Abstract:
A vehicle heating system comprising: a coolant circuit that circulates coolant between an engine and a heater core; heating device that heats coolant, which is interposed in the coolant circuit; a pump for coolant circulation, which is interposed in the coolant circuit; and a switching valve that switches the coolant flowing through the coolant circuit between a heater-core-side circuit that circuits the coolant among the heater core, the pump and the heating device and an engine-side circuit that circulates the coolant into the engine, wherein the switching valve has a thermo valve that switches channels so that the coolant coming from the engine-side circuit enters either one of the heater-core-side circuit and the engine-side circuit according to temperature of the coolant, and a bypass that delivers the coolant, which comes from the heater-core-side circuit, to the heater-core-side circuit.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a vehicle heating system, and more specifically, to a vehicle heating system with coolant-heating device. 
         [0003]    2. Description of the Related Art 
         [0004]    For the purpose of securing heating performance in vehicles including hybrid vehicles, idling-stop vehicles, etc., vehicle heating systems have been developed, which have a heating device, such as an electric heater, for heating the coolant to be introduced into a heater core. 
         [0005]    These vehicle heating systems are equipped with a heating device and an electric pump in a coolant circuit running through the engine and the heater core so that heating may be carried out during engine shutdown. For a quick heating performance during the engine&#39;s cold state, some of these systems are further equipped with a four-way valve for switching coolant routes to prevent the coolant circulating the heater core from entering the engine. The four-way valve is actuated by a control unit and is switched on or off according to room or outside temperature (Unexamined Japanese Patent Application No. 2000-108645). 
         [0006]    The four-way valve mentioned in the publication, however, is of an electric type like an electromagnetic valve or a motor-operated switching valve, which is relatively expensive. On top of that, the actuation of the four-way valve requires a control unit and a temperature sensor, and thus overall increases the cost of the heating system. Furthermore, since the four-way valve is designed to switch the coolant routes according to room or outside temperature detected by the temperature sensor, it is difficult to properly grasp engine temperature and reflect the engine temperature to the heating control. For instance, when the room temperature is low, the valve is switched to the route that does not lead the coolant circulating the heater core into the engine. In this case, once the room temperature is increased with a quick heating effect, the coolant circulating the heater core is switched to the route running to the engine side. At this point, if the engine is in a cold state, there is the possibility of loss of heating performance as the coolant refrigerated in the engine circulates into the heater core. 
       SUMMARY OF THE INVENTION 
       [0007]    It is an object of the present invention to provide a vehicle heating system that performs efficient heating control, reduce the cost of a four-way valve for switching coolant paths, and design the entire heating system with a simple and inexpensive configuration. 
         [0008]    In order to achieve the object, the invention is a vehicle heating system comprising: a coolant circuit that circulates coolant between an engine and a heater core; heating device that heats coolant, which is interposed in the coolant circuit; a pump for coolant circulation, which is interposed in the coolant circuit; and a switching valve that switches the coolant flowing through the coolant circuit between a heater-core-side circuit that circuits the coolant among the heater core, the pump and the heating device and an engine-side circuit that circulates the coolant into the engine, wherein 
         [0009]    the switching valve has a thermo valve that switches channels so that the coolant coming from the engine-side circuit enters either one of the heater-core-side circuit and the engine-side circuit according to temperature of the coolant, and a bypass that returns the coolant, which comes from the heater-core-side circuit, to the heater-core-side circuit; and when the channels are switched so that the coolant coming from the engine-side circuit enters the engine-side circuit, the thermo valve blocks the coolant, which comes from the engine-side circuit, from entering the heater-core-side circuit. 
         [0010]    When the engine temperature is low as seen at cold start, the coolant heated by the heater can be delivered through the bypass into the heater-core-side circuit without passing through the engine by using the switching valve to divide the coolant circuit into the heater-core-side circuit that circulates the coolant among the heater core, the pump and the heating device and the engine-side circuit that circulates the coolant into the engine, and by using the thermo valve to switch the channels according to the temperature of the coolant coming from the engine-side circuit. It is therefore possible to harvest heat from the heater core without reducing the coolant temperature and obtain heating performance quickly. 
         [0011]    Since the thermo valve carries out the switching of the coolant circuit based upon the coolant temperature, it is not necessary to install drive device, such as an electromagnetic solenoid and a motor, for switching the valve, and the switching valve can be configured at low cost. It is also not necessary to provide a controller that controls the drive device for switching the valve, a sensor that detects temperature, etc. Consequently, the heating system overall is simply and inexpensively configured. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The present invention will become more fully understood from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus, are not limitative of the present invention, and wherein: 
           [0013]      FIG. 1  is a schematic configuration diagram of a vehicle heating system according to one embodiment of the invention; 
           [0014]      FIG. 2A  shows a detailed interior configuration of a switching valve when coolant temperature is low, and  FIG. 2B  when the coolant temperature is high; and 
           [0015]      FIG. 3  is a configuration diagram of the vehicle heating system, showing the configuration of the switching valve. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    An embodiment of the invention will be described below with reference to the attached drawings. 
         [0017]      FIG. 1  is a schematic configuration view of a vehicle heating system according to one embodiment of the invention. 
         [0018]    As illustrated in  FIG. 1 , according to the embodiment, an electric heater  3  (heating device), a heater core  4  and an electric pump  5  are interposed in a coolant circuit  2  of an engine  1  in the order named in a direction that coolant flows. 
         [0019]    The electric heater  3  can be actuated even during shutdown of the engine  1  and is capable of heating the coolant in the coolant circuit  2 . The heater core  4  harvests thermal energy from the coolant and performs heat exchange with air to be supplied into the vehicle, to thereby heat the air. The electric pump  5  circulates the coolant in the coolant circuit  2 . 
         [0020]    The coolant circuit  2  is provided with a switching valve  10 . The switching valve  10  has two inlets  11  and  12  and two outlets  13  and  14 , and functions to switch the coolant circuit  2 . Between the two inlets  11  and  12  of the switching valve  10 , the first inlet  11  is connected to a coolant outlet of the engine  1 , and the second inlet  12  to an outlet of the electric pump  5 . Between the two outlets  13  and  14  of the switching valve  10 , the first outlet  13  is connected to an inflow port of the electric heater  3 , and the second outlet  14  to a coolant inlet of the engine  1 . 
         [0021]      FIG. 2A  shows a detailed interior configuration of the switching valve  10  when coolant temperature is low, and  FIG. 2B  when the coolant temperature is high. 
         [0022]    The switching valve  10  has a thermo valve  20  that is open or closed according to the coolant temperature. As shown in  FIG. 2 , the thermo valve  20  is provided with a casing  21  whose interior space is substantially column-shaped and a shaft  22  that is movable within the casing  21  in an axial direction (vertical direction as viewed in  FIG. 2 ). The shaft  22  is equipped with a first valve element  23  in an upper part thereof and a second valve element  24  at a lower end thereof. The interior space of the casing  21  is divided by the first valve element  23  into two, that is, an upper space  25  and a lower space  26 . As shown in  FIG. 2A , when the shaft  22  is located on the upper side, the upper space  25  and the lower space  26  are separated by the first valve element  23 . As shown in  FIG. 2B , when the shaft  22  is located on the lower side, the upper space  25  and the lower space  26  open into each other. 
         [0023]    The first inlet  11  leading to the lower space  26  is formed in a peripheral wall of the casing  21 , and a first outlet  13  leading to the upper space  25  is formed in an upper part of the casing  21 . A valve port  27  opening into the second outlet  14  is formed in a lower part of the casing  21 . The valve port  27  is open/closed by the second valve element  24 . 
         [0024]    The shaft  22  includes a built-in temperature sensor, not shown, and moves in the axial direction according to the temperature of the coolant stored in the lower space  26 . The shaft  22  moves upwards at low coolant temperature and downwards at high coolant temperature, as viewed in  FIG. 2 . 
         [0025]    The switching valve  10  is further provided with a lead-in path  28  linking the second inlet  12  and the second outlet  14 . The switching valve  10  further includes a bypass  29  linking the second inlet  12  and the upper space  25 . 
         [0026]    As shown in  FIG. 2A , when the shaft  22  moves upwards as viewed in the drawing due to a decrease in coolant temperature, the second valve element  24  is detached away from and opens the valve port  27 , connecting the first inlet  11  and the second outlet  14  to each other. At the same time, the upper space  25  and the lower space  26  in the casing  21  are separated from each other by the first valve element  23 , disconnecting the first inlet  11  and the first outlet  13  from each other. 
         [0027]    As shown in  FIG. 2B , when the shaft  22  moves downwards as viewed in the drawing due to an increase in coolant temperature, the valve port  27  is closed by the second valve element  24 . Simultaneously, the first valve element  23  is open, making the upper space  25  and the lower space  26  in the casing  21  open into each other, and connecting the first inlet  11  and the first outlet  13  to each other. 
         [0028]      FIG. 3  is a configuration diagram of the vehicle heating system, showing the construction of the switching valve  10 . 
         [0029]    Since the embodiment constructs the switching valve  10  in the above-described manner, the coolant coming from the engine  1  into the first inlet  11  is switched between the inflow into the first outlet  13  side, namely, into the electric heater  3 , and the returning to the second outlet  14  side, namely, to the engine  1 . 
         [0030]    The coolant coming from the second inlet  12  is discharged from the second outlet  14  through the lead-in path  28  and returns to the coolant inlet of the engine  1 . 
         [0031]    Since the bypass  29  links the second inlet  12  and the first outlet  13 , even if the first inlet  11  and the first outlet  13  are disconnected from each other, the coolant coming from the second inlet  12  can be supplied to the first outlet  13  by passing through the bypass  29 . 
         [0032]    Consequently, when the coolant coming from the engine  1  has low temperature, there are created a circuit  30  (engine-side circuit) in which the coolant from the engine  1  is returned to the engine  1  by the thermo valve  20  without passing through the heater core  4 , and a coolant circuit  31  (heater-core-side circuit) that is provided with the electric heater  3 , the heater core  4  and the electric pump  5 , and does not run through the engine  1 . When the temperature of the coolant coming from the engine  1  is decreased as seen right after startup, the coolant heated by the electric heater  3  does not pass through the engine  1  and is introduced into the heater core  4  while the decrease of the coolant temperature is prevented. This makes it possible to harvest heat from the heater core  4  and immediately raise the coolant temperature. 
         [0033]    When the coolant coming from the engine  1  has high temperature, the coolant delivered from the engine  1  is caused to enter the heater core  4  side by the thermo valve  20 . The heat of the coolant discharged from the engine  1  can therefore be harvested from the heater core  4 . It is then possible to achieve the heating that applies the heat of the engine  1 . 
         [0034]    Since the switching of the coolant circuit  2  based upon the coolant temperature is carried out by the thermo valve  20 , it is not necessary to provide any drive device, such as an electromagnetic solenoid, a motor, etc., for switching the valve. For that reason, the switching valve  10  can be constructed at low cost. It is also not necessary to provide a controller that controls the drive device for switching the valve, a sensor that detects temperature, etc. Consequently, the heating system overall is simply and inexpensively configured. 
         [0035]    After passing through the heater core  4  and entering the second inlet  12 , the coolant passes through the lead-in path  28  and is discharged from the second outlet  14 . The coolant is subsequently introduced into the engine side, regardless of the switching of the thermo valve  20 . On this account, when the shaft  22  of the thermo valve  20  moves upwards and creates the coolant circuit  31  that does not run through the engine  1 , even if the coolant circulating through the circuit  31  is increased in temperature to expand by the heating of the electric heater  3  or the like, water leakage from the circuit  31  can be prevented by introducing the coolant into the engine  1  side through the lead-in path  28 . 
         [0036]    The embodiment actuates the electric pump  5  during the heating of the vehicle and stops the electric pump  5  during the cooling of the vehicle. 
         [0037]    In the present embodiment, the first outlet  13  and the second inlet  12  are constantly linked to each other through the bypass  29 . For that reason, if the electric pump  5  is at rest when the shaft  22  moves downwards due to the increase of the coolant temperature, the fluid pressure of the coolant existing in the lead-in path  28  is decreased. As a result, part of the coolant that has come from the first inlet  11  is returned to the engine  1  through the bypass  29  and the lead-in path  28 . This causes the possibility that the coolant passing through the heater core  4  is decreased in flow volume, and heating efficiency is therefore deteriorated. However, if the electric pump  5  is actuated during heating as mentioned above, a sufficient flow volume of the coolant passing through the heater core  4  can be retained, and the heating efficiency is secured. 
         [0038]    During the cooling of the vehicle, when the shaft  22  moves downwards due to an increase in coolant temperature, the flow volume of the coolant existing in the lead-in path  28  is decreased by stopping the electric pump  5 . This way, the coolant that has come from the first inlet  11  is actively returned to the engine  1  through the bypass  29 . The high-temperature coolant is therefore prevented from passing through the heater core  4 , which discourages the generation of hot air from the heater core  4 . This consequently prevents deterioration in cooling performance.