JP2008019827A - Deposit removal device for cylinder pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain formation of deposit around a cylinder pressure sensor. <P>SOLUTION: A heater 11 is provided at a front end part 8 of the cylinder pressure sensor 1 and thermally decomposes deposit attached to a clearance 24 which is a boundary part of the front end part 8 and a cylinder head 21 surrounding this. As a temperature sensor 12 for detecting a generation state of the deposit in the clearance 24 is also provided, and the heater 11 is controlled based on its output, the heater 11 is controlled according to the generation state of the deposit. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a deposit removing device for removing deposits generated around an in-cylinder pressure sensor that detects pressure in a combustion chamber of an internal combustion engine.

  In order to detect the combustion state of the internal combustion engine, an in-cylinder pressure sensor that detects the pressure in the combustion chamber is used (for example, Patent Document 1 and Patent Document 2). The in-cylinder pressure sensor is mounted on the cylinder head, and the tip of the in-cylinder pressure sensor is exposed to the combustion chamber from a through hole provided in the combustion chamber. A clearance is provided between the cylinder pressure sensor and the through hole of the cylinder head for the purpose of facilitating mounting.

JP 2005-43364 A JP-A-5-52693

  However, if a deposit is generated in the clearance and the deposit is hardened, a large stress may be generated at the tip of the in-cylinder pressure sensor when the in-cylinder pressure sensor is removed, and the in-cylinder pressure sensor may be damaged. In a fuel injection device (injector), a seal material such as polytetrafluoroethylene may be disposed to prevent deposits from being generated in such clearance, but the in-cylinder pressure sensor is used in an environment where the temperature is higher than that of the injector. In addition, since there is no self-cooling action at the time of fuel injection like an injector, such a sealing material cannot be used.

  Therefore, an object of the present invention is to provide a novel means for suppressing the generation of deposit around the in-cylinder pressure sensor.

  A cylinder pressure sensor deposit removing apparatus according to the present invention is a cylinder pressure sensor deposit removing apparatus attached to a combustion chamber of an internal combustion engine, a heater disposed inside the cylinder pressure sensor, and a control for controlling the heater. And the control means controls the heating of the heater when a deposit is generated in the in-cylinder pressure sensor.

  In the present invention, the heater disposed inside the in-cylinder pressure sensor is heated when the deposit is generated in the in-cylinder pressure sensor, so that the generated deposit can be pyrolyzed.

  In the present invention, it is preferable that a temperature sensor for detecting the temperature of the in-cylinder pressure sensor is further provided, and the control means controls the heater according to the temperature detected by the temperature sensor. Since the deposit has high heat insulation properties, the formation of the deposit can be detected based on the temperature.

  The present invention may further include deposit detection means for detecting a deposit generation state in the in-cylinder pressure sensor, and the control means may control the heater according to the deposit generation state based on the output of the deposit detection means. The deposit generation state mentioned here includes components and properties in addition to the presence and amount of deposit. The deposit detection means includes not only detecting a physical quantity caused by deposit generation, but also predicting or estimating a deposit generation state based on other physical quantities that may affect deposit generation.

  The control means preferably turns on the heater on condition that the temperature detected by the temperature sensor has reached a predetermined first reference value. In this aspect, the deposit can be suitably processed by turning on the heater on condition that the actual temperature has reached the predetermined first reference value at which the generation of the predetermined amount of deposit is predicted or estimated. .

  The control means preferably turns off the heater on condition that the temperature detected by the temperature sensor has reached a predetermined second reference value higher than the first reference value. Excessive heating with a heater can produce an inorganic deposit that is difficult to remove. Therefore, the deposit can be suitably processed by turning off the heater on condition that the actual temperature has reached a considerably high temperature.

  The heater heating control by the control means is preferably executed on condition that the fuel cut control is being executed. In this case, the risk of self-ignition due to the heating control of the heater can be suppressed.

  Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, an in-cylinder pressure sensor 1 according to an embodiment of the present invention includes a hollow sensor main body 2 forming a casing, a pressure receiving rod 4 and a piezoelectric element 5 accommodated in a hollow portion 3 in the sensor main body 2. .

  The sensor body 2 is generally cylindrical and has a base portion 6, an intermediate portion 7, and a tip portion 8. The tip portion 8 is a portion having a smaller diameter than the intermediate portion 7, and in a state where it is attached to the cylinder head 21, a clearance 24 is formed around the tip portion 8 as described later. A diaphragm 9 is fixed to the hollow portion 3 so as to be substantially flush with the end face 8 a of the tip 8. The intermediate portion 7 is formed with a screw portion 7a and a hexagon bolt portion 7b.

  The tip of the pressure receiving rod 4 is in contact with the diaphragm 9 from the inside. The pressure receiving rod 4 and the piezoelectric element 5 are fixed to the sensor body 2 with a predetermined load by a set screw 10.

  A heater 11 and a temperature sensor 12 are disposed at the tip 8 of the sensor body. The heater 11 is a ceramic heater formed in a cylindrical shape, and a heater capable of rapid overheating such as a PTC heater is preferable. The heater 11 is disposed over almost the entire length of the tip 8.

  The temperature sensor 12 is disposed in contact with the heater 11. The temperature sensor 12 can detect the temperature of the tip 8 including the heater 11. It is preferable to use a thermocouple for the temperature sensor 12. Lead wires 11 a and 12 a from the heater 11 and the temperature sensor 12 are detachably connected to the wire harness 14 together with other lead wires (not shown) by the connector 13.

  The in-cylinder pressure sensor 1 configured as described above is installed on the cylinder head 21 of the engine by the screw portion 7a. In the installed state, the distal end portion of the in-cylinder pressure sensor 1 is exposed into the combustion chamber 22 from a through hole 23 provided in the combustion chamber 22. The end face 8 a of the tip 8 and the end face of the diaphragm 9 are substantially flush with the upper wall portion of the combustion chamber 22. In addition, a clearance 24 is provided at the boundary between the outer peripheral surface of the tip 8 of the sensor body 2 and the through hole 23 for the purpose of facilitating mounting. Accordingly, the heater 11 is disposed in the vicinity of the clearance 24 and along the clearance 24, and deposits in the entire area of the clearance 24 that is a boundary portion between the tip 8 and the cylinder head 21 surrounding the tip 8 can be removed. .

  The ECU 30 that controls the entire apparatus is composed of a well-known microcomputer including a CPU, RAM, ROM, nonvolatile memory, A / D converter, D / A converter, and I / O port interconnected by a data bus. ing. Signals from the piezoelectric element 5 and the temperature sensor 12 of the in-cylinder pressure sensor 1 are input to the input side of the ECU 30. On the input side of the ECU 30, a vehicle speed sensor 31 provided in the vicinity of the drive wheel, a throttle sensor 32 provided in the vicinity of the throttle valve, and a crank angle sensor provided in the vicinity of the engine crankshaft. 33. Various sensors including a water temperature sensor 34 installed in the cylinder block of the engine are connected, and signals indicating various physical quantities indicating the state of the vehicle are input. The heater 11 of the in-cylinder pressure sensor 1 is connected to the output side of the ECU 30 via a drive circuit (not shown). The ECU 30 executes fuel cut control separately from the processing according to the present invention for the purpose of saving fuel consumption. This fuel cut control is control for cutting fuel supply to a predetermined cylinder. Specifically, for example, the vehicle speed, throttle opening, engine speed, and engine water temperature input from sensors 31, 32, 33, and 34, for example. By referring to the predetermined fuel cut area map, when the running state is in the fuel cut area (for example, at the time of deceleration or at high rotation), the fuel supply to a predetermined cylinder is cut.

  The operation of the present embodiment configured as described above will be described below. FIG. 3 shows an outline of the deposit removal process executed by the ECU 30. This process routine is repeatedly executed while an ignition switch (not shown) is turned on. The change in temperature T during execution of this processing routine is shown in FIG.

  First, the ECU 30 determines whether 1 is set (turned on) in a flag immediately after processing to be described later (S10). Here, this is the first process, and the flag is reset (turned off), and therefore affirmative in step S10. Next, the ECU 30 reads the temperature T detected by the temperature sensor 12 (S20), and compares the read temperature T with a threshold Ta that is a predetermined first reference value (S30). This threshold Ta is a temperature at which deposits are considered to have been generated. If the temperature T is equal to or lower than the threshold Ta, the process is returned.

  If the temperature T exceeds the threshold Ta, it is next determined whether fuel cut control is being executed (S40, time t1). If the fuel cut control is not executed, the process is returned. In addition, since the apparatus of this embodiment performs the heating by the heater 11 on condition that fuel cut control is being performed, the possibility of the self-ignition resulting from the heating control of the heater 11 can be suppressed.

  When the fuel cut is being executed, the heater 11 is energized (S50), and the temperature T is read again (S60). The energization of the heater 11 and the reading of the temperature T are repeatedly executed until the temperature T exceeds a threshold value Tb that is a predetermined second reference value (S70). The threshold value Tb is set to a value higher than the threshold value Ta that is the first reference value described above. The threshold value Tb is set to a value higher than the temperature at which the deposit is removed and lower than the temperature at which the inorganic deposit is generated.

  When the temperature T exceeds the threshold value Tb (time t2), 1 is set, that is, turned on (S80), and the process is returned. This immediately after processing flag is reset on the condition that a predetermined time has passed as a time sufficient for the temperature T to fall within the normal operating range from the end of deposit removal by energization of the heater 11. (= 0).

  As a result of the above processing, as shown in FIG. 4, the temperature T in the present embodiment gradually increases due to the heat insulation of the deposit (t0 to t1) as the deposit is generated. When Ta is exceeded, the temperature rises rapidly due to the energization of the heater 11, and the saturation curve characteristic of the heater 11, the operation setting of the heater drive circuit, and / or the heat capacity of the cylinder head 21 in the vicinity of the tip of the in-cylinder pressure sensor 1 and its vicinity. When the temperature T exceeds the threshold value Tb (t2) due to the delay in temperature rise due to the temperature rise, the temperature decreases due to the heater 11 being turned off.

  As described above, in the present embodiment, since the deposit can be thermally decomposed by the heater 11 provided in the vicinity of the clearance 24, the generation of the deposit around the in-cylinder pressure sensor 1 can be suitably suppressed. In the present embodiment, the heater 11 is disposed in the distal end portion 8 in the vicinity of the boundary portion between the through hole 23 of the combustion chamber 22 and the distal end portion 8 of the in-cylinder pressure sensor 1. Can be easily replaced.

  In this embodiment, since heating by the heater 11 is controlled by the ECU 30, the deposit process can be performed flexibly. Further, in the present embodiment, it further includes deposit detection means for detecting the generation state of deposit in the clearance 24 that is a boundary portion between the through hole 23 and the tip end portion 8, and the ECU 30 controls the heater 11 based on the output of the deposit detection means. Since it controls, the heater 11 can be controlled according to the production | generation state of a deposit.

  Further, in the present embodiment, by utilizing the high heat insulating property of the deposit, the deposit detecting means is the temperature sensor 12 that detects the temperature of the sensor body, and the temperature detected by the temperature sensor 12 is a predetermined first reference value ( Since the ECU 30 turns on the heater 11 on the condition that the threshold value Ta) has been reached, the desired effect of the present invention can be obtained with a simple configuration.

  Further, in the present embodiment, the ECU 30 turns off the heater 11 on the condition that a predetermined second reference value (threshold value Tb) higher than the first reference value has been reached, so that it is difficult to remove by excessive heating. Generation of inorganic deposits can be suppressed.

  In the above embodiment, the present invention has been described with a certain degree of concreteness, but various modifications and changes can be made to the present invention without departing from the spirit and scope of the invention described in the claims. It must be understood that. That is, the present invention includes modifications and changes that fall within the scope and spirit of the appended claims and their equivalents. For example, the heater according to the present invention is not limited to the above-described ceramic heater or other structure as long as the deposit attached to the boundary portion between the tip portion 8 and the cylinder head 21, particularly the deposit 24, can be thermally decomposed. May be employed, and may be arranged on the surface instead of the inside of the tip 8.

  Various configurations other than the temperature sensor 12 can be adopted as the deposit detection means. Deposit detection means such as the temperature sensor 12 need not be installed in the sensor body 2.

  The deposit generation state mentioned here includes components and properties in addition to the presence and amount of deposit. The deposit detection means includes not only detecting a physical quantity that changes due to the generation of deposit, but also predicting or estimating the generation state of the deposit based on a physical quantity that can affect the generation of deposit. Since the deposit is formed with unburned fuel as a main element, it is preferable to predict or estimate the deposit generation state based on a parameter that can affect the remaining amount of unburned fuel in the combustion chamber. Such parameters include, but are not limited to, engine speed, required load, fuel injection amount, intake air amount, air-fuel ratio, valve timing, ignition timing, fuel properties, engine water temperature and outside air temperature. Each of these parameters may be used alone, or a plurality of types may be used in combination by a predetermined function. For example, by calculating the residual amount of unburned fuel per predetermined minute time based on such parameters, and accumulating the remaining amount in consideration of the decrease over time, the amount of deposit generated can be predicted or estimated. By energizing the heater 11 according to the estimated deposit generation amount and other generation states (for example, on condition that the generation amount exceeds a predetermined threshold), the same effect as in the above embodiment can be obtained. it can. The standby time after the heater is turned off can also be set or corrected according to the state of the vehicle.

  In the above embodiment, the heater 11 is turned off on condition that the threshold value Tb is exceeded. However, the heater is turned on for a predetermined time after a predetermined heating start condition is satisfied, and / or The heater may be controlled so that the temperature T becomes a constant temperature suitable for deposit pyrolysis. Further, the energization time and / or energization temperature for controlling the heater may be set or corrected to be different depending on the deposit generation state. For example, when it is estimated from the operation history that the components and properties of the deposit are likely to be hardened, hardening of the deposit can be suppressed by lowering the temperature of the heater 11 and lengthening the energization time.

  In the present invention, the detection element for detecting the in-cylinder pressure may be other types such as an optical fiber pressure type and a strain gauge type in addition to the piezoelectric type.

It is a longitudinal cross-sectional view which shows schematic structure of embodiment of this invention. It is a block diagram which shows the control system of embodiment. It is a flowchart which shows the deposit removal process in embodiment. It is a graph which shows an example of the temperature change in an embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 In-cylinder pressure sensor 2 Sensor main body 5 Piezoelectric element 8 Tip part 9 Diaphragm 11 Heater 12 Temperature sensor 21 Cylinder head 22 Combustion chamber 23 Through-hole 24 Clearance

Claims (6)

An in-cylinder pressure sensor deposit removing device attached to a combustion chamber of an internal combustion engine,
A heater disposed inside the in-cylinder pressure sensor, and a control means for controlling the heater;
The deposit removal device for an in-cylinder pressure sensor, wherein the control means controls the heating of the heater when a deposit is generated in the in-cylinder pressure sensor. The in-cylinder pressure sensor deposit removing apparatus according to claim 1,
A temperature sensor for detecting the temperature of the in-cylinder pressure sensor;
The deposit removing device for an in-cylinder pressure sensor, wherein the control means controls the heater according to a temperature detected by the temperature sensor. The in-cylinder pressure sensor deposit removing apparatus according to claim 1,
A deposit detecting means for detecting a deposit generation state in the in-cylinder pressure sensor;
The deposit removing device for an in-cylinder pressure sensor, wherein the control means controls the heater in accordance with a generation state of the deposit. The in-cylinder pressure sensor deposit removing apparatus according to claim 2,
The deposit removing device for an in-cylinder pressure sensor, wherein the control means turns on the heater on condition that the temperature detected by the temperature sensor has reached a predetermined first reference value. The in-cylinder pressure sensor deposit removing apparatus according to claim 4,
The deposit removing device for an in-cylinder pressure sensor, wherein the control means turns off the heater on condition that the temperature detected by the temperature sensor reaches a predetermined second reference value higher than the first reference value. . The in-cylinder pressure sensor deposit removing apparatus according to any one of claims 1 to 5,
The deposit removing device for an in-cylinder pressure sensor, wherein the control means controls the heating of the heater on condition that fuel cut control is being executed.

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