Alternator control device

Abstract

To provide a control device for an alternator that can prevent abnormal noise without unnecessarily increasing a rotation speed of an engine.SOLUTION: A control device 26 controls the drive of an alternator 12 that generates power by power transferred from an engine 10 and charges a battery 22. The control device 26 restricts an excitation current To of the alternator 12 so that a load torque TRQo of the alternator 12 falls below specified allowable torque when a voltage Vb of the battery 22 is equal to or greater than a specified reference voltage Vs, a rotation speed Ne of the engine 10 is equal to or less than a specified reference rotation speed Nst, and a temperature To of the alternator 12 is equal to or less than a specified reference temperature Tst.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] This specification discloses an alternator control device that controls the operation of an alternator that generates electricity using power transmitted from an engine to charge a battery. [Background technology]

[0002] Generally, an engine-equipped vehicle is provided with an alternator that generates electricity using power transmitted from the engine. The power of the engine is transmitted to the alternator by a transmission mechanism having a pulley and a belt. In other words, the power of the engine is transmitted by the frictional force between the belt and the pulley.

[0003] When the engine speed is low and the alternator temperature is low, the load torque of the alternator increases. When the load torque of the alternator increases, slippage occurs between the belt and the pulley, which may cause belt slippage and, ultimately, belt squeal (abnormal noise).

[0004] In order to prevent such abnormal noise, some have proposed a technique for increasing the engine speed when there is a risk of belt squeal. For example, Patent Document 1 discloses a control device that releases a lock-up clutch interposed between the engine and the transmission when the engine is operating at low speed, thereby increasing the engine speed. This technique can reduce the load torque of the alternator, thereby effectively suppressing belt squeal. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-132929 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the technology of Patent Document 1 is used when the vehicle is not moving and is idling. There is an upper limit to the engine speed that can be increased during idling. Therefore, there are cases where the engine speed cannot be increased to a level that can prevent abnormal noise. In addition, if the engine speed is increased, there is a risk that fuel efficiency will be affected accordingly.

[0007] Therefore, this specification discloses an alternator control device that can prevent abnormal noise without unnecessarily increasing the engine speed. [Means for solving the problem]

[0008] The alternator control device disclosed in this specification is an alternator control device that controls the operation of an alternator that generates electricity using power transmitted from an engine to charge a battery, and is characterized in that when the voltage of the battery is equal to or higher than a specified reference voltage, the engine speed is equal to or lower than a specified reference speed, and the alternator temperature is equal to or lower than a specified reference temperature, the alternator excitation current is limited so that the alternator torque is less than a specified allowable torque.

[0009] In this case, if the amount of power generated by the alternator becomes smaller than the amount of power required by the vehicle load as a result of limiting the excitation current of the alternator, the operation of the vehicle load may be limited. Effect of the Invention

[0010] According to the technology disclosed in this specification, abnormal noise can be suppressed without unnecessarily increasing the engine speed. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a configuration of a power generation system of a vehicle. [Diagram 2] 4 is a graph showing a load torque of an alternator. [Diagram 3] 4 is a flowchart showing a flow of control of an alternator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The control device 26 for the alternator 12 will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of a power generation system for a vehicle. The power generation system includes an engine 10, an alternator 12, a battery 22, and a control device 26. An engine pulley 28 is connected to the engine 10, and an alternator pulley 30 is connected to the alternator 12. A pulley belt 32 is stretched between the engine pulley 28 and the alternator pulley 30, and the rotational power of the engine 10 is transmitted to the alternator 12 via the pulley belt 32. In addition, the output shaft of the engine 10 is connected to the driving wheels 20 of the vehicle via a transmission 14 and a differential device 18. The state of the transmission 14 is changed by a gear shift 16 operated by a user. When "parking" is selected as the gear shift 16, the transmission 14 is locked, and the output power of the engine 10 is not transmitted to the driving wheels 20. On the other hand, when "drive" is selected as the gear shift 16, the output power of the engine 10 is transmitted to the drive wheels 20 via the transmission 14. Hereinafter, the selected state of the gear shift 16 will be referred to as "shift state Sg."

[0013] The alternator 12 generates electric power using power transmitted from the engine 10. More specifically, the alternator 12 includes a rotor that rotates using the power transmitted from the engine 10, a stator including a three-phase winding, a rectifier that rectifies the AC output from the stator to a DC output, and a regulator that controls the excitation current applied to the rotor (none of which are shown). The rotor is provided with a field winding that generates a magnetic flux for inducing a voltage in the stator, and the regulator controls the generated electric power Po of the alternator 12 by controlling the excitation current applied to the field winding.

[0014] The electric power generated by the alternator 12 is stored in the battery 22. The auxiliary load 24 receives electric power from the alternator 12 or the battery 22 to operate.

[0015] The controller 26 controls the operation of the alternator 12, and is physically a computer having a processor and a memory. The controller 26 controls the excitation current Io of the alternator 12 in accordance with the states of the engine 10, the alternator 12, etc.

[0016] Specifically, the battery voltage Vb, the engine speed Ne, and the alternator temperature To are input to the control device 26. When the battery voltage Vb is equal to or higher than a specified reference voltage Vst, the engine speed Ne is equal to or lower than a specified reference speed Nst, and the alternator temperature To is equal to or lower than a specified reference temperature Tst, the control device 26 controls the alternator 12 so that the excitation current Io of the alternator 12 is equal to or lower than an allowable current value Imx. The reason for such a configuration will be described with reference to FIG. 2.

[0017] Fig. 2 is a graph showing the load torque TRQo of the alternator 12. In Fig. 2, the horizontal axis shows the engine speed Ne, and the vertical axis shows the load torque TRQo of the alternator 12. Also in Fig. 2, a curve L1 shows the load torque TRQo when the alternator temperature To is T1, and a curve L2 shows the load torque TRQo when the alternator temperature To is T2, which is sufficiently higher than T1.

[0018] As is clear from Fig. 2, the load torque TRQo is high when the engine speed Ne is low, i.e., when Ne ≈ N1. This speed N1 is generally close to the speed selected during idling. The load torque TRQo is also high when the alternator temperature To is low. Note that the alternator temperature To = T1 on the curve L1 in Fig. 2 is close to the alternator temperature To immediately after the engine is started.

[0019] Here, if the load torque TRQo is high, slippage may occur between the pulley belt 32 and the pulleys 28, 30, causing belt slippage and, ultimately, belt squeal (abnormal noise). In the past, some have proposed setting the engine speed Ne high to prevent such abnormal noise. However, there is an upper limit to the engine speed Ne that can be selected during idling, and it is often impossible to increase the engine speed to a level that can prevent abnormal noise. In addition, if the engine speed Ne is increased, the fuel efficiency of the vehicle is affected accordingly. Therefore, in general, the pulley belt 32 and the pulleys 28, 30 that do not generate abnormal noise, in other words, that can withstand the load torque TRQo, are designed for each combination of the engine 10 and the alternator 12. Therefore, in the case of the prior art, there were many types of pulley belts 32 and pulleys 28, 30 that were handled.

[0020] On the other hand, as described above, the load torque TRQo becomes high when the engine speed Ne is low and the alternator temperature To is low, and this usually occurs only for a short period of time immediately after starting the engine 10. Increasing the number of types of pulley belt 32 and pulleys 28, 30 in order to withstand the load torque TRQo that occurs only for such a short period of time has been pointless.

[0021] Therefore, in this example, when the engine speed Ne is equal to or lower than the reference speed Nst and the alternator temperature To is equal to or lower than the reference temperature Tst, the excitation current Io of the alternator 12 is limited in order to reduce the load torque TRQo. However, when the excitation current Io is limited, the power generation power Po of the alternator 12 decreases accordingly. Therefore, the excitation current Io is limited only when the battery 22 has a sufficient charge amount, that is, when the battery voltage Vb is equal to or higher than the specified reference voltage Vst.

[0022] Specifically, when the limiting conditions of Vb≧Vst, Ne≦Nst, and To≦Tst are satisfied, the control device 26 calculates an excitation current that keeps the load torque TRQo below a specified allowable torque (i.e., a torque that does not cause squealing), i.e., an allowable current value Imx, based on the engine speed Ne and shift state Sg at that time. When the gear shift 16 is in "parking", the load on the engine 10, and therefore the load torque TRQo, is reduced compared to when it is in "drive". Therefore, when the gear shift 16 is in "parking", the allowable current value Imx of the excitation current Io can be set larger than when it is in "drive".

[0023] The control device 26 drives the regulator of the alternator 12 so that the excitation current Io of the alternator 12 does not exceed the calculated allowable current value Imx. This makes it possible to prevent the load torque TRQo from becoming excessively high immediately after the start of the engine 10, and effectively prevents the pulley belt 32 from squealing.

[0024] However, when the excitation current Io is limited, the power generation power Po of the alternator 12 naturally decreases. If the power generation power Po of the alternator 12 is smaller than the power consumed by the auxiliary load 24, the amount of electricity stored in the battery 22 gradually decreases. Therefore, when the excitation current Io is limited, if the power generation power Po of the alternator 12 falls below the power required by the auxiliary load 24, the control device 26 limits the operation of the auxiliary load 24 to reduce the required power Prq. This makes it possible to prevent the amount of electricity stored in the battery 22 from decreasing.

[0025] Next, the flow of control of the alternator 12 by the control device 26 will be described with reference to Fig. 3. This process begins with the start of the engine 10. The control device 26 first checks the battery voltage Vb and compares this battery voltage Vb with a reference voltage Vst (S10). If the comparison shows that the battery voltage Vb is less than the reference voltage Vst, sufficient power generation by the alternator 12 is required, so normal control is performed (S22). In the normal control, the excitation current Io is determined based on the engine speed Ne, the required power Prq, etc.

[0026] On the other hand, when the battery voltage Vb is equal to or higher than the reference voltage Vst, the control device 26 compares the engine speed Ne with the reference speed Nst (S12). When the engine speed Ne exceeds the reference speed Nst, the load torque TRQo is expected to be low, so there is no need to limit the excitation current Io. Therefore, in this case, normal control is performed (S22).

[0027] On the other hand, when the engine speed Ne is equal to or lower than the reference speed Nst, the control device 26 further compares the alternator temperature To with the reference temperature Tst. When the alternator temperature To exceeds the reference temperature Tst, the load torque TRQo is expected to be low, and therefore the control device 26 executes normal control (S22).

[0028] On the other hand, when the alternator temperature To is equal to or lower than the reference temperature Tst, it is expected that the load torque TRQo is likely to become high. In this case, the control device 26 calculates the allowable current value Imx based on the current engine speed Ne and the shift state Sg, and controls the regulator of the alternator 12 so that the excitation current Io is equal to or lower than the allowable current value Imx (S16). That is, in this case, the control device 26 executes a process of limiting the excitation current Io.

[0029] When the limiting process of the excitation current Io is executed, the control device 26 further compares the generated electric power Po of the alternator 12 with the required electric power Prq from the auxiliary load 24 (S18). Then, when the generated electric power Po is less than the required electric power Prq, the control device 26 partially limits the operation of the auxiliary load 24 so as to reduce the required electric power Prq (S20). On the other hand, when the generated electric power Po is equal to or greater than the required electric power Prq, the control device 26 does not limit the auxiliary load 24 and proceeds directly to step S24. In step S24, the state of the engine 10 is confirmed, and if the engine 10 is operating, the process returns to step S10 and the same process is repeated. On the other hand, if the engine 10 is stopped, all the processes are terminated.

[0030] As is clear from the above explanation, in this example, under certain conditions where the load torque TRQo is likely to be high, the excitation current Io is limited, so that abnormal noise can be prevented without unnecessarily increasing the engine speed Ne or without specially designing the pulley belt 32 and the pulleys 28, 30. [Explanation of symbols]

[0031] 10 engine, 12 alternator, 14 transmission, 16 gear shift, 18 differential, 20 drive wheels, 22 battery, 24 auxiliary load, 26 control device, 28 engine pulley, 30 alternator pulley, 32 pulley belt, Ne engine speed, Prq required power, Sg shift state, To alternator temperature, Vb battery voltage.

Claims

1. 1. A control device for an alternator that controls driving of an alternator that generates electricity using power transmitted from an engine to charge a battery, When the voltage of the battery is equal to or higher than a prescribed reference voltage, the rotational speed of the engine is equal to or lower than a prescribed reference rotational speed, and the temperature of the alternator is equal to or lower than a prescribed reference temperature, the excitation current of the alternator is limited so that the torque of the alternator is less than a prescribed allowable torque. The value of the excitation current that becomes less than the specified allowable torque is calculated based on the engine speed and the gear shift selection state at that time.

1. An alternator control device comprising:

2. The alternator control device according to claim 1, 2. An alternator control device comprising: a control circuit for controlling an alternator, the control circuit for controlling an alternator exciting current, the alternator controlling a power supply to the alternator;

3. A control device for an alternator as described in claim 1, 13. An alternator control device according to claim 12, wherein the value of the excitation current that becomes less than the specified allowable torque is set to be larger when the gear shift is in parking position than when the gear shift is in drive position.

Images