JP2020118107A - Purge system for electric vehicle mounted with power generating engine - Google Patents

Abstract

To provide a purge system for a type of an electric vehicle which does not directly transmit engine output to driving wheels.SOLUTION: A purge system comprises: a canister which absorbs vaporized fuel generated in a fuel tank; a purge passage which communicates a suction pipe connected to a power generating engine with the canister; and a step motor type control valve which is installed in the purge passage and controls a flow rate of purge gas.SELECTED DRAWING: Figure 1

Description

This specification discloses the technique regarding the purge system of the electric vehicle carrying the engine for electric power generation.

Patent Document 1 discloses a purge system in which vaporized fuel generated in a fuel tank is adsorbed by a canister, purge gas containing vaporized fuel is supplied to an intake pipe connected to the engine, and the vaporized fuel is burned in the engine. ing. The canister and the intake pipe are connected by a purge passage. In Patent Document 1, a VSV type control valve (purge VSV) that controls the flow rate by the duty ratio is provided on the purge passage. The VSV type control valve changes the duty ratio according to the driving state of the engine (driving state of the automobile), and changes the flow rate of the purge gas supplied to the intake pipe (engine).

JP, 2011-132839, A

As described above, in the purge system of Patent Document 1, the VSV type control valve is used to control the flow rate of the purge gas supplied to the intake pipe. The VSV type control valve can quickly change the opening degree (change the flow rate of purge gas). Therefore, when it is necessary to frequently change the driving state (rotational speed) of the engine in response to the acceleration and deceleration of the automobile, the VSV type control valve can change the flow rate of the purge gas quickly, and thus is a useful control valve. Is. That is, in a purge system used in an automobile in which the output of the engine is directly transmitted to the drive wheels, it makes sense to control the flow rate of the purge gas by using a VSV type control valve.

However, in recent years, automobiles (electric automobiles) of the type that do not directly transmit the output of the engine to the drive wheels have been developed. In this type of electric vehicle, the engine is used only for generating electricity to charge the battery. The drive wheels are driven by a motor connected to the battery. Therefore, in the case of this type of electric vehicle, it is not necessary to change the driving state (rotation speed) of the engine in accordance with the acceleration/deceleration of the electric vehicle. Therefore, in this type of electric vehicle, it is considered that there is a purge system more suitable than the purge system used in the type of vehicle that directly transfers the output of the engine to the drive wheels. However, at present, no purging system that considers this type of electric vehicle has been developed. The present specification aims to provide a purge system for use in an electric vehicle of the type that does not directly transfer the output of the engine to the drive wheels.

The first technology disclosed in the present specification is a purge system for an electric vehicle equipped with a power generation engine. The purge system is provided on the canister that adsorbs the evaporated fuel generated in the fuel tank, the purge passage that connects the intake pipe connected to the power generation engine and the canister, and the purge passage. And a step motor type control valve for controlling the flow rate of.

A second technique disclosed in the present specification is the purge system according to the first technique, in which a VSV type control valve for controlling a flow rate of a purge gas by a duty ratio is provided on a purge passage in parallel with a step motor type control valve. It may be provided.

A third technique disclosed in the present specification is the purge system of the second technique, wherein the flow rate of the purge gas is controlled by the VSV type control valve when the purge gas concentration is equal to or higher than a predetermined value, and the purge gas concentration is lower than the predetermined value. At this time, the flow rate of the purge gas may be controlled by the step motor type control valve.

A fourth technique disclosed in the present specification is the purge system according to any one of the first to third techniques, wherein the pressure in the intake pipe is set to -40 kPa or more and -15 kPa or less when detecting the first purge gas concentration. Adjust and open the step motor type control valve to supply purge gas to the intake pipe.Based on the opening of the step motor type control valve, the pressure in the intake pipe, the intake air amount of the intake pipe, and the air-fuel ratio value. The control for detecting the purge gas concentration may be performed.

A fifth technique disclosed in the present specification is the purge system according to any one of the first to fourth techniques, in which the pressure in the intake pipe is maintained at a pressure less than −40 kPa and the step motor control valve Control for specifying the valve opening position may be performed.

According to the first technique, the purge gas can be efficiently supplied to the power generation engine. Specifically, when driving the power generation engine in a high load range (a state in which a large amount of outside air is supplied to the power generation engine using a supercharger, etc.), sufficient purge gas is supplied to the power generation engine. Can be supplied. That is, the flow rate of the purge gas (hereinafter referred to as the purge flow rate) can be increased. In the power generation engine, it is not necessary to change the driving state of the power generation engine according to the driving state of the automobile. That is, the power generation engine can continue to drive the power generation engine in a constant state regardless of the acceleration/deceleration of the automobile. In this case, the efficiency (fuel consumption) of the power generation engine is good if it is continuously driven in the high load range. For example, when a flow control valve (VSV type control valve) used in a vehicle of a type in which a drive wheel is directly driven by an engine (the output of the engine is directly transmitted to the drive wheel) is applied to an electric vehicle having a power generation engine. The purge flow rate can be controlled in the light load range, but the purge flow rate cannot be controlled in the high load range (the barge gas flow rate is insufficient). A flow rate control valve (VSV type control valve) used in an automobile in which driving wheels are directly driven by an engine is designed so that flow rate control becomes good in a light load range. For example, a duty ratio of 100% (control Even if the valve is fully opened), the required amount of purge gas cannot be passed. The first technology is a purge system that succeeds in increasing the purge flow rate in an electric vehicle equipped with a power generation engine.

In this specification, a state in which the amount of air supplied to the power generation engine is large is referred to as a high load region, a state in which the amount of air is small is referred to as a light load region, and a medium load is present between the high load region and the light load region. Area. Specifically, when the intake pipe internal pressure exceeds -15 kPa (small negative pressure) corresponds to the high load range, and when the intake pipe internal pressure is -40 kPa or higher and -15 kPa or lower (negative pressure is medium), medium load. It corresponds to the region, and when the pressure in the intake pipe is less than -40 kPa (large negative pressure) corresponds to the light load region.

According to the second technique, in addition to being able to secure a large purge flow rate in the high load range, the purge flow rate can be accurately controlled when the engine is driven in the light load range during idling, for example.

According to the third technique, when the purge gas concentration is high and the flow rate variation greatly affects the air-fuel ratio, the power generation engine can be driven in the light load range and the purge flow rate can be controlled by the VSV control valve. On the other hand, when the purge gas concentration is low and the influence of the flow rate variation on the air-fuel ratio is small, the power generation engine can be driven in the high load range, and the purge flow rate can be controlled by the step motor type control valve. According to the third technology, it is possible to improve fuel efficiency of an electric vehicle equipped with a power generation engine while suppressing deviation of the air-fuel ratio from the target air-fuel ratio.

According to the fourth technique, the purge gas concentration can be detected (measured) while suppressing the influence on the driving state of the power generation engine. In the fourth technique, at the first time, that is, when the current purge gas concentration is unknown, in order to reduce the influence on the drive state of the power generation engine, the purge gas concentration is kept in the state where the engine is driven in the medium load range. To detect. According to the fourth technique, when the purge gas concentration is detected, the fuel in the air-fuel mixture supplied to the power generation engine becomes too rich (overrich), or the purge gas is not sufficiently supplied to the power generation engine. Can be suppressed.

According to the fifth technique, the step at which the step motor type control valve starts opening (the step of changing from the closed state to the open state) is specified in the light load region. In the step motor type control valve, the valve may not open (the purge gas does not flow) from the lower limit step to several steps. Therefore, it is necessary to actually open the step motor type control valve gradually (raise the step) to identify the valve opening start position. If the purge flow rate when the step motor type control valve changes from the closed state to the open state is small, it may not be possible to determine an accurate valve opening step. By performing the judgment of the valve opening step in the light load range, the purge flow rate passing through the step motor type control valve increases when the valve closing state changes to the valve opening state, and the valve opening step can be surely judged. it can.

1 is a schematic view of a fuel supply system including a purge system according to a first embodiment. The schematic diagram of the fuel supply system provided with the purge system of 2nd Example is shown. The schematic diagram of the fuel supply system provided with the purge system of 3rd Example is shown. The schematic diagram of the fuel supply system provided with the purge system of 4th Example is shown. The flowchart about the calibration process of a step motor type control valve is shown. The flowchart about the detection process of the purge gas concentration of the first time is shown. The flowchart about the switching process of a VSV type control valve and a step motor type control valve is shown.

(First Embodiment: Fuel Supply System with Purge System)
A fuel supply system 10 including a purge system 20 will be described with reference to FIG. 1. The fuel supply system 10 is mounted on an electric vehicle and has a main fuel supply path 12 for supplying the fuel stored in the fuel tank 14 to the engine 2 and a vaporized fuel generated in the fuel tank 14 as a purge gas. A purge system 20 for supplying the engine 2 is provided. The engine 2 is also used to drive a power generation motor mounted on an electric vehicle. That is, the fuel supply system 10 is used to supply fuel to a power generation engine of an electric vehicle.

(Main fuel supply route)
The main fuel supply path 12 is connected to the fuel pump unit 16 and the injector 4. The fuel pump unit 16 includes a fuel pump, a pressure regulator, a control circuit, and the like. The fuel pump unit 16 controls the fuel pump according to the signal supplied from the ECU 100. The fuel pump pressurizes and discharges the fuel in the fuel tank 14. The fuel discharged from the fuel pump is regulated by the pressure regulator and supplied from the fuel pump unit 16 to the main fuel supply path 12. The fuel passes through the main fuel supply path 12 and reaches the injector 4. The injector 4 has a valve (not shown) whose opening is controlled by the ECU 100. When the valve of the injector 4 is opened, the fuel in the main fuel supply passage 12 is supplied to the intake pipe 34 connected to the engine 2.

The intake pipe 34 is connected to the air cleaner 30. The air cleaner 30 includes a filter that removes foreign matter in the air flowing into the intake pipe 34. A throttle valve 32 is provided between the engine 2 and the air cleaner 30. When the throttle valve 32 opens, intake air is taken from the air cleaner 30 toward the engine 2. The throttle valve 32 is a butterfly valve. The ECU 100 adjusts the amount of air flowing into the engine 2 by adjusting the opening of the throttle valve 32 to change the opening area of the intake pipe 34. The throttle valve 32 is provided closer to the air cleaner 30 than the injector 4.

A supercharger 33 is arranged between the throttle valve 32 of the intake pipe 34 and the air cleaner 30. The supercharger 33 is a so-called turbocharger, and rotates the turbine by the gas exhausted from the engine 2 to the exhaust pipe 38, whereby the air in the intake pipe 34 is pressurized and supplied to the engine 2. The supercharger 33 is controlled by the ECU 100 to be driven when the rotation speed of the engine 2 exceeds a predetermined rotation speed (for example, 2000 rotations).

An air flow meter 39 is arranged between the air cleaner 30 of the intake pipe 34 and the supercharger 33. The air flow meter 39 is one of a hot wire type, a Karman vortex type, and a movable plate type. The air flow meter 39 detects the amount of air that passes through the air cleaner 30 and is introduced into the intake pipe 34 from the atmosphere.

A pressure sensor 56 is attached to the intake pipe 34 downstream of the throttle valve 32. Specifically, the pressure sensor 56 is attached between the throttle valve 32 and the engine 2. More specifically, the pressure sensor 56 is attached to an intake manifold (not shown) arranged between the throttle valve 32 and the engine 2. The intake pressure of the engine 2 (pressure in the intake path) can be detected by the pressure sensor 56.

The gas after being burned by the engine 2 passes through the exhaust pipe 38 and is discharged. An air-fuel ratio sensor 36 is arranged in the exhaust pipe 38. The air-fuel ratio sensor 36 detects the air-fuel ratio in the exhaust pipe 38. When the ECU 100 acquires the air-fuel ratio from the air-fuel ratio sensor 36, the ECU 100 compares the acquired air-fuel ratio with the set air-fuel ratio and calculates a correction coefficient for the air-fuel ratio. The ECU 100 adjusts the opening degree of the injector 4 and the amount of air supplied to the engine 2 based on the calculated correction coefficient.

(Purge system)
The purge system 20 adsorbs the evaporated fuel generated in the fuel tank 14 by the canister 19 and supplies it to the intake pipe 34 through the purge passage 24. The evaporated fuel adsorbed by the canister 19 is mixed with air and supplied to the intake pipe 34. A mixed gas of evaporated fuel and air is called a purge gas. The purge system 20 includes a canister 19, a purge passage 24, a step motor type control valve 40, an ejector 60, and a control unit 102 in the ECU 100.

The canister 19 includes an atmosphere port 19a, a purge port 19b, and a tank port 19c. Further, activated carbon is housed inside the canister 19. The atmosphere port 19a is connected to the atmosphere passage 17 and communicates with the atmosphere via the air filter 15. The purge port 19b is connected to the purge passage 24. The tank port 14 a is connected to the tank passage 18 and communicates with the upper end of the fuel tank 14.

The evaporated fuel generated in the fuel tank 14 flows into the canister 19 through the tank passage 18 and is adsorbed by the activated carbon. The evaporated fuel adsorbed on the activated carbon is mixed with the air flowing in from the atmosphere passage 17 and supplied as purge gas from the purge port 19b to the purge passage 24. The air filter 15 removes foreign matter contained in the air flowing into the canister 19 from the atmosphere passage 17.

The flow rate of the purge gas in the purge passage 24 is controlled by a step motor type control valve 40 provided on the purge passage 24, and the purge gas is supplied to the intake pipe 34. Specifically, when the step value of the step motor type control valve 40 is increased (when the opening is increased), the flow rate of the barge gas is increased, and when the step value is decreased (when the opening is decreased), the purge flow rate is decreased. The purge passage 24 branches into a first passage 26 and a second passage 25 downstream of the step motor type control valve 40. The first passage 26 is connected to the suction port of the ejector 60. A check valve 50 is arranged in the middle of the first passage 26 (between the step motor type control valve 40 and the ejector 60). The check valve 50 allows the gas in the first passage 26 to flow from the step motor type control valve 40 toward the ejector 60, and prohibits the gas from flowing from the ejector 60 toward the step motor type control valve 40. The second passage 25 is connected to the intake pipe 34 downstream of the throttle valve 32. A check valve 52 is arranged in the middle of the second passage 25 (between the step motor type control valve 40 and the intake pipe 34). The check valve 52 allows the gas in the second passage 25 to flow from the step motor type control valve 40 toward the intake pipe 34, and prohibits the gas from flowing from the intake pipe 34 toward the step motor type control valve 40. To do.

A supply passage 64 and a discharge passage 62 are connected to the ejector 60. The supply passage 64 connects the supply port of the ejector 60 and the intake pipe 34 downstream of the supercharger 33 (between the supercharger 33 and the throttle valve 32). The discharge passage 62 connects the discharge port of the ejector 60 and the intake pipe 34 upstream of the supercharger 33. When the supercharger 33 is driven, a pressure difference is generated between the upstream side and the downstream side of the supercharger 33 (the pressure at the downstream side becomes higher than that at the upstream side), and the gas flows between the supply port and the discharge port of the ejector 60. As a result, negative pressure is generated in the suction port of the ejector, and the purge gas is supplied to the intake pipe 34 through the first passage 26 and the discharge passage 62. On the other hand, when the supercharger 33 is not driven, no pressure difference is generated between the upstream side and the downstream side of the supercharger 33. Since no negative pressure is generated in the suction port of the ejector, the purge gas is not supplied to the intake pipe 34 through the first passage 26 and the discharge passage 62. Note that when the supercharger 33 is not driven, the inside of the intake pipe 34 downstream of the throttle valve 32 becomes negative pressure due to the control of the throttle valve 32. As a result, the purge gas is supplied to the intake pipe 34 through the second passage 25.

(Characteristics of purge system)
As described above, the flow rate of the purge gas in the purge passage 24 is controlled by the step motor type control valve 40. The opening degree (step angle) of the step motor type control valve 40 is controlled by the control unit 102. The step motor type control valve 40 has a smaller pressure loss than, for example, a VSV type control valve. Therefore, the step motor type control valve 40 is suitable for supplying a large amount of purge gas to the intake pipe 34. Further, the purge system 20 is used to supply purge gas to a power generation engine (engine 2) of an electric vehicle. Since the power generation engine of the electric vehicle does not directly drive the drive wheels, it is not necessary to change the driving state of the power generation engine according to the driving state of the electric vehicle. Therefore, the power generation engine is normally driven in a high load range (that is, the supercharger 33 is driven) in order to achieve high efficiency (high fuel efficiency). Since the purge system 20 controls the purge flow rate using the step motor type control valve 40 having a small pressure loss, it is necessary to supply a large amount of purge gas to the power generation engine (engine 2) that is often driven in the high load region. You can

(Second to Fourth Embodiments: Modifications of Fuel Supply System)
Modifications (fuel supply systems 210, 310, 410) of the fuel supply system 10 will be described with reference to FIGS. 2 to 4. Regarding the fuel supply systems 210, 310, 410, the same components as those of the fuel supply system 10 are denoted by the same reference numerals as those of the fuel supply system 10, and the description thereof may be omitted.

(Second embodiment)
The fuel supply system 210 shown in FIG. 2 is used to supply fuel to a power generation engine of an electric vehicle similarly to the fuel supply system 10, and includes a main fuel supply path 12 and a purge system 220. In the purge system 220, the bypass passage 23 is connected to the purge passage 24, and the VSV type control valve 42 is provided on the bypass passage 23. That is, the VSV type control valve 42 is arranged in parallel with the step motor type control valve 40. The purge system 220 switches the purge flow rate control between the VSV type control valve 42 and the step motor type control valve 40 according to the driving state of the engine 2. Specifically, when the engine 2 is driven in a light load range, such as when the vehicle is stopped (idling), the purge flow rate is controlled using the VSV type control valve 42. The opening (duty ratio) of the VSV type control valve 42 is controlled by the control unit 102. On the other hand, when the engine 2 is driven in the high load range, the purge flow rate is controlled using the step motor type control valve 40, and when the engine 2 is driven in the load range higher than the light load range, the step motor type control valve 40 is used. Control the purge flow rate. That is, the control unit 102 controls the purge flow rate using the VSV type control valve 42 when the detected value of the pressure sensor 56 is less than −40 kPa, and uses the step motor type control valve 40 to purge when the detected value is −40 kPa or more. Control the flow rate.

As described above, in the purge system 220, the VSV type control valve 42 is arranged in parallel with the step motor type control valve 40, and when the engine 2 is driven in the light load range, the purge flow rate is controlled by using the VSV type control valve 42. It is different from the purge system 20 in that it is controlled. When the engine 2 is driven in the light load region, the pressure inside the intake pipe 34 is low (negative pressure is large), and the differential pressure between the upstream and downstream of the control valves 40 and 42 is large. In general, the greater the differential pressure between the upstream side and the downstream side of the control valve, the greater the influence of the variation in the opening degree of the control valve on the purge flow rate. Further, since the VSV type control valve can control the flow rate with a high flow rate resolution by changing the duty ratio, the VSV type control valve has a better flow rate decomposition ability than the step motor type control valve. Since the purge system 220 controls the purge flow rate by using the VSV type control valve 42 in the light load region where the influence of the flow rate decomposition ability becomes large, the purge gas is supplied to the intake pipe 34 with high accuracy regardless of the driving condition of the engine 2. Can be supplied.

(Third embodiment)
The fuel supply system 310 shown in FIG. 3 is used for supplying fuel to a power generation engine of an electric vehicle similarly to the fuel supply systems 10 and 210, and includes a main fuel supply path 12 and a purge system 320. The fuel supply system 310 differs from the purge system 20 in that the intake pipe 34 is not provided with the supercharger 33 and the purge system 320 is not provided with an ejector. Since the purge system 320 does not include an ejector, the purge passage 24 is directly connected to the intake pipe 34. That is, the purge passage 24 does not branch into the first passage 26 and the second passage (see also FIG. 1). Like the purge system 20, the purge system 320 controls the purge flow rate using the step motor type control valve 40, so that a large amount of purge gas can be supplied to the power generation engine (engine 2).

(Fourth embodiment)
The fuel supply system 410 shown in FIG. 4 is used to supply fuel to the power generation engine of an electric vehicle similarly to the fuel supply systems 10, 210 and 310, and includes a main fuel supply path 12 and a purge system 420. .. The purge system 420 is different from the purge system 320 (see FIG. 3) in that the bypass passage 23 is connected to the purge passage 24, and the VSV type control valve 42 is provided on the bypass passage 23. different. In the purge system 420 as well, like the purge system 220, when the engine 2 is driven in the light load range, the VSV type control valve 42 is used to control the purge flow rate, and the engine 2 is operated in the load range higher than the light load range. When driving, the purge flow rate is controlled using the step motor type control valve 40.

(Purge system operation)
Next, the operation of the purging system 20, 220, 320, 420 will be described. When the engine 2 is being driven and the purge condition is satisfied, the control unit 102 controls (opens) the step motor type control valve 40 or the VSV type control valve 42 to execute the purge process of supplying the purge gas to the engine 2. To do. The purge condition is a condition that is satisfied when the purge process of supplying the purge gas to the engine 2 is to be executed. The condition is preset in the control unit 102 by the manufacturer based on the remaining amount of the stored battery that stores the electricity. The control unit 102 constantly monitors whether or not the purge condition is satisfied while the engine 2 is being driven. The control unit 102 controls the opening degrees of the control valves 40 and 42 based on the purge gas concentration and the measurement value of the air flow meter 39. In the purge systems 220 and 420, the control unit 102 determines whether to control the step motor type control valve 40 or the VSV type control valve 42 based on the detection value of the pressure sensor 56. When the control valves 40 and 42 are opened, the purge gas adsorbed by the canister 19 is introduced into the engine 2.

When the engine 2 is driven, the ECU 100 controls the throttle valve 32 and the injector 4 using the detection value of the air-fuel ratio sensor 36 to adjust the air-fuel ratio to the target air-fuel ratio (for example, the ideal air-fuel ratio). Specifically, when the air-fuel ratio deviates from the target air-fuel ratio, the correction amount of the air-fuel ratio is calculated, and the injector 4 is feedback-controlled based on the calculated correction amount so that the air-fuel ratio becomes the target air-fuel ratio. .. Further, during the purge process, the ECU 100 corrects the fuel injection amount of the injector 4 based on the purge flow rate and the purge gas concentration. The purge gas concentration is specified by utilizing the phenomenon that the air-fuel ratio deviates from the target air-fuel ratio when the purge gas is supplied to the engine 2. The air-fuel ratio is detected by the air-fuel ratio sensor 36. For example, when the purge gas is supplied to the engine 2, the air-fuel ratio shifts to the rich side as compared with before the purge gas is supplied to the engine 2. As a result, the ECU 100 corrects the fuel injection amount of the injector 4 in order to control the air-fuel ratio to the target air-fuel ratio. The purge gas concentration can be specified by using the correction amount of the fuel injection amount when the purge gas is supplied to the engine 2.

(Calibration of step motor type control valve)
As described above, in the purge systems 20, 220, 320, 420, the purge gas is supplied to the engine 2 using the step motor type control valve 40. In the step motor type control valve 40, the position (step value) at which the closed state is switched to the open state may deviate from the original position due to the tolerance of the components. By specifying the step value at which the step motor type control valve 40 switches from the closed state to the open state, it is possible to suppress the purge flow rate from deviating from the set value. Note that the calibration of the step motor type control valve 40 is not always necessary for the purge systems 220 and 420 that use the VSV type control valve 42 when the engine 2 is driven in the light load region. As described above, it is when the differential pressure between the upstream side and the downstream side of the control valve is large (the engine 2 is driven in the light load range) that the variation in the opening degree of the control valve has a large influence on the purge flow rate. In other words, when the engine 2 is driven in a load range higher than the light load range, the influence of the variation in the opening of the control valve on the purge flow rate is small. Therefore, in the purge systems 220 and 420, calibration of the step motor type control valve 40 can be omitted. Hereinafter, a method of calibrating the step motor type control valve 40 will be described with reference to FIG. The following processing is executed by the control unit 102.

As shown in FIG. 5, first, in step S2, it is determined whether or not the valve opening start position (valve opening start step value) of the step motor control valve 40 has been specified. That is, it is determined whether or not the valve opening start step value of the step motor type control valve 40 is stored in the memory of the control unit 102. If the valve opening start position has already been specified (step S2: YES), the process ends. When the valve opening start position is not specified (step S2: NO), the engine 2 is driven in the light load range and the step value of the step motor type control valve 40 is set to the lower limit value (step S4). That is, in step S4, the step motor type control valve 40 is closed. Since the step motor type control valve 40 is closed, the purge gas is not supplied to the engine 2. Next, the air-fuel ratio (the detection value of the air-fuel ratio sensor 36) is read (step S6), and the pressure in the intake pipe 34 (the detection value of the pressure sensor 56) is read (step S8). Either of the processes of steps S6 and S8 may be performed first, or the processes may be performed simultaneously.

Next, the step value of the step motor type control valve 40 is increased by "1 step" (step S10), then the air-fuel ratio is read (step S12), and the pressure in the intake pipe 34 is read (step S14). Either of the processes of steps S12 and S14 may be performed first, or the processes may be performed simultaneously. After that, the change α1 of the air-fuel ratio is calculated (step S16). That is, the value of the air-fuel ratio read in step S6 is subtracted from the value of the air-fuel ratio read in step S12. Note that the change α1 is calculated by the CPU in the control unit 102.

Next, the absolute value of the change |α1| is compared with the predetermined value X1 (step S18). If the change |α1| is larger than the predetermined value X1 (step S18: YES), the step motor control valve 40 opens. Then, it is determined that the purge gas is being supplied to the engine 2. After that, the process proceeds to step S20, the valve opening start position (step value of valve opening start) of the step motor type control valve 40 is stored in the memory in the control unit 102 (step S20), and the calibration process of the step motor type control valve 40 is performed. finish. The predetermined value X1 is a threshold value indicating whether or not the purge gas is being supplied to the engine 2, and is stored in the memory in the control unit 102. By comparing the change |α1| with the predetermined value X1, it is possible to prevent the erroneous valve opening start step value (the step value at which the step motor type control valve 40 is not opened) from being stored due to a measurement error. ..

As described above, when the step motor type control valve 40 is opened and the purge gas is supplied to the engine 2, the air-fuel ratio normally changes. However, when the concentration of the purge gas is equal to the engine 2 target air-fuel ratio (for example, the ideal air-fuel ratio), the air-fuel ratio does not change even if the purge gas is being supplied to the engine 2. Therefore, when the change |α1| is equal to or smaller than the predetermined value X1 in step S18 (step S18: NO), the change β1 of the pressure in the intake pipe 34 is calculated (step S22). That is, the CPU in the control unit 102 subtracts the pressure in the intake pipe 34 read in step S14 from the pressure in the intake pipe 34 read in step S8.

Next, the absolute value of change |β1| is compared with the predetermined value Y1 (step S24). If the change |β1| is larger than the predetermined value Y1 (step S24: YES), the step motor control valve 40 opens. Then, it is determined that the purge gas is being supplied to the engine 2. After that, the process proceeds to step S20, the valve opening start position (step value of valve opening start) of the step motor type control valve 40 is stored in the memory in the control unit 102 (step S20), and the calibration process of the step motor type control valve 40 is performed. finish. The predetermined value Y1 is a threshold value indicating whether or not the purge gas is supplied to the intake pipe 34, and is stored in the memory in the control unit 102. When the change |β1| is equal to or less than the predetermined value Y1 in step S24 (step S24: NO), it is determined that the step motor type control valve 40 is not open and the purge gas is not supplied to the intake pipe 34, and the step Returning to S10, the step value of the step motor type control valve 40 is further increased by "1 step".

Note that, as described above, the calibration process of the step motor type control valve 40 is performed while the engine 2 is driven in the light load range. When the engine 2 is driven in the light load region, the differential pressure between the upstream side and the downstream side of the step motor type control valve 40 is large. Therefore, when the step motor type control valve 40 changes from the closed state to the open state, a relatively large flow rate of purge gas is supplied to the intake pipe 34 even if the valve opening ratio is small, and the pressure in the intake pipe 34 is reduced. Changes clearly. Similarly, the air-fuel ratio value also changes clearly. That is, the open position of the step motor type control valve 40 is specified (calibrated) by maintaining the pressure in the intake pipe 34 below -40 kPa (driving the engine 2 in the light load region). (Valve opening step value) can be accurately specified.

(Detection of first purge gas concentration)
As described above, the purge gas concentration can be specified by utilizing the phenomenon that the air-fuel ratio deviates from the target air-fuel ratio when the purge gas is supplied to the engine 2. Therefore, if the air-fuel ratio is detected, the purge gas concentration can be detected even if the purge gas concentration gradually changes. However, when the purge gas concentration is unknown, such as immediately after the start of the engine 2, when the purge gas is supplied to the engine 2 by normal control, the air-fuel ratio may be excessively affected (for example, overrich). Therefore, it is necessary to detect the purge gas concentration for the first time while suppressing the influence on the air-fuel ratio. Hereinafter, a method of detecting the purge gas concentration for the first time will be described with reference to FIG. The following processing is executed by the control unit 102.

As shown in FIG. 6, first, in step S30, it is determined whether or not the first purge gas concentration has been detected. That is, it is determined whether or not the purge gas concentration after starting the engine 2 is stored in the memory of the control unit 102. If the first purge gas concentration has been detected (step S30: YES), the process ends. When the initial purge gas concentration is not detected (step S30: NO), the engine 2 is driven in the medium load range (pressure in the intake pipe 34: -40 kPa or more and -15 kPa or less), and the air-fuel ratio is stoichiometric (theoretical air-fuel ratio). Control (step S32). Next, the step motor type control valve 40 is fully closed (step S34). That is, in step S34, the purge gas is controlled so as not to be supplied to the engine 2.

Next, the air-fuel ratio correction amount calculated using the detection value of the air-fuel ratio sensor 36 is read, and the read air-fuel ratio correction amount is stored (step S36). As described above, the ECU 100 calculates the correction value of the air-fuel ratio using the detection value of the air-fuel ratio sensor 36, and the air-fuel ratio becomes the target air-fuel ratio (stoichiometric in the case of this processing) based on the calculated correction value. Feedback control of the injector 4 is performed. That is, after the engine 2 is started, the ECU 100 always continues to calculate the correction amount of the air-fuel ratio and keeps the air-fuel ratio at the target air-fuel ratio. When the detected air-fuel ratio is stoichiometric, the air-fuel ratio correction amount is zero.

Next, the step motor type control valve 40 is increased by a predetermined step value (step S38). The predetermined step value (the number of steps to be increased) is not particularly limited, but the number of steps by which the purge gas is reliably supplied to the engine 2 is set.

Next, the air-fuel ratio correction amount, the pressure in the intake pipe 34 (the detection value of the pressure sensor 56), and the intake air amount into the intake pipe 34 (the detection value of the air flow meter 39) are read (step S40). Next, the change α2 of the air-fuel ratio is calculated (step S42). In step S42, the value of the air-fuel ratio correction amount read in step S36 is subtracted from the value of the air-fuel ratio correction amount read in step S40 to calculate the change α2. Note that either step S42 or step S44, which will be described later, may be performed first or simultaneously.

Next, the purge rate A2 is calculated (step S44). The purge rate A2 is calculated by first determining the purge flow rate from the step value of the step motor type control valve 40 (the opening degree of the step motor type control valve 40) and the pressure in the intake pipe 34. Specifically, a table (or a relational expression) in which the relationship between the pressure in the intake pipe 34 and the purge flow rate is written is created in advance for each step value of the step motor type control valve 40, and the memory in the control unit 102 is created. Remember. Then, with reference to the step value table set in step S38, the purge flow rate is obtained based on the pressure in the intake pipe 34 (detection value of the pressure sensor 56) read in step S40. When the pressure sensor 56 is a type that detects absolute pressure, the pressure in the intake pipe 34 is calculated by subtracting the atmospheric pressure from the detection value of the pressure sensor 56. Next, the purge rate A2 is calculated using the purge flow rate and the intake air amount (detected value of the air flow meter 39) read in step S40. The purge rate A2 can be calculated by dividing the purge flow rate by the flow rate of the gas flowing in the intake pipe 34. Specifically, the purge rate A2 is calculated by the following equation (1). In the following formula (1), “pg” indicates the purge flow rate (g/s), and “pa” indicates the intake air amount (g/s) to the intake pipe 34.
Formula 1: A2(%)=pg/(pa+pg)×100

Next, the purge gas concentration is calculated from the change α2 in the air-fuel ratio calculated in step S42 and the purge rate A2 calculated in step S44 (step S46). Next, the calculated purge gas concentration is stored in the memory in the control unit 102 (step S48), the drive of the engine 2 is returned to the normal operation control (for example, high load range stoichiometric operation) (step S50), and the process is ended. ..

As described above, the first time the purge gas concentration is detected, the engine 2 is driven in the medium load range (the inside of the intake pipe 34 is adjusted to -40 kPa or higher and -15 kPa or lower), and the step motor type control valve 40 is opened to purge gas. Is supplied to the intake pipe 34, and the purge gas concentration is detected based on the opening of the step motor type control valve 40, the pressure inside the intake pipe 34, the intake air amount of the intake pipe 34, and the value of the air-fuel ratio. When the opening degree of the step motor control valve 40 is equal, the purge flow rate supplied to the intake pipe 34 increases as the pressure in the intake pipe 34 decreases (the negative pressure increases). However, the change in the purge flow rate is not proportional to the change in the pressure in the intake pipe 34. As for the purge flow rate, in the high load region where the pressure in the intake pipe 34 is high (negative pressure is small), the purge flow amount greatly increases due to a slight decrease in the intake pipe 34 pressure (slight increase in the negative pressure), and in the medium load region. It increases slowly and does not change much in the low load region.

In the above process, the purge flow rate is used as a factor for detecting the purge concentration (a factor for calculating the purge rate), as shown in the above equation (1). Therefore, when the purge gas concentration is unknown (first-time detection of the purge gas concentration), it is not preferable to perform it in a high load range in which the purge flow rate largely changes due to a slight change in the intake pipe 34 pressure. Further, since the purge flow rate in the high load region is small, the purge rate becomes small in the high load region as is clear from the above equation (1), and therefore it is not suitable for detecting the purge gas concentration. Further, in the light load region (the pressure in the intake pipe 34 is low), for example, when the purge gas concentration is high, a large amount of purge gas may be supplied to the engine 2, which may have an excessive influence on the air-fuel ratio. Therefore, it is not preferable to perform the initial barge gas concentration detection in the light load region. In the above process, the first time the purge gas concentration is detected in the medium load range, the concentration can be accurately detected without significantly affecting the air-fuel ratio.

(Switching between VSV type control valve and step motor type control valve)
As described above, the purge systems 220 and 420 include both the VSV type control valve 42 and the step motor type control valve 40, and use the VSV type control valve 42 when driving the engine 2 in the light load region. The purge flow rate is controlled, and when the engine 2 is driven in the high load range, the step motor type control valve 40 is used to control the purge flow rate. However, when the purge gas concentration is high, the air-fuel ratio may be excessively affected only by the opening of the control valve slightly deviating from the control value (that is, the purge flow rate deviating from the control value). Therefore, in the purge systems 220 and 420, the purge flow rate is controlled by the VSV type control valve 42 when the purge gas concentration is equal to or higher than a predetermined value, and the purge flow rate is controlled by the step motor type control valve 40 when the purge gas concentration is lower than the predetermined value. Switch to control. Hereinafter, the switching process of the VSV type control valve 42 and the step motor type control valve 40 will be described with reference to FIG. 7.

As shown in FIG. 7, first, it is determined whether or not the purge execution condition is satisfied (step S60). In step S60, it is determined that purging is possible when the remaining amount of the battery (battery charged by the power generation of the engine 2) is within a certain range, and purging is not possible when the remaining amount is outside the certain range. When the purge execution condition is not satisfied (step S60: NO), both the VSV type control valve 42 and the step motor type control valve 40 are fully closed (step S78), and the process ends. When the purge execution condition is satisfied (step S60: YES), the process proceeds to step S62, and it is determined whether the purge gas concentration has been detected. That is, it is determined whether the purge gas concentration is stored in the memory of the control unit 102.

When the purge gas concentration has been detected (step S62: YES), the detected purge gas concentration C1 (the purge gas concentration stored in the memory of the control unit 102) is compared with the predetermined value Z1 (step S72). That is, it is determined whether the purge gas concentration C1 is less than the predetermined value Z1. It should be noted that the predetermined value Z1 is set when the engine 2 is driven in a high load range and the purge flow rate is controlled by the step motor type control valve 40 if the opening variation of the step motor type control valve 40 is within the tolerance (that is, , If the variation in the purge flow rate supplied to the engine 2 is within the allowable range), the concentration is set so as not to have an excessive influence on the air-fuel ratio.

When the purge gas concentration is not detected (step S62: NO) and when the purge gas concentration C1 is the predetermined value Z1 or more (step S72: NO), the process proceeds to step S64 and the purge flow rate is controlled using the VSV type control valve 42. To do. In this case, the engine 2 is driven in the light load range. That is, when the purge gas concentration is high (predetermined value Z1 or more) and when the purge gas concentration is unknown, the VSV type control valve 42 controls the purge flow rate. Next, the purge gas concentration C2 is detected while controlling the purge flow rate by the VSV type control valve 42 (step S66). The method of detecting the purge gas concentration has been described above, and will be omitted.

Next, it is determined whether the detected purge gas concentration C2 is less than the predetermined value Z1 (step S68). When the purge gas concentration C2 is less than the predetermined value Z1 (step S68: YES), the purge gas concentration C2 is stored in the memory of the control unit 102, and the process ends. That is, the purge gas concentration C1 described above is updated to the purge gas concentration C2. On the other hand, when the detected purge gas concentration C2 is equal to or higher than the predetermined value Z1 (step S68: NO), the process returns to step S64 and the purge flow rate is continuously controlled using the VSV type control valve 42.

When the purge gas concentration C1 is less than the predetermined value Z1 in step S72 (step S72: YES), the process proceeds to step S74, and the purge flow rate is controlled using the step motor type control valve 40. In this case, the engine 2 is driven in the high load range. Next, the purge gas concentration C3 is detected while controlling the purge flow rate by the step motor type control valve 40, the purge gas concentration C3 is stored in the memory of the control unit 102 (step S76), and the process is ended. That is, the purge gas concentration C1 described above is updated to the purge gas concentration C3.

In the above process, when the purge gas concentration is equal to or higher than the predetermined value, the purge flow rate is controlled using the VSV type control valve 42, and when the purge gas concentration is lower than the predetermined value or when the purge gas concentration is lower than the predetermined value. The purge flow rate is controlled using the step motor type control valve 40. Therefore, a large amount of purge gas can be supplied to the engine 2 while suppressing the air-fuel ratio from deviating from the target air-fuel ratio.

(Other embodiments)
In the above embodiment, the pressure (negative pressure) in the intake pipe or the example in which the purge gas is supplied to the intake pipe by using the ejector has been described. However, a pump may be arranged on the purge passage and the purge gas may be pumped to the intake pipe. Even in this case, the differential pressure between the upstream side and the downstream side of the control valves (VSV type control valve and step motor type control valve) is utilized to calibrate the above step motor type control valve, detect the purge gas concentration for the first time, and control the VSV type. The process of switching the valve and the step motor type control valve can be executed.

Further, in the purge systems 20, 220, 320 and 420, it is not always necessary to perform both (1) calibration of the step motor type control valve and (2) initial detection of the purge gas concentration. Only the process (1) or the process (2) may be performed, or both the process (1) and the process (2) may not be performed. Similarly, in the purge systems 220 and 420, the switching processing between the VSV type control valve and the step motor type control valve is not performed, and normally (when the engine is driven in the high load range), the purge flow rate is set by the step motor type control valve. The purge flow rate may be controlled by the VSV type control valve only when the engine is driven in a light load range by controlling the purge flow rate.

The embodiments of the present invention have been described above in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. Further, the technical elements described in the present specification or the drawings exert technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technique illustrated in the present specification or the drawings achieves a plurality of purposes at the same time, and achieving the one purpose among them has technical utility.

2: Engine (engine for power generation)
14: Fuel tank 19: Canister 20: Purge system 24: Purge passage 34: Intake pipe 40: Step motor type control valve

Claims (5)

A purge system for an electric vehicle equipped with a power generation engine,
A canister for adsorbing the evaporated fuel generated in the fuel tank,
A purge passage connecting the intake pipe and the canister connected to the power generation engine,
A step motor type control valve provided on the purge passage for controlling the flow rate of the purge gas,
Purge system equipped with. The purging system according to claim 1, wherein
A purge system in which a VSV type control valve for controlling the flow rate of purge gas by a duty ratio is provided in parallel with a step motor type control valve on a purge passage. The purging system according to claim 2, wherein
When the purge gas concentration is equal to or higher than a predetermined value, the VSV type control valve controls the flow rate of the purge gas,
A purge system that controls the flow rate of purge gas with a step motor type control valve when the concentration of purge gas is less than a predetermined value. The purging system according to any one of claims 1 to 3,
When detecting the first purge gas concentration,
Adjust the pressure in the intake pipe to -40 kPa or higher and -15 kPa or lower,
Open the step motor type control valve to supply purge gas to the intake pipe,
A purge system that performs control to detect the purge gas concentration based on the opening of the step motor type control valve, the pressure in the intake pipe, the intake air amount of the intake pipe, and the value of the air-fuel ratio. A purge system according to any one of claims 1 to 4, wherein
A purge system that performs control to identify the opening position of a step motor type control valve while maintaining the pressure in the intake pipe at a pressure of less than -40 kPa.

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