Patent Application
20150330273
The present application claims the benefit of priority to Korean Patent Application Number 10-2014-0059128 filed on May 16, 2014, the entire contents of which application are incorporated herein for all purposes by this reference.
The present inventive concept relates generally to techniques for diagnosing bypass valves on oil cooling circuits for vehicles and, more particularly, to a method and apparatus for diagnosing a bypass valve on an oil cooling circuit for vehicles which compares the temperature of oil with a limit temperature, at which the bypass valve must be opened or closed, and is able to rapidly and accurately diagnose failure in the bypass valve.
Generally, vehicles are provided with an oil pump to use oil for use in lubrication, cooling, washing, and rust prevention of an engine. The oil pump draws oil from an oil pan containing oil and supplies it to elements requiring the use of oil at a predetermined flow rate and pressure.
Cooling oil using cooling water, an oil cooler is installed between the oil pump and an oil filter. Furthermore, a bypass valve is provided to divert the flow of oil, which is supplied to the oil cooler, depending on the temperature of the oil.
That is, under low-temperature oil conditions, for example, at an initial ignition stage, oil flows with high viscosity. Given this, to prevent power loss caused by mechanical friction of an engine, the bypass valve is actively controlled in such a way that it opens so that oil pumped by the oil pump flows to the engine without passing through the oil cooler whereby the oil can be rapidly warmed up.
On the other hand, under high-temperature oil conditions, the bypass valve is actively controlled in such a way that it is closed so that oil supplied from the oil pump passes through the oil cooler and is thus cooled by heat exchange in the oil cooler.
However, the conventional oil cooler bypass valve is problematic in that, when the bypass valve malfunctions and stops in an open or closed state, it is difficult to accurately diagnose the failure state of the bypass valve.
However, if a vehicle moves under low-speed and low-load conditions in which the temperature of oil is relatively low, it is difficult to sense an open stuck state of the bypass valve because of a low oil temperature.
In other words, even if an open stuck failure has occurred, only when the vehicle moves under high-speed and high-load conditions can the open stuck failure be sensed. Therefore, the open stuck failure cannot be easily sensed despite the fact that if the vehicle moves in the failure state, fuel efficiency of the vehicle is markedly exacerbated.
The foregoing is intended merely to aid in the understanding of the background of the present inventive concept, and is not intended to mean that the present inventive concept falls within the purview of the related art that is already known to those skilled in the art.
An object of the present disclosure is to rapidly and accurately diagnose failure in the bypass valve.
In order to accomplish the above object, in an aspect, the present disclosure provides a method for diagnosing a bypass valve on an oil cooling circuit for vehicles, including: measuring a temperature of oil downstream of the bypass valve; a prediction step of comparing the downstream oil temperature with an opening reference temperature or a closing reference temperature and predicting an open or closed state of the bypass valve; and a diagnosis step of, depending on a result of the prediction step, comparing the downstream oil temperature with a lowest reference temperature or a highest reference temperature and diagnosing whether the bypass valve is in a failure state in which the bypass valve is stuck in an open or closed state.
In certain embodiments, the lowest and highest reference temperatures may be determined from output variables reflecting a driving state and driving conditions of the vehicle.
In the prediction step, when the downstream oil temperature is less than or equal to the opening reference temperature of the bypass valve, the bypass valve is predicted as being in an open state, and when the downstream oil temperature is higher than the closing reference temperature of the bypass valve, the bypass valve is predicted as being in a closed state.
In the diagnosis step, when the downstream oil temperature is less than or equal to the opening reference temperature and is less than or equal to the lowest reference temperature, the bypass valve is diagnosed as being in a failure state in which the bypass valve is stuck in a closed state.
In the diagnosis step, when the downstream oil temperature is higher than both the closing reference temperature and the highest reference temperature, the bypass valve is diagnosed as being in a failure state in which the bypass valve is stuck in an open state.
In another embodiment, the present inventive concept may provide a method for diagnosing a bypass valve on an oil cooling circuit for vehicles, including: measuring a temperature of oil downstream of the bypass valve and a temperature of oil upstream of the bypass valve; a prediction step of comparing the downstream oil temperature with an opening reference temperature or a closing reference temperature, and predicting an open or closed state of the bypass valve; and a diagnosis step of, depending on a result of the prediction step, comparing a difference between the downstream oil temperature and the upstream oil temperature with a lowest limit value or a highest limit value of a difference between the downstream oil temperature and the upstream oil temperature, and diagnosing whether the bypass valve is in a failure state in which the bypass valve is stuck in an open or closed state.
In the prediction step, when the downstream oil temperature is the opening reference temperature of the bypass valve or less, the bypass valve is predicted as being in an open state, and when the downstream oil temperature is higher than the closing reference temperature of the bypass valve, the bypass valve is predicted as being in a closed state.
In the diagnosis step, when the downstream oil temperature is less than or equal to the opening reference temperature, and the difference between the downstream oil temperature and the upstream oil temperature is less than or equal to the lowest limit value, the bypass valve is diagnosed as being in a failure state in which the bypass valve is stuck in a closed state.
In the diagnosis step, when the downstream oil temperature is higher than the closing reference temperature, and the difference between the downstream oil temperature and the upstream oil temperature is higher than the highest limit value, the bypass valve is diagnosed as being in a failure state in which the bypass valve is stuck in an open state.
In certain embodiments, the lowest and highest limit values may be determined from output variables reflecting a driving state and driving conditions of the vehicle. The output variables may include an RPM of an engine, a load of the engine, a temperature of cooling water and a temperature of outdoor air.
In a further aspect, the present inventive concept may provide an apparatus for a bypass valve on an oil cooling circuit for vehicles, including: a temperature sensor configured to measure a temperature of oil downstream of the bypass valve; and a controller which may be configured to compare the downstream oil temperature with an opening reference temperature or a closing reference temperature for opening or closing the bypass valve, predict an open or closed state of the bypass valve; compare, depending on the result of the prediction step, the downstream oil temperature with a lowest reference temperature and a highest reference temperature and diagnose whether the bypass valve is in a failure state in which the bypass valve is stuck in an open or closed state. In an embodiment, the lowest and highest reference temperatures may be determined from output variables reflecting a driving state and driving conditions of the vehicle.
In a still another aspect, the present inventive concept provides an apparatus for a bypass valve on an oil cooling circuit for vehicles, including: a first temperature sensor and a second temperature sensor respectively measuring a temperature of oil downstream of the bypass valve and a temperature of oil upstream of the bypass valve; and a controller which is configured to compare the downstream oil temperature with an opening reference temperature or a closing reference temperature, predict an open or closed state of the bypass valve; compare, depending on the result of the prediction step, a difference between the downstream oil temperature and the upstream oil temperature with lowest or highest limit values of a difference between the downstream oil temperature and the upstream oil temperature, and diagnose whether the bypass valve is in a failure state in which the bypass valve is stuck in an open or closed state. In certain embodiments, the the lowest and highest limit values may be determined from output variables reflecting a driving state and driving conditions of the vehicle.
The above and other objects, features and advantages of the present inventive concept will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
Hereinafter, preferred embodiments of the present inventive concept will be described in detail with reference to the attached drawings.
The method for diagnosing a bypass valve on an oil cooling circuit for vehicles according to the present inventive concept includes a measurement step, a prediction step and a diagnosis step.
Referring to
As shown in
A bypass passage and the bypass valve 3 are provided on a passage along which oil is supplied to the oil cooler 1. The bypass valve 3 can be controlled such that it is opened or closed depending on the temperature of oil which is measured downstream of the bypass valve 3. In an embodiment, the bypass valve 3 may be an oil thermostat.
A failure state in which the bypass valve 3 is stuck in an open or closed state can be rapidly and accurately diagnosed by comparing the temperature of oil measured downstream of the bypass valve 3 both with the reference temperature at which the bypass valve 3 must be opened or closed and with highest and lowest limit temperatures reflecting the driving state of the vehicle. Therefore, fuel loss which is caused when the vehicle moves in a failure state can be reduced.
In the prediction step, when the downstream oil temperature is less than or equal to an opening reference temperature of the bypass valve 3, the bypass valve 3 is predicted as being in an open state. When the downstream oil temperature is higher than a closing reference temperature of the bypass valve 3, the bypass valve 3 is predicted as being in a closed state.
The opening reference temperature may be a reference temperature at which the bypass valve 3 is completely opened. The closing reference temperature may be a reference temperature at which the bypass valve 3 is completely closed. Of course, the opening reference temperature is set as a temperature lower than the closing reference temperature.
That is, when the downstream oil temperature is the opening reference temperature or less, the bypass valve 3 must be open to prevent oil from being supplied to the oil cooler 1 and cooled by it. Thus, on the assumption that the bypass valve 3 is normally operated, the bypass valve 3 under the above conditions is predicted as being in an open state.
On the contrary, when the downstream oil temperature is greater than the opening reference temperature, the bypass valve 3 must be closed to supply oil to the oil cooler 1 and cool the oil. Hence, in this case, on the assumption that the bypass valve 3 is normally operated, the bypass valve 3 is predicted as being in a closed state.
Particularly, as shown in
In other words, when the downstream oil temperature is a low temperature at which the bypass valve 3 must be open, if the bypass valve 3 is normally operated, the bypass valve 3 must be open so that oil bypasses the oil cooler 1. However, if the downstream oil temperature is measured as being the lowest reference temperature or less determined reflecting the driving state of the vehicle, oil is determined as being still cooled by the oil cooler 1. Therefore, the bypass valve 3 is diagnosed as being in a failure state in which it is stuck in a closed state rather than being open.
Furthermore, in the diagnosis step, when the downstream oil temperature is higher both than the opening reference temperature and than the highest reference temperature, the bypass valve 3 is diagnosed as being in a failure state in which it is stuck in an open state.
That is, when the downstream oil temperature is a high temperature at which the bypass valve 3 must be closed, if the bypass valve 3 is normally operated, the bypass valve 3 must be closed so that oil is supplied to the oil cooler 1 and thus cooled by the oil cooler 1. However, if the downstream oil temperature is measured as being higher than the highest reference temperature determined reflecting the driving state of the vehicle, oil is determined as still bypassing the oil cooler 1 rather than being supplied to the oil cooler 1. Therefore, the bypass valve 3 is diagnosed as being in a failure state in which it is stuck in an open state rather than being closed.
Hereinafter, a second embodiment of a method for diagnosing a bypass valve 3 according to the present inventive concept will be described with reference to
As shown in
A bypass passage and the bypass valve 3 are provided on a passage along which oil is supplied to the oil cooler 1. The bypass valve 3 can be controlled such that it is opened or closed depending on the temperatures of oil which are measured upstream and downstream of the bypass valve 3. In an embodiment, the bypass valve 3 may be an oil thermostat.
A failure state in which the bypass valve 3 is stuck in an open or closed state can be rapidly and accurately diagnosed both by comparing the temperature of oil measured downstream of the bypass valve 3 with the reference temperature at which the bypass valve 3 must be opened or closed and by comparing a difference between oil temperatures measured downstream and upstream with highest and lowest limit values reflecting the driving state of the vehicle. Therefore, fuel loss which is caused when the vehicle moves in a failure state can be reduced.
In the prediction step, when the downstream oil temperature is an opening reference temperature of the bypass valve 3 or less, the bypass valve 3 is predicted as being in an open state. When the downstream oil temperature is higher than a closing reference temperature of the bypass valve 3, the bypass valve 3 is predicted as being in a closed state.
Here, the opening reference temperature may be a reference temperature at which the bypass valve 3 is completely opened. The closing reference temperature may be a reference temperature at which the bypass valve 3 is completely closed. Of course, the opening reference temperature is set as a temperature lower than the closing reference temperature.
Particularly, as shown in
In other words, when the downstream oil temperature is a low temperature at which the bypass valve 3 must be open, if the bypass valve 3 is normally operated, the bypass valve 3 must be open so that oil bypasses the oil cooler 1. However, if the difference value between the downstream oil temperature and the upstream oil temperature is measured as being the lowest limit value determined reflecting the driving state of the vehicle or less, oil is determined as being still cooled by the oil cooler 1. Therefore, the bypass valve 3 can be diagnosed as being in a failure state in which it is stuck in a closed state rather than being open.
In the diagnosis step, when the downstream oil temperature is higher than the opening reference temperature, and the difference value between the downstream oil temperature and the upstream oil temperature is higher than the highest limit value, the bypass valve 3 is diagnosed as being in a failure state in which it is stuck in an open state.
That is, when the downstream oil temperature is a high temperature at which the bypass valve 3 must be closed, if the bypass valve 3 is normally operated, the bypass valve 3 must be closed so that oil is supplied to the oil cooler 1 and thus cooled by the oil cooler 1. However, if a difference value between the downstream oil temperature and the upstream oil temperature is measured as being higher than the highest limit value determined reflecting the driving state of the vehicle, oil is determined as still bypassing the oil cooler 1 rather than being supplied to the oil cooler 1. Therefore, the bypass valve 3 is diagnosed as being in a failure state in which it is stuck in an open state rather than being closed.
Furthermore, the output variables may be the RPM of an engine, the load of the engine, the temperature of cooling water and the temperature of the air. The lowest reference temperature, the highest reference temperature, the lowest limit value and the highest limit value can be determined using a table or map to which the output variables are input.
Referring to
Referring to
The first temperature sensor 5 may be disposed on the circuit before a main gallery downstream of the oil cooler. The second temperature sensor 7 may be disposed on the circuit upstream of the oil cooler including an oil pan.
As described above, in the present inventive concept, a failure state in which a bypass valve is stuck in an open or closed state can be rapidly and accurately diagnosed by comparing the temperature of oil measured downstream of the bypass valve both with a reference temperature at which the bypass valve must be opened or closed and with highest and lowest limit temperatures reflecting the driving state of the vehicle. Therefore, fuel loss which is caused when the vehicle moves in a failure state can be reduced.
Although the preferred embodiments of the present inventive concept have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the inventive concept as disclosed in the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2014-0059128 | May 2014 | KR | national |
