JP6947118B2 - Supercharger - Google Patents

Description

The present invention relates to the control of a variable nozzle mechanism of a turbocharger.

Conventionally, it is known that an engine is provided with a supercharger such as a turbocharger that supercharges the air sucked into the engine by using the exhaust energy from the exhaust manifold. The turbocharger is provided with a variable nozzle mechanism that uses a vane to narrow the exhaust flow path to increase the flow velocity of the exhaust gas supplied to the turbine wheel, or to widen the exhaust flow path to reduce the flow velocity. In some cases.

Regarding a supercharger provided with a variable nozzle mechanism, for example, Japanese Patent Application Laid-Open No. 2009-275620 (Patent Document 1) states that the opening degree of the variable nozzle is controlled by PID in order to set the actual supercharging pressure to the target supercharging pressure. The technology to adjust is disclosed.

Japanese Unexamined Patent Publication No. 2009-275620

In the turbocharger provided with the above-mentioned variable nozzle mechanism, the vane opening degree of the variable nozzle mechanism is controlled so that the pressure of the exhaust manifold does not exceed the pressure upper limit value in order to protect the engine. The vane opening degree is set using, for example, the engine speed and the fuel injection amount on the premise that the exhaust flow rate is in a stable state with little fluctuation. However, when the operating state of the engine is in a transient state, the expected exhaust flow rate may not be reached even if the engine speed and the fuel injection amount are the same. Therefore, even when the vane opening is set so that the pressure of the exhaust manifold reaches the pressure upper limit value using the engine speed and the fuel injection amount, when the actual exhaust flow rate is smaller than expected, the exhaust is exhausted. The pressure of the manifold can be more than the upper limit of the pressure. As described above, the vane opening degree set depending on the flow rate of the exhaust gas may be a vane opening degree having a large margin with respect to the vane opening degree that actually causes the pressure of the exhaust manifold to reach the pressure upper limit value. As a result, it may not be possible to appropriately set the vane opening degree at which the function of the turbocharger can be fully exerted.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a supercharger having a variable nozzle mechanism in which a vane opening degree is appropriately set according to an exhaust flow rate. To provide.

A supercharger according to a certain aspect of the present invention has a turbine operated by exhaust gas discharged from the engine, a compressor supercharging air taken into the engine by the operation of the turbine, and a plurality of nozzle vanes. A flow velocity variable device that changes the flow velocity of the exhaust gas that operates the turbine by rotating the nozzle vane to change the vane opening degree that indicates the size of the gap between the nozzle vanes and the adjacent nozzle vanes, and a control device that controls the flow velocity variable device. Be prepared. The control device uses the first effective opening area indicating the product of the sum of the opening areas in the gap between the adjacent nozzle vanes and the first coefficient indicating the ease of flow of exhaust in the flow velocity variable device, and the exhaust flow rate from the engine. Set the lower limit of the vane opening. The control device sets the lower limit of the vane opening smaller as the exhaust flow rate decreases.

In this way, the lower limit of the vane opening according to the first effective opening area and the exhaust flow rate is set, so that the vane opening according to the request while keeping the pressure of the exhaust manifold lower than the pressure upper limit. Can be set appropriately. Therefore, the function of the supercharger can be fully exerted.

Preferably, the control device calculates the basic value of the vane opening using the engine speed and the fuel injection amount in the engine, and responds to the difference between the target supercharging pressure of the turbocharger and the actual supercharging pressure. Calculate the feedback amount of the vane opening. The control device sets the command value of the vane opening degree based on the comparison result of the sum of the basic value and the feedback amount and the lower limit value of the vane opening degree.

By doing so, the lower limit of the vane opening is appropriately set, so that the pressure of the exhaust manifold is prevented from exceeding the upper limit of the pressure, and for example, the actual supercharging pressure is quickly reached to the target supercharging pressure. Since the amount of feedback can be set larger so as to rise, the function of the supercharger can be quickly exerted.

More preferably, the engine includes a connecting passage that connects the intake passage and the exhaust passage on the upstream side of the turbine without passing through the cylinder of the engine, and a regulating valve that adjusts the flow rate of the exhaust gas flowing through the connecting passage. An exhaust gas recirculation device is provided. The control device uses the second effective opening area indicating the product of the opening area of the regulating valve and the second coefficient indicating the ease of flow of exhaust in the regulating valve, the pressure of the intake passage, and the exhaust flow rate as the first effective. Calculate the opening area.

In this way, in an engine provided with an exhaust gas recirculation device, the lower limit of the vane opening can be set by using the first effective opening area and the exhaust flow rate even when the opening of the adjusting valve is transient. .. Therefore, it is possible to appropriately set the vane opening degree according to the demand while lowering the pressure of the exhaust manifold below the pressure upper limit value.

According to the present invention, in a supercharger having a variable nozzle mechanism, it is possible to provide a supercharger that appropriately sets a vane opening degree according to an exhaust flow rate.

It is a figure which shows the schematic structure of the engine provided with the supercharger which concerns on this embodiment. It is a figure which shows an example of the structure of the variable nozzle mechanism. It is a flowchart which shows the control process executed by a control device. It is a figure for demonstrating the effective opening area between adjacent vanes in a variable nozzle mechanism. It is a figure which shows an example of the relationship between the effective opening area, the exhaust flow rate, and the lower limit value of a vane opening degree in a variable nozzle mechanism.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are designated by the same reference numerals. Their names and functions are the same. Therefore, detailed explanations about them are not repeated.

FIG. 1 is a diagram showing a schematic configuration of an engine 1 provided with a supercharger according to the present embodiment. In the present embodiment, the engine 1 will be described as, for example, a common rail type diesel engine as an example, but may be an engine of another type (for example, a gasoline engine or the like).

The engine 1 includes an engine body 10, an air cleaner 20, an intercooler 26, an intake manifold 28, a supercharger 30, an exhaust manifold 50, an exhaust treatment device 55, and an exhaust gas recirculation device (hereinafter, EGR (Exhaust)). A gas recirculation) device) 60, an engine rotation speed sensor 102, an air flow meter 104, a supercharging pressure sensor 106, and a control device 200 are provided.

The engine body 10 includes a cylinder 12 and an injector 16. The engine 1 may be an in-line engine or an engine having another cylinder layout (for example, V-type or horizontal type).

The injector 16 is a fuel injection device provided at the top of the cylinder 12 and connected to a common rail (not shown). The fuel stored in the fuel tank (not shown) is pressurized to a predetermined pressure by a supply pump (not shown) and supplied to the common rail. The fuel supplied to the common rail is injected from the injector 16 at a predetermined timing. The injector 16 supplies the fuel injection amount Qv commanded in response to the control signal from the control device 200 into the cylinder 12.

The air cleaner 20 removes foreign matter from the air sucked from the outside of the engine 1. One end of the first intake pipe 22 is connected to the air cleaner 20.

The other end of the first intake pipe 22 is connected to the intake inlet of the compressor 32 of the supercharger 30. One end of the second intake pipe 24 is connected to the intake outlet of the compressor 32. The compressor 32 supercharges the air flowing from the first intake pipe 22 and supplies it to the second intake pipe 24. The detailed operation of the compressor 32 will be described later.

One end of the intercooler 26 is connected to the other end of the second intake pipe 24. The intercooler 26 is an air-cooled or water-cooled heat exchanger that cools the air flowing through the second intake pipe 24.

One end of the third intake pipe 27 is connected to the other end of the intercooler 26. An intake manifold 28 is connected to the other end of the third intake pipe 27. The intake manifold 28 is connected to the intake port of the cylinder 12 of the engine body 10. A diesel throttle 25 is provided in the middle of the third intake pipe 27, on the intercooler 26 side of the branch point with the EGR 60 described later.

The exhaust manifold 50 is connected to the exhaust port of the cylinder 12 of the engine body 10. One end of the first exhaust pipe 52 is connected to the exhaust manifold 50. The other end of the first exhaust pipe 52 is connected to the exhaust inlet of the turbine 36 of the turbocharger 30. Therefore, the exhaust gas discharged from the exhaust port of each cylinder is supplied to the turbine 36 via the exhaust manifold 50 and the first exhaust pipe 52. The diesel throttle 25 adjusts the flow rate of intake air from the control device 200 according to a control signal.

One end of the second exhaust pipe 54 is connected to the exhaust outlet of the turbine 36. An exhaust treatment device 55 including an oxidation catalyst 56, a PM (Particulate Matter) removal filter 57, and an SCR catalyst 58, a muffler, and the like are connected to the other end of the second exhaust pipe 54. Therefore, the exhaust gas discharged from the exhaust outlet of the turbine 36 is discharged to the outside of the vehicle via the second exhaust pipe 54, the exhaust treatment device 55, the muffler, and the like.

The third intake pipe 27 and the exhaust manifold 50 are connected by the EGR device 60 without passing through the cylinder 12 of the engine body 10. The EGR device 60 includes an EGR valve 62 and an EGR passage 66. The EGR passage 66 connects the third intake pipe 27 and the exhaust manifold 50. The EGR valve 62 is provided in the middle of the EGR passage 66.

The EGR valve 62 is a regulating valve that adjusts the flow rate of the EGR gas flowing through the EGR passage 66 in response to a control signal from the control device 200. The exhaust gas in the exhaust manifold 50 is returned to the intake side as EGR gas via the EGR device 60, so that the combustion temperature in the cylinder 12 is lowered and the amount of NOx produced is reduced.

The turbocharger 30 includes a compressor 32, a turbine 36, a variable nozzle mechanism 40, and an actuator 44. The compressor wheel 34 is housed in the housing of the compressor 32, and the 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 42 and rotate integrally. Therefore, the compressor wheel 34 is rotationally driven by the exhaust energy of the exhaust gas supplied to the turbine wheel 38.

The variable nozzle mechanism 40 is arranged in an exhaust inflow portion around the rotation axis of the turbine wheel 38, and includes a plurality of vanes (see FIG. 2) that guide the exhaust gas supplied from the first exhaust pipe 52 to the turbine wheel 38. Includes a link mechanism that changes the gap between adjacent vanes (the size of this gap is referred to as the vane opening degree in the following description) by rotating each of the plurality of vanes. The actuator 44 changes the vane opening degree of the variable nozzle mechanism 40 by operating the link mechanism in response to an operation instruction from the control device 200.

By changing the vane opening degree of the variable nozzle mechanism 40, the flow path of the exhaust gas in the exhaust inflow portion to the turbine wheel 38 is narrowed or widened. Thereby, the flow velocity of the exhaust gas blown to the turbine wheel 38 can be changed.

FIG. 2 is a diagram showing an example of the configuration of the variable nozzle mechanism 40. FIG. 2A is a view of the variable nozzle mechanism 40 viewed from the left in FIG. FIG. 2B is a view of the variable nozzle mechanism 40 viewed from the right in FIG. The configuration of the variable nozzle mechanism 40 may be any structure as long as it changes the flow velocity of the exhaust gas supplied to the turbine wheel 38 by narrowing the flow path of the exhaust gas from the first exhaust pipe 52 to the turbine wheel 38, and in particular, FIG. It is not limited to the configuration shown in.

As shown in FIGS. 2A and 2B, the variable nozzle mechanism 40 includes a plurality of nozzle vanes 67 arranged in an exhaust inflow portion on the outer periphery of the turbine wheel 38, and a plurality of shafts 68 as rotation centers. Includes a nozzle plate 69 that oscillates each of the nozzle vanes 67, and a unisonring 71 that rotates the shaft 68 using an arm 70 fixed to the end of each shaft 68. The unisonring 71 is rotated by the operation of the actuator 44 via the link mechanism 72, and the arm 72b fixed to the end of the rotation shaft 72a of the link mechanism 72 is swung by the actuator 44. By doing so, the unisonring 71 that engages with the arm 72b can be rotated.

For example, as shown in FIG. 2A, when the arm 72b is swung by the link mechanism 72 in the direction indicated by the arrow, the unisonring 71 is moved in the direction indicated by the arrow, that is, counterclockwise in FIG. 2A. Rotate, and in FIG. 2B, it rotates clockwise. Further, due to the rotation of the unisonring 71, each axis 68 is rotated in the direction indicated by the arrow, that is, counterclockwise in FIG. 2A and clockwise in FIG. 2B. Therefore, the opening degree of the nozzle vane 67 is controlled to the closed side (so that the gap between two adjacent nozzle vanes becomes narrower). Further, when the arm 72b is swung in the direction opposite to the arrow, the opening degree of the nozzle vane 67 is controlled to the opening side (so that the gap between two adjacent nozzle vanes is widened).

Returning to FIG. 1, the operation of the engine 1 is controlled by the control device 200. The control device 200 includes a CPU (Central Processing Unit) that performs various processes, a memory that includes a ROM (Read Only Memory) that stores programs and data, a RAM (Random Access Memory) that stores the processing results of the CPU, and the like. Includes input / output ports (neither shown) for exchanging information with the outside. The above-mentioned sensors (for example, engine speed sensor 102, air flow meter 104, boost pressure sensor 106, etc.) are connected to the input port. Devices to be controlled (for example, injector 16, actuator 44, EGR valve 62, etc.) are connected to the output port.

The control device 200 controls various devices so that the engine 1 is in a desired operating state based on the signals from each sensor and the device, and the map and the program stored in the memory. Note that various controls are not limited to software processing, but can also be processed by dedicated hardware (electronic circuits). Further, the control device 200 has a built-in timer circuit (not shown) for measuring the time.

The engine speed sensor 102 detects the speed of the crankshaft, which is the output shaft of the engine 1, as the engine speed NE. The engine speed sensor 102 transmits a signal indicating the detected engine speed NE to the control device 200.

The air flow meter 104 detects the flow rate (intake air amount) Qin of fresh air introduced into the first intake pipe 22. The air flow meter 104 transmits a signal indicating the detected intake air amount Qin to the control device 200.

The boost pressure sensor 106 detects the pressure in the intake manifold 28 as the boost pressure. The boost pressure sensor 106 transmits a signal indicating the detected boost pressure to the control device 200.

In the engine 1 having the above configuration, the control device 200 controls the variable nozzle mechanism 40 based on the state of the engine 1. More specifically, the control device 200 sets the basic value of the vane opening degree of the variable nozzle mechanism 40 based on the state of the engine 1 (for example, the engine speed NE and the fuel injection amount Qv).

The control device 200 increases the flow velocity of the exhaust gas supplied to the turbine wheel 38, for example, when the engine speed NE is in the low speed region and the load is in the low load region (that is,). Set the basic value (so that the vane opening becomes smaller).

On the other hand, in the control device 200, for example, when the engine speed NE is in the high speed region and the load is in the high load region, the flow velocity of the exhaust gas supplied to the turbine wheel 38 is slowed down ( That is, the basic value is set so that the vane opening becomes large).

Further, the control device 200 calculates the feedback amount of the vane opening degree by using the difference between the target boost pressure and the actual boost pressure. The control device 200 sets a target boost pressure using, for example, the engine speed NE, the intake air amount Qin, the fuel injection amount Qv, and the like. The control device 200 acquires the actual boost pressure by using the boost pressure sensor 106.

The control device 200 generates a control signal for controlling the actuator 44 using a value obtained by adding the feedback amount to the set basic value as a command value of the vane opening degree, and transmits the control signal to the actuator 44. The actuator 44 of the variable nozzle mechanism 40 changes the vane opening degree based on the received control signal. In this way, by appropriately adjusting the vane opening degree of the variable nozzle mechanism 40 based on the state of the engine 1, the supercharging pressure of the supercharger 30 can be adjusted to the optimum supercharging pressure.

In the turbocharger 30 having such a variable nozzle mechanism 40, the vane opening degree of the variable nozzle mechanism 40 is controlled so that the pressure of the exhaust manifold 50 does not exceed the pressure upper limit value in order to protect the engine. That is, when the lower limit of the vane opening is set to the value obtained by adding the feedback amount to the above-mentioned basic value and the value obtained by adding the feedback amount to the basic value is smaller than the lower limit value, the lower limit value is set to the vane opening. The actuator 44 of the variable nozzle mechanism 40 is controlled as a command value. The lower limit of the vane opening degree is set using, for example, the engine speed NE and the fuel injection amount Qv on the premise that the exhaust flow rate is in a stable state with little fluctuation.

However, when the operating state of the engine 1 is a transient state, the expected exhaust flow rate may not be reached even if the engine speed NE and the fuel injection amount Qv are the same. Therefore, even when the vane opening is set so that the pressure of the exhaust manifold 50 reaches the pressure upper limit value using the engine rotation speed NE and the fuel injection amount Qv, the actual pressure of the exhaust manifold 50 is the pressure upper limit. It can be in a state where there is more room than the value. As described above, the vane opening degree set depending on the exhaust flow rate may be a vane opening degree having a large margin with respect to the vane opening degree that actually causes the pressure of the exhaust manifold 50 to reach the pressure upper limit value. As a result, it may not be possible to appropriately set the vane opening degree at which the function of the turbocharger can be fully exerted.

Therefore, in the present embodiment, it is assumed that the control device 200 operates as follows. That is, the control device 200 has a first effective opening area μ indicating the product of _{the total opening area A 1} in the gap between the adjacent nozzle vanes 67 and _{the first coefficient μ 1} indicating the ease of exhaust flow in the variable nozzle mechanism 40. ₁ A ₁ and the exhaust flow rate m from the engine 1 are used to set the lower limit value Va of the vane opening. The control device 200 sets the lower limit value Va of the vane opening degree smaller as the exhaust flow rate m decreases.

In this way, the lower limit value Va of the vane opening according to the first effective opening area μ ₁ A ₁ and the exhaust flow rate m is set, so that the pressure of the exhaust manifold 50 is made lower than the pressure upper limit value while being lowered. The vane opening can be appropriately set according to the request. Therefore, the function of the supercharger can be fully exerted.

Hereinafter, the control process executed by the control device 200 according to the present embodiment will be described with reference to FIG. FIG. 3 is a flowchart showing a control process executed by the control device 200. The process shown in this flowchart is called and executed from the main routine (not shown) at predetermined control cycles. In the following description, it is assumed that the EGR valve 62 is fully closed or opened to such an extent that it does not affect the calculation of the lower limit value Va of the vane opening, which will be described later.

In step 100 (hereinafter, step is referred to as S) 100, the control device 200 calculates the basic value Vb of the vane opening degree. As described above, the control device 200 calculates the basic value Vb of the vane opening degree by using the engine speed NE and the fuel injection amount Qv. The control device 200 calculates the basic value Vb of the vane opening degree by using, for example, a map showing the relationship between the engine speed NE, the fuel injection amount Qv, and the basic value Vb of the vane opening degree. A map showing the relationship between the engine speed NE, the fuel injection amount Qv, and the basic value Vb of the vane opening degree is adapted by, for example, an experiment, and is stored in the memory of the control device 200 in advance.

The control device 200 acquires the engine speed NE from the engine speed sensor 102. The control device 200 acquires the fuel injection amount Qv using the command value for the injector 16.

In S102, the control device 200 calculates the feedback amount Vc of the vane opening degree. As described above, the control device 200 calculates the feedback amount Vc from the difference between the target boost pressure and the actual boost pressure. The control device 200 calculates the feedback amount Vc using a map showing the relationship between the difference between the target boost pressure and the actual boost pressure and the feedback amount Vc. A map showing the relationship between the difference between the target boost pressure and the actual boost pressure and the feedback amount Vc is adapted by, for example, an experiment, and is stored in the memory of the control device 200 in advance. Since the method of obtaining the target boost pressure and the actual boost pressure is as described above, the detailed description thereof will not be repeated.

In S104, the control device 200 calculates the sum Vb + Vc of the basic value Vb of the vane opening degree and the feedback amount Vc. In S106, the control device 200 calculates _{the effective opening area μ 1} A _{1 of the variable nozzle mechanism 40.}

FIG. 4 is a diagram for explaining an _{effective opening area μ 1} A ₁ between adjacent vanes in the variable nozzle mechanism 40. As shown in FIG. 4, a square opening having a straight line as one side shown in the solid line of FIG. 4 is formed in the gap between the nozzle vane 67a and the adjacent nozzle vane 67b. Similar openings are formed between each vane of the variable nozzle mechanism 40. The opening area is indicated by the sum of the areas of the openings between the vanes. Effective opening area of the variable nozzle mechanism 40 is indicated by the product of the total sum A ₁ of the area of the opening between the vanes, the coefficient mu ₁ showing the ease of flow of exhaust gas in the variable nozzle mechanism 40. This effective opening area μ ₁ A ₁ can be estimated using the following equation (1).

Here, "a" and "b" indicate predetermined coefficients. "R" indicates the gas constant. “M” indicates the exhaust flow rate from the exhaust manifold 50. The exhaust flow rate m is estimated using, for example, the amount of gas in the cylinder 12 calculated using the intake air amount Qin and the fuel injection amount Qv.

Further, “T4” indicates the exhaust temperature in the exhaust manifold 50. The exhaust temperature T4 is, for example, the engine speed NE, the intake air temperature, the water temperature, the combustion parameters such as the fuel injection amount Qv and the injection timing, the intake air amount Qin, the temperature of the intake manifold 28, and the inside of the cylinder 12. Estimated using the amount of gas. The intake air temperature, the water temperature, and the temperature of the intake intake manifold 28 are detected by using, for example, a sensor (not shown).

“P6” indicates the pressure of the exhaust gas flowing out from the supercharger 30 to the second exhaust pipe 54. The exhaust pressure P6 is estimated using, for example, the atmospheric pressure, the front-rear differential pressure of the PM removal filter 57, and the pressure loss value of the SCR 58. The atmospheric pressure and the front-rear differential pressure of the PM removal filter 57 are detected by using, for example, a sensor (not shown).

“P4” indicates the pressure of the exhaust gas in the exhaust manifold 50. The exhaust pressure P4 includes, for example, the exhaust temperature T4, the intake air amount Qin, the fuel injection amount Qv, the combustion parameters such as the fuel injection timing, the exhaust pressure P6, the state of the EGR device 60, and the vane opening degree. The assumed pressure upper limit value is set using the state of the variable nozzle mechanism 40.

For the exhaust temperature T4 and the exhaust pressures P4 and P6, predetermined calculation models are constructed experimentally or designly in advance, and the estimated values and the upper limit values are calculated by inputting the respective parameters described above.

In the above equation (1), for example, the law of energy conservation, the law of momentum conservation, etc. are obtained from the opening degree of the adjacent nozzle vanes 67 of the variable nozzle mechanism 40, the temperature, pressure, and exhaust flow rate upstream and downstream of the nozzle vanes 67. Derived from the relational expression derived using. Since such a relational expression is derived using a well-known technique, its detailed description will not be given.

In S108, the control device 200 calculates the lower limit value Va of the vane opening degree. Specifically, the control device 200 calculates the lower limit value Va of the vane opening degree by using the exhaust flow rate m and the effective opening area μ ₁ A _{1 of the variable nozzle mechanism 40.} The control device 200 calculates, for example, the lower limit value Va of the vane opening degree by using a map showing the relationship between the exhaust flow rate m, the effective opening area μ ₁ A _{1, and the lower limit value Va of the vane opening degree.} A map showing the relationship between the exhaust flow rate m, the effective opening area μ _{1 A 1,} and the lower limit value Va of the vane opening degree is adapted by, for example, an experiment, and is stored in the memory of the control device 200 in advance.

_{FIG. 5 is a diagram showing an example of the relationship between the effective opening area μ 1} A ₁ in the variable nozzle mechanism 40, the exhaust flow rate m, and the lower limit value Va of the vane opening. Each of the thick solid line LN1, the one-dot chain line LN2, the two-dot chain line LN3, the thin line LN4, and the broken line LN5 in FIG. 5 _{shows the relationship between the effective opening area μ 1} A ₁ that can be taken for each exhaust flow rate and the lower limit value Va of the vane opening. .. Of the thick solid lines LN1 to the broken line LN5, the exhaust flow rate on the thick solid line LN1 is the smallest, and the exhaust flow rate on the broken line LN5 is the largest. It is assumed that the exhaust flow rate increases in the order of the thick solid line LN1, the one-dot chain line LN2, the two-dot chain line LN3, the thin line LN4, and the broken line LN5.

Further, among the thick solid lines LN1 to the broken line LN5, the broken line LN5 indicates the relationship between the effective opening area and the lower limit value Va of the vane opening when the exhaust flow rate is F (0), and the thin line LN4 has the exhaust flow rate F. _{The relationship between the effective opening area μ 1} A ₁ and the lower limit value Va of the vane opening when the flow rate is half that of (0) (F (0) × 0.5) is shown.

For example, when the exhaust flow rate m is F (0) and the effective opening area μ ₁ A ₁ is S (0) (see point A in the figure), V (0) is the lower limit of the vane opening. It will be set as the value Va. On the other hand, it is assumed that the exhaust flow rate m is half the flow rate of F (0). For convenience of explanation, _{the parameters other than the effective opening area μ 1} A ₁ are assumed to be the same. In this case, when the exhaust flow rate m becomes half the flow rate of F (0), the effective opening area μ ₁ A ₁ also becomes half the value as is clear from the equation (1) (see point B in the figure), so V V (1) on the closing side of (0) is set as the lower limit value Va of the vane opening. In this way, the lower limit value Va of the vane opening degree is set smaller as the exhaust flow rate decreases.

In S110, the control device 200 determines whether or not the value of the basic value Vb + the feedback amount Vc is equal to or greater than the lower limit value Va of the vane opening degree. When it is determined that the value of the basic value Vb + the feedback amount Vc is equal to or greater than the lower limit value Va of the vane opening degree (YES in S110), the process is transferred to S112.

In S112, the control device 200 sets the value of the basic value Vb + the feedback amount Vc as the command value of the vane opening degree, and executes the opening degree control of the variable nozzle mechanism 40 based on the set command value.

When it is determined that the value of the basic value Vb of the vane opening degree + the feedback amount Vc is smaller than the lower limit value Va of the vane opening degree (NO in S110), the process is transferred to S114.

In S114, the control device 200 sets the lower limit value Va of the vane opening degree as a command value of the vane opening degree, and executes the opening degree control of the variable nozzle mechanism 40 based on the set command value.

The operation of the control device 200 in the present embodiment based on the above structure and flowchart will be described.

When the engine 1 is in the operating state, the basic value Vb of the vane opening is calculated based on the engine speed NE and the fuel injection amount Qv (S100), and the difference between the target boost pressure and the actual boost pressure. The feedback amount Vc of the vane opening degree is calculated according to (S102), and the sum of the calculated basic value Vb of the vane opening degree and the feedback amount Vc is calculated (S104).

On the other hand, the exhaust flow rate m, the exhaust temperature T4, and the exhaust pressure P6 are estimated using a predetermined calculation model, and the effective opening area μ ₁ A _{1 corresponding to the upper limit value of the exhaust pressure P4 is calculated using the estimated values.} (S106). Then, the lower limit value Va of the vane opening degree is calculated using the exhaust flow rate m and the effective opening area μ ₁ A _{1 (S108).} When the sum of the basic value Vb of the vane opening and the feedback amount Vc is equal to or greater than the lower limit value Va of the vane opening (YES in S110), the sum of the basic value Vb of the vane opening and the feedback amount Vc is calculated. Opening control is executed as a command value of the vane opening degree (S112). On the other hand, when the sum of the basic value Vb of the vane opening and the feedback amount Vc is smaller than the lower limit value Va of the vane opening (NO in S110), the lower limit value Va of the vane opening is commanded for the vane opening. Opening control is executed as a value (S114).

As described above, according to the turbocharger 30 according to the present embodiment, _{the lower limit value Va of the vane opening according to the effective opening area μ 1} A ₁ and the exhaust flow rate m is set (particularly, the exhaust). Since the lower limit value Va of the vane opening is set smaller as the flow rate m decreases), the pressure P4 of the exhaust manifold 50 can be appropriately set to the required vane opening while being lower than the pressure upper limit value. can. Therefore, the function of the supercharger 30 can be fully exerted. Therefore, in a supercharger having a variable nozzle mechanism, it is possible to provide a supercharger that appropriately sets the vane opening degree according to the exhaust flow rate.

Further, by appropriately setting the lower limit value Va of the vane opening degree, the pressure of the exhaust manifold 50 is prevented from exceeding the upper limit value of the pressure, and the actual supercharging pressure is quickly increased to the target supercharging pressure, for example. Since the feedback amount can be set larger so as to be performed, the function of the supercharger 30 can be quickly exerted.

In particular, when the engine is transient (when the supercharger 30 is transient) such as when the vehicle is accelerating, the pressure of the exhaust manifold 50 is the upper limit of the pressure by adjusting the feedback amount which has a large effect on the vane opening during the transient. Since the vane opening can be closed until it is close to the vicinity, the boost pressure can be increased quickly. As a result, the amount of air taken into the engine 1 is rapidly increased, and the acceleration performance of the vehicle can be improved.

Hereinafter, a modified example will be described.
In the above-described embodiment, the case where the EGR valve 62 is fully closed or has an opening degree that does not affect the calculation of the vane limit opening degree has been described as an example, but a part of the exhaust gas is the EGR passage 66. _{The effective opening area μ 1} A ₁ in the variable nozzle mechanism 40 may be calculated in consideration of the case of distribution to the variable nozzle mechanism 40.

Specifically, the control device 200 _{may calculate the effective opening area μ 1} A ₁ using the following equation (2).

Here, "a", "b", "c" and "d" indicate predetermined coefficients. "R" indicates the gas constant. “M” indicates the exhaust flow rate from the exhaust manifold 50.

Further, "T4" indicates the exhaust temperature in the exhaust manifold 50. “P6” indicates the pressure of the exhaust gas flowing out from the supercharger 30 to the second exhaust pipe 54. “P4” indicates the pressure of the exhaust gas in the exhaust manifold 50. Since the method of estimating the exhaust flow rate m, the exhaust temperature T4, and the exhaust pressure P6 and the method of setting the upper limit value of the exhaust pressure P4 are as described above, the detailed description thereof will not be repeated.

“Pb” indicates the pressure of the intake air in the intake manifold 28. The intake pressure Pb is acquired by, for example, the boost pressure sensor 106. “Μ ₂ A ₂ ” indicates the effective opening area of the EGR valve 62. For example, the _{opening area A 2 calculated from the second coefficient μ 2} indicating the ease of flow in the EGR valve 62 and the opening degree of the EGR valve 62. Indicated by the product of.

The control device 200 calculates the _{effective opening area μ 2} A ₂ by using, for example, a map showing the relationship between the flow rate of EGR gas, the opening degree of the EGR valve 62, and μ ₂ A _2. The relationship between the flow rate of the EGR gas, the opening degree of the EGR valve 62, and the effective opening area μ ₂ A ₂ is adapted by, for example, an experiment or the like, and is stored in advance in the memory of the control device 200.

In this way, even in the engine 1 provided with the EGR 60 that returns a part of the exhaust gas to the intake passage, the lower limit value Va of the vane opening can be set by using _{the effective opening area μ 1} A _{1 and the exhaust flow rate m.} Can be done. Therefore, the pressure of the exhaust manifold 50 can be appropriately set to the vane opening degree according to the demand while being lower than the pressure upper limit value.

In the above equation (2), for example, in addition to the above equation (1), the law of energy conservation and the momentum are based on the opening degree of the EGR valve 62, the temperature, pressure and gas flow rate upstream and downstream of the EGR valve 62. It is derived from the relational expression derived by using the law of conservation. Since such a relational expression is derived using a well-known technique, its detailed description will not be given.

Further, in the above-described embodiment, the EGR device 60 has been described as being composed of the EGR valve 62 and the EGR passage 66, but is connected to the EGR passage 66 or in parallel with the EGR passage 66 and is connected to the EGR passage 66. An EGR cooler may be provided in a passage set so as to be branchable from 66.

Further, in the above-described embodiment, the exhaust temperature T4 and the exhaust pressures P4 and P6 are estimated based on the state of the engine 1 and the like. However, a temperature sensor is provided in the exhaust manifold 50 to directly detect the exhaust temperature T4. Alternatively, a pressure sensor may be provided in the exhaust manifold 50 to directly detect the exhaust pressure P4, or a pressure sensor may be provided in the second exhaust pipe 54 to directly detect the exhaust pressure P6.

The above-mentioned modification may be carried out in whole or in combination.
It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 engine, 10 engine body, 12 cylinders, 16 injectors, 20 air cleaners, 22, 24, 27 intake pipes, 25 diesel throttles, 26 intercoolers, 28 intake manifolds, 30 superchargers, 32 compressors, 34 compressor wheels, 36 turbines , 38 turbine wheel, 40 variable nozzle mechanism, 42 connecting shaft, 44 actuator, 50 exhaust manifold, 52, 54 exhaust pipe, 55 exhaust treatment device, 56 oxidation catalyst, 57 PM removal filter, 58 SCR catalyst, 60 EGR device, 62 EGR valve, 64 EGR cooler, 66 EGR passage, 67, 67a, 67b nozzle vane, 68 shaft, 69 nozzle plate, 70, 72b arm, 71 unison ring, 72 link mechanism, 72a rotation shaft, 102 engine rotation speed sensor, 104 airflow Meter, 106 boost pressure sensor, 200 controller.

Claims (3)

A turbine operated by the exhaust gas discharged from the engine and
A compressor that supercharges the air that is taken into the engine by the operation of the turbine, and
A flow velocity variable device having a plurality of nozzle vanes and rotating the plurality of nozzle vanes to change the flow velocity of the exhaust gas that operates the turbine by changing the vane opening degree indicating the size of the gap between the plurality of nozzle vanes. When,
A control device for controlling the flow velocity variable device is provided.
The control device is
The first effective opening area indicating the product of the total opening area in the gap between the adjacent nozzle vanes and the first coefficient indicating the ease of exhaust flow in the flow velocity variable device, and the exhaust flow rate from the engine are used. Set the lower limit of the vane opening,
A supercharger that sets the lower limit of the vane opening degree smaller as the exhaust flow rate decreases. The control device is
The basic value of the vane opening is calculated using the engine speed and the fuel injection amount in the engine, and the vane is calculated according to the difference between the target supercharging pressure and the actual supercharging pressure of the turbocharger. Calculate the amount of feedback of the opening,
The supercharger according to claim 1, wherein a command value of the vane opening degree is set based on a comparison result of the sum of the basic value and the feedback amount and the lower limit value of the vane opening degree. The engine includes a connection passage that connects an intake passage and an exhaust passage on the upstream side of the turbine without passing through the cylinder of the engine, and a regulating valve that adjusts the flow rate of exhaust gas flowing through the connection passage. Exhaust gas recirculation device with
The control device has a second effective opening area indicating the product of an opening area in the adjusting valve and a second coefficient indicating the ease of flow of exhaust in the adjusting valve, a pressure in the intake passage, and an exhaust flow rate. The supercharger according to claim 1 or 2, wherein the first effective opening area is calculated by using the turbocharger.

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