Control device for engine

Abstract

To suppress generation of large distortion of an engine due to increase in a temperature difference of the engine.SOLUTION: A control device 1 for an engine includes: a regulation section (throttle valve 29) that regulates an intake air filling amount relative to a cylinder 22 in accordance with an operating amount of an accelerator pedal; a measurement section (oil temperature sensor 57) that outputs a measurement signal related to a temperature of an upper end part of a cylinder head 25 having an intake port 26 and an exhaust port 27 communicating with the cylinder; and a control section 49 that sets an upper limit value of the intake air filling amount to be smaller as the temperature of the upper end part of the cylinder head is lower when the temperature of the upper end part of the cylinder head is a predetermined temperature or lower on the basis of the measurement signal obtained by the measurement section at start of an engine 2, and outputs a control signal corresponding to the operating amount of the accelerator pedal within a range that does not exceed the upper limit value of the intake air filling amount to the regulation section.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an engine control device. [Background technology]

[0002] Patent Document 1 describes a conventional cooling device for an internal combustion engine. The cooling device includes a strain sensor that detects strain in an engine block, and a cooling means that controls the circulation of cooling water in a cooling passage in the engine block. The cooling means circulates the cooling water so that the amount of strain detected by the strain sensor is equal to or less than a predetermined value. More specifically, when the detected amount of strain exceeds the predetermined value, the rotation speed of the electric water pump increases, and the flow rate of the cooling water increases. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-72285 A Summary of the Invention [Problem to be solved by the invention]

[0004] The thermal distortion that occurs in an engine is caused by the temperature difference between the high temperature part and the low temperature part. A large temperature difference causes the deformation of the engine to become non-uniform, and the greater the non-uniformity of the deformation, the greater the distortion.

[0005] For example, consider a case where an engine is started in an environment where the outside air temperature is below -20°C, and the accelerator pedal is depressed immediately after the engine is started, causing the throttle valve to be fully opened. In this case, the temperature of the exhaust ports and exhaust manifold formed in the cylinder head of the engine may rise rapidly locally, while the temperature of areas away from the exhaust side of the cylinder head, for example, near the top end of the cylinder head, may remain low due to the extremely low outside air temperature. In this case, the cylinder head may be significantly distorted due to the large temperature difference.

[0006] The conventional cooling device adjusts the flow rate of the cooling water. However, immediately after the engine is started, the thermostat valve is closed and the cooling water does not pass through the engine. Therefore, the exhaust side of the cylinder head is not cooled. Even if the cooling water passes through the engine, once the temperature of the cooling water reaches 100°C, no further cooling effect can be expected. The conventional cooling device described above is not very effective at suppressing the temperature difference in the engine that may occur immediately after the engine is started.

[0007] The technology disclosed herein suppresses significant distortion of the engine caused by large temperature differences in the engine. [Means for solving the problem]

[0008] The technology disclosed herein relates to an engine control device. an adjustment unit that adjusts an intake air filling amount for the cylinder in response to an accelerator pedal depression amount; a measuring unit that outputs a measurement signal related to a temperature of an upper end portion of a cylinder head having an intake port and an exhaust port communicating with the cylinder; and a control unit which, based on a measurement signal from the measuring unit when the temperature of the upper end of the cylinder head is below a predetermined temperature, sets the upper limit of the intake air filling volume to a smaller value the lower the temperature of the upper end of the cylinder head, and outputs a control signal to the adjustment unit according to the amount of operation of the accelerator pedal within a range that does not exceed the upper limit of the intake air filling volume.

[0009] The measurement unit outputs a measurement signal related to the temperature of an upper end of the cylinder head. The upper end of the cylinder head is away from the exhaust port of the cylinder head. The temperature difference between the temperature of the upper end of the cylinder head and the temperature near the exhaust port is likely to be large. The exhaust port is a port that communicates with the cylinder and is a port that discharges burnt gas inside the cylinder from the cylinder. The cylinder head may have an exhaust manifold in which multiple exhaust ports are gathered together.

[0010] The control unit outputs a control signal to the adjustment unit according to the amount of accelerator pedal depression. The adjustment unit adjusts the amount of intake air charged to the cylinder according to the control signal. When the amount of accelerator pedal depression is large, the adjustment unit increases the amount of intake air charged to the cylinder. When the amount of intake air charged is large, the engine output increases and the temperature near the exhaust port of the cylinder head also increases. The adjustment unit may be a throttle valve located midway in the intake pipe communicating with the cylinder. The adjustment unit may also be an intake valve and / or an exhaust valve that opens and closes the intake port and / or the exhaust port.

[0011] The control unit also sets the upper limit of the intake air charge amount to a lower value according to the temperature of the upper end of the cylinder head, which is the temperature when the engine is started. Specifically, when the temperature of the upper end of the cylinder head when the engine is started is equal to or lower than a predetermined temperature, the control unit sets the upper limit of the intake air charge amount to a lower value as the temperature of the upper end of the cylinder head is lower. The predetermined temperature may be, for example, a temperature below freezing.

[0012] It should be noted that starting the engine here refers to starting the engine by the driver in the vehicle operating the starter switch, and generally, the temperature of the engine at the time of starting is substantially equal to the outside air temperature.

[0013] The control unit further outputs a control signal to the adjustment unit according to the amount of accelerator pedal operation based on the set upper limit value of the intake air charge amount, within a range not exceeding the upper limit value. Even if the driver depresses the accelerator pedal deeply, the intake air charge amount is limited by the upper limit value. The engine output is suppressed, and the increase in temperature near the exhaust port of the cylinder head is also suppressed. As a result, the temperature difference in the engine, specifically the cylinder head, is suppressed from increasing, and the occurrence of significant distortion in the cylinder head is suppressed.

[0014] Here, unlike the above-mentioned control device, a control is considered in which the intake air charge amount is limited by setting an upper limit value for the intake air charge amount after the temperature difference between the upper end of the cylinder head and the temperature near the exhaust port becomes large during engine operation. In this case, the temperature difference between the upper end of the cylinder head and the temperature near the exhaust port is not large immediately after the engine is started, so the intake air charge amount is not substantially limited, while as the temperature near the exhaust port increases after the engine is started, the temperature difference between the upper end of the cylinder head and the temperature near the exhaust port increases, so that the intake air charge amount is limited by the set upper limit value. With this type of control, the engine output is limited as the engine temperature increases, which causes a sense of discomfort for the driver.

[0015] In response to this, the control device sets an upper limit for the intake air charge amount in advance according to the temperature at the top end of the cylinder head when the engine is started, in other words, before the temperature difference between the temperature at the top end of the cylinder head and the temperature near the exhaust port becomes large, thereby limiting the intake air charge amount. This control can prevent the driver from feeling uncomfortable as mentioned above.

[0016] Furthermore, the control device does not suppress the distortion of the engine by increasing the cooling capacity of the engine, and can effectively suppress the temperature difference of the engine immediately after the engine is started.

[0017] The control unit may not set the upper limit of the intake air charge amount when the temperature of the upper end of the cylinder head exceeds a predetermined temperature when the engine is started. The upper limit is an upper limit for suppressing engine distortion, and is not an upper limit of the intake air charge amount for setting the maximum output of the engine specifications. In other words, the above-mentioned upper limit of the intake air charge amount is smaller than the upper limit of the intake air charge amount for setting the maximum output of the engine specifications.

[0018] the cylinder head has a passage for lubricating oil at an upper end of the cylinder head; The measurement unit may be attached to the engine and output a measurement signal related to a temperature of the lubricating oil to the control unit.

[0019] According to the study by the inventors of the present application, it was found that in an engine having a passage for lubricating oil at the upper end of the cylinder head, there is a high correlation between the temperature of the lubricating oil and the temperature of the upper end of the cylinder head. The control device suppresses the distortion of the engine as described above using a measurement unit that outputs a measurement signal related to the temperature of the lubricating oil, that is, a so-called oil temperature sensor. The control device does not require a special sensor.

[0020] The control unit may set an upper limit value qa_limit of the intake air charge amount in accordance with the following relational expression (1).

[0021] qa_limit = A × Toil + B × ε_a + C …(1) where Toil is the temperature of the lubricating oil, ε_a is the allowable distortion value of the cylinder head, and A, B, and C are constants.

[0022] According to the investigations of the present inventors, it was found that there is a linear relationship between the temperature difference ΔT between the temperature at the top end of the cylinder head and the temperature near the exhaust port during engine operation and the magnitude of distortion ε generated in the cylinder head, as shown in equation (2).

[0023] ε = {Temperature near the exhaust port (qa, thw) - Temperature at the top of the cylinder head (Toil, thw, qa)} × a + f(qa) …(2) where qa is the intake air charge, thw is the engine coolant temperature, and a is a constant. The intake air charge qa and the engine coolant thw are influencing factors of the temperature near the exhaust port. The lubricating oil temperature Toil, the intake air charge qa, and the engine coolant thw are influencing factors of the temperature at the top end of the cylinder head. The temperature difference ΔT is expressed by the following formula: ΔT = {Temperature near the exhaust port (qa, thw) - Temperature at the top of the cylinder head (Toil, thw, qa)} It is represented by:

[0024] If the maximum temperature is substituted for thw and the allowable distortion value ε_a is substituted for ε in equation (2) so that the distortion of the cylinder head is kept below the allowable value even when the coolant temperature reaches the maximum temperature, for example 100°C, the upper limit value qa_limit of the intake air charge amount can be expressed by the lubricating oil temperature Toil as in equation (1). Equation (1) is obtained from model equation (2) that predicts the distortion that occurs in the cylinder head.

[0025] According to formula (1), if the lubricating oil temperature Toil increases as the engine continues to operate after the engine starts, the upper limit value qa_limit of the intake air charge amount increases. This relaxes the restriction on the intake air charge amount when the driver depresses the accelerator pedal heavily. The engine output increases relatively.

[0026] In addition, when the lubricating oil temperature (Toil) is high, the temperature at the top of the cylinder head is high, so even if the engine output increases and the temperature near the exhaust port rises, the temperature difference between the temperature near the exhaust port and the temperature at the top of the cylinder head is small. Since the temperature difference in the cylinder head is small, engine distortion is suppressed.

[0027] the control unit has a table indicating a relationship between a temperature of the upper end portion of the cylinder head when the engine is started and an upper limit value of the intake air charging amount, the control unit, when starting the engine, uses the table to set a first upper limit value of the intake air filling amount based on a measurement signal from the measurement unit, and outputs a control signal to the adjustment unit according to an operation amount of the accelerator pedal within a range not exceeding the first upper limit value; The control unit may be configured to calculate a second upper limit value of the intake air filling amount using the relational equation after starting the engine, and after the second upper limit value exceeds the first upper limit value, output a control signal to the adjustment unit according to the amount of operation of the accelerator pedal within a range not exceeding the second upper limit value.

[0028] As described above, formula (1) is obtained by substituting the maximum temperature for the engine coolant temperature thw in formula (2). The actual coolant temperature when the engine is started is lower than the maximum temperature. Therefore, the upper limit value of the intake air charge amount calculated using formula (1) may be too small considering the actual coolant temperature immediately after the engine is started, and if used immediately after the engine is started, there is a possibility that the engine output will be restricted more than necessary.

[0029] Therefore, the control unit sets a first upper limit value of the intake air charge amount using a table when the engine is started. The table indicates the relationship between the temperature of the upper end of the cylinder head when the engine is started and the upper limit value of the intake air charge amount. The table may be created based on experiments carried out in advance. Immediately after the engine is started, the adjustment unit is controlled according to the first upper limit value of the intake air charge amount set using the table, so that the distortion of the engine is prevented from exceeding the allowable value without restricting the engine output more than necessary.

[0030] Furthermore, after the engine is started, the temperature of the engine coolant increases as the engine continues to operate. As a result, the second upper limit value of the intake air charge amount calculated using formula (1) becomes effective in suppressing engine distortion. After the second upper limit value exceeds the first upper limit value, the control unit outputs a control signal to the adjustment unit according to the amount of accelerator pedal operation within a range not exceeding the second upper limit value set according to formula (1). The engine control device can relax the engine output restriction as much as possible while suppressing engine distortion from exceeding an allowable value. As the engine warms up, the engine output approaches the output required by the driver. Effect of the Invention

[0031] The engine control device described above can prevent a large temperature difference in the engine from occurring, thereby preventing a large distortion from occurring in the engine. [Brief description of the drawings]

[0032] [Figure 1] FIG. 1 shows an engine control device. [Diagram 2] FIG. 2 is a block diagram of the engine control device. [Diagram 3] FIG. 3 is a diagram for explaining distortion occurring in the cylinder head, where the left diagram is a plan view of the cylinder head and the right diagram is a side view of the cylinder head. [Figure 4] FIG. 4 shows the temperature changes over time for the engine and the corresponding changes in strain. [Diagram 5] Figure 5 shows the relationship between temperature difference and strain in an engine. [Figure 6] FIG. 6 illustrates a table for setting the first upper limit value of the intake air charge amount. [Figure 7] FIG. 7 illustrates the change in the upper limit of the intake air charge after the engine starts. [Figure 8] FIG. 8 is a flowchart of the basic control of the engine. [Figure 9] FIG. 9 shows a procedure for setting the upper limit of the intake air charge amount. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Hereinafter, an embodiment of an engine control device will be described with reference to the drawings. The engine control device described here is merely an example.

[0034] (Overall structure of engine control device) Fig. 1 shows an engine control device 1. Fig. 2 shows a block diagram of the engine control device. Fig. 3 shows a cylinder head of the engine. The engine control device 1 is mounted on a four-wheeled automobile.

[0035] The engine control device 1 includes an engine 2. The engine 2 is a drive source for running an automobile. The engine 2 is, for example, a spark ignition engine. However, the engine 2 may be a compression ignition engine.

[0036] The engine 2 has a cylinder block 21. The cylinder block 21 has a cylinder 22. Although only one cylinder 22 is illustrated in FIG. 1, the engine 2 has a plurality of cylinders 22. The cylinder 22 forms a combustion chamber 24 together with a piston 23 inserted in the cylinder 22. The piston 23 reciprocates within the cylinder 22.

[0037] The engine 2 has a cylinder head 25. The cylinder head 25 is located on the cylinder block 21 and closes the upper end opening of the cylinder 22. The cylinder head 25 has an intake port 26 and an exhaust port 27.

[0038] The intake port 26 connects an intake pipe 28 to the cylinder 22. The intake pipe 28 sends intake air to the cylinder 22. A throttle valve 29 is located midway through the intake pipe 28. The throttle valve 29 is a butterfly valve, and by adjusting the opening degree thereof, the amount of intake air charged to the cylinder 22 is adjusted. The throttle valve 29 is one example of an adjustment unit.

[0039] Reference numeral 31 denotes an air cleaner 31. The air cleaner 31 is located at the tip of the intake pipe 28, and removes dust from the air to be supplied into the cylinder 22. Reference numeral 32 denotes a compressor 32 of a turbocharger 34. The compressor 32 compresses the air to be supplied into the cylinder 22. Reference numeral 33 denotes an intercooler 33, which cools the air compressed by the compressor 32.

[0040] The exhaust ports 27 are connected to the cylinders 22. The cylinder head 25 has an exhaust manifold 36, as shown in FIG. 3. The exhaust manifold 36 gathers together the multiple exhaust ports 27. The exhaust manifold 36 is connected to an exhaust pipe 35. The exhaust pipe 35 discharges exhaust gas from the cylinders 22.

[0041] Reference numeral 37 denotes a turbine 37 of the turbocharger 34. The turbine 37 rotates by the energy of the exhaust gas discharged from the cylinder 22. The turbine 37 is connected to the compressor 32, and the turbine 37 and the compressor 32 rotate together. Reference numeral 38 denotes a catalytic converter 38. The catalytic converter 38 purifies the exhaust gas.

[0042] The engine 2 has an intake valve 39. The intake valve 39 opens and closes the intake port 26 at a predetermined timing. The engine 2 has an exhaust valve 40. The exhaust valve 40 opens and closes the exhaust port 27 at a predetermined timing. Camshafts 41 and 42 located at the upper end of the cylinder head 25 operate the intake valve 39 and the exhaust valve 40, respectively.

[0043] The engine 2 has a spark plug 47. The tip of the spark plug 47 faces the inside of the cylinder 22. The spark plug 47 forcibly ignites the air-fuel mixture in the cylinder 22.

[0044] The engine 2 has an injector 48 (see FIG. 2). The injector 48 supplies fuel into the cylinder 22.

[0045] The engine 2 has a cooling water passage 43. The cooling water passage 43 is formed in the cylinder block 21 and the cylinder head 25. Cooling water flows through the cooling water passage 43. The cooling water cools the periphery of the cylinder 22 and the exhaust side of the engine 2, that is, the right side of the page in FIG.

[0046] The engine 2 has an oil gallery 44. The oil gallery 44 is connected to an oil pump 45. The oil pump 45 is immersed in lubricating oil stored in an oil pan 46. The oil pump 45 supplies lubricating oil to the engine 2 through the oil gallery 44. More specifically, the oil gallery 44 extends from the oil pan 46 through the cylinder block 21 to the cylinder head 25. The oil gallery 44 also extends to the upper end of the cylinder head 25 and can supply lubricating oil to the camshafts 41 and 42. In other words, the cylinder head 25 has a passage for lubricating oil at the upper end of the cylinder head 25. The lubricating oil supplied to the engine 2 returns to the oil pan 46 while being supplied to each part of the engine 2.

[0047] As shown in FIG. 2, the engine control device 1 includes a control unit 49. The control unit 49 is an ECU (Engine control Unit). The control unit 49 is a controller based on a known microcomputer. The control unit 49 includes a central processing unit (CPU), a memory, and an I / F circuit. The CPU executes a program. The memory is composed of, for example, a RAM (Random Access Memory) or a ROM (Read Only Memory). The memory stores programs and data. The I / F circuit inputs and outputs electric signals. The control unit 49 outputs control signals to the throttle valve 29, the spark plug 47, and the injector 48.

[0048] The engine control device 1 also has an accelerator opening sensor 55. The accelerator opening sensor 55 outputs to the control unit 49 a signal corresponding to the amount of depression of the accelerator pedal operated by the driver.

[0049] The engine control device 1 has a vehicle speed sensor 56. The vehicle speed sensor 56 outputs to the control unit 49 a signal corresponding to the vehicle speed of the automobile.

[0050] The engine control device 1 has an oil temperature sensor 57. The oil temperature sensor 57 is attached to the engine 2 as shown in Fig. 1. The oil temperature sensor 57 outputs a signal corresponding to the temperature of the lubricating oil flowing through the oil gallery 44 to the control unit 49. More specifically, the oil temperature sensor 57 is attached to the cylinder block 21, and measures the temperature of the lubricating oil supplied from the oil pan 46 to the cylinder head 25.

[0051] The control unit 49 has, as functional blocks, a torque calculation unit 50, an intake charge amount calculation unit 51, a fuel injection amount / timing calculation unit 52, an ignition timing calculation unit 53, and a memory unit .

[0052] The torque calculation unit 50 calculates a target torque from a target acceleration of the vehicle based on the measurement signals of an accelerator opening sensor 55 and a vehicle speed sensor 56 .

[0053] The intake air charge calculation unit 51 calculates a target intake air charge for the cylinder 22 based on the target torque. The intake air charge calculation unit 51 corrects the target intake air charge, which is set according to the depression amount of the accelerator pedal, based on an upper limit value, which will be described in detail later. The upper limit value is set according to the temperature of the lubricating oil.

[0054] An injection amount / timing calculation unit 52 calculates the fuel injection amount and injection timing based on the corrected target intake air charge amount.

[0055] An ignition timing calculation unit 53 calculates the ignition timing based on the corrected target intake air charge amount.

[0056] The storage unit 54 stores a model formula and a table 6 for setting the upper limit value qa_limit of the intake air charge amount, which will be described in detail later.

[0057] (Control to suppress distortion of cylinder head) The engine control device 1 is characterized by being able to suppress thermal distortion in the cylinder head 25. Thermal distortion in the cylinder head 25 is caused by the temperature difference between a high-temperature portion and a low-temperature portion. A large temperature difference causes the amount of deformation of the engine 2 to be non-uniform, and the non-uniform amount of deformation leads to large distortion.

[0058] 3 is a diagram illustrating thermal distortion occurring in the cylinder head 25. The left diagram in FIG. 3 is a plan view of the cylinder head 25, and the right diagram in FIG.

[0059] For example, in an environment where the outside air temperature is below minus 20 degrees Celsius, a driver in a car starts the engine 2 by operating the starter switch, and immediately after starting, the driver depresses the accelerator pedal to drive the car with the throttle valve 29 fully open. In this case, the temperature of the exhaust port 27 and the exhaust manifold 36 formed in the cylinder head 25 rises locally and rapidly. The shaded areas in FIG. 3 are examples of high-temperature areas. While the exhaust-side temperature of the cylinder head 25 rises, a situation may occur in which the temperature of a part away from the exhaust-side part of the cylinder head 25, for example, near the upper end of the cylinder head 25, remains significantly lower due to the extremely low outside air temperature. In this case, the cylinder head 25 may be significantly distorted like a fan due to the large temperature difference, as shown by the white arrow in FIG. 3.

[0060] Fig. 4 illustrates the time variations in various temperatures of the engine 2 (i.e., the upper diagram in Fig. 4) and the changes in distortion caused in the cylinder head 25 due to the temperature variations (i.e., the lower diagram in Fig. 4) when the engine 2 starts in an extremely low temperature environment and then operates with the throttle valve 29 substantially fully open. The vertical axis in the upper diagram in Fig. 4 indicates temperature, and the horizontal axis indicates the passage of time. The vertical axis in the lower diagram in Fig. 4 indicates distortion, and the horizontal axis indicates the passage of time.

[0061] Immediately after the engine 2 is started, the throttle valve 29 is fully opened and the engine 2 is operated, so that the exhaust port 27 and the exhaust manifold 36 formed in the cylinder head 25, that is, the exhaust side temperature, rises rapidly as described above. Following the rise in the exhaust side temperature, the engine 2 cooling water temperature also gradually rises. However, the rate of rise in the engine 2 cooling water temperature is lower than the rate of rise in the exhaust side temperature. At a specific timing, that is, at time t0 in FIG. 4, the cooling water thermostat valve opens, so that the rise in the engine 2 cooling water temperature becomes gradual. After time t0, the engine 2 cooling water temperature is maintained in a specific temperature range. When the thermostat valve opens, the cooling water cooled by the radiator is supplied to the exhaust port 27 and the exhaust manifold 36 of the cylinder head 25, so that the exhaust side temperature gradually drops.

[0062] Unlike the rise in exhaust-side temperature, the temperature of the upper end of the cylinder head 25 rises slowly. This is because the oil gallery 44 is located at the upper end of the cylinder head 25, and the upper end of the cylinder head 25 is cooled by low-temperature lubricating oil. Because the temperature of the upper end of the cylinder head 25 rises slowly, the temperature difference ΔT between the exhaust-side temperature and the upper end temperature of the cylinder head 25 gradually increases after the engine 2 is started. The temperature difference ΔT is maximum just before the exhaust-side temperature starts to drop.

[0063] 4, the distortion of the cylinder head 25 gradually increases with an increase in the exhaust side temperature after the start of the engine 2. The distortion reaches a maximum when the temperature difference ΔT reaches a maximum.

[0064] After the distortion of the cylinder head 25 reaches a maximum, the temperature difference ΔT gradually decreases due to the combination of the decrease in the exhaust side temperature and the increase in the upper end temperature. The distortion of the cylinder head 25 also gradually decreases.

[0065] 4, after the engine 2 is started, the temperature of the upper end of the cylinder head 25 and the temperature of the lubricating oil, i.e., the oil temperature, rise at approximately the same rate. If the oil temperature is measured instead of the temperature of the upper end of the cylinder head 25, the measured oil temperature can be used as a substitute for the temperature of the upper end of the cylinder head 25.

[0066] From FIG. 4, it is considered that there is a correlation between the temperature difference ΔT between the exhaust side temperature and the upper end temperature of the cylinder head 25 and the distortion occurring in the cylinder head 25. Therefore, the inventors of the present application measured the temperature difference ΔT and the magnitude of the distortion of the cylinder head 25 in various operating states of the engine 2 with different rotation speeds and / or loads. FIG. 5 illustrates the measurement results. The vertical axis of FIG. 5 is the distortion ε of the cylinder head 25, and the horizontal axis is the temperature difference ΔT. From FIG. 5, it can be seen that there is a linear relationship between the temperature difference ΔT and the distortion ε in the cylinder head 25, and the magnitude of the slope a is approximately the same regardless of the operating state of the engine 2, while the intercept changes depending on the operating state of the engine 2.

[0067] Based on FIG. 5, the inventors of the present application have constructed a model for predicting the strain ε occurring in the cylinder head 25 from the temperature difference ΔT, as shown in the following equations (3) and (4). ε = ΔT×a + f(qa) …(3) ΔT = {exhaust side temperature (qa, thw) - top end temperature (Toil, thw, qa)} … (4) where qa is the intake charge, thw is the engine coolant temperature, and a is a constant (i.e., the slope). The intake charge qa and the coolant temperature thw are influencing factors of the exhaust side temperature, and the intake charge qa, the coolant temperature thw, and the lubricating oil temperature Toil are influencing factors of the upper end temperature.

[0068] Even if an attempt is made to suppress distortion of the cylinder head 25 by controlling the flow rate of the coolant, as shown in Fig. 4, immediately after the start of the engine 2, the distortion of the cylinder head 25 reaches its maximum before the coolant can suppress the distortion of the cylinder head 25. Therefore, the flow rate control of the coolant is not effective in suppressing distortion of the cylinder head 25 immediately after the start of the engine 2.

[0069] Therefore, the engine control device 1 suppresses distortion of the cylinder head 25 by adjusting the intake air charge amount. In other words, the engine control device 1 relatively reduces the intake air charge amount even if the driver depresses the accelerator pedal. Limiting the intake air charge amount suppresses the rise in the exhaust side temperature. Suppressing the rise in the exhaust side temperature suppresses the temperature difference ΔT and the distortion of the cylinder head 25 from increasing.

[0070] Specifically, in the distortion model of equations (3) and (4), the upper limit qa_limit of the intake air charge amount is determined so that the distortion ε of the cylinder head 25 is kept below the allowable value ε_a even when the coolant temperature thw reaches the maximum temperature, for example, 100° C. In equations (3) and (4), the allowable value ε_a is substituted for the distortion ε, 100° C. is substituted for the coolant temperature thw, and the upper limit qa_limit is substituted for the intake air charge amount qa, and the upper limit qa_limit of the intake air charge amount is expressed in terms of the lubricating oil temperature Toil, resulting in the following equation (5). qa_limit = A × Toil + B × ε_a + C …(5) where A, B, and C are constants.

[0071] The control unit 49 uses equation (5) to determine the target intake air filling amount based on the lubricating oil temperature Toil measured by the oil temperature sensor 57 and the measurement values ​​measured by the accelerator opening sensor 55 and the vehicle speed sensor 56. More specifically, the target intake air filling amount is set by limiting the target intake air filling amount based on the measurement values ​​measured by the accelerator opening sensor 55 and the vehicle speed sensor 56 by the upper limit value qa_limit of the intake air filling amount calculated using equation (5).

[0072] Even if the driver depresses the accelerator pedal, the intake air filling amount is limited, so the increase in the exhaust side temperature is suppressed. The temperature difference ΔT of the cylinder head 25 is suppressed from increasing. The distortion of the cylinder head 25 does not exceed the allowable value ε_a. The distortion of the cylinder head 25 is suppressed from increasing.

[0073] When the driver's accelerator pedal depression amount is small and the target intake air charge amount is not limited by the upper limit value of the intake air charge amount, the output of engine 2 satisfies the output required by the driver.

[0074] Here, the allowable value ε_a of the distortion of the cylinder head 25 may be set as large as possible within a range in which cracks do not occur in the cylinder head 25. This is because the larger the allowable value ε_a of distortion, the more relaxed the upper limit of the intake air filling amount is, and the output of the engine 2 approaches the output required by the driver. The technology disclosed herein, which uses a model for predicting the distortion ε occurring in the cylinder head 25, achieves, at a high level, both suppressing the distortion of the cylinder head 25 to the allowable value or less and relaxing the output limit of the engine 2 as much as possible.

[0075] The allowable distortion value ε_a of the cylinder head 25 may be set in consideration of residual distortion of the cylinder head 25 during manufacture and thermal distortion.

[0076] According to formula (5), if the lubricating oil temperature Toil increases as the engine 2 continues to operate after the engine 2 starts, the upper limit value qa_limit of the intake air charge amount increases. If the upper limit value qa_limit increases, the restriction on the intake air charge amount when the driver deeply depresses the accelerator pedal is relaxed. The output of the engine 2 increases relatively. Note that when the lubricating oil temperature Toil is high, the upper end temperature of the cylinder head 25 is high, so even if the output of the engine 2 increases and the exhaust side temperature increases, the temperature difference ΔT between the exhaust side temperature and the upper end temperature is small.

[0077] Here, equation (5) is an equation obtained by substituting the maximum temperature for the engine coolant temperature thw in equations (3) and (4). The actual coolant temperature when engine 2 is started is lower than the maximum temperature. Therefore, the upper limit value qa_limit of the intake air charge amount calculated using equation (5) may be too small in consideration of the actual coolant temperature of engine 2, and using equation (5) immediately after engine 2 is started may result in unnecessarily limiting the output of engine 2.

[0078] Therefore, immediately after the start of the engine 2, the engine control device 1 sets the first upper limit value of the intake air charge amount using table 6 shown in FIG. 6, instead of using equation (5).

[0079] Table 6 in FIG. 6 shows the relationship between the temperature of the lubricating oil when the engine 2 is started (i.e., the oil temperature at start-up) and the upper limit of the intake air charge amount (i.e., the first upper limit value qa_limit 1). The temperature of the lubricating oil may be the temperature of the upper end of the cylinder head 25. Table 6 is created based on experiments carried out in advance. qa_limit 3 in FIG. 6 shows the upper limit value of the intake air charge amount that determines the maximum output in the specifications of the engine 2, that is, the third upper limit value. The third upper limit value is a fixed value determined for the engine 2. The first upper limit value qa_limit 1 is smaller than the third upper limit value qa_limit 3.

[0080] As shown by the solid line in Table 6, the first upper limit value qa_limit 1 of the intake air charge amount is set when the oil temperature at start-up is equal to or lower than T1. Temperature T1 corresponds to the temperature of the lubricating oil when engine 2 is started at an extremely low outside air temperature. T1 may be set to a temperature of, for example, about minus 20-30°C. If the temperature of the lubricating oil when engine 2 is started exceeds T1, the first upper limit value qa_limit 1 of the intake air charge amount is not set. As will be described in detail later, if the first upper limit value qa_limit 1 of the intake air charge amount is not set, the upper limit value of the intake air charge amount using equation (5), i.e., the second upper limit value qa_limit 2, is not set either.

[0081] In table 6, the first upper limit value qa_limit 1 of the intake air charge amount is set smaller as the oil temperature at start-up is lower. This is because the lower the oil temperature at start-up is, the lower the temperature at the upper end of the cylinder head 25 is, and therefore the intake air charge amount must be reduced in order to suppress the temperature difference in the cylinder head 25. The minimum value of the first upper limit value qa_limit 1 may be, for example, about 70% of the third upper limit value. In other words, the output of the engine 2 may be reduced by up to about 30% of the maximum output.

[0082] Next, the setting of the upper limit of the intake air charge amount by the control unit 49 will be described with reference to Fig. 7. The vertical axis of Fig. 7 represents the upper limit of the intake air charge amount qa_limit, and the horizontal axis represents the passage of time. Fig. 7 illustrates the change in the upper limit of the intake air charge amount after the engine 2 is started.

[0083] When starting the engine 2, the control unit 49 determines a first upper limit value qa_limit 1 of the intake air filling amount using the table 6, and sets the target intake air filling amount by limiting the target intake air filling amount based on the measurement values ​​measured by the accelerator opening sensor 55 and the vehicle speed sensor 56 using the first upper limit value qa_limit 1 of the intake air filling amount. The first upper limit value qa_limit 1 of the intake air filling amount is a constant value as shown in FIG.

[0084] The control unit 49 also calculates the second upper limit value qa_limit 2 of the intake air charge amount using the formula (5) while the engine 2 continues to operate after the engine 2 is started. The second upper limit value qa_limit 2 increases as the engine 2 continues to operate and the temperature Toil of the lubricating oil increases. The control unit 49 compares the first upper limit value qa_limit 1 set at the start of the engine 2 with the second upper limit value qa_limit 2 of the intake air charge amount updated using the formula (5). As illustrated by the dashed line in FIG. 7, the second upper limit value qa_limit 2 of the intake air charge amount calculated using the formula (5) is smaller than the first upper limit value qa_limit 1 during the period from the start of the engine 2 to time t1. Immediately after the start of the engine 2, the second upper limit value qa_limit 2 of the intake air charge amount may limit the intake air charge amount more than necessary.

[0085] When the second upper limit value qa_limit2 of the intake air filling amount exceeds the first upper limit value qa_limit1 at time t1, the controller 49 switches the upper limit value qa_limit of the intake air filling amount from the first upper limit value qa_limit1 to the second upper limit value qa_limit2.

[0086] 7, the controller 49 continues to calculate the second upper limit value qa_limit 2 of the intake air charge amount using the equation (5). As the temperature of the lubricating oil increases, the second upper limit value qa_limit 2 also gradually increases. As the warm-up of the engine 2 progresses, the limitation on the output of the engine 2 is relaxed.

[0087] As the temperature of the engine 2 increases over time, the second upper limit value qa_limit 2 of the intake air charge calculated using the formula (5) becomes larger. As shown by the dashed line in FIG. 7, the second upper limit value qa_limit 2 of the intake air charge exceeds the third upper limit value qa_limit 3 (see time t2 in FIG. 7). As described above, the third upper limit value qa_limit 3 of the intake air charge is the upper limit value of the intake air charge that determines the maximum output in the specifications of the engine 2, and is a fixed value determined for the engine 2. After the second upper limit value qa_limit 2 of the intake air charge exceeds the third upper limit value qa_limit 3, the control unit 49 sets the target intake air charge using the third upper limit value qa_limit 3. The intake air charge of the engine 2 is not substantially limited. The second upper limit value qa_limit 2 is smaller than the third upper limit value qa_limit 3.

[0088] (Engine Control) Next, control of the engine 2, including adjustment control of the intake air charge amount for suppressing the above-mentioned distortion of the cylinder head 25, will be described with reference to the drawings.

[0089] FIG. 8 shows a flowchart of the basic control of the engine 2. The flowchart in FIG. 8 is executed by the control unit 49. In step S81 after the start, the control unit 49 reads the measurement signals of each sensor. In the following step S82, the control unit 49 calculates a target acceleration of the automobile based on the measurement signals of the accelerator opening sensor 55 and the vehicle speed sensor 56. In addition, in step S83, the control unit 49 calculates a target torque from the target acceleration. In the following step S84, the control unit 49 calculates a target intake air filling amount from the target torque. The target intake air filling amount calculated in S84 is a target intake air filling amount according to the amount of operation of the accelerator pedal by the driver.

[0090] In step S85, the control unit 49 corrects the target intake air filling amount based on the target intake air filling amount calculated in step S84 and the upper limit value qa_limit of the intake air filling amount. That is, if the target intake air filling amount calculated in step S84 exceeds the upper limit value qa_limit of the intake air filling amount, the control unit 49 sets the upper limit value qa_limit of the intake air filling amount as the target intake air filling amount. If the driver depresses the accelerator pedal heavily, the intake air filling amount is limited. If the target intake air filling amount calculated in step S84 is equal to or less than the upper limit value qa_limit of the intake air filling amount, the control unit 49 sets the target intake air filling amount calculated in step S84 as the target intake air filling amount as it is.

[0091] In step S86, the control unit 49 sets the target throttle opening based on the corrected target intake air charge amount. The control unit 49 also calculates the target injection amount / injection timing in step S87. In step S88, the control unit 49 calculates the target ignition timing.

[0092] In step S89, the control unit 49 adjusts the opening of the throttle valve 29 so that the throttle opening becomes the one set in step S86. In step S810, the control unit 49 causes the injector 48 to inject fuel based on the target injection amount / injection timing calculated in step S87. In step S811, the control unit 49 causes the ignition plug 47 to ignite at the target ignition timing set in step S88.

[0093] 9 is a flowchart showing a procedure for setting the upper limit of the intake air charge amount. The upper limit of the intake air charge amount qa_limit set in FIG. 9 is used in step S85 of the flow in FIG.

[0094] First, in step S91 after starting, the control unit 49 reads the measurement signal of the oil temperature sensor 57. In the following step S92, the control unit 49 determines whether or not the engine 2 has just been started. If the engine 2 has just been started, the process of FIG. 9 proceeds to step S93. If the engine 2 has not just been started, the process of FIG. 9 proceeds to step S95.

[0095] In step S93, the control unit 49 judges whether the lubricating oil temperature Toil is equal to or lower than T1 (see also FIG. 6). If the judgment in step S93 is No, the process proceeds to step S910. This is because the lubricating oil temperature Toil at the start of the engine 2 is relatively high, and therefore no increase in distortion due to the above-mentioned temperature difference ΔT occurs. The control unit 49 selects the third upper limit value qa_limit 3 as the upper limit value of the intake air filling amount. Neither the first upper limit value qa_limit 1 nor the second upper limit value qa_limit 2 is set.

[0096] If the determination in step S93 is Yes, the process in Fig. 9 proceeds to step S94. In step S94, the control unit 49 sets a first upper limit value qa_limit 1 from the temperature Toil of the lubricating oil by using Table 6 in Fig. 6.

[0097] In the following step S95, the control unit 94 sets a second upper limit value qa_limit 2 from the temperature Toil of the lubricating oil by using the model formula of equation (5).

[0098] In step S96, the controller 49 determines whether the second upper limit value qa_limit 2 is greater than the first upper limit value qa_limit 1. If the second upper limit value qa_limit 2 is equal to or less than the first upper limit value qa_limit 1, the process in Fig. 9 proceeds to step S97, where the controller 49 selects the first upper limit value qa_limit 1 as the upper limit value of the intake air charge amount. This corresponds to the period from the start of the engine 2 to time t1 in Fig. 7.

[0099] 9 proceeds from step S96 to step S98, where the controller 49 selects the second upper limit qa_limit 2 as the upper limit of the intake air charge amount. This corresponds to the period after time t1 in FIG. 7.

[0100] In step S99 after step S98, the controller 49 determines whether the second upper limit value qa_limit 2 is greater than the third upper limit value qa_limit 3. If the second upper limit value qa_limit 2 is less than the third upper limit value qa_limit 3, the process of FIG. 9 returns. The controller 49 selects the second upper limit value qa_limit 2 as the upper limit value of the intake air charge amount. This corresponds to the period from time t1 to t2 in FIG. 7.

[0101] If the second upper limit qa_limit 2 exceeds the third upper limit qa_limit 3, the process in Fig. 9 proceeds to step S910. The controller 49 selects the third upper limit qa_limit 3 as the upper limit of the intake air charge amount. This corresponds to the period after time t2 in Fig. 7.

[0102] The engine control device 1 sets the upper limit value qa_limit 1 or qa_limit 2 of the intake air filling amount in advance according to the temperature Toil of the lubricating oil when the engine 2 is started, in other words, before the temperature difference ΔT between the upper end temperature of the cylinder head 25 and the exhaust side temperature becomes large, and limits the target intake air filling amount as necessary.

[0103] Here, unlike the above-mentioned control device, a control is considered in which the upper limit value qa_limit of the intake air charge amount is set to limit the intake air charge amount after the temperature difference ΔT between the upper end temperature and the exhaust side temperature of the cylinder head 25 becomes large during operation of the engine 2. In this case, the temperature difference ΔT between the upper end temperature and the exhaust side temperature of the cylinder head 25 is not large immediately after the start of the engine 2, so the target intake air charge amount is not substantially limited, while, as described above, when the operation of the engine 2 continues with the accelerator pedal depressed and the throttle valve 29 fully opened, the exhaust side temperature rises rapidly, the temperature difference ΔT between the upper end temperature and the exhaust side temperature of the cylinder head 25 becomes large, and, for example, the second upper limit value qa_limit 2 is set. As a result, the target intake air charge amount may be limited by the set upper limit value. In this control, the output of the engine 2 is limited as the temperature of the engine 2 increases, which causes a sense of discomfort for the driver.

[0104] In response to this, the engine control device 1 previously described sets the upper limit value qa_limit of the intake air charge amount before the temperature difference ΔT between the upper end temperature of the cylinder head 25 and the exhaust side temperature becomes large, and limits the target intake air charge amount. The upper limit value qa_limit of the intake air charge amount gradually increases, as shown in FIG. 7. In other words, as the engine 2 warms up, the limit on the target intake air charge amount is relaxed, so that the output of the engine 2 approaches the output required by the driver. As a result, the driver is prevented from feeling uncomfortable.

[0105] In addition, since the engine control device 1 does not suppress distortion of the engine 2 by increasing the cooling capacity of the engine 2, it has an advantage that the temperature difference of the engine 2 can be effectively suppressed immediately after the engine 2 is started.

[0106] Furthermore, the engine control device 1 uses the oil temperature sensor 57 to perform the distortion suppression control of the engine 2 described above. The engine control device 1 does not require a special sensor. Note that the technology disclosed herein does not exclude the use of a sensor other than the oil temperature sensor 57. The temperature difference of the cylinder head 25 can be determined based on various parameters related to the operation of the engine.

[0107] It should be noted that the application of the technology disclosed herein is not limited to the engine described above, and the technology disclosed herein can be applied to various engines. [Explanation of symbols]

[0108] 1 Engine control device 2 Engine 22 cylinders 25 Cylinder head 26 Intake port 27 Exhaust port 29 Throttle valve (adjustment part) 44 Oil Gallery (passageway) 49 Control Unit 57 Oil temperature sensor (measurement part) 6 Tables

Claims

1. an adjustment unit that adjusts an intake air filling amount for the cylinder in response to an accelerator pedal depression amount; a measuring unit that outputs a measurement signal related to a temperature of an upper end portion of a cylinder head having an intake port and an exhaust port communicating with the cylinder; a control unit that sets the upper limit of the intake air filling amount to a smaller value the lower the temperature of the upper end of the cylinder head is, based on a measurement signal from the measurement unit when the temperature of the upper end of the cylinder head is below a predetermined temperature, and outputs a control signal to the adjustment unit according to the amount of operation of the accelerator pedal within a range that does not exceed the upper limit of the intake air filling amount.

2. 2. The engine control device according to claim 1, the cylinder head has a passage for lubricating oil at an upper end of the cylinder head; The measurement unit is attached to the engine and outputs a measurement signal related to the temperature of the lubricating oil to the control unit.

3. 3. The engine control device according to claim 2, The control unit sets an upper limit value qa_limit of the intake air filling amount in accordance with the following relational expression. qa_limit = A × Toil + B × ε_a + C where Toil is the lubricating oil temperature, ε_a is the allowable distortion of the cylinder head, and A, B, and C are constants.

4. 4. The engine control device according to claim 3, the control unit has a table indicating a relationship between a temperature of the upper end portion of the cylinder head when the engine is started and an upper limit value of the intake air charging amount, the control unit, when starting the engine, uses the table to set a first upper limit value of the intake air filling amount based on a measurement signal from the measurement unit, and outputs a control signal to the adjustment unit according to an operation amount of the accelerator pedal within a range not exceeding the first upper limit value; An engine control device, wherein the control unit calculates a second upper limit value of the intake air filling amount using the relational equation after the engine is started, and after the second upper limit value exceeds the first upper limit value, outputs a control signal to the adjustment unit corresponding to the amount of operation of the accelerator pedal within a range not exceeding the second upper limit value.

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