JP4207160B2 - Knocking control device for gas fuel direct injection engine - Google Patents

Description

  The present invention relates to a knock control device for a gas fuel direct injection engine including a direct injection injector and a spark plug provided facing a combustion chamber, and a knocking detection means for detecting or estimating the occurrence of knocking.

  Conventionally, a so-called gas fuel engine that uses compressed natural gas (hereinafter referred to as CNG) or hydrogen gas as a fuel has been developed. In this gas fuel engine, it has been proposed to control the injection timing of the gas fuel into the combustion chamber based on the engine operation region in order to control the combustion of the gas fuel in the combustion chamber and improve the fuel efficiency. Yes.

  For example, Patent Document 1 states that in a gas fuel engine, gas fuel is injected at the end of the compression stroke in the low load operation region, and gas fuel is injected at the beginning of the compression stroke or in the intake stroke in the high load operation region. ing.

JP 2004-076686 A

  By the way, for example, CNG has a high octane number and is superior to gasoline in terms of anti-knock properties, but if a high compression ratio or the like is employed, the possibility of knocking increases. Therefore, when a high compression ratio or the like is employed, generally, ignition timing retardation control that retards the ignition timing from the optimum timing is employed as knock control control. However, when the ignition timing retarding control is applied with the technique described in Patent Document 1, the combustion pressure is lowered, and the performance of the gas fuel engine is deteriorated.

  Therefore, an object of the present invention is to provide a knocking control device for a gas fuel direct injection engine that makes it possible to avoid knocking without reducing the performance of the gas fuel engine.

A knocking control device for a gas fuel direct injection engine according to an aspect of the present invention that achieves the above object includes a direct injection injector and a spark plug that are provided facing a combustion chamber, and a knocking detection unit that detects or estimates the occurrence of knocking. A knock control apparatus for a gas fuel direct injection engine comprising: a gas fuel injection pressure that is set to be higher than a normal injection pressure when knocking is detected or estimated by the knock detection means. The high injection pressure setting means is provided in addition to the low pressure gas fuel line for supplying the normal injection pressure gas fuel to the direct injection injector, and the high injection pressure setting means has a pressure higher than the normal injection pressure. The high-pressure gas fuel line, the low-pressure gas fuel line, and the high-pressure gas fuel line for supplying the fuel to the direct injection injector And means changed, the switching means, when the occurrence of knocking is detected or estimated by the knocking detecting means, and switches the high pressure gas fuel line so that the high-pressure gas fuel is injected from the direct injector.

Here, the low-pressure gas fuel line is a normal low-pressure gas fuel line that decompresses the high-pressure gas fuel in the fuel tank with a regulator and supplies it to each injector via a delivery pipe . The high-pressure gas fuel line is a low- pressure gas fuel line. A high-pressure gas fuel line provided in addition to the line and bypassing the regulator is preferable.

Alternatively, the low-pressure gas fuel line is a normal low-pressure gas fuel line in which the high- pressure gas fuel in the fuel tank is decompressed by a regulator and supplied to each injector via a delivery pipe . The high-pressure gas fuel line is a low-pressure gas fuel line. In addition, the high-pressure gas fuel line is preferably provided, and is branched from the downstream side of the regulator and provided with a pressurizing means.

Further, when knocking detection is detected or estimated by the knocking detection means , the maximum retarded-angle injection that is permitted in order to allow the turbulence of the gas fuel injection end timing from the direct injection injector to be generated near the spark plug. It is preferable to retard the gas fuel injection timing as the end timing .

  Further, when the occurrence of knocking is detected or estimated by the knocking detection means, if the gas fuel pressure in the fuel tank is lower than a predetermined value, the ignition timing by the spark plug is set without operating the high injection pressure setting means. It is desirable to perform retarded ignition timing retard control.

According to one aspect of the present invention, there is provided a knocking control device for a gas fuel direct injection engine comprising a direct injection injector and a spark plug provided facing a combustion chamber, and knocking detection means for detecting or estimating the occurrence of knocking. When the occurrence of knocking is detected or estimated by the knocking detection means, the fuel injection pressure setting means for setting the gas fuel injection pressure from the direct injection injector higher than the normal injection pressure, the high injection pressure setting means, A high-pressure gas fuel line, which is provided in addition to a low-pressure gas fuel line for supplying gas fuel having a normal injection pressure to the direct injection injector, and for supplying a high-pressure gas fuel having a pressure higher than the normal injection pressure to the direct injection injector; , A switching means for switching between the low pressure gas fuel line and the high pressure gas fuel line, the switching means by the knocking detection means When the evolution of Kkingu is detected or estimated, because the switching to the high-pressure gas fuel line so that the high-pressure gas fuel is injected from the direct injector, when the occurrence of knocking is detected or estimated, gas fuel combustion chamber at high pressure It is possible to generate a large turbulence in the combustion chamber. As a result, the natural ignition in the combustion chamber is suppressed without deteriorating the performance of the gas fuel engine, and knocking can be avoided.

The low-pressure gas fuel line is a normal low-pressure gas fuel line that decompresses the high-pressure gas fuel in the fuel tank with a regulator and supplies it to each injector via a delivery pipe . The high-pressure gas fuel line is a low-pressure gas fuel line. Additionally provided, according to the a high pressure gas fuel line that bypasses the regulator, when the occurrence of knocking is detected or estimated by switching the high pressure gas fuel line, a high pressure of fuel gas in the fuel tank combustion Since it is injected into the chamber, knocking can be reliably avoided with a simple configuration without requiring any special pressurizing means.

Alternatively, the low-pressure gas fuel line is a normal low-pressure gas fuel line in which the high- pressure gas fuel in the fuel tank is decompressed by a regulator and supplied to each injector via a delivery pipe . The high-pressure gas fuel line is a low-pressure gas fuel line. Additionally provided, is branched from the downstream of the regulator, according to a high pressure gas fuel line pressure means is disposed, once since decompressed gas fuel can be pressurized by pressurizing means, fuel Regardless of the pressure of the gas fuel in the tank, when the occurrence of knocking is detected or estimated, high-pressure gas fuel is injected into the combustion chamber, so that knocking can be reliably avoided.

Further, when knocking detection is detected or estimated by the knocking detection means , the maximum retarded-angle injection that is permitted in order to allow the turbulence of the gas fuel injection end timing from the direct injection injector to be generated near the spark plug. According to the form of retarding the injection timing of the gas fuel at the end timing, the high-pressure gas fuel injected at the retarded injection timing generates a strong turbulence near the spark plug, and ignition is performed in that state. The occurrence of knocking can be avoided more reliably.

  Further, when the occurrence of knocking is detected or estimated by the knocking detection means, if the gas fuel pressure in the fuel tank is lower than a predetermined value, the ignition timing by the spark plug is set without operating the high injection pressure setting means. According to the form of performing retarded ignition timing retard control, control for avoiding knocking can be reliably performed even when it is difficult to inject high-pressure gas fuel.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
First, based on FIG.1 and FIG.2, 1st embodiment of the knock control apparatus of the gas fuel direct injection engine which concerns on this invention is described. FIG. 1 is a schematic diagram for explaining the knock control device 101 of the gas fuel direct injection engine of the first embodiment, and FIG. 2 controls the knock control device 101 of the gas fuel direct injection engine in FIG. It is an example of the flowchart for this.

  The intake port of the engine 1 is connected to the intake manifold 2, and the exhaust port of the engine 1 is connected to the exhaust manifold 5. The engine 1 in FIG. 1 includes a gas fuel supply system 3 that uses CNG as gas fuel. This gas fuel supply system 3 is connected via a delivery pipe 4 to a CNG direct injection injector 41 serving as a direct injection injector for gas fuel disposed in a cylinder combustion chamber 11 so as to be able to be injected via an injection port. . The engine 1 is provided with a knock sensor 1a as a knocking detecting means for detecting high-frequency vibration caused by knocking transmitted to the cylinder block. Further, in the engine 1, the piston cavity 12 adapted to the injection direction from the CNG direct injection injector 41 is formed offset to the intake port side, and a pressure sensor for detecting the gas fuel injection pressure of this gas fuel 4 a is arranged in the delivery pipe 4. In addition, an ignition plug 13 is disposed in the upper center of each combustion chamber 11.

  A fuel tank 31 as a gas fuel container mounted on the vehicle is connected to a high-pressure gas fuel delivery line 32. The high-pressure gas fuel delivery line 32 is connected to the delivery pipe 4 via a regulator 3 b that decompresses the high-pressure gas fuel in the fuel tank 31 to make low-pressure gas fuel and a low-pressure gas fuel line 33. In the high pressure gas fuel delivery line 32, a pressure sensor 3a for detecting the gas fuel pressure of the high pressure gas fuel in the fuel tank 31 and a switching control as to whether or not the low pressure gas fuel flows through the low pressure gas fuel line 33 will be described later. The shut-off valve 3X for performing the above is arranged, and the regulator 3b is connected downstream thereof. And the check valve 3c which prevents the back flow of low pressure gas fuel is arrange | positioned at the low pressure gas fuel line 33 connected downstream of the regulator 3b. The shut-off valve 3X is controllable based on an output signal from the ECU 300 described later. Here, the gas fuel decompressed by the regulator 3b is referred to as a low pressure gas fuel, and a high pressure gas fuel in the fuel tank 31 or the like is referred to as a high pressure gas fuel.

  On the other hand, the high-pressure gas fuel line 34 is branched from the high-pressure gas fuel delivery line 32, more specifically, from a branch point J downstream of the pressure sensor 3a and upstream of the shutoff valve 3X. The high pressure gas fuel line 34 is further joined to the low pressure gas fuel line 33 downstream of the check valve 3c. That is, the high-pressure gas fuel line 34 is provided in parallel to the low-pressure gas fuel line 33 so as to bypass the regulator 3b, and allows the high-pressure gas fuel from the fuel tank 31 to flow through the delivery pipe 4 as it is. A flow path is formed. In the high-pressure gas fuel line 34 downstream of the branch point J, a shut-off valve 3Y for performing switching control as to whether or not to flow high-pressure gas fuel is disposed. The shut-off valve 3Y is controllable based on an output signal from the ECU 300 described later, and is the same as the shut-off valve 3X described above.

  The high-pressure gas fuel filled in the fuel tank 31 with a filling pressure (for example, 20 MPa) is decompressed to a certain high regulation pressure (for example, 5 MPa) by the regulator 3b to be a low-pressure gas fuel. Therefore, it is injected from the CNG direct injection injector 41 into the combustion chamber 11 in, for example, a compression stroke. This high regulation pressure is a pressure that enables in-cylinder injection in the compression stroke, regardless of the operating state. The CNG direct injection injector 41 can be controlled based on an output signal from the ECU 300 described later.

  In addition to the shutoff valves 3X and 3Y, the knock control device 101 for the gas fuel direct injection engine according to the present invention includes an electronic control unit (ECU) 300 that performs basic control such as control of the CNG direct injection injector 41. ing. The ECU 300 includes, for example, a microcomputer including a CPU, a memory for recording various programs and data, an input interface circuit, and an output interface circuit. The input interface circuit includes a knock sensor 1a for detecting high-frequency vibration caused by knocking transmitted to the cylinder block, a pressure sensor 3a for detecting the gas fuel pressure of the high-pressure gas fuel in the fuel tank 31, and an injection from the CNG direct injection injector 41. A pressure sensor 4a that detects the gas fuel injection pressure of the gas fuel, and a load sensor 301 and a rotation speed sensor 302 that are means for detecting the operating state of the engine such as the engine speed and load are connected via electrical wiring. ing. The output interface circuit of the ECU 300 is connected to the step motors SM1 and SM2 for driving which can open and close the shut-off valves 3X and 3Y, and the opening and closing thereof is controlled based on data obtained by these various sensors. Has been made possible.

  Next, an example of the control of the knocking control device 101 of the gas fuel direct injection engine having the above configuration will be described with reference to the flowchart of FIG. The control routine of FIG. 2 is a routine that is executed every predetermined time.

  In the knock control device 101 of the gas fuel direct injection engine having the above-described configuration, the low pressure gas fuel 33 is usually supplied via the low pressure gas fuel line 33 in a state where combustion is normally performed without causing knocking. The low pressure gas fuel is injected from the CNG direct injection injector 41. That is, the shutoff valve 3X is opened to flow the low pressure gas fuel to the low pressure gas fuel line 33, while the shutoff valve 3Y is closed to shut off the high pressure gas fuel to the high pressure gas fuel line 34.

  When the control starts, it is determined in step S201 whether or not knocking has occurred in order to check whether or not control is performed to avoid knocking. That is, the knock sensor 1a detects high-frequency vibration due to knocking. For example, when the knocking sensor 1a exceeds a certain threshold, it is determined that knocking has occurred, and the process proceeds to step S202. Note that whether or not knocking has occurred may be detected or estimated by other means such as an in-cylinder pressure sensor. Alternatively, the following control may be performed by estimating the occurrence of knocking in advance before the occurrence of knocking.

  In step S202, as means for avoiding knocking, control is performed to set the gas fuel injection pressure higher than the normal injection pressure, and ignition is performed to change the ignition timing to the retard side as has been conventionally done. In order to check which of the timing retard control is to be selected, it is determined whether or not the pressure in the fuel tank 31 is higher than a predetermined pressure. That is, in the first embodiment, when the pressure in the fuel tank 31 is higher than a predetermined pressure and the high-pressure gas fuel can be injected from the CNG direct injection injector 41, the gas fuel injection pressure is set higher than the normal injection pressure. Control is selected, otherwise ignition timing retard control is selected to avoid knocking. Here, it is determined whether or not the gas fuel pressure of the high-pressure gas fuel detected by the pressure sensor 3a is higher than a predetermined pressure of 10 MPa, for example. If it is determined that the result is higher than 10 MPa, the process proceeds to step S203. When the pressure in the fuel tank 31 is not higher than the predetermined pressure, the process proceeds to step S214, and ignition timing retardation control is performed.

  In step S203, the shut-off valve 3Y is opened to flow the high-pressure gas fuel to the high-pressure gas fuel line 34. Next, in step S204, the shut-off valve 3X is closed to shut off the flow path of the low-pressure gas fuel. As a result, the low-pressure gas fuel line 33 and the high-pressure gas fuel line 34 are switched, and the high-pressure gas fuel is allowed to flow through the high-pressure gas fuel line 34 so that the high-pressure gas fuel can be injected from the CNG direct injection injector 41.

  Next, in step S205, the injection end time is extracted from the limit injection end time map that is obtained and stored in advance through experiments. Specifically, the injection end time is obtained by searching a limit injection end time map based on the engine load and the rotation speed detected by the load sensor 301 and the rotation speed sensor 302. The term “limit injection end timing” as used herein refers to the maximum retarded injection end timing that is allowed in order to ensure that a turbulence can be reliably generated in the vicinity of the spark plug 13 when retarded injection is performed. The limit injection end timing map may be created in consideration of not only the engine load and the rotational speed but also the gas fuel pressure or the gas fuel injection pressure.

  Next, in step S206, the injection start timing is extracted from the engine load and rotation speed at that time and the gas fuel injection pressure. More specifically, the fuel injection amount required corresponding to the operating state is obtained from the engine load and the rotation speed detected in step S205 by searching map data stored in advance by experiments. It is done. Then, based on the fuel injection amount and the gas fuel injection pressure obtained by the pressure sensor 4a, the fuel injection period is obtained by searching the data that has been obtained in advance by experiments and stored, and the injection that has already been extracted is completed. The injection start time is determined from the relationship with the time. In determining the fuel injection period, the gas fuel injection pressure is used in the first embodiment. However, for example, the fuel temperature of the high-pressure gas fuel may also be used.

  As described above, when the injection start timing and the injection end timing are obtained, high-pressure gas fuel is injected from the CNG direct injection injector 41 according to these timings, and is ignited from the spark plug 13 so that the combustion in the combustion chamber 11 is performed. Will be done. By the way, since such control is performed to avoid knocking, in order to confirm whether knocking has been avoided or not, knocking is not performed in the same step S207 as in step S201. It is determined whether or not it has occurred. When it is determined that knocking has not occurred, that is, knocking has been avoided, the process proceeds to step S208 to return to normal control.

  That is, in order to return to the normal control state, the shut-off valve 3X is first opened so that the low-pressure gas fuel flows in step S208, and the shut-off valve 3Y is closed so that the high-pressure gas fuel is shut off in step S209. As a result, the injection control is returned to the normal injection pressure (for example, 5 MPa) corresponding to the gas fuel pressure of the low-pressure gas fuel, and the combustion in the combustion chamber 11 is performed using the low-pressure gas fuel. Such control switching is performed immediately when it is determined that knocking can be avoided, so that even when the operating state of the engine suddenly changes, it is possible to appropriately perform the corresponding combustion control. Become.

  On the other hand, control is switched as described above to avoid knocking. However, when it is determined in step S207 that knocking has occurred, that is, when it is determined that knocking has not been avoided, the process proceeds to step S210. .

  In step S210, it is determined whether or not the high-pressure injection period during which combustion control is performed by increasing the gas fuel injection pressure has passed to determine whether knocking can be avoided by the above control. Specifically, it is determined whether or not the high-pressure injection period started by a timer device (not shown) started by an open signal to the shut-off valve 3Y exceeds a predetermined period. Returning, Steps S205 to S207 and Step S210 are repeated again. When the high pressure injection period exceeds the predetermined period, it is determined that knocking could not be avoided even by the high injection pressure control, and the process proceeds to the next step S211. At this time, the high-pressure injection period being measured by the timer device is reset to “0”.

  In step S211, switching control to ignition timing retardation control is performed in order to avoid knocking. Then, the shutoff valve 3X is opened in step S212 and the shutoff valve 3Y is closed in step S213 so that the ignition timing retardation control is performed and the high injection pressure control is stopped. Note that steps S211 to S213 are performed almost simultaneously, and the switching to the ignition timing retardation control is performed smoothly. Although it has been described that the ignition timing retarding control is performed in steps S214 and S211, if knocking is avoided by this control, the control is returned to the normal optimal ignition timing.

  According to the first embodiment described above, the knocking control device 101 for the gas fuel direct injection engine is configured to set the gas fuel injection pressure from the CNG direct injection injector 41 higher than the normal injection pressure. It has. The high injection pressure setting means decompresses the high-pressure gas fuel in the fuel tank 31 by the regulator 3 b and adds to the normal low-pressure gas fuel line 33 that supplies the CNG direct injection injectors 41 via the delivery pipe 4. Since it is provided with a high-pressure gas fuel line 34 that bypasses the regulator 3b and shut-off valves 3X and 3Y as switching means for switching between the low-pressure gas fuel line 33 and the high-pressure gas fuel line 34, occurrence of knocking is detected In principle, the high-pressure gas fuel is directly injected into the combustion chamber 11. A large turbulence is generated in the combustion chamber 11. In particular, since the gas fuel is injected at a retarded angle, ignition is performed in a state where a large turbulence is generated in the vicinity of the spark plug 13 in the combustion chamber 11, and as a result, for example, before the piston reaches the top dead center, the gas fuel Therefore, the performance of the gas fuel direct injection engine is not deteriorated by the control for avoiding knocking. In addition, spontaneous ignition in the combustion chamber, particularly in the vicinity of the spark plug, is suppressed, and knocking can be avoided. Furthermore, according to such a configuration, only a parallel flow path and electromagnetically controllable shut-off valves 3X and 3Y are provided to perform control for switching between high-pressure gas fuel and low-pressure gas fuel. Can be avoided.

  Next, a second embodiment of the knock control device for a gas fuel direct injection engine according to the present invention will be described with reference to FIGS. FIG. 3 is a schematic diagram for explaining the knock control device 102 of the gas fuel direct injection engine of the second embodiment, and FIG. 4 controls the knock control device 102 of the gas fuel direct injection engine in FIG. It is an example of the flowchart for this. In order to facilitate understanding of the description, the same components as those in the first embodiment are denoted by the same reference numerals as much as possible to avoid redundant description.

  The second embodiment is different from the first embodiment in that the high-pressure gas fuel from the fuel tank 31 is all decompressed via the regulator 3b. Instead, in the second embodiment, a branch is made from the low pressure gas fuel line 33 downstream of the regulator 3b, and then the check valve 3c of the low pressure gas fuel line 33 is bypassed and joined to the low pressure gas fuel line 33. The high-pressure gas fuel line 35 is provided, and the compressor 3Z is provided to increase the pressure of the low-pressure gas fuel. In the high pressure gas fuel line 35 downstream of the compressor 3Z, a surge tank 3d, a pressure sensor 3e, and a shutoff valve 3Y are further arranged in this order. The surge tank 3d is provided to suppress the pulsation of the gas fuel that has been pressurized by the compressor 3Z, and the pressure sensor 3e is provided so that the pressure of the gas fuel pressurized by the compressor 3Z can be detected. The compressor 3Z is driven by a motor. The high pressure gas fuel delivery line 32 is only provided with a pressure sensor 3a in the vicinity of the fuel tank 31.

  Next, an example of the control of the knocking control device 102 of the gas fuel direct injection engine of the second embodiment will be described with reference to the flowchart of FIG. The control routine of FIG. 4 is a routine that is executed every predetermined time. Note that steps S405 to S413 in the flowchart in FIG. 4 correspond to steps S201, S203, S205 to S207, steps S209 to S211 and S213 in the flowchart in FIG. 2 in the previous embodiment. These descriptions are omitted.

  In the knock control device 102 of the gas fuel direct injection engine having the above-described configuration, the low pressure gas fuel is sent to the delivery pipe 4 via the low pressure gas fuel line 33 in a state where the combustion is normally performed without knocking. Thus, the low pressure gas fuel is injected from the CNG direct injection injector 41. That is, the shutoff valve 3Y is closed to shut off the flow of the high pressure gas fuel pressurized by the compressor 3Z from the high pressure gas fuel line 35 to the low pressure gas fuel line 33.

  When the control starts, first, in step S401, it is determined whether or not the internal pressure of the surge tank 3d is higher than the lower limit predetermined pressure in order to check whether the gas fuel in the high pressure gas fuel line 35 is high pressure gas fuel. In the second embodiment, for example, the pressure of the low-pressure gas fuel is approximately 5 MPa, while the lower limit predetermined pressure is set to a pressure higher than that, for example, 10 MPa. When it is determined that the internal pressure of the surge tank 3d detected by the pressure sensor 3e, that is, the pressure of the gas fuel pressurized by the compressor 3Z is 10 MPa or less, the process proceeds to step S402 and the compressor 3Z is turned on. Thereby, the gas fuel in the high-pressure gas fuel line 35 is pressurized to become high-pressure gas fuel.

  Next, in step S403, it is determined whether or not the internal pressure of the surge tank 3d is higher than the target predetermined pressure in order to stop the compressor 3Z. In the second embodiment, the target predetermined pressure is set to 20 MPa, for example, and it is determined whether or not the internal pressure of the surge tank 3d detected by the pressure sensor 3e is higher than 20 MPa. Steps S402 and S403 are repeated until it is determined that the internal pressure of the surge tank 3d is higher than 20 MPa. As a result, when it is determined that the internal pressure of the surge tank 3d is higher than 20 MPa, the compressor 3Z is turned off in step S404. Thereafter, the process proceeds to step S405, and the control is performed as described above. The lower limit predetermined pressure and the target predetermined pressure are different from each other, but may be the same pressure.

  According to the second embodiment described above, as the high injection pressure setting means, the high pressure gas fuel in the fuel tank 31 is normally decompressed by the regulator 3b and supplied to each CNG direct injection injector 41 via the delivery pipe 4. In addition to the low pressure gas fuel line 33, a high pressure gas fuel line 35 branched from the downstream of the regulator 3b and provided with the compressor 3Z, and a shutoff valve 3Y for switching between the low pressure gas fuel line 33 and the high pressure gas fuel line 35, Is provided. Thereby, first, the low pressure gas fuel decompressed by the regulator 3b in advance is boosted by the compressor 3Z to become high pressure gas fuel. When the occurrence of knocking is detected or estimated regardless of the pressure of the gas fuel in the fuel tank 31, the high-pressure gas fuel is sent to the delivery pipe 4 via the high-pressure gas fuel line 35, and the CNG direct injection injector 41. Will be injected into the combustion chamber 11. As a result, it is possible to reliably avoid knocking as in the first embodiment. In particular, since fuel is injected at a retarded angle, ignition is performed in a state where a large turbulence is generated in the vicinity of the spark plug 13 in the combustion chamber 11, and knocking can be further avoided.

It is the schematic for demonstrating the knocking control apparatus of the gas fuel direct injection engine of 1st embodiment. It is an example of the flowchart for controlling the knock control apparatus of the gas fuel direct injection engine in FIG. It is the schematic for demonstrating the knocking control apparatus of the gas fuel direct injection engine of 2nd embodiment. It is an example of the flowchart for controlling the knock control apparatus of the gas fuel direct injection engine in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine body 11 Combustion chamber 12 Piston cavity 13 Spark plug 2 Intake manifold 21 Fuel passage 3 Gas fuel supply system 31 Fuel tank 32 High pressure gas fuel delivery line 33 Low pressure gas fuel line 34, 35 High pressure gas fuel line 3a Pressure sensor 3b Regulator 3c Check valve 3d Surge tank 3e Pressure sensor 3X Shut-off valve 3Y Shut-off valve 3Z Compressor 4 Delivery pipe 41 CNG direct injection injector 5 Exhaust manifold 300 ECU

Claims (5)

A knocking control device for a gas fuel direct injection engine comprising a direct injection injector and a spark plug provided facing a combustion chamber, and a knocking detection means for detecting or estimating the occurrence of knocking,
A high injection pressure setting means for setting a gas fuel injection pressure from the direct injection injector higher than a normal injection pressure when occurrence of knocking is detected or estimated by the knocking detection means ;
The high injection pressure setting means includes
A high-pressure gas provided in addition to the low-pressure gas fuel line for supplying gas fuel of normal injection pressure to the direct injection injector, and for supplying high-pressure gas fuel of pressure higher than the normal injection pressure to the direct injection injector A fuel line;
Switching means for switching between the low pressure gas fuel line and the high pressure gas fuel line;
With
The switching means switches to the high-pressure gas fuel line so that the high-pressure gas fuel is injected from the direct injection injector when occurrence of knocking is detected or estimated by the knocking detection means. Knocking control device for direct injection engine. The low-pressure gas fuel line is a normal low-pressure gas fuel line that depressurizes the high-pressure gas fuel in the fuel tank by a regulator and supplies it to each injector through a delivery pipe ,
The high pressure gas fuel line is provided in addition to the low-pressure gas fuel line, knock control device for a gas fuel direct injection engine according to claim 1, characterized in that the high pressure gas fuel line that bypasses the regulator. The low-pressure gas fuel line is a normal low-pressure gas fuel line that depressurizes the high-pressure gas fuel in the fuel tank by a regulator and supplies it to each injector through a delivery pipe ,
The high pressure gas fuel line is provided in addition to the low-pressure gas fuel line is branched from the downstream of the regulator, according to claim 1, wherein the pressurizing means is a high pressure gas fuel line disposed Gas fuel direct injection engine knock control device. When the occurrence of knocking is detected or estimated by the knocking detection means, the maximum delay angle that is allowed in order to allow the turbulence of the gas fuel injection end timing from the direct injection injector to be generated in the vicinity of the spark plug. 4. The knock control apparatus for a gas fuel direct injection engine according to claim 1 , wherein the injection timing of the gas fuel is retarded as the injection end timing .   When the occurrence of knocking is detected or estimated by the knocking detection means, if the gas fuel pressure in the fuel tank is lower than a predetermined value, the ignition timing by the ignition plug is not operated without operating the high injection pressure setting means. 4. The knock control apparatus for a gas fuel direct injection engine according to any one of claims 1 to 3, wherein ignition timing retarding control is performed to retard the ignition timing.

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