Control system for V-type engines

Abstract

To provide a control device of a V-engine which can suppress the occurrence of preignition at both banks by easy control.SOLUTION: A control device of a V-engine comprises: a first intake temperature sensor for detecting a first intake temperature of intake air flowing in a first intake passage which is connected to a first bank; a second intake temperature sensor for detecting a second intake temperature of intake air flowing in a second intake passage which is connected to a second bank; a first variable valve mechanism which can change an advance angle amount at the closure of an intake valve of each cylinder of the first bank; a second variable valve mechanism which can change an advance angle amount at the closure of an intake valve of each cylinder of the second bank; and a determination part for determining which is higher in a first intake temperature and a second intake temperature. When either of the first intake temperature and the second intake temperature is high, the control device lowers the advance angle amounts at the closure of the first intake valve and the second intake valve according to the higher intake temperature.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a control device for a V-type engine.

Background Art

[0002] There is a technique for suppressing the occurrence of so-called pre-ignition in which an air-fuel mixture self-ignites before ignition by a spark plug by controlling the closing timing of an intake valve based on the intake air temperature (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There is a V-type engine in which intake passages are connected to two banks respectively. In this V-type engine, there is a possibility that the temperature of the intake air flowing through the intake passage connected to one bank and the temperature of the intake air flowing through the intake passage connected to the other bank vary. When there is such a variation in the intake air temperature, if the closing timing of the intake valves in both banks is controlled based on only the intake air temperature of one bank, even if the occurrence of pre-ignition can be suppressed in one bank, there is a possibility that pre-ignition may occur in the other bank.

[0005] On the other hand, it is conceivable to suppress the occurrence of pre-ignition for each bank by independently controlling the closing timing of the intake valves for each bank according to the intake air temperature of the bank. However, in this case, the control becomes complicated.

[0006] Therefore, an object of the present invention is to provide a control device for a V-type engine that suppresses the occurrence of pre-ignition in both banks with simple control.

Means for Solving the Problems

[0007] The above objective is to provide a first bank having a plurality of first cylinders, a second bank having a plurality of second cylinders, a first variable valve timing mechanism capable of changing the amount of advance angle from a first reference closing time which is retarded to the intake bottom dead center of the first cylinder for the closing timing of the first intake valve of the first cylinder, a second variable valve timing mechanism capable of changing the amount of advance angle from a second reference closing time which is retarded to the intake bottom dead center of the second cylinder for the closing timing of the second intake valve of the second cylinder, a first intake temperature sensor for detecting the first intake temperature of intake air flowing through a first intake passage connected to the first bank, and a second intake temperature sensor for detecting the second intake temperature of intake air flowing through a second intake passage connected to the second bank, wherein the crank angle from the intake bottom dead center of the first cylinder to the first reference closing time is different from the crank angle from the intake bottom dead center of the second cylinder to the second reference closing time This can be achieved by a V-type engine control device comprising: a control unit that controls the first and second variable valve timing mechanisms so that the advance angle of the closing timings of the first and second intake valves match; an acquisition unit that acquires the first and second intake temperatures; and a determination unit that determines which of the first and second intake temperatures is higher. If the first intake temperature is higher than the second intake temperature, the control unit reduces the advance angle of the closing timings of the first and second intake valves from the first and second reference closing times as the first intake temperature increases; and if the second intake temperature is higher than the first intake temperature, the control unit reduces the advance angle of the closing timings of the first and second intake valves from the first and second reference closing times as the second intake temperature increases.

[0008] The system includes a prediction unit that predicts whether or not pre-ignition will occur in the first cylinder based on the first intake air temperature and whether or not pre-ignition will occur in the second cylinder based on the second intake air temperature. If it is predicted that pre-ignition will occur in at least one of the first and second cylinders, the advance angle of the closing timing of the first and second intake valves from the respective first and second reference closing timings may be reduced compared to the case where it is predicted that pre-ignition will not occur in either the first or second cylinder.

[0009] The V-type engine includes a first intake pressure sensor for detecting a first intake pressure in the first intake passage, a second intake pressure sensor for detecting a second intake pressure in the second intake passage, and a rotational speed sensor for detecting the rotational speed of the V-type engine. The acquisition unit acquires the first and second intake pressures and the rotational speed. Based on the first intake temperature, the first intake pressure, and the rotational speed, the prediction unit predicts whether or not pre-ignition occurs in the first cylinder. Based on the second intake temperature, the second intake pressure, and the rotational speed, the prediction unit may also predict whether or not pre-ignition occurs in the second cylinder. [Effects of the Invention]

[0010] According to the present invention, a control device for a V-type engine can be provided that suppresses the occurrence of pre-ignition in both banks with simple control. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram of the engine's configuration. [Figure 2] This flowchart illustrates the first limit control of the advance angle of the intake valve opening and closing timing. [Figure 3] This is an explanatory diagram illustrating the limitations on the advance angle of the intake valve's opening and closing timing. [Figure 4] This map defines the relationship between intake air temperature and the upper limit of the advance angle of the intake valve opening and closing timing. [Figure 5] This flowchart illustrates the second limit control for the advance angle of the intake valve opening and closing timing. [Modes for carrying out the invention]

[0012] [Overview of a V-type engine] Figure 1 is a schematic diagram of the V-type engine 1. The V-type engine 1 has a pair of banks 2L and 2R arranged around the crankshaft at an appropriate bank angle relative to each other. Bank 2L has three cylinders 20L. Bank 2R has three cylinders 20R. In other words, the V-type engine 1 is a V-type 6-cylinder engine, but the number of cylinders is not limited to this. The V-type engine 1 is also a gasoline engine. Banks 2L and 2R correspond to the first and second banks, respectively. Cylinders 20L and 20R correspond to the first and second cylinders, respectively. Exhaust passages 30L and 30R are connected to banks 2L and 2R, respectively. Catalysts 31L and 31R are provided to exhaust passages 30L and 30R, respectively.

[0013] Intake passages 10L and 10R are connected to banks 2L and 2R, respectively. Intake passages 10L and 10R correspond to the first and second intake passages, respectively. Intake passage 10L is equipped with, from upstream, an air cleaner 11L, an intercooler 12L, an intake air temperature sensor 13L, an intake pressure sensor 14L, a throttle valve 15L, a surge tank 16L, and a branch pipe 17L. Similarly, intake passage 10R is equipped with, from upstream, an air cleaner 11R, an intercooler 12R, an intake air temperature sensor 13R, an intake pressure sensor 14R, a throttle valve 15R, a surge tank 16R, and a branch pipe 17R. Intake air temperature sensors 13L and 13R correspond to the first and second intake air temperature sensors, respectively. Intake pressure sensors 14L and 14R correspond to the first and second intake pressure sensors, respectively.

[0014] Air cleaners 11L and 11R filter dust and other particles from the intake air flowing through intake passages 10L and 10R, respectively. Intercoolers 12L and 12R cool the intake air flowing through intake passages 10L and 10R, respectively. Intake air temperature sensor 13L detects the intake air temperature TL, which is the temperature of the intake air flowing through intake passage 10L. Similarly, intake air temperature sensor 13R detects the intake air temperature TR, which is the temperature of the intake air flowing through intake passage 10R. Intake pressure sensor 14L detects the intake pressure PL, which is the pressure inside intake passage 10L. Similarly, intake pressure sensor 14R detects the intake pressure PR, which is the pressure inside intake passage 10R. Throttle valves 15L and 15R adjust the amount of intake air introduced into cylinders 20L and 20R, respectively. Surge tanks 16L and 16R store the intake air. Branch pipe 17L connects surge tank 16L to the intake port of cylinder 20L. Similarly, branch pipe 17R connects surge tank 16R to the intake port of cylinder 20R.

[0015] Cylinder 20L is equipped with two intake valves 21L, two exhaust valves 22L, and a spark plug 23L. Similarly, cylinder 20R is equipped with two intake valves 21R, two exhaust valves 22R, and a spark plug 23R. Intake valves 21L and 21R introduce intake air into cylinders 20L and 20R, respectively. Exhaust valves 22L and 22R discharge exhaust from cylinders 20L and 20R, respectively. Spark plugs 23L and 23R ignite the air-fuel mixture in cylinders 20L and 20R, respectively. Although not shown in the diagram, fuel injection valves are provided to supply fuel to the inside of cylinders 20L and 20R. Intake valves 21L and 21R correspond to the first and second intake valves, respectively.

[0016] Banks 2L and 2R are provided with camshafts 25L and 25R, respectively, which open and close intake valves 21L and 21R. Furthermore, banks 2L and 2R are provided with hydraulic variable valve timing mechanisms 26L and 26R, respectively, which can change the opening and closing timing of intake valves 21L and 21R. The variable valve timing mechanisms 26L and 26R change the advance angle of the opening and closing timing of intake valves 21L and 21R by changing the rotational phase of the camshafts 25L and 25R relative to a crankshaft (not shown). Specifically, the variable valve timing mechanism 26L changes the advance angle of the opening and closing timing of intake valve 21L while maintaining a constant operating angle corresponding to the period during which intake valve 21L is open and maintaining a constant maximum lift amount of intake valve 21L. The variable valve timing mechanism 26R operates similarly. The variable valve timing mechanisms 26L and 26R correspond to the first and second variable valve timing mechanisms, respectively.

[0017] The ECU (Electronic Control Unit) 50 includes a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), etc. The ECU 50 is electrically connected to the ignition switch S1, crank angle sensor S2, intake air temperature sensors 13L and 13R, intake pressure sensors 14L and 14R, throttle valves 15L and 15R, and spark plugs 23L and 23R. The ignition switch S1 detects whether the ignition is on or off. The crank angle sensor S2 detects the engine speed R, which is the rotational speed of the V-type engine 1. The crank angle sensor S2 corresponds to the rotational speed sensor.

[0018] Based on the engine speed R, intake air temperatures TL and TR, intake air pressures PL and PR, etc., the ECU 50 controls the opening degrees of the throttle valves 15L and 15R, the ignition timing of the spark plugs 23L and 23R, the fuel injection amounts in each of the banks 2L and 2R, and the opening and closing timing of the intake valves 21L and 21R by the variable valve mechanisms 26L and 26R to control the entire V-type engine 1. At this time, the ECU 50 controls so that the torques of the banks 2L and 2R match. Incidentally, the ECU 50 controls the opening and closing timing of the intake valves 21L and 21R by controlling the amount of oil supplied to the variable valve mechanisms 26L and 26R via an oil control valve (not shown). Further, the CPU, ROM, and RAM of the ECU 50 functionally realize a control unit, an acquisition unit, a determination unit, and a prediction unit, which will be described in detail later.

[0019] Here, the ECU 50 controls the variable valve mechanisms 26L and 26R so that the amount of advance of the opening and closing timing of each of the intake valves 21L and 21R matches. Specifically, the respective target phases of the camshafts 25L and 25R with respect to the crankshaft are set to the same value. This control is executed by the control unit. Compared with the case of independently controlling the opening and closing timing of the intake valves 21L and 21R in this way, this control is simplified. Also, in order to suppress the occurrence of pre-ignition, the ECU 50 executes the first and second limit controls of the amount of advance of the opening and closing timing of the following intake valves 21L and 21R.

[0020] Here, for example, due to variations in the temperatures of the intercoolers 12L and 12R and variations in the opening degrees of the throttle valves 15L and 15R, there may be variations in the intake air temperatures TL and TR. Even when such variations occur in the intake air temperatures TL and TR, the ECU 50 suppresses the occurrence of pre-ignition in both of the cylinders 20L and 20R by executing the following control.

[0021] [First Limit Control of the Amount of Advance of the Opening and Closing Timing of the Intake Valve] FIG. 2 is a flowchart illustrating the first limit control of the advance amount of the opening and closing timing of intake valves 21L and 21R. This control is repeatedly executed while the ignition is on. The ECU 50 acquires the intake temperatures TL and TR (step S1), and determines whether the intake temperature TL is higher than the intake temperature TR (step S2). If Yes in step S2, the ECU 50 restricts the advance amount of the opening and closing timing of each of the intake valves 21L and 21R based on the intake temperature TL (step S3). If No in step S2, considering that the intake temperature TR is higher than the intake temperature TL, the ECU 50 restricts the advance amount of the opening and closing timing of each of the intake valves 21L and 21R based on the intake temperature TR (step S4). Step S1 is an example of the process executed by the acquisition unit. Step S2 is an example of the process executed by the determination unit. Steps S3 and S4 are examples of the processes executed by the control unit.

[0022] FIG. 3 is an explanatory diagram of the restriction of the advance amount of the opening and closing timing of intake valves 21L and 21R. FIG. 3 shows a diagram of the closing timing of the intake valve. The vertical axis represents the lift amount of the intake valve, and the horizontal axis represents the crank angle. The reference closing timing IVC is set on the retarded side with respect to the intake bottom dead center. The crank angle from the intake bottom dead center to the reference closing timing IVC is the same for all cylinders 20L and 20R. Although details will be described later, an upper limit value θa [CA] of the advance amount is set from the reference closing position IVC, and the variable valve mechanisms 26L and 26R are controlled so that the advance amount of the opening and closing timing of each of the intake valves 21L and 21R is not more than the upper limit value θa.

[0023] Figure 4 is a map that defines the relationship between intake air temperature and the upper limit θa of the advance angle of the intake valve opening and closing timing. As shown in Figure 4, the upper limit θa decreases as the intake air temperature increases. This is because higher intake air temperatures increase the in-cylinder temperature, making pre-ignition more likely. Also, as the closing timing advances towards the intake bottom dead center, the amount of intake air introduced into the cylinder increases, making pre-ignition more likely. Thus, the amount of advance angle of the intake valve closing timing is controlled to decrease as the intake air temperature increases. Therefore, for example, if the target advance angle set according to the operating state of the V-type engine 1 is greater than the upper limit θa, the actual advance angle is limited to the upper limit θa. As a result, the advance angle decreases as the intake air temperature increases.

[0024] As described above, when the intake air temperature TL is higher than the intake air temperature TR, the ECU 50 refers to the map in Figure 4 and sets the upper limit θa of the advance amount of intake valves 21L and 21R based on the intake air temperature TL. This reduces the advance amount of intake valves 21L and 21R to match cylinder 20L, which is prone to pre-ignition. Similarly, when the intake air temperature TR is higher than the intake air temperature TL, the ECU 50 sets the upper limit θa based on the intake air temperature TR. This reduces the advance amount of intake valves 21L and 21R to match cylinder 20R, which is prone to pre-ignition. In this way, the occurrence of pre-ignition in both cylinders 20L and 20R is suppressed. Note that in Figure 4, the upper limit θa decreases linearly as the intake air temperature increases, but it may also decrease curvilinearly or in steps.

[0025] [Second limit control of the advance angle amount for the opening and closing timing of the intake valve] Figure 5 is a flowchart illustrating the second limit control of the advance amount of the opening and closing timing of intake valves 21L and 21R. This control is repeatedly executed while the ignition is ON. The ECU 50 acquires the intake air temperature TL and TR, intake air pressure PL and PR, and engine speed R (step S11). Next, the ECU 50 predicts whether or not pre-ignition will occur in cylinder 20L and cylinder 20R (step S12). In detail, for cylinder 20L, the presence or absence of pre-ignition is predicted based on the intake air temperature TL, intake air pressure PL, and engine speed R. For cylinder 20R, the presence or absence of pre-ignition is predicted based on the intake air temperature TR, intake air pressure PR, and engine speed R. Here, as mentioned above, pre-ignition is more likely to occur when the intake air temperature is high, when the intake air pressure is high, and when the engine speed is low. Step S11 is an example of the processing performed by the acquisition unit. Step S12 is an example of the process performed by the prediction unit.

[0026] Therefore, ECU50 predicts that pre-ignition will occur in cylinder 20L if, for example, (1) the intake air temperature TL is above a predetermined temperature t, (2) the intake air pressure PL is above a predetermined pressure p, and (3) the engine speed R is below a predetermined speed r. If any of the above conditions (1) to (3) are not met, ECU50 predicts that pre-ignition will not occur in cylinder 20L. Similarly, ECU50 predicts that pre-ignition will occur in cylinder 20R if, for example, (4) the intake air temperature TR is above a predetermined temperature t, (5) the intake air pressure PR is above a predetermined pressure p, and (6) the engine speed R is below a predetermined speed r. If any of the above conditions (4) to (6) are not met, ECU50 predicts that pre-ignition will not occur in cylinder 20R. Note that the predetermined temperature t is the same value in conditions (1) and (4) above. The predetermined pressure p is the same value under conditions (2) and (5). The predetermined rotational speed r is the same value under conditions (3) and (6).

[0027] The ECU 50 determines whether or not it is predicted that pre-ignition will occur in at least one of cylinders 20L and 20R (step S13). If the answer in step S13 is No, that is, if it is predicted that pre-ignition will not occur in either cylinder 20L or 20R, this control terminates. Step S13 is an example of the processing performed by the control unit.

[0028] If the answer in step S13 is Yes, the ECU 50 further restricts the advance amount of the opening and closing timings of the intake valves 21L and 21R (step S14). For example, the ECU 50 may restrict the advance amount by an upper limit θb that is smaller than the upper limit θa, instead of the upper limit θa mentioned above. Alternatively, the ECU 50 may use as an upper limit a value obtained by subtracting a value smaller than the upper limit θa from the upper limit θa. Or, it may use as an upper limit a value obtained by multiplying the upper limit θa by a value less than 1. In this way, if the occurrence of pre-ignition is predicted in at least one of cylinders 20L and 20R, the advance amount of the opening and closing timings of the intake valves 21L and 21R is further restricted, and the occurrence of pre-ignition in both banks 2L and 2R is suppressed. As described above, the occurrence of pre-ignition is effectively suppressed by the first and second limiting controls.

[0029] The variable valve timing mechanisms 26L and 26R are hydraulic, but are not limited to this; they may also be electromagnetic variable valve timing mechanisms that change the opening and closing timing of the intake valves 21L and 21R using electromagnetic actuators.

[0030] The variable valve timing mechanisms 26L and 26R may change the opening and closing timing while keeping the operating angles of the intake valves 21L and 21R constant, or they may reduce the operating angle as the closing timing advances.

[0031] The intake air temperature sensors 13L and 13R may be provided in the intake passages 10L and 10R downstream of the throttle valves 15L and 15R, respectively. Alternatively, the intake air temperature sensors 13L and 13R may be provided, for example, in the surge tanks 16L and 16R, respectively. It is preferable that the intake air temperature sensors 13L and 13R are provided in the same position on the bank 2L and 2R sides, respectively. The same applies to the intake pressure sensors 14L and 14R.

[0032] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of Symbols]

[0033] 1 V-type engine 2L Bank (Bank 1) 2R Bank (Second Bank) 10L intake passage (first intake passage) 10R Intake passage (2nd intake passage) 13L Intake Air Temperature Sensor (First Intake Air Temperature Sensor) 13R Intake air temperature sensor (2nd intake air temperature sensor) 20L cylinder (1st cylinder) 20R cylinder (2nd cylinder) 21L intake valve (first intake valve) 21R Intake valve (2nd intake valve) 26L Variable valve timing mechanism (first variable valve timing mechanism) 26R Variable valve timing mechanism (second variable valve timing mechanism) 50 ECU (Control unit, control unit, acquisition unit, determination unit, and prediction unit for V-type engines)

Claims

[Claim 1] A control device for a V-type engine comprising: a first bank having a plurality of first cylinders; a second bank having a plurality of second cylinders; a first variable valve timing mechanism capable of changing the amount of advance of the closing timing of the first intake valve of the first cylinder from a first reference closing time which is retarded to the intake bottom dead center of the first cylinder; a second variable valve timing mechanism capable of changing the amount of advance of the closing timing of the second intake valve of the second cylinder from a second reference closing time which is retarded to the intake bottom dead center of the second cylinder; a first intake temperature sensor for detecting the first intake temperature of intake air flowing through a first intake passage connected to the first bank; and a second intake temperature sensor for detecting the second intake temperature of intake air flowing through a second intake passage connected to the second bank, wherein the crank angle from the intake bottom dead center of the first cylinder to the first reference closing time is the same as the crank angle from the intake bottom dead center of the second cylinder to the second reference closing time, A control unit that controls the first and second variable valve timing mechanisms so that the advance angle amounts for the closing timings of the first and second intake valves are the same, The acquisition unit acquires the first and second intake air temperatures, The system includes a determination unit that determines which of the first intake air temperature and the second intake air temperature is higher, If the first intake air temperature is higher than the second intake air temperature, the control unit reduces the advance angle of the closing timing of the first and second intake valves from the first and second reference closing timings as the first intake air temperature increases. If the second intake air temperature is higher than the first intake air temperature, the control unit reduces the advance angle of the closing timing of the first and second intake valves from the first and second reference closing timings as the second intake air temperature increases. The system includes a prediction unit that predicts whether or not pre-ignition occurs in the first cylinder based on the first intake air temperature, and whether or not pre-ignition occurs in the second cylinder based on the second intake air temperature. If it is predicted that pre-ignition will occur in at least one of the first and second cylinders, the advance amount of the closing timing of the first and second intake valves from the first and second reference closing timings, respectively, will be reduced even further than the advance amount reduced by the control unit, compared to the case where it is predicted that pre-ignition will not occur in either the first or second cylinder. The V-type engine comprises a first intake pressure sensor for detecting a first intake pressure in the first intake passage, a second intake pressure sensor for detecting a second intake pressure in the second intake passage, and a rotational speed sensor for detecting the rotational speed of the V-type engine. The acquisition unit acquires the first and second intake pressures and the rotational speed, When the first intake air temperature is above a predetermined temperature, the first intake pressure is above a predetermined pressure, and the rotational speed is below a predetermined rotational speed, the prediction unit predicts that pre-ignition will occur in the first cylinder. If any of the following conditions are not met, the prediction unit predicts that pre-ignition will not occur in the first cylinder: the first intake air temperature is above the predetermined temperature, the first intake pressure is above the predetermined pressure, or the rotational speed is below the predetermined rotational speed. When the second intake air temperature is above the predetermined temperature, the second intake pressure is above the predetermined pressure, and the rotational speed is below the predetermined rotational speed, the prediction unit predicts that pre-ignition will occur in the second cylinder. A control device for a V-type engine, wherein if any of the following conditions are not met, the prediction unit predicts that pre-ignition will not occur in the second cylinder: the second intake air temperature is above the predetermined temperature, the second intake pressure is above the predetermined pressure, or the rotational speed is below the predetermined rotational speed.

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