is a flowchart showing the contents of control performed by the control unit in the above embodiment.

[Fig. 14] Fig. 14 is a characteristic diagram showing the control content for each operating state performed by the control unit in the above embodiment.

[Explanation of symbols]

 11 Engine 12 Intake passage 13 Air flow meter 16 Control unit 21 Crank angle sensor 41 CNG fuel supply device 42 CNG fuel tank 45 Gas supply passage 47 Safety valve 48 Pressure reducing device 50 Basic flow rate adjusting sonic valve unit 51 Duty control sonic valve 52 Duty control sonic Valve 53 Duty control sonic valve 54 Duty control sonic valve 55 Duty control sonic valve 56 Duty control sonic valve 60 Drive unit

Claims (13)

[Claims] 1. A plurality of pressure adjusting units for adjusting the gas fuel pressure and a plurality of branch passages formed by branching on the downstream side of the pressure adjusting units, each of which opens a predetermined constant flow rate by opening a valve. A gas fuel supply device including: a flow rate adjusting unit including individual solenoid valves; and a multi-tracheal pipe that guides gas fuel formed in a gas passage after the branch passages are joined to each cylinder. An engine operating state detecting means for detecting a state; and a gas fuel supply amount controlling means for controlling opening and closing of the plurality of solenoid valves according to the engine operating state to control a gas fuel supply amount. A control device for an internal combustion engine, comprising: 2. The internal combustion engine according to claim 1, wherein among the plurality of electromagnetic valves for adjusting the gas fuel flow rate, at least the small flow rate adjusting solenoid valve performs duty control at a predetermined control cycle. Control device. 3. The plurality of solenoid valves have different flow rates n.
3. The internal combustion engine according to claim 1 or 2, further comprising a plurality of solenoid valves, and the flow rate of another solenoid valve is set to 2 ⁿ with respect to a solenoid valve having a minimum flow rate among the n solenoid valves. Engine control unit. 4. A plurality of solenoid valves having different valve opening flow rates are duty-controlled, and duty control of each solenoid valve is performed so that the total flow rate of all the solenoid valves in the open state is kept substantially constant over time. The phase is set, and any one of claims 1 to 3 is provided.
Of the internal combustion engine according to item 6. 5. A liquid fuel supply apparatus for supplying liquid fuel to each cylinder, the liquid fuel supply apparatus comprising the gas fuel supply apparatus, an engine operating state detecting means and a gas fuel supply amount control means, and the liquid fuel according to the engine operating state. A liquid fuel supply amount control means for controlling the supply amount, and a fuel switching means for switching the fuel to be supplied to the engine to a gas fuel or a liquid fuel according to the engine operating state. The control device for an internal combustion engine according to any one of 1 to 4. 6. The control device for the internal combustion engine according to claim 5, wherein the fuel switching means performs the fuel switching after confirming that the fuel switching conditions are satisfied after the fuel switching request. . 7. A fuel supply unit for supplying fuel directly from the fuel supply source to a downstream engine in the fuel system before switching the fuel supply after shutting off the supply of the fuel supply source on the upstream side. Fuel switching confirmation means for confirming that the remaining fuel has been completely supplied, and operation stopping means for stopping the operation of the fuel supply part after confirmation of the completion of the fuel switching. Based on the fuel supply amount of the fuel supplied immediately before the fuel switching by the fuel switching confirmation means and the set fuel supply amount when only the fuel after switching is supplied according to the operating state immediately after the completion of the switching, 6. A mixed fuel supply amount setting means for setting the fuel supply amount of the fuel after switching, which is supplied together with the residual fuel in the fuel system before switching before the switching is completed. Or 6
A control device for an internal combustion engine according to. 8. The fuel switching confirmation means confirms completion of switching from gas fuel to liquid fuel based on a gas fuel supply delay time constant related to gas fuel, and the fuel switching confirmation means switches from gas fuel to liquid fuel. When the fuel supply amount related to the liquid fuel to be supplied immediately after the switching is confirmed after the switching is confirmed, the gas fuel supply delay time constant related to the gas fuel and the liquid fuel supply delay time constant related to the liquid fuel are calculated. The internal combustion engine according to any one of claims 5 to 7, wherein the fuel supply amount of the liquid fuel supplied together with the residual fuel of the gas fuel system before the completion of the switching is set based on Control device. 9. The fuel switching confirmation means confirms completion of switching from liquid fuel to gas fuel based on a liquid fuel supply delay time constant relating to liquid fuel, and the fuel switching confirmation means switches from liquid fuel to gas fuel. When the fuel supply amount related to the gas fuel supplied immediately after the switching is confirmed after the switching is confirmed, the liquid fuel is supplied before the switching is completed based on the liquid fuel supply delay time constant related to the liquid fuel. The control device for an internal combustion engine according to any one of claims 5 to 7, wherein a fuel supply amount related to a gas fuel supplied together with the residual fuel of the system is set. 10. When the operating state detected by the engine operating state detecting means is an operating state in which the cooling water temperature is lower than a predetermined temperature, the gas fuel supply control is performed, and at the time of starting and during the gas fuel supply control. The internal combustion engine according to any one of claims 5 to 9, wherein duty control is performed with a fine cycle width in an operation area below a load area, and duty control with a large cycle width is performed in a high load area. Control device. 11. The ignition timing setting means for setting an ignition timing based on the engine operating state after the completion of fuel switching is confirmed by the fuel switching confirmation means. 11. The control device for an internal combustion engine according to any one of 10. 12. The exhaust gas recirculation rate setting means for setting an exhaust gas recirculation rate based on the engine operating state after the fuel switch confirmation means confirms the completion of fuel switching. The control device for an internal combustion engine according to any one of 5 to 10. 13. The control device for an internal combustion engine according to claim 1, wherein the gas fuel is CNG fuel and the liquid fuel is gasoline fuel.