JP6465381B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus.

As a general electric power steering device, for example, a column assist type that adds a driving force of an electric motor to a steering column, a pinion assist type that adds a driving force of an electric motor to a pinion gear, and an electric motor to a rack gear There is a rack assist type or the like that adds a driving force.
Specifically, for example, as in the invention described in Patent Document 1, there has been an electric power steering device in which an electric motor applies a driving force of the electric motor to a steering column via a worm gear.

JP 2003-175851 A

However, in the form of adding the driving force described in Patent Document 1, since the driving force of the electric motor is once transmitted to the worm gear and then from the worm gear to the steering column, the driving force is applied with a delay from the steering operation. Has been made.
Due to this delay in addition, the driving force of the electric motor is added in the middle of the steering operation. Therefore, before and after the driving force is applied, there is a possibility that an uncomfortable feeling such as a sudden reduction in the heavy steering feeling may occur.

  Therefore, the problem to be solved by the present invention is to provide an electric power steering device that has little or no discomfort in the steering feeling before and after the addition of the driving force of the electric motor.

As means for solving the above-mentioned problems, an electric power steering device according to the present invention is a steering device that extends in the vertical direction of a vehicle, has one end connected to a rotatable steering wheel, and transmits the rotational force of the steering wheel. A column and a pinion gear that is connected to the other end of the steering column and can be rotated by transmitting the rotational force of the steering wheel, and a tire is connected to the left and right ends extending in the left-right direction of the vehicle. When the rotational force of the steering wheel is transmitted, the rack can move in the left-right direction, and the rack gear that can turn the tire by the movement, the plurality of electric motors having substantially the same rotational torque, and the operation of the steering wheel An ECU for simultaneously adding a current for driving the electric motor to a plurality of electric motors; The provided, rotation to the steering column and the pinion gear, and, with respect to any one of the moving rack gear is meshed directly like at least one of the electric motor to transmit the driving force faster than the other electric motor, other electric electric motor is engaged to add a driving force through a transmitting member for transmitting delayed while amplifying the driving force, with the operation of the steering wheel, the driving force of at least one electric motor of the other It is added prior to the driving force of the motor.

The electric power steering apparatus according to the present invention, an auxiliary for the pinion gear meshing with the rack gear in a position different from the pinion gear, the other electric motor is preferably that will be engaged in the auxiliary pinion gear through the transmission member.

  In the electric power steering apparatus according to the present invention, the transmission member is preferably a worm gear.

  According to the present invention, the electric motor includes the electric motor that directly adds the driving force and the electric motor that indirectly performs the transmission via the transmission member. When the driving force of an electric motor is directly applied to a rotating steering column or the like without passing through a transmission member, the delay from when the steering operation is made until the driving force is applied, compared to the case through a transmission member Is reduced or eliminated. Therefore, when the steering operation is started, the addition of the driving force is also started quickly. Therefore, it is possible to provide an electric power steering device with little or no sense of incongruity in the steering feeling before and after the addition of the driving force of the electric motor.

FIG. 1 is a schematic view showing an embodiment of an electric power steering apparatus according to the present invention. FIG. 2 is a graph showing the relationship between the steering angle in the steering operation of the conventional electric power steering apparatus and the torque required for the steering operation. FIG. 3 is a schematic view showing another embodiment of the electric power steering apparatus according to the present invention. FIG. 4 is a schematic view showing another embodiment of the electric power steering apparatus according to the present invention.

  An embodiment of an electric power steering apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing an embodiment of an electric power steering apparatus according to the present invention. FIG. 1 shows a vehicle equipped with an electric power steering device as viewed from the front.

  As shown in FIG. 1, the electric power steering apparatus 1 includes a steering wheel 2, a steering column 3, a pinion gear 4, a rack gear 5, an auxiliary pinion gear 6, an electric motor 7, and a worm gear 8.

  The steering wheel 2 is a rotatable member and is rotated by an occupant during a steering operation. The steering wheel 2 and the steering column 3 are disposed so as to protrude into the passenger compartment, which is a region where the passenger sits when riding, and the remaining members such as the pinion gear 4, the rack gear 5, the auxiliary pinion gear 6, the electric motor 7 and the worm gear 8 are It is provided outside the passenger compartment.

The steering column 3 extends in the vertical direction of the vehicle, and has an upper end connected to the steering wheel 2 and the other end connected to the pinion gear 4. In the embodiment shown in FIG. 1, the other end located below the steering column 3 is connected to a pinion gear 4 described later via an appropriate connecting member such as a torsion bar 9. The torsion bar 9 is a rod-like member capable of torsional rotation, and transmits the rotational force transmitted from the steering column 3 to the pinion gear 4.
The torsion bar 9 is electrically connected to the torque sensor 10, and the degree of twist of the torsion bar 9 is detected by the torque sensor 10. The torque sensor 10 is electrically connected to an ECU (engine control unit) 11 and inputs the degree of torsion of the torsion bar 9 detected by the torque sensor 10 to the ECU 11 as a torque signal. The ECU 11 is electrically connected to the electric motor 7. The electrical relationship between the ECU 11 and the electric motor 7 will be described later together with the description of the electric motor 7.
As the torsion bar 9, the torque sensor 10, and the ECU 11, existing ones incorporated in a normal electric power steering apparatus can be used.
1 is an example of a steering column in the electric power steering apparatus according to the present invention.

The pinion gear 4 is a member that is connected to the other end of the steering column 3 via a torsion bar 9 and is rotatable about an axis when the rotational force of the steering wheel 2 is transmitted. The rotational force of the steering wheel 2 is transmitted to the pinion gear 4 via the steering column 3 and the torsion bar 9. As the pinion gear 4, a general pinion gear can be used, and a groove in an oblique direction with respect to the axis is formed on the peripheral surface of the rod-shaped body.
The pinion gear 4 shown in FIG. 1 is an example of a pinion gear in the electric power steering device according to the present invention.

The rack gear 5 is a member that extends in the left-right direction of the vehicle, is connected to tires 12 at both left and right ends, and meshes with the pinion gear 4. Further, the rack gear 5 is movable in the left-right direction when the rotational force of the steering wheel 2 is transmitted, and the tire 12 can be turned by the movement in the left-right direction. The rotational force of the steering wheel 2 is transmitted to the rack gear 5 via the steering column 3, the torsion bar 9 and the pinion gear 4. As the rack gear 5, a general rack gear can be used, and a groove is formed so as to be substantially orthogonal to the axis along the major axis direction of the rod-shaped body.
When the pinion gear 4 to which the rotational force is transmitted from the torsion bar 9 rotates, the rack gear 5 that meshes with the pinion gear 4 slides so as to be delivered in either the left or right direction.
Tires 12 are attached to the left and right ends of the rack gear 5 via appropriate connecting members such as tie rods (not shown). As a result, the steering operation input to the steering wheel 2 can be transmitted to the tire 12 via the steering column 3, the torsion bar 9, the pinion gear 4, and the rack gear 5.
1 is an example of a rack gear in the electric power steering apparatus according to the present invention.

The auxiliary pinion gear 6 meshes with the rack gear 5 at a position different from the pinion gear 4 that is indirectly or directly connected to the steering wheel 2, the steering column 3, and the torsion bar 9. In the embodiment shown in FIG. 1, the pinion gear 4 is provided on the right side in the vehicle left-right direction, which is the same side as the side on which the steering wheel 2 is provided, whereas the auxiliary pinion gear 6 is provided on the left side in the vehicle left-right direction. Is provided.
The embodiment shown in FIG. 1 is a pinion assist type electric power steering device because the electric motor 7 is attached to the pinion gear 4 and the auxiliary pinion gear 6.
The auxiliary pinion gear 6 is driven to the pinion gear 4 when adopting the pinion assist type, particularly when there is no region for attaching a member such as the electric motor 7 around the pinion gear 4 or from the viewpoint of improving the stability of the steering operation. This is a member that is preferably provided when additional driving force is required in addition to the addition of force. When the column assist type and the rack assist type are adopted, the auxiliary pinion gear 6 does not need to be provided.
The auxiliary pinion gear 6 shown in FIG. 1 is an example of the auxiliary pinion gear in the electric power steering apparatus according to the present invention.

In the embodiment shown in FIG. 1, two electric motors 7 are provided, and the driving force of the electric motor 7 is applied to the rotating pinion gear 4 and the auxiliary pinion gear 6. As shown in FIG. 1, the electric motor 7 includes a first electric motor 71 and a second electric motor 72. The first electric motor 71 and the second electric motor 72 have basically the same function and the same performance, and the connected members and the members that transmit the driving force are different.
Specifically, the first electric motor 71 is directly connected to the pinion gear 4, while the second electric motor 72 is indirectly connected to the auxiliary pinion gear 6 via a worm gear 8 described later. The As a result, the first electric motor 71 directly applies driving force to the pinion gear 4, while the second electric motor 72 indirectly applies driving force to the auxiliary pinion gear 6 via the worm gear 8. To do.
The first electric motor 71 and the second electric motor 72 are examples of the electric motor in the electric power steering apparatus according to the present invention.

In this embodiment, when the electric motor 7 is directly connected to an appropriate member such as the steering column 3 and the driving force of the electric motor 7 is directly applied, the shaft periphery and the tip of the rotating shaft of the electric motor 7 Generally, even if a driving force is applied to the steering column 3 or the like via fixedly attached gears, it is assumed that it is directly applied.
In the case where another member such as a worm gear 8 is interposed between the generally attached gears and the steering column 3 or the like, they are indirectly connected and the drive force is also indirectly added. I will do it. The other member is a member that is not fixedly attached to the rotating shaft of the electric motor, for example, and can delay the addition of the driving force to the steering column 3 or the like.

The worm gear 8 is provided so as to be fewer than the electric motor 7, and one worm gear 8 is provided in the present embodiment. Of the pinion gear 4 and auxiliary pinion gear 6 to which the electric motor 7 applies driving force, the worm gear 8 is attached to the auxiliary pinion gear 6 to which the second electric motor 72 applies driving force. The worm gear 8 is interposed between the second electric motor 72 and the auxiliary pinion gear 6, and transmits the driving force of the second electric motor 72 to the auxiliary pinion gear 6.
As the worm gear 8, a general worm gear can be used, and the torque generated by the second electric motor 72 can be amplified and transmitted to the auxiliary pinion gear 6.
The worm gear 8 is an example of a transmission member in the electric power steering apparatus according to the present invention, and can transmit a rotational force generated by the electric motor to another member as a driving force in addition to the worm gear used in a reduction gear or the like. Any member can be used, and appropriate gears can be used.

As described above, the electric motor 7 and the ECU 11 are electrically connected. When a torque signal is input from the torque sensor 10 to the ECU 11, the ECU 11 adds a current corresponding to the vehicle speed at the time when the steering operation is performed to the first electric motor 71 and the second electric motor 72. The first electric motor 71 and the second electric motor 72 to which the current is added generate a driving force based on rotational torque.
The driving force generated by the first electric motor 71 is transmitted to the pinion gear 4 as a rotational force. Further, the rotational force of the pinion gear 4 is transmitted as a force that moves the rack gear 5 along the left-right direction of the vehicle. Further, the driving force generated by the second electric motor 72 is amplified by a worm gear 8 incorporated in an appropriate reduction gear and then transmitted as a rotational force to the auxiliary pinion gear 6, and further from the auxiliary pinion gear 6 to the rack gear 5. It is transmitted as a force in the vehicle left-right direction.

In the conventional electric power steering apparatus, for example, there are many forms in which one or a plurality of electric motors and worm gears are provided, that is, the same number of electric motors and worm gears are provided. When a steering operation is performed in this conventional form, first, an electric current is added from the ECU to the electric motor. Next, rotational torque is generated as a driving force by the operation of the electric motor. Further, the driving force is transmitted from the electric motor to the worm gear. Finally, the driving force of the electric motor is applied to the rotating or moving member to which the worm gear is attached to the member to which the worm gear is attached from the worm gear.
That is, the driving force of the electric motor is not transmitted directly from the electric motor to a member to which a driving force such as a steering column is to be added, but is transmitted with a slight delay from the steering operation by the presence of the worm gear. It was.
When a steering operation such as stationary is performed, since the degree of driving force of the electric motor required for the electric power steering device is large, the electric motor and the worm gear are basically provided as a pair of members. It was.

Here, a graph showing the relationship between the steering angle in the steering operation of the conventional electric power steering apparatus and the torque required for the steering operation is shown in FIG. The steering angle in the steering operation is a rotation angle from the initial state of the steering wheel 2.
Conventionally, when the steering wheel 2 is rotated to an appropriate steering angle as shown in FIG. 2, an inflection point X at which the inclination of the graph changes may occur. This inflection point X occurs when the driving force of the electric motor is actually applied by transmitting the driving force of the electric motor to the member to which the electric motor is attached.

In the region A of the steering angle near the inflection point X and smaller than the inflection point X, it is difficult for the occupant performing the steering operation to rotate the steering wheel 2 and feels heavy. Region A is a state where the addition of the driving force of the electric motor has not started.
Further, in the region B of the steering angle near the inflection point X and larger than the inflection point X, it feels that the steering wheel 2 that was heavy for the occupant performing the steering operation has become lighter at a stroke. Region B is a state in which application of the driving force of the electric motor is started.
The change that suddenly lightened from the heavy steering feeling before and after the addition of the driving force of the electric motor led to an uncomfortable feeling of steering for the occupant.

  Therefore, in the past, the driving force was added via the worm gear as an additional form of the driving force of the electric motor. Therefore, the driving force is added in the middle of the steering operation by adding the driving force delayed by the amount corresponding to the worm gear from the start of the steering operation. There was a sense of incongruity of the steering feeling before and after the addition of.

In the embodiment shown in FIG. 1, the first electric motor 71 is provided on the pinion gear 4 without the worm gear 8, so that the driving force of the first electric motor 71 is quickly transmitted to the pinion gear 4. Therefore, the start timing of the addition of the driving force by the first electric motor 71 is accelerated by the amount not passing through the worm gear 8. That is, in this embodiment, the time difference from the start of the steering operation to the start of the addition of the driving force is smaller than in the conventional case.
Thereby, the inflection point X shown in FIG. When the inflection point X does not occur, the steering wheel 2 in the steering operation does not change lightly from a heavy state, so that there is no sense of discomfort in the steering feeling for the occupant.
Further, in the present embodiment, even if the inflection point X is generated, the addition of the driving force of the electric motor is made earlier than in the prior art, so the inflection point X is smaller than that shown in FIG. And further to the low torque side of the torque required for the steering operation. As a result, the steering wheel 2 needs only to be changed so that the steering wheel 2 becomes slightly lighter at an early time after the steering operation is started.

  In the present embodiment, since the driving force of the first electric motor 71 is quickly applied, the responsiveness of the operation in which the tire 12 changes its direction according to the steering operation is favorable with respect to the steering operation.

  In the present embodiment, the addition of the driving force of the first electric motor 71 is achieved quickly because the worm gear 8 is not used. That is, the first electric motor 71 and the second electric motor 72 do not perform separate control on the start timing of the addition of the driving force, but the addition of the driving force of the first electric motor 71 drives the second electric motor 72. It precedes the addition of power.

Furthermore, in this embodiment, when a current is simultaneously applied to the first electric motor 71 and the second electric motor 72, the driving force of the first electric motor 71 provided without the worm gear 8 is transmitted via the worm gear 8. It is added before the driving force of the second electric motor 72 provided. Therefore, if current is simultaneously applied to the first electric motor 71 and the second electric motor 72, the driving force of the second electric motor 72 is also added later, so that a large torque is applied in the steering operation. It is possible to cope with the case where it is necessary.
Further, since the driving force of the second electric motor 72 that is added later is amplified by the worm gear 8, it is suitable for a steering operation that requires a large torque including stationary driving and sudden steering.

  Subsequently, an embodiment different from the embodiment shown in FIG. 1 is shown as a schematic diagram in FIGS. 3 and 4.

A difference between the embodiment shown in FIG. 3 and the embodiment shown in FIG. 1 is a portion where the worm gear 8 is provided. Since the same member is used except this difference, the detailed description regarding a common member is abbreviate | omitted.
In the embodiment shown in FIG. 3, a worm gear 8 is interposed between the first electric motor 71 and the pinion gear 4. The second electric motor 72 is directly connected to the auxiliary pinion gear 6.

Even if the position where the worm gear 8 is provided is different, the embodiment shown in FIG. 3 has the same function and action as the embodiment shown in FIG. That is, the driving force of the second electric motor 72 provided without using the worm gear 8 is quickly transmitted to the auxiliary pinion gear 6. Therefore, the normal steering operation performed during traveling or the like is performed in a heavy state during the steering operation as shown by the inflection point X shown in FIG. It is difficult or unlikely that changes that suddenly become lighter will occur.
Further, even when a steering operation that requires a large torque, such as stationary driving or sudden steering, is performed, the driving force of the first electric motor 71 is amplified by the worm gear 8 and transmitted to the pinion gear 4. The operation can be performed smoothly, and the torque required for the steering operation can be reduced as a whole.

The difference between the embodiment shown in FIG. 4 and the embodiment shown in FIG. 1 is a portion where an electric motor is provided and a portion where a worm gear is provided. Since the same member is used except this difference, the detailed description regarding a common member is abbreviate | omitted.
In the embodiment shown in FIG. 4, worm gears 8 and 81 are interposed between the first electric motor 71 and the pinion gear 4 and between the second electric motor 72 and the auxiliary pinion gear 6, respectively. The third electric motor 73 is directly connected to the steering column 3, and the fourth electric motor 74 is directly connected to the rack gear 5. The worm gear 8 and the worm gear 81 use the same type of worm gear, and are merely attached to different members.
In the embodiment shown in FIG. 4, the electric motor 7 is attached to all of the steering column 3, the pinion gear 4, the auxiliary pinion gear 6 and the rack gear 5, so that it becomes a combined type of column assist type, pinion assist type and rack assist type. ing.

Even if the positions where the worm gears 8 and 81 are provided are different, the embodiment shown in FIG. 4 eventually has the same functions and operations as the embodiment shown in FIG. That is, the driving forces of the third electric motor 73 and the fourth electric motor 74 provided without the worm gears 8 and 81 are quickly transmitted to the steering column 3 and the rack gear 5. Therefore, in a normal steering operation performed during traveling or the like, since the quick driving force is quickly applied by the third electric motor 73 and the fourth electric motor 74, the steering is performed as shown by the inflection point X shown in FIG. A change that suddenly becomes lighter from a heavy state during operation is difficult or does not occur.
Further, even when a steering operation that requires a large torque, such as stationary driving or sudden steering, is performed, the driving force of the first electric motor 71 and the second electric motor 72 is amplified by the worm gears 8 and 81 and then the pinion gear. 4 and the auxiliary pinion gear 6, the steering operation can be performed smoothly, and the torque required for the steering operation as a whole can be reduced.

  In the present invention, any member that does not include the worm gear may be used. For example, an electric motor may be provided at four locations of the steering column 3, the pinion gear 4, the auxiliary pinion gear 6, and the rack gear 5, and only the rack gear 5 may be provided with a worm gear.

  Furthermore, as long as two or more electric motors are provided, the number and arrangement thereof are not limited. Since the total number of electric motors is two or more, for example, when the auxiliary pinion gear 6 is provided as in the embodiment shown in FIG. 1, if one electric motor is provided in the auxiliary pinion gear 6, the steering Another electric motor may be provided in at least one of the column 3, the pinion gear 4, and the rack gear 5.

  In addition, the member that interposes the worm gear and the member that does not intervene are not particularly limited. For example, in the case of an engine car, the size of the area where the worm gear can be installed in the engine room in front of the passenger compartment. It can be determined according to the cost, mass, and required driving performance of the vehicle, etc. In addition, since the magnitude | size of the driving force transmitted to the member to which the driving force of a vehicle's mass and gravity center and an electric motor are added changes with arrangement | positioning of a worm gear, the driving | running performance requested | required of the vehicle to which this invention is applied. The arrangement and number of worm gears are preferably determined accordingly.

When three or more electric motors are provided as in the embodiment shown in FIG. 4, the driving force of one or two electric motors is added in a steering operation that requires a large torque, such as a normal steering operation and a stationary operation. May be enough. In this case, at least one of the first electric motor 71, the second electric motor 72, the third electric motor 73, and the fourth electric motor 74 may be used as the backup electric motor. Specifically, the electric motor used as a spare does not basically operate, and it is only necessary that the electric motor other than the spare be activated for the first time when a normal operation cannot be performed due to some factor. . Providing a spare electric motor is preferable because the driving safety performance of the vehicle is further improved.
Even if a spare electric motor is provided, as long as the electric power steering apparatus according to the present invention is applied, as an electric motor other than the spare, an electric motor with a worm gear interposed therein and an electric motor without a worm gear interposed therebetween. A motor is disposed. Therefore, not only does the steering feeling feel uncomfortable during the steering operation, but also the steering operation requiring a large torque, such as a stationary stop, can be performed smoothly.

  In the electric power steering apparatus according to the present invention, there is a form in which the auxiliary pinion gear 6 is not provided. As this form, the form which an electric motor adds a driving force with respect to at least 2 of the steering column 3, the pinion gear 4, and the rack gear 5 can be mentioned, for example. Even in this form, the driving force is directly applied to at least one of the steering column 3, the pinion gear 4 and the rack gear 5 without the worm gear, so that the uncomfortable feeling of steering can be reduced or eliminated without any problem. Steering operation that requires a large torque, such as stationary, can be performed smoothly.

  When the steering-by-wire format is adopted as the power steering format, a plurality of electric motors are provided. Even in this case, it is preferable to apply the electric power steering device according to the present invention. By applying the present invention to the steering-by-wire format, it is possible not only to make or not cause a sense of incongruity with respect to the steering feeling in the steering operation, but also to smoothly perform a steering operation that requires a large torque, such as a stationary operation.

  As mentioned above, although embodiment which applied the invention made | formed by this inventor was described, this invention is not limited by the description and drawing which make a part of indication of this invention by this embodiment. That is, it should be added that other embodiments, examples, operation techniques, and the like made by those skilled in the art based on this embodiment are all included in the scope of the present invention.

1: electric power steering device, 2: steering wheel, 3: steering column, 4: pinion gear, 5: rack gear, 6: auxiliary pinion gear, 7: electric motor, 71: first electric motor, 72: second electric motor, 73: Third electric motor, 74: Fourth electric motor, 8 and 81: Worm gear, 9: Torsion bar, 10: Torque sensor, 11: ECU, 12: Tire

Claims (3)

A steering column that extends in the vertical direction of the vehicle, has one end connected to a rotatable steering wheel, and transmits the rotational force of the steering wheel;
A pinion gear that is connected to the other end of the steering column and is rotatable by transmitting the rotational force of the steering wheel;
A tire is connected to both left and right ends extending in the vehicle left-right direction, meshed with a pinion gear, and can move in the left-right direction when the rotational force of the steering wheel is transmitted, and the tire can be turned by this movement Rack gear,
A plurality of electric motors having substantially the same rotational torque;
An ECU for simultaneously adding current to drive the plurality of electric motors to the plurality of electric motors by operating the steering wheel,
Rotation to the steering column and the pinion gear, and, with respect to any one of the moving rack gear is meshed directly like at least one of the electric motor to transmit the driving force faster than the other electric motor, other electric motor There are meshed to add a driving force through a transmitting member for transmitting delayed while amplifying the driving force,
With the operation of the steering wheel, the driving force of at least one electric motor is added prior to the driving force of the other electric motors.
Electric power steering device. It has an auxiliary pinion gear that meshes with the rack gear at a position different from the pinion gear,
Other electric motor, Ru is meshed with auxiliary pinion gear through the transmission member,
The electric power steering apparatus according to claim 1. The transmission member is a worm gear,
The electric power steering apparatus according to claim 1 or 2.

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