RADIATOR COOLING SYSTEM IN AN INTERNAL COMBUSTION ENGINE

Abstract: A cooling system for a radiator in an internal combustion engine is provided with a pair of fans connected to a first motor for a small electric current and a second motor for a large elec­ tric current, respectively. Relays are provided for operating the first and/or second motor sequentially in accordance with the degree of cooling requirement of the engine. A delay device is provided for delaying the operation of the relay(s) for attaining a stronger cooling requirement for a predetermined short pe­ riod just after the engine is started. A generation of rush cur­ rent in the relay contacts is prevented.

Description: 1. Field of the Invention The present invention relates to an apparatus for controlling an electrically operated radiator cooling system in an internal combustion engine. 2. Description of the Related Art DE-A-28 06 708 discloses a radiator cooling system in an internal combustion engine of a vehicle comprising a temperature-regulating arrangement wherein a control circuit operates a radiator ventilation system at a first speed when a first temperature detector detects that the temperature at a certain place in the cooling system exceeds a predetermined threshold value, and at a second higher or maximum speed when a second temperature detector detects that the temperature at another place in the cooling system exceeds another higher threshold value, to attain a desired fan speed which is sufficient to properly cool the radiator system. Furthermore, US-A-4 426 960 discloses a control circuit for multistage fans, wherein a delay circuit is provided to inhibit any two fans from being started simultaneously in order to minimize loading due to motor start currents. However, such a radiator cooling system with a temperature-regulating arrangement wherein a plurality of operational parameters are taken into account, is disadvantageous from the viewpoint of cost, and the need for the dimensions of the parts to be increased which causes difficulties in the mounting of the device in a restricted space in the vehicle. SUMMARY OF THE INVENTION An object of the invention is to provide an apparatus capable of overcoming the above mentioned difficulties formed in the above referenced radiator cooling systems of the prior art. According to the present invention, a radiator cooling system in an internal combustion engine is provided, comprising: a) at least one electrically operated cooling fan, b) first sensor means sensing the temperature of an engine coolant medium so as to produce an electrical signal indicating the temperature of said engine coolant medium, and c) a control circuit controlling the electric current in the electrically operated cooling fan according to predetermined temperature conditions of the engine detected by said sensor means, said control circuit generating a small electric current to be supplied to the fan when the radiator cooling requirement is small, and a large electric current to be supplied to the fan when the radiator cooling requirement is high, said radiator cooling system being characterized by further comprising: d) a small motor for said small electric current being connected to a first fan member and a large motor for said large electric current being connected to a second fan member of said electrically operated cooling fan; e) second sensor means sensing operating conditions of an air conditioner system operated by rotation of said engine, said second sensor means comprising a first detector detecting the actuation of said air conditioner system, corresponding to a weak cooling requirement, and a second detector detecting a high pressure of the cooling medium of the air conditioner system, corresponding to a strong cooling requirement; f) third sensor means sensing fail-safe conditions; and g) a timer delay circuit preventing a circuit portion of said control circuit from being connected to an electric power source for a predetermined time period; h) wherein, when the temperature of the engine cooling medium reaches a first threshold value, the small motor and the large motor are controlled to attain a low speed rotation, when the temperature of the engine cooling medium reaches a higher second threshold value, the small motor is controlled to attain a high speed rotation while the large motor is controlled to maintain said low speed rotation, and when the temperature of the engine cooling medium reaches an even higher third threshold value, the small motor and the large motor are controlled to attain a high speed rotation; when said first detector detects the actuation of said air conditioner system, the small motor and the large motor are controlled to attain a low speed rotation, even if the temperature of the engine cooling medium is lower than said first threshold value, and when said second detector detects a high pressure of the cooling medium of the air conditioner system, the small motor is controlled to attain a high speed rotation while the large motor is controlled to attain a low speed rotation; and when said third sensor means senses a fail-safe condition indicating the requirement of a cooling effect, the small motor is controlled to attain a high speed rotation and the large motor is controlled to attain a low speed rotation, while both motors are de-energized when a fail-safe condition indicating a lock condition is detected; and wherein, when the engine is started and the temperature of the engine cooling medium is higher than said second or third threshold value or a high pressure of the cooling medium of the air conditioner system is detected, the small motor and the large motor are both controlled to attain only a low speed rotation from the beginning of the start of the engine during said time period predetermined by said timer delay circuit, irrespective of the degree of the radiator cooling requirement. Thus, a small fan motor and a large fan motor can be used advantageously for the cooling fan in connection with a temperature-regulating arrangement involving a plurality of operational parameters, and a shockless and safe operation of the radiator cooling system can be obtained with a small and simple construction. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a general systematic view of the radiator cooling system according to the present invention; Figure 2 shows details of the control circuit according to the present invention; and, Figure 3 shows timing charts explaining the operation of the radiator cooling system according to the present invention. DESCRIPTION OF A PREFERRED EMBODIMENT In Figure 1, showing the embodiment of the present invention, 10 designates the body of an internal combustion engine, and 12 a radiator. A pair of cooling fans 14 and 14' are arranged in parallel on the side of the radiator 12 facing the engine body 10 and are connected to a small electric motor 16, and a large electric motor 17, respectively. Reference numeral 18 denotes a control circuit designed so as to operate the cooling fans in response to the operation of the engine and/or an air conditioner system. The air conditioner system is provided with a compressor 20 which is connected to an electro-magnetic clutch 22 having an output shaft having a pulley 24 fixed thereon. The engine is provided with a crankshaft 10' having a pulley 28 fixed thereon, which is connected to the pulley 24 by way of a belt 26. The control circuit 18 is connected to an ignition switch 30 for starting the engine, a magnet switch (A/C switch) 32 for operating the air conditioner system, a switch 34 for sensing a high pressure condition in the air conditioner system, and an engine cooling water temperature sensor 36, so that the control circuit 18 attains a desired operation in response to signals from these switches. The magnet switch 32 controls the operation of the clutch 22 for rotating the compressor 20; the high pressure switch 34 detects a high pressure of the coolant housed in the compressor 20; and the temperature sensor 36 is mounted on the engine body 10 so that it is in contact with the cooling water in a water jacket 10'' of the engine body 10. Figure 2 shows a detailed construction of the control circuit 18 in Fig. 1. The control circuit 18 is provided with a cooling fan driving section 38, a relay section 40, and an air conditioner driving unit 42. A detailed construction of the unit 42 for operating the air conditioner, including the compressor 20, is omitted, since it is not directly related to the present invention. The relay section 40 is provided with first, second, and third relays R₁ , R₂ , and R₃. The first and third relays R₁ and R₃ have normally opened contacts r₁ and r₃ , respectively, which are in series connection with a battery BAT on one side and the large motor 17 on the other side. The contact r₁ of the first relay R₁ is, at the side near the contact r₃ , connected to a contact of the second relay R₂ which is in series connection with the small motor 16. The small motor 16 has windings having a small value resistance, such as 1.8 Ω, and consumes an electric power of 80W. The large motor 17 has windings having an electric resistance with a value of, e.g., 0.48 Ω, and consumes an electric power of 300W. A resistor element 46 having a value of, e.g., 0.46 Ω, is arranged between the contact r₁ and the motor 17, so as to by-pass the contact r₃ of the third relay R₃. The contact r₂ of the second relay R₂ is switched between a condition wherein the small motor 16 is connected with the battery BAT via the resistor element 46 and condition where the small motor 16 is connected with the battery BAT without the intervention of the resistor element 46. The cooling fan driving unit 38 is for operating the first, second and third relays R₁ , R₂ , and R₃ in accordance with the conditions of the air conditioner system. A comparator 50 issues a "1" signal when the air conditioner magnet switch 32 is made ON, and a "0" signal when the switch 32 is made OFF. A comparator 51 issues a "1" signal when the air conditioner pressure switch 34 is made ON due to the high pressure of the coolant in the compressor 20, and a "0" signal when the switch 34 is made OFF due to a low pressure of the coolant therein. A comparator 52 issues a "1" signal when the temperature of the engine cooling water sensed by the engine cooling water temperature sensor 36 rises above 90°C, and a "0" signal when the temperature falls below 85°C. A comparator 53 issues a "1" signal when a connector member (not shown) for a cable for connecting the engine cooling water temperature sensor 36 is not normally connected and a "0" signal when the connector is normally connected. A comparator 54 issues a "1" signal when the cooling water temperature rises above 95°C, and a "0" signal when the temperature falls below 90°C. A comparator 55 issues a "1" signal when the engine cooling water temperature rises above 105°C, and a "0" signal when the temperature falls below 100°C. A comparator 56 issues a "1" signal when the electric motors 16 and 17 are normally rotated, and a "0" signal when at least one of these motors 16 and 17 is overloaded due to a "lock" condition. The respective inputs of the comparators 50, 52, and 53 are connected to a first OR gate 57. The respective inputs of the comparators 51, 53 and 54 are connected to a second OR gate 58. The outputs of the first OR gate 57 and the comparator 56 are connected to a first AND gate 59 at the respective inputs. The output of the first AND gate 59 and the output of the second OR gate 58 are connected to a second AND gate 60 at the respective inputs. Finally, the output of the first AND gate 59 and the comparator 55 are connected to a third AND gate 61 at the respective inputs. The first AND gate 59 is for operating the first relay R₁ , which gate 59 is connected to a base of a Darlington connected transistor unit 62. The transistor unit 62 has an emitter-collector circuit in which a coil L₁ of the first relay R₁ is arranged. The second AND gate 60 is for controlling the relay R₂ , the output of which gate 60 is connected to a Darlington connected transistor unit 63 at the base thereof. The transistor unit 63 has an emitter-collector circuit in which a coil of the second relay R₂ is arranged. The third AND gate 61 is for controlling the third relay R₃ , the output of which gate 61 is connected to a Darlington connected transistor unit 64 at the base thereof. The transistor unit 64 has an emitter-collector circuit in which a coil L₃ of the third relay R₃ is located. The first AND gate 59 is connected not only to the transistor unit 62 for operating the first relay R₁ but also to the second and third AND gates 60 and 61 for operating the second and the third relays R₂ and R₃ , respectively. As will be fully understood from the later description, such a connection allows the electric current in the electric motors 16 and 17 to be increased in a sequential manner in accordance with the cooling ability, as required, in order to attain a sufficient and a necessary cooling operation. This construction of the first AND gate 59 capable of controlling not only the first relay R₁ for the least cooling ability but also of controlling the second and the third relays R₂ and R₃ , respectively, adapted for a much higher cooling ability, inevitably generates a condition wherein a plurality of relays R₁ and R₂ or R₁ , R₂ , and R₃ are simultaneously operated when a required cooling ability is high upon the start of the engine. When this situation occurs, a large amount of electric current is generated in the relay coils when the relays are energized, which will have an adverse effect on the durability of not only the coils but also the contacts r₁ , r₂ , and r₃. According to the improvement by the present invention, a delay unit such as a one-shot multi-vibrator 70 is arranged between the first AND gate 59 and the second and third AND gates 60 and 61. The delay unit 70 allows the operation of the second and the third AND gates 60 and 61 when a predetermined time, such as 1 to 10 seconds, has lapsed after the issuance of the trigger signal "1" from the first AND gate 59, as shown in Fig. 3-(e) and (f). The operation of the radiator cooling system according to the present invention will be described hereinbelow. During the normal engine running condition, when the temperature of the cooling water of the engine becomes higher than 90°C, the OR gate 57 is made ON, causing the first AND gate 59 to be made ON, so that the transistor unit 62 is made ON, causing the coil L₁ of the first relay R₁ to be energized (see Figure 3-(e)). Thus, the contact r₁ is made ON and the small motor 16 and the large motor 17 are energized by way of the resistor element 46 for decreasing the electric current. Thus, the cooling fans 14 and 14' connected to the electric motors 16 and 17, respectively, attain a low speed rotation. When the temperature of the cooling water rises above 95°C, the second OR gate 58 is made ON while the first AND gate 59 is maintained ON. Thus, the first and second transistor units 62 and 63 are made ON, causing the relay coils R₁ and R₂ to be energized, so that the relay contacts r₁ and r₂ are both made ON (see Figure 3-(e and f)). Therefore, the small motor 16 is directly connected to the battery BAT without the intervention of the resistor element 46, while the large motor 17 is still connected via the resistor element 46. Therefore, the rotational speed of the small motor 16 connected to the fan 14 is increased, and accordingly, an increase in cooling capacity is obtained as a whole. When the temperature of the cooling water becomes higher than 105°C, the third AND gate 61 is made ON while the first and second AND gates 59 and 60 are maintained ON (Fig. 3-(g)). Therefore, the transistor unit 64 is made ON so that the coil L₃ of the third relay R₃ is energized. Thus, the contact r₃ is made ON, so that not only the small motor 16 but also the large motor 17 is directly connected to the battery BAT without the intervention of the resistor element 46. Thus, the fans 14 and 14' attain their maximum rotational speed. In addition to the above basic operation, the control of the rotational speed of the fans 14 and 14' is attained in accordance with the conditions of the air conditioning system. When the air conditioner magnet switch 32 is made ON, because an air conditioner switch is made ON, the OR gate 57 issues a "1" signal, causing the transistor 62 to be made ON, so that the coil L₁ of the first relay R₁ is energized so as to make the contact r₁ to be ON. Thus, the small motor 16 and the large motor 17 are rotated at a decreased rotational speed, even if the engine cooling temperature is lower than 90°C. When the load of the air conditioner system is high, the comparator 51 produces a "1" signal due to the high pressure of the cooling medium in the compressor 20. In this case, the OR gate 58 issues a "1" signal, which causes the second AND gate 60 to issue a "1" signal while the first AND gate 59 issues a "1" signal. Thus, the transistor 63 is made ON, causing the second relay R₂ to be energized. Thus, the small motor 16 attains a high rotational speed, and the large motor 17 attains a low rotational speed. Further, the following fail-safe operations are attained. If the connector of the engine cooling water temperature sensor 36, which connector connects the temperature sensor 36 with the electric control unit 18, is accidentally disconnected, a "1" signal is issued from the first OR gate 57 and second OR gate 58 for energizing the first and second relays R₁ and R₂. Thus, a high rotational speed of the small motor 16 and a low rotational speed of the large motor 17 are maintained. Furthermore, when a lock condition is detected by detecting a high electric current generated in the motor 16 or 17, the comparator 56 issues a "0" signal directed to the AND gate 59. Therefore, the AND gate 59 constantly issues a "0" signal irrespective of the conditions of the other comparator units 51 to 55. All of the relays 62, 63, and 64 are maintained in a de-energized condition, preventing the motors 16 and 17 from an overload. When the engine is started, the relays R₁ , R₂ , and R₃ are, in most cases, in a condition wherein they are to be de-energized, since the temperature of the engine cooling water is low and the air conditioner is not in operation. However, in some cases, the relays are in a condition wherein they are to be operated when the engine is started. For example, when the engine cooling water temperature is higher than 95°C or the high pressure switch 34 is ON at the same time as when the engine is to be started, not only the first relay R₁ but also the second relay R₂ and/or the third relay R₃ are simultaneously in a condition to be energized. In this case, the first AND gate 59 issues a "1" signal at the same time as the start of the engine, for energizing the first relay R₁ and attaining a low rotational speed of the fans 14 and 14'. However, the "1" signal from the first AND gate 59 cannot be immediately transmitted to the second and third AND gates 60 and 61, due to the existence of the one-shot multivibrator 70. After the lapse of the short period T from the start of the engine, the delay unit 70 allows the transmission of a "1" signal from the first AND gate 59 to the second and/or third AND gates 60 and 61, allowing the relays R₂ and R₃ to be energized. Due to the delay of the operation of the relays R₂ and R3 , a rush current in the relay control circuit is prevented, allowing the life of the relay coils and relay contacts to be prolonged.

Claims: A radiator cooling system in an internal combustion engine, comprising: a) at least one electrically operated cooling fan, b) first sensor means sensing the temperature of an engine coolant medium so as to produce an electrical signal indicating the temperature of said engine coolant medium, and c) a control circuit controlling the electric current in the electrically operated cooling fan according to predetermined temperature conditions of the engine detected by said sensor means, said control circuit generating a small electric current to be supplied to the fan when the radiator cooling requirement is small, and a large electric current to be supplied to the fan when the radiator cooling requirement is high, said radiator cooling system being characterized by further comprising: d) a small motor (16) for said small electric current being connected to a first fan member (14) and a large motor (17) for said large electric current being connected to a second fan member (14') of said electrically operated cooling fan; e) second sensor means (32, 34) sensing operating conditions of an air conditioner system (20, 22, 24) operated by rotation of said engine, said second sensor means comprising a first detector (32) detecting the actuation of said air conditioner system, corresponding to a weak cooling requirement, and a second detector (34) detecting a high pressure of the cooling medium of the air conditioner system, corresponding to a strong cooling requirement; f) third sensor means (53, 56) sensing fail-safe conditions; and g) a timer delay circuit (70) preventing a circuit portion of said control circuit (18) from being connected to an electric power source (BAT) for a predetermined time period (T); h) wherein, when the temperature of the engine cooling medium reaches a first threshold value, the small motor and the large motor are controlled to attain a low speed rotation, when the temperature of the engine cooling medium reaches a higher second threshold value, the small motor is controlled to attain a high speed rotation while the large motor is controlled to maintain said low speed rotation, and when the temperature of the engine cooling medium reaches an even higher third threshold value, the small motor and the large motor are controlled to attain a high speed rotation; when said first detector detects the actuation of said air conditioner system, the small motor and the large motor are controlled to attain a low speed rotation, even if the temperature of the engine cooling medium is lower than said first threshold value, and when said second detector detects a high pressure of the cooling medium of the air conditioner system, the small motor is controlled to attain a high speed rotation while the large motor is controlled to attain a low speed rotation; and when said third sensor means senses a fail-safe condition indicating the requirement of a cooling effect, the small motor is controlled to attain a high speed rotation and the large motor is controlled to attain a low speed rotation, while both motors are de-energized when a fail-safe condition indicating a lock condition is detected; and wherein, when the engine is started and the temperature of the engine cooling medium is higher than said second or third threshold value or a high pressure of the cooling medium of the air conditioner system is detected, the small motor and the large motor are both controlled to attain only a low speed rotation from the beginning of the start of the engine during said time period predetermined by said timer delay circuit, irrespective of the degree of the radiator cooling requirement. A radiator cooling system according to claim 1, being characterized in that said control circuit (18) comprises an electric resistor element (46) connected to said large motor (17), and a switching circuit (R3) selectively by-passing the electric resistor element in accordance with the radiator cooling requirement.

Inventors: MASAHIKO, NOBA
Applicants: TOYOTA JIDOSHA KABUSHIKI KAISHA
Application year: 1986
Main classification: F01P7
IPC codes: F01P5, H02H7, F01P7, B60H1