JP2012102639A - Engine cooling system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine cooling system for enabling the temperature of cooling water to quickly reach a target water temperature.SOLUTION: A flow rate of an electric water pump 6 is increased in a quantity from when the temperature of the cooling water exceeds the target water temperature, a water quantity between an engine 1 and a radiator 4 is increased by putting an electronic thermostat 8 being an opening-closing valve in an opening state, the flow rate of the electric water pump 6 is reduced in the quantity from when the temperature of the cooling water is less than the target water temperature, the electronic thermostat 8 is put in a closing state P, and feedback gain on control of the electric water pump 6 is made variable in response to an engine load.

Description

  The present invention relates to an engine cooling device that circulates engine coolant using an electric water pump.

  2. Description of the Related Art Conventionally, there has been proposed an engine cooling apparatus that includes a mechanical water pump that operates by obtaining driving force from an engine and controls the circulating flow rate of cooling water. Currently, in addition to the mechanical water pump, an engine cooling device using an electronic thermostat capable of controlling the circulating flow rate of cooling water regardless of the driving force of the engine has been proposed (for example, Patent Document 1). reference). In this device, the flow rate of the electric water pump and the opening degree of the electronic thermostat are determined in accordance with the operating state in consideration of the power consumption for opening the valve of the electronic thermostat.

  However, with the above-described mechanical water pump, the target water temperature of the cooling water is set to be low in advance in consideration that the circulating flow rate of the cooling water depends on the engine speed. . As a result, fuel consumption is always deteriorated by cooling the cooling water more than necessary. Further, in the engine cooling device described in Patent Document 1, since control is performed without distinguishing between overshoot and undershoot from the viewpoint of converging the coolant temperature to the target temperature, particularly when the required load increases. Becomes difficult to follow the target water temperature.

JP 2006-37883 A

  The object of the present invention is to cause the coolant temperature to quickly follow the target coolant temperature among the points described above.

  In order to achieve such an object, the present invention takes the following measures.

  That is, an engine cooling apparatus according to the present invention includes an electric water pump and an on-off valve that controls the amount of water between the engine and the radiator, and includes a cooling water passage in the engine by driving the electric water pump. The cooling water is circulated in the air, and the flow rate of the electric water pump is increased from the time when the temperature of the cooling water exceeds the target water temperature, and the on-off valve is controlled to the open side so that the flow between the engine and the radiator is increased. The amount of water is increased, the flow rate of the electric water pump is reduced from the time when the cooling water temperature falls below the target water temperature, and the on-off valve is controlled to be closed, so that the flow rate of the electric water pump is adjusted to the required load. It is characterized in that it is controlled variably in response.

  If it is such, the water temperature of a cooling water can be made to follow a target water temperature rapidly by variably controlling the flow volume of an electric water pump according to a required load.

  In addition, when the target water temperature of the cooling water itself is changed due to a change in the required load or the engine speed, the cooling water temperature and the target water temperature are greatly deviated instantaneously at the timing when the target water temperature is changed. It will be. Even in such a case, in order to cause the cooling water temperature to quickly follow the target water temperature, the electric water pump is controlled so that the absolute value of the difference between the cooling water temperature and the target value is predetermined. When the value is larger than the value, feedforward control is performed to determine the flow rate of the electric water pump based on the engine speed and the required load, and the absolute value of the difference between the coolant temperature and the target value is greater than a predetermined value. If it is smaller, it is desirable to perform feedback control for determining the flow rate of the electric water pump according to the difference from the target value. Thereby, the time lag from the timing when the target water temperature is changed can be eliminated, and prompt control can be performed.

  According to the present invention, it is possible to provide a cooling device for an engine that promptly follows the coolant temperature to the target coolant temperature by variably controlling the flow rate of the electric water pump according to the required load.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration explanatory diagram according to an embodiment of the present invention. Other typical composition explanatory views concerning the embodiment. The flowchart which concerns on the same embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  1 and 2 are diagrams showing a schematic configuration of an engine 1 and an engine cooling device for cooling the engine 1. The engine 1 is a compression ignition type engine 1 (diesel engine) using light oil as a fuel or a spark ignition type engine (gasoline engine) using gasoline as a fuel, and is mounted on an automobile or the like. 1 shows a state where an electronic thermostat 8 to be described later is in a closed state (P), and FIG. 2 shows a state in which it is in an open state (Q).

  The engine 1 includes a cylinder head, a cylinder block, and the like, and the cylinder head and the cylinder block are provided with a cooling water passage 1a that is a passage for circulating water as a heat medium. As shown in FIGS. 1 and 2, on the outlet side of the cooling water passage 1a, the heater side cooling water passage 3 for guiding the cooling water to the heater core 2 for heating the vehicle interior and the radiator side for guiding the cooling water to the radiator 4 are provided. A cooling water passage 5 is connected. The cooling water passage 1a, the heater side cooling water passage 3 and the radiator side cooling water passage 5 constitute the cooling water circulation path according to the present invention.

  Further, the engine 1 is provided with an electric water pump 6 that sucks in cooling water that has flowed through the heater side cooling water passage 3 and the radiator side cooling water passage 5 from the outside, and sends the cooling water to the cooling water passage 1a. When a voltage is applied to the electric water pump 6 according to a command signal from the ECU 9 described later, the electric water pump 6 supplies cooling water having a flow rate corresponding to the applied voltage to the cooling water passage 1a.

  A radiator bypass passage 7 is connected to the radiator-side cooling water passage 5, and an electronic thermostat 8, which is an on-off valve, is provided at a connection portion between the radiator-side cooling water passage 5 and the radiator bypass passage 7.

  This electronic thermostat 8 is a wax that controls the flow rate of cooling water flowing through the radiator 4 and flowing through the radiator side cooling water passage 5 and cooling water flowing through the radiator bypass passage 7 to the electric water pump 6 side. It is equipped with a thermostat valve of the type. This thermostat valve uses a wax that compresses and expands according to temperature as a temperature sensing part, and the valve can be mechanically opened and closed according to the temperature of the cooling water that has passed through the engine cooling water passage 1a. The PTC (Positive Temperature Coefficient) heater which electrically heats this temperature sensing part is provided. And by electrically energizing this PTC heater and electrically heating the wax, it is possible to electronically control the opening and closing of the thermostat valve.

  In this embodiment, an ECU 9 is provided to control the engine 1 and the like described above. The ECU 9 is mainly configured by a microcomputer system including a central processing unit, a storage device, an input interface, and an output interface.

  The ECU 9 outputs a crank position sensor (not shown) that outputs an electrical signal corresponding to the rotational speed of the crankshaft that is the output shaft of the engine 1, and an electrical signal that corresponds to the amount of air taken into the cylinder of the engine 1. An air flow meter (not shown), and a water temperature sensor 10 for outputting an electric signal corresponding to the temperature of the cooling water flowing in the engine cooling water passage 1a on the cylinder head side are electrically connected, and their outputs A signal is input to the ECU 9.

  The ECU 9 is electrically connected to the electric water pump 6, and the ECU 9 controls the electric water pump 6 so that the ECU 9 controls the electric water pump 6 to circulate the cooling water in the cooling water circulation path including the in-engine cooling water passage 1 a. It is possible to control. The ECU 9 is electrically connected to the electronic thermostat 8 so that the ECU 9 can control energization to the PTC heater of the electronic thermostat 8.

  Then, the ECU 9 increases the flow rate of the electric water pump 6 from the time when the cooling water temperature exceeds the target water temperature, and controls the electronic thermostat as the opening / closing valve in the open state (Q) to control the amount of water between the engine 1 and the radiator 4. In addition, the flow rate of the electric water pump 6 is reduced from the time when the coolant temperature falls below the target water temperature, and the electronic thermostat 8 is controlled to the closed state (P). In addition, the electric water pump A program for making the feedback gain related to the control No. 6 variable according to the engine load which is a required load such as an accelerator depression amount is incorporated.

  Subsequently, the control of the electric water pump and the electronic thermostat 8 for cooling the engine 1 in the present embodiment will be described.

  In the present embodiment, the flow rate of the electric water pump 6 is increased from the time when the coolant temperature exceeds the target water temperature, and the water amount between the engine and the radiator is increased by controlling the electronic thermostat 8 to the open state (Q). . Then, the flow rate of the electric water pump is reduced from the time when the coolant temperature falls below the target coolant temperature, and the electronic thermostat 8 is controlled to the closed state (P).

  In the present embodiment, the feedback gain used for controlling the electric water pump 6 is determined based on a map created by the engine load and the engine speed. The map is set so that the feedback gain increases when the engine load increases, such as when the accelerator pedal is depressed. The control using the feedback gain can employ various feedback controls such as a proportional control for multiplying the deviation by the feedback gain, an integral control for multiplying the integral value of the deviation, or a proportional integral control.

  That is, when the engine load increases, the flow rate (the slope) of the electric water pump 6 increases by inputting a feedback gain larger than that before the engine load increases based on the map. Thereby, the water temperature of cooling water can be rapidly reached to the target water temperature.

  Here, the target temperature of the cooling water is determined based on a map created based on the engine speed and the engine load. In other words, when the engine load increases during operation, the coolant temperature rapidly increases, or at the same time as the load increases, the target water temperature is changed to a low value. It can happen.

  Therefore, in the present embodiment, as shown in the flowchart of FIG. 3, the control of the electric water pump 6 is performed when the absolute value of the difference between the coolant temperature and the target value is larger than a predetermined value of 10 ° C. Feed forward control is performed to determine the flow rate of the electric water pump 6 based on the engine speed and the engine load, and feedback control is performed when the absolute value of the difference between the coolant temperature and the target coolant temperature is less than 10 ° C. I have to. The control of the electric water pump (electric W / P) 6 and the electronic thermostat (electronic thermo) 8 will be described with reference to FIG.

  First, the temperature of the cooling water rises as the engine 1 starts, but the operation of the electric water pump 6 is stopped and the electronic thermostat 8 is closed until the temperature of the cooling water reaches 80 ° C. (step S1). (P) (step S2).

  When the actual water temperature exceeds 80 ° C. and the deviation between the cooling water temperature, that is, the actual water temperature and the target water temperature exceeds 10 ° C. (step S3), the feedforward (F / F) control is performed as follows. Is done. In this case, when the actual water temperature is higher than the target water temperature (step S4), the electronic thermostat 8 is opened (Q), and the flow rate of the electric water pump 6 is set to a predetermined value (step S5). The predetermined value is determined based on a map created based on the engine load and the engine speed. When the actual water temperature is lower than the target water temperature (step S4), the electronic thermostat 8 is closed (P), and the flow rate of the electric water pump 6 is set to a predetermined value (step S6). This predetermined value is determined based on a map created based on the engine load and the engine speed as described above.

  On the other hand, when the deviation between the actual water temperature and the target water temperature does not exceed 10 ° C. (step S3), feed-back (F / B) control is performed. In this case, when the actual water temperature is higher than the target water temperature (step S7), the electronic thermostat 8 is opened (Q), and the feedback gain of the electric water pump 6 is created based on the engine speed and the engine load. The values determined in the map are set (step S8). If the actual water temperature is lower than the target water temperature (step S7), the electronic thermostat 8 is closed (P), and the feedback gain of the electric water pump 6 is created based on the engine speed and the engine load. (Step S9). In this way, even if the target water temperature changes due to a change in engine load, the actual water temperature can quickly follow the target water temperature.

  With the configuration as described above, according to the present embodiment, when the engine load increases, the flow rate of the electric water pump is greatly feedback-controlled, so that the coolant temperature can quickly follow the target coolant temperature. It has become.

  In this embodiment, the water temperature of the cooling water is controlled by the water pump based on the engine speed and the engine load when the difference between the cooling water temperature and the target value is larger than a predetermined value. Feedforward control is performed to calculate the flow rate per unit time, and when the difference between the coolant temperature and the target value is smaller than a predetermined value, feedback control is performed for the difference between the target value and the target value. Therefore, the time lag from when the target water temperature is changed to when the control is executed can be eliminated, and the coolant temperature can be quickly reached the target water temperature.

  Although the embodiment of the present invention has been described above, the specific configuration of each unit is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, in the above-described embodiment, the electronic thermostat is controlled to be controlled only in two stages, that is, the open state and the closed state. However, of course, the electronic thermostat is controlled in multiple stages more than two stages, or in a non-stage control. An open / close valve may be used. In the above embodiment, the absolute value of the difference between the target water temperature and the actual water temperature of the cooling water when switching between the feedback control and the feedforward control is set to 10 ° C. as an example. . Further, the specific mode of the map for determining the target water temperature, the feedback gain, and the value used for the feedforward control is not limited to that of the above embodiment, and various modes including the existing one are applied. be able to.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can be used as an engine cooling device that circulates engine coolant using an electric water pump.

DESCRIPTION OF SYMBOLS 1 ... Engine 4 ... Radiator 6 ... Electric water pump 8 ... Electronic thermostat

Claims (2)

An electric water pump and an open / close valve that controls the amount of water between the engine and the radiator are provided, and the cooling water is circulated through a cooling water circulation path including a cooling water passage in the engine by driving the electric water pump. And
Increase the flow rate of the electric water pump from the time when the coolant temperature exceeds the target water temperature, and perform feedback control to increase the amount of water between the engine and the radiator by controlling the open / close valve to the open side,
Reducing the flow rate of the electric water pump from the time when the temperature of the cooling water falls below the target water temperature, and performing feedback control to control the open / close valve to the closed side;
An engine cooling apparatus characterized in that a feedback gain related to the control of the electric water pump is variable in accordance with an engine load. When the absolute value of the difference between the cooling water temperature and the target water temperature is greater than a predetermined value, the electric water pump is controlled to determine the flow rate of the electric water pump according to the engine speed and the engine load. Forward control,
The feedback control for determining the flow rate of the electric water pump according to the difference with the target water temperature when the absolute value of the difference between the water temperature value and the target value is smaller than a predetermined value. Engine cooling system.

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