Engine supercharger

Abstract

The present invention provides a supercharging device that improves durability by suppressing valve opening and closing while ensuring starting performance during cold starts. [Solution] In an engine 1 equipped with a first supercharger 2 that provides supercharging in the low-speed range and a second supercharger 3 that provides supercharging in the high-speed range, the exhaust passage 11 is equipped with a first bypass passage 22 that bypasses the turbine 2b of the first supercharger 2, a second bypass passage 23 that bypasses the turbine 3b of the second supercharger 3, a TBV 25 that opens and closes the first bypass passage 22, a WG 26 that opens and closes the second bypass passage 23, a valve control unit that controls the opening of the TBV 25 and WG 26 between fully closed and fully open, and an outside air temperature sensor 34 that acquires the outside air temperature. The valve control unit fully closes the TBV 25 and fully opens the WG 26 when the engine is started at room temperature, and opens the TBV 25 to 26% and fully opens the second valve 26 when the engine is started in cold conditions.

Description

【Technical Field】 【0001】 The present invention relates to a supercharging device for an engine having a plurality of superchargers. 【Background Art】 【0002】 Patent Document 1 discloses an engine for driving a vehicle equipped with a supercharger (turbocharger). Many engines equipped with a supercharger include a bypass passage for flowing exhaust gas bypassing the turbine, and a wastegate valve for opening and closing the bypass passage. 【0003】 Patent Document 1 further discloses a technique for controlling the opening degree of the wastegate valve according to the required acceleration or the like at the time of engine startup. 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 Japanese Patent No. 2020-172166 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 In recent years, engines equipped with a plurality of superchargers having different operating characteristics have become known. For example, an engine is provided with a supercharger for the low-speed range of an engine having a small turbine and a supercharger for the high-speed range of an engine having a large turbine, and each turbine is provided with a valve for controlling the flow rate of exhaust gas supplied thereto, and the opening degree of each valve is controlled based on the operating state of the engine. 【0006】 In engines equipped with multiple superchargers, where exhaust gas supply to the turbine is controlled by valve opening, the valves that control the exhaust flow rate to the low-speed superchargers operate frequently, especially during engine startup. This can lead to wear and tear on the moving parts of these valves over time. Furthermore, setting the valve opening to a small degree during startup to reduce the amount of valve opening and closing increases exhaust resistance, resulting in reduced starting performance, especially during cold starts. 【0007】 The present invention has been made in view of these problems, and its objective is to provide a supercharging device that improves durability by suppressing the amount of valve opening and closing while ensuring starting performance during cold starts in an engine equipped with multiple superchargers and valves that control the exhaust flow rate to each turbine. [Means for solving the problem] 【0008】 To achieve the above objective, the engine supercharging system according to the present invention comprises: a first supercharger that supercharges the engine in the low-speed range; a second supercharger that supercharges the engine in the high-speed range; a first bypass passage that bypasses the turbine of the first supercharger in the exhaust passage of the engine; a second bypass passage that bypasses the turbine of the second supercharger in the exhaust passage; a first valve that opens and closes the first bypass passage; a second valve that opens and closes the second bypass passage; a control unit that controls the opening of the first valve and the second valve between fully closed and fully open; and an outside air temperature acquisition means for acquiring the outside air temperature. The control unit is characterized in that, when the engine is started, if the outside air temperature is above a predetermined temperature, it fully closes the first valve and fully opens the second valve; and if the outside air temperature is below the predetermined temperature, it opens the first valve to an opening less than fully open and fully opens the second valve. [Effects of the Invention] 【0009】 According to the engine supercharging system of the present invention, when starting the engine, if the ambient temperature is above a predetermined temperature, the first valve is fully closed and the second valve is fully open, thereby greatly increasing the supercharging effect of the first supercharger. Furthermore, during cold starts when the ambient temperature is below the predetermined temperature, the first valve is opened to a smaller opening than fully open and the second valve is fully open, thereby suppressing pressure loss in the exhaust passage and ensuring starting performance, while also suppressing the valve movement of the first valve and improving the durability of the first valve. [Brief explanation of the drawing] 【0010】 [Figure 1] This is a diagram showing the configuration of the intake and exhaust system of an engine according to an embodiment of the present invention. [Figure 2] This is a diagram showing the configuration of the control system for each valve in the intake and exhaust system in this embodiment. [Figure 3] This graph shows an example of the control range for the opening degree of each valve in the intake and exhaust system. [Figure 4] This map shows examples of TBV and WG opening settings based on ambient temperature and engine operating conditions. [Figure 5] This graph shows actual measurement examples of the changes in engine rotational speed at TBV openings of 100% and 26% during engine startup. [Modes for carrying out the invention] 【0011】 Embodiments of the present invention will be described below with reference to the drawings. 【0012】 Figure 1 is a diagram showing the configuration of the intake and exhaust system of engine 1 according to an embodiment of the present invention. Figure 2 is a diagram showing the configuration of the control system for each valve of the intake and exhaust system in this embodiment. 【0013】 The engine 1 according to this embodiment is, for example, a diesel engine and is used as a power source for driving vehicles such as hybrid electric vehicles (HEVs), such as plug-in hybrid electric vehicles (PHEVs) that can be charged or supplied with external power. 【0014】 The engine 1 drives the generator 50 to generate electricity, and the electricity output from the generator 50 is configured to charge the in-vehicle battery 51 (in-vehicle rechargeable battery). The vehicle also includes an electric motor 52 that can be driven by the electricity supplied from the in-vehicle battery 51 to rotate the wheels. 【0015】 The engine 1 includes a two-stage turbocharger 5 having a first supercharger 2 which is a turbocharger for low-speed range supercharging and a second supercharger 3 which is a turbocharger for high-speed range supercharging. 【0016】 The first supercharger 2 is smaller than the second supercharger 3 and is designed to be suitable for supercharging in the low-speed range of the engine 1. The second supercharger 3 is designed to be suitable for supercharging in the medium-high speed range of the engine 1. 【0017】 In the intake passage 7 of the engine 1, in order from the upstream side of the intake air toward the engine 1, there are provided a compressor 3a of the second supercharger 3, a compressor 2a of the first supercharger 2, an intercooler 8 for cooling the intake air, and a throttle valve 9 for controlling the intake air flow rate. 【0018】 In the exhaust passage 11 of the engine 1, in order from the engine 1 toward the downstream side of the exhaust, there are provided a turbine 2b of the first supercharger 2, a turbine 3b of the second supercharger 3, and an exhaust purification unit 12. 【0019】 An EGR passage 15 is provided to connect the exhaust passage 11 on the downstream side of the exhaust purification unit 12 and the intake passage 7 on the upstream side of the compressor 3a of the second supercharger 3. In the EGR passage 15, in order from the exhaust passage 11 side, there are provided an EGR cooler 16 for cooling the exhaust passing through the EGR passage 15 and an EGR valve 17 for controlling the flow rate of the exhaust passing through the EGR passage 15. [[ID=​The exhaust passage 11 is provided with a first bypass passage 22 that bypasses the turbine 2b of the first supercharger 2 and a second bypass passage 23 that bypasses the turbine 3b of the second supercharger 3. The first bypass passage 22 is provided with a turbine bypass valve (hereinafter referred to as TBV) 25 (first valve) that opens and closes the first bypass passage 22. The second bypass passage 23 is provided with a wastegate valve (hereinafter referred to as WG) 26 (second valve) that opens and closes the second bypass passage 23. 【0021】 The intake passage 7 is provided with a third bypass passage 20 that bypasses the compressor 2a of the first supercharger 2. The third bypass passage 20 is provided with a compressor bypass valve (hereinafter referred to as CBV) 21 that opens and closes the third bypass passage 20. 【0022】 The first supercharger 2 is provided with a variable nozzle (VNT) 28 that controls the flow velocity of the exhaust gas flowing into the turbine 2b by reducing the exhaust gas flow area to the turbine 2b of the first supercharger 2. 【0023】 The opening degrees of the CBV 21, TBV 25, WG 26, and VNT 28 can be controlled to any value between fully closed and fully open. Also, the TBV 25 has a larger valve movement amount from fully closed to fully open, that is, the movement distance of the valve body which is the movable part, than the WG 26. [[ID=...]] 【0024】 As shown in FIG. 2, the CBV 21, TBV 25, WG 26, and VNT 28 are respectively driven by valve actuators 21a, 25a, 26a, and 28a. Each of the valve actuators 21a, 25a, 26a, and 28a is operationally controlled by a valve control unit 31 provided in the engine control unit 30. 【0025】 The engine control unit 30, which includes the valve control unit 31, is equipped with input / output devices, storage devices (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), etc. The valve control unit 31 controls the opening degree of CBV21, TBV25, WG26, and VNT28 based on the engine rotational speed Ne and engine torque Toe. The engine rotational speed Ne can be input from, for example, an engine rotational speed sensor 32 provided on the output shaft of the engine 1. The engine torque Toe can be input from, for example, an engine torque calculation unit 33 provided in the engine control unit 30, which calculates a value based on the accelerator operation amount, etc. 【0026】 Figure 3 is a graph showing an example of the opening degree control range for each valve 21, 25, 26, and 28 of the intake and exhaust system. Figure 4 is a map showing example opening degree settings for TBV25 and WG26 based on ambient temperature and engine operating conditions. Figure 5 is a graph comparing the changes in engine rotational speed at TBV opening degrees of 100% and 26% during engine startup. 【0027】 As shown in Figure 3, for example, the valve control unit 31 closes TBV25 and CBV21 when the engine rotational speed Ne is less than a predetermined value Ne1, and opens TBV25 and CBV21 when the engine rotational speed Ne is less than a predetermined value Ne1. The predetermined value Ne1 is, for example, 2000 rpm. 【0028】 As a result, in the low-speed range where the engine speed Ne is less than a predetermined value Ne1, the entire intake air passes through the compressor 2a of the first supercharger 2, and the entire exhaust air passes through the turbine 2b of the first supercharger 2, thereby operating the first supercharger 2. Furthermore, as shown in the area of ​​the downward-sloping diagonal line in Figure 3, in the low-speed range where the engine speed Ne is less than a predetermined value Ne1, the VNT 28 is controlled to open based on the engine speed Ne and engine torque Toe. For example, when the engine speed Ne is greater than or equal to the predetermined value Ne1, the VNT 28 is fully open, but in the low-speed range where the engine speed Ne is less than a predetermined value Ne1, the opening of the VNT 28 is reduced as the engine speed Ne decreases, increasing the flow velocity of the exhaust passing through the turbine 2b of the first supercharger 2. This improves the supercharging effect of the first supercharger 2 and allows for a rapid increase in engine torque in the low-speed range, such as during engine startup. 【0029】 Furthermore, the valve control unit 31 controls the opening and closing of the VNT28 based not only on the engine rotational speed Ne but also on the engine torque Toe, and also takes into account the boost pressure and exhaust pressure conditions of the engine 1 when controlling the opening and closing of the VNT28. 【0030】 In the high-speed range where the engine rotational speed Ne is greater than or equal to a predetermined value Ne1, the exhaust can bypass the turbine 2b of the first supercharger 2, and the intake can bypass the compressor 2a of the first supercharger 2, thereby suppressing intake and exhaust resistance. Furthermore, as shown in the downward-sloping shaded area in Figure 3, WG26 is controlled to open in the high-speed range where the engine rotational speed Ne is greater than or equal to a predetermined value Ne1, and at high engine torque. For example, WG26 is normally closed, but by opening WG26 in the region where the engine torque Toe is greater than or equal to an allowable value based on the engine rotational speed Ne (the downward-sloping shaded area in Figure 3), the turbine 3b of the second supercharger 3 is bypassed, thereby suppressing an increase in exhaust resistance. 【0031】 Furthermore, the valve control unit 31 controls the opening degree of TBV25 and WG26 based on the ambient temperature Temp when the engine is started. The ambient temperature Temp can be input, for example, from an ambient temperature sensor 34 (ambient temperature acquisition means) provided in the vehicle. 【0032】 As shown in Figure 4, during ambient temperature startup when the ambient temperature Temp is above a predetermined temperature Temp1 (e.g., 25°C), the valve control unit 31 fully closes the TBV25 (opening 0%) and fully opens the WG26 (opening 100%) before engine startup and during cranking. During startup determination and after startup, both the TBV25 and WG26 are fully closed (opening 0%). 【0033】 Note that "before engine start" refers to the moment immediately before engine start and before cranking begins. The start determination period is the period from ignition to complete combustion, when engine 1's operation stabilizes, and is used to determine whether or not engine 1 has started. 【0034】 The valve control unit 31 sets the opening degree of the TBV25 to a predetermined opening degree Ra1 (e.g., 26%) before engine start and during cranking when the ambient temperature Temp is below a predetermined temperature Temp1 during cold start. The opening degrees of the TBV25 and WG26 after the start determination when the ambient temperature Temp is below the predetermined temperature Temp1 during cold start are set to the same values ​​as during normal temperature start. 【0035】 The predetermined opening angle Ra1 should be set to the smallest possible value while ensuring starting performance during cold starts, after conducting tests and other procedures. 【0036】 For example, as shown in Figure 5, when the ambient temperature Temp is below a predetermined temperature Temp1, and the predetermined opening Ra1 is set to 26%, the change in engine speed Ne is almost the same as when the TBV25 is set to fully open (100%), and thus, it has been found through testing that starting performance can be ensured. In such an engine 1, it is desirable to set the predetermined opening Ra1 to 26%, and by setting the predetermined opening Ra1 within the range of at least 26% to 50%, starting performance can be ensured while suppressing the amount of valve movement of the TBV25 during engine starting to less than half compared to when it is set to fully open, thereby significantly improving durability. 【0037】 Furthermore, the valve control unit 31 may change the predetermined opening degree Ra1 of the TBV 26 before engine starting and during cranking based on the ambient temperature Temp when the ambient temperature Temp is below a predetermined temperature Temp1 during cold starting. Specifically, the predetermined opening degree Ra1 of the TBV 26 should be increased as the ambient temperature Temp decreases. This allows the starting performance of the engine 1 to decrease as the ambient temperature Temp decreases, by setting the predetermined opening degree Ra1 to a larger value, thereby suppressing the valve movement amount of the BV 25 while ensuring starting performance. When changing the predetermined opening degree Ra1 based on the ambient temperature Temp, it is preferable to set the predetermined opening degree Ra1 within the range of 26% to 50%. 【0038】 Furthermore, the valve control unit 31 may completely close the TBV 25 when the ambient temperature Temp is below a predetermined temperature Temp1 during cold startup, and the state of charge (SOC) of the onboard battery 51 is lower than a predetermined value SOC1. The state of charge (SOC) of the onboard battery 51 can be input, for example, from a battery monitoring unit 53 that monitors the charging and discharging of the onboard battery 51. The predetermined value SOC1 should be set to a lower limit that ensures sufficient output from the drive motor when the vehicle starts immediately after a cold start. 【0039】 As described above, the engine 1 includes a first supercharger 2 that provides supercharging in the low-speed range and a second supercharger 3 that provides supercharging in the high-speed range. In the exhaust passage 11, it includes a first bypass passage 22 that bypasses the turbine 2b of the first supercharger 2, a second bypass passage 23 that bypasses the turbine 3b of the second supercharger 3, a TBV 25 that opens and closes the first bypass passage 22, and a WG 26 that opens and closes the second bypass passage 23. 【0040】 Furthermore, the valve control unit 31 of this embodiment controls the valve to fully close the TBV 25 and fully open the WG 26 when the engine starts if the outside air temperature Temp is above a predetermined temperature Temp1, and to open the TBV 25 to a predetermined opening Ra1 (for example, 26%) less than fully open and fully open the WG 26 when the outside air temperature Temp is below the predetermined temperature Temp1. 【0041】 As a result, when starting at ambient temperature with an outside air temperature Temp above a predetermined temperature Temp1, the TBV25 is completely closed, allowing the entire amount of exhaust gas to pass through the turbine 2b of the first supercharger 2, thereby enabling a rapid and significant supercharging effect to be obtained by the first supercharger 2. 【0042】 Furthermore, during cold starts when the ambient temperature Temp is below a predetermined temperature Temp1, opening the TBV25 can reduce the pressure loss in the exhaust passage 11, thereby improving starting performance. Also, by opening the TBV25 to, for example, 26% rather than fully during cold starts, it is possible to reduce the amount of valve movement of the TBV25 during starting, i.e., the distance the valve body of the TBV25 moves, while ensuring starting performance. This reduces wear on the movable parts of the TBV25 and improves durability. 【0043】 The TBV25 opens and closes in a partial state, for example, when the engine rotational speed Ne is around a predetermined value Ne1, while the WG26 only opens at high speed and high load. Therefore, the TBV25 opens and closes much more frequently than the WG26. Consequently, by suppressing wear on the TBV25 and improving its durability as described above, the overall durability of the engine, including the TBV25 and WG26, can be improved. 【0044】 Furthermore, since the TBV25 has a larger valve travel distance from fully closed to fully open compared to the WG26, setting the TBV25 opening to a predetermined opening Ra1 (=26%) instead of fully closed during cold startup significantly reduces the travel distance of the TBV25 valve body during startup, effectively suppressing wear on the movable parts of the TBV25. 【0045】 In this embodiment, engine 1 sets the opening degree of the TBV25 to a predetermined opening degree Ra1 (=26%) during cold starting (before starting and during cranking). This ensures starting performance that is not significantly different from when the TBV25 is fully open (100%) during cold starting, while setting the TBV25 opening degree as close as possible to closed (0%), thereby greatly improving the durability of the TBV25. The opening degree of the TBV25 during cold starting (before starting and during cranking) may vary depending on the specifications of the engine to which it is applied, so it should be set appropriately after confirmation through experiments, etc. At least setting the opening degree of the TBV25 during cold starting to less than fully open can suppress the movement distance of the TBV25 valve body during starting compared to setting it to fully open, thereby improving the durability of the TBV25. 【0046】 Furthermore, by changing the opening degree Ra (predetermined opening degree Ra1) of the TBV25 during cold starting based on the ambient temperature Temp, it is possible to set the opening degree of the TBV25 as low as possible while ensuring starting performance in accordance with the ambient temperature Temp. This suppresses changes in the opening degree of the TBV25 during cold starting and further reduces wear on the movable parts. 【0047】 Furthermore, as described above, when the engine 1 of this embodiment is mounted on a hybrid vehicle having an electric motor 52 that can mechanically drive the wheels using power output from an on-board battery 51, if the state of charge (SOC) of the on-board battery 51 is lower than a predetermined value SOC1 during cold start-up when the ambient temperature Temp is below a predetermined temperature Temp1, closing the TBV 25 completely regardless of the ambient temperature Temp will allow the engine output to be quickly increased by closing the TBV 25, even if the output of the drive motor cannot be secured when the charge level of the on-board battery 51 is low, thereby ensuring the acceleration of the vehicle from engine start-up. 【0048】 It should be noted that the present invention is not limited to the embodiments described above. For example, various settings such as a predetermined temperature Temp1 and a predetermined opening degree Ra1 may be confirmed by testing or other means and set as appropriate. 【0049】 Furthermore, the present invention can also be applied to engines in engine-driven vehicles that do not have an electric motor for propulsion. The present invention can be applied to engines as a power source for propulsion in various vehicles, and can be widely applied to engines for various applications. [Explanation of Symbols] 【0050】 1 Engine 2. First supercharger 3. Second Supercharger 7 Intake passage 11 Exhaust passage 22 First Bypass Passage 23 Second Bypass Passage 25 TBV (1st valve) 26 WG (2nd valve) 30 Engine control unit 31 Valve control unit (control unit) 34. Outdoor temperature sensor (means for acquiring outdoor temperature) 51. Onboard battery (onboard rechargeable battery) 52 Electric motor

Claims

[Claim 1] The first supercharger provides boost at low engine speeds, A second supercharger that provides boost to the engine in the high-speed range, In the exhaust passage of the engine, there is a first bypass passage that bypasses the turbine of the first supercharger, The exhaust passage includes a second bypass passage that bypasses the turbine of the second supercharger, A first valve that opens and closes the first bypass passage, A second valve that opens and closes the second bypass passage, A control unit that controls the opening degree of the first valve and the second valve between fully closed and fully open, It includes an outside air temperature acquisition means for acquiring the outside air temperature, The control unit, when starting the engine, fully closes the first valve and fully opens the second valve if the ambient temperature is above a predetermined temperature, and opens the first valve to less than fully open and fully opens the second valve if the ambient temperature is below the predetermined temperature. An engine supercharging system characterized by the following features. [Claim 2] The first valve has a larger valve travel distance from fully closed to fully open compared to the second valve. The supercharging device for the engine according to feature 1. [Claim 3] The control unit sets the opening of the first valve to a value within the range of 26% to 50% when the engine is started when the ambient temperature is below the predetermined temperature. A supercharging device for an engine according to claim 1 or 2. [Claim 4] The control unit changes the opening degree of the first valve based on the ambient temperature when the engine is started at an ambient temperature below the predetermined temperature. A supercharging device for an engine according to claim 1 or 2. [Claim 5] The vehicle is equipped with an on-board rechargeable battery and an electric motor for propulsion that is driven by power supplied from the on-board rechargeable battery. The control unit, when starting the engine at an ambient temperature below the predetermined temperature, will completely close the first valve regardless of the ambient temperature if the charge level of the onboard battery is lower than a predetermined value. The supercharging device for the engine according to feature 1.

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