Vehicle control device

Abstract

To prevent the operational state of an internal combustion engine from being affected by an ice block formed from moisture in blow-by gas that flows backward.SOLUTION: A control device is for a vehicle which comprises: an internal combustion engine provided with an engine body, a supercharger including a compressor arranged on an intake passage connected to the engine body, a blow-by gas return passage leading blow-by gas generated in the engine body to the intake passage on a downstream side of the compressor, and a fresh air introduction passage which leads fresh air to the engine body through the intake passage on an upstream side of the compressor; and an automatic transmission to which power of the internal combustion engine is transmitted. The control device has: a calculation section which calculates an ice block generation degree due to moisture in the blow-by gas flowing from the engine body to the intake passage through the fresh air introduction passage when the internal combustion engine is in a supercharging region; and a control section which prevents shift-up operation of the automatic transmission when the ice block generation degree is likely to affect an operation state of the internal combustion engine.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device. [Background technology]

[0002] There are known vehicles equipped with internal combustion engines equipped with a supercharger. Some of these internal combustion engines are equipped with a blow-by gas return passage that guides blow-by gas generated in the engine body to an intake passage downstream of a compressor of the supercharger, and a fresh air introduction passage that guides fresh air from the intake passage upstream of the compressor to the engine body (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-264759 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, when the operating point of the internal combustion engine is in the supercharging region, positive pressure is generated in the intake passage downstream of the compressor, which may cause blow-by gas to flow back from the engine body into the intake passage through the fresh air introduction passage. In this case, if the outside temperature is low, the moisture in the blow-by gas may freeze and form ice blocks. These ice blocks may adhere to the inner surface of the fresh air introduction passage or collide with the compressor of the supercharger, which may affect the operating condition of the internal combustion engine.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a vehicle control device that prevents ice blocks from being formed due to the freezing of water in the blow-by gas that has flowed back, and that prevents the ice blocks from affecting the operating state of the internal combustion engine. [Means for solving the problem]

[0006] The above object can be achieved by a control device for a vehicle including an internal combustion engine having an engine body, a supercharger including a compressor arranged on an intake passage connected to the engine body, a blow-by gas return passage that guides blow-by gas generated in the engine body to the intake passage downstream of the compressor, and a fresh air introduction passage that guides fresh air from the intake passage upstream of the compressor to the engine body, and an automatic transmission to which power of the internal combustion engine is transmitted, the control device comprising: a calculation unit that calculates a degree of ice formation generated by freezing of water in blow-by gas flowing from the engine body to the intake passage via the fresh air introduction passage when a required operating point of the internal combustion engine belongs to a supercharging region; and a restriction unit that restricts upshifting of the automatic transmission when the degree of formation is equal to or greater than a first judgment value that may affect the operating state of the internal combustion engine.

[0007] The limiting unit may forcibly downshift the automatic transmission so that the required operating point belongs to a naturally aspirated engine when the generation degree is equal to or greater than a second determination value that is greater than the first determination value.

[0008] The limiting unit may cancel the restriction on the upshifting of the automatic transmission if the degree of generation becomes less than a third determination value that is smaller than the first determination value after restricting the upshifting of the automatic transmission, and may cancel the forced downshifting of the automatic transmission if the degree of generation becomes less than a fourth determination value that is smaller than the second determination value and larger than the first determination value after forcibly shifting down the automatic transmission.

[0009] The calculation unit may calculate the generation degree to be a larger value the longer the elapsed time during which the outside air temperature is below a predetermined temperature and the required operating point belongs to a supercharging region, and may calculate the generation degree to be a smaller value the longer the elapsed time during which the required operating point belongs to a naturally aspirated region. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a vehicle control device that suppresses the generation of ice blocks due to the freezing of water in the blow-by gas that has flowed back, which would affect the operating state of the internal combustion engine. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of a vehicle according to this embodiment. [Figure 2] FIG. 2 is a schematic diagram of the engine. [Figure 3] FIG. 3 is an explanatory diagram when the operating point of the engine is in the supercharging region. [Figure 4] FIG. 4 is a flowchart showing an example of ice block formation degree calculation control executed by the ECU. [Figure 5] FIG. 5 is an explanatory diagram of the operating points of the engine. [Figure 6] FIG. 6 is a flowchart showing an example of ice block formation suppression control executed by the ECU. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Vehicle outline] FIG. 1 is a schematic diagram of a vehicle 1 according to this embodiment. In FIG. 1, the vehicle 1 includes an engine 10, a torque converter 50, an automatic transmission 52, a propeller shaft 56, axles 60, drive wheels 62, a hydraulic control circuit 70, an oil pump 72, and an ECU (Electronic Control Unit) 100. The engine 10 is a gasoline or diesel engine that functions as a driving power source for traveling, and is an example of an internal combustion engine. The torque converter 50 is a fluid-type power transmission connected to the engine 10. The automatic transmission 52 is connected to the torque converter 50, and power from the engine 10 is transmitted to the automatic transmission 52 via the torque converter 50. The propeller shaft 56 is connected to an output shaft 54 ​​of the automatic transmission 52. The differential gear unit 58 is connected to the propeller shaft 56. The drive wheels 62 are connected to the differential gear unit 58 via the axles 60.

[0013] The automatic transmission 52 is provided with a hydraulic control circuit 70. The hydraulic control circuit 70 has a plurality of valves, and by controlling the valves, hydraulically controls the engagement and disengagement of the clutches and brakes of the automatic transmission 52. This enables the automatic transmission 52 to establish a desired gear. A mechanical oil pump 72 is connected to the torque converter 50. The oil pump 72 is driven and rotated by the engine 10 to generate hydraulic oil pressure for hydraulically controlling the automatic transmission 52 and for lubricating each part of the power transmission path from the engine 10 to the drive wheels 62.

[0014] The ECU 100 is an electronic control unit including a processing circuit that performs various arithmetic operations related to the driving control of the vehicle 1, and a memory that stores control programs and data. The ECU 100 is an example of a vehicle control device, and functionally realizes a calculation unit and a restriction unit, which will be described in detail later. The ECU 100 controls the operation of the engine 10. Specifically, the ECU 100 controls the torque and rotation speed of the engine 10 by controlling the throttle opening, ignition timing, and fuel injection amount of the engine 10. The ECU 100 also controls the automatic transmission 52 through control of the hydraulic control circuit 70.

[0015] The ECU 100 receives signals from an ignition switch 80, a crank angle sensor 81, an air flow meter 82, and an outside air temperature sensor 83. The ignition switch 80 detects the on / off state of the ignition. The crank angle sensor 81 detects the rotation speed of the crankshaft of the engine 10, i.e., the engine rotation speed. The air flow meter 82 detects the amount of intake air into the engine 10. The outside air temperature sensor 83 detects the temperature of the outside air.

[0016] [Engine outline] 2 is a schematic diagram of the engine 10. The engine 10 is a spark-ignition four-cylinder gasoline engine and is an example of an internal combustion engine, but is not limited to this and may be an engine other than four cylinders, for example, a compression-ignition diesel engine or other type of engine.

[0017] The engine 10 includes an engine body 11, a head cover 12, a crankcase 13, a piston 14, a combustion chamber 15, an intake passage 16, a turbocharger 20, an intercooler 22, and a throttle valve 24. The engine body 11 has a cylinder 11a, a head cover 12 provided above the cylinder 11a, and a crankcase 13 provided below the cylinder 11a. The piston 14 reciprocates within the combustion chamber 15 of the cylinder 11a. An intake passage 16 is connected to each cylinder of the engine body 11 via an intake manifold 16a.

[0018] The air cleaner 17 is attached near the inlet of the intake passage 16. The compressor 20a of the turbocharger 20 is installed downstream of the air cleaner 17 in the intake passage 16 and compresses the intake air. The compressor 20a is integrally connected via a connecting shaft to a turbine 20b arranged in an exhaust passage (not shown). The above-mentioned air flow meter 82 is provided in the intake passage 16 between the air cleaner 17 and the compressor 20a.

[0019] The intercooler 22 is installed downstream of the compressor 20a in the intake passage 16 and cools the supercharged air. An electronically controlled throttle valve 24 is installed downstream of the intercooler 22 and controlled by the ECU 100. The intake manifold 16a described above is arranged downstream of the throttle valve 24.

[0020] Blow-by gas guide passages 31a and 31b are provided in the cylinder 11a and the head cover 12. The blow-by gas guide passage 31a is formed by penetrating the cylinder 11a and the head cover 12, and connects the inside of the crankcase 13 to the oil separator 43, so that blow-by gas present in the crankcase 13 is guided to the oil separator 43. The blow-by gas guide passage 31b connects the head cover 12 to the oil separator 43, so that blow-by gas present in the internal space of the head cover 12 is guided to the oil separator 43.

[0021] The blow-by gas is guided to the oil separator 43 via the blow-by gas guide passages 31a and 31b, and the blow-by gas from which the oil mist has been separated in the oil separator 43 is returned to the intake manifold 16a via the blow-by gas return passage 36 that connects the oil separator 43 to the intake manifold 16a.

[0022] A PCV (Positive Crankcase Ventilation) valve 38 is installed at the end of the blow-by gas recirculation passage 36 on the oil separator 43 side. The PCV valve 38 is configured as a differential pressure actuated valve that operates in response to the differential pressure between the internal space of the head cover 12 on the upstream side and the intake manifold 16a on the downstream side. The PCV valve 38 adjusts the flow rate of the blow-by gas recirculating to the intake manifold 16a and prevents the blow-by gas from flowing back into the internal space of the head cover 12.

[0023] In addition, a fresh air introduction passage 34 is provided that connects the internal space of the head cover 12 with the intake passage 16 upstream of the compressor 20a and downstream of the air cleaner 17. More specifically, the fresh air introduction passage 34 connects the intake passage 16 with a fresh air-side separator 44. The fresh air-side separator 44 is provided with a fresh air guide passage 33a, which connects the fresh air-side separator 44 with the internal space of the head cover 12. Furthermore, a fresh air guide passage 33b connects the interior of the head cover 12 with the interior of the crankcase 13. Thus, fresh air passing through the intake passage 16 is introduced into the internal space of the head cover 12 and the crankcase 13 by the fresh air introduction passage 34, the fresh air-side separator 44, and the fresh air guide passages 33a and 33b.

[0024] [Backflow of blow-by gas] As shown in Fig. 2, when the operating point of the engine 10 is in the naturally aspirated (NA) region, the combustion chamber 15 and the intake manifold 16a, which are downstream of the throttle valve 24, are under negative pressure, and the intake passage 16, which is upstream of the compressor 20a, is under atmospheric pressure. Therefore, in the NA region, fresh air flows through the fresh air introduction passage 34, the fresh air separator 44, the fresh air guide passage 33a, the head cover 12, the fresh air guide passage 33b, and the crankcase 13. Blow-by gas is returned from the crankcase 13 and the head cover 12 to the intake manifold 16a via the oil separator 43 and the blow-by gas return passage 36. In this way, the blow-by gas is supplied from the intake manifold 16a into the combustion chamber 15, where it can be burned.

[0025] On the other hand, when the operating point of the engine 10 is in the supercharging region, the following problem may occur. FIG. 3 is an explanatory diagram of the case when the operating point of the engine 10 is in the supercharging region. When the operating point of the engine 10 is in the supercharging region, the combustion chamber 15 and the intake manifold 16a, which are downstream of the compressor 20a, are under positive pressure, while the intake passage 16, which is upstream of the compressor 20a, is under negative pressure. As a result, blow-by gas flows from the crankcase 13 through the blow-by gas guide passage 31a, the oil separator 43, the blow-by gas guide passage 31b, the head cover 12, the fresh air guide passage 33a, the fresh air separator 44, and the fresh air introduction passage 34, and then backflows into the intake passage 16, which is upstream of the compressor 20a. If the outside temperature is low, moisture in the blow-by gas may freeze and form ice blocks while the blow-by gas flows into the intake passage 16 via the fresh air introduction passage 34. Such ice blocks may adhere to and block the inner wall of the fresh air introduction passage 34, collide with the compressor 20a, or freeze the PCV valve 38, thereby affecting the operating state of the engine 10. Therefore, in this embodiment, the ECU 100 executes the following control.

[0026] [Ice block generation rate calculation control] 4 is a flowchart showing an example of ice formation degree calculation control executed by ECU 100. This control is repeatedly executed while the ignition is on. ECU 100 determines whether an increment condition for incrementing a counter indicating the ice formation degree is met (step S1).

[0027] The conditions for incrementing the counter are, for example, that the outside air temperature is equal to or lower than a predetermined temperature and that the required operating point of the engine 10 is in the supercharging region. The predetermined temperature is a temperature at which moisture in the blow-by gas may freeze when the blow-by gas flows backward through the fresh air introduction passage 34 as shown in FIG. 3. The predetermined temperature is, for example, 0°C, but is not limited to this and may be a temperature higher than 0°C by a predetermined margin. The case where the required operating point is in the supercharging region includes not only a case where the operating point of the engine 10 is already in the supercharging region in accordance with the required operating point, but also a case where the operating point of the engine 10 is still in the NA region but has moved into the supercharging region in accordance with an operation command from the driver.

[0028] Furthermore, whether the required operating point of the engine 10 belongs to the supercharging region may be determined based on the engine speed, engine torque, and gear position. FIG. 5 is an explanatory diagram of the operating point of the engine 10. In the graph of FIG. 5, the horizontal axis represents the engine speed, and the vertical axis represents the engine torque. In FIG. 5, the boundary between the supercharging region and the NA region is shown by a dashed line. The NA region is on the lower torque side of the boundary line, and the supercharging region is on the higher torque side of the boundary line. FIG. 5 also shows operating lines for each gear position from first to eighth. These operating lines represent the relationship between engine speed and engine torque. As the gear position becomes higher, the engine operating point more easily shifts from the NA region to the supercharging region. Whether the required operating point of the engine 10 belongs to the supercharging region may be determined based on such a map. Note that FIG. 5 illustrates an example of iso-power lines of the engine 10, which will be described in detail later.

[0029] If the answer to step S1 is Yes, i.e., if the outside air temperature is equal to or lower than a predetermined temperature and the required operating point of the engine 10 is in the supercharging region, the ECU 100 increments the counter (step S2). If the answer to step S1 is No, i.e., if at least one of the conditions that the outside air temperature is equal to or lower than a predetermined temperature and the required operating point of the engine 10 is in the supercharging region is not met, the ECU 100 decrements the counter (step S3). By repeating this process, the counter value increases as the duration over which the above-mentioned increment condition is met becomes longer, and the degree of ice block generation can be considered to be greater. Steps S1 to S3 are an example of the process executed by the calculation unit.

[0030] [Ice block formation suppression control] FIG. 6 is a flowchart showing an example of ice block formation suppression control executed by the ECU 100. This control is repeatedly executed while the ignition is on. The ECU 100 determines whether the counter value is less than a shift-up restriction release determination value (step S10). If the result of step S10 is Yes, the ECU 100 releases the shift-up restriction (step S11). If the result of step S10 is No, the ECU 100 determines whether the counter value is equal to or greater than a shift-up restriction determination value (step S12). If the result of step S12 is Yes, the ECU 100 restricts shift-up (step S13). Specifically, in this embodiment, the restriction on shift-up is a restriction on shifting to a gear higher than a predetermined gear. For example, shifting to eighth gear, which is higher than seventh gear, is restricted. However, the restriction on shift-up is not limited to this. For example, shifting to a gear higher than the gear at the time the counter value becomes equal to or greater than the shift-up restriction determination value may be restricted.

[0031] The shift-up restriction release determination value is a value smaller than the shift-up restriction determination value. As described above, the shift-up restriction determination value is set to a counter value at which the generation of ice blocks may affect the operating state of the engine 10. The shift-up restriction release determination value is set to a counter value at which the generated ice blocks can be considered to have sufficiently melted. The shift-up restriction release determination value and the shift-up restriction determination value are set based on experimental results, simulation results, etc. Furthermore, a difference between the shift-up restriction release determination value and the shift-up restriction determination value makes it possible to suppress hunting, in which the restriction and release of the shift-up restriction are repeated. The shift-up restriction determination value is an example of a first determination value. The shift-up restriction release determination value is an example of a third determination value. The processing of step S13 is an example of processing executed by the restriction unit.

[0032] Through the above process, when the counter value increases to or exceeds the shift-up restriction determination value, shift-up is restricted, and further ice block formation is suppressed. This reduces the impact of ice blocks on the operating state of the engine 10. When the counter value subsequently decreases and falls below the shift-up restriction release determination value, it is assumed that the ice blocks have sufficiently melted, and the shift-up restriction is released, ensuring drivability.

[0033] Next, the ECU 100 determines whether the counter value is less than a downshift cancellation determination value (step S20). If the result in step S20 is Yes, the ECU 100 cancels the forced downshift (step S21). If the result in step S20 is No, the ECU 100 determines whether the counter value is equal to or greater than the downshift determination value (step S22). If the result in step S22 is Yes, the ECU 100 forcibly downshifts the engine 10 so that the required operating point of the engine 10 moves from the supercharging region to the NA region while maintaining the constant output of the engine 10 (step S23). Specifically, the ECU 100 downshifts to the highest gear within the NA region that can maintain the constant output.

[0034] The downshift cancellation determination value is a value smaller than the downshift determination value and greater than the upshift limit value. The downshift determination value is also greater than the above-described upshift limit determination value. The downshift determination value is set to a counter value at which the formation of ice blocks is likely to affect the operating state of the engine 10, and therefore it is desirable to promote the melting of the ice blocks. The downshift cancellation determination value is set to a counter value at which it is not necessary to promote the melting of the ice blocks by forcibly downshifting. The downshift cancellation determination value and the downshift determination value are set based on experimental results, simulation results, and the like. Furthermore, the difference between the downshift cancellation determination value and the downshift determination value makes it possible to suppress hunting, which is the repeated occurrence of forcible downshifts and their cancellation. The downshift determination value is an example of a second determination value. The downshift cancellation determination value is an example of a fourth determination value. The processing of step S23 is an example of processing executed by the restriction unit.

[0035] As a result of the above processing, if the counter value further increases to or exceeds the downshift determination value while upshifting is restricted, a downshift is forcibly performed so that the required operating point of the engine 10 transitions from the supercharged region to the naturally aspirated region. This facilitates the melting of the ice blocks. When a forcible downshift is performed, the engine speed and engine torque are limited so that the engine 10 maintains constant output. For example, the engine speed is increased and engine torque is reduced along the constant output line shown in FIG. 5, thereby performing a downshift so that the operating point transitions from the supercharged region to the naturally aspirated region. This prevents a decrease in drivability. When the counter value decreases and the downshift is canceled, it is determined that there is no need to facilitate the melting of the ice blocks, and the downshift is canceled, thereby ensuring drivability.

[0036] In the above embodiment, the counter is decremented when at least one of the conditions that the outside air temperature is equal to or lower than a predetermined temperature and the required operating point of the engine 10 does not belong to the supercharging region is not satisfied, but this is not limiting. For example, when the outside air temperature is equal to or lower than a predetermined temperature but the required operating point of the engine 10 belongs to the NA region, the counter is decremented, and when the outside air temperature is higher than the predetermined temperature but the required operating point of the engine 10 belongs to the supercharging region, the current counter value may be maintained.

[0037] In the above embodiment, the vehicle 1 is an engine vehicle equipped with the engine 10, but the present invention is not limited to this, and the contents of the above embodiment may be applied to a hybrid vehicle equipped with an engine and a motor.

[0038] 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 variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0039] 1 vehicle 10 Engine 11. Main body of the organization 16 Intake passage 20. Turbocharger 34 New air intake passage 36 Blow-by gas return passage 52 Automatic transmission 100 ECU (vehicle control unit, calculation unit, limiting unit)

Claims

[Claim 1] an internal combustion engine having an engine body, a turbocharger including a compressor arranged in an intake passage connected to the engine body, a blow-by gas return passage that introduces blow-by gas generated in the engine body to the intake passage downstream of the compressor, and a fresh air introduction passage that introduces fresh air from the intake passage upstream of the compressor to the engine body; an automatic transmission to which power of the internal combustion engine is transmitted, a calculation unit that calculates a degree of ice formation caused by freezing of moisture in blow-by gas flowing from the engine body through the fresh air introduction passage into the intake passage when a required operating point of the internal combustion engine belongs to a supercharging region; and a limiting unit that limits an upshift of the automatic transmission when the generation degree is equal to or greater than a first determination value that may affect an operating state of the internal combustion engine, the limiting unit forcibly downshifts the automatic transmission so that the required operating point belongs to a naturally aspirated state when the generation degree is equal to or greater than a second determination value that is greater than the first determination value; the limiting unit limits the rotation speed and torque of the internal combustion engine so as to maintain equal output of the internal combustion engine before and after the limiting unit performs a downshift of the automatic transmission, the limiting unit cancels the restriction on the upshifting of the automatic transmission when the degree of generation becomes less than a third determination value that is smaller than the first determination value after limiting the upshifting of the automatic transmission, and cancels the forced downshifting of the automatic transmission when the degree of generation becomes less than a fourth determination value that is smaller than the second determination value and larger than the first determination value after forcibly downshifting the automatic transmission; a control device for a vehicle, wherein the calculation unit calculates the generation degree to be a larger value the longer the elapsed time during which the outside air temperature is equal to or lower than a predetermined temperature and the required operating point is in a supercharging region, and calculates the generation degree to be a smaller value the longer the elapsed time during which the required operating point is in a naturally aspirated region.

Images