Engine starting apparatus

An apparatus for starting an engine, including an inertia-engagement-type starter. In the apparatus, a starter-characteristic switching mechanism is configured to switch an output characteristic of the starter between a plurality of output characteristics including at least a low-torque high-speed characteristic and a high-torque low-speed characteristic, where the output characteristic of the starter is hereinafter referred to a starter characteristic. A timing controller is configured to control when the starter-characteristic switching mechanism switches the starter characteristic such that the starter characteristic is set to the high-torque low-speed characteristic from initiation of actuation of the starter at least until a pinion successfully meshes with a ring gear, and after the pinion has successfully meshed with the ring gear, the starter characteristic is switched from the high-torque low-speed characteristic to the low-torque high-speed characteristic at which the engine is cranked by the starter.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims the benefit of priority from earlier Japanese Patent Applications No. 2014-115563 filed Jun. 4, 2014, the descriptions of which are incorporated herein by reference.

BACKGROUND

Technical Field

The present invention relates to an engine starting apparatus capable of switching an output characteristic of a starter between a low-torque high-speed characteristic and a high-torque low-speed characteristic.

Related Art

Conventionally, there is a desire for an idle-stop-enabled starter to reduce an engine restarting time as much as possible to improve the comfort of a driver or other occupants of a vehicle. A technique for reducing the restarting time includes increasing a cranking speed. Such a technique, however, in combination with good start-up performance at low temperatures where engine friction is high, necessitates use of a large in size and high power motor.

A known technique for increasing the cranking speed at restarting of the engine without increasing dimensions of the motor includes switching as needed between high-speed and high-torque characteristics.

For example, Japanese Patent Application Laid-Open Publication No. 2004-197719 discloses preparing a motor including a series coil and a shunt coil as field coils and switching between the high-speed and high-torque characteristics by an electronic control unit (ECU) controlling field current flowing through the shunt coil of the motor.

The technique disclosed in Japanese patent application laid-open publication no. 2004-197719 can reduce an engine starting time from engine idle stop by setting an output characteristic of the starter at starting of an engine to a high-speed characteristic. At the high-speed characteristic of the starter, however, a rotational speed of a pinion may become too high for the pinion to reliably mesh with a ring gear, which may lead to diminished engagement reliability. A measure to overcome such a disadvantage may include increasing a load of a drive spring for pushing the pinion toward the ring gear at mesh.

Increasing the load of the drive spring, however, necessitates increasing an attraction force of a solenoid for attracting the pinion thereinto against a spring reaction force generated by the drive spring. This may lead to larger dimensions of the solenoid, thus leading to degradation of installation property of the starter and an increased starter cost.

In consideration of the foregoing, exemplary embodiments of the present invention are directed to providing an engine starting apparatus capable of reducing an engine starting time without increasing the size of the solenoid.

SUMMARY

In accordance with an exemplary embodiment of the present invention, there is provided an apparatus for starting an engine, including: an inertia-engagement-type starter configured to utilize an attractive force of a solenoid to push a pinion into an engaged position with a ring gear of the engine and then transfer a rotational force of the motor from the pinion to the ring gear to start the engine; a starter-characteristic switching mechanism configured to switch an output characteristic of the starter between a plurality of output characteristics including at least a low-torque high-speed characteristic and a high-torque low-speed characteristic, the output characteristic of the starter being referred to a starter characteristic; and a timing controller configured to control when the starter-characteristic switching mechanism switches the starter characteristic such that the starter characteristic is set to the high-torque low-speed characteristic from initiation of actuation of the starter at least until the pinion successfully meshes with the ring gear, and after the pinion has successfully meshed with the ring gear, the starter characteristic is switched from the high-torque low-speed characteristic to the low-torque high-speed characteristic at which the engine is cranked by the starter.

In the apparatus configured as above with the engine being cranked at the low-torque high-speed characteristic, the starter characteristic is set to the high-torque low-speed characteristic at least until the pinion successfully meshes with the ring gear. This can reduce the rotational speed of the pinion at mesh as compared to when the pinion meshes with the ring gear at the low-torque high-speed characteristic of the starter. More specifically, the pinion is pushed toward the ring gear by actuation of the solenoid and abuts the ring gear. When the pinion and the ring gear match in meshing phase during the rotation of the pinion, the pinion successfully meshes with the ring gear. The rotational speed of the pinion at mesh is a rotational speed of the pinion at the moment when the pinion successfully meshes with the ring gear. Such a rotational speed of the pinion at mesh is reduced, which can enhance engagement reliability.

In addition, there is no need to increase the load of a drive spring for pushing the pinion toward the ring gear, which can prevent dimensions of the solenoid from increasing. That is, this can reduce an engine starting time without increasing dimensions of the solenoid.

In addition, after the pinion has successfully meshed with the ring gear, the starter characteristic is switched to the low-torque high-speed characteristic at which the engine is cranked. This can reduce an elapsed time from the initiation of actuation of the starter until the engine start. Particularly, in the case of the vehicle with an idle stop system or an automated stop and go system, an elapsed time from the initiation of actuation of the starter until the engine restart can be reduced, which can contribute to enhancement of the comfort of a driver or other occupants of the vehicle.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Some embodiments will now be described by way of example only and with reference to the accompanying drawings.

First Embodiment

An engine starting apparatus of a first embodiment is, as shown inFIG. 1, an inertia-engagement-type starter1, a controller (hereinafter referred to as an electronic control unit (ECU))4configured to control operations of the starter1via starter relays2,3, and a starter-characteristic switching mechanism (described later) configured to switch output characteristics of the starter1(hereinafter referred to as starter characteristics).

The starter1includes a motor5configured to generate a rotational force, an output shaft7to which the rotational force of the motor5is transferred via a variable reducer6(described later), a pinion9configured to transfer a drive torque of the motor5to a ring gear8of an engine, an electro-magnetic solenoid device10(described later), and other components.

The motor5is a brushed direct-current (DC) motor that includes a field element formed of permanent magnets arranged on an inner periphery of a yoke11, an armature14having a commutator13disposed on an armature axis, brushes15configured to slide on the outer periphery of the commutator13as the armature14rotates, and other components. The field element may be a wound field type field element formed of field windings in place of the permanent magnets12.

The output shaft7is arranged coaxially with an armature axis14athrough the variable reducer6. An axial end portion of the output shaft7opposite the motor5is supported by a starter housing17via a bearing16.

The pinion9is straight-splined to an outer periphery of an inner tube18aof a clutch18and urged toward a distal end of the inner tube18a(e.g., a left-hand-side end portion of the inner tube18ainFIG. 1) by a pinion spring19to be in contact with a pinion stopper20attached at the distal end of the inner tube18a.

The clutch18serves as a unidirectional clutch that is helical-splined to an outer periphery of the output shaft7to transfer the motor torque to the pinion9, but interrupts torque transfer from the pinion9to the output shaft7when the pinion9is turned by the engine.

The electro-magnetic solenoid device10includes a solenoid SL1for pushing the pinion9integrally together with the clutch18via a shift lever22in conjunction of movement of the plunger21, and a solenoid SL2for opening and closing main contacts in conjunction of movement of the plunger23.

The main contacts include a pair of stationary contacts electrically connected via two terminal bolts25,26to an energization path for supplying power from a battery24to the motor5, and a movable contact for electrically opening and closing the pair of stationary contacts in conjunction of movement of the plunger23.

The terminal bolts25,26are secured to a resin cover27covering a proximal end portion of the electro-magnetic solenoid device10(e.g., a right-hand-side end portion of the electro-magnetic solenoid device10inFIG. 1). The terminal bolt25is electrically connected to a positive terminal of the battery24via a battery cable28. The terminal bolt26is electrically connected to a positive brush15via a motor lead wire29.

The starter-characteristic switching mechanism of the present embodiment will now be explained.

The starter-characteristic switching mechanism includes the variable reducer6and a mode switcher30configured to switch an operational mode of the variable reducer6between a retarding mode and a non-retarding mode.

The variable reducer6may include a well-known planetary reducer. In the retarding mode of the variable reducer6, rotation of an internally-toothed gear (not shown) of the planetary reducer is restricted. In the non-retarding mode of the variable reducer6, the rotation of the internally-toothed gear of the planetary reducer is unrestricted. The mode switcher30includes, for example a motor actuator (not shown), and is configured to switch the operational mode of the variable reducer6from the retarding mode to the non-retarding mode, or from the non-retarding mode to the retarding mode, in conjunction of the operation of the motor actuator.

In the retarding mode, the rotation of the internally-toothed gear is restricted. Therefore, the variable reducer6serves as a standard speed reducer. That is, the rotational speed of the motor5is reduced by the variable reducer6to be transmitted to the output shaft7.

In the non-retarding mode, the rotation of the internally-toothed gear of the planetary reducer is unrestricted to be able to rotate in an unrestricted manner. Therefore, the variable reducer6does not serve as the speed reducer. That is, as the motor5rotates, constituent gears of the variable reducer6(e.g., the internally-toothed gear, the planetary gear, and a sun gear) rotate integrally together with each other. Therefore, the rotation of the motor5is transmitted to the output shaft7without being reduced by the variable reducer6. That is, the starter characteristic is set to a high-torque low-speed characteristic by the variable reducer6setting the operation mode to the retarding mode, and set to a low-torque high-speed characteristic by the variable reducer6setting the operation mode to the non-retarding mode.

Operation of the starter1, particularly, cranking of the engine at the low-torque high-speed characteristic when the engine is restarted from the engine idle stop, will now be explained.

The ECU4is configured to, upon receipt of an engine restart request, turn on the starter relay2and then the starter relay3.

When the solenoid SL1is activated by turning on the starter relay2, the pinion9is pushed integrally together with the clutch18in the anti-motor direction (e.g., the right-to-left direction inFIG. 1) via the shift lever22. When the pinion9and the ring gear8are out of meshing phase, axial end faces of teeth of the pinion9and axial end faces of teeth of the ring gear8abut each other.

Thereafter, when the solenoid SL2is activated by turning on the starter relay3, the main contacts are closed and the motor5is energized by the battery24to generate a rotational force. The rotational speed of the motor5is reduced by the variable reducer6. The reduced rotation of the motor5is transmitted to the output shaft7, and in turn transferred from the output shaft7to the pinion9via the clutch18. When the pinion9and the ring gear8match in meshing phase during the rotation of the pinion9, the teeth of the pinion are pushed into between respective pairs of adjacent teeth of the ring gear8. The pinion9and the ring gear8thus successfully mesh with each other. Consequently, the motor torque is transferred from the pinion9to the ring gear8to crank the engine.

The variable reducer6is configured in the retarding mode from initiation of actuation of the starter1at least until the pinion9successfully meshes with the ring gear8. After the pinion9successfully meshes with the ring gear8, the variable reducer6is switched into the non-retarding mode. That is, as shown inFIG. 2, the starter characteristic is set to a high-torque low-speed characteristic for a time interval (t1inFIG. 2) from initiation of energization of the solenoid SL1until the pinion9successfully meshes with the ring gear8. During cranking of the engine after the pinion9has successfully meshed with the ring gear8, the starter characteristic is set to a low-torque high-speed characteristic.

When to switch the starter characteristic from the high-torque low-speed characteristic to the low-torque high-speed characteristic may be set by a timer circuit31as a timing controller configured to control when the starter-characteristic switching mechanism (6,30) switches the starter characteristic (seeFIG. 1). More specifically, a time interval (or an elapsed time) from the initiation of energization of the solenoid SL1to when the pinion9successfully meshes with the ring gear8may be counted (by using a timer function of the a timer circuit31) beforehand. The counted time interval may be set in the timer circuit31. As shown inFIG. 1, the timer circuit31is activated in response to an ON-signal to the starter relay2. Upon expiration of the time interval t1(seeFIGS. 2, 3), the motor actuator in the mode switcher30is energized.

Advantages

At restarting of the engine from the idle stop, the starter characteristic is set to the high-torque low-speed characteristic from the initiation of energization of the solenoid SL1at least until the pinion9successfully meshes with the ring gear8, where the rotational speed of the pinion9is set lowest. As shown inFIG. 3, an increase rate of rotational speed of the pinion9is reduced as compared to that of the starter at the low-torque high-speed characteristic. That is, the rotational speed of the pinion9at mesh is reduced as compared to that of the starter at the low-torque high-speed characteristic.FIG. 3is an expanded view of a waveform diagram for a time interval O-T along the time axis (abscissa) shown inFIG. 2. As described above, the pinion9is pushed toward the ring gear8by actuation of the solenoid SL1and abuts the ring gear8. When the pinion9and the ring gear8match in meshing phase during the rotation of the pinion9, the pinion9successfully meshes with the ring gear8. The rotational speed of the pinion9at mesh is a rotational speed of the pinion9at the moment when the pinion9successfully meshes with the ring gear.

In the engine starting apparatus of the first embodiment configured as above, the reduced rotational speed of the pinion at mesh can enhance the engagement reliability. There is thus no need to increase the load of the drive spring32(seeFIG. 1) for pushing the pinion9toward the ring gear8. Therefore, there is no need to increase the attractive force of the solenoid SL1. This can prevent degradation of installation property of the starter without increasing the dimensions of the starter.

In addition, after the pinion9has successfully meshed with the ring gear8, the variable reducer6is switched into the non-retarding mode and the engine is then cranked at the low-torque high-speed characteristic. The cranking speed is thus increased. The increased cranking speed can lead to a reduced engine starting time. Particularly, in the case of the vehicle with the idle stop system or the automated stop and go system, an amount of time from the initiation of actuation of the starter (the initiation of energization of the solenoid SL1in the present embodiment) until the engine restart can be reduced, which can contribute to enhancement of the comfort of a driver or other occupants of the vehicle.

With use of the timer circuit31to switch the operational mode of the variable reducer6(between the retarding mode and the non-retarding mode), when to switch the operational mode of the variable reducer6from the high-torque low-speed characteristic to the low-torque high-speed characteristic can be readily and properly controlled.

In addition, the starter1of the present embodiment uses the brushed DC motor, which allows the engine starting apparatus to be realized with lower cost as compared to when an alternating current (AC) motor is used that uses an inverter for controlling large current.

Other embodiments of the present invention will now be explained with reference to the accompanying drawings. Elements having the same functions as in the first embodiment are assigned the same numbers and will not be described again, for brevity.

Second Embodiment

The starter1of the first embodiment includes the variable reducer6for switching the starter characteristic between the two different characteristics, i.e., the low-torque high-speed characteristic and the high-torque low-speed characteristic. Alternatively, in the second embodiment, a plurality of such variable reducers6may be combined in series with each other, where the operational modes of the respective variable reducers6may be individually switched by the mode switcher30. This allows the starter characteristic to be switched between at least three different characteristics, that is, the starter characteristic may be switched in at least three stages.

With this configuration, the output characteristic of the starter at mesh may be set to an output characteristic that is lower in torque than the highest-torque characteristic and higher in torque than the output characteristic at which the engine is cranked.

At such a high-torque low-speed characteristic, as in the first embodiment, the rotational speed of the pinion at mesh can be reduced, which can enhance the engagement reliability. However, a too high starting torque of the motor5may increase gear-end-face wear between the pinion and the ring gear, leading to reduced durability for maintaining the engagement reliability. To avoid a situation where the starting torque of the motor5becomes too high at mesh, in the second embodiment, the output characteristic of the starter may be set not to the highest-torque characteristic, but to an output characteristic lower in torque than the highest-torque characteristic, that is, a proper-torque characteristic, until the pinion9successfully meshes with the ring gear8. This allows enhancing the engagement reliability by reducing the rotational speed of the pinion at mesh while minimizing an increase of gear-end-face wear to maintain the durability.

Modifications

In the first embodiment, the timer circuit31is used to switch the operational mode of the variable reducer6between the retarding mode and the non-retarding mode. Instead of using the timer circuit31, the ECU4may be used to provide the same function as the timer circuit31. In the first embodiment, the timer circuit31is configured to count the elapsed time t1from the initiation of energization of the solenoid SL1until the starter characteristic is switched from the high-torque low-speed characteristic to the low-torque high-speed characteristic, where the timer circuit31starts time-counting in response to the ON-signal to the starter relay2. Alternatively, the timer circuit31may be configured to count an elapsed time from the initiation of energization of the solenoid SL2until the starter characteristic is switched from the high-torque low-speed characteristic to the low-torque high-speed characteristic, where the timer circuit31may start time-counting in response to an ON-signal to the starter relay3. That is, at time t2after the initiation of the energization of the solenoid SL2(seeFIGS. 2, 3), the motor actuator of the mode switcher30may be energized.

In the first embodiment, the starter-characteristic switching mechanism is configured to switch the starter characteristic from the high-torque low-speed characteristic to the low-torque high-speed characteristic. In the second embodiment, the starter-characteristic switching mechanism is configured to switch the starter characteristic in at least three stages between the high-torque low-speed characteristic and the low-torque high-speed characteristic. Alternatively, the starter-characteristic switching mechanism may be configured to switch the starter characteristic not in the gradually variable manner as in the first and second embodiments, but in a continuously variable manner.

The electro-magnetic solenoid device10of the first embodiment is a tandem-solenoid device including the solenoid SL1for pushing the pinion9toward the ring gear8, and the solenoid SL2for opening and closing the main contacts. Alternatively, instead of using such a tandem-solenoid device10, a conventional electromagnetic switch may be used that is configured to use a single solenoid not only for pushing the pinion9toward the ring gear8, but also for opening and closing the main contacts.