Electric parking lock apparatus

An electric parking lock apparatus includes a parking mechanism, an electric actuator, an engagement member, a first urging member, and a first electromagnetic solenoid. The parking mechanism includes a parking gear and a parking pawl. The engagement member includes first and second engagement elements. The first engagement element includes a proximal end coupled to the first urging member. The second engagement element includes a proximal end coupled to a brake pedal of the vehicle. In a state of power supply failure, the first electromagnetic solenoid allows the first engagement element to swing in the direction for engaging with the second engagement element. In the state of power supply failure, the engagement elements engage with each other when the brake pedal is released from a depressed state, and the parking pawl is caused to swing in a direction for engaging with the parking gear as the brake pedal is released.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent Application No. 2021-155275 filed on Sep. 24, 2021, the entire contents of which are hereby incorporated by reference.

BACKGROUND

The disclosure relates to an electric parking lock apparatus.

An automatic transmission according to the related art includes a parking lock apparatus that locks a parking gear fitted to an output shaft of the automatic transmission when a parking (P) range is selected. In recent years, automatic transmissions including a shift-by-wire (SBW) mechanism have been commercialized. In such an automatic transmission, a range selected by a driver is detected with a switch or the like, and the shift-by-wire (SBW) mechanism changes a range of the automatic transmission by driving an electric actuator, such as an electric motor, based on the result of the detection.

When, for example, the P range is selected, the electric shift-by-wire mechanism (parking lock apparatus including an electric actuator) drives the electric actuator, such as an electric motor, to swing a parking pawl and lock the parking gear. When a range other than the P range is selected, the electric actuator, such as an electric motor, is driven to unlock the parking gear.

In an electric parking lock apparatus, there is a possibility that parking lock cannot be released if a power supply failure occurs while the parking gear is locked. The power supply failure may occur due to, for example, an abnormality in a battery, disconnection or short-circuiting of a power supply line (harness), or a rupture of a main fuse. Accordingly, for example, Japanese Unexamined Patent Application Publication (JP-A) No. 2018-65519 and Japanese Unexamined Patent Application Publication (JP-A) No. 2000-85552 propose electric parking lock apparatuses including a manual lock releaser that enables a manual operation for releasing the parking lock when a power supply failure occurs.

SUMMARY

An aspect of the disclosure provides an electric parking lock apparatus including a parking mechanism, an electric actuator, an engagement member, a first urging member, and a first electromagnetic solenoid. The parking mechanism includes a parking gear and a parking pawl and is configured to lock the parking gear by engaging the parking pawl with the parking gear to set a vehicle to a parking state. The electric actuator is configured to swing the parking pawl to lock the parking gear. The engagement member includes a first engagement element and a second engagement element in pairs that are engageable with each other. The first urging member is provided at a distal end of the parking pawl, and configured to apply an urging force to the first engagement element so that the first engagement element swings in a direction for engaging with the second engagement element. In an energized state, the first electromagnetic solenoid is configured to retain the first engagement element against the urging force of the first urging member so that the first engagement element does not swing. The first engagement element includes a proximal end coupled to the first urging member. The second engagement element includes a proximal end coupled to a brake pedal of the vehicle. In a state of power supply failure, the first electromagnetic solenoid allows the first engagement element to swing in the direction for engaging with the second engagement element in response to the urging force of the first urging member. In the state of power supply failure, the first engagement element and the second engagement element engage with each other in a case where the brake pedal is released from a depressed state, and the parking pawl is caused to swing in a direction for engaging with the parking gear as the brake pedal is released from the depressed state.

DETAILED DESCRIPTION

A power supply failure may occur while the parking gear is not locked, that is, in an unlocked state. In such a case, there is a possibility that the electric actuator, such as an electric motor, cannot be driven, and the parking gear cannot be locked. However, JP-A No. 2018-65519 and JP-A No. 2000-85552 do not describe any operation of locking the parking gear when a power supply failure occurs in the unlocked state.

It is desirable to provide an electric parking lock apparatus capable of semi-automatically locking a parking gear if a power supply failure occurs while the parking gear is not locked (unlocked state).

The configuration of an electric parking lock apparatus1according to an embodiment will be described with reference toFIGS.1to3.FIG.1illustrates the configuration of a shift-by-wire mechanism2included in the electric parking lock apparatus1.FIG.2is a schematic diagram illustrating the configuration of a lock mechanism3for use in a state of power supply failure in the electric parking lock apparatus1(normal power supply state (energized state)).FIG.3is a schematic diagram illustrating the configuration of the lock mechanism3for use in the state of power supply failure in the electric parking lock apparatus1(state of power supply failure (non-energized state)).

When a parking (P) range is selected, the shift-by-wire mechanism (parking mechanism)2included in the electric parking lock apparatus1locks rotation of an automatic transmission so that wheels do not rotate. Referring toFIG.1, a shift-by-wire control unit (hereinafter referred to as “SBW-CU”)20drives an electric actuator15(for example, an electric motor) having an output shaft to which a detent plate14is attached. The detent plate14is coupled to a parking rod13that is movable back and forth in an axial direction. A parking gear12is spline-fitted to, for example, an output shaft of the automatic transmission. The parking gear12is provided with a parking pawl11that is swingable to engage with the parking gear12.

When the parking (P) range is selected, the electric actuator15(electric motor) is rotated to swing the detent plate14so that the parking rod13moves in the axial direction. Accordingly, a tapered unit of the parking rod13pushes the parking pawl11from behind, so that the parking pawl11swings and engages with the parking gear12. As a result, rotation of the automatic transmission is locked. When the vehicle is moving at a speed higher than or equal to a predetermined speed, the parking pawl11is snapped back by the parking gear12and cannot engage with the parking gear12.

If a power supply failure occurs due to, for example, an abnormality in a battery, disconnection or short-circuiting of a power supply line (harness), or a rupture of a main fuse, there is a possibility that the SBW-CU20and the electric actuator15described above cannot be operated. In other words, there is a possibility that the parking gear12cannot be locked or unlocked (released from a locked state). The electric parking lock apparatus1has a function of semi-automatically locking the parking gear12(parking lock) when a power supply failure occurs while the parking gear12is not locked (unlocked state).

The electric parking lock apparatus1includes the lock mechanism3for use in the state of power supply failure. As illustrated inFIGS.2and3, the lock mechanism3for use in the state of power supply failure mainly includes a first urging member31, a second urging member32, an engagement member33, an elastic member34, a first electromagnetic solenoid41, and a second electromagnetic solenoid42.

The engagement member33includes a pair of engagement elements331and332(first engagement element331and second engagement element332) engageable with each other. The first engagement element (engagement lug)331and the second engagement element (engagement lug)332each have a distal end that is hook-shaped or wedge-shaped, for example. When the outer surfaces of the distal ends of the first and second engagement elements331and332are in contact with each other, for example, when a power supply failure occurs while a brake pedal60is not depressed, the first and second engagement elements331and332are movable (slidable) along contact surfaces thereof.

A proximal end of the first engagement element331is coupled to a first urging member31provided at a distal end of the parking pawl11. A proximal end of the second engagement element332is coupled to the brake pedal60with a wire51.

An elastic member34that is expandable and contractible (for example, a coil spring) is disposed between the proximal end of the first engagement element331and the first urging member31provided at the distal end of the parking pawl11. A contraction force (spring force) of the elastic member34is greater than an urging force of the second urging member32. The contraction force (spring force) of the elastic member34is set so that the elastic member34expands and does not lock the parking gear12when the parking pawl11is snapped back by the parking gear12.

The first urging member31is composed of, for example, a coil spring and is provided at the distal end of the parking pawl11. The first urging member31applies an urging force to the first engagement element331of the engagement member33so that the first engagement element331swings in a direction for engaging with (approaching) the second engagement element332.

In a normal power supply state (energized state), a plunger, for example, of the first electromagnetic solenoid41projects outward. Accordingly, the first engagement element331is retained against the urging force of the first urging member31so that the first engagement element331does not swing. Thus, the first and second engagement elements331and332are restrained from engaging with each other.

In the state of power supply failure (non-energized state), the plunger of the first electromagnetic solenoid41is retracted (contained) in the first electromagnetic solenoid41. Accordingly, the first engagement element331is enabled to swing in a direction for engaging with (approaching) the second engagement element332in response to the urging force of the first urging member31. In other words, the first and second engagement elements331and332are enabled to engage with each other. Therefore, the pair of engagement elements331and332engage with each other when the brake pedal60is released from a depressed state in the state of power supply failure (non-energized state). As the brake pedal60is released from a depressed state, that is, as the brake pedal60returns to a brake pedal position, the parking pawl11is pulled by the wire51and caused to swing in a direction for engaging with the parking gear12.

The second urging member32is composed of, for example, a coil spring and is provided at a proximal end of the parking pawl11(swing center axis). The second urging member32applies an urging force to the parking pawl11in a direction such that the parking pawl11moves away from the parking gear12, that is, such that the lock is released.

In the normal power supply state (energized state), a plunger, for example, of the second electromagnetic solenoid42is retracted (contained) in the second electromagnetic solenoid42. Accordingly, the parking pawl11is enabled to move away from the parking gear12(lock can be released) in response to the urging force of the second urging member32. In the state of power supply failure (non-energized state), the plunger of the second electromagnetic solenoid42projects outward. Accordingly, the parking pawl11is retained against the urging force of the second urging member32so that the parking pawl11is retained in a parking lock state (engaged with the parking gear12).

The electric parking lock apparatus1also includes a release member (release lever)43that mechanically cancels the parking state maintained by the second electromagnetic solenoid42in the state of power supply failure (non-energized state). In one example, the release member43is coupled to the plunger of the second electromagnetic solenoid42with a wire or the like. When the release member43is pulled, the plunger of the second electromagnetic solenoid42is pulled (retracted) into the second electromagnetic solenoid42. As a result, the parking pawl11moves away from the parking gear12in response to the urging force of the second urging member32, and the lock is released.

According to the above-described configuration, in the state of power supply failure, as illustrated inFIG.3, the plunger of the first electromagnetic solenoid41is pulled (retracted) into the first electromagnetic solenoid41. Accordingly, the first engagement element331is enabled to swing in the direction for engaging with the second engagement element332in response to the urging force of the first urging member31.

The proximal end of the first engagement element331is coupled to the first urging member31provided at the distal end of the parking pawl11, and the proximal end of the second engagement element332is coupled to the brake pedal60with the wire51. Therefore, when the brake pedal60is released from the depressed state afterwards, the pair of engagement elements331and332engage with each other, and the parking pawl11swings in the direction for engaging with the parking gear12as the brake pedal60is released from the depressed state. As a result, the parking gear12is locked (parking lock) in response to releasing of the brake pedal60from the depressed state, that is, semi-automatically.

In the state of power supply failure, the plunger of the second electromagnetic solenoid42projects outward. Accordingly, the parking pawl11is retained in the parking lock state against the urging force of the second urging member32. Even in the state of power supply failure, when the release member43is pulled, the plunger of the second electromagnetic solenoid42is pulled (retracted) into the second electromagnetic solenoid42. Accordingly, the parking pawl11moves away from the parking gear12in response to the urging force of the second urging member32, and the lock is released.

In the normal power supply state (energized state), as illustrated inFIG.2, the plunger of the second electromagnetic solenoid42is retracted (contained) in the second electromagnetic solenoid42, and the plunger of the first electromagnetic solenoid41projects outward. Therefore, the parking pawl11is enabled to swing, and the first engagement element331is retained against the urging force of the first urging member31so that the first engagement element331does not swing, that is, so that the first and second engagement elements331and332do not engage with each other. Therefore, as described above, the parking gear12is locked or unlocked in response to an operation of the electric actuator15.

As described above, according to the present embodiment, in the state of power supply failure, the first engagement element331is enabled to swing in the direction for engaging with the second engagement element332in response to the urging force of the first urging member31. The proximal end of the first engagement element331is coupled to the first urging member31provided at the distal end of the parking pawl11, and the proximal end of the second engagement element332is coupled to the brake pedal60with the wire51. Therefore, when the brake pedal60is released from the depressed state afterwards, the pair of engagement elements331and332engage with each other, and the parking pawl11swings in the direction for engaging with the parking gear12as the brake pedal60is released from the depressed state (return to the brake pedal position). As a result, even when a power supply failure occurs while the parking gear12is not locked (unlocked state), the parking gear12can be semi-automatically locked by releasing the brake pedal60from the depressed state.

In the normal power supply state (energized state), the plunger of the second electromagnetic solenoid42is retracted (contained) in the second electromagnetic solenoid42, and the plunger of the first electromagnetic solenoid41projects outward. Therefore, the parking pawl11is enabled to swing, and the first engagement element331is retained against the urging force of the first urging member31so that the first engagement element331does not swing, that is, so that the first and second engagement elements331and332do not engage with each other. Therefore, the parking gear12is locked or unlocked in response to an operation of the electric actuator15.

According to the present embodiment, the first and second engagement elements331and332each have a hook-shaped or wedge-shaped distal end. When the outer surfaces of the distal ends of the first and second engagement elements331and332are in contact with each other, for example, when a power supply failure occurs while a brake pedal60is not depressed, the first and second engagement elements331and332are movable along contact surfaces thereof. Therefore, even when a power supply failure occurs while the brake pedal60is not depressed, the parking lock can be set by depressing the brake pedal60and then releasing the brake pedal60from the depressed state.

According to the present embodiment, the second urging member32and the second electromagnetic solenoid42are provided. The second urging member32applies an urging force to the parking pawl11in a direction such that the parking pawl11moves away from the parking gear12. In the energized state, the second electromagnetic solenoid42enables the parking pawl11to move away from the parking gear12in response to the urging force of the second urging member32. In the state of power supply failure, the second electromagnetic solenoid42retains the parking pawl11in the parking lock state against the urging force of the second urging member32. Therefore, even when a power supply failure occurs, the parking lock state can be maintained against the urging force of the second urging member32.

According to the present embodiment, the expandable and contractible elastic member34is also provided. The elastic member34is disposed between the proximal end of the first engagement element331and the first urging member31provided at the distal end of the parking pawl11. The contraction force of the elastic member34is greater than the urging force of the second urging member32. Therefore, for example, when a power supply failure occurs while the vehicle is moving and when the parking pawl11is snapped back by the parking gear12, the elastic member34expands to prevent the parking gear12from being locked. When the parking pawl11is not snapped back by the parking gear12, the locked state can be established and maintained.

According to the present embodiment, the release member43is also provided. The release member43mechanically cancels the parking state maintained by the second electromagnetic solenoid42in the state of power supply failure. Therefore, even in the state of power supply failure, the lock can be canceled (unlocked).

Although an embodiment of the disclosure has been described, the disclosure is not limited to the above-described embodiment, and various modifications are possible. For example, the shapes of the first and second engagement elements331and332are not limited to those in the above-described embodiment. In addition, for example, the arrangement of the first and second electromagnetic solenoids41and42is not limited to that in the above-described embodiment.

The system configuration of the above-described embodiment is an example, and the system configuration of the disclosure is not limited to that in the above-described embodiment. For example, the SBW-CU20and the electric actuator15may be integrated together.

The disclosure may also be applied to a vehicle in which no automatic transmission is mounted. Examples of such a vehicle include an electric vehicle (EV) that directly drives wheels with an electric motor or the like, a fuel cell vehicle (FCV), and a series hybrid electric vehicle (SHEV).