JPH0799114B2 - Engine controller - Google Patents

Description

The present invention relates to a fuel injection control of an engine having a fuel injection valve for directly injecting fuel into a cylinder and a fuel injection valve for injecting fuel into an intake passage. It relates to the device.

[Prior Art] Since the fuel injection valve can accurately control the fuel supply amount, it is often the case that the fuel is supplied to the engine by using the fuel injection valve and the fuel control such as the air-fuel ratio control can be performed more precisely. Are known. As one of fuel supply methods using a fuel injection valve, a fuel injection valve is provided so as to directly face a combustion chamber or an operation chamber, and fuel is directly injected into the combustion chamber or the operation chamber, so-called direct injection. A method has been proposed (see, for example, Japanese Patent Laid-Open No. 58-56117). In such a direct injection system, the fuel distribution in the combustion chamber or working chamber can be unevenly distributed by adjusting the position, direction, injection timing, etc. of the fuel injection valve. There is an advantage that a so-called intake air stratification can be performed in which a rich air-fuel mixture layer is formed around the spark plug in order to improve the combustibility of the.

However, such uneven distribution of the fuel distribution in the combustion chamber or the working chamber lowers the air utilization rate (the ratio of the air used for combustion of fuel to the air in all the intake air) at the time of high load, resulting in a reduction in output. There was a problem. Therefore, a second fuel injection valve is provided in the intake passage so that the second fuel injection valve
Fuel is injected from the fuel injection valve to the intake air in the intake passage (manifold injection) to uniformly mix the intake air and the fuel to increase the air utilization rate, improve the combustibility at low load and increase the air flow at high load. It has been proposed that it is compatible with the improvement of the utilization rate.

However, in the conventional one provided with such a first fuel injection valve and second fuel injection valve, when switching from direct injection at low load to manifold injection at high load,
Due to the difference in air utilization rate, there is a step difference in torque.
There is a problem that torque switching occurs and switching cannot be performed smoothly.

[Object of the Invention] The present invention has been made in view of the above-mentioned conventional problems, and in an engine configured to perform direct injection at low load and perform manifold injection at high load,
An object of the present invention is to provide an engine control device capable of effectively preventing the occurrence of torque shock when switching from direct injection to manifold injection and performing smooth switching.

In order to achieve the above object, the present invention has a first fuel injection valve that directly injects fuel into the cylinder, a second fuel injection valve that injects fuel into the intake passage, and a second fuel injection valve when the load is low. 2 The fuel injection from the fuel injection valve is stopped and the intake air amount control is substantially stopped, and the fuel injection amount of the first fuel injection valve is controlled to perform the output control, while the first fuel injection valve is operated at the time of high load. From the low-load side control and output control means for controlling the fuel injection amount of the second fuel injection valve to maintain the intake air at a predetermined air-fuel ratio and performing output control by the intake air amount control. At the time of switching to the load side control, after making the air-fuel ratio substantially equal to the predetermined air-fuel ratio by the intake air amount control, the fuel injection from the first fuel injection valve is stopped and the fuel injection from the second fuel injection valve is performed. Switching control means for controlling A control device for an engine is provided.

EFFECTS OF THE INVENTION According to the present invention, when the direct injection is performed in a state where the intake air is not substantially throttled to the manifold injection in which the intake air amount is controlled, the intake air amount is controlled while the direct injection is performed. After the control is started, the air-fuel ratio during direct injection is adjusted to be approximately the same as the predetermined air-fuel ratio (for example, excess air ratio λ = 1) during high-load side control in which manifold injection is performed. Since the control is switched to the load side and the manifold injection is performed, the air-fuel ratio (excess air ratio) before and after the switching is almost the same, and the air utilization rate is also almost the same. Therefore, there is no torque step and there is no torque shock. It is possible to prevent the occurrence of, and to smoothly switch between direct injection and manifold injection. The excess air ratio λ is a value obtained by dividing the actual intake air amount by the air amount (theoretical air amount) necessary for combustion of fuel, and between this excess air ratio λ and the air-fuel ratio A / F, λ = (A / F) /14.7 (1
4.7 is the theoretical air-fuel ratio).

Further, by switching between direct injection and manifold injection at the excess air ratio λ = 1, load control during manifold injection can be performed by throttle control as in the conventional case, so that the control mechanism can be simplified.

[Embodiment] An embodiment of the present invention will be described below with respect to a rotary piston engine, but the present invention is not limited to this, and it goes without saying that the present invention can be applied to a reciprocating engine.

As shown in FIG. 1, the rotary piston engine RE is
In the casing 1, the rotor 2 makes a planetary rotational motion around the eccentric shaft 3 to suck the intake air or the air-fuel mixture into the working chamber 6 from the intake port 5 opening to the inner surface of the side housing 4 forming the side wall of the casing 1. , The mixture in the working chamber 6 is compressed by the rotor 2 and ignited and burned by the spark plug 7,
After that, a basic structure in which a series of strokes in which the combustion gas is discharged to the exhaust passage 11 through the exhaust port 9 opening to the inner peripheral surface of the rotor housing 8 forming the peripheral wall of the casing 1 is continuously repeated is provided.

An intake passage 12 is provided to supply intake air to the working chamber 6, and the intake passage 12 is provided with an air cleaner 13 for removing suspended dust in the intake air in order from the upstream side, and an air flow for detecting the amount of intake air every moment. In response to a signal applied from the meter 14 and a control circuit 15 described in detail later, a step motor
A throttle valve 17 driven and opened / closed by 16 and a second fuel injection valve 18 for injecting fuel into the intake air (manifold injection) in a predetermined load region (high load region), which will be described in detail later, are interposed. There is. The fuel in the fuel tank 19 is supplied to the second fuel injection valve 18 through a fuel supply passage 21 by a fuel pump 22 having a relatively low discharge pressure. Then, among the fuel supplied to the second fuel injection valve 18, the fuel not injected into the intake air is returned to the fuel tank 19 through the fuel return passage 23. In the fuel return passage 23, in the vicinity of the second fuel injection valve 18, in order to prevent the fuel injection amount from changing due to the change in the negative pressure in the intake passage 12, the fuel injection pressure of the second fuel injection valve 18 ( A pressure regulator 24 is provided to maintain the differential pressure between the pressure in the fuel return passage 23) and the pressure in the intake passage 12 at a predetermined constant value.

By the way, at a position on the trailing side of the ignition plug 7 of the rotor housing 8, fuel is directly injected into the working chamber 6 in a predetermined load region (a light load region excluding an extremely light load region) described in detail later. (Direct injection) The main nozzle 26 is inserted into a hole that is formed by penetrating through the rotor housing 8 while inclining slightly to the leading side from the thickness direction and opening in the inner surface of the rotor housing 8 while inclining slightly in the leading direction. On the other hand, a pilot nozzle 28 that directly injects fuel into the working chamber 6 in a predetermined load region (light load region) at a position on the rotor housing 8 that is slightly on the leading side of the ignition plug 7 is arranged on the rotor housing 8 side. The spark plug 7 is inserted into the inner surface of the rotor housing 8 so as to penetrate therethrough while inclining slightly to the trailing side from the thickness direction. The rotor housing 8 is fitted into a hole having a common opening with the hole of the rotor housing 8.
The main nozzle 26 and pilot nozzle 28
Corresponds to the first fuel injection valve described in the claims of the present application. And the main nozzle 26 and pilot nozzle
In order to supply fuel to the fuel supply path 28, a branched fuel supply path 31 is provided branching from a position slightly downstream of the fuel pump 22 in the fuel supply path 21, and the branched fuel supply path 31 further includes a main nozzle 26. Main nozzle passage 32 communicating with
And a pilot nozzle passage 33 communicating with the pilot nozzle 28. Fuel must be injected into the working chamber 6 from the main nozzle 26 and the pilot nozzle 28 during the high-pressure intake air in the compression stroke, but since the discharge pressure of the fuel pump 22 cannot inject the fuel into the working chamber 6. , Main nozzle passage 32 and pilot nozzle passage 33
A fuel pump 36 for a main nozzle and a fuel pump 37 for a pilot nozzle, which are mechanically driven by an output shaft 35 of the engine RE via a timing belt 34, are provided in each. The main nozzle fuel pump 36 and the pilot nozzle fuel pump 37 are, for example, plunger pumps, which are capable of periodically discharging fuel at a predetermined timing in synchronization with the rotation of the output shaft 35. . The fuel pump 36 for the main nozzle is connected to the control circuit 15
The discharge amount of each time is controlled according to the load amount, while the pilot nozzle fuel pump 37
Is set so that the discharge amount for each time is constant regardless of the magnitude of the load. Further, in the main nozzle passage 32 and the pilot nozzle passage 33, the main nozzle fuel pump 36 and the pilot nozzle fuel pump 37 downstream, respectively, in order to stop the fuel injection in a predetermined load region, The control circuit 15 controls the fuel discharged from the nozzle fuel pump 36 and the pilot nozzle fuel pump 37.
A relief valve 41 for the main nozzle and a relief valve 42 for the pilot nozzle are provided to relieve the branched fuel supply passage 31 through the relief passage 38 in response to the signal from the. The main nozzle 26 or pilot nozzle
The fuel not injected from 28 into the working chamber 6 is returned to the branch fuel supply passage 31 through the return passage 43.

By the way, the control circuit 15 is composed of a microcomputer, and the intake air amount Qa detected by the air flow meter 14 is measured.
And an oxygen concentration C (air-fuel ratio A / F is known) detected by an oxygen concentration meter 45 provided in the exhaust passage 11, and an engine speed N detected by a rotation speed sensor (not shown). , Accelerator pedal opening sensor (not shown)
Predetermined control such as intake air amount control, fuel supply amount control, direct injection / manifold injection switching control, ignition plug ignition timing control, etc. is performed by using the accelerator opening Ac detected by the input information. But,
Hereinafter, referring to the control flowchart shown in FIG.
A control method of the control circuit 15 will be described.

As shown in FIG. 2, when the control is started, first in step S1, the intake air amount Qa, the engine speed N, the accelerator opening Ac, and the oxygen concentration C in the exhaust gas are used as control information as a control circuit. It is read in 15 and the operating condition of the engine RE is grasped.

Next, in step S2, it is compared whether or not the cylinder (front or rear) of the engine RE is in the fuel injection range. In the present embodiment, when the engine RE is in the deceleration range represented by the region IV in FIG. 3, the fuel supply to one of the predetermined cylinders is stopped to activate the engine brake, and the load is further reduced. When the vehicle is in the strong deceleration range represented by the region V in FIG. 3, the fuel supply to both cylinders is stopped in order to exert stronger engine braking. Therefore, as a result of the comparison in step S2, the operating state of the cylinder corresponds to the region V in FIG. 3 or the region IV in FIG. 3 and the cylinder is in the fuel state when the one-sided cylinder fuel supply is stopped. If the cylinder is set to stop the supply, it is not in the fuel injection range (NO), so it is not necessary to perform fuel injection, and control is performed in step S1.
Go to 5. Then, in step S15, it is compared whether or not the ignition switch is on, and if it is on (YES), the engine RE continues to operate, and the control returns to step S1 and continues. On the other hand, if the ignition switch is off (NO), the operation of the engine RE is stopped and the control ends.

On the other hand, as a result of the comparison in step S2, the operating state of the cylinder concerned does not correspond to the region IV or the region V in FIG. 3, or corresponds to the region IV in FIG. In the case of the cylinder on the side set to supply fuel, the engine RE is in the fuel injection range (YES), so control is performed to perform fuel injection in step S3.
Proceeded to.

In step S3, it is compared whether or not the operating state of the engine RE is in the switching region from direct injection to manifold injection or from manifold injection to direct injection. Here, the operating state of the engine RE represents the boundary at which the intake amount control is started prior to the switching from the direct injection to the manifold injection, and the broken line A _{2 in} FIG.
And the broken line A ₁ that represents the boundary at which switching is performed from manifold injection to direct injection III
When it enters, it is determined that it is in the switching area. As a result of the comparison in step S3, when the operating state of the engine RE corresponds to the region III in FIG. 3, it is in the switching region (YES), so the control proceeds to step S4 to switch the fuel injection system. .

In step S4, it is compared whether or not the operating state of the engine RE in the switching region is switching from direct injection to manifold injection. This is performed by comparing whether the engine load W before entering the switching region is on the low rotation side or the low load side with respect to the broken line A _{2 in} FIG.
As a result of the comparison in step S4, before entering the switching area (previous time)
Is not direct injection (NO), the engine
Since the RE operating state corresponds to the case where the switching from the manifold injection to the direct injection should be performed, the control proceeds to step S8 to switch to the direct injection.

In step S8, the fuel injection from the second fuel injection valve 18 is stopped and the manifold injection is stopped (see FIG. 1). When the manifold injection is being performed, the main nozzle passage 32 is connected to the relief passage 38, and the fuel is branched through the relief passage 38 to the branch fuel supply passage 31.
The relief valve 41 for the main nozzle, which has been returned to the main nozzle 26, is switched to connect the main nozzle passage 32 to the main nozzle 26, and direct injection is performed from the main nozzle 26 into the working chamber 6 (FIG. 1). reference). As described above, the fuel injection amount from the main nozzle 26 is adjusted by controlling the discharge amount of the main nozzle fuel pump 36 according to the engine load (see FIG. 1). Similarly, the pilot nozzle relief valve 42 is switched to connect the pilot nozzle passage 33 to the pilot nozzle 28, and direct injection is also performed from the pilot nozzle 28 into the working chamber 6 (see FIG. 1). The fuel injection amount from the pilot nozzle 28 is constant regardless of the engine load. In this way, from manifold injection to direct injection (main nozzle + pilot nozzle)
After being switched to, the control is advanced to step S15, and the control is returned to step S1 and continued or terminated in accordance with ON / OFF of the ignition switch.

On the other hand, as a result of the comparison in step S4, when the direct injection is performed before entering the switching region (YES), the engine RE
Since the operating state of corresponds to the case where the switching from the direct injection to the manifold injection should be performed, the control proceeds to step S5 to switch to the manifold injection.

In step S5, when switching from direct injection to manifold injection, the throttle valve 17 is throttled and the intake amount is throttled in order to prevent a torque step difference from occurring due to a difference in the air utilization rate. Then, after the throttle of the intake air amount is started in step S5, the control proceeds to step S6.

In step S6, it is compared whether or not the excess air ratio (air-fuel ratio A / F) has dropped to a predetermined excess air ratio (air-fuel ratio A / F) during manifold injection, and the excess air ratio (air-fuel ratio A / F) is compared. If is not lower than the specified value (NO), the control is step
It is returned to S5, and the intake amount is further throttled. In this way, the intake amount is continuously throttled while direct injection is performed until the excess air ratio (air-fuel ratio A / F) reaches a predetermined value, and the excess air ratio (air-fuel ratio A / F) is almost the predetermined value. When (YES) is reached, control proceeds to step S7 to switch from direct injection to manifold injection. When direct injection is being performed at the time of light load, the throttle valve 17 is fully opened, and the throttle valve 17 is substantially in a state without throttling. As a result, pumping loss at light load is reduced and stratification of intake air is promoted.

Here, assuming that the intake air amount control in steps S5 and S6 is not performed and the direct injection is switched to the manifold injection at a predetermined load W ₃ (corresponding to the broken line A ₁ in FIG. 3), the air-fuel ratio A / F changes as shown by the straight line B ₅ in FIG. 4 (a), and when the direct injection is switched to the manifold injection with the load W = W ₃ , a step difference as shown by d occurs in the air-fuel ratio A / F. However, in response to this, a step difference is also generated in the air utilization rate, which causes a torque step difference. Therefore, in the present embodiment, the load W =
From the time point when W ₁ (corresponding to the broken line A ₂ in FIG. 3) is reached, the intake amount is throttled as shown by the broken line B ₂ in FIG. 4 (b), and as shown in FIG. 4 (a), When the air-fuel ratio A / F reaches a value corresponding to the excess air ratio λ = 1 (W = W ₂ ), the direct injection is switched to the manifold injection, and the broken line B _{1 in} FIG.
As described above, the gap of the air-fuel ratio (air utilization rate) is prevented from occurring during the switching. Engine load W of air-fuel ratio A / F, intake air amount Qa, and fuel supply amount Qf when switching is performed in this way
Characteristics for, respectively, line B ₁ in 4 (a), indicated by a broken line B ₄ fold line B ₂ and the fourth diagram of Fig. 4 (b) (c).

In step S7, the main nozzle relief valve 41 and the pilot nozzle relief valve 42 respectively connect the main nozzle passage 32 and the pilot nozzle passage 33 with the relief passage 38.
When the direct injection is performed, the fuel supplied to the main nozzle 26 and the pilot nozzle 28 is completely returned to the branch fuel supply passage 31 through the relief passage 38. , Direct injection is stopped (see FIG. 1). Then, fuel injection is started from the second fuel injection valve 18, and manifold injection is performed.

Thereafter, the control proceeds to step S15, and the control is returned to step S1 and continued or stopped in accordance with the on / off state of the ignition switch.

Here, another preferred embodiment of the above-mentioned method for switching between direct injection and manifold injection will be described.

In steps S5 and S6 described above, the intake amount is throttled by throttling the throttle valve, but it is possible to throttle the intake amount by using the pumping loss reducing means of the early closing or late closing method without throttling the throttle valve 17. For example, it is possible to reduce the pumping loss and prevent the occurrence of torque shock when switching from direct injection to manifold injection.

Further, the feedback control of the air-fuel ratio is performed in the region IV of FIG. 3, and the direct injection and the manifold injection are switched during the feedback control of the air-fuel ratio, so that the torque shock can be prevented more accurately. it can.

Alternatively, when the direct injection is switched to the manifold injection, the intake air amount may be reduced by an amount corresponding to the difference between these air utilization rates. Also in this case, torque shock at the time of switching can be effectively prevented, and smooth switching can be performed.

In addition, a bypass intake passage that links the throttle valve with the accelerator pedal and bypasses the throttle valve is provided.When the load is light, the bypass intake passage is opened so that there is no throttle, and when the load is high, the bypass intake passage is closed. The intake air amount control may be performed by. By doing so, the control can be simplified.

By the way, on the other hand, as a result of the comparison in step S3, the engine RE
If the operating state of does not correspond to the switching region from direct injection to manifold injection or from manifold injection to direct injection (NO), the control proceeds to step S9 to continue the current fuel injection method.

In step S9, the operating state of the engine RE is the broken line in FIG.
It is compared whether or not it is in the light load region (region II) on the low rotation side or the low load side from A ₂ . As a result of the comparison, if the operating condition of the engine RE does not correspond to the light load region (region II in FIG. 3) (NO), the operating condition of the engine RE indicates that the engine RE is in the high load region (FIG. 3). Region I), control is passed to step S10, and manifold injection is continued. After that, the control proceeds to step S15, and the control returns to step S1 and continues or is ended in accordance with the ON / OFF of the ignition switch.

On the other hand, as a result of the comparison in step S9, if the operating state of the engine RE falls within the light load region (region II in FIG. 3) (YE
S), further, the control proceeds to step S11 in order to compare whether the operating state of the engine RE is in the extremely light load region where the intake air needs to be throttled to prevent the combustion temperature from decreasing.

As a result of the comparison in step S11, if the operating state of the engine RE does not correspond to the extremely light load region shown in the region VII of FIG. 5 (NO), the engine RE is in the normal light load region, so control is performed. In step S12, the direct injection from the main nozzle 26 and the pilot nozzle 28 is continued. After that, the control proceeds to step S15, and the control returns to step S1 and continues or is ended depending on whether the ignition switch is turned on or off.

On the other hand, as a result of the comparison in step S11, if the operating state of the engine RE falls within the extremely light load region shown in the region VII of FIG. 5 (YES), the control proceeds to step S13 to perform the intake air amount control again. To be

In step S13, the intake air amount is reduced again. In the present embodiment, in a predetermined light load range, the throttle valve 17 is fully opened so that there is substantially no throttling, and the output control is performed by the fuel injection amount from the main nozzle 26. At this time, the intake air amount is substantially constant at the same rotation speed regardless of the load. As a result, as described above, the stratification of the intake air is effectively performed and the combustibility is enhanced. However, in the extremely light load region (region VII in FIG. 5) where the load is further reduced, the intake air is reduced. When the fuel is supplied without being throttled, the fuel supply amount is extremely small, and therefore, the heat generation amount is small, so that the combustion temperature is lowered and the exhaust temperature is lowered. As a result, the activity of the catalyst of the exhaust gas purifying device is lowered, and the problem that the cleanliness of the exhaust gas is deteriorated occurs. Therefore, when the operating state of the engine RE is extremely light load, which is lower than a predetermined load, the throttle valve 18 is throttled to control the intake air amount. By this, the intake amount
Qa becomes like the broken line D ₁ in FIG. In this way
After reducing the intake air amount, the control proceeds to step S14.

In this case, in step S14, since the fuel injection amount is very small in this case, fuel injection is performed only from the pilot nozzle 28. At this time, the main nozzle passage 32 is relieved to the relief passage 38.
The relief valve 41 for the main nozzle is switched so as to be connected to, and the fuel injection from the main nozzle 26 is stopped.
Therefore, fuel is injected into the working chamber 6 only through the pilot nozzle 28. As described above, the fuel injection amount from the pilot nozzle 28 is constant regardless of the load. In this way, since the intake air amount is throttled in the extremely light load region, it is possible to prevent the exhaust gas temperature from decreasing, enhance the activity of the exhaust gas purifying catalyst, and enhance the cleanliness of the exhaust gas. Further, since the intake amount is throttled and the air-fuel mixture has a rich composition, the ignitability becomes better than that during super lean burn. Furthermore, even if a misfire occurs during sudden deceleration,
Since the intake air amount is narrowed, it is possible to prevent an abnormal rise in the catalyst temperature of the exhaust gas purification device that would occur during misfire during non-throttle.

In step S13, the intake amount is reduced by closing the throttle valve 18, but instead of this, it is possible to reduce the intake amount by using a pumping loss reducing means such as an early closing method or a late closing method. For example, the same effect (prevention of decrease in exhaust gas temperature, etc.) can be obtained while suppressing increase in pumping loss.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of a rotary piston engine showing an embodiment of the present invention. FIG. 2 is a control flowchart showing a method of controlling the rotary piston engine shown in FIG. FIG. 3 is a diagram showing an operating region for direct injection, an operating region for manifold injection, etc. of the rotary piston engine shown in FIG. 1 with the engine load and the engine speed as parameters. FIGS. 4 (a), (b), and (c) are graphs showing the characteristics of the air-fuel ratio, the intake amount, and the fuel supply amount with respect to the engine load when switching from direct injection to manifold injection, respectively. FIG. 5 is a diagram showing an extremely light load range in which the intake air amount is controlled during direct injection. FIG. 6 is a diagram showing the intake air amount with respect to the engine load when the intake air amount control is performed in the extremely light load region. RE …… Rotary piston engine, 5 …… Intake port,
6 ... Working chamber, 12 ... Intake passage, 15 ... Control circuit, 18 ...
… Second fuel injection valve, 26 …… Main nozzle, 28 …… Pilot nozzle.

Claims (1)

[Claims] 1. A first fuel injection valve for directly injecting fuel into a cylinder, a second fuel injection valve for injecting fuel into an intake passage, and a fuel injection from the second fuel injection valve being stopped when the load is low. At the same time, the intake air amount control is substantially stopped, and the fuel injection amount of the first fuel injection valve is controlled to perform output control,
When the load is high, the fuel injection from the first fuel injection valve is stopped, the fuel injection amount of the second fuel injection valve is controlled to maintain the intake air at a predetermined air-fuel ratio, and the output control is performed by the intake air amount control. Means for changing the control from the low load side control to the high load side control, the intake air amount control is performed to make the air fuel ratio substantially equal to the predetermined air fuel ratio, and then the fuel injection from the first fuel injection valve is stopped and the second fuel is stopped. An engine control device, comprising: a switching control means for controlling to inject fuel from an injection valve.