JP5736920B2 - Hybrid vehicle engine control system - Google Patents

Description

The present invention relates to an engine control device for a hybrid vehicle.

As an engine, a gaseous fuel engine to which a gaseous fuel such as hydrogen or LPG is supplied has been put into practical use. In addition, the number of hybrid vehicles equipped with an engine and a driving motor tends to increase. Patent Document 1 discloses an engine for a hybrid vehicle. A gas fuel engine is disclosed. Patent Document 2 discloses that in a hybrid vehicle, engine rotation is performed within a high efficiency range.

On the other hand, recent engines are increasing in number that automatically stop and start the engine. For example, when the engine is mounted on a vehicle that performs idling stop or a hybrid vehicle, the engine is automatically stopped and started. In such an automatic engine stop and start operation, the automatic start operation is performed quite frequently, so that the power consumption of the battery required for engine cranking increases.

JP 2006-250024 A JP 2007-195334 A

By the way, in a hybrid vehicle, when a mounted engine is a gas fuel engine, it is preferable in terms of reducing harmful components of exhaust gas. On the other hand, even in the case of a gas fuel engine, when the engine is started, the air-fuel ratio becomes considerably rich, so that the amount of Raw / NOx generated increases. This Raw / NOx can be reduced when fuel injection is performed during the intake stroke as compared to when fuel injection is performed within the range from the end of the intake stroke to the compression stroke. However, when the amount of charge of the battery that supplies power to the driving motor is small, if the fuel injection is performed in the intake stroke to reduce Raw / NOx, the charging efficiency is greatly reduced because the fuel is gas. The engine output (engine torque) is lowered, which is not preferable in terms of preventing the battery charge from being reduced.

The present invention has been made in view of the above circumstances, and its purpose is to prevent reduction of Raw / NOx and start-up of battery charge in a hybrid vehicle equipped with an engine supplied with gaseous fuel. It is an object of the present invention to provide an engine control device for a hybrid vehicle that can satisfy both of these requirements at a high level.

In order to achieve the above object, the following solution is adopted in the present invention. That is, as described in claim 1 in the claims,
Driven by receiving power from at least one of an engine to which gaseous fuel is supplied, a generator that is driven by the engine to generate electric power, a battery that stores electric power generated by the generator, and the generator An engine control device for a hybrid vehicle comprising a travel motor,
Charge amount detecting means for detecting the charge amount of the battery;
The gaseous fuel supplied to the engine, the first fuel injection mode supplies during the intake stroke, and the fuel injection means can be selected a second fuel injection mode to supply a range of period of the compression stroke from the intake stroke end,
Control means for controlling the fuel injection means;
With
The control means determines the fuel injection ratio in the first fuel injection mode when the charge amount detected by the charge amount detection means is equal to or greater than a predetermined value when the engine is started. On the other hand, when the charge amount is less than the predetermined value, the charge amount in the first fuel injection mode is larger than the fuel injection ratio in the two fuel injection modes. Reducing the fuel injection rate to increase the fuel injection rate in the engine second fuel injection mode;
It is like that. According to the above solution, when the charge amount of the battery is large, it is possible to increase the fuel injection ratio in the first fuel injection mode and to reduce Raw / NOx as compared to when the charge amount is small. Also, when the charge amount of the battery is small, the fuel injection ratio in the first fuel injection mode is reduced and the fuel injection ratio in the second fuel injection mode is increased compared to when the charge amount is large. It is possible to prevent the charging amount of the battery from being lowered by increasing the charging efficiency of the engine (increasing the battery charging efficiency by the engine).

According to the present invention, both Raw / NOx reduction and battery charge reduction prevention can be satisfied at a high level.

The simplified top view which shows an example at the time of applying this invention to a hybrid vehicle. The system diagram which shows an example of a gaseous fuel engine. The figure which shows an example when driving | running | working, using the driving | running | working using only battery power, and generating electric power with an engine. The figure which shows the example of a control system of this invention in a block diagram. The time chart which shows an example of the fuel-injection aspect at the time of engine starting when a battery charge amount is large, and an air fuel ratio setting. The time chart which shows an example of the fuel-injection aspect at the time of engine starting at the time of battery charge amount being small, and an air fuel ratio setting. The flowchart which shows the example of control of this invention.

In FIG. 1, an automobile V as a vehicle has a body (vehicle body) indicated by reference numeral 1, left and right front wheels indicated by reference numeral 2, and left and right rear wheels indicated by reference numeral 3. A traveling motor 4 is connected to the left and right front wheels 2 via a differential gear 5A and a drive shaft 5B. In other words, in the embodiment, a front-wheel drive vehicle in which only the left and right front wheels 2 are driven.

In addition to the traveling motor 4, an engine 6, a generator 7, and an inverter 8 are disposed at the front portion of the body 1. A battery 9 and a fuel tank 10 are disposed below the floor surface of the body 1 from the middle part in the front-rear direction to the rear part. The engine 6 is a spark-ignition gas fuel engine, and is supplied with, for example, hydrogen as a gaseous fuel stored in the fuel tank 10.

The generator 7 is driven by the engine 6 to generate electric power, and also functions as a starting motor for starting the engine 6 by receiving electric power from the battery 9. The battery 9 is composed of, for example, a lithium ion battery, and has a high voltage (for example, 300 to 500 V) and a large capacity. The electric power stored in the battery 9 is supplied to the traveling motor 4 and travels, and the electric power stored only in the battery 9 in the maximum power storage state can travel several tens km (for example, 30 to 60 km). Further, a low-voltage (for example, 12V) battery 11 is mounted on the rear end of the body 1, and this battery 11 is used for various on-vehicle electric devices such as a spark plug, a fuel injection valve, a headlight, a wiper, and an audio. Power is supplied.

FIG. 2 shows an example of the engine 6 and its intake / exhaust system. In the embodiment, the engine 6 is a Wankel type rotary piston engine, and has two cylinders of a first cylinder RA and a second cylinder RB in series. Branch intake passages 21A and 21B that are individually connected to the intake ports of the cylinders RA and RB are connected to one common intake passage 22. A throttle valve 23 is disposed in the common intake passage 22. Further, first fuel injection valves 24A and 24B for port injection are disposed in the respective branch intake passages 21A and 21B. The first fuel injection valves 24A and 24B are for obtaining a first fuel injection mode in which fuel is injected during the intake stroke. As the fuel injection valve, second fuel injection valves 25A and 25B that directly inject fuel into the cylinder (working chamber) are further provided. The second fuel injection valves 25A and 25B perform fuel injection in the range from the end of the intake stroke to the compression stroke (in the embodiment, fuel injection is performed during the compression stroke), and a second fuel injection mode is obtained. It has become a thing.

Branch exhaust passages 26 </ b> A and 26 </ b> B that are individually connected to the exhaust ports of the cylinders RA and RB are connected to one common exhaust passage 27. An air-fuel ratio sensor 28 is disposed in the common exhaust passage 27, and an exhaust gas purification catalyst (NOx catalyst in the embodiment) 29 is disposed on the downstream side of the air-fuel ratio sensor 28.

The common intake passage 22 and the common exhaust passage 27 are connected by an EGR passage 30, and an EGR valve 31 is connected to the EGR passage 30. The EGR passage 30 is opened to the common intake passage 22 on the downstream side of the throttle valve 23, and is opened to the common exhaust passage 27 on the upstream side of the air-fuel ratio sensor 28.

Each cylinder RA, RB has two spark plugs 33A, 33B. After the engine is started, fuel injection from the first fuel injection valves 24A and 24B is executed at a relatively low rotation and low load, while fuel injection from the second fuel injection valves 25A and 25B is relatively Performed at high rotation or high load. A mixture of air and hydrogen as fuel injected from the fuel injection valve is ignited by the spark plugs 33A and 33B. Combustion is performed by igniting the air-fuel mixture. The fuel injection control when starting the engine will be described later.

FIG. 3 shows how the traveling state of the vehicle V is changed according to the amount of power stored in the battery 9. That is, when the charged amount of the battery 9 is large (for example, until the charged amount is reduced to 40%), the engine 6 is stopped (automatically stopped), and the traveling motor 4 is driven only by the power supply from the battery 9. (So-called plug-in travel). On the other hand, when the storage amount of the battery 9 is small (for example, when the storage amount is less than 40%), the engine 6 is started (automatic start), and the generator 7 generates power, and the generator 7 generates power. Electric power is supplied to the traveling motor 4 and surplus power is supplied to the battery 9. When the amount of electricity stored in the battery 9 is increased by the power generated by the generator 7 (for example, when the amount of electricity stored reaches 70%), the engine 4 is automatically stopped (resumption of plug-in travel). As described above, the engine 6 automatically repeats stop and start according to the amount of power stored in the battery 9, and when the engine 6 is started, the generator 7 generates power and travels and stores power in the battery 9. Is done. Note that when the vehicle V is decelerated, regeneration is performed by the traveling motor 4, and electric power generated by regeneration is stored in the battery 9.

FIG. 4 is a block diagram showing an example of the control system of the present invention. In the figure, U is a controller (control unit) configured using a microcomputer. The controller U controls the traveling motor 4, the engine 6 (particularly the fuel injection valve), the generator 7, and the inverter 8. Power transfer between the battery 9 and the travel motor 4 via the inverter 8, power transfer between the generator 7 and the battery 9, power supply from the generator 7 to the travel motor 4, and from the battery 9 to the battery 11 is supplied with electric power.

The controller U performs engine control such as fuel injection control and ignition timing control, and also performs automatic stop and start control of the engine 6 and the like. A signal from the air-fuel ratio sensor 28 is input to the controller U. The air-fuel ratio sensor 28 is a linear sensor and detects an excess air ratio λ as an air-fuel ratio. In addition, the controller U receives signals from various sensors or switches S1 to S6. The sensor S1 detects the vehicle speed. The sensor S2 detects the accelerator opening. The sensor S3 detects the engine coolant temperature. The sensor S4 detects the engine speed. The switch S5 detects that the brake pedal has been depressed. The sensor S6 detects the amount of charge of the battery 9.

The automatic stop and automatic start of the engine 6 by the controller U are performed according to the following conditions, for example. First, as described above, automatic stop and automatic start according to the charged amount of the battery 9 are performed. Even under the condition that the engine is automatically started according to the amount of power stored in the battery 9, automatic stop and automatic start by idle stop are performed. That is, for example, when the accelerator opening is 0, the vehicle speed is 0, and the brake switch S5 is ON (when the brake pedal is depressed), the engine 6 is automatically stopped. When the brake switch S5 is turned off from the automatic stop state, the engine 6 is automatically started.

Next, referring to FIG. 5, when the charge amount of the battery 9 is large, that is, when the charge amount detected by the sensor S6 is larger than a preset predetermined value (for example, 50% as a charge rate), fuel injection An example of control is shown. In FIG. 5, when a start command of the engine (when the start condition has been satisfied), the fuel injection during the intake stroke, the first fuel injection valve 24A, is done only from 25B, the second fuel Fuel injection from the injection valves 25A and 25B is not performed (execution of fuel injection only in the first fuel injection mode). After the time point t1 when the engine is started by fuel injection from the first fuel injection valves 24A and 24B and the engine speed reaches a predetermined rotation speed (for example, 1000 rpm), the first fuel injection valves 24A and 24B. And the second fuel injection valves 25A and 25B, the fuel injection is executed, and the fuel injection rate at that time is, for example, 50%. Further, the air-fuel ratio is relatively rich from the start of the engine to the predetermined rotational speed (in the embodiment, the excess air ratio λ is set to 1.2, for example, but is preferably set to λ = 1 or more). As a result, the engine can be started reliably and promptly. Further, after the engine speed becomes equal to or higher than the predetermined speed, the air-fuel ratio is relatively lean (for example, the excess air ratio λ = 2.2). When starting the engine in which the air-fuel ratio is made rich, fuel injection is executed only from the first fuel injection valves 24A and 24B, which is preferable in terms of reducing Raw / NOx.

FIG. 6 shows an example of fuel injection control when the charge amount of the battery 9 is small (charge ratio is less than 50%, for example). At this time, fuel injection is performed from both the first fuel injection valves 24A and 24B and the second fuel injection valves 25A and 25B. In the fuel injection control, the engine start timing is divided into an initial start period and a late start period, and the first fuel is higher in the initial start period (before the time point t11) than in the late start period (range t11 to t12). The fuel injection ratios at the injection valves 24A and 24A are made larger than the fuel injection ratios at the second fuel injection valves 25A and 25B. Specifically, at the initial start time (for example, before the time t11 when the engine speed is 500 rpm or less), the fuel injection ratio from the first fuel injection valves 24A and 24B is set to 70%, for example. The fuel injection ratio from the fuel injection valves 25A and 25B is set to 30%. Further, in the late start period (for example, when the engine speed is between 500 and 1000 rpm, between the time t11 and the time t12), the fuel injection ratio from the first fuel injection valves 24A and 24B is set to 60%, for example. The fuel injection ratio from the two fuel injection valves 25A and 25B is 40%. After the start (after t12 when the engine speed becomes 1000 rpm or more), the fuel injection ratio from the first fuel injection valves 24A and 24B and the fuel injection from the second fuel injection valves 25A and 25B. Each percentage is 50%.

The air-fuel ratio at the time of starting the engine when the battery charge is small is changed from rich to lean with the passage of time (however, the excess air ratio λ is rich in a range of at least 1.0). Specifically, when the air-fuel ratio is indicated by the excess air ratio λ, the initial start is richest, for example, λ = 1.2, and the late start is rich, for example, λ = 1.6. λ = 2.2. Thus, at the time of starting, the air-fuel ratio is made rich so that the engine can be started reliably and promptly. In addition, since fuel injection is performed from the second fuel injection valves 25A and 25B in the range from the end of the intake stroke to the compression stroke, the charging efficiency is improved, the engine torque is increased, and the charge amount of the battery 9 is reduced accordingly. Is prevented (the battery can be actively charged).

FIG. 7 is a flowchart showing the control contents of the controller U described above, and this flowchart will be described below. In the following description, Q indicates a step. First, in Q1, signals from various sensors or switches S1 to S6 are read. Thereafter, in Q2, it is determined whether or not there is an engine start command (whether or not the start condition is satisfied). If the determination in Q2 is NO, the process returns to Q1.

If the determination in Q2 is YES, it is determined in Q3 whether or not the charge amount of the battery 9 detected by the sensor S6 is equal to or greater than a predetermined value BA (for example, 50%). When the determination in Q3 is YES, in Q4, fuel injection is executed only from the first fuel injection valves 24A, 24B, and the air-fuel ratio at that time is 1.2 with the excess air ratio λ. After Q4, in Q5, it is determined whether or not the engine speed N detected by the sensor S4 has become equal to or higher than a preset second predetermined speed (for example, 1000 rpm). If the determination in Q5 is NO, the control in Q4 is continued assuming that the engine is starting. If YES in Q5, fuel injection is performed at a fuel injection rate of 50% from both the first fuel injection valves 24A and 24B and the second fuel injection valves 25A and 25B in Q6. The air-fuel ratio is also set to λ = 2.2.

When the determination in Q3 is NO, that is, when the amount of charge of the battery 9 is small, in Q7, fuel is injected from the first fuel injection valves 24A and 24B at a fuel injection ratio of 70% and the second fuel injection valve 25A. 25B, fuel is injected at a fuel injection rate of 30%. At this time, the air-fuel ratio becomes the richest λ = 1.2. After Q7, in Q8, it is determined whether or not the engine speed N is within a preset range between a first predetermined speed N1 (for example, 500 rpm) and a second predetermined speed N2 (for example, 1000 rpm). If the determination in Q8 is NO, the control in Q7 is continued assuming that the engine is still in the initial stage of startup.

When the determination in Q8 is YES, it means that it is in the late start-up period. In this case, in Q9, fuel is injected from the first fuel injection valves 24A and 24B at a fuel injection ratio of 60% and the second fuel is injected. Fuel is injected from the injection valves 25A and 25B at a fuel injection ratio of 40%. In addition, the air-fuel ratio at this time is λ = 1.6 which becomes rich. After Q9, at Q10, it is determined whether or not the engine speed N is equal to or greater than a second predetermined speed N2. When the determination in Q10 is NO, the control in Q9 is continued, assuming that it is still in the late start range. If YES in Q10, the process proceeds to Q6 described above.

Although the embodiment has been described above, the present invention is not limited to the embodiment, and can be appropriately changed within the scope described in the scope of claims. For example, the invention includes the following cases. . Wheel driving may be performed by the engine 6. In this case, wheel driving by only the engine 6, wheel driving by only the traveling motor 4, and wheel driving by both the engine 6 and the traveling motor 4 are possible. May be appropriately switched. The engine 6 may be a reciprocating engine.

In FIG. 5, as in FIG. 6, the fuel injection ratio and the air-fuel ratio in the late start period are set to numerical values between the early start period and after the start period separately in the early start period and late start period. Good. In FIG. 5, fuel injection may be performed from the second fuel injection valves 25 </ b> A and 25 </ b> B from the beginning of startup (however, the fuel injection ratio is reduced as compared with the case of FIG. 5). In FIG. 6, the fuel injection at the initial stage of the start may be performed only from the second fuel injection valves 25A and 25B. In both cases of FIGS. 5 and 6, during start-up, either or both of the fuel injection ratio and the air-fuel ratio may be changed in three steps or more, or may be changed continuously. Of course, the object of the present invention is not limited to what is explicitly stated, but also implicitly includes providing what is substantially preferred or expressed as an advantage.

The present invention is suitable for application to, for example, a hybrid vehicle equipped with an engine using hydrogen as fuel.

V: Vehicle 4: Driving motor 6: Engine 7: Generator 9: Battery 10: Fuel tank 24A, 24B: First fuel injection valve (for port injection)
25A, 25B: Second fuel injection valve (for direct injection)
28: Air-fuel ratio sensor 33A, 33B: Spark plug U: Controller S6: Sensor (charge amount)

Claims (6)

Driven by receiving power from at least one of an engine to which gaseous fuel is supplied, a generator that is driven by the engine to generate electric power, a battery that stores electric power generated by the generator, and the generator An engine control device for a hybrid vehicle comprising a travel motor,
Charge amount detecting means for detecting the charge amount of the battery;
The gaseous fuel supplied to the engine, the first fuel injection mode supplies during the intake stroke, and the fuel injection means can be selected a second fuel injection mode to supply a range of period of the compression stroke from the intake stroke end,
Control means for controlling the fuel injection means;
With
The control means determines the fuel injection ratio in the first fuel injection mode when the charge amount detected by the charge amount detection means is equal to or greater than a predetermined value when the engine is started. On the other hand, when the charge amount is less than the predetermined value, the charge amount in the first fuel injection mode is larger than the fuel injection ratio in the two fuel injection modes. Reducing the fuel injection rate and increasing the fuel injection rate in the second fuel injection mode;
An engine control device for a hybrid vehicle. In claim 1,
The fuel injection means includes a first fuel injection valve that injects fuel toward the intake port, and a second fuel injection valve that injects fuel directly into the cylinder,
The fuel injection from the first fuel injection valve is the first fuel injection mode,
The fuel injection from the second fuel injection valve is the second fuel injection mode.
An engine control device for a hybrid vehicle. In claim 2,
When the charge amount detected by the charge amount detection means is equal to or greater than the predetermined value, fuel is injected only from the first fuel injection valve,
When the charge amount detected by the charge amount detection means is less than the predetermined value, fuel is injected from both the first fuel injection valve and the second fuel injection valve.
An engine control device for a hybrid vehicle. In any one of Claims 1 thru | or 3,
When the engine is started, the air-fuel ratio is made richer than after the start, and the fuel injection ratio in the first fuel injection mode is made larger than the fuel injection ratio in the second fuel injection mode. A hybrid vehicle engine control device. In claim 4,
The air-fuel ratio is made richer in the early stage of engine startup than in the later stage of startup, and the fuel injection ratio in the first fuel injection mode is made larger than the fuel injection ratio in the second fuel injection mode. An engine control device for a hybrid vehicle characterized by the above. In claim 4 or claim 5,
An engine control device for a hybrid vehicle, characterized in that fuel injection is performed only in the first fuel injection mode at least at the initial start of the engine.

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