JP2009013969A - Diesel engine and fuel temperature operation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To predict temperature rise of fuel and inhibit excessive temperature rise of fuel. <P>SOLUTION: In this engine 1, a predicted value Tp of fuel is calculated and whether or not the predicted value Tp of fuel temperature reaches an upper limit temperature T is judged, based on fuel remaining quantity Vf, fuel temperature Th, engine speed Ne, outside temperature To, acquired from each sensor of a fuel remaining quantity sensor 21, a fuel temperature sensor 22, a crank angle sensor 24 and an outside temperature sensor 24, and fuel injection quantity Q calculated by ECU 20. If the predicted value Tp of fuel temperature reaches the upper limit temperature T in the judgment, the engine 1 limits torque of the engine 1 and collects fuel used for lubrication to a fuel tank 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a diesel engine in which fuel is used as a lubricating oil.

  Conventionally, a light oil lubricated diesel engine in which a reservoir for separating bubbles is disposed between a fuel tank and a diesel engine, and a lubricating fuel circulation circuit and a combustion fuel circulation circuit are configured between the reservoir and the engine. Is disclosed (Patent Document 1). In such a light oil lubricated diesel engine, light oil as a fuel is also used as a lubricant for each part of the engine and circulates through each part of the engine. For this reason, the oil only for lubrication is unnecessary, and the effort of oil replacement can be saved.

Japanese Utility Model Publication No. 60-194112

  By the way, such a light oil lubricated diesel engine uses fuel as lubricating oil for each part of the engine. If the temperature of the fuel used as the lubricating oil rises excessively in this way, the fuel evaporates and the viscosity decreases, and the fuel may not function as the lubricating oil. Thereby, it is considered that the lubrication state in the lubrication part deteriorates and causes engine failure.

  Therefore, an object of the present invention is to predict an increase in the temperature of the fuel and suppress an excessive increase in the temperature of the fuel.

  A diesel engine of the present invention that solves such a problem is a diesel engine in which fuel is used as a lubricating oil, and a calculation means for calculating a predicted value of the fuel temperature based on information that affects the fuel temperature of the engine, A judgment means for judging whether or not the predicted value of the fuel temperature reaches the upper limit temperature T is provided (claim 1). By adopting such a configuration, it is possible to predict an excessive increase in the fuel temperature and take measures against the excessive increase in the fuel temperature based on this prediction. The upper limit temperature T is a temperature set in advance as a temperature at which an appropriate lubrication state of each part of the engine can be maintained. Such an upper limit temperature T can be set in accordance with engine specifications and operating conditions.

  In such a diesel engine, the information affecting the fuel temperature of the engine is set to include at least one of the outside air temperature, the remaining amount of fuel in the fuel tank, the engine speed, the fuel injection amount, and the fuel temperature. (Claim 2). Engine fuel temperature is affected by engine conditions and the environment surrounding the engine. The diesel engine can predict the fuel temperature of the engine based on such information indicating the state of the engine and the environment around the engine.

  In a diesel engine in which fuel is used as lubricating oil, for example, fuel stored in an oil pan is supplied to each part of the engine that requires lubrication. The fuel supplied in this way becomes high temperature by cooling each part of the engine that has become high temperature by combustion. Thus, the fuel that has been used for lubrication and has reached a high temperature is returned to the oil pan. As a result, the fuel temperature in the oil pan rises, so the fuel temperature supplied to each part of the engine rises. Therefore, the diesel engine of the present invention can be configured to include torque control means for performing torque control of the engine based on the determination as to whether or not the predicted value of the fuel temperature reaches the upper limit temperature T. (Claim 3). By limiting the torque of the engine in this way, the amount of heat generated from the engine is reduced, so that the temperature increase of each part of the engine is suppressed and the increase in fuel temperature can be suppressed. As a result, an appropriate lubrication state of each part of the engine can be maintained, and engine failure can be avoided. Such torque limitation can be performed, for example, by reducing the fuel injection amount or narrowing the throttle opening.

  Such a diesel engine is based on a return path for returning the fuel after being supplied to each part of the engine as lubricating oil to the fuel tank, and whether or not the predicted value of the fuel temperature reaches the upper limit temperature T. It is possible to adopt a configuration comprising a distribution control means for distributing the fuel after being supplied to each part of the engine as lubricating oil to the return path (claim 4). With such a configuration, it is possible to improve the cooling effect of the fuel that has become high temperature in each part of the engine. The fuel that has reached a high temperature in each part of the engine flows through a fuel tank formed separately from the engine, so that it is easier to cool than when it is collected in an oil pan disposed in contact with the engine. In particular, the fuel tank is often mounted on the rear side of the vehicle with respect to the engine body mounted on the front side of the vehicle. For this reason, when a return path for returning the fuel used for lubrication from the engine body to the fuel tank is formed, the return path inevitably becomes long. Thereby, the cooling effect of the fuel returning to the fuel tank can be improved. Moreover, it can be expected that the fuel used for lubrication is cooled by being returned to the fuel tank having a larger capacity than the oil pan and mixed with a large amount of fuel. By cooling the fuel in this way, the temperature rise of the fuel supplied to each part of the engine is suppressed, and lubrication of each part of the engine can be maintained.

  Furthermore, such a diesel engine supplies torque control means for controlling the torque of the engine based on the determination as to whether or not the predicted value of the fuel temperature reaches the upper limit temperature T, and supplies it to each part of the engine as lubricating oil. The fuel after being supplied to each part of the engine as lubricating oil based on the return path for returning the fuel after the fuel is returned to the fuel tank and whether or not the predicted value of the fuel temperature reaches the upper limit temperature T And a distribution control means for distributing to a route. Thus, by restricting the torque, heat generation due to combustion can be suppressed, and by extending the return path, fuel cooling can be promoted, and an excessive increase in fuel temperature can be suppressed.

  The fuel temperature calculation device of the present invention is a fuel temperature calculation device that calculates a fuel temperature increase gradient based on information that affects the fuel temperature of the engine, and the information that affects the fuel temperature of the engine includes: And at least one of the outside air temperature, the remaining amount of fuel in the fuel tank, the rotational speed, the fuel injection amount, and the cooling water temperature, and the fuel temperature of the engine. Thereby, the fuel temperature calculation device can predict an increase in fuel temperature.

  The diesel engine of the present invention includes a determination means for calculating a predicted value of the fuel temperature based on information affecting the fuel temperature of the engine and determining whether the predicted value of the fuel temperature reaches the upper limit temperature T. By providing, it is possible to predict an excessive increase in the fuel temperature and to take measures for suppressing an excessive increase in the temperature of the fuel based on this prediction.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory diagram showing a schematic configuration of a fuel supply portion of a fuel lubricated diesel engine (hereinafter referred to as “engine”) 1 of the present embodiment. The engine 1 uses light oil as fuel, and includes a fuel tank 2 and an oil pan 3. The fuel tank 2 is mounted on the rear side of the vehicle with respect to the engine body mounted on the front side of the vehicle. The fuel tank 2 and the oil pan 3 communicate with each other through a fuel supply path 4. The fuel supply path 4 is provided with a cementer 5 and an electric supply pump 6, and fuel is supplied from the fuel tank 2 to the oil pan 3 by the electric supply pump 6. Here, although the oil pan 3 refers to what was integrally provided in the lower part of the cylinder block (not shown), a separate oil tank may be sufficient. Note that the capacity of the fuel tank 2 is larger than the capacity of the oil pan 3.

  The engine 1 has a lubricating system fuel supply path 8 that supplies fuel as lubricating oil to the engine parts 7 that need to be supplied with lubricating oil. The lubrication system fuel supply path 8 is provided with a filter 9 and a lubrication pump 10 capable of pumping fuel at a pressure of about 50 to 400 kPa. The lubrication pump 10 is driven to suck up the fuel from the oil pan 3. The engine is supplied to each part 7. Here, each part 7 of the engine refers to a portion that receives supply of engine oil in a conventional engine, such as around the cylinder head or the crankshaft of the engine 1.

  The engine 1 also has a first lubrication system fuel return path 11 that returns the fuel supplied to the engine parts 7 through the lubrication system fuel supply path 8 to the oil pan 3. The fuel tank side return path 19 is branched from the middle of the first lubrication system fuel return path 11. The fuel tank side return path 19 corresponds to the return path of the present invention, and is a path for returning the fuel supplied to each part 7 of the engine to the fuel tank 2. A three-way valve 18 is arranged at a branch point where the fuel tank return path 19 branches. The three-way valve 18 switches between a flow path to the oil pan 3 side and a flow path to the fuel tank 2 side according to a command signal from an ECU (Electronic Control Unit) 20.

  Furthermore, the engine 1 has an injection system fuel supply path 13 that supplies fuel to an injection system 12 that injects fuel into the cylinder. The injection system fuel supply path 13 is provided with a filter 14 and an injection pump 15 capable of pumping fuel at a high pressure of 10 MPa or more. By driving the injection pump 15, the fuel is sucked up from the oil pan 3 and injected. Supplying to the system 12.

  The engine 1 also has an injection system fuel return path 16 that returns the injection system return fuel that has been supplied to the injection system 12 through the injection system fuel supply path 13 to the fuel tank 2. The injection system return fuel refers to fuel returned from each of a supply pump (low pressure pump), a common rail, and a fuel injection valve (all not shown) provided integrally with the injection pump 15.

  Here, the position of the suction port 13 a of the injection system fuel supply path 13 located in the oil pan 3 is set to a position higher than the position of the suction port 8 a of the lubrication system fuel supply path 8. An oil level sensor 17 is attached to the oil tank 3.

  The engine 1 includes an ECU 20. The ECU 20 corresponds to a calculation means for calculating the predicted value of the fuel temperature according to the present invention and a determination means for comparing the predicted value of the fuel temperature with the upper limit temperature T. The ECU 20 is electrically connected to the oil level sensor 17, the remaining fuel sensor 21, the fuel temperature sensor 22, the crank angle sensor 24, and the outside air temperature sensor 25.

  The oil level sensor 17 detects the height of the oil surface in the oil pan 3. The remaining fuel sensor 21 calculates the remaining fuel amount Vf in the fuel tank 2. The fuel temperature sensor 22 is disposed downstream of the lubrication pump 10 in the lubrication system fuel supply path 8 and measures the fuel temperature Th in the lubrication system fuel supply path 8. The crank angle sensor 24 is mounted on a crankshaft (not shown) of the engine 1 and measures the engine speed Ne based on the rotation angle of the crankshaft. The outside air temperature sensor 25 measures an outside air temperature To outside the engine 1. Measurement values measured by these sensors are transmitted to the ECU 20.

  The ECU 20 is electrically connected to the electric supply pump 6. The ECU 20 determines an oil supply amount to the oil pan 3 based on information acquired from the oil level sensor 17 and other sensors, and transmits a discharge command signal to the electric supply pump 6.

  The ECU 20 is electrically connected to the injection system 12. The ECU 20 determines injection specifications in the injection system 12 based on information acquired from each sensor and sends an injection command signal to the injection system 12.

  Further, the ECU 20 is electrically connected to the three-way valve 18. The ECU 20 switches the three-way valve 18 based on information acquired from each sensor.

  Next, the control for suppressing the fuel temperature rise of the engine 1 configured as described above will be described with reference to FIG. FIG. 2 is a control flow for suppressing an increase in the fuel temperature of the engine 1. This control is performed by the ECU 20. First, in step S1, the ECU 20 acquires the fuel temperature Th, the outside air temperature To, the fuel remaining amount Vf, and the engine speed Ne from each sensor. Further, the fuel injection amount Q corresponding to the engine operating condition is calculated. When the ECU 20 acquires various types of information in step S1, the ECU 20 proceeds to step S2.

In step S2, the ECU 20 calculates the fuel temperature increase gradient ΔTh based on the various information acquired in step S1. The fuel temperature increase gradient ΔTh is calculated as the product of the correction coefficient k and the pre-correction fuel temperature increase gradient ΔTh ₀ as shown in the following formula (1).

ΔTh = k × ΔTh ₀ (1)

  Here, the correction coefficient k is a value used in consideration of the influence of the fuel temperature Th and the outside air temperature To on the increase of the fuel temperature. In general, the higher the fuel temperature Th and the outside air temperature To are, the lower the correction coefficient k is.

The pre-correction fuel temperature increase gradient ΔTh ₀ and the correction coefficient k are obtained from a map prepared in advance. Here, a map used to calculate the pre-correction fuel temperature increase gradient ΔTh ₀ and the correction coefficient k will be described. 3 and 4 are examples of maps used for calculating the pre-correction fuel temperature increase gradient ΔTh ₀ , and FIG. 5 is an example of maps used for calculating the correction coefficient k. FIG. 3 is a first map for calculating a heat generation amount Qf due to combustion of the engine 1 based on the engine speed Ne and the fuel injection amount Q. FIG. 4 is a second map for calculating the pre-correction fuel temperature increase gradient ΔTh ₀ based on the calorific value Qf and the remaining fuel amount Vf calculated in FIG. FIG. 5 is a third map for calculating the correction coefficient k based on the fuel temperature Th and the outside air temperature To.

  The ECU 20 uses the first map shown in FIG. 3 to calculate the heat generation amount Qf of the engine 1 based on the engine speed Ne and the fuel injection amount Q acquired in step S1. That is, the measured value of the engine speed Ne and the measured value of the fuel injection amount Q are collated with the first map, and the heat generation amount Qf is determined. For example, when the engine speed Ne is 2000 and the fuel injection amount Q is 20, the heat generation amount Qf is Qf5.

Next, the ECU 20 uses the second map shown in FIG. 4 to calculate the pre-correction fuel temperature increase gradient ΔTh ₀ based on the calculated calorific value Qf and the remaining fuel amount Vf acquired in step S1. . That is, the calculated value of the calorific value Qf and the measured value of the remaining fuel amount Vf are collated with the second map, and the pre-correction fuel temperature increase gradient ΔTh ₀ is determined. For example, in the map of FIG. 4, when the calorific value Qf is Qf3 and the fuel remaining amount Vf is V2, the pre-correction fuel temperature increase gradient ΔTh ₀ is a9.

  Next, the ECU 20 calculates the correction coefficient k based on the fuel temperature Th and the outside air temperature To acquired in step S1, using the third map shown in FIG. That is, the measured value of the fuel temperature Th and the measured value of the outside air temperature To are collated with the third map, and the correction coefficient k is determined. For example, in the map of FIG. 5, when the fuel temperature Th is Th3 and the outside air temperature To is To2, the correction coefficient is k7.

Based on the pre-correction fuel temperature increase gradient ΔTh ₀ calculated in this way and the correction coefficient k, the temperature increase gradient ΔTh is calculated. If ECU20 calculates fuel temperature rise gradient (DELTA) Th in step S2, it will complete | finish the process of step S2 and will progress to step S3.

  In step S3, the ECU 20 calculates a predicted value Tp of the fuel temperature after the elapse of time t based on the fuel temperature increase gradient ΔTh calculated in step S2.

  FIG. 6 is an explanatory diagram showing the relationship between the fuel temperature predicted by the ECU 20 and time. The vertical axis in FIG. 6 represents the predicted fuel temperature, and the horizontal axis represents the elapsed time since the fuel temperature Th was measured in step S1. The slope of the straight line shown in FIG. 6 represents the fuel temperature increase gradient ΔTh calculated in step S2. That is, the fuel temperature is predicted to increase at a fuel temperature increase gradient ΔTh per unit time. The ECU 20 calculates the predicted value Tp of the fuel temperature after the elapse of time t from the measurement of the fuel temperature Th based on the straight line shown in FIG. This time t is determined in advance according to the specifications and operating conditions of the engine 1. Such a time t is set shorter when the engine 1 is operated with a high load than when the engine 1 is operated with a low load and a medium load. In this way, a rapid increase in fuel temperature at high load is taken into account. When the ECU 20 calculates the predicted fuel temperature Tp in step S3, the ECU 20 finishes the process of step S3, and then proceeds to step S4.

  In step S4, the ECU 20 determines whether or not the predicted fuel temperature value Tp calculated in step S3 reaches the upper limit temperature T. This upper limit temperature T is determined in advance according to the specifications of the engine 1 and the operating conditions. If the determination here is Yes, that is, if the predicted value of the fuel temperature after the elapse of time t reaches the upper limit temperature T, the process proceeds to step S5.

  In step S <b> 5, the ECU 20 limits the torque of the engine 1. Here, the engine 1 limits the torque by decreasing the fuel injection amount. That is, the ECU 20 sends a command signal so as to decrease the fuel injection amount in the injection system 12. Thereby, the emitted-heat amount of the engine 1 reduces and the raise of fuel temperature is suppressed. Further, instead of reducing the fuel injection amount, the throttle opening may be narrowed to limit the torque. After executing the torque limitation in step S5, the ECU 20 proceeds to step S6.

  In step S <b> 6, the ECU 20 performs control to collect the fuel used for lubrication in each part 7 of the engine into the fuel tank 2. That is, the ECU 20 switches the three-way valve 18. Thus, the fuel used for lubrication in each engine part 7 flows into the fuel tank return path 19 and is returned to the fuel tank 2.

  By the way, it is conceivable that impurities used for lubrication in the engine parts 7 are mixed with impurities when passing through the engine parts 7. If the engine 1 of the present embodiment returns to the oil pan 3 in which the suction port 13a of the injection system fuel supply path 13 is disposed, the fuel mixed with such impurities can be consumed at an early stage. However, when the fuel temperature is predicted to reach the upper limit temperature T, the fuel temperature is caused to flow into the fuel tank return path 19 and recovered to the fuel tank 2. The engine parts 7 that are lubricated are arranged on the front side of the vehicle, whereas the fuel tank 2 is mounted on the rear side of the vehicle, so that the fuel tank return path 19 becomes longer. Thereby, the cooling effect of the fuel returned to the fuel tank 2 increases. In addition, it is expected that the fuel is cooled by being returned to the fuel tank 2 having a larger capacity than the oil pan 3 and mixed with a large amount of fuel. As described above, when the fuel temperature is predicted to reach the upper limit temperature T, the engine 1 prioritizes cooling of the fuel temperature over rapid consumption of the fuel used for lubrication, and suppresses an increase in the fuel temperature. The fuel tank side return path 19 may be provided with a cooling device to cool the fuel flowing through the fuel tank side return path 19.

  When the ECU 20 changes the flow path of the three-way valve 18 in step S6, the ECU 20 finishes the process and returns. By the way, if the determination in step S4 is No, that is, if the predicted value of the fuel temperature after the elapse of time t does not reach the upper limit temperature T, the process proceeds to step S7.

  In step S7, the ECU 20 releases the torque limitation of the engine 1. Thereby, the fuel can be supplied to the fuel system 12 without any restriction. When the ECU 20 cancels the torque limitation in step S7, the ECU 20 then proceeds to step S8.

  In step S <b> 8, the ECU 20 collects the fuel used for lubrication in each part 7 of the engine into the oil pan 3. As a specific process, the ECU 20 causes the three-way valve 18 to form a flow path that allows the engine parts 7 and the oil pan 3 to communicate with each other. Thereby, the fuel collected from each part 7 of the engine is returned to the oil pan 3. In this way, the fuel used for lubrication in each engine part 7 is supplied from the oil pan 3 to the injection system 12 and consumed at an early stage. When the ECU 20 changes the flow path of the three-way valve 18 in step S8, the process returns.

  As described above, the engine 1 according to the present embodiment is based on the fuel temperature Th, the outside air temperature To, the fuel remaining amount Vf, the engine speed Ne, and the fuel injection amount Q acquired from each sensor disposed in the engine 1. Thus, the fuel temperature increase gradient ΔTh is calculated. From this fuel temperature rise gradient ΔTh, a predicted value Tp of the fuel temperature after t seconds from the measurement of the fuel temperature is calculated, and it is determined whether or not this predicted value Tp reaches the upper limit temperature T. Based on this determination result, the engine 1 limits the torque of the engine 1 by reducing the fuel injection amount when the predicted value Tp reaches the upper limit temperature T. Further, the fuel used for lubrication is collected in the fuel tank 2 and cooled. As a result, an excessive increase in the fuel temperature is suppressed, and an appropriate lubrication state of each part 7 of the engine is maintained, so that failure of the engine 1 can be avoided.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention. It is apparent from the above description that various other embodiments are possible within the scope.

  For example, in the control flow for suppressing the increase in the fuel temperature of the engine 1, only one of step S5 and step S6 may be performed. That is, when it is determined that the predicted value Tp of the fuel temperature reaches the upper limit temperature T, a configuration including a control that performs only torque limitation may be used. Alternatively, only control for switching the three-way valve 18 may be performed.

  Further, the fuel-lubricated diesel engine of the present invention may be configured to determine that the predicted fuel temperature value Tp reaches the upper limit temperature T, limit the engine torque, and notify the driver that the torque is limited.

  In addition, in order to calculate the temperature rise gradient ΔTh, information that affects the fuel temperature of the engine, such as the coolant temperature, can be added to the information of the engine 1 acquired from each sensor.

It is explanatory drawing which showed schematic structure of the fuel supply part of the engine of an Example. This is a control flow for suppressing an increase in engine fuel temperature. It is a map which calculates the emitted-heat amount by engine combustion based on an engine speed and fuel injection amount. FIG. 5 is a map for calculating a pre-correction fuel temperature increase gradient based on the amount of heat generated by the engine and the remaining amount of fuel. It is a map which calculates a correction coefficient based on fuel temperature and outside temperature. It is explanatory drawing which showed the relationship between the fuel temperature estimated in ECU, and time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Fuel tank 3 Oil pan 7 Engine parts 8 Lubrication system fuel supply path 10 Lubrication pump 11 Lubrication system return path 12 Injection system 16 Injection system return fuel 17 Oil level sensor 18 Three-way valve 19 Fuel tank side return path 20 ECU
21 Fuel level sensor 22 Fuel temperature sensor 24 Crank angle sensor 25 Outside air temperature sensor

Claims (6)

A diesel engine in which the fuel is used as a lubricant,
A calculation means for calculating a predicted value of the fuel temperature based on information affecting the fuel temperature of the engine;
A diesel engine comprising a judging means for judging whether or not the predicted value of the fuel temperature reaches an upper limit temperature T. The diesel engine according to claim 1, wherein
The diesel engine characterized in that the information affecting the fuel temperature of the engine includes at least one of an outside air temperature, a remaining amount of fuel in the fuel tank, an engine speed, and a fuel injection amount, and a fuel temperature. The diesel engine according to claim 1, wherein
A diesel engine comprising torque control means for performing torque control of the engine based on determination of whether or not the predicted value of the fuel temperature reaches the upper limit temperature T. The diesel engine according to claim 1, wherein
A return path for returning the fuel after being supplied to each part of the engine as lubricating oil to the fuel tank;
Based on the determination whether the predicted value of the fuel temperature reaches the upper limit temperature T, distribution control means for distributing the fuel after being supplied to each part of the engine as lubricating oil to the return path;
Diesel engine characterized by comprising The diesel engine according to claim 1, wherein
Torque control means for performing torque control of the engine based on determination of whether the predicted value of the fuel temperature reaches the upper limit temperature T;
A return path for returning the fuel after being supplied to each part of the engine as lubricating oil to the fuel tank;
Based on the determination whether the predicted value of the fuel temperature reaches the upper limit temperature T, distribution control means for distributing the fuel after being supplied to each part of the engine as lubricating oil to the return path;
Diesel engine characterized by comprising A fuel temperature calculation device that calculates a fuel temperature rise gradient based on information that affects the fuel temperature of an engine,
The information affecting the fuel temperature of the engine includes at least one of the outside air temperature, the fuel remaining amount in the fuel tank, the rotational speed, the fuel injection amount, the cooling water temperature, and the fuel temperature of the engine. Temperature calculation device.

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