vehicle

Abstract

It suppresses the decrease in output under low-pressure conditions. [Solution] The vehicle comprises an engine 10 having a main combustion chamber 1, a sub-chamber 11 adjacent to the main combustion chamber 1, a first ignition device 20 facing the sub-chamber 11, and a second ignition device 30 facing the main combustion chamber 1; an environmental information acquisition means 53 for acquiring ambient pressure information; and a control unit 51 for controlling ignition by the first ignition device 20 and the second ignition device 30. The control unit 51 can select first ignition control, which performs ignition by the first ignition device 20 and does not perform ignition by the second ignition device 30 when the load of the engine 10 is below a predetermined load threshold, and second ignition control, which performs ignition by the second ignition device 30 and does not perform ignition by the first ignition device 20 when the load of the engine 10 is above a predetermined load threshold. The control unit 51 can select first ignition control, which sets a predetermined load threshold to the first predetermined load in a standard pressure environment where the atmospheric pressure information is above a predetermined value, and sets a predetermined load threshold to the low load side in a low pressure environment where the atmospheric pressure information is below a predetermined value.

Description

Technical Field

[0001] This invention relates to a vehicle equipped with an internal combustion engine.

Background Art

[0002] Conventionally, a number of technologies for auxiliary chamber type internal combustion engines with an auxiliary chamber provided in the main combustion chamber have been disclosed. The auxiliary chamber is partitioned from the main fuel chamber through a partition wall having a plurality of minute injection holes. Further, the auxiliary chamber is equipped with an ignition device for igniting the air-fuel mixture.

[0003] In an auxiliary chamber type internal combustion engine, a combustion method called JET ignition is widespread, in which an air-fuel mixture having the same air-fuel ratio as that in the main combustion chamber is formed in the auxiliary chamber, the air-fuel mixture in the auxiliary chamber is ignited, and the main combustion chamber air-fuel mixture is rapidly burned by a flame jet ejected into the main combustion chamber through the injection holes. Further, development of a technique for performing combustion assist for a region where the flame jet by JET ignition is weak using an ignition device provided in the main combustion chamber separately from the ignition device in the auxiliary chamber is also in progress (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Generally, in high-altitude areas under low-pressure conditions, internal combustion engines (hereinafter referred to as engines) need to increase the intake air volume (volume flow rate) to achieve the same power output as at sea level. However, even when attempting to increase the intake air volume, naturally aspirated (NA) engines have an upper limit on engine speed, and turbocharged engines have an upper limit on turbine speed. Therefore, a decrease in maximum power output may be unavoidable at high altitudes in both cases.

[0006] Furthermore, at high altitudes, even if the intake air velocity into the engine's combustion chamber is the same as at sea level, the lower air density and oxygen concentration may prevent the desired acceleration from being achieved. Moreover, at high altitudes, increasing the intake air volume (volume flow rate) to operate at the same power output as at sea level tends to lower the intake negative pressure. This decrease in intake negative pressure reduces pumping losses, allowing operation with a smaller air volume (lower mass flow rate). However, this reduction in pumping losses and the decrease in required air volume leads to a decrease in compression pressure in the cylinder, resulting in a reduced combustion speed. While a reduced combustion speed increases the margin against knocking, allowing for ignition advance, if the ignition timing is already at the optimal timing (the ignition timing that maximizes torque), further ignition advance can cause knocking and increase nitrogen oxides (NOx) in the exhaust gas, making it undesirable.

[0007] Therefore, the objective of this invention is to suppress the decrease in output under low-pressure conditions. [Means for solving the problem]

[0008] To solve the above problems, this invention provides a vehicle comprising an engine having a main combustion chamber, a sub-chamber provided adjacent to the main combustion chamber, a first ignition device facing the sub-chamber, and a second ignition device facing the main combustion chamber; an environmental information acquisition means for acquiring ambient pressure information; and a control unit for controlling ignition by the first and second ignition devices. The control unit can select between first ignition control, where ignition is performed by the first ignition device and not by the second ignition device when the engine load is below a predetermined load threshold, and second ignition control, where ignition is performed by the second ignition device and not by the first ignition device when the load is above the predetermined load threshold. The control unit also employs a vehicle that performs first ignition expansion control, where, under standard pressure conditions where the atmospheric pressure information is above a predetermined value, the predetermined load threshold is set to a first predetermined load, and under low pressure conditions where the atmospheric pressure information is below a predetermined value, the predetermined load threshold is set to a lower load than the first predetermined load (Configuration 1).

[0009] In Configuration 1, under the standard pressure environment, if the engine load is equal to or greater than the first predetermined load and the engine speed is equal to or greater than the first predetermined rotational speed, a third ignition control is selected, in which ignition is performed by the first ignition device and the second ignition device within the same combustion cycle. In the low pressure environment, if the engine load is equal to or greater than the first predetermined load and the engine speed is equal to or greater than the first predetermined rotational speed, the first ignition control is selected. (Configuration 2)

[0010] In configuration 1 or 2, a supercharger is provided to supercharge the intake air introduced into the engine, and under the standard pressure environment, supercharging is performed when the engine load is above a predetermined load boundary value, and in the case of the first ignition expansion control, a configuration can be adopted in which the supercharging region is expanded to the low load side. (Configuration 3)

[0011] In any one of configurations 1 to 3, the first ignition expansion control can be performed when the engine speed is at or above a second predetermined speed that is lower than the first predetermined speed (configuration 4).

[0012] Furthermore, in configuration 4, under the standard pressure environment and the low pressure environment, if the engine load is less than the first predetermined load and the engine speed is less than the second predetermined speed, a configuration can be adopted in which a third ignition control is performed by the first ignition device and the second ignition device within the same combustion cycle (configuration 5). [Effects of the Invention]

[0013] According to this invention, the decrease in output can be suppressed in a low-pressure environment. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram showing a vehicle according to this invention. [Figure 2] This is a cross-sectional view showing the main components of the engine installed in the vehicle. [Figure 3] This is a cross-sectional view taken along line III-III in Figure 2. [Figure 4A] This graph shows the control of this invention on flat ground (standard pressure conditions). [Figure 4B] This graph illustrates the control of this invention at high altitudes (low pressure conditions). [Modes for carrying out the invention]

[0015] Embodiments of this invention will be described based on the drawings. Figures 1 to 3 show an internal combustion engine 10 and its control device, as well as components surrounding the internal combustion engine 10, which are mounted on a vehicle 60 according to an embodiment of this invention. Note that the figures show only components directly related to this invention, and descriptions of other general components are omitted.

[0016] As shown in Fig. 2, the internal combustion engine 10 is a pre-chamber type internal combustion engine 10 having as main components a main combustion chamber 1 formed by a cylinder head 13 and a cylinder block 2, a piston 3 that reciprocates within the main combustion chamber 1, and a pre-chamber 11 provided adjacent to the main combustion chamber 1. Hereinafter, in the embodiments, the internal combustion engine 10 is referred to as the engine 10. Note that the figure shows a main part of one cylinder out of a plurality of cylinders of the engine 10. In the embodiments, for example, a four-cylinder engine having four cylinders is assumed, but this invention is applicable regardless of the number of cylinders.

[0017] As shown in Fig. 1, the engine 10 is configured to include an intake passage 5 that feeds intake air into the main combustion chamber 1, an exhaust passage 6 drawn out from the main combustion chamber 1, a fuel injection device 40 that injects fuel, etc. The openings 5a, 6a of the intake passage 5 and the exhaust passage 6 to the main combustion chamber 1 are opened and closed by an intake valve 7 and an exhaust valve 8, respectively. In the embodiments, as the fuel injection device 40, a port injection valve 40a that injects fuel into an intake port which is a connection part of the intake passage 5 to the main combustion chamber 1 and a direct injection valve 40b that directly injects fuel into the main combustion chamber 1 are provided, but the fuel injection device 40 may be only one of the port injection valve 40a and the direct injection valve 40b.

[0018] In the intake passage 5, an intake air cooling device (intercooler) 16 that cools the intake air flowing through the intake passage 5, a compressor of a supercharger (turbocharger) 15, a throttle valve 18 that adjusts the flow passage area of the intake passage 5, and further, an air cleaner etc. are provided toward the upstream side from the intake port. Also, in the exhaust passage 6, a turbine of the supercharger 15, an exhaust purification unit 17 provided with a catalyst etc. that removes harmful substances in the exhaust gas, a muffler etc. are provided toward the downstream side from an exhaust port which is a connection part to the main combustion chamber 1.

[0019] The operation of the supercharger 15 is such that when the turbine rotates by the exhaust gas flowing through the exhaust passage 6, the rotation is transmitted to the compressor of the intake passage 5, and supercharging is performed on the intake air flowing through the intake passage 5 by the rotation of the compressor.

[0020] The vehicle 60 equipped with this engine 10 includes an electronic control unit (ECU) 50 for controlling the engine 10. The electronic control unit 50 issues commands necessary for controlling the engine, such as fuel injection by the fuel injection device 40, control of the boost pressure, control of the opening degree of the throttle valve 18, and others.

[0021] In the intake passage 5, as a sensor device for acquiring information necessary for controlling the engine 10, an air flow sensor c for detecting the amount of air flowing in the intake passage 5 and the like are provided. Further, the engine 10 is provided with a rotational speed sensor b for detecting the rotational speed of the crankshaft, a water temperature sensor for detecting the temperature of the cooling water for cooling the cylinder block 2 and the like. Sensors not labeled are not shown (the same applies in the following paragraphs).

[0022] The vehicle 60 is equipped with an accelerator pedal and the like. The accelerator pedal is provided with an accelerator position sensor for detecting the amount of depression of the accelerator by the driver. Also, the vehicle 60 is provided with an atmospheric pressure sensor a for acquiring information on the ambient atmospheric pressure. Information from these various sensors can be acquired by the electronic control unit 50 through a cable. In the figure, a part of the cable is not shown.

[0023] The electronic control unit 50 is a collection of electronic control devices (computers) including interfaces, processors, memories, etc. connected to each other via a bus. The electronic control unit 50 mainly includes a control unit 51 for controlling the engine 10 and a vehicle control unit 52 for controlling the operation of the entire vehicle 60. Also, the electronic control unit 50 includes an environmental information acquisition means 53 for acquiring atmospheric pressure information around the vehicle 60.

[0024] The environmental information acquisition means 53 acquires information on the atmospheric pressure around the vehicle 60 using information from the pressure sensor a. Here, instead of the pressure sensor a, the altitude information (altitude above sea level) of the location where the vehicle 60 is located may be acquired using a GPS device and map function, and the atmospheric pressure information may be acquired from that altitude information. In other words, the means for acquiring atmospheric pressure information may be other methods other than those exemplified.

[0025] As shown in Figure 2, the main combustion chamber 1 of the engine 10 is composed of a space enclosed by the lower surface of the cylinder head 13, the inner surface 2a of the cylinder bore formed in the cylinder block 2, and the top surface 3a of the piston 3. The sub-chamber 11 adjacent to the main combustion chamber 1 is composed of a space separated from the main combustion chamber 1 by a main body member 12 attached to the lower surface of the cylinder head 13.

[0026] The main body member 12 has a bottom portion and a circumferential portion, forming a concave shape that opens upward, and is located at the top of the cylindrical axis of the main combustion chamber 1. The main body member 12 has a plurality of injection holes 12a that penetrate the circumferential portion inward and outward. The portion of the main body member 12 where the injection holes 12a are located protrudes from the lower surface of the cylinder head 13 toward the main combustion chamber 1.

[0027] The sub-chamber 11 is equipped with a first ignition device (JET spark plug) 20 that ignites the fuel mixture of gasoline and air. The electrodes of the first ignition device 20 face the space inside the sub-chamber 11. In addition, the main combustion chamber 1 is equipped with a second ignition device (SI spark plug) 30, separate from the first ignition device 20. The electrodes of the second ignition device 30 face the space inside the main combustion chamber 1. The selection of the first ignition device 20 and the second ignition device 30, and their ignition timing, are controlled by the control unit 51.

[0028] The control details of this invention will be explained below.

[0029] The control unit 51 selectively controls, based on atmospheric pressure information acquired by the environmental information acquisition means 53, to perform first ignition control, which involves ignition by the first ignition device 20 (JET ignition) and not ignition by the second ignition device 30 (SI ignition); second ignition control, which involves ignition by the second ignition device 30 (SI ignition) and not ignition by the first ignition device 20 (JET ignition); or third ignition control, which involves both ignition by the first ignition device 20 (JET ignition) and ignition by the second ignition device 30 (SI ignition) within the same combustion cycle. This allows for selective combination of ignition by the first ignition device 20 in the sub-chamber 11 and ignition by the second ignition device 30 in the main combustion chamber 1 (SI ignition), depending on the combustion state which changes in atmospheric pressure environments such as high altitudes, thereby increasing the degree of freedom in controlling the combustion state of the engine 10. In particular, actively performing JET ignition in the sub-chamber 11 is effective as a means of suppressing power reduction in low-pressure environments, because the ignited fuel rapidly propagates to the main combustion chamber 1 as a flamethrower.

[0030] Here, the control unit 51 performs first ignition control when the load of the engine 10 is less than a predetermined load threshold, and performs second ignition control when the load is above the predetermined load threshold. Furthermore, the control unit 51 sets the predetermined load threshold to the first predetermined load in a standard pressure environment where the atmospheric pressure information is above a predetermined value (or in a low-altitude environment where the elevation (altitude above sea level) is below a predetermined altitude), and performs first ignition expansion control which sets the predetermined load threshold to a lower load than the first predetermined load in a low-pressure environment where the atmospheric pressure information is below a predetermined value.

[0031] In this embodiment, under standard pressure conditions, as shown in Figure 4A, the second ignition control (corresponding to region B in the figure) is selected when the load of the engine 10 is less than the first predetermined load a, and the first ignition control (corresponding to region A in the figure) is selected when the load is equal to or greater than the first predetermined load a. Furthermore, under low pressure conditions, as shown in Figure 4B, the load that serves as the boundary between the second ignition control (corresponding to region B' in the figure) and the first ignition control (corresponding to region A' in the figure) is set to a second predetermined load a' which is lower than the first predetermined load a, instead of the aforementioned first predetermined load a. In other words, when first ignition expansion control is performed under low pressure conditions, the predetermined load threshold is lowered compared to the standard pressure conditions, and the second ignition control is selected when the load of the engine 10 is less than the second predetermined load a', and the first ignition control is selected when the load is equal to or greater than the second predetermined load a'.

[0032] In other words, in low-load regions where the output is too high with ignition by the first ignition device 20 (first ignition control), the system is designed to switch to ignition by the second ignition device 30 (second ignition control) to suppress shocks. In low-pressure environments, the range of first ignition control is extended to the low-load side compared to standard-pressure environments. As a result, even in high-altitude areas where the mass flow rate of air is lower than at sea level, the flame ejected from the sub-chamber 11 by JET ignition ensures a predetermined combustion speed, and consequently, the fuel in the main combustion chamber 1 burns more reliably.

[0033] In the embodiments shown in Figures 4A and 4B, a two-stage control system is used, where a predetermined load threshold under a standard pressure environment is set as the first predetermined load a, and a predetermined load threshold under a low pressure environment is set as the second predetermined load a'. However, it is also possible to use a control system that adjusts the predetermined load threshold in three or more steps, or continuously, according to the atmospheric pressure value under a low pressure environment. That is, as the atmospheric pressure falls below a predetermined value and the difference from that predetermined value increases, the predetermined load threshold may decrease in steps or continuously (the region in which the JET ignition occurs expands to the low-load side).

[0034] Here, the predetermined value of atmospheric pressure information that marks the boundary between the standard pressure environment and the low pressure environment can be set to, for example, the atmospheric pressure equivalent to an altitude of 1000m (approximately 900hPa), assuming that the atmospheric pressure at sea level (altitude 0m = near sea level) is 1 atmosphere (1013hPa ≈ approximately 1000hPa), where the atmospheric pressure is standard atmospheric pressure. This predetermined value can be changed as appropriate according to the specifications of the vehicle 60 and engine 10. For this reason, depending on the specifications, it is also conceivable that the predetermined value may be set to the atmospheric pressure equivalent to an altitude of 2000m (approximately 800hPa).

[0035] In this embodiment, in addition to the first ignition expansion control, third ignition control is selected in the high-speed, high-load region (corresponding to region D in Figure 4A) where the load of the engine 10 is greater than or equal to a first predetermined load a and the rotational speed of the engine 10 is greater than or equal to a first predetermined rotational speed e under standard pressure conditions. In this third ignition control in the high-speed, high-load region under standard pressure conditions, ignition by the first ignition device 20 is performed after ignition by the second ignition device 30 within the same combustion cycle, and the shock caused by JET ignition is mitigated by burning a portion of the fuel in the main combustion chamber 1 with SI ignition before performing JET ignition. However, under low pressure conditions, first ignition control is selected in the same high-speed, high-load region (corresponding to D' in Figure 4B). That is, under low pressure conditions, first ignition control is selected in the high-speed, high-load region where the load of the engine 10 is greater than or equal to a first predetermined load a and the rotational speed of the engine 10 is greater than or equal to a first predetermined rotational speed e, and the region that can be handled by JET ignition alone is extended to the high-load side.

[0036] This addresses the decrease in maximum output under low-pressure conditions by reducing heat loss and JET shock (combustion accompanied by shock caused by the propagation and collision of strong flames), thereby enhancing high-speed combustion (improved thermal efficiency) through JET ignition. As a result, under low-pressure conditions, the control range of the first ignition control, which uses only JET ignition, is set to extend to the high-speed, high-load side.

[0037] In this embodiment, as shown in FIG. 4A, as the high rotation high load region where the third ignition control is performed under the standard pressure environment, in addition to the load of the engine 10 being equal to or higher than the first predetermined load a, it is required that the load be equal to or higher than the third predetermined load f set higher than the first predetermined load a. The value of the third predetermined load f, which is the lower limit of the load for performing the third ignition control, can be adjusted in the region where the load is equal to or higher than the first predetermined load a.

[0038] Also, for the high rotation high load region under the standard pressure environment (corresponding to region D in FIG. 4A) and the high rotation high load region under the low pressure environment (corresponding to region D' in FIG. 4B), the rotational speed of the engine 10 is defined to be equal to or higher than the first predetermined rotational speed e. However, the value of this first predetermined rotational speed e may be set to be smaller as the load of the engine 10 is higher. In FIGS. 4A and 4B showing the embodiment, at the third predetermined load f, the high rotation high load regions shown in regions D and D' are set to have a first predetermined rotational speed e = e1 or higher. However, at the maximum allowable load g (f < g) of the engine 10, the high rotation high load region is set to have a first predetermined rotational speed e = e2 or higher (e2 < e1), reducing the boundary rotational speed. Also, between the rotational speed e1 and the rotational speed e2, the numerical value of the load changes linearly according to the load of the engine 10.

[0039] Here, the engine 10 of the embodiment includes a supercharger 15, and under the standard pressure environment, supercharging is performed when the load of the engine 10 is equal to or higher than a predetermined load boundary value. Also, during the first ignition expansion control under the low pressure environment, by lowering the predetermined load boundary value compared to the case under the standard pressure environment, the supercharging region is expanded to the low load side. That is, in the high load region under the standard pressure environment, the first ignition control using only JET ignition and supercharging are performed together, and under the low pressure environment, the lower limit of the supercharging use region is also moved to the low load side in accordance with the first ignition expansion control. That is, by the first ignition expansion control, in accordance with the decrease in the lower limit value of the load in the region of the first ignition control, the lower limit value of the load in the supercharging region is also decreased.

[0040] In this embodiment, a predetermined load threshold that serves as the boundary between the first ignition control and the second ignition control is set to a first predetermined load a under standard pressure conditions and a second predetermined load a' under low pressure conditions. In response to this, a predetermined load boundary value that serves as the boundary between the supercharged region and the naturally aspirated (NA) region is also set to match the first predetermined load a under standard pressure conditions and a second predetermined load a' under low pressure conditions. However, the predetermined load threshold that serves as the boundary between the first ignition control and the second ignition control and the predetermined load boundary value that serves as the boundary between the presence or absence of supercharging do not necessarily have to coincide, and the two may use different load values ​​under standard pressure conditions and low pressure conditions, respectively.

[0041] Furthermore, the predetermined load boundary value, which is the boundary between supercharging and non-supercharging, may be controlled to adjust in three or more steps or continuously, in accordance with the atmospheric pressure value in a low-pressure environment. In other words, as the atmospheric pressure falls below a predetermined value and the difference from that predetermined value increases, the predetermined load boundary value may decrease in steps or continuously (the supercharging region may expand to the low-load side).

[0042] Furthermore, in this embodiment, the first ignition expansion control is performed only in the region where the engine speed of 10 is set to a value lower than the first predetermined rotational speed e, and is above the second predetermined rotational speed c. In other words, the first ignition expansion control is not performed in the low rotational speed, low load region where a large output is not required, in an effort to reduce the likelihood of JET shock. In this low rotational speed, low load region, that is, the region where the load of the engine 10 is less than the first predetermined load a, and the engine speed is less than the second predetermined rotational speed c (corresponding to region C in Figure 4A and region C' in Figure 4B), it is desirable to select a third ignition control that uses both JET ignition and SI ignition. In this case, the ignition timing of JET ignition and SI ignition may be such that JET ignition is set after SI ignition, or both may be set simultaneously. It is also conceivable that JET ignition may be set before SI ignition.

[0043] As the first predetermined rotational speed e=e1, for example, 4000 rpm can be adopted, and as the second predetermined rotational speed c, for example, 2000 rpm can be adopted.

[0044] In the embodiments, the configuration of this invention was described using an engine 10 equipped with a supercharger 15 such as a turbocharger as an example, but this invention can also be applied to a naturally aspirated engine 10 that is not equipped with a supercharger 15.

[0045] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. Accordingly, the scope of the invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended. [Explanation of Symbols]

[0046] 1. Main combustion chamber 10. Engine (internal combustion engine) 11 Antechamber 20. First ignition system (JET spark plug) 30 Second ignition system (SI spark plug) 40 Fuel Injector 50 Electronic control units 51 Control Unit 53 Environmental information acquisition means 60 vehicles

Claims

1. An engine comprising a main combustion chamber, a sub-chamber adjacent to the main combustion chamber, a first ignition device facing the sub-chamber, and a second ignition device facing the main combustion chamber; an environmental information acquisition means for acquiring ambient pressure information; and a control unit for controlling ignition by the first and second ignition devices. The control unit can select a first ignition control in which the first ignition device ignites the engine when the engine load is below a predetermined load threshold and the second ignition device does not ignite it, and a second ignition control in which the second ignition device ignites the engine when the load is above the predetermined load threshold and the first ignition device does not ignite it, and the control unit performs a first ignition expansion control in which, under a standard pressure environment where the atmospheric pressure information is above a predetermined value, the predetermined load threshold is set to a first predetermined load, and under a low pressure environment where the atmospheric pressure information is below a predetermined value, the predetermined load threshold is set to a lower load than the first predetermined load.

2. The vehicle according to claim 1, wherein, under the standard pressure environment, if the engine load is greater than or equal to the first predetermined load and the engine speed is greater than or equal to the first predetermined rotational speed, a third ignition control is selected to perform ignition by the first ignition device and the second ignition device within the same combustion cycle, and under the low pressure environment, if the engine load is greater than or equal to the first predetermined load and the engine speed is greater than or equal to the first predetermined rotational speed, the first ignition control is selected.

3. The vehicle according to claim 1, comprising a supercharger for supercharging the intake air introduced into the engine, wherein under the standard pressure environment, supercharging is performed when the engine load is above a predetermined load boundary value, and when the first ignition expansion control is performed, the supercharging region is expanded to the low load side.

4. The vehicle according to claim 1, wherein the first ignition expansion control is performed when the engine speed is at or above a second predetermined speed that is lower than the first predetermined speed.

5. The vehicle according to claim 4, wherein, under the standard pressure environment and the low pressure environment, when the engine load is less than the first predetermined load and the engine speed is less than the second predetermined speed, a third ignition control is selected in which ignition is performed by the first ignition device and the second ignition device within the same combustion cycle.

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