JP2000303839A - Cooling control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely detect failures of an electric water pump provided on an engine and to prevent damage of the engine due to overheat. SOLUTION: A closed cooling water circuit, connecting a water jacket J of an engine E to a radiator R, is provided with an electric thermostat T constituting the cooling water circuit when opening a valve and constituting a bypass circuit, which does pass the radiator R when closing the valve and an electric water pump P for circulating cooling water. A power value is calculated from a current (i) and a voltage (v) of an electric motor 12 of the electric water pump P. When failures such as short circuiting and disconnection is determined to have occurred, when this power value is at the outside of a prescribed range and a mode is transferred to a fail-safe mode so as to prevent damage to the engine E.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine cooling control device for controlling the opening of an electric thermostat and the number of revolutions of an electric water pump by control means.

[0002]

2. Description of the Related Art In general, a water pump for circulating cooling water through a closed cooling water circuit connecting a water jacket and a radiator of an engine is connected to and driven by a crankshaft of the engine. The thermostat constituting the bypass circuit that bypasses the radiator to promote warm-up during the cold period uses a thermo-wax that responds to the temperature of the cooling water as a driving source.

In such a conventional cooling control apparatus for an engine equipped with a water pump and a thermostat, the rotation speed of the water pump is uniquely determined by the engine rotation speed, and the opening of the thermostat is uniquely determined by the temperature of the cooling water. Therefore, it was not possible to precisely control the rotation speed of the water pump and the opening of the thermostat.

On the other hand, the water pump can be driven by an electric motor to control the number of rotations arbitrarily.
Japanese Patent Application Laid-Open No. 5-231 discloses an engine cooling control device which is capable of arbitrarily controlling the flow rate of cooling water passing through a radiator by electrically changing the opening of a thermostat.
148 and JP-A-5-231149.

[0005]

By the way, according to the above-mentioned publication, even if the electric water pump fails for some reason and an abnormality occurs in the circulation of the cooling water, the failure can be reliably detected. Since the cooling water temperature could not be increased, the engine could be damaged.

The present invention has been made in view of the above circumstances, and has as its object to reliably detect a failure of an electric water pump provided in an engine and prevent damage to the engine.

[0007]

According to the first aspect of the present invention, there is provided a closed cooling water circuit for connecting a water jacket and a radiator of an engine, wherein the cooling is performed when a valve is opened. An electric thermostat that constitutes a water circuit and constitutes a bypass circuit that does not pass through the radiator when the valve is closed, and an electric water pump that circulates cooling water are provided, and the control means controls the opening of the electric thermostat and the rotation speed of the electric water pump. In the engine cooling control device to be controlled, the control means calculates a power value of the electric water pump based on a current and a voltage of the electric motor of the electric water pump, and detects a failure of the electric water pump based on the power value. A cooling control device for an engine is proposed.

According to the above configuration, by monitoring the power value calculated from the current and the voltage of the electric motor of the electric water pump, it is possible to reliably detect a failure such as a short circuit or disconnection of the drive system of the electric water pump. Can be.

According to the invention described in claim 2,
In addition to the configuration of claim 1, an engine cooling control device is proposed in which the control means calculates the power value as an average power value for a short time.

According to the above configuration, the electric power value of the electric motor of the electric water pump is calculated as an average electric power value for a short period of time. And the failure of the electric water pump can be detected with higher accuracy.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on embodiments of the present invention shown in the accompanying drawings.

1 to 4 show an embodiment of the present invention. FIG. 1 is a view for explaining the overall structure of an engine cooling system.
FIG. 2 is an explanatory view of the operation in a cold state corresponding to FIG. 1, FIG. 3 is a longitudinal sectional view of the electric thermostat, and FIG. 4 is a flowchart of a failure detection routine of the electric water pump.

First, based on the schematic diagram of FIG.
The overall structure of the cooling system will be described.

The engine E has a water jacket J surrounding the outer periphery of a cylinder bore formed in a cylinder block and the outer periphery of a combustion chamber formed in a cylinder head.
A radiator R is provided to cool the cooling water that has passed through the water jacket J and has increased in temperature. With the upper part of the downstream end and the radiator R of the water jacket J is connected with the radiator upper hose h _1, and the upstream end of the lower and the water jacket J of the radiator R are connected by the radiator lower hose h _2, the radiator lower hose h ₂ , An electric thermostat T and an electric water pump P are provided. And the downstream end of the electric thermostat T and the water jacket J is connected in the bypass hose h _3. The heater hose h ₄ connecting the downstream end of the radiator lower hose h ₂ and water jacket J, the heater core H and the on-off valve V for heating is provided.

The electric thermostat T uses a linear solenoid 11 as a driving source unlike a general thermostat using thermowax as a driving source, and its opening degree can be continuously changed. Electric water pump P
Unlike the general water pump that uses the crankshaft of the engine E as a drive source, the impeller 13 is driven to rotate by using the electric motor 12 as a drive source, and the number of revolutions can be continuously changed.

The electronic control unit U has a water jacket
Cooling water in the water jacket J
Cooling water temperature sensor S for detecting temperature Tw₁Signal from
And the rotation speed N of the electric water pump P (the electric motor 12
Rotation speed sensor S for detecting the rotation speed of the pump)_TwoFaith from
And a current sensor S for detecting the current i of the electric motor 12
_ThreeAnd a voltage for detecting the voltage v of the electric motor 12.
Pressure sensor S_FourIs input. Electronic control uni
U is an electric thermos based on the cooling water temperature Tw.
The opening of the tut T and the rotation speed of the electric water pump P
Control, the cooling water temperature Tw, the pump speed
Electric water pump based on N, current i and voltage v
Determines the failure of P and turns on the warning lamp 14 when a failure occurs
Warnings and reduce overheating.
The fuel injection control device 1
5, the fuel injection amount of the engine E is enriched.

Next, the structure of the electric thermostat T will be described with reference to FIG.

The electric thermostat T includes a first housing 16 connected to the lower portion of the radiator R via the upstream half portion of the radiator lower hose h _2, radiator lower hose h
And a second housing 17 connected to the downstream end of the water jacket J through the bypass hose h ₃ together connected to the electric water pump P through the downstream half of the _2.
A first valve seat 18 is formed in the first housing 16, and a plurality of support arms 19 extending in a conical manner from the periphery of the first valve seat 18 toward the inside of the first housing 16 are provided with a first valve seat 18. The second housing 17 extends through the center of one valve seat 18.
A guide rod 20 protruding into the inside is fixed. Second
At the entrance of the bypass hose h ₃ which opens into the housing 17, the second valve seat 21 is formed so as to be positioned coaxially of the guide rod 20.

The guide rod 20 has a linear solenoid 1
1 is slidably supported, and a first valve body 23 and a second valve body 24 are integrally provided on a holder 22 holding the linear solenoid 11 therein. A first valve seat 18,
The first valve element 23 which can be seated thereon constitutes a cooling water flow control valve 25, and the second valve element 21 and the second valve element 24 which can be seated thereon constitute a bypass valve 26. . Spring seat 27 fixed inside second housing 17
A compressed valve spring 28 is mounted between the first valve body 23 and the first valve body 23, and the first valve body 23 of the cooling water flow control valve 25 is connected to the first valve seat 18 by the elastic force of the valve spring 28. The second valve body 24 of the bypass valve 26 is biased in the direction of seating on the second valve seat 2.
It is urged in a direction away from 1.

Therefore, when the linear solenoid 11 is in the non-excited state, the holder 22 moves leftward in the drawing due to the resiliency of the valve spring 28, and the first valve body 23 is seated on the first valve seat 18, The cooling water flow control valve 25 is closed, the second valve body 24 is separated from the second valve seat 21, and the bypass valve 26 is opened. Conversely, when the linear solenoid 11 is in the excited state, the holder 22 moves rightward in the drawing against the elastic force of the valve spring 28 as shown by the chain line, and the first valve body 23 The cooling water flow control valve 25 is opened apart from the first valve seat 18, the second valve body 24 is seated on the second valve seat 21, and the bypass valve 26 is closed.

When the cooling water temperature Tw detected by the cooling water temperature sensor S ₁ is low, for example, in a cold state immediately after the start of the engine E, the linear solenoid 11 of the electric thermostat T is commanded by the electronic control unit U. Is in the non-excited state shown in FIG. 3, the cooling water flow control valve 25 is closed, and the bypass valve 26 is opened. As a result, as shown in FIG. 2, the radiator lower hose h ₂ leading to the outlet of the radiator R are closed, the circuit in which the cooling water passing through the radiator R is interrupted. Therefore, the cooling water supplied from the electric water pump P to the water jacket J of the engine E is:
Without flowing into the radiator R via the radiator upper hose h _1, the bypass hose h ₃ from the downstream end of the water jacket J, via the bypass valve 26 and the radiator lower hose h ₂ was opened to reflux the electric water pump P. In this way, by circulating the cooling water that has passed through the water jacket J and raised in temperature without passing through the radiator R, the warm-up operation of the engine E can be promoted. Also, while the cooling water temperature is particularly low, the operation of the electric water pump P is stopped, and the water jacket J is stopped.
The warm-up operation of the engine E is further effectively promoted by retaining the cooling water in the inside.

When the engine E is warm after the warm-up operation is completed,
Is an electric thermostat by a command from the electronic control unit U.
T, the linear solenoid 11 becomes excited,
The cooling water flow control valve 25, which had been closed at
, The bypass valve 26 that has been opened closes. as a result,
As shown in FIG. 1, a radiator connected to the outlet of the radiator R
-Taro lower hose h_TwoIs opened and the cooling water is supplied to the radiator R
Is formed. Therefore, the electric water tap
Pump P supplied to water jacket J of engine E
Cooled water is supplied to the bypass hose h_ThreeDo not flow into
Radiator up from the downstream end of water jacket J
Parkose h₁, Radiator R, radiator lower hose
h_Two, Opened cooling water flow control valve 25 and radiator
Lower hose _TwoTo the electric water pump P via
You. After passing through the water jacket J
Cooling the raised cooling water by passing it through the radiator R
Operation to maintain the temperature of the engine E properly
Can be made possible.

Next, failure detection of the electric water pump P will be described with reference to FIG.

First, at step S1, the cooling water temperature sensor S
Detects the coolant temperature Tw within the water jacket J _1, pump speed in the pump rotational speed sensor S ₂ N
Is detected, and if the cooling water temperature Tw and the pump speed N are both stable at step S2,
In 3, the current i and the voltage v of the electric motor 12 are detected by the current sensor S ₃ and the voltage sensor S ₄ , and in step S 4, the power obtained by multiplying the current i and the voltage v is integrated by a predetermined minute unit time. To calculate a power value w. If the power value w is not between the lower limit value A and the upper limit value B in step S5, it is determined that some trouble has occurred in the electric water pump P.

When it is determined that the electric water pump P has failed in this way, the warning lamp 14 is turned on by a command from the electronic control unit U in step S6 to issue a warning to the driver, and in step S8 the overheat is started. Enter fail-safe mode to avoid occurrence. In the fail-safe mode, the fuel injection amount of the engine E is enriched through the fuel injection amount control device 15 by a command from the electronic control unit U, thereby preventing damage to the engine E due to overheating.

If the power value w calculated in step S5 is equal to or less than the lower limit value A, a failure such as disconnection of the electric circuit of the electric motor 12 is considered. If the power value w is equal to or more than the upper limit value B, Failures such as short-circuiting of the electric circuit of the electric motor 12 and sticking of the impeller 13 of the electric water pump P are considered.

The power value w is not calculated as a simple product of the current i and the voltage v (ie, an instantaneous power value), but is calculated as an integral value (ie, an average power value) in a minute unit time, so that the load is calculated. The effect of the instantaneous change in the number of revolutions of the electric motor 12 and the effect of electric noise due to the fluctuation of the electric motor 12 can be removed, and the failure of the electric water pump P can be detected with higher accuracy.

As described above, the failure of the electric water pump P can be reliably detected by monitoring the current i and the voltage v of the electric motor 12 of the electric water pump P. In addition, when the failure of the electric water pump P is detected, a warning is issued to the driver, and the fuel injection amount is enriched by entering the fail-safe mode. Therefore, damage to the engine E due to overheating can be avoided.

Although the embodiments of the present invention have been described in detail, various design changes can be made in the present invention without departing from the gist thereof.

For example, in the embodiment, the electric water pump P
Although the power value w of the electric motor 12 is calculated as the average power value, it can be calculated as an instantaneous power value (a simple product of the current i and the voltage v).

[0031]

As described above, according to the first aspect of the present invention, by monitoring the power value calculated from the current and the voltage of the electric motor of the electric water pump, the drive system of the electric water pump is monitored. Failures such as short circuits and disconnections can be reliably detected.

According to the second aspect of the present invention,
Since the electric power value of the electric motor of the electric water pump is calculated as an average electric power value for a short period of time, the effect of the instantaneous change in the number of revolutions of the electric motor due to a change in load and the influence of electric noise are removed, and the electric water pump fails. Can be detected with higher accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the overall structure of an engine cooling system.

FIG. 2 is an explanatory view of an operation at a cold time corresponding to FIG. 1;

FIG. 3 is a longitudinal sectional view of an electric thermostat.

FIG. 4 is a flowchart of a failure detection routine of the electric water pump.

[Explanation of symbols]

 E engine J water jacket P electric water pump R radiator T electric thermostat U electronic control unit (control means) i current v voltage w power value 12 electric motor

Claims (2)

[Claims] 1. A closed cooling water circuit for connecting a water jacket (J) and a radiator (R) of an engine (E), the cooling water circuit being formed when the valve is opened, and passing through the radiator (R) when the valve is closed. An electric thermostat (T) constituting a bypass circuit not provided and an electric water pump (P) for circulating cooling water are provided, and the control means (U) controls the opening of the electric thermostat (T) and the electric water pump (P). In the engine cooling control device for controlling the number of revolutions, the control means (U) controls the electric motor (12) based on the current (i) and the voltage (v) of the electric motor (12) of the electric water pump (P). A) calculating an electric power value (w), and detecting a failure of the electric water pump (P) based on the electric power value (w). 2. The engine cooling control device according to claim 1, wherein the control means (U) calculates the power value (w) as an average power value for a short time.