vehicle

Abstract

To make closing speed of a variable nozzle (closing speed of a VN opening) in normal control and auxiliary brake control suitable.SOLUTION: A vehicle is mounted with an engine having a variable nozzle turbo. A control device executes normal control for controlling an opening of a variable nozzle (VN opening Tv) to a target VN opening To on the basis of an operating state of the engine and auxiliary brake control for controlling the VN opening Tv to deceleration time target VN opening Tdo during deceleration of the vehicle. During the normal control, when the VN opening Tv is controlled to a closing side, the VN opening Tv is controlled by using first speed vc1 and second speed vc2. During the auxiliary brake control, when the VN opening Tv is controlled to the closing side, the VN opening tv is controlled by using third speed vc3 and fourth speed vc4.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to vehicles, and more particularly to vehicles equipped with an internal combustion engine with an exhaust brake. [Background technology]

[0002] In vehicles, in order to increase engine braking force, an exhaust brake is sometimes adopted that increases the exhaust pressure by narrowing the cross-sectional area of ​​the exhaust passage of the internal combustion engine, thereby increasing the pumping loss of the internal combustion engine. For example, in JP 2022-181282 A (Patent Document 1), the opening of the variable nozzle (nozzle vane) of a variable nozzle turbo is reduced (by narrowing the nozzle opening) to provide an exhaust brake function.

[0003] In Patent Document 1, a limit value for exhaust pressure in the exhaust manifold is calculated from the viewpoint of reliability of the turbocharger or the engine body, an effective nozzle area corresponding to this limit value is found, and a lower limit value for the variable nozzle opening (VN opening) corresponding to this effective nozzle area is set.Then, when the exhaust brake is activated, the VN opening is controlled so that it becomes the lower limit value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-181282 Summary of the Invention [Problem to be solved by the invention]

[0005] A variable nozzle turbo controls the boost pressure by controlling the VN opening. For example, boost pressure control is performed to control the VN opening so that the boost pressure becomes a target boost pressure according to the operating state of the internal combustion engine. During boost pressure control, the closing speed of the VN opening (closing speed) is set so that the output and emissions of the internal combustion engine become appropriate. In this disclosure, boost pressure control according to the operating state of the internal combustion engine is also referred to as normal control.

[0006] The exhaust brake is activated when the vehicle decelerates to increase engine braking force. When the vehicle decelerates (when the accelerator pedal is not depressed while the vehicle is moving), the internal combustion engine generally performs fuel cut-off during deceleration. Furthermore, when the exhaust brake using a variable nozzle turbo is activated, the VN opening is often reduced (the VN opening becomes more throttling) compared to normal control in order to increase exhaust pressure. Therefore, when the exhaust brake is activated, it is preferable to set the VN opening closing speed taking into consideration the deceleration required by the vehicle, rather than the output or emissions of the internal combustion engine. In this disclosure, control of the variable nozzle turbo (control of the VN opening) when the exhaust brake is activated is also referred to as auxiliary brake control.

[0007] An object of the present disclosure is to optimize the closing speed of the variable nozzle (closing speed of the VN opening) in normal control and auxiliary brake control. [Means for solving the problem]

[0008] (1) A vehicle according to the present disclosure is a vehicle equipped with an internal combustion engine having a variable nozzle turbocharger in an exhaust passage. The vehicle is equipped with a control device that controls the opening of the variable nozzle of the variable nozzle turbocharger. The control device performs normal control, which controls the opening of the variable nozzle to a target opening based on the operating state of the internal combustion engine, and auxiliary brake control, which controls the opening of the variable nozzle to a deceleration target opening when the vehicle decelerates. During normal control, the control device controls the opening of the variable nozzle based on a normal closing speed, and during auxiliary brake control, the control device controls the opening of the variable nozzle based on a deceleration closing speed.

[0009] According to this configuration, the control device executes normal control to control the opening of the variable nozzle to a target opening based on the operating state of the internal combustion engine, and during normal control, controls the opening of the variable nozzle based on the normal closing speed.The control device executes auxiliary brake control to control the opening of the variable nozzle to the deceleration target opening when the vehicle decelerates, and during auxiliary brake control, controls the opening of the variable nozzle based on the deceleration closing speed.

[0010] During normal control, the opening of the variable nozzle (VN opening) can be controlled by the normal closing speed, taking into account the output and emissions of the internal combustion engine, and during vehicle deceleration, the VN opening can be controlled by the deceleration closing speed, taking into account the required deceleration. Therefore, the closing speed of the VN opening during normal control and auxiliary brake control can be optimized.

[0011] (2) In the above (1), the closing speed during deceleration may be set so that the expansion ratio in the turbine of the variable nozzle turbo is equal to or less than a predetermined value.

[0012] When the exhaust brake is activated (when auxiliary brake control is being executed), the VN opening is often reduced (the VN opening becomes more throttling) compared to normal control in order to increase exhaust pressure. If the variable nozzle is suddenly closed to the point where the VN opening is small, the expansion ratio of the variable nozzle turbo's turbine becomes excessive, raising concerns that the turbine may be damaged. With this configuration, the closing speed during deceleration is set so that the expansion ratio is below a predetermined value, making it possible to prevent the expansion ratio from becoming excessive while taking into account the vehicle's deceleration.

[0013] (3) In the above (1) and (2), the internal combustion engine includes an EGR passage that recirculates exhaust gas upstream of the turbine to an intake passage, and an EGR valve provided in the EGR passage. The control device executes EGR control that controls the opening degree of the EGR valve based on the operating state of the internal combustion engine. The normal closing speed may be set to prevent interference between the normal control and the EGR control.

[0014] According to this configuration, the control device executes EGR control. The EGR passage recirculates exhaust gas received by the turbine back into the intake passage. When the VN opening is controlled to the closing side, the exhaust pressure rises, increasing the exhaust gas recirculation amount (EGR amount). If the EGR amount increases due to the increase in exhaust pressure, the desired EGR rate cannot be maintained, so the control device controls the opening of the EGR valve. Depending on the normal closing speed of the VN opening, controlling the EGR valve opening may not be able to adequately suppress changes in the EGR rate due to the increase in exhaust pressure. With this configuration, the normal closing speed of the VN opening is set to avoid interference between the normal control of the variable nozzle and the EGR control, so the desired EGR rate (EGR amount) can be maintained.

[0015] (4) In the above (1) to (3), the normal closing speed includes a first speed and a second speed slower than the first speed, and the second speed is the closing speed when the deviation between the opening of the variable nozzle and the target opening is equal to or less than a first predetermined value. The deceleration closing speed includes a third speed and a fourth speed slower than the third speed, and the fourth speed is the closing speed when the deviation between the opening of the variable nozzle and the target opening during deceleration is equal to or less than a second predetermined value. The third speed may be set to be equal to or less than the first speed.

[0016] With this configuration, during normal control, when the deviation between the VN opening and the target opening is greater than a first predetermined value, the variable nozzle is controlled to close at a first speed. When the deviation becomes equal to or less than the first predetermined value, the variable nozzle is controlled to the target opening at a second speed slower than the first speed. Furthermore, during auxiliary brake control, when the deviation between the VN opening and the target opening during deceleration is greater than a second predetermined value, the variable nozzle is controlled to close at a third speed. When the deviation becomes equal to or less than the second predetermined value, the variable nozzle is controlled to the target opening at a fourth speed slower than the third speed. Therefore, the VN opening can be quickly controlled to the target opening or the target opening during deceleration while suppressing overshoot.

[0017] When auxiliary brake control is performed, the VN opening is often reduced (the VN opening becomes more throttling) compared to normal control in order to increase exhaust pressure. With this configuration, the third speed is set to be equal to or lower than the first speed, so the VN opening is closed more slowly at the start of auxiliary brake control compared to the start of normal control. Therefore, even when the VN opening is closed to a smaller value than during normal control during auxiliary brake control, the expansion ratio in the turbine can be prevented from becoming excessive.

[0018] (5) In the above (1) to (4), the control device may set the target opening degree during deceleration based on the target deceleration of the vehicle.

[0019] According to this configuration, a desired deceleration (engine braking force) can be obtained during auxiliary brake control. [Effects of the Invention]

[0020] According to the present disclosure, the closing speed of the variable nozzle (closing speed of the VN opening) can be optimized in normal control and auxiliary brake control. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a diagram showing a schematic configuration of a vehicle according to an embodiment of the present invention; [Figure 2] 2 is a flowchart of VN opening control executed by a control device 200 in the present embodiment. [Figure 3] 10 is a flowchart of normal control. [Figure 4] FIG. 10 is a diagram illustrating an overview of speed control of VN opening. [Figure 5] 4 is a flowchart of auxiliary brake control. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, the same or corresponding parts in the drawings are designated by the same reference numerals, and description thereof may not be repeated.

[0023] (Embodiment 1) FIG. 1 is a diagram showing a schematic configuration of a vehicle V according to this embodiment. The vehicle V includes an engine 1, a transmission 3, a differential gear 5, drive wheels 7, and a control device 200. The engine 1 is a compression autoignition internal combustion engine (diesel engine) and corresponds to the "internal combustion engine" of the present disclosure. The engine 1 is a drive source for the vehicle V, and the output of the engine 1 is transmitted to the drive wheels 7 via the transmission 3 and the differential gear 5 to drive the vehicle V.

[0024] The engine 1 comprises an engine body 10, an air cleaner 20, an intake passage 22, an intercooler 26, an intake manifold 28, a variable nozzle supercharger (variable nozzle turbo) 30, an exhaust manifold 50, an exhaust passage 52, an exhaust purification device 56, and an EGR device (exhaust gas recirculation device) 60.

[0025] The engine body 10 includes a cylinder head 11, a cylinder 12, a piston 13, and a fuel injection valve 15. The piston 13 is inserted into the cylinder 12 so as to be able to move up and down. A combustion chamber 14 is formed by the space surrounded by the top of the piston 13, the cylinder head 11, and the cylinder 12.

[0026] The fuel injection valve 15 is an injector provided in the cylinder head 11 that sprays fuel into the combustion chamber 14. Fuel stored in a fuel tank (not shown) is pressurized to a predetermined pressure by a high-pressure fuel pump and supplied to a common rail (neither is shown). The fuel supplied to the common rail is supplied to the fuel injection valve 15 and injected into the combustion chamber 14 from a nozzle of the fuel injection valve 15. The fuel injection valve 15 supplies a commanded fuel injection amount Qf into the combustion chamber 14 at a commanded timing (injection timing) in response to a control signal from the control device 200.

[0027] Air (fresh air) is drawn into an intake passage (intake pipe) 22 via an air cleaner 20. A compressor 32 of a variable nozzle supercharger (variable nozzle turbocharger) 30 is provided in the intake passage 22 downstream of the air cleaner 20. The compressor 32 supercharges the intake air. The supercharged air is cooled by an intercooler 26.

[0028] An intake throttle valve (diesel throttle) 25 is disposed in the intake passage 22 downstream of the intercooler 26. The intake passage 22 is connected to an intake manifold 28, and intake air flows into the combustion chamber 14 from an intake port formed in the engine body 10 (cylinder head 11). The intake port is opened and closed by an intake valve 16.

[0029] The exhaust manifold 50 is connected to an exhaust port 51 of the engine body 10 (cylinder head 11). An exhaust valve 17 opens and closes the exhaust port 51. The exhaust (combustion gas) collected in the exhaust manifold 50 passes through an exhaust passage (exhaust pipe) 52 and flows into the turbine 36 of the variable nozzle turbo 30.

[0030] An exhaust purification device 56 is provided in the exhaust passage 52 downstream of the turbine 36. The exhaust purification device 56 may be composed of, for example, an oxidation catalyst, a DPF (Diesel Particulate Filter), and a selective reduction catalyst. The selective reduction catalyst generates ammonia from urea water supplied from a urea addition valve (not shown), and uses the ammonia to reduce and purify nitrogen oxides (NOx) in the exhaust. A silencer (exhaust muffler) 58 is provided in the exhaust passage 52 downstream of the exhaust purification device 56, and the exhaust is silenced by the silencer 58 before being released into the atmosphere.

[0031] The engine 1 is provided with an EGR (Exhaust Gas Recirculation) device 60. The EGR device 60 includes an EGR cooler 61, an EGR valve 62, and an EGR passage 63. The EGR passage 63 connects the exhaust passage 52 upstream of the turbine 36 with the intake passage 22 downstream of the intake throttle valve 25. The EGR cooler 61 and the EGR valve 62 are provided in the EGR passage 63. The EGR cooler 61 cools the EGR gas (exhaust). The EGR valve 62 is an adjustment valve that adjusts the amount of exhaust gas recirculated (EGR amount) flowing through the EGR passage 63 in response to a control signal from the control device 200. The greater the opening of the EGR valve 62, the greater the EGR amount (the amount of exhaust gas recirculated to the intake passage 22).

[0032] The variable nozzle turbo 30 includes a compressor 32, a turbine 36, and a variable nozzle mechanism 40. A compressor wheel 34 is housed in the housing of the compressor 32, and a turbine wheel 38 is housed in the housing of the turbine 36. The compressor wheel 34 and the turbine wheel 38 are connected by a connecting shaft 39. The compressor wheel 34 is driven to rotate by the exhaust energy of the exhaust gas supplied to the turbine wheel 38, and compresses and supercharges the intake air.

[0033] The variable nozzle mechanism 40 is composed of multiple variable nozzles (nozzle vanes) arranged in the exhaust inlet section around the rotation axis of the turbine wheel 38, and a link mechanism that rotates the variable nozzles around the rotation axis. When the link mechanism is driven by an actuator 42, the gap (exhaust passage cross-sectional area) between adjacent nozzles changes, narrowing or widening the exhaust flow path in the exhaust inlet section of the turbine wheel 38. This makes it possible to change the flow velocity of the exhaust that drives the turbine wheel 38. In this embodiment, the gap (exhaust passage cross-sectional area) between adjacent variable nozzles is referred to as the VN opening (variable nozzle opening). Also, in this embodiment, the actuator 42 is a DC motor.

[0034] The control device 200 controls the operation of the engine 1. The control device 200 includes a CPU (Central Processing Unit) 201 that performs various processes, memory 202 including a ROM (Read Only Memory) that stores programs and data and a RAM (Random Access Memory) that stores CPU processing results, and input / output ports (not shown) for exchanging information with the outside. Various sensors are connected to the input port, and devices to be controlled (for example, fuel injection valve 15, intake throttle valve 25, actuator 42, EGR valve 62, etc.) are connected to the output port.

[0035] The control device 200 executes predetermined calculation processing based on signals from various sensors and devices, and maps and programs stored in the memory 202. Then, the control device 200 controls the fuel injection valve 15, the intake throttle valve 25, the actuator 42, the EGR valve 62, etc. based on the results of the calculation processing.

[0036] In this embodiment, the various sensors include an engine rotation speed sensor 101, an air flow meter 102, an accelerator opening sensor 103, a boost pressure sensor 104, an exhaust pressure sensor 105, a VN opening sensor 106, a vehicle speed sensor 107, and a shift position sensor 108.

[0037] The engine rotation speed sensor 101 detects the rotation speed of the crankshaft, which is the output shaft of the engine 1, as the engine rotation speed NE. The air flow meter 102 detects the intake air amount Ga. The accelerator opening sensor 103 detects the accelerator opening AP, which is the amount of depression of the accelerator pedal. The boost pressure sensor 104 detects the boost pressure Pim by the variable nozzle turbo 30.

[0038] The exhaust pressure sensor 105 detects the exhaust pressure P4, which is the pressure in the exhaust passage upstream of the turbine 36. The VN opening sensor 106 detects the opening degree (VN opening degree) Tv of the variable nozzle. The vehicle speed sensor 107 detects the vehicle speed SPD of the vehicle V in which the engine 1 is mounted.

[0039] The shift position sensor 108 detects the shift position of the transmission 3. In this embodiment, the transmission 3 is an automatic transmission, and the shift positions can be selected from P (parking), R (reverse), N (neutral), D (drive), and S (sports). When a shift lever (not shown) is operated to select the S position, a gear change is performed in the S mode. In the S mode, a shift range from 1st to 6th gear ranges can be selected by operating a shift switch (not shown). In the S position, acceleration and engine braking are greater than in the D position. Also, the smaller the number of the shift range (1st to 6th gear range), the greater the acceleration and engine braking.

[0040] The control device 200 executes fuel injection control. For example, the control device 200 calculates a fuel injection amount Qf from a fuel injection amount map stored in the memory 202 using the accelerator opening AP and the engine rotation speed NE. The control device 200 also calculates a fuel injection timing from a fuel injection timing map stored in the memory 202 using the accelerator opening AP and the engine rotation speed NE. Then, the control device 200 controls the fuel injection valve 15 so that the amount of fuel equivalent to the fuel injection amount Qf is injected at the calculated fuel injection timing.

[0041] The control device 200 executes EGR control. For example, the control device 200 calculates a target EGR rate based on the fuel injection amount Qf, the intake air amount Ga, and the engine rotation speed NE. The control device 200 calculates the amount of gas in the combustion chamber 14 based on the boost pressure Pim, and determines an actual EGR rate from the calculated gas amount and the intake air amount Ga. Then, the control device 200 controls the opening of the EGR valve 62 so that the actual EGR rate becomes the target EGR rate. Note that during auxiliary brake control of the VN opening control, which will be described later, the EGR rate is set to 0, and the EGR valve 62 is controlled to be fully closed.

[0042] The control device 200 executes VN opening control to control the VN opening of the variable nozzle turbo 30. The VN opening control includes normal control to control the VN opening to a target VN opening To based on the operating state of the engine 1, and auxiliary brake control to control the VN opening to a target VN opening Tdo during deceleration when the vehicle V decelerates.

[0043] 2 is a flowchart of VN opening control executed by control device 200 in this embodiment. This flowchart is repeatedly executed at predetermined intervals when the ignition switch of engine 1 is ON. In step (hereinafter, step will be abbreviated as "S") 10, it is determined whether or not S mode has been selected. If the shift position detected by shift position sensor 108 is the S position and S mode has been selected, a positive determination is made and the process proceeds to S11. If S mode has not been selected, a negative determination is made and the process proceeds to S20.

[0044] In S11, it is determined whether the accelerator pedal is released, the accelerator opening AP is 0, and the vehicle speed SPD is equal to or greater than a predetermined value α. The predetermined value α is a threshold value for detecting whether the vehicle is moving (not stopped). If there is a request to decelerate the vehicle, the accelerator opening AP is 0 and the vehicle speed SPD is equal to or greater than the predetermined value α, so a positive determination is made and the process proceeds to S30. If there is no request to decelerate the vehicle, a negative determination is made and the process proceeds to S20.

[0045] In S20, the normal control described in FIG. 3 is executed, and in S30, the auxiliary brake control described in FIG. 5 is executed, after which the current routine ends.

[0046] 3 is a flowchart of normal control. In S22, a target boost pressure Pt is calculated based on the engine speed NE and the fuel injection amount Qf (or the accelerator pedal position AP). In the following S24, a target VN opening To of the VN opening is determined based on the target boost pressure Pt. For example, the target VN opening To may be calculated from the target boost pressure Pt and the boost pressure Pim. Note that instead of S22 and S24, the target VN opening To may be calculated based on the engine speed NE and the fuel injection amount Qf (or the accelerator pedal position AP), and the target VN opening To may be corrected based on the difference between the target boost pressure Pt and the boost pressure Pim.

[0047] In S26, the actuator 42 is controlled using the first speed vc1, the second speed vc2, the speed switching deviation dc1, and the like so that the VN opening Tv detected by the VN opening sensor 106 becomes the target VN opening To.

[0048] FIG. 4 is a diagram illustrating an overview of speed control of VN opening Tv. In FIG. 4, the vertical axis represents VN opening Tv, and the horizontal axis represents time. In FIG. 4, the dotted line indicates speed control under normal control. Under normal control, when controlling VN opening Tv toward the closing side (throttling side), if the deviation between VN opening Tv and target VN opening To is greater than speed switching deviation dc1, VN opening Tv is controlled to decrease (close) at a first speed vc1. Furthermore, if the deviation between VN opening Tv and target VN opening To is equal to or smaller than speed switching deviation dc1, VN opening Tv is controlled to decrease at a second speed vc2. The first speed vc1 and the second speed vc2 represent the amount of change in VN opening Tv per unit time, and the first speed vc1 is set faster (larger) than the second speed vc2. The first speed vc1 and the second speed vc2 correspond to an example of the "normal closing speed" of the present disclosure.

[0049] The first speed vc1, the second speed vc2, and the speed switching deviation dc1 are set in advance through experiments or the like according to the operating state of the engine 1, and are stored in the memory 202 as a map using, for example, the engine rotation speed NE and the accelerator opening AP as parameters. In this embodiment, the first speed vc1, the second speed vc2, and the speed switching deviation dc1 are set so as to avoid interference between the VN opening control and the EGR control due to a decrease in the VN opening Tv, an increase in the exhaust pressure, and fluctuations in the EGR amount. The first speed vc1 and the second speed vc2 are set so that the actual EGR rate can be controlled to the target EGR rate by controlling the opening of the EGR valve 62, even if the VN opening Tv is controlled to the closing side by the first speed vc1 and the second speed vc2.

[0050] In S26, when controlling VN opening Tv to the opening side, the opening speed (opening velocity) vo1 is used to control VN opening Tv. When controlling VN opening Tv to the opening side, a speed switching deviation may be provided to set the opening speed in two stages, as in the case of closing. The first speed vc1, second speed vc2, and speed switching deviation dc1 correspond to examples of the "first speed," "second speed," and "first predetermined value" in this disclosure. The target VN opening To corresponds to an example of the "target opening" in this disclosure.

[0051] 5 is a flowchart of auxiliary brake control. In S32, the target deceleration Gd of the vehicle V is calculated. The control device 200 calculates the target deceleration Gd based on the vehicle speed SPD and the shift range (1st to 6th range). For example, the target deceleration Gd may be calculated so that it increases as the shift range value decreases.

[0052] In the next step S34, a target VN opening degree Tdo during deceleration is calculated based on the target deceleration Gd. For example, a target exhaust pressure P4tag necessary to achieve the target deceleration Gd may be calculated based on the engine rotation speed NE and the intake air amount Ga, and the target VN opening degree Tdo during deceleration may be calculated based on the difference between the target exhaust pressure P4tag and the exhaust pressure P4. Alternatively, the target VN opening degree Tdo during deceleration that can achieve the target deceleration Gd may be calculated from a map using the engine rotation speed NE and the intake air amount Ga as parameters. In this embodiment, when the auxiliary brake control is executed, the EGR rate is set to 0, and the EGR valve 62 is controlled to be fully closed.

[0053] In S36, the actuator 42 is controlled using the third speed vc3, the fourth speed vc4, the speed switching deviation dc2, etc. so that the VN opening Tv detected by the VN opening sensor 106 becomes the target VN opening Tdo during deceleration.

[0054] Referring to Fig. 4, the solid line indicates speed control in auxiliary brake control. In auxiliary brake control, when VN opening Tv is controlled to close (throttle) the valve, if the deviation between VN opening Tv and the target VN opening Tdo during deceleration is greater than speed switching deviation dc2, VN opening Tv is controlled to decrease (close) at a third speed vc3. Furthermore, if the deviation between VN opening Tv and the target VN opening Tdo during deceleration is equal to or less than speed switching deviation dc2, VN opening Tv is controlled to decrease at a fourth speed vc4. The third speed vc3 and the fourth speed vc4 are amounts of change in VN opening Tv per unit time, and the third speed vc3 is set faster (larger) than the fourth speed vc4. The third speed vc3 and the fourth speed vc4 correspond to examples of the "closing speed during deceleration" of the present disclosure.

[0055] The third speed vc3, the fourth speed vc4, and the speed switching deviation dc2 are set in advance through experiments or the like according to the operating state of the engine 1, and are stored in the memory 202 as a map with the engine rotation speed NE and the intake air amount Ga as parameters, for example. In this embodiment, the third speed vc3, the fourth speed vc4, and the speed switching deviation dc2 are set so that the expansion ratio of the turbine 36 of the variable nozzle turbo 30 is equal to or less than a predetermined value. To achieve the target deceleration Gd, the deceleration target VN opening Tdo is set smaller than the target VN opening To (toward the throttle side). If the variable nozzle is suddenly closed to a region where the VN opening Tv is small, the expansion ratio of the turbine 36 may become excessive, which may damage the turbine 36. In this embodiment, the third speed vc3, the fourth speed vc4, and the speed switching deviation dc2 are set so that the expansion ratio is equal to or less than a predetermined value, thereby preventing the expansion ratio from becoming excessive.

[0056] In Fig. 4, the third speed vc3 is set smaller (slower) than the first speed vc1. At the start of auxiliary brake control, the VN opening Tv is closed more slowly than at the start of normal control. Therefore, even if the target VN opening Tdo during deceleration is smaller than the target VN opening To, the expansion ratio in the turbine 36 is prevented from becoming excessive. Note that the third speed vc3 may be any speed as long as it is equal to or lower than the first speed vc1.

[0057] In S36, when controlling VN opening Tv to the opening side, the opening speed (opening speed) vo3 is used to control VN opening Tv. When controlling VN opening Tv to the opening side, a speed switching deviation may be provided to set the opening speed in two stages, as in the case of closing. The third speed vc3, the fourth speed vc4, and the speed switching deviation dc2 correspond to examples of the "third speed," "fourth speed," and "second predetermined value" in this disclosure. The target VN opening during deceleration Tdo corresponds to an example of the "target opening during deceleration" in this disclosure.

[0058] According to this embodiment, the control device 200 executes normal control (FIG. 3) that controls the variable nozzle opening (VN opening Tv) to a target VN opening To based on the operating state of the engine 1. During normal control, the control device 200 controls the VN opening Tv using a normal closing speed (first speed vc1, second speed vc2). During deceleration of the vehicle V, the control device 200 executes auxiliary brake control (FIG. 5) that controls the VN opening Tv to a deceleration target VN opening Tdo. During auxiliary brake control, the control device 200 controls the VN opening Tv using a deceleration closing speed (third speed vc3, fourth speed vc4). As a result, during normal control, the VN opening Tv can be controlled using a normal closing speed that takes into account the output and emissions of the engine 1. Furthermore, during auxiliary brake control, the VN opening Tv can be controlled using a deceleration closing speed that takes into account the expansion ratio of the turbine 36. Therefore, the closing speed of the variable nozzle (the closing speed of the VN opening Tv) during normal control and auxiliary brake control can be optimized.

[0059] According to this embodiment, the third speed vc3 and the fourth speed vc4 (closing speed during deceleration) are set so that the expansion ratio in the turbine 36 is equal to or less than a predetermined value. This makes it possible to ensure the deceleration of the vehicle V while suppressing damage to the turbine 36 during auxiliary brake control (when the exhaust brake is activated).

[0060] According to this embodiment, the first speed vc1 and the second speed vc2 (normally closed speed) are set to avoid interference between the VN opening control and the EGR control, thereby maintaining optimal emissions.

[0061] In this embodiment, the first speed vc1 is set to be faster than the second speed vc2, and the third speed vc3 is set to be faster than the fourth speed vc4. Therefore, the VN opening Tv can be quickly controlled to the target VN opening To or the deceleration target VN opening Tdo while suppressing overshoot in the VN opening control.

[0062] In the above embodiment, when the S position is selected (when a positive determination is made in S10 in FIG. 2), auxiliary brake control (exhaust brake) is executed if the conditions are met. However, an exhaust brake switch operated by the driver may be provided, and when the exhaust brake switch is turned ON, auxiliary brake control may be executed if the conditions are met. Also, the transmission 3 may be a manual transmission.

[0063] In the above embodiment, when the auxiliary brake control is executed, the EGR rate is set to 0, and the EGR valve 62 is controlled to be fully closed. However, when the auxiliary brake control is executed, the EGR valve 62 may be fixed to a predetermined opening.

[0064] The control device 200 may include multiple CPUs, which cooperate to execute various controls. Alternatively, the control devices may be configured to execute various controls using multiple ECUs (Electronic Control Units) connected via a CAN (Controller Area Network). In this case, the multiple ECUs connected via the CAN correspond to the control devices.

[0065] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0066] 1 engine, 3 transmission, 5 differential gear, 7 drive wheels, 10 engine body, 11 cylinder head, 12 cylinder, 13 piston, 14 combustion chamber, 15 fuel injection valve, 16 intake valve, 17 exhaust valve, 20 air cleaner, 22 intake passage, 25 intake throttle valve, 26 intercooler, 28 intake manifold, 30 variable nozzle turbo, 32 compressor, 34 compressor wheel, 36 turbine, 38 turbine wheel, 39 connecting shaft, 40 variable nozzle mechanism, 42 actuator, 50 exhaust manifold, 51 exhaust port, 52 exhaust passage, 56 exhaust purification device, 58 silencer, 60 EGR device, 61 EGR cooler, 62 EGR valve, 63 EGR passage, 80 exhaust valve, 101 engine rotation speed sensor, 102 air flow meter, 103 Accelerator opening sensor, 104 boost pressure sensor, 105 exhaust pressure sensor, 107 vehicle speed sensor, 108 shift position sensor, 200 control device, 201 CPU, 202 memory, V vehicle.

Claims

1. A vehicle equipped with an internal combustion engine having a variable nozzle turbo in an exhaust passage, a control device for controlling an opening degree of the variable nozzle of the variable nozzle turbo; The control device normal control that controls the opening degree of the variable nozzle to a target opening degree based on an operating state of the internal combustion engine; and executing auxiliary brake control to control the opening of the variable nozzle to a target opening during deceleration when the vehicle is decelerating. During the normal control, the opening degree of the variable nozzle is controlled based on a normal closing speed; During the auxiliary brake control, the opening degree of the variable nozzle is controlled based on the closing speed during deceleration.

2. 2. The vehicle according to claim 1, wherein the closing speed during deceleration is set so that an expansion ratio in a turbine of the variable nozzle turbo is equal to or less than a predetermined value.

3. the internal combustion engine includes an EGR passage that recirculates exhaust gas upstream of the turbine to an intake passage, and an EGR valve provided in the EGR passage, The control device Further, an EGR control is performed to control an opening degree of the EGR valve based on an operating state of the internal combustion engine. The vehicle according to claim 2 , wherein the normal closing speed is set to prevent the normal control from interfering with the EGR control.

4. the normal closing speed includes a first speed and a second speed slower than the first speed, and the second speed is a closing speed when a deviation between an opening degree of the variable nozzle and the target opening degree is equal to or less than a first predetermined value; the closing speed during deceleration includes a third speed and a fourth speed slower than the third speed, and the fourth speed is a closing speed when a deviation between an opening degree of the variable nozzle and the target opening degree during deceleration is equal to or less than a second predetermined value; The vehicle according to claim 1 , wherein the third speed is set to be equal to or lower than the first speed.

5. The control device The vehicle according to claim 4, wherein the target opening during deceleration is set based on a target deceleration of the vehicle.

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