GB2400157A

GB2400157A - Electronic throttle assembly

Info

Publication number: GB2400157A
Application number: GB0307565A
Authority: GB
Inventors: Paul David Sims; Nathan Andrew Skinner; James Justin Tindall; Alan David Graham
Original assignee: Visteon Global Technologies Inc
Current assignee: Visteon Global Technologies Inc
Priority date: 2003-04-02
Filing date: 2003-04-02
Publication date: 2004-10-06
Also published as: GB0307565D0

Abstract

An electronic throttle assembly (1) suitable for use in automotive applications comprising an air inlet passageway (2), a valve member for controlling air flow through the passageway (2), a throttle shaft (18) operationally linked to the valve member for rotation about a first axis (6), a drive motor (8), and a gear mechanism (16, figure 3). The gear mechanism (16) comprising a drive gear (48) and a driven gear (32) for transmitting mechanical power between the drive motor (8) and the throttle shaft (18). The drive gear (48) is powered by the motor (8) and arranged to rotate about a second axis (10). The first and second axes (6,10) are transverse, preferably orthogonal and non-intersecting. The drive motor (8) is preferably co-axial with the second axis (10). The gear mechanism (16) preferably comprises a conically tapered worm gear (48) and hypoid-offset spiral bevel gear (32). The drive motor (8) and drive gear (48) may be located on opposite sides of the driven gear (32).

Description

Electronic Throttle Assembly The present invention relates to an

electronic throttle assembly, and particularly to an electronic throttle assembly for use in automotive applications.

Electronic throttle assemblies provide significant advantages over mechanically driven throttles. For example, in a motor vehicle having an electronic throttle, there is no need for a direct mechanical linkage from an accelerator pedal to the throttle body, and this allows greater freedom in the placement of the throttle body, as well as permitting an electronic engine control unit (ECU) to control the throttle.

An electronic throttle assembly will include a drive motor arranged to activate a value member, which is usually a near-circular throttle flap in an air inlet duct for an internal combustion engine. A drive motor should be compact and hence may have relatively low power, and may have insufficient torque to turn a throttle shaft directly under all operating conditions, particularly if there is a build up of ice around the throttle valve.

The need for increased torque together with the need for precise control of the throttle setting means that conventional motor vehicle electronic throttle assemblies have a step down gear arrangement between the motor and the throttle member. The conventional arrangement is to have a series of parallel axis gears, which may drive a sector gear on a throttle shaft; see, for example, the disclosure in patent document EP 1 099 842 A2. Such electronic throttle assemblies provide the benefit of being compact, due to the - 2 close proximity of the gearing arrangement with the throttle flap, and also the side-by-side arrangement of the motor and air inlet passageway, made possible by the fact that the motor and throttle shaft have parallel rotational axes.

However, a problem with all such electronic throttle assemblies is the need for very tight dimensional tolerances in the gearbox, both to deal with teeth clatter and wear, and to reduce hysteresis in the movement of the throttle flap.

The accuracy of the gearing arrangement has to be maintained over the expected lifetime of the product. The difficulty of this problem is greater if the assembly is made from a moulded plastic and/or if plastic moulded gearing components or bearings are used in an attempt to reduce the cost of the assembly.

It is an object of the present invention to provide a more convenient and economical electronic throttle assembly for a motor vehicle.

According to the invention, there is provided an electronic throttle assembly, comprising an air inlet passageway, a valve member for controlling air flow through the passageway, a throttle shaft operationally linked to the valve member and being arranged to rotate about a first axis to move the valve member between an open orientation in which air flow is admitted through the passageway and a closed orientation in which air flow through the passageway is restricted, a drive motor, and a gear mechanism, wherein: - the gear mechanism comprises a drive gear and a driven gear for transmitting mechanical power between the drive motor and - 3 the throttle shaft; - the drive gear is powered by the drive motor and is arranged to rotate about a second axis; - the driven gear meshes with the drive gear and is arranged to rotate the throttle shaft to move the valve member between an open and a closed orientation; and - the second axis and the first axis are transverse to each other.

This arrangement provides a number of benefits. First, it is possible to achieve the same or a comparable step-down gearing ratio with two such transverse gear members, as compared with the three such parallel gear members used in conventional gear assemblies. For example, a gear arrangement with three parallel axis gear members may achieve a step down ratio of between 17:1 and 18:1. The two transverse gear arrangement of the present invention may be designed to have a step down ratio of between 13:1 and 16:1 and achieve comparable performance.

In general, errors in tolerances between multiple interlinked components tend to add together, rather than to cancel out.

Therefore, because the arrangement reduces the number of gears, it is easier to maintain alignment between the gear members over time, particularly when the gear arrangement is fabricated in a moulded plastic material.

The arrangement also permits the motor to be mounted transversely to an axis of the air inlet passageway. Usually, - 4 the valve member will be a circular or near-circular throttle flap. In prior art arrangements, the close proximity of the drive motor and the air inlet passageway, necessary to maintain close parallel axis alignment between the various gear members, will restrict the maximum diameter of the air inlet passageway. Therefore, the transverse arrangement of the present invention permits the cross-sectional area or diameter of the air inlet passageway to be increased, which will reduce air friction within the walls of the air inlet passageway and increase the responsiveness and maximum air flow through the passageway, thereby increasing engine performance.

A further advantage is that the arrangement permits greater commonality of components if it is desired to manufacture a range of electronic throttle assemblies having different size air inlet passageways. For the reasons described above, in the prior art, this would necessitate having alternative orientations and configurations of certain components, such as the drive motor, to allow larger air inlet passageways.

This leads to increased product complexity and hence cost. . In contrast, in the transverse arrangement of the present invention, all that is necessary is that the mechanical linkage, such as a drive shaft, between the motor and drive gear is changed along with the air inlet passage and throttle flap.

The gear arrangement may be a right anglec/offset arrangement, consisting of a driven gear and drive pinion.

The pinion has fewer teeth than the gear and is pre e-ably of parallel or tapered screw form. The driven gear may He a face type similar to a hypoid-offset spiral bevel. - 5

This arrangement offers a wide range of gear ratios, with a greater number of continuously meshing teeth, than for a conventional worm gear of similar size, resulting in higher strength and smoothness of action from a compact design.

Also, mounting requirements for such a gear arrangement are not as critical as for bevel or hypoid gears, ensuring maximum accuracy and positive backlash control.

In a preferred embodiment of the invention, the drive motor is coaxial with the second axis. This simplifies the mechanical linkage and alignment between the drive motor and the drive gear. In addition, the first and second axes are preferably orthogonal.

Also in a preferred embodiment of the invention, the first and second axes are offset, that is, non-intersecting.

It is particularly advantageous if the drive gear is a worm gear and the driven gear is a spiral face type gear. This arrangement provides advantages in terms of increased contact area between gear teeth, as multiple teeth on opposite gears may have portions in contact at the same time. This results in smooth running of the gears, with a reduced emphasis on manufacturing variability as well as a higher capability of transfer of mechanical power from the drive gear to the driven gear under the action of the drive motor, or from the driven gear to the drive gear, for example under the action of a spring driven return mechanism.

The spiral face type gear may have gear teeth that extend in a plane which is perpendicular to the first axis and which 6 - extends along the second axis. The plane of the gear teeth may be angled relative to the direction of the second axis, but is preferably parallel with the second axis, in which case the first axis and the second axis will be orthogonal and offset relative to one another.

The drive motor is preferably coaxial with the second axis.

Then, in one embodiment of the invention, the drive motor and the drive gear are both on one side of a point of closest approach between the first axis and the second axis. This provides the benefit of reducing the length of the mechanical linkage between the drive motor and the drive gear, which potentially makes for a more compact arrangement of the gears.

However, in an alternative embodiment of the invention, the drive motor is on one side of a point of closest approach between the first axis and the second axis, and the drive gear is on the other side of a point of closest approach between the first axis and the second axis. The gear arrangement will normally be surrounded by a gear housing, and this arrangement therefore makes is easier to use part of the gear housing as a bearing for the drive gear, which can help to maintain alignment between the drive gear and the driven gear.

The invention will now be further described, by way of example only, w th reference to the accompanying drawings, in which: Figure 1 shows a perspective view of an electronic throttle assembly according to a first embodiment of the 7 - invention, having an air inlet passageway, a throttle flap that is rotatable along a first axis, a drive motor extending along a second, transverse axis, and a gear housing containing a gear mechanism linked to the throttle flap and the drive motor) Figures 2 and 3 are a side views of the electronic throttle assembly of Figure 1, showing respectively a housing cover in place and removed to expose a transverse gear arrangement comprising a drive gear connected to the drive motor and a driven gear connected to a throttle shaft) Figure 4 is a cross-section view of the electronic throttle assembly of Figure 1, taken along the first axis through the throttle shaft as indicated by the line IV-IV of Figure 3, showing also part of the driven gear and a spring return mechanism; Figure 5 is a rear view of the driven gear from the same direction as in Figure 3i Figure 6 is a front view of the driven gear, from the opposite direction of Figure 5, showing a face type gear similar to a hypoid-offset spiral bevel gear; Figure 7 is a plan view of the driven gear, taken along the line VII-VII of Figure 6i Figure 8 is a cross-section view of the dr ven gear, taken along the line VIII-VIII of Figure 6; - 8 Figures 9 and 10 are perspective views of, respectively, the front and rear sides of the driven gear; Figures 11 and 12 are perspective views of, respectively, the front and rear sides of the housing cover; Figure 13 is a perspective view of an electronic throttle assembly according to a second embodiment of the invention; and Figure 14 is an exploded perspective view of the electronic throttle assembly of Figure 13, which as shown differs from the first embodiment mainly in the arrangement of the drive gear and the driven gear.

Figures 1 to 4 show a various views an electronic throttle assembly 1, having an air inlet passageway 2, inside of which is a throttle flap 4 which is rotatable about a first axis 6.

A drive motor 8 extends along a second axis 10 that extends orthogonally to the first axis 6. The first and second axes 6,10 are laterally offset with respect to each other, so that these are non-intersecting.

The electronic throttle assembly 1 comprises a main body 12 that can be moulded in a durable plastic material such as glass reinforced Polyetherimide (PET). The body 12 defines the air inlet passageway 2, as well as part of a housing 14 for a gear assembly 16. A throttle shaft 18 extends through the main body along the first axis 6. A throttle flap 4 is connected to the throttle shaft 18 by means of two screws 20.

The throttle she t 18 is rotationally supported by a pair of 9 cylindrical bearings 22,23 seated in corresponding cylindrical bearing recesses 24,25 in the main body 12.

One end 26 of the throttle shaft 18 is rotationally engaged with a rotational movement sensor 28 that is secured to the main body 12. The sensor 28 provides a signal to an engine control unit (not shown) indicative of the rotational orientation of the throttle shaft 18 and hence the throttle stop 4.

The other end 30 of the throttle shaft 18 is connected to a driven gear 32 of the gear assembly 16. The driven gear is shown in more detail in Figures 5 to 10.

The air passageway 2 has a stepped cylindrical bore 33 that extends along a third throttle bore axis 34. The throttle bore axis 34 intersects with and is orthogonal to the first axis 6. The bore 33 has a circular crosssection in the plane of the throttle flap 4. The non-circular flap lies at a small angle to the main bore, such that it appears circular when viewed from the direction of airflow. The shape provides a small clearance between the throttle flap 4 and the mid- portion of the bore 35 in order to prevent jamming of the throttle flap 4 in the air passageway 2 when this is closed.

As shown in Figure 3, the gear assembly 16 comprises in addition to the driven gear 32 mounted on the end 30 of the throttle shaft 18, a worm gear 40 which is mounted on a drive shaft 42 from the drive motor 8. As shown in Figure 4, the first axis 6 about which the driven gear 32 rotates is offset by a distance (d) as indicated by arrow 44. The point along the second axis 10 at which the second axis 10 is closest to - 10 the first axis 6 is denoted in Figure 4 by 10'. In the first embodiment 1 of the electronic throttle assembly, the worm gear 40 lies on a side of the point 10' of closest approach between the first and second axes 6, 10 closest to the motor 8. The worm gear 40 therefore engages with a portion of the driven gear that lies between the point 10' and the drive motor 8.

As shown most clearly in Figures 6 and 9, the driven gear 32 is a face type gear having a set of teeth 46 extending along an annular arc which is centered about the first axis 6 and which lies in a plane perpendicular to the direction of the first axis 6. The teeth 46 are oriented in the direction towards the air passageway 2, and the worm gear 40 therefore lies between the face type gear 32 and the air passageway 2.

It would, however, be possible for the teeth 46 of the face type gear 32 to be oriented in the opposite direction, that is, away from the air passageway 2, in which case the face type gear 32 would lie between the worm gear 40 and the air passageway 2.

In either case, the drive gear 40 acts as a pinion gear which is rightangled to the face type gear 32. Because the worm drive gear 40 is offset from the driven gear 32, the worm gear here is a conically tapered worm. gear providing a number of parallel engaging teeth 48, and the face type gear 32 is a similar to a hypoid-offset spiral bevel gear. This arrangement offers a wide range of potentially achievable gear ratios, with a greater number of continuously meshing teeth 46,48, both on the drive gear 40 and driven ge- 32, as compared with a cylindrical worm gear of similar size. This results in a more secure engagement between the teeth 46,48 - 11 of the driving and driven gears 40,32, and a greater smoothness of action together with a compact design. In addition, the mounting requirements for the driving and driven gears 40,32 are not as critical as for other types of gear arrangements, ensuring maximum accuracy and positive backlash control.

The gear mechanism 16 also has a coil spring 50 which is seated between a cover 52 on the gear housing 14, and the driven gear 32. The housing cover is shown in more detail in Figures 11 and 12. The ends of the coil spring 50 are engaged with both the housing cover 52 and driven gear 32, so that as the driven gear 32 rotates 54 the throttle flap 4 over 90 between a closed orientation in which airflow through the air inlet 2 is severely restricted, and an open orientation in which the throttle flap 4 extends along the air inlet access 34, the coil spring 50 becomes wound. Therefore, if the drive motor 8 fails, the throttle flap 4 is automatically moved back towards the closed position.

The rotational freedom of the throttle shaft 18, and hence throttle flap 4, is restrained by a pair of end stops 56,57 that extend radially from the driven gear 32, and which alternatively come into contact with a projection 58 that extends radially inwards from an inner surface 59 of the gear assembly housing 14. One of these end stops 56 has a tangentially extending recess 60 that engages with a straight end (not shown) of the spring 50. The gear housing cover 52 has a similar tangential feature 62 to capture an opposite straight end (not shown) of the spring 50, so that the straight ends of the spring 50 are prevented from movement as a spring 50 is wound when the driven gear 32 rotates from an orientation in which the throttle flap 4 is closed through 90 to an orientation in which the throttle flap 4 is open in the air passageway 2. The spring 50 when wound provides a sufficient spring bias to return the throttle flap 4 to a closed orientation in the event that electric control of the drive motor 8 fails.

The gear assembly cover 52 will normally be permanently affixed to the gear housing 14; however a housing may have a removable end cap 65 as shown in Figure 4, by which the moving components of the gear assembly 16 may be lubricated.

The electronic throttle assembly 1 is assembled in the following manner. First, the throttle shaft 18 is inserted through the air passageway 2, and oriented with an axial slot 64 oriented along the axis 34 of the air passageway 2. A throttle flap 4 is then inserted through the slot 64 and then the screws 20 used to secure the throttle flap 4 to the throttle shaft 18. The throttle shaft bearings 22,23 are inserted over the ends 26,30 of the throttle shaft 18 and seated in the corresponding bearing recesses 24,25. The driven gear 32 is then inserted over the end 30 of the throttle shaft 18. With the throttle shaft 4 in the closed orientation, the spring 50 is inserted between the gear housing cover 52 and the driven gear 32 such that there is a residual biasing force maintaining the driven gear 32 in the closed orientation with the end stop 56 is against the projection 58 in the flap closed orientation. The housing cover 52 is then permanently affixed to the housing portion 14 of the main body 12, for example by gluing or Ultrasonic welding. - 13

The driving worm gear 40 is tapered so that a narrow end of the gear is directed along the drive axis 10 towards a correspondingly bevelled profile of the driven gear teeth 46.

This permits the drive motor 8 and drive gear 40 to be brought up against the main body 12 along the drive axis 10 until the spiral teeth 48 of the drive gear 40 mesh with the bevelled spiral face type teeth 46 of the driven gear 32.

Screws 66 are then used to secure a drive motor 8 with the main body 12 of the electronic throttle assembly 1.

Finally, the rotational sensor 28 is offered up along the throttle shaft axis 6 to engage rotationally with the end 26 of the throttle shaft 18, whereupon screws 68 are used to secure the sensor 28 to the main body 12 of the electronic throttle assembly 1.

The electronic throttle assembly 1 is designed for use in an automotive application to control a flow of air into an internal combustion engine (not shown). In use, a flexible hose (not shown) would be secured to one end 70 of the air passageway 2, and the opposite end 71, would be mounted to the engine intake manifold (not shown).

Figures 13 and 14 show a second embodiment of an electronic throttle assembly 101, in which features similar to those of the first embodiment 1 are indicated by reference numerals incremented by 100. The electronic throttle assembly 101 differs from the first embodiment 1 mainly in the form of the driven gear 132 and the drive gear 140 of the gear assembly 116. As with the first embodiment 1, the drive gear 140 is a conically tapered worm gear, and the driven gear 132 is a face type gear having a hypoid-offset spiral bevel - 14 arrangement of gear teeth 146. In this arrangement, however, the worm drive gear 140 is at the end of an extended drive shaft 142 so that the drive gear 140 extends beyond the point 110' at which the drive axis 110 is closest to the throttle shaft axis 106. The driven gear 132 therefore has spiral face type gear teeth 146 arranged along an annular arc that is also on the far side of the point 110' from the drive motor 108. The bevel on these teeth 146 is, however, in the opposite direction so that a similarly tapered shape of the drive gear 140 permits the drive gear teeth 148 to mesh with the driven gear teeth 146 when the drive motor 108 is brought up against the main body 112 along the drive axis 110.

An advantage of this arrangement is that the drive gear 140 has a bearing end 80 that engages with a similar cylindrical bearing 82 in a cylindrical bearing recess 84 in the inner wall 159 of the gear assembly housing 114. This accurately locates and secures the drive gear 140 relative to the driven gear 132.

The embodiments of the invention 1,101 provide a number of advantages over an electronic throttle assembly having a number of gears arranged along parallel axes. Because only two gears are required, there is a reduced part count and a simplified mechanical arrangement with fewer bearings, which reduces manufacturing cost while at the same time allowing tolerances to be met in the various components. Most of the components, including the drive and driven gears 40,140, 32,132 can be manufactured from a durable plastics materials, for example glass reinforced nylon. Because the drive motor 8,108 extends along an axis 10,110 transverse to both the throttle valve axis 6,106 and air passageway axis 34,134, it is possible to increase the diameter of the air inlet 102.

For example, in the illustrated examples 1,101, the air inlet 2,102 can have a diameter of between 70 mm and 120 mm. This improves air flow characteristics into an internal combustion engine. The invention therefore provides a convenient and economical electronic throttle assembly for a motor vehicle. - 16

Claims

Claims: 1. An electronic throttle assembly, comprising an air inlet

passageway, a valve member for controlling air flow through the passageway, a throttle shaft operationally linked to the valve member and being arranged to rotate about a first axis to move the valve member between an open orientation in which air flow is admitted through the passageway and a closed orientation in which air flow through the passageway is restricted, a drive motor, and a gear mechanism, wherein: the gear mechanism comprises a drive gear and a driven gear for transmitting mechanical power between the drive motor and the throttle shaft; - the drive gear is powered by the drive motor and is arranged to rotate about a second axisi - the driven gear meshes with the drive gear and is arranged to rotate the throttle shaft to move the valve member between an open and a closed orientation; and - the second axis and the first axis are transverse to each other.
2. An electronic throttle assembly as claimed in Claim 1, in which the drive motor is coaxial with the second axis.
3. An electronic throttle assembly as claimed in Claim 1 or Claim 2, in which the first and second axes are orthogonal.
4. An electronic throttle assembly as claimed in any preceding claim, in which the first and second axes are non-intersecting.
5. An electronic throttle assembly as claimed in Claim 4, in which the drive gear is a worm gear and the driven gear is a spiral face type gear.
6. An electronic throttle assembly as claimed in Claim 5, in which the spiral face type gear has gear teeth that extend in a plane which is perpendicular to the first axis and which extends along the second axis.
7. An electronic throttle assembly as claimed in Claim 6, in which the plane of the gear teeth is parallel with the second axis.
8. An electronic throttle assembly as claimed in Claim 6 or Claim 7, in which the drive motor is coaxial with the second axis, and the drive motor and the drive gear are both on one side of a point of closest approach between the first axis and the second axis.
9. An electronic throttle assembly as claimed in Claim 6 or Claim 7, in which the drive motor is coaxial with the second axis, and the drive motor is on one side of a point of closest approach between the first axis and the second axis, and the drive gear is on the other side of a point of closest approach between the first axis and the second axis.
10. An electronic throttle assembly as claimed in any preceding claim, in which the drive gear is a conically - 18 tapered worm gear.
11. An electronic throttle assembly as claimed in any preceding claim, in which the driven gear is a hypoid-offset spiral bevel gear.
12. An electronic throttle assembly as claimed in any preceding claim, in which the driven gear is on the throttle shaft.
13. An electronic throttle assembly as claimed in any preceding claim, in which the dive motor has a drive shaft, and the drive gear is on the drive shaft.
14. An electronic throttle assembly, substantially as herein described, with reference to or as shown in the accompanying drawings.