JP2010043557A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform optimal gas flow control by correcting the homogeneity of a direct injection engine which is changed accompanied by variations machine difference and deterioration with time. <P>SOLUTION: This control device include a homogeneity detection means measuring or predicting the homogeneity of an air fuel mixture, a homogeneity comparison means comparing homogeneity obtained by the means measuring or predicting the homogeneity of the air fuel mixture and target homogeneity for each predetermined air fuel ratio, a torque detection means measuring or predicting torque generated by a direct injection engine, a torque comparison means comparing torque and target torque set for each predetermined operation zone, and a gas flow control means controlling the intensity of a gas flow. In the control devices, this gas flow control device using homogeneity measurement is characterized by intermittently or continuously gas flow control means based on homogeneity detected by the homogeneity detection means, torque or control target value of the gas flow control means set for each operation zone. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device that controls gas flow in an internal combustion engine.

  In the conventional technology, as described in Patent Document 1, it is described that the catalyst purification rate is calculated from the exhaust gas components detected from the exhaust gas sensor before and after the catalyst, and the gas flow is controlled based on the catalyst purification rate. ing. In addition, in general internal combustion engines as well as in-cylinder direct-injection gasoline engines, it is known to improve output performance and fuel consumption performance by uniformly mixing the air-fuel mixture formed by fuel and air. Yes. The degree of uniform mixing of the air-fuel mixture is defined as homogeneity, and the higher the degree of homogeneity, the better the degree of mixing. As a means of improving the homogeneity, SCV (Swirl Control Valve) or TGV (Tumble Generated) which strengthens the flow of air (gas flow) sucked into the combustion chamber and actively uses swirl flow or tumble flow, etc. A gas flow control valve represented by a valve) or the like is known. In general, the gas flow control valve performs control based on the operating state of the engine (engine rotational speed and intake pipe pressure). This is because the homogeneity is improved by strengthening the gas flow, but at the same time, the gas flow control valve closes the intake path, so that the amount of air sucked into the cylinder is reduced. That is, it can be said that the output characteristics are determined by the difference between the improvement in homogeneity and the loss in the amount of air sucked into the cylinder.

JP-A-9-195816

  However, in the conventional method, the homogeneity is not always the same even with the same gas flow strength due to machine difference variation and deterioration with time. That is, considering factors including environmental changes (temperature, engine water temperature, fuel gasoline properties, etc.), it cannot be said that gas flow control for obtaining a desired homogeneity is performed in the conventional method.

  An object of the present invention is to improve engine output performance and exhaust performance by improving homogeneity.

  The present invention for solving the above problems is a control device for an internal combustion engine provided with a gas flow control device for controlling the strength of gas flow, a homogeneity detection means for measuring or predicting the homogeneity of an air-fuel mixture, and a homogeneity A homogeneity comparison means for comparing the homogeneity obtained from the degree detection means with a target homogeneity for each preset air-fuel ratio, and a gas flow control means for controlling the gas flow control device. The control device is characterized in that the gas flow control means is intermittently or continuously controlled based on the detected homogeneity.

  According to the present invention, engine output performance and exhaust performance can be improved.

  Examples of the present invention will be described below.

  FIG. 1 and FIG. 2 are configuration diagrams relating to the first embodiment of the present invention. In the present embodiment, a multi-cylinder engine is mainly assumed. In the following drawings, one cylinder will be described for the sake of simplicity. Further, description will be made using an oxygen concentration sensor that detects an oxygen concentration remaining in the exhaust gas (hereinafter referred to as residual oxygen concentration) as the homogeneity detection means, and TGV as the gas flow control means. Here, the homogeneity detection means may be any means that can measure not only the residual oxygen concentration remaining in the exhaust gas, but also an item having a correlation with the homogeneity such as carbon monoxide concentration or exhaust temperature. It is only necessary to be able to grasp the homogeneity of the air-fuel mixture whether it is target or indirect.

  Air in the atmosphere is sucked from the intake passage (102) into the combustion chamber (111) via an air filter (not shown). Further, an air flow sensor (103) for measuring the amount of intake air and an electric throttle valve (104) for adjusting the amount of intake air are provided in the intake path (102), and the control unit (201) is provided with intake air. The amount is calculated and the electric throttle valve (104) is controlled. On the downstream side of the electric throttle valve (104), a TGV (107) that is a gas flow control valve and a partition plate (108) are provided, and an auxiliary intake having an outlet opened in the vicinity of the intake valve (109). By providing the passage, a tumble flow can be generated in the air sucked into the combustion chamber (111). At this time, in order to control the formation of the gas flow, it is necessary to control the amount of air supplied from the auxiliary intake passage, and using the TGV (107), the amount of air supplied from the original intake path (102) The ratio can be controlled. On the other hand, the fuel is sent from a fuel tank (not shown) to a high-pressure fuel pump (119) by a lift pump (not shown) that pumps up the fuel, and after being pressurized by the high-pressure fuel pump (119), the gallery (120) And is directly injected into the combustion chamber (111) by the fuel injection valve (122). The injection amount at this time is determined by the intake air amount and the target air-fuel ratio preset in the control unit (201). In addition, the gallery (120) is provided with a fuel pressure sensor (121) for measuring the fuel pressure in the gallery, and the high pressure fuel pump is controlled by the control unit (201) so as to obtain an appropriate fuel pressure. The air sucked into the combustion chamber (111) and the fuel injected from the fuel injection valve (122) become an air-fuel mixture that is easily combusted in the fuel chamber (111), and the control unit (201) has an appropriate ignition timing. The ignition signal is calculated and output to the ignition coil (123). The ignition signal boosted by the ignition coil (123) is ignited by the spark plug (124), and the air-fuel mixture is combusted in the combustion chamber (111) and then discharged into the exhaust path (125) as exhaust gas. Further, the exhaust path (125) is provided with a catalyst (127), and the exhaust gas purified by the catalyst (127) is again opened to the atmosphere. Since the catalyst (127) has a ratio of air and fuel (hereinafter referred to as air-fuel ratio) that can draw the purification capacity to the maximum source, the control unit (201) is provided with an oxygen concentration sensor provided upstream of the catalyst (127). Based on the air-fuel ratio information from (126), so-called feedback control is performed between the air-fuel ratio target values. Further, an upstream side of the catalyst (127) is provided with an oxygen concentration sensor (126) serving as a homogeneity detection means, which detects the residual oxygen concentration. Due to the pressure in the combustion chamber (111) (hereinafter referred to as combustion pressure) generated by the combustion, a force that pushes the piston (112) downward acts on the crankshaft (not shown) via the connecting rod (113). It is transmitted and converted into rotational motion, which becomes engine output. A combustion pressure sensor (not shown) for measuring the combustion pressure is used as torque detection means (128). The combustion crankshaft (not shown) is provided with a flywheel (114) so that the rotational motion is smoothly performed, and the crank angle sensor (115) detects an edge provided on the outer periphery of the flywheel. The rotational force of the crankshaft (not shown) is transmitted to the camshafts (117a, 117b) above the engine body (101) by a belt, a chain, etc., and the camshaft also rotates. The position and number of camshafts differ depending on the engine configuration. In this figure, the camshaft is provided at the top of the engine body (101), and the so-called double overhead cam type (DOHC) with separate camshafts for intake and exhaust. The direct injection engine is shown. The intake valve (109) corresponding to the shape of the elliptical cam (117a) provided on the camshaft (not shown) obtains movement characteristics. Similarly, an exhaust cam (117b) is provided, and similarly, the exhaust valve (110) obtains a movement characteristic corresponding to the shape of the exhaust cam. Similar to the crankshaft, the control unit detects the rotation of the camshaft by the cam angle sensors (116a, 116b).

  Next, the control unit (201) will be described. The main part is composed of an MPU (202), an EP-ROM (203), a RAM (204), an I / O LSI (205) including an A / D converter, and the like. From the crankshaft crank angle sensor (115), cam angle sensors (116a, 116b), etc., the control unit (201) calculates the engine speed, ignition timing, and the like. The control unit (201) operates the electric throttle valve (104) from the position information of an accelerator opening sensor that detects the opening degree of an accelerator petal (not shown) operated by the driver, and the electric throttle valve (104 Since the correction can be made by grasping the position of the electric throttle valve (104) by means of the throttle opening sensor (105) for detecting the opening of), precise control is possible. The control unit (201) uses the air flow sensor (103) to obtain a current intake air amount and then calculates an appropriate fuel injection time in combination with the engine speed and the like, and sends a pulse signal to the fuel injection valve (122). Send. The fuel injection valve (122) performs fuel injection by opening and closing the needle in the fuel injection valve based on the pulse signal. For the ignition system, the control unit (201) outputs an optimal ignition timing, which varies depending on the engine operating conditions, as an ignition signal to the ignition coil (123), and the ignition signal is boosted by the ignition coil (123) and the ignition plug ( 124). Based on the information detected by the homogeneity measuring means (223) represented by the oxygen concentration sensor for detecting the residual oxygen concentration, the control unit indirectly grasps the homogeneity. Further, the gas flow control means (107) is controlled based on the homogeneity information and the torque from the torque detector.

  FIG. 3 is a graph showing the relationship between homogeneity, filling efficiency, and torque. This figure is only a graph, and the relationship described depends on the engine used and the operating conditions (in the figure, the operating conditions and the air-fuel ratio are fixed). . The horizontal axis indicates the strength of gas flow, and the vertical axis indicates the torque (301), filling efficiency (302), and homogeneity (303) from the top. When the homogeneity is poor, the homogeneity improves when the gas flow is increased. However, even if the gas flow is increased, the improvement in homogeneity gradually decreases. If it exceeds 305), even if the gas flow is strengthened, the homogeneity is not improved any more. The filling efficiency (302) has a characteristic of decreasing when the gas flow is strengthened, and shows a significant decrease at a certain point (304 in the figure). The torque is improved up to the point where the homogeneity (303) is improved and the decrease in the filling efficiency (302) is small (306 in the figure), but when the filling efficiency (302 in the figure) starts to drop significantly. The torque starts ignition (307) by the balance of the improvement in homogeneity and the reduction in filling efficiency. Further, it can be seen that when the filling efficiency starts to greatly decrease in a state where the degree of improvement in homogeneity is lost, the torque (301) further decreases significantly. As described above, 305 and 304 in the figure change the relationship with the gas flow strength depending on the operation region. Specifically, when the operation region becomes a high load or a high rotation, 305 and 304 move to the left side in the figure. This is due to the fact that the flow rate of air increases as the amount of air sucked into the combustion chamber increases.

  FIG. 4 is a graph showing the relationship between the residual oxygen concentration and the homogeneity as one of means for measuring the homogeneity. The vertical axis represents the concentration of residual oxygen, and the horizontal axis represents the air-fuel ratio. 401 is a graph in which the air-fuel ratio is changed at an ideal homogeneity. That is, the ideal value of the residual oxygen concentration is shown. When the air-fuel ratio is rich, oxygen in the air-fuel mixture is insufficient regardless of the homogeneity, so that the residual oxygen concentration is infinitely close to 0. The oxygen concentration in the air-fuel mixture increases when the stoichiometric air-fuel ratio of 14.7 is slightly reduced, and the oxygen concentration increases even when the ideal homogeneity is maintained. 402 is the residual oxygen concentration when the homogeneity is low. If the degree of homogeneity is low, the air-fuel mixture has unevenness, so that oxygen in the air-fuel mixture cannot be combusted and is mixed with other exhaust gas components and discharged from the combustion chamber. For this reason, compared to 401, 402 has a higher residual oxygen concentration overall. The control contents of the gas flow in the first embodiment of the present invention will be described using this characteristic. In addition, although it demonstrated using residual oxygen concentration here, the same effect can be acquired even if it uses the component in other exhaust gas, and a combustion rate will become quick, when a homogeneity improves further. From the characteristics, control using the exhaust temperature may be performed. Other exhaust gases include carbon monoxide concentration in addition to oxygen concentration.

  FIG. 5 is a flowchart according to the first embodiment of the present invention. First, the control flow according to the present invention will be described. The control in Embodiment 1 of the present invention is roughly divided into the control of S517, S518, and S519. S517 is conventional gas flow control, and performs gas flow control based on the operation region. In S518, when it is determined that the homogeneity is equal to or less than the target homogeneity and the gas flow is too strong for some reason not caused by the homogeneity during steady operation, control is performed to weaken the gas flow. In S519, the gas flow is controlled based on the homogeneity. The flow of control will be described in detail. In S501, the target homogeneity is read. In this embodiment, an oxygen concentration sensor is used as the homogeneity detecting means, and the residual oxygen concentration is detected in advance. The target residual oxygen concentration for each air-fuel ratio (hereinafter referred to as target oxygen concentration) is read based on the current air-fuel ratio. In S502, torque is detected from the output torque detection means. In S503, it is determined whether or not the operation region of the direct injection engine has been changed. When the operation region has been changed, the target torque set in advance for each operation region in S504 is searched based on the current operation region. In S505, the control value of the gas flow control means set in advance for each operation range is searched, and the gas flow control means is controlled based on the control value searched in S505 in S506. After that, in S511, the torque detected in S502 is compared with the target torque searched in S504. In S512, the torque detected in S502 is stored as the previous torque. In S513, a residual oxygen concentration is detected from an oxygen concentration sensor which is a homogeneity detection means. In S514, the residual oxygen concentration detected in S513 is compared with the target oxygen concentration read in S401. If it is determined that the residual oxygen concentration is higher than the target oxygen concentration, the control value of the gas flow control means is further set in S515. Control to increase gas flow. Conversely, if the target oxygen concentration and the residual oxygen concentration are approximate values in S514, it is determined that the gas flow is too strong (position 307 in FIG. 3), and in S516, the control value of the gas flow control means is set to gas. Control the flow to weaken. On the other hand, if it is determined in S503 that the operation region is constant, that is, it is a steady operation, S507 compares the previous torque stored in S502 with the torque detected in S502 in S512 or S509. If the torque is higher than the previous torque, the control proceeds to S511. If the torque is not higher than the previous torque, it is further determined in S508 whether the torque is lower than the previous torque. If the torque is lower than the previous torque, the torque detected in S502 is stored as the previous torque as in S412, and the control value of the gas flow control means is controlled in S510 so that the gas flow becomes weaker.

  FIG. 6 is a timing chart showing the basic operation in the first embodiment of the present invention, and relates to the contents up to S515 in FIG. The horizontal axis in the figure is the elapsed time, the left side indicates the past, and the dotted line 613 indicates the present. The graph shows target torque (611), torque detected from torque detection means (601), filling efficiency (602), residual oxygen concentration (603), target oxygen concentration (612), homogeneity (604), TVG from the top. Write control position (605). First, via S517, when the control unit (201) determines that the current torque (601) is insufficient with respect to the target torque (611) (S511), the current residual oxygen concentration (603) is detected. Then, the target oxygen concentration (603) is compared. When the residual oxygen concentration is higher than the target oxygen concentration, the control unit determines that the degree of homogeneity is insufficient, and in S515, controls the control position of the TGV that is the gas flow control means so that the gas flow becomes stronger. Thereafter, in the so-called steady operation in which there is no change in the operation region, the above control is repeated through S507 until the torque becomes close to the target torque or until the residual oxygen concentration becomes close to the target oxygen concentration. In the figure, since the torque is close to the target torque at 614 (615), the control position of the TGV which is the gas flow control means is kept constant (616). After that, since the previous torque and the current torque are the same in S507, the current TGV control position is made constant, so the torque is always constant. As a supplementary explanation, when the control position of TGV is further increased from 614 (610), the charging efficiency (607), residual oxygen concentration (608), and homogeneity (609) show the dotted lines shown in the figure, and as a result, torque ( 606) will fall. When the operation region is changed, regardless of the current control position of the TGV, the control position of the TGV set for each operation region is set according to the control of S517, and then the above control is performed. Further, when the torque is lower than the target torque and the residual oxygen concentration is close to the target oxygen concentration, it is determined that the torque is on the dotted line 606, so that the gas flow is weakened at the control position of the TGV by S516. Control.

  FIG. 7 is determined that there is no abnormality in engine control with respect to FIG. 6, and even if the control is continued to increase the gas flow, the torque does not reach the target torque, and as a result, the gas flow becomes too strong. It is a figure showing the situation where torque (701) does not reach the target torque (711) because the charging efficiency is significantly reduced. After timing 714, there is a sufficient improvement in homogeneity (709), and the charging efficiency does not show a significant decrease (707), but even if the TGV control position becomes stronger after timing 714, the torque does not increase. The torque does not reach the target torque, and the torque drops to a peak at 715. In this case, the control shifts from S507 to S508. If the previous torque is equal to the torque, the position of the TGV is maintained. If the previous torque is higher than the torque, the gas flow is weakened at the control position of the TGV. The torque is always controlled to be the highest.

  Of course, it goes without saying that the residual oxygen concentration and the target torque, which are the target homogeneity in the first embodiment of the present invention, have hysteresis, and the previous torque or the homogeneity with respect to the control amount of the gas flow control means. If the sensitivity of the residual oxygen concentration that is the detection means is extremely low, a method such as slowing the update frequency may be used, and the learning value is provided for the target torque or target homogeneity to improve control accuracy. A method may also be used.

  As a result, it is possible to correct the gas flow control for the uniformity variation due to the machine difference variation, and it is possible to cope with the aging deterioration and the change in the use environment which are difficult to predict. Direct injection engines will always be controlled with good homogeneity.

The whole block diagram of a direct-injection engine. The block diagram of a control unit (ECU). Graph of relationship between homogeneity, filling efficiency and torque. Graph of the relationship between residual oxygen concentration and homogeneity. The flowchart in Example 1 of this invention. 1 is a timing chart 1 in Embodiment 1 of the present invention. 2 is a timing chart 2 in Embodiment 1 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Engine main body 102 Intake path 103 Air flow sensor 104 Electrically controlled throttle valve 105 Throttle opening sensor 106 Collector 107 TGV (tumble generated valve)
108 Partition plate 109 Intake valve 110 Exhaust valve 111 Combustion chamber 112 Piston 113 Connecting rod 114 Flywheel 115 Crank angle sensor 116a Intake cam 116b Exhaust cam 117 Cam angle sensor 118 Fuel path 119 High pressure fuel pump 120 Gallery 121 Fuel pressure sensor 122 Fuel injection Valve (Injector)
123 ignition coil 124 spark plug 125 exhaust path 126 oxygen concentration sensor 127 catalyst 223 homogeneity measuring means

Claims (11)

A control device for an internal combustion engine comprising a gas flow control device for controlling the strength of gas flow,
The control device includes:
A homogeneity estimation means for measuring or predicting the homogeneity of the mixture,
Gas flow control means for controlling the gas flow control device,
A control apparatus for controlling a gas flow control means based on the homogeneity detected by the homogeneity detection means. The control device includes:
A homogeneity comparison means for comparing the homogeneity obtained from the homogeneity estimation means with a target homogeneity for each preset air-fuel ratio;
The gas flow control device controls the gas flow control device so that the homogeneity obtained from the homogeneity estimation means approaches the target homogeneity. A control device for an internal combustion engine comprising a gas flow control device for controlling the strength of gas flow,
The control device includes:
Output torque estimating means for measuring or predicting output torque output from the internal combustion engine;
Torque comparison means for comparing the output torque with a target torque set in advance for each operation region;
A homogeneity estimation means for measuring or predicting the homogeneity of the mixture,
Gas flow control means for controlling the gas flow control device;
With
The gas flow control means includes
A control device that controls the gas flow control device so that the output torque approaches the target torque based on the homogeneity detected by the homogeneity detection means and the target torque.   4. The control device according to claim 3, wherein when the output torque is lower than the target torque and it is determined that the homogeneity detected from the homogeneity estimation means is lower than the vicinity of the target homogeneity, the control of the gas flow control means is performed. A control device for controlling the value so that the gas flow becomes stronger.   4. The control device according to claim 3, wherein when the output torque is lower than the target torque and it is determined that the homogeneity detected from the homogeneity estimation means is close to the target homogeneity, the gas flow control means A control device that controls the control value so that the gas flow becomes weak.   4. The control device according to claim 3, wherein when the operation region of the internal combustion engine is changed, the gas flow control unit is controlled based on a control target value of the gas flow control unit set for each operation region. A control device characterized by.   4. The control device according to claim 3, further comprising means for comparing the previous measured or calculated previous torque with the current measured or calculated current torque, wherein the gas flow control is performed when the operating range of the internal combustion engine is steady. When the control value of the means is controlled to increase the gas flow, but the previous torque is determined to be higher than the current torque, the control amount of the gas flow control means is controlled to weaken the gas flow. A control device characterized by.   2. The control device according to claim 1, wherein the homogeneity estimating means is a means for directly or indirectly detecting at least one selected from an oxygen concentration, a carbon monoxide concentration, and an exhaust gas temperature remaining in the exhaust gas. Control device characterized.   4. The control device according to claim 3, wherein as the means for measuring or predicting the output torque, a torque sensor capable of detecting the output torque, a combustion pressure sensor capable of measuring a combustion pressure in a cylinder, or the A control device comprising at least one means for predicting the output torque from an intake air amount of an internal combustion engine, an engine rotation speed, and the like.   2. The control device according to claim 1, wherein the gas flow control means includes at least one of a swirl control valve, a tumble generated valve, and a variable valve that can change a moving characteristic of the intake valve. Control device.   2. The control device according to claim 1, wherein during the start retard control, the start retard control is performed by a homogeneity that can promote combustion in the exhaust passage.

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