JP7235401B2 - injection system - Google Patents

Description

The present invention relates to an injection system mounted on a vehicle for injecting a liquid material into an exhaust passage of an internal combustion engine.

Injection systems are known for injecting liquid material into the exhaust passage of an internal combustion engine of a vehicle. For example, Patent Literature 1 discloses a method for forcibly burning PM accumulated in a particulate filter for collecting particulate matter (hereinafter also referred to as "PM") contained in exhaust gas of an internal combustion engine. discloses a technique of injecting fuel into an exhaust passage further upstream of an oxidation catalyst disposed upstream of a particulate filter to raise the temperature of the exhaust gas. In the fuel injection system described in Patent Document 1, the flow rate of fuel supplied to an injection valve attached to an exhaust pipe is controlled, and when the pressure of the fuel exceeds the valve opening pressure of the injection valve, the injection valve opens. and fuel is injected.

Further, in Patent Document 2, in order to purify nitrogen oxides (hereinafter also referred to as " _NOx ") contained in the exhaust gas of an internal combustion engine, a liquid reducing agent is introduced into an exhaust passage on the upstream side of a reduction catalyst. is disclosed to supply the reducing agent to the reduction catalyst. In the reducing agent injection system described in Patent Document 2, fuel is injected by controlling the opening and closing of an electronically controlled injection valve attached to an exhaust pipe.

JP 2018-135868 A JP 2018-127960 A

Here, in the injection system described above, exhaust heat is transferred directly or via an exhaust pipe to the injection valve during operation of the internal combustion engine to heat the injection valve. In the fuel injection system disclosed in Patent Literature 1, if the injection valve is heated while fuel injection is stopped, the fuel may deteriorate inside the injection valve or in a fuel pipe in the vicinity thereof. If the fuel deteriorates, the valve body may be damaged and the operation of the injection valve may be hindered. In the reducing agent injection system described in Patent Document 2, if the injection valve is heated while the injection of the reducing agent is stopped, the reducing agent may crystallize or the electronically controlled injection valve may be damaged. There is a risk of

In contrast, there are injection systems with cooling devices for cooling the injection valves. For example, the temperature rise of the injection valve is suppressed by holding the injection valve in a cooling holder having a cooling chamber through which engine cooling water can flow, and circulating the cooling water in the cooling chamber. However, immediately after the internal combustion engine stops, circulation of cooling water in the engine stops even though exhaust heat remains, so the injection valve is likely to be exposed to high temperatures.

SUMMARY OF THE INVENTION An object of the present invention is to provide an injection system capable of suppressing an increase in the temperature of an injection valve.

According to one aspect of the present invention, an injection system includes an injection valve that injects a liquid material into an exhaust passage of an internal combustion engine of a vehicle, a cooling device that cools the injection valve, and a cooling control section that controls the cooling device. The cooling device has a cooling chamber through which a cooling medium passes, a cooling holder that holds an injection valve, and a cooling water circuit of an internal combustion engine that has a pump and a radiator. An introduction passage for introducing the cooling medium into the cooling chamber, an extraction passage for extracting the cooling medium from the cooling chamber and joining the cooling water circuit on the upstream side of the pump, and connecting the introduction passage and the extraction passage to bypass the pump and the radiator. and a cooling water circulating pump provided in the bypass passage, and the cooling control unit controls the temperature in the exhaust passage to reach a preset start threshold when the internal combustion engine is stopped and the driving of the pump is stopped. An injection system is provided that drives the cooling water circulation pump when it exceeds and terminates driving the cooling water circulation pump when a predetermined termination condition is met.

ADVANTAGE OF THE INVENTION According to this invention, the temperature rise of an injection valve can be suppressed.

1 is a schematic diagram showing a configuration example of an exhaust purification system using a fuel injection system according to an embodiment of the present invention; FIG. It is a schematic diagram which shows the structural example of the fuel-injection system which concerns on the same embodiment. It is a schematic diagram which shows the structural example of the cooling water introduction passage of the fuel injection system which concerns on the same embodiment. It is a schematic diagram which shows the structural example of the cooling water introduction passage of the fuel injection system which concerns on the same embodiment. It is a schematic diagram which shows the structural example of the control apparatus of the fuel-injection system which concerns on the same embodiment. 4 is a flowchart showing an example of cooling control during operation of the internal combustion engine by the control device for the fuel injection system according to the embodiment; 4 is a flowchart showing an example of cooling control after the internal combustion engine is stopped by the control device for the fuel injection system according to the embodiment;

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the present specification and drawings, constituent elements having substantially the same functional configuration are denoted by the same reference numerals, thereby omitting redundant description.

<1. Overall Configuration of Exhaust Purification System>
In this embodiment, a fuel injection system that injects fuel into an exhaust passage will be described as an example of an injection system.

First, an example of an exhaust purification system 1 including a fuel injection system 90 according to this embodiment will be described with reference to FIG. FIG. 1 shows an example of the overall configuration of an exhaust purification system 1. As shown in FIG. The exhaust purification system 1 includes an oxidation catalyst 21 , a particulate filter 22 , a fuel injection system 90 and a control device 60 . The exhaust purification system 1 is a system for purifying the exhaust gas of a diesel engine, which is one aspect of the internal combustion engine 5 . collect.

Both the oxidation catalyst 21 and the particulate filter 22 are arranged inside the exhaust pipe 11 . The oxidation catalyst 21 is provided upstream of the particulate filter 22 . Exhaust gas discharged from the internal combustion engine 5 flows through the exhaust pipe 11, passes through the oxidation catalyst 21 and the particulate filter 22, and flows downstream. A device for removing other components such as nitrogen oxides in the exhaust gas may be arranged downstream of the particulate filter 22 .

The particulate filter 22 collects PM in exhaust gas passing through the particulate filter 22 . The particulate filter 22 may be a known particulate filter, and for example, a honeycomb filter made of a ceramic material is used. Most of the PM collected by the particulate filter 22 accumulates on the particulate filter 22 until regeneration control of the particulate filter 22 is performed.

The oxidation catalyst 21 oxidizes unburned fuel injected from the fuel injection system 90 . The oxidation catalyst 21 raises the temperature of the exhaust gas passing through the oxidation catalyst 21 by the heat of oxidation generated. The oxidation catalyst 21 may be a known oxidation catalyst. For example, a catalyst obtained by adding a predetermined amount of a rare earth element such as cerium to a catalyst in which platinum is supported on alumina is used.

Temperature sensors 50 and 52 are provided upstream and downstream of the oxidation catalyst 21, respectively. Further, a differential pressure sensor 54 is provided to detect the differential pressure between the pressure on the upstream side and the pressure on the downstream side of the particulate filter 22 . Sensor signals from these sensors are output to the control device 60, and the temperature and differential pressure at each position are detected. These sensors may be omitted if the temperature and pressure difference can be estimated by calculation.

The fuel injection system 90 measures the amount of fuel supplied from the fuel tank 30 and injects it into the exhaust pipe 11 . In this embodiment, a fuel injection system 90 is provided by branching from the fuel supply passage of the fuel supply system of the internal combustion engine 5 . Specifically, the fuel supply system of the internal combustion engine 5 includes a fuel tank 30 for storing fuel, a fuel pump 32 for sucking up and pumping the fuel in the fuel tank 30, and a fuel for removing foreign matter mixed in the fuel. and a filter 34 .

Fuel in the fuel tank 30 is discharged by the fuel pump 32 and sent to the fuel filter 34 through the fuel supply passage 36 . A portion of the fuel that has passed through the fuel filter 34 is sent to the fuel injection system 90 through the fuel passage 38a. Another part of the fuel sent to the fuel filter 34 is sent to the internal combustion engine 5 through the fuel passage 37 . Excess fuel of the fuel sent to the internal combustion engine 5 is returned to the fuel tank 30 through the fuel recirculation passage 35 .

In the present embodiment, fuel is supplied to the fuel injection system 90 through the fuel passage 38a branched from the fuel path that supplies fuel to the internal combustion engine 5. Fuel may be supplied to the fuel injection system 90 via an independent fuel path other than the fuel path that is supplied to the fuel injection system 90 . Further, a fuel supply path independent from the fuel supply system of the internal combustion engine 5 may be provided, such as by providing a fuel tank separate from the fuel tank 30 storing the fuel supplied to the internal combustion engine 5 .

The fuel injection system 90 comprises a metering unit 70 and an injection module 80 . The metering unit 70 regulates the flow of fuel supplied to the injection module 80 via the fuel passage 38b. The injection module 80 comprises an injection valve that opens and closes according to the pressure of the supplied fuel. The metering unit 70 is driven and controlled by the control device 60 . It should be noted that the fuel passages 38a and 38b are one aspect of liquid passages.

The fuel injection system 90 has a cooling device 100 . The cooling device 100 mainly cools the injection module 80 which is likely to be heated under the influence of exhaust heat. In the present embodiment, the cooling device 100 cools the injection module 80 and the like by circulating the cooling water of the internal combustion engine 5 in the cooling water circulation passage 95 and dissipating heat from the injection module 80 and the like.

The injection module 80 is arranged in the middle of the cooling water circulation passage 95 . Cooling water for the internal combustion engine 5 can flow through the injection module 80 . The internal combustion engine 5 includes a cooling water circuit 4 that is formed in the engine block and circulates cooling water while passing through the radiator 3 . The cooling water circuit 4 includes a pump 2 that circulates cooling water. The pump 2 is driven by the output of the internal combustion engine 5, for example, and discharges cooling water. The internal combustion engine 5 includes a temperature sensor 6 that measures the temperature of cooling water circulating in the cooling water circuit 4 . The cooling water circulation passage 95 branches off from the cooling water circuit 4 at the branching portion 7 provided in the cooling water circuit 4 on the downstream side of the pump 2 , and joins at the joining portion 9 provided in the cooling water circuit 4 on the upstream side of the pump 2 . Joins the cooling water circuit 4 .

The cooling water circulation passage 95 includes a cooling water introduction passage 95 a that introduces cooling water into the injection module 80 and a cooling water discharge passage 95 b that discharges the cooling water from the injection module 80 . A portion of the cooling water introduction passage 95a is arranged adjacent to the fuel passage 38b that connects the metering unit 70 and the injection module 80 . While the internal combustion engine 5 is operating, the cooling water circulates through the cooling water circulation passage 95 by driving the pump 2 . Heat is radiated from the fuel in the injection module 80, the fuel in the fuel passage 38b, and the injection module 80 by the circulating cooling water.

The cooling water circulation passage 95 also includes a bypass passage 95c that connects the cooling water introduction passage 95a and the cooling water discharge passage 95b. A three-way valve 99 is provided at the connecting portion between the coolant outlet passage 95b and the bypass passage 95c. A cooling water circulation pump 97 is provided in the middle of the bypass passage 95c. The three-way valve 99 and the cooling water circulation pump 97 are driven and controlled by the controller 60 .

In this embodiment, the three-way valve 99 allows cooling water to flow from the injection module 80 side to the radiator 3 side in a non-energized state, while cooling from the injection module 80 side to the bypass passage 95c side in an energized state. Allows water flow. Therefore, by energizing the three-way valve 99 and driving the cooling water circulation pump 97, cooling water can be circulated through the injection module 80 even while the internal combustion engine 5 is stopped.

<2. Configuration of Fuel Injection System>
Next, a configuration example of the fuel injection system 90 will be described with reference to FIG. FIG. 2 is a schematic diagram showing a configuration example of the fuel injection system 90. As shown in FIG. The fuel injection system 90 comprises a metering unit 70 and an injection module 80 . The injection module 80 is fixed to the exhaust pipe 11 upstream of the oxidation catalyst 21 and injects fuel into the exhaust pipe 11 . The metering unit 70 adjusts the injection quantity of fuel injected from the injection module 80 . A fuel passage 38a is connected to the metering unit 70, and part of the fuel pressure-fed by the fuel pump 32 is supplied to the metering unit 70 (see FIG. 1). The metering unit 70 and the injection module 80 are connected by a fuel passage 38b, and the fuel is metered by the metering unit 70 and supplied to the injection module 80. FIG.

The metering unit 70 includes a shutoff valve 72 , an upstream pressure/temperature sensor 74 , a control valve 76 and a downstream pressure sensor 78 in order from the upstream side along the direction of fuel flow.

The shutoff valve 72 opens the fuel passage 38a when fuel injection into the exhaust pipe 11 is performed, and shuts off the fuel passage 38a when fuel injection into the exhaust pipe 11 is not performed. The shutoff valve 72 is composed of, for example, an on/off valve equipped with an electromagnetic solenoid, which opens the fuel passage 38a when energized and shuts off the fuel passage 38a when not energized. The cutoff valve 72 is controlled to be driven by the control device 60 . For example, the control device 60 energizes the shutoff valve 72 when performing forced regeneration control of the particulate filter 22, and stops energizing the shutoff valve 72 when not performing forced regeneration control. As a result, the supply of fuel to the control valve 76 and its stop are switched.

Control valve 76 adjusts the amount of fuel injected into exhaust pipe 11 via injection module 80 . The control valve 76 is composed of, for example, an on/off valve equipped with an electromagnetic solenoid, and driven based on a PWM (Palse Width Modulation) signal transmitted from the control device 60 . For example, the control device 60 controls the differential pressure obtained from the sensor signal of the upstream pressure/temperature sensor 74 and the sensor signal of the downstream pressure sensor 78, or the upstream The duty ratio of the control valve 76 is controlled based on the sensor signal of the side pressure/temperature sensor 74 . For example, if the control valve 76 is an on/off valve that opens when energized, the controller 60 controls the ratio of the energization time to the injection cycle time of each injection cycle. This regulates the amount of fuel supplied to the injection module 80 .

The upstream pressure/temperature sensor 74 is provided in the fuel passage 39a that connects the cutoff valve 72 and the control valve 76, and measures the fuel pressure upstream of the control valve 76 (hereinafter also referred to as "upstream fuel pressure"). ) and fuel temperature. The downstream pressure sensor 78 is provided in the fuel passage 39b on the downstream side of the control valve 76, and detects the pressure of the fuel on the downstream side of the control valve 76 (hereinafter also referred to as "downstream fuel pressure"). . For example, the control device 60 sets the duty ratio of the control valve 76 based on the differential pressure between the upstream fuel pressure and the downstream fuel pressure or the upstream fuel pressure. When the same amount of fuel is supplied to the injection module 80, the controller 60 sets the duty ratio of the control valve 76 to be smaller as the differential pressure or the upstream fuel pressure is relatively higher. The duty ratio of the control valve 76 is set larger as the upstream fuel pressure is relatively lower.

A fuel return pipe having an orifice passage or a one-way valve and leading to the fuel tank 30 may be connected between the shutoff valve 72 and the control valve 76 . By providing the fuel return pipe, it is possible to prevent the pressure of the fuel supplied to the control valve 76 from becoming excessively high, thereby preventing damage to components such as the upstream pressure/temperature sensor 74 .

The injection module 80 comprises an injection valve 81 and a cooling holder 87 . The injection valve 81 is configured as a mechanical on-off valve that opens according to the pressure of the fuel supplied from the metering unit 70, for example. Injection module 80 includes valve body 82 , valve spring 84 and valve seat 86 . A valve spring 84 biases the valve body 82 toward the valve seat 86 . When the pressure of the fuel supplied from the metering unit 70 exceeds the valve opening pressure set according to the biasing force of the valve spring 84, the valve body 82 is separated from the valve seat 86 to open the valve.

The cooling holder 87 has a cooling chamber 88 through which cooling water for the internal combustion engine 5 can flow. The cooling chamber 88 is formed to surround the injection valve 81. Cooling water is introduced into the cooling chamber 88 through a cooling water introduction passage 95a, and the cooling water is discharged from the cooling chamber 88 through a cooling water outlet passage 95b. derived. While the cooling water circulates through the cooling water circulation passage 95, the heat of the injection valve 81 is transferred to the cooling water, and the heating of the injection valve 81 is suppressed. A part of the cooling water introduction passage 95a is arranged adjacent to the fuel passage 38b. As a result, the heat of the fuel in the fuel passage 38b is transferred to the cooling water, and heating of the fuel is also suppressed.

Injection module 80 includes a module temperature sensor 89 for measuring the temperature within the module. A module temperature sensor 89 is preferably provided to measure the temperature near the valve body 82 of the injection valve 81 .

3 and 4 are explanatory diagrams showing configuration examples of the fuel passage 38b and the cooling water introduction passage 95a. As shown in FIG. 3, a portion of the fuel passage 38b and a portion of the cooling water introduction passage 95a are both disposed within the heat insulating pipe 92. As shown in FIG. As a result, the cooling efficiency is enhanced when the cooling water passing through the cooling water introduction passage 95a cools the fuel in the fuel passage 38b. Instead of using the heat insulating pipe 92, the fuel passage 38b and the cooling water introduction passage 95a may be covered with heat insulating material such as heat insulating tape.

In the present embodiment, as shown in FIG. 4, the cooling water introduction passage 95a includes a first portion 95aa disposed together with the fuel passage 38b in the heat insulating pipe 92 and a second portion 95aa that bypasses the first portion. 2 portions 95ab. The first portion 95aa and the second portion 95ab branch from the passage switching valve 96, and the cooling water passage is switched to the first portion 95aa or the second portion 95ab. The operation of passage switching valve 96 is controlled by controller 60 . The passage switching valve 96 may be provided at a position where the first portion 95aa and the second portion 95ab meet.

<3. Control device>
(3-1. Configuration example)
Next, the configuration of the control device 60 will be specifically described. The control device 60 controls the metering unit 70 to inject fuel into the exhaust pipe 11 via the injection module 80 . Further, the control device 60 executes cooling control of the fuel injection system 90 after the internal combustion engine 5 is stopped. The control device 60 includes a processor such as a CPU (Central Processing Unit) and storage elements such as a RAM (Random Access Memory) and a ROM (Read Only Memory).

FIG. 5 shows the functional configuration of the control device 60. As shown in FIG. The control device 60 includes an injection control section 61 and a cooling control section 63 . The injection control unit 61 performs forced regeneration control to forcibly burn PM deposited on the particulate filter 22 . The control device 60 performs forced regeneration control, for example, when the differential pressure detected by the differential pressure sensor 54 exceeds a reference value. As the amount of PM trapped in the particulate filter 22 increases, the pressure difference between the pressure upstream and downstream of the particulate filter 22 increases. Further, the control device 60 may execute forced regeneration control before stopping the internal combustion engine 5 when the ignition switch of the internal combustion engine 5 is turned off. In the forced regeneration control, the control device 60 controls the fuel injection system 90 to inject fuel into the exhaust pipe 11 upstream of the oxidation catalyst 21 .

For example, the control device 60 performs intake throttling or post-injection to the internal combustion engine 5 to increase the temperature of the exhaust gas and increase the temperature of the oxidation catalyst 21, and then performs fuel injection from the fuel injection system 90. may As a result, the fuel is efficiently oxidized in the oxidation catalyst 21, and the temperature of the exhaust gas rises quickly. At this time, the controller 60 adjusts the amount of fuel injected from the fuel injection system 90 so that the temperature of the exhaust gas flowing into the particulate filter 22 is approximately 300 to 600.degree. In this manner, high-temperature exhaust gas flows into the particulate filter 22, and PM inside the particulate filter 22 is combusted. The forced regeneration control by fuel injection from the fuel injection system 90 is performed for about 15 to 30 minutes, for example, depending on the estimated amount of PM trapped in the particulate filter 22 .

The cooling control unit 63 controls the operation of the passage switching valve 96 , the cooling water circulation pump 97 and the three-way valve 99 to control the cooling of the fuel injection system 90 . Specifically, based on the sensor signal of the temperature sensor 6, the cooling control unit 63 adjusts the temperature of cooling water introduced into the injection module 80 via the cooling water circulation passage 95 (hereinafter also referred to as "inlet cooling water temperature"). Get information about The cooling control unit 63 also acquires temperature information of the fuel introduced into the injection module 80 based on the sensor signal from the upstream pressure/temperature sensor 74 .

The cooling control unit 63 controls the operation of the passage switching valve 96 based on the information on the inlet cooling water temperature and the fuel temperature. The cooling control unit 63 operates the passage switching valve 96 so that the cooling water passes through the first portion 95aa of the cooling water introduction passage 95a when the inlet cooling water temperature is lower than the fuel temperature. On the other hand, the cooling control unit 63 operates the passage switching valve 96 so that the cooling water passes through the second portion 95ab of the cooling water introduction passage 95a when the inlet cooling water temperature is equal to or higher than the fuel temperature. As a result, the cooling water passage is controlled so that the cooling water does not heat the fuel.

Further, the cooling control unit 63 drives the cooling device 100 when the temperature in the exhaust passage exceeds a preset start threshold after the internal combustion engine 5 is stopped, and drives the cooling device 100 when a predetermined termination condition is satisfied. terminate. Specifically, after the internal combustion engine 5 is stopped, the driving of the pump 2 provided in the internal combustion engine 5 is stopped, and the circulation of the cooling water to the cooling water circulation passage 95 is stopped. As a result, the cooling water staying in the injection module 80 is heated to a boiling state, and the temperature of the injection valve 81 rises. Therefore, the cooling control unit 63 drives the cooling water circulation pump 97 to circulate the cooling water to the injection module 80 when the injection module 80 is in a state where it can be heated after the internal combustion engine 5 is stopped.

Further, the cooling control unit 63 stops the cooling water circulation pump 97 to terminate the circulation of the cooling water to the injection module 80 when the injection module 80 is no longer likely to be heated. As a result, damage or sticking of the injection valve 81 caused by the fuel deterioration due to the heating of the injection module 80 after the internal combustion engine 5 is stopped is suppressed.

(3-2. Operation example)
Next, an example of operation during cooling control of the fuel injection system 90 by the cooling control section 63 of the control device 60 will be described.

FIG. 6 is a flowchart showing an example of processing of the control device 60 until the operation of the internal combustion engine 5 is stopped. The cooling control unit 63 controls the upstream pressure/temperature sensor 74 while the internal combustion engine 5 is operating, that is, while the cooling water is circulating in the cooling water circulation passage 95 by driving the pump 2 provided in the internal combustion engine 5 . It is determined whether or not the measured fuel temperature T_f exceeds the inlet cooling water temperature T_c measured by the temperature sensor 6 (step S11).

When the fuel temperature T_f exceeds the inlet cooling water temperature T_c (S11/Yes), the cooling control unit 63 operates the passage switching valve 96 so that the cooling water passes through the first portion 95aa of the cooling water introduction passage 95a. (step S13). As a result, the fuel in the fuel passage 38b is cooled by the cooling water. On the other hand, when the fuel temperature T_f is equal to or lower than the inlet cooling water temperature T_c (S11/No), the cooling control unit 63 operates the passage switching valve 96 so that the cooling water passes through the second portion 95ab of the cooling water introduction passage 95a. (step S15). As a result, it is possible to prevent the temperature of the fuel in the fuel passage 38b from rising due to the heat of the cooling water.

Then, the cooling control unit 63 determines whether or not the internal combustion engine 5 has stopped (step S17). While the internal combustion engine 5 is operating (S17/No), the cooling control unit 63 repeats operation control of the passage switching valve 96 based on the fuel temperature T_f and the inlet cooling water temperature T_c. S17/Yes), the operation control of the passage switching valve 96 is ended. In this way, the cooling control section 63 suppresses the temperature rise of the fuel supplied to the injection module 80 during operation of the internal combustion engine 5 .

FIG. 7 is a flowchart showing an example of processing of the control device 60 after the ignition switch of the internal combustion engine 5 is turned off. After the ignition switch of the internal combustion engine 5 is turned off, the injection control unit 61 injects fuel into the exhaust pipe 11 on the upstream side of the oxidation catalyst 21 via the injection module 80 for a predetermined period (step S21). During this time, the operation of the internal combustion engine 5 is continued, and the PM deposited on the particulate filter 22 is burned by the high-temperature exhaust gas, and the particulate filter 22 is regenerated. When the regeneration control of the particulate filter 22 ends, the internal combustion engine 5 stops. As a result, circulation of cooling water by the pump 2 provided in the internal combustion engine 5 is stopped.

Next, when the internal combustion engine 5 is stopped, the cooling control unit 63 determines whether the exhaust temperature T_g measured by the temperature sensor 50 exceeds a preset start threshold value T_0 (step S23). The start threshold T_0 may be set to an appropriate temperature in consideration of the temperature at which the fuel may thermally deteriorate, the heat transfer rate from the exhaust pipe 11 to the injection valve 81, and the like. If the exhaust temperature T_g is equal to or lower than the start threshold value T_0 (S23/No), it is considered that there is no risk of damage to the injection module 80 due to thermal deterioration of the fuel, so the cooling control unit 63 terminates this routine.

On the other hand, when the exhaust temperature T_g exceeds the start threshold value T_0 (S23/Yes), the cooling control unit 63 controls the cooling water in the cooling water lead-out passage 95b to flow into the cooling water introduction passage 95a via the bypass passage 95c. The three-way valve 99 is operated to start driving the cooling water circulation pump 97 (step S24). As a result, the cooling water circulates to the injection module 80 even though the internal combustion engine 5 is in a stopped state. Therefore, even if exhaust heat remaining after the internal combustion engine 5 is stopped is transmitted to the injection module 80, the temperature rise of the injection module 80 can be suppressed.

Next, the cooling control unit 63 determines whether or not a termination condition for terminating the cooling water circulation is satisfied (step S27). The termination condition may be, for example, that the rate of increase of a predetermined temperature correlated with the temperature of the injection valve 81 falls below a preset termination reference value. Specifically, the termination condition may be that the rate of increase in module temperature measured by the module temperature sensor 89 falls below a predetermined termination reference value. That is, when the influence of exhaust heat on the injection valve 81 becomes small and it can be judged that the subsequent temperature rise is small, the circulation of the cooling water can be terminated.

The termination condition may be that the driving time of the cooling device 100, that is, the elapsed time after the cooling water circulation pump 97 starts circulating the cooling water exceeds a preset termination reference value. In other words, the circulation of the cooling water can be terminated after the cooling water has been circulated for a period of time during which the subsequent temperature rise of the injection valve 81 is expected to be small.

The end condition is that after a predetermined correlation temperature correlated with the temperature of the injection valve 81 rises, the correlation temperature is the initial value when the cooling device 100 is driven, or the end after adding a predetermined value to the initial value. It may be a decrease to a reference value. For example, after the module temperature measured by the module temperature sensor 89 rises, the module temperature is the value when the cooling water circulation pump 97 starts circulating the cooling water, or the termination reference value obtained by adding a predetermined value to the initial value. , the cooling water circulation can be terminated.

Alternatively, the termination condition may be that the exhaust temperature T_g measured by the temperature sensor 50 decreases to a preset termination reference value. Since the internal combustion engine 5 has already stopped, it is expected that the temperature rise of the injection valve 81 will be small after the exhaust gas temperature T_g drops to the termination reference value. be able to.

In this embodiment, the cooling control unit 63 determines that the end condition is met when any one of the above four conditions is met. As a result, excessive temperature rise of the injection valve 81 can be suppressed while avoiding excessively long cooling control time.

If the termination condition is not satisfied (S27/No), the cooling control unit 63 repeats the determination of step S27 until the termination condition is satisfied. When the termination condition is satisfied (S27/Yes), the cooling control unit 63 stops driving the cooling water circulation pump 97 and terminates the operation of the three-way valve 99 (step S29). This ends the cooling control.

Even after the internal combustion engine 5 is stopped, if the fuel temperature T_f is higher than the inlet cooling water temperature T_c, the cooling water is allowed to pass through the first portion 95aa of the cooling water introduction passage 95a so that It is also possible to suppress the temperature rise of the stagnant fuel. This makes it possible to further suppress thermal deterioration of the fuel.

As described above, according to the fuel injection system 90 according to the present embodiment, the cooling device 100 is driven when the injection module 80 can be heated under the influence of exhaust heat after the internal combustion engine 5 has stopped. . As a result, it is possible to suppress damage or sticking of the injection valve 81 due to thermal deterioration of the fuel.

Further, according to the fuel injection system 90 according to the present embodiment, a part of the cooling water introduction passage 95a for introducing the cooling water of the internal combustion engine 5 to the injection module 80 is a fuel passage for supplying fuel to the injection module 80. 38b. As a result, the fuel in the fuel passage 38b can also be cooled, and damage and sticking of the injection valve 81 due to thermal deterioration of the fuel can be further suppressed.

Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention belongs can conceive of various modifications or modifications within the scope of the technical idea described in the claims. It is understood that these also naturally belong to the technical scope of the present invention.

For example, in the above embodiment, the cooling water introduction passage 95a for introducing cooling water into the injection module 80 branches into a first portion 95aa and a second portion 95ab, of which the first portion 95aa is connected to the fuel passage 38b. Although they are arranged adjacent to each other, it is not essential in the present invention that a portion of the cooling water introduction passage 95a is arranged adjacent to the fuel passage 38b.

Further, the configuration in which a portion of the cooling water introduction passage 95a is arranged adjacent to the fuel passage 38b is not limited to the example of the above embodiment. While the cooling water introduction passage 95a is a single passage without a branched portion, the fuel passage 38b is composed of a first portion adjacent to the cooling water introduction passage 95a and a second portion bypassing the first portion. It may be configured separately. In this case, when the fuel temperature T_f is higher than the inlet cooling water temperature T_c, the temperature rise of the fuel introduced into the injection module 80 can be suppressed by controlling the fuel to pass through the first portion. can.

In the above embodiment, the cooling device 100 for cooling the injection module 80 after the internal combustion engine 5 is stopped is a device in which the bypass passage 95c, the cooling water circulation pump 97, and the three-way valve 99 are added to the cooling water circulation passage 95. However, the invention is not limited to such examples. An independent cooling device that does not use the cooling water circulation passage 95 may be used as the cooling device 100 that cools the injection module 80 after the internal combustion engine 5 is stopped.

Further, the injection system according to the above embodiment can be applied not only to a fuel injection system but also to a reducing agent injection system that supplies a liquid reducing agent into an exhaust passage. In this case, the cooling control section performs cooling control so that the temperature of the injection module or the electromagnetically controlled injection valve does not exceed the heat resistant temperature of the injection valve or the temperature at which the composition of the liquid reducing agent may change.

1: exhaust purification system, 4: cooling water circuit, 5: internal combustion engine, 6: temperature sensor, 11: exhaust pipe, 21: oxidation catalyst, 22: particulate filter, 38a and 38b: fuel passage, 50: temperature sensor, 60: control device, 61: injection control unit, 63: cooling control unit, 70: metering unit, 74: upstream pressure/temperature sensor, 80: injection module, 81: injection valve, 87: cooling holder, 88: cooling Chamber, 89: Module temperature sensor, 90: Fuel injection system, 92: Heat insulating pipe, 95: Cooling water circulation passage, 95a: Cooling water introduction passage, 95aa: First portion, 95ab: Second portion, 95b: Cooling water Outlet passage, 95c: bypass passage, 96: passage switching valve, 97: cooling water circulation pump, 99: three-way valve, 100: cooling device

Claims (8)

An injection valve (81) for injecting a liquid material into an exhaust passage of an internal combustion engine (5) of a vehicle, a cooling device (100) for cooling the injection valve (81), and a cooling control for controlling the cooling device (100) an injection system (90) comprising a portion (63);
The cooling device (100)
a cooling holder (87) having a cooling chamber (88) through which a cooling medium passes and holding the injection valve (81);
A cooling water circuit (4) of the internal combustion engine (5) having a pump (2) and a radiator (3) branches from the downstream side of the pump (2) and introduces the cooling medium into the cooling chamber (88). an introduction passageway (95a);
a lead-out passage (95b) for leading the cooling medium from the cooling chamber (88) and joining the cooling water circuit (4) on the upstream side of the pump (2);
a bypass passage (95c) connecting the introduction passage (95a) and the discharge passage (95b) and bypassing the pump (2) and the radiator (3);
A cooling water circulation pump (97) provided in the bypass passage (95c),
The cooling control section (63)
driving the cooling water circulation pump (97) when the temperature in the exhaust passage exceeds a preset start threshold with the internal combustion engine (5) stopped and the pump (2) stopped being driven; terminating the driving of the cooling water circulation pump (97) when a predetermined termination condition is satisfied;
An injection system characterized by: The termination condition is that the rate of increase of a predetermined temperature correlated with the temperature of the injection valve (81) falls below a preset termination reference value.
2. The injection system according to claim 1, characterized in that: The termination condition is that the driving time of the cooling device (100) exceeds a preset termination reference value.
2. The injection system according to claim 1, characterized in that: The end condition is an initial value when the correlation temperature drives the cooling device (100) after a rise in a predetermined correlation temperature correlated with the temperature of the injection valve (81), or is predetermined at the initial value value is added to the end criterion value,
2. The injection system according to claim 1, characterized in that: wherein the termination condition is that the temperature in the exhaust passage falls to a preset termination reference value;
2. The injection system according to claim 1, characterized in that: A part of the introduction passageway (95a) is arranged in contact with a liquid passageway (38b) that supplies the liquid material to the injection valve (81).
The injection system according to any one of claims 1 to 5, characterized in that: The introduction passageway (95a) is
A first portion (95aa) arranged in contact with the liquid passage (38b), a second portion (95ab) bypassing the first portion (95aa), a passage switching valve (96) that switches to the first portion (95aa) or the second portion (95ab);
The cooling control unit (63)
passing the cooling medium through the first portion (95aa) when the temperature of the liquid material is higher than the temperature of the cooling medium;
passing the cooling medium through the second portion (95ab) when the temperature of the liquid material is lower than the temperature of the cooling medium;
7. Injection system according to claim 6, characterized in that: The liquid passage (38b) is
a first portion arranged in contact with the introduction passage (95a); a second portion bypassing the first portion; and a passage switching valve that switches to
The cooling control unit (63)
passing the liquid material through the first portion when the temperature of the liquid material is higher than the temperature of the cooling medium;
passing the liquid material through the second portion when the temperature of the liquid material is lower than the temperature of the cooling medium;
7. Injection system according to claim 6, characterized in that:

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