JP5863490B2 - Intake air circulation system for internal combustion engine - Google Patents

Description

  The present invention relates to an intake air circulation device for an internal combustion engine that reduces the amount of overshoot at the time of load interruption that has been applied during operation of the internal combustion engine.

An internal combustion engine is used as a power source for operating a power plant or the like. As these internal combustion engines, gas engines are widely adopted for the purpose of diversifying fuels that use methane gas or the like with high output and economy.
However, if the load acting on the gas engine for some reason is cut off (for example, the power generation is stopped due to a malfunction of the power generation facility, etc.), the engine will rotate until the load suddenly disappears. Over-rotation (overshoot) in which the number of revolutions suddenly increases occurs due to the rotational inertial force that has been maintained.

When the overshoot occurs, the exhaust gas emission amount and the pressure increase as the engine speed increases. If the exhaust gas emission amount and pressure increase, the turbocharger may rotate, the supply air pressure and amount increase, and the burden on the engine and turbocharger may increase, leading to equipment failure or damage. Becomes higher.
In order to improve the overshoot, in addition to increasing the moment of inertia, it is conceivable to reduce the mixed gas (fuel gas + air) present in the intake chamber when shut off.
The increase of the moment of inertia which is one of the measures can suppress the rotation fluctuation with respect to the load fluctuation due to the increase of the inertia moment.
However, the moment of inertia is determined by the size of the crankshaft system and the generator, and there is a limit to increasing the moment of inertia.
As another measure, intake chamber volume reduction (inlet manifold + intake pipe volume) cannot be easily reduced because an intercooler having a large air volume is interposed in the intake pipe.

Japanese Utility Model Laid-Open No. 61-1114050 (Patent Document 1) discloses a reduction of the mixed gas in the intake pipe.
According to Patent Document 1, as shown in FIG. 6, the gas engine A is provided with a cylinder 01, and the cylinder 01 is provided with an intake valve 02 and an exhaust valve 03. An exhaust manifold 05 is connected to the exhaust valve 03 side, and the other side allows exhaust gas to flow into the turbine 061 side of the supercharger 06.
An intake manifold 04 is connected to the intake valve 02 side, and supply air is supplied from an air cooler 07.
The compressor 062 of the supercharger 06 compresses air from an air cleaner (not shown) and pumps it to the air cooler 07 via the intake pipe 08.
A bypass pipe 081 that connects the intake upstream side of the compressor 062 and the intermediate portion of the intake pipe 08 is interposed. An air volume adjusting valve 09 that opens and closes by driving the adjusting mechanism 011 via the interlocking mechanism 013 is disposed in the middle portion of the bypass pipe 081.

  Then, when the engine load becomes no load, the governor 011 opens the air volume adjustment valve 09 via the interlocking mechanism 013 to reduce the air volume of the intake pipe 08 and can be applied to the supercharger surging countermeasure. Has been made.

Japanese Utility Model Publication No. 61-114050

  However, the disclosed technique of Patent Document 1 is a countermeasure against a surging phenomenon in which the entire gas flowing through the intake system including the compressor 062 and the intake pipe 08 vibrates violently in the flow direction, and is used as a countermeasure against overshoot when the load of the internal combustion engine is interrupted is not.

  The present invention has been made to solve such problems, and suppresses the amount of overshoot that occurs when the load acting on the internal combustion engine is cut off, thus reducing the burden on the engine and turbocharger. An object of the present invention is to provide a highly reliable internal combustion engine in which the risk of breakdown or damage to equipment is reduced.

In order to solve the problem, the present invention provides an internal combustion engine, an air cleaner for purifying air to the internal combustion engine,
An intake pipe connecting the internal combustion engine and the air cleaner;
A mixing device that mixes fuel gas with the air flowing through the intake pipe to generate a mixed gas;
A turbocharger for pressurizing the mixed gas generated by the mixing device ;
An intercooler that cools the mixed gas pressurized by the turbocharger ,
The mixing device, the turbocharger, and the intercooler are provided in order from the upstream side of the intake pipe,
Furthermore, a volume portion provided via an inflow pipe communicated between the intercooler and the internal combustion engine,
An on-off valve provided in the inflow pipe;
Load interruption detection means for detecting that the load acting on the internal combustion engine has been interrupted;
A rotational speed detection means for detecting the rotational speed of the internal combustion engine;
A control device for controlling the opening and closing operation of the on-off valve,
When the load shut-off detection means detects a load shut-off, the controller opens the on-off valve to cause a part of the mixed gas flowing through the intake pipe to flow into the volume portion, and the rotational speed The on-off valve is closed when the detection means detects that the increase in the rotational speed of the internal combustion engine has stopped or is decreasing.

  According to this invention, when the load acting on the internal combustion engine is shut off, the internal combustion engine prevents the rotational speed from rapidly increasing (overshoot) due to the rotational inertial force that has been maintained until then. Effect of reducing the amount of fuel gas supplied to the internal combustion engine and suppressing the rotational force of the internal combustion engine and suppressing the rapid increase in the rotational speed by flowing a part of the mixed gas supplied to the internal combustion engine Can be obtained.

Preferably, in the present invention, an outflow pipe having one end communicating with the volume portion and the other end communicating between the mixing device and the turbocharger, and a flow rate adjusting valve interposed in the outflow pipe, Prepared,
The flow rate adjustment valve is opened by the control device with a delay from the opening operation time of the opening / closing valve, and the mixed gas in the volume part is returned to the upstream side of the turbocharger of the intake pipe, and the rotation speed detection means May be closed when it is detected that the internal combustion engine has stopped increasing or is decreasing.
Further, by returning the mixed gas to the upstream side of the turbocharger, it is possible to lengthen the time until the returned mixed gas flows into the inlet manifold, thereby improving the buffer effect of the volume portion.

  According to this invention, since the upward tendency of over-rotation (overshoot) when the load of the internal combustion engine is interrupted converges within one second, after the occurrence, the timing is delayed from the opening operation time of the on-off valve to open the flow regulating valve. By controlling, the no-load operation of the internal combustion engine is stabilized early.

  In the present invention, it is preferable that the volume of the volume portion is approximately ¼ of the volume of the intake manifold.

  According to this invention, if the volume of the volume portion is too small, the rotation of the internal combustion engine cannot be affected. On the other hand, if the volume of the volume portion is too large, the mixed gas is not sufficiently supplied to the internal combustion engine, so that rotation spots occur in the internal combustion engine, and it may be stopped in some cases. By making the volume of the volume body approximately ¼ of the volume of the intake manifold, over-rotation (overshoot) could be rapidly converged.

  In the present invention, it is preferable that the attachment position of the flow rate adjusting valve be disposed in the volume portion or the outflow pipe close to the volume portion.

  According to this invention, since the mixed gas in the volume portion has a higher pressure than the mixed gas in the intake pipe at the outlet of the outflow pipe, the pressure of the mixed gas in the intake pipe decreases when the flow rate adjusting valve is located near the intake pipe. It is difficult to prevent the over-rotation preventing effect from becoming insufficient.

  Preferably, in the present invention, an ignition cut means for cutting the ignition of the mixed gas is provided in a part of the plurality of combustion chambers provided in the internal combustion engine, and the load shut-off detection means shuts off the load. The ignition cut means may be operated when detected, and the ignition cut means may be stopped when the rotation speed detection means detects that the rotation speed of the internal combustion engine has stopped increasing or is decreasing.

  According to such an invention, in a part of the plurality of combustion chambers arranged in the internal combustion engine, the ignition of the mixed gas is cut to reduce the rotational speed of the internal combustion engine, and the cut combustion chamber (cylinder) ) Can effectively suppress the increase in rotation due to the engine braking effect (rotational resistance caused by the load compressing the mixed gas in the cylinder).

  In the present invention, it is preferable that the combustion chamber for performing the ignition cut should not be continued for two or more cylinders in the ignition order during normal operation of the internal combustion engine.

  According to this invention, by preventing the combustion chamber (cylinder) that performs the ignition cut from being continued, the possibility of an increase in the concentration of the unburned gas mixture is reduced as much as possible. Risk can be suppressed.

  Preferably, in the present invention, the internal combustion engine is provided with a retard means for retarding the ignition timing of the mixed gas with respect to a normal operation, and the retard means is operated when the load shut-off detecting means detects a load shut-off. When the rotational speed detection means detects that the rotational speed of the internal combustion engine has stopped increasing or decreased, the retarding means may stop operating.

According to this invention, by retarding the ignition timing of the mixed gas with respect to the normal operating character, the combustion efficiency of the mixed gas is lowered, and the conversion efficiency of the combustion energy into motive energy is lowered.
Therefore, the overshoot at the time of load interruption can be suppressed by reducing the influence of the rotation-up by reducing the conversion to motive energy.

  In this way, the amount of overshoot that occurs when the load acting on the internal combustion engine is cut off is reduced, reducing the burden on the engine and turbocharger, and reducing the risk of equipment failure or damage The internal combustion engine can be made high.

1 shows an overall schematic configuration diagram according to a first embodiment of the present invention. FIG. The whole schematic block diagram by 2nd Embodiment which concerns on this invention is shown. (A) shows the operation | movement timing chart figure of the component apparatus in the 1st-4th embodiment which concerns on this invention, (B) shows the implementation condition figure of each embodiment. The comparative example of the rotation speed fall at the time of changing the volume part + ignition cut and flow control valve opening delay by 3rd Embodiment which concerns on this invention is shown, (A) is 1set, and (B) is ignition cut number. The number of cuts is 2set, and (C) indicates the number of ignition cuts is 3set. The comparison figure of the rotation speed fall result of the volume part + retard (changed) by 3rd Embodiment which concerns on this invention is shown. An explanatory view of prior art is shown.

Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.
However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to specific examples unless otherwise specifically described. Only.

(First embodiment)
FIG. 1 shows an overall configuration diagram according to the present invention. Reference numeral 1 denotes an internal combustion engine. The internal combustion engine 1 is a V-type 16-cylinder power generation gas engine inclined in a V-shape around the rotation axis of a crankshaft (not shown) of the internal combustion engine 1.
The internal combustion engine 1 (hereinafter abbreviated as “engine 1”) is arranged in a V shape in the RH bank 11 and the LH bank 12, and 8 cylinders are arranged in each bank.
An inlet manifold 15 for introducing a mixed gas into the combustion chamber 14 of each cylinder of each bank is connected to the V-shaped space of the RH bank 11 and the LH bank.
The inlet manifold 15 includes inlet manifolds of both RH and LH banks.
On the other hand, an RH exhaust manifold 16 for deriving exhaust gas discharged from the combustion chamber 14 is disposed outside the RH bank 11, and an LH exhaust manifold 17 for deriving exhaust gas discharged from the combustion chamber 14 is disposed outside the LH bank 12, respectively. It is installed.

The inlet manifold 15 is connected to an intake pipe 5 for introducing a mixed gas obtained by mixing air from the air cleaner 3 and fuel gas mixed from the middle into the inlet manifold 15.
The intake pipe 5 includes, in order from the upstream side of the air supply system path, a mixing device 7 that mixes fuel gas with air, an RH turbocharger 18 that is driven by exhaust gas from the RH exhaust manifold 16 and pressurizes the mixed gas, The engine speed is adjusted by adjusting the flow rate of the LH turbocharger 19 which is arranged in parallel with the RH turbocharger 18 and is driven by the exhaust gas from the LH exhaust manifold 17 to pressurize the mixed gas, and the mixed gas flowing through the intake pipe 5. A throttle valve 51 for control and an intercooler 52 for cooling the mixed gas pressurized and heated by the turbochargers LH and RH are provided.

The exhaust gas that has driven the LH turbocharger 19 flows through the second exhaust pipe 85, joins the first exhaust pipe through which the exhaust gas that has driven the RH turbocharger 18 flows, and is introduced into the exhaust gas treatment device 8.
The exhaust gas introduced into the exhaust gas treatment device 8 is rendered harmless by the oxidation catalyst 81 and the denitration catalyst 82 and released to the atmosphere.

A control device 6 controls the engine 1. The control device 6 includes a rotation speed sensor 62 that is a rotation speed detection means for detecting the rotation speed of the engine 1 and a load interruption detection that detects power interruption / connection to a generator (not shown) that is driving the engine 1. A load sensor 61 as a means is input. The throttle valve 51 adjusts the flow rate of the mixed gas flowing through the intake pipe 5 by the control device 6, and maintains the rotational speed of the engine 1 within the set rotational speed region.
The mixing device 7 adjusts the mixing ratio of air and fuel gas so that the control device 6 can maintain the rotational speed within the set rotational speed region in accordance with the rotational speed change of the engine 1.

A buffer 2 is a volume part having a space for instantaneously sucking the mixed gas in the intake pipe 5. The buffer 2 has an inflow pipe 21 having one end communicating with the intake pipe 5 between the intercooler 52 and the inlet manifold 15 and the other end communicating with the buffer 2 serving as a volume portion. The inflow pipe 21 is provided with an on-off valve 25 that controls the flow of the mixed gas from the intake pipe 5 into the volume space, and is operated by the control device 6.
Accordingly, since the mixed gas instantaneously flows from the intake pipe 5 into the buffer 2, the amount of the mixed gas flowing into the inlet manifold 15 is reduced, and the rotational force of the engine 1 is suppressed.

The operation of this embodiment will be described based on the range of the first embodiment of FIG.
The engine 1 is controlled by the control device 6 so as to operate at a constant rotation and a constant output when the generator is driven.
During operation of the engine 1, an abnormality occurs in the power generation facility, and the power of the engine 1 is cut off from the generator in order to stop the power generation. At this time, since the load acting on the engine 1 is suddenly cut off, the engine 1 generates a so-called overshoot in which the rotational speed increases so far that the rotational speed increases as the load disappears. In the case of the present embodiment, the time from when the load is interrupted until the overshoot shifts to a downward trend is approximately 0.5 to 0.6 sec.
When the load fluctuates, the load sensor 61 detects load interruption, and the control device 6 opens the on-off valve 25 after t1. t1 is a time lag until the output starts to decrease.
Therefore, the load sensor 61 detects the time point when the output starts to decrease.
In this embodiment, the load sensor 61 is used as a means for detecting power interruption / contact. However, when the rotational speed sensor 62 is rapidly increased (for example, the rotational speed is 1% or more / 100 mmsec), the power is It can also be determined as being blocked.

When the opening / closing valve 25 is opened by the control device 6, the pressurized mixed gas in the intake pipe 5 instantaneously flows into the buffer 2 which is a volume part.
At this time, since the mixed gas in the intake pipe 5 is pressurized by the turbochargers 18 and 19, it flows in instantaneously when the on-off valve 25 is opened.
The amount of the mixed gas in the portion of the intake pipe 5 where the inflow pipe 21 is connected is the mixing ratio of the air and fuel gas corresponding to the engine speed at that time in the mixing device 7 and the throttle valve 51 on the upstream side. Although the amount of gas is present, a part of the mixed gas flows out to the buffer 2 side at that portion, so that the insufficiently mixed gas is supplied to the combustion chamber 14 of the engine 1.
Therefore, the combustion efficiency in the combustion chamber is reduced, and the engine speed is also reduced. Therefore, it becomes possible to suppress the maximum number of overshoots to an allowable number of revolutions.

When it is detected by the rotational speed sensor 62 that the engine 1 continues to rise due to the overshoot and stops rising or descends (after t0), the control device 6 closes the on-off valve 25. Even in this state, the decreasing tendency of the engine speed is maintained.
Since the pressure of the air-fuel mixture flowing into the buffer 2 decreases on the side of the intake pipe 5, the air-fuel mixture returns to the side of the intake pipe 5 based on the decrease, and the pressure of the mixed gas in the buffer 2 decreases.

In the present embodiment, the volume of the buffer 2 is set to approximately 1/4 of the inlet manifold 15 (including both the RH and LH banks).
If the volume of the volume portion is too small, this cannot affect the rotation of the engine 1. On the other hand, if the volume of the volume portion is too large, the amount of mixed gas flowing into the inlet manifold 15 side is reduced, causing rotation spots in the engine 1 and possibly stopping. The volume of the volume body was set to about 1/4 of the volume of the intake manifold.
In addition, it was also considered that the time t0 until the overshoot starts and the increasing tendency of the rotation speed stops or moves down is 0.5 to 0.6 sec. (See Figure 3)
Further, by connecting one end of the inflow pipe 21 between the intercooler 52 and the inlet manifold 15, the mixed gas supply amount to the inlet manifold 15 is effectively reduced without being affected by the intercooler 52. I was able to do that.
Together, the effects of these measures have made it possible to reduce the maximum overshoot rpm of the overshoot.

(Second Embodiment)
Since the present embodiment is the same as the first embodiment except for the structure for discharging the mixed gas introduced into the volume portion (buffer), the overall description is omitted, and only the different portions will be described. In this case, the same parts are denoted by the same reference numerals and description thereof is omitted.

FIG. 2 shows an overall configuration diagram of the second embodiment according to the present invention.
The internal combustion engine 1 is a V-type 16-cylinder power generation gas engine that is inclined in a V shape around the rotation axis of a crankshaft (not shown).
An inlet manifold 15 is connected to a V-shaped space of the internal combustion engine 1 (hereinafter abbreviated as “engine 1”).
On the other hand, an RH exhaust manifold 16 is disposed outside the RH bank 11, and an LH exhaust manifold 17 is disposed outside the LH bank 12.

The inlet manifold 15 is connected to an intake pipe 5 for introducing a mixed gas obtained by mixing air and fuel gas into the inlet manifold 15.
In the intake pipe 5, a mixing device 7 that mixes fuel gas with air, an RH turbocharger 18, and an LH turbocharger 19 disposed in parallel with the RH turbocharger 18, in order from the upstream side of the air supply system path. A throttle valve 51 and an intercooler 52 are provided.

  Then, the exhaust gas that has driven the LH turbocharger 19 and the RH turbocharger 18 is introduced into the exhaust gas treatment device 8, detoxified in the exhaust gas treatment device 8, and released to the atmosphere.

A control device 6a controls the engine 1. The control device 6a includes a rotation speed sensor 62 that is a rotation speed detection means for detecting the rotation speed of the engine 1 and a load interruption detection that detects power interruption / disconnection to a generator (not shown) that is driving the engine 1. A load sensor 61 as a means is input. The throttle valve 51 adjusts the flow rate of the mixed gas flowing through the intake pipe 5 by the control device 6, and maintains the rotational speed of the engine 1 within the set rotational speed region.
The mixing device 7 adjusts the mixing ratio of air and fuel gas so that the control device 6 can maintain the rotation speed within a set rotation speed region in accordance with the rotation speed and load of the engine 1.

A buffer 2a is a volume part having a space for instantaneously sucking the mixed gas in the intake pipe 5. The buffer 2a has an inflow pipe 21 having one end communicating with the intake pipe 5 between the intercooler 52 and the inlet manifold 15, and the other end communicating with the buffer 2a which is a volume portion. The inflow pipe 21 is provided with an on-off valve 25 for controlling the inflow of the mixed gas from the intake pipe 5 into the buffer 2a which is a volume part. The on-off valve 25 is operated by the control device 6a.
Further, an outflow pipe 22 is disposed on the opposite side of the inflow pipe 21 in the buffer 2a. One of the outflow pipes 22 communicates with the intake pipe 5 between the mixing device 7 and the RH and LH turbochargers 18 and 19, and the other communicates with the buffer 2a. A flow rate adjusting valve 26 that discharges the mixed gas flowing into the buffer 2a while adjusting the flow rate to the upstream side of the RH and LH turbochargers 18 and 19 is disposed near the buffer 2a of the outflow pipe 22. The flow rate adjusting valve 26 is controlled by the control device 6a.
The flow regulating valve 26 may be directly attached to the buffer 2a, and the outflow pipe 22 may be attached to the buffer 2a.
Further, the volume of the buffer 2a is set to approximately ¼ of the inlet manifold 15 (including both the RH and LH banks) based on the same concept as in the first embodiment.
In this case, the assembly man-hours due to the reduction in the number of assembling steps and the number of assembling points are reduced, and the quality stability is improved.

The operation of the present embodiment will be described based on the time chart of FIG.
The engine 1 is controlled by the control device 6 so as to operate at a constant rotation and a constant output when the generator is driven.
During operation of the engine 1, an abnormality occurs in the power generation facility, and the power of the engine 1 is cut off from the generator in order to stop the power generation.
At this time, overshoot occurs in the engine 1.
When the load fluctuates (shuts off), the load sensor 61 detects the load shut-off, and the control device 6 opens the on-off valve 25 after t1. t1 is a time lag until it is detected that the load is cut off.
When the opening / closing valve 25 is opened by the control device 6, the pressurized mixed gas in the intake pipe 5 instantaneously flows into the buffer 2a which is a volume part.

Accordingly, the flow control valve 26 is opened by the control device 6 after time t2 (delay) after the opening / closing valve 25 is opened.
The time t2 is set in consideration of the volume of the buffer 2a, the flow resistance of the inflow pipe 21, and the like.
When the flow regulating valve 26 is opened, the pressure of the mixed gas in the buffer 2a is higher than the mixed gas pressure in the intake pipe 5 to which one end of the outflow pipe 22 communicates, so that the mixed gas in the buffer 2a enters the intake pipe 5. And leaked.
At this time, the mixed gas inflow into the intake pipe 5 is instantaneously performed rather than instantaneously, so that the amount of pressure increase in the RH and LH turbochargers 18 and 19 is suppressed, thereby suppressing the inlet manifold. The amount of the mixed gas supplied to 15 can be reduced, and the convergence of the overshoot can be accelerated.
Therefore, the flow rate adjusting valve 26 can obtain the same effect even if it is replaced with an orifice.
Further, by installing the flow rate adjusting valve 26 in the vicinity of the buffer 2a or on the buffer 2a, the distance until the mixed gas flows into the intake pipe 5 is lengthened, thereby delaying the flow of the mixed gas based on the increase in flow resistance. This is to cause

When it is detected by the rotational speed sensor 62 that the engine 1 continues to rise due to the overshoot and stops rising or descends (after t0), the control device 6 closes the on-off valve 25, Keep idling.
On the other hand, the flow rate adjusting valve 26 is closed by the control device 6 after time t3 after the opening / closing valve 25 is closed.
This is because the flow rate is adjusted by the flow rate adjusting valve 26, so that the mixed gas pressure in the buffer 2a is sufficiently lowered so that the operation of the buffer 2a is sufficiently performed when the on-off valve 25 is opened. It is to keep.

Since the operation and effects in this embodiment are the same as those in the first embodiment except for the following, they are omitted.
In the test results in the present embodiment, the mixed gas that has flowed into the buffer 2a is adjusted in flow rate by the flow rate adjusting valve 26 and also flows into the intake pipe 5 on the upstream side of the turbocharger, so that the maximum overshoot rotation is achieved. It was confirmed that there was an effect of reducing several rpm.

(Third embodiment)
The present embodiment is the same as the second embodiment except that the ignition of the mixed gas introduced into the combustion chamber 14 of the engine 1 is cut off.
Therefore, description of the structure is omitted, and only different parts are described. In this case, the same parts are denoted by the same reference numerals and description thereof is omitted.

The control device 6a for controlling the engine 1 includes an ignition cut means 65 for cutting the ignition of the mixed gas in a part of the plurality of combustion chambers 14 (making the mixed gas introduced into the combustion chambers 14 unburned). 2) is stored.
The control means 6a activates the ignition cut means 65 when the load sensor 61 as load interruption detection means detects the interruption of the engine load, and the rotation speed sensor 62 as rotation speed detection means stops the increase in the rotation speed of the engine 1. Alternatively, when it is detected that the vehicle is descending (after t0), the operation of the ignition cut means 65 is stopped.
In the present embodiment, as shown in FIG. 3 as the third embodiment, when the load fluctuates (cuts off), the load sensor 61 detects the load cut-off, and the control device 6a opens the on-off valve 25 after the load cut-off t1. To do.
The ignition cut is performed by the control device 6a at the same timing as the opening / closing valve 25 is opened.
The ignition cut timing is the same as the opening operation of the on-off valve 25, but is distinguished as t4 in order to prevent the explanation from becoming complicated.

When the on-off valve 25 is opened by the control device 6a, the pressurized mixed gas in the intake pipe 5 instantaneously flows into the buffer 2a which is a volume part.
Accordingly, the amount of mixed gas flowing to the inlet manifold 15 side is reduced, and the rotational force of the engine 1 is suppressed.
Further, the ignition cut of the combustion chamber 14 in which the amount of the mixed gas is suppressed is performed to further suppress the rotational force of the engine 1.
The combustion chamber 14 (cylinder) that performs the ignition cut is made not to continue for two or more cylinders in the normal ignition sequence of the engine 1.
This is because the combustion chamber 14 (cylinder) in which the ignition cut is performed is not continued, so that the possibility that the unburned mixed gas concentration becomes high is reduced as much as possible, so that the smoke explosion (unburned gas) in the exhaust pipe is reduced. The risk of combustion) can be suppressed.

FIG. 4 shows a comparison of the overshoot suppression effect due to the delay t4 from when the overshoot occurs until the control device 6a detects the load interruption and when the ignition cut command is issued from the control device 6a.
The implementation conditions according to the third embodiment of FIG. 4 are: change in inflow valve + volume portion + flow rate adjustment valve opening delay t2 + ignition cut command delay t4 and decrease in the number of revolutions when the number of ignition cuts (reducing cylinder) is changed. (A) shows the effect when the number of ignition cuts is 1set, (B) shows the effect when the number of ignition cuts is 2set, and (C) shows the effect when the number of ignition cuts is 3set.
The countermeasure for the rotational speed drop in FIG. 4 (A) is the condition of inflow valve + volume portion + flow rate adjusting valve opening delay t2 + ignition cut (cylinder reduction) + ignition cut command delay t4 [FIGS. 3 (A), (B) Reference].
t2 indicates a time lag from when the opening / closing valve 5 is opened to when the flow regulating valve 26 is opened.
The ignition cut command delay t4 is a time lag from the time when the overshoot occurs until the time when the control device 6a commands the ignition cut.
An ignition cut reduced cylinder 1set represents two cylinders, and each of the cylinders in the left and right banks 11 and 12 is subjected to ignition cut. This is because, in the case of this embodiment, since it is a V-type engine, rotation spots occur unless the left and right banks are equally reduced.
Therefore, the reduced cylinder 2set represents 4 cylinders, and the reduced cylinder 3set represents 6 cylinders.

In FIG. 4A, α1 has no countermeasure, and between β1 and δ1, in addition to the second embodiment, in addition to the reduced cylinder 1set (two cylinders), the delay t4 is β1 is 0 sec, γ1 is 0.2 sec, and δ1 is 0.4 sec. The measurement results are described in this order.
As a result, it can be seen that the smaller (shorter) the delay of t4, the greater the effect of suppressing the maximum overshoot speed.
This is because if the delay of t4 is small (t4; 0 sec), the ignition cut is started immediately after the overshoot is started, and the combustion of the mixed gas can be cut at an early stage, which has the effect of suppressing the maximum rotational speed. large.
On the other hand, when it is slow (t4; 0.4 sec), the ignition cut starts after the overshoot progresses, and the effect of suppressing the maximum rotational speed is small.
The convergence tendency after the maximum number of overshoot rotations has converged in a state where α to δ are kept parallel to each other indicates that the lighting cut contributes to the overshoot suppression effect.
As a result, it was found that the maximum rotational speed of overshoot was about 1% of β1 with respect to α1 in the case of volume portion + reducing cylinder (lighting cut) 1set + delay t4 (0 sec).
Further, in FIG. 4B, α2 has no countermeasure, and between β2 and δ2, in addition to the second embodiment, in addition to the reduced cylinder 2set (four cylinders), the delay t4 is β2 is 0 sec, γ2 is 0.2 sec, and δ2 is 0. Measurement results are described in the order of 4 sec.
Similar to FIG. 4 (A), FIG. 4 (B) shows that the effect of suppressing the maximum overshoot speed is larger as the delay of t4 is smaller (shorter), and the number of reduced cylinders (ignition cut) is larger. It turns out that the effect which suppresses the maximum number of rotations of an overshoot is large as it becomes (the width | variety of the number of rotations is large).
Also, in FIG. 4 (C), α3 has no countermeasures, and between β3 and δ3, the reduction cylinder 3set (6 cylinders), the delay t4, β3 is 0 sec, γ3 is 0.2 sec, and δ3 is 0.4 sec. It is described.
This will be described with reference to FIG. 4C, in which the effect of suppressing the maximum number of overshoots is significant.
With respect to α3 without cylinder reduction, δ3 has an effect of suppressing the rotational speed from a position of 400 msec (time tms), γ3 has an effect of suppressing the rotational speed from a position of 200 msec (time tms), and β3 has an effect of suppressing the rotational speed of 0 msec (time tms). It can be seen that the effect of suppressing the rotational speed appears from the position of).
It can be seen that the smaller (shorter) the delay of t4 is, the greater the effect of suppressing the maximum overshoot speed is.
As a result, it was found that the maximum number of overshoot rotations was about 3.3% of α3 with respect to α3 when the volume portion + reducing cylinder (lighting cut) 1set + delay t4 (0 sec).

  By adopting such a structure, the cut combustion chamber 14 (cylinder) is engine braked by cutting the ignition of the mixed gas at an early stage in a part of the plurality of combustion chambers provided in the engine 1. Due to the effect (rotational resistance due to the load compressing the mixed gas in the cylinder), the increase in rotation can be effectively suppressed.

(Fourth embodiment)
This embodiment is the same as the second embodiment (buffer bypass) except that the ignition timing of the mixed gas introduced into the combustion chamber 14 of the engine 1 is changed.
Therefore, description of the structure is omitted, and only different parts are described. In this case, the same parts are denoted by the same reference numerals and description thereof is omitted.

The combustion chamber 14 of the engine 1 is provided with a retard means 66 that delays the ignition timing of the mixed gas whose amount of mixed gas is suppressed (the amount of mixed gas flowing into the buffer 2).
The retard means 66 is accommodated in the control device 6a.
When the load sensor 61 serving as the load shut-off detecting means detects the load shut-off, the retard means 66 is operated, and the rotational speed sensor 62 serving as the rotational speed detecting means stops or lowers (after t0) the rotational speed of the engine 1. When it is detected that the retarding device 66 is operating, the operation of the retard means 66 is stopped.
In this embodiment, as shown in FIG. 3, when the load fluctuates (shuts off), the load sensor 61 detects the load shut-off, and the control device 6 is implemented by the retard means 66 built in the control device 6 after t1. The

FIG. 5 shows a result when the maximum overshoot speed at the time of load interruption is suppressed in the present embodiment.
The countermeasure for suppressing the maximum overshoot speed of the present embodiment was implemented under the conditions of inflow valve + volume part volume part + regulator valve (volume part bypass delay t2) + retard [see FIGS. 3A and 3B]. It is a result.
According to this result, in the case of retard B, a reduction effect of about 10 rpm was obtained.
However, the retard has a delay angle A <B.
As can be seen from FIG. 5, the larger the retard amount, the better. However, if it is too large, abnormal combustion or misfire may be caused, and the value must be determined by the engine.

By retarding the ignition timing of the mixed gas with respect to the normal driving character, the combustion efficiency of the mixed gas is lowered, and the conversion efficiency of the combustion energy into motive energy is lowered.
Therefore, it is possible to suppress the maximum overshoot speed at the time of load interruption by reducing the effect of the rotation increase by reducing the conversion to motive energy.

  It can be provided as an intake air circulation device for an internal combustion engine that reduces a so-called overshoot amount in which the rotation speed rapidly increases when a load is interrupted that has been applied during operation of the internal combustion engine.

1 engine (internal combustion engine)
2, 2a buffer (volume part)
DESCRIPTION OF SYMBOLS 3 Air cleaner 5 Intake pipe 6, 6a Control apparatus 7 Mixing apparatus 8 Exhaust gas processing apparatus 15 Inlet manifold 16 RH exhaust manifold 17 LH exhaust manifold 18 RH turbocharger 19 LH turbocharger 21 Inflow pipe 22 Outflow pipe 25 On-off valve (open / close valve)
26 Flow control valve 51 Throttle valve 52 Intercooler 61 Load sensor (load cutoff detection means)
62 Rotational speed sensor (Rotational speed detection means)
65 ignition cut means 66 retard means

Claims (7)

An internal combustion engine, and an air cleaner for purifying air to the internal combustion engine;
An intake pipe connecting the internal combustion engine and the air cleaner;
A mixing device that mixes fuel gas with the air flowing through the intake pipe to generate a mixed gas;
A turbocharger for pressurizing the mixed gas generated by the mixing device ;
An intercooler that cools the mixed gas pressurized by the turbocharger ,
The mixing device, the turbocharger, and the intercooler are provided in order from the upstream side of the intake pipe,
Furthermore, a volume provided through an inflow pipe connected between the intercooler and the internal combustion engine,
An on-off valve provided in the inflow pipe;
Load interruption detection means for detecting that the load acting on the internal combustion engine has been interrupted;
A rotational speed detection means for detecting the rotational speed of the internal combustion engine;
A control device for controlling the opening and closing operation of the on-off valve,
When the load shut-off detection means detects a load shut-off, the controller opens the on-off valve to cause a part of the mixed gas flowing through the intake pipe to flow into the volume portion, and the rotational speed An intake air circulation device for an internal combustion engine, wherein when the detecting means detects that the increase in the rotational speed of the internal combustion engine has stopped or is decreasing, the on-off valve is closed. An outflow pipe having one end communicating with the volume portion and the other end communicating between the mixing device and the turbocharger, and a flow rate adjusting valve interposed in the outflow pipe,
The flow rate adjusting valve is opened by the control device with a delay from the opening operation time of the opening / closing valve, and the mixed gas in the volume part is returned to the upstream side of the turbocharger of the intake pipe. 2. An intake-air circulating apparatus for an internal combustion engine according to claim 1, wherein the intake-air circulating apparatus is closed when it is detected that the engine speed has stopped increasing or is decreasing.   The intake air circulation device for an internal combustion engine according to claim 1 or 2, wherein the volume of the volume portion is approximately ¼ of the volume of the intake manifold.   The intake circulation device for an internal combustion engine according to claim 2 or 3, wherein the attachment position of the flow rate adjusting valve is disposed in the volume portion or the outflow pipe close to the volume portion.   In some of the plurality of combustion chambers provided in the internal combustion engine, ignition cut means for cutting off the ignition of the mixed gas is provided, and the ignition cut means is provided when the load cut-off detecting means detects load cut-off. The operation of the ignition cut means is stopped when the engine speed is detected and the engine speed detecting means detects that the engine speed of the internal combustion engine has stopped increasing or decreased. An intake air circulation device for an internal combustion engine according to any one of the above.   6. An intake air circulation system for an internal combustion engine according to claim 5, wherein the combustion chamber for carrying out the ignition cut is not continued for two or more cylinders in an ignition order during normal operation of the internal combustion engine. The internal combustion engine is provided with a retard means for retarding the ignition timing of the mixed gas with respect to a normal operation, and the retard means is operated when the load shut-off detecting means detects a load shut-off. 5. The intake air circulation device for an internal combustion engine according to claim 1, wherein the retard means stops operating when it is detected that the increase in the rotational speed of the internal combustion engine is stopped or is decreasing. 6. .

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