JP5708393B2 - Engine control system - Google Patents

Description

  The present invention relates to an engine control system, and more particularly to an engine control system including an operating angle variable mechanism that can change an operating angle while keeping the maximum lift amount of an exhaust valve constant.

  2. Description of the Related Art A variable valve mechanism that makes valve characteristics of an intake valve and an exhaust valve included in an engine variable is known. For example, in Patent Document 1, the first variable valve mechanism that can change the lift amount of the exhaust valve, the second variable valve mechanism that can change the phase of the exhaust valve, and the first and second when an engine brake is requested. There is disclosed a variable valve operating apparatus for an engine having control means for controlling the operation of the variable valve operating mechanism. Patent Document 1 discloses that the engine braking force can be changed by this variable valve operating device.

In Patent Document 2, a flange portion provided on a drive shaft that rotates in synchronization with the rotation of the engine and formed with an engagement groove along the radial direction, and an engagement groove provided on the camshaft and along the radial direction. The internal combustion engine includes a flange portion formed with an annular disc and an annular disc engaged with the flange portion via a pin, and the valve lift characteristics of the intake and exhaust valves are variably controlled by decentering the center of the annular disc. A valve device is disclosed.

  In Patent Document 3, a cam shaft including an outer cam shaft and an inner cam shaft, and a first phase control mechanism and a second phase control mechanism provided at both shaft end portions of the cam shaft, the relative relationship between the outer cam shaft and the inner cam shaft are provided. A valve operating device capable of changing a general phase is disclosed. Patent Document 4 discloses a variable working angle mechanism in which the lift amount is enlarged / reduced in accordance with the expansion / reduction of the working angle when the working angle of the intake valve is made variable.

JP 2008-157195 A JP 2006-336659 A JP 2009-144521 A JP 2005-299594 A

  By the way, an exhaust system of the engine may be provided with a back pressure adjusting device capable of adjusting the back pressure. The back pressure adjusting device is used to increase the engine braking force, for example, by increasing the back pressure generated in the exhaust system. On the other hand, the back pressure adjusting device can increase the back pressure generated in the exhaust system, thereby generating exhaust blowback into the engine cylinder and the intake passage. And the fall of in-cylinder temperature can also be suppressed by making internal EGR gas amount increase by this. For this reason, the back pressure adjusting device is also used to promote warm-up, for example, by increasing the back pressure during engine warm-up.

  However, when the back pressure adjusting device is used for promoting warm-up, depending on the valve characteristics of the exhaust valve, there is a possibility that the opening area of the exhaust port required for exhaust blowback cannot be secured sufficiently. Specifically, for example, when the valve timing of the exhaust valve is fixed, there is a possibility that the opening area of the exhaust port cannot be sufficiently secured as a result of obtaining the valve timing considering the entire engine operation. In this respect, in order to sufficiently generate exhaust blowback, for example, it is conceivable to set a large overlap amount of the intake and exhaust valves. However, in this case, for example, the engine performance during high-load operation may deteriorate.

  In view of the above problems, an object of the present invention is to provide an engine control system that can favorably promote warm-up using a back pressure adjusting device.

The present invention while the maximum lift amount of the exhaust valve provided in the engine constant, and can change the duration change mechanism operating angle, an adjustable back pressure regulator back pressure occurring in the exhaust system of the engine, the a phase capable of changing phase variable mechanism of the exhaust valve, during the warm-up of the engine, to control the back pressure regulator so as to increase the back pressure generated in the exhaust system of the engine, working angle of the exhaust valve An engine control system comprising: a control unit that controls the variable working angle mechanism so as to enlarge the phase and controls the variable phase mechanism so as to retard the phase of the exhaust valve .

In the present invention, when the control unit controls the phase variable mechanism to retard the phase of the exhaust valve, the exhaust valve is within a range in which interference between a piston included in the engine and the exhaust valve does not occur. The phase variable mechanism can be controlled so as to delay the phase as much as possible .

  ADVANTAGE OF THE INVENTION According to this invention, warming-up promotion using a back pressure adjustment apparatus can be aimed at suitably.

1 is an overall configuration diagram of Example 1. FIG. 1 is a schematic configuration diagram of an engine according to Embodiment 1. FIG. It is explanatory drawing of the valve timing of Example 1. FIG. It is a figure which shows a 1st control operation with a flowchart. It is explanatory drawing of the blowback of exhaust_gas | exhaustion. It is explanatory drawing of the working angle variable upper limit of a working angle variable mechanism. It is the 1st comparison figure of a working angle variable upper limit. It is the 2nd comparison figure of a working angle variable upper limit. FIG. 6 is an overall configuration diagram of Embodiment 2. It is explanatory drawing of the valve timing of Example 2. FIG. It is a figure which shows a 2nd control operation with a flowchart. It is a figure which shows the variable upper limit of the working angle and retard amount of an exhaust valve.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall configuration diagram of the first embodiment. FIG. 2 is a schematic configuration diagram of the engine 50A. As shown in FIG. 1, the intake system 10 supplies intake air to the engine 50A. The exhaust system 20 circulates exhaust discharged from the engine 50A. The exhaust system 20 is provided with a supercharger 30 and a back pressure control valve 40. The supercharger 30 is an exhaust-driven supercharger, and specifically, the exhaust system 20 is provided with a turbine portion of the supercharger 30. The back pressure control valve 40 changes the throttle degree of the exhaust passage by changing the opening degree. The back pressure adjustment valve 40 corresponds to a back pressure adjustment device that can adjust the back pressure generated in the exhaust system 20.

  The engine 50A is a compression ignition type internal combustion engine (diesel engine), and includes a plurality (four in this case) of cylinders 51a. In this regard, intake air is distributed and supplied from the intake system 10 to each cylinder 51a, and exhaust from each cylinder 51a is discharged to the exhaust system 20. The engine 50 </ b> A includes a fuel injection valve 56 and a variable operating angle mechanism 57. The fuel injection valve 56 is provided for each cylinder 51a. The operating angle variable mechanism 57 is provided across the plurality of cylinders 51a.

  The back pressure adjusting device may be, for example, a variable capacity supercharger including a variable nozzle vane that makes the cross-sectional area of the flow path for introducing the exhaust gas variable. In this regard, the supercharger 30 can be a back pressure adjusting device by using the supercharger 30 instead of the back pressure adjusting valve 40 as the supercharger.

  As shown in FIG. 2, the engine 50 </ b> A includes a cylinder block 51, a cylinder head 52, a piston 53, an intake valve 54, and an exhaust valve 55 in addition to the fuel injection valve 56 and the operating angle variable mechanism 57. A cylinder 51 a is formed in the cylinder block 51. A piston 53 is accommodated in the cylinder 51a. A cylinder head 52 is fixed to the upper surface of the cylinder block 51. The combustion chamber E is formed as a space surrounded by the cylinder block 51, the cylinder head 52 and the piston 53.

  The cylinder head 52 is formed with an intake port 52a and an exhaust port 52b. An intake valve 54 and an exhaust valve 55 are provided. The intake port 52 a guides intake air to the combustion chamber E, and the exhaust port 52 b discharges gas from the combustion chamber E. The intake valve 54 opens and closes the intake port 52a, and the exhaust valve 55 opens and closes the exhaust port 52b. Two intake valves 54 and two exhaust valves 55 are provided for each cylinder. Specifically, the fuel injection valve 56 is provided in the cylinder head 52 with an injection hole protruding from the center upper portion of the combustion chamber E.

  Specifically, the operating angle variable mechanism 57 is provided for the exhaust valve 55. The working angle variable mechanism 57 is a working angle variable mechanism that can change the working angle while keeping the maximum lift amount of the exhaust valve 55 constant. For example, as disclosed in Patent Document 2 described above, the working angle variable mechanism 57 includes an eccentric member (annular disk) that makes the cam speed variable by decentering the center between the drive shaft and the cam shaft. Can be applied. The operating angle variable mechanism 57 similarly changes the operating angle of each of a plurality of (here, two) exhaust valves 55 provided for each cylinder 51a.

  FIG. 3 is an explanatory diagram of the valve timing of the first embodiment. As shown in FIG. 3, the operating angle (valve opening period) of the exhaust valve 55 is enlarged or reduced by the operating angle variable mechanism 57 around the crank angle corresponding to the center of the valve opening period. The valve timings of the intake / exhaust valves 54 and 55 are set so that the overlap amount of the intake / exhaust valves 54 and 55 is increased by increasing the operating angle of the exhaust valve 55.

  Returning to FIG. 1, the ECU 1 </ b> A is an electronic control device, and the back pressure control valve 40, the fuel injection valve 56, and the operating angle variable mechanism 57 are electrically connected as control objects to the ECU 1 </ b> A. The ECU 1A is electrically connected to a sensor group 70 for detecting the operating state of the engine 50A. The sensor group 70 includes, for example, an accelerator opening sensor that can detect an accelerator pedal depression amount (accelerator opening) for making an acceleration request to the engine 50A, a crank angle sensor that can detect the rotational speed NE of the engine 50A, an engine A water temperature sensor capable of detecting a cooling water temperature of 50A is included.

  The ROM is configured to store a program describing various processes executed by the CPU, map data, and the like. Various functions are realized in the ECU 1A by executing processing while the CPU uses a temporary storage area of the RAM as needed based on a program stored in the ROM. In this regard, in the ECU 1A, for example, the following control unit is functionally realized.

  The control unit controls the back pressure adjustment valve 40 so as to increase the back pressure generated in the exhaust system 20 when the engine 50A is warmed up, and controls the working angle variable mechanism 57 so as to increase the working angle of the exhaust valve 55. . In controlling the back pressure control valve 40 so as to increase the back pressure, the control unit specifically controls the back pressure adjustment valve 40 so as to throttle the exhaust passage rather than the fully opened state. Further, in controlling the operating angle variable mechanism 57 so as to increase the operating angle of the exhaust valve 55, the control unit specifically operates so as to increase the operating angle of the exhaust valve 55 rather than the operating angle of the intake valve 54. The angle variable mechanism 57 is controlled.

  In controlling the back pressure control valve 40 and the operating angle variable mechanism 57, the control unit specifically controls the back pressure based on the engine operating state (specifically, the accelerator opening, the rotational speed NE, and the cooling water temperature here). The opening degree of the valve 40 (the throttle degree of the exhaust passage) and the operating angle control state of the operating angle variable mechanism 57 are calculated, and the back pressure control valve 40 is adjusted so that the opening degree of the back pressure control valve 40 becomes the calculated opening degree. In addition to controlling, the operating angle variable mechanism 57 is controlled so that the operating angle control state becomes the calculated operating angle control state. For example, a fuel injection amount may be applied to the engine operating state instead of the accelerator opening.

  In calculating the opening degree of the back pressure control valve 40 and the operating angle control state of the operating angle variable mechanism 57, the control unit specifically detects the engine operating state, and the opening degree and operating angle of the back pressure control valve 40. The operating angle control state of the variable mechanism 57 is referred to each map data determined in advance according to the engine operating state, and the opening degree of the back pressure control valve 40 and the operating angle of the operating angle variable mechanism 57 corresponding to the detected engine operating state. By reading the control state, the opening degree of the back pressure control valve 40 and the operating angle control state of the operating angle variable mechanism 57 are calculated. In these map data, the opening degree of the back pressure control valve 40 and the operating angle control state of the operating angle variable mechanism 57 to be realized according to the engine operating state are set in advance. These map data are created with the goal of achieving the shortest warm-up completion time without degrading the fuel consumption as much as possible.

  In this embodiment, an engine control system (hereinafter simply referred to as a control system) 100A including a back pressure control valve 40, a working angle variable mechanism 57, and an ECU 1A is realized.

  Next, the operation of the ECU 1A as the first control operation will be described with reference to the flowchart shown in FIG. The ECU 1A detects the engine operating state (step S1). Specifically, in step S1, the accelerator opening, the rotational speed NE, and the coolant temperature are detected. Subsequently, the ECU 1A determines whether or not the coolant temperature is lower than a predetermined value α (step S2). The predetermined value α is 40 ° C., for example, and when the coolant temperature is lower than the predetermined value α, it is determined that the engine 50A is warming up. If a negative determination is made in step S2, this flowchart is terminated.

  On the other hand, if the determination in step S2 is affirmative, the ECU 1A calculates the opening degree of the back pressure control valve 40 to be realized and the operating angle control state of the operating angle variable mechanism 57 based on the detected engine operating state (step S3A). . Then, the back pressure control valve 40 and the operating angle variable mechanism 57 are controlled so as to be in the calculated opening degree and operating angle control state (step S4A). After step S4A, the process returns to step S2. As a result, the back pressure control valve 40 is controlled to increase the back pressure and the working angle of the exhaust valve 55 is increased until the coolant temperature reaches the predetermined value α when the engine 50A is warmed up. The angle variable mechanism 57 is controlled.

  Next, the function and effect of the control system 100A will be described. FIG. 5 is an explanatory diagram of exhaust blowback. The control system 100A controls the back pressure adjustment valve 40 so as to increase the back pressure when the engine 50A is warmed up. For this reason, the control system 100A can generate exhaust blowback from the exhaust system 20 into the cylinder 51a of the engine 50A. In addition, the control system 100A controls the operating angle variable mechanism 57 so as to increase the operating angle of the exhaust valve 55 when the engine 50A is warmed up, so that the opening area of the exhaust port 52b required for exhaust blowback is also increased. It can be secured. As a result, the amount of internal EGR gas can be increased by increasing the exhaust blowback amount. For this reason, the control system 100A can favorably promote warm-up using the back pressure adjustment valve 40.

  In the control system 100A, the valve timings of the intake / exhaust valves 54, 55 are set so that the overlap amount of the intake / exhaust valves 54, 55 is increased by increasing the operating angle of the exhaust valve 55. For this reason, the control system 100A can increase the exhaust blow-back amount even by increasing the overlap amount of the intake / exhaust valves 54, 55, thereby favorably promoting the warm-up by increasing the internal EGR gas amount. Can be planned.

  In order to increase the overlap amount, the control system 100A is preferable in the following points. FIG. 6 is an explanatory diagram of the working angle variable upper limit of the working angle variable mechanism 57. As shown in FIG. 6, the valve stamp (interference between the piston 53 and the exhaust valve 55) generation region R is formed so that the valve stamp is generated with a smaller lift amount as the phase is on the retarded side. In this respect, the working angle variable upper limit of the working angle variable mechanism 57 is set from the viewpoint of avoiding the valve stamp, in addition to the factors caused by the structure of the working angle variable mechanism 57 itself. In the variable operating angle mechanism 57 that can change the operating angle while keeping the maximum lift amount of the exhaust valve 55 constant, the rising and falling of the lift amount become gentle as the operating angle increases. The operating angle can be expanded within a range where no valve stamp is generated.

  FIG. 7 is a first comparison diagram of the working angle variable upper limit. FIG. 8 is a second comparison diagram of the upper limit of the operating angle variable. In FIG. 7, the working angle variable upper limit is compared between the working angle variable mechanism 57 and the working angle variable mechanism in which the lift amount is enlarged / reduced in accordance with the expansion / reduction of the operating angle (case 1). ing. In FIG. 8, in the case of the variable operating angle mechanism 57 and the valve gear that includes a cam shaft composed of an outer cam shaft and an inner cam shaft and can change the relative phase between the outer cam shaft and the inner cam shaft (case 2). ) And the working angle variable upper limit are compared. In case 2, the variable upper limit of the combined operating angle (the valve opening period as a whole when only one of the two exhaust valves 55 is retarded) is the operating angle variable upper limit.

  As shown in FIG. 7, in case 1, the lift amount increases as the operating angle increases. Therefore, in this case, if the operating angle is increased, a valve stamp is generated when the lift amount is decreased. As a result, the amount of overlap of the intake / exhaust valves 54 and 55 cannot be increased compared to the case of the variable working angle mechanism 57, so that the internal EGR gas amount cannot be increased, thereby promoting warm-up. The effect will decrease.

  As shown in FIG. 8, in the case 2, the lift amount rises and falls abruptly as compared with the working angle variable mechanism 57. Therefore, in this case, if one of the two exhaust valves 55 is retarded to increase the combined working angle, a valve stamp is generated when the lift amount decreases. As a result, in this case as well, the effect of promoting warm-up is reduced because the overlap amount of the intake / exhaust valves 54 and 55 cannot be increased compared with the case of the variable working angle mechanism 57. Further, in this case, the working angle variable mechanism 57 is more advantageous in that the volume efficiency is considered to be lower than that of the working angle variable mechanism 57.

  Thus, the control system 100A can ensure a large variable upper limit of the operating angle by providing the operating angle variable mechanism 57 that can change the operating angle while keeping the maximum lift amount of the exhaust valve 55 constant. For this reason, the control system 100A is preferable in that the warm-up acceleration can be enhanced by suitably increasing the overlap amount of the intake and exhaust valves 54 and 55.

  FIG. 9 is an overall configuration diagram of the second embodiment. The engine 50B is substantially the same as the engine 50A except that it further includes a phase variable mechanism 58 that can change the phase (opening / closing timing) of the exhaust valve 55. For example, a structure in which the phase of the drive shaft provided in the operating angle variable mechanism 57 is changed with respect to the rotation of the engine 50B can be applied to the phase variable mechanism 58. The ECU 1B is substantially the same as the ECU 1A except that the control unit is realized as will be described later.

  FIG. 10 is an explanatory diagram of valve timing in the second embodiment. As shown in FIG. 10, in the second embodiment, not only can the working angle of the exhaust valve 55 be enlarged and reduced by the working angle variable mechanism 57, but the opening / closing timing of the exhaust valve 55 can be changed by the phase variable mechanism 58. Can do. In this regard, the phase variable mechanism 58 similarly changes the phase of each of a plurality (here, two) of exhaust valves 55 provided for each cylinder 51a.

  In the ECU 1B, the control unit further controls the phase variable mechanism 58 so as to retard the phase of the exhaust valve 55 when the engine 50B is warmed up. In controlling the phase variable mechanism 58, the control unit specifically calculates the phase control state of the phase variable mechanism 58 based on the engine operating state (specifically, the accelerator opening, the rotational speed NE, and the cooling water temperature here). Then, the phase variable mechanism 58 is controlled so that the phase control state becomes the calculated phase control state.

  In calculating the phase control state of the phase variable mechanism 58, the control unit specifically detects the engine operating state, and refers to the map data predetermined for the phase control state of the phase variable mechanism 58 according to the engine operating state. Then, the phase control state of the phase variable mechanism 58 is calculated by reading the phase control state of the phase variable mechanism 58 corresponding to the detected engine operating state. In this map data, the phase control state of the phase variable mechanism 58 to be realized according to the engine operating state is set in advance.

  The control unit that controls the working angle variable mechanism 57 and the phase variable mechanism 58 controls the working angle variable mechanism 57 so as to expand the working angle within a range in which the valve stamp does not occur when the lift amount decreases, and the exhaust valve 55 When the phase is not retarded, the operating angle variable mechanism 57 can be controlled so that the operating angle becomes smaller than the maximum operating angle that can be expanded without generating a valve stamp. Further, the phase variable mechanism 58 can be controlled so as to retard the phase of the exhaust valve 55 to the maximum extent within a range where no valve stamp is generated.

  In this embodiment, a control system 100B including the back pressure control valve 40, the operating angle variable mechanism 57, the phase variable mechanism 58, and the ECU 1B is realized.

  Next, the operation of the ECU 1B as the second control operation will be described using the flowchart shown in FIG. This flowchart is the same as the flowchart shown in FIG. 4 except that steps S3B and S4B are provided instead of steps S3A and S4A. For this reason, these are specifically described here. In step S3B, the ECU 1B calculates the opening degree of the back pressure regulating valve 40 to be realized, the operating angle control state of the operating angle variable mechanism 57, and the phase control state of the phase variable mechanism 58 based on the detected engine operating state (step S3B). S3B). Then, the back pressure control valve 40, the operating angle variable mechanism 57, and the phase variable mechanism 58 are controlled so that the calculated opening degree, operating angle control state, and phase control state are obtained (step S4B).

  Next, the effect of the control system 100B will be described. FIG. 12 is a view showing the variable upper limit of the working angle and the retard amount of the exhaust valve 55. As shown in FIG. 12, in the control system 100B, the phase variable mechanism 58 is controlled so as to retard the phase of the exhaust valve 55 when the engine 50B is warmed up. The phase of the exhaust valve 55 can be retarded within a range where no valve stamp is generated. For this reason, the control system 100B increases warm-up acceleration by enlarging the overlap amount of the intake / exhaust valves 54 and 55 while ensuring a large lift amount of the exhaust valve 55 as compared with the control system 100A. be able to.

  Specifically, the control system 100B controls the variable operating angle mechanism 57 so as to expand the operating angle within a range in which the valve stamp is not generated when the lift amount is reduced, and the valve stamp when the phase of the exhaust valve 55 is not retarded. The operating angle variable mechanism 57 is controlled so that the operating angle becomes smaller than the maximum operating angle that can be expanded without generating the valve, and the phase of the exhaust valve 55 is delayed as much as possible within a range where no valve stamp is generated. In addition, by controlling the phase variable mechanism 58, it is possible to improve the warm-up acceleration as described above.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

ECU 1A, 1B
Back pressure control valve 40
Engine 50A, 50B
Exhaust valve 55
Working angle variable mechanism 57
Phase variable mechanism 58

Claims (2)

A working angle variable mechanism capable of changing the working angle while keeping the maximum lift amount of the exhaust valve provided in the engine constant;
A back pressure adjusting device capable of adjusting a back pressure generated in the exhaust system of the engine;
A phase variable mechanism capable of changing the phase of the exhaust valve;
During the warm-up of the engine, to control the back pressure regulator so as to increase the back pressure generated in the exhaust system of the engine, the control operating angle variable mechanism so as to enlarge the working angle of the exhaust valve And a control unit that controls the phase variable mechanism so as to retard the phase of the exhaust valve . The engine control system according to claim 1,
The control unit controls the phase variable mechanism so as to retard the phase of the exhaust valve, and maximizes the phase of the exhaust valve within a range in which interference between the piston included in the engine and the exhaust valve does not occur. An engine control system that controls the phase variable mechanism to limit the angle .

Images