The present invention relates to rotational driving apparatuses for testing internal combustion engines to which a ring gear is attached.
Rotational driving apparatuses for testing internal combustion engines are used to test an internal combustion engine under test by rotating the internal combustion engine without igniting it, that is, they are used when performing so-called xe2x80x98cold testingxe2x80x99. Cold testing includes valve-related testing, such as the timing at which the intake value and the exhaust valve open and close, and testing of the injection nozzle.
An example of such a rotational driving apparatus for an internal combustion engine is disclosed in JP 10-115576A (hereinafter referred to as xe2x80x9cfirst conventional examplexe2x80x9d). The first conventional example is illustrated in FIG. 8. A ring gear 143 is mounted to a crank shaft 141, which is the primary shaft of an internal combustion engine 140 that is in the testing position. A rotor 103 is provided as a part of the rotational driving apparatus, and is rotatively driven about the rotation axis of the ring gear 143 (hereinafter, referred to as the xe2x80x9cring gear rotation axisxe2x80x9d). An engaging member 130 is provided on the rotor 103 and is slidable in the radial direction of the ring gear 143 (hereinafter, referred to as the xe2x80x9cring gear radial directionxe2x80x9d). The engaging member 130 can engage with the ring gear 143 by shifting inwardly in the radial direction. A switching means 110 is provided to shift the engaging member 130 in the ring gear radial direction so as to switch it between an engaged position in which the engaging member 130 engages with the ring gear 143 and a released position in which the engaging member is disengaged. The rotational driving apparatus can rotate the ring gear 143 by rotating the rotor 103 while the engaging member 130 is engaged with the ring gear 143.
The base end of the engaging member 130 is supported only by the rotor 103, and its front end portion is provided with an engaging portion 136 that engages the ring gear 143.
The switching means 110 is provided with a cylindrical body 106 that is fitted, shiftably in the axial direction, to the outside of an output shaft 101 that is rotatively driven about the axis of the rotor 103, that is, about the ring gear rotation axis, and an L-shaped linkage 127 that is pivotably supported on the rotor 103 and that shifts the engaging member 130 in the ring gear radial direction by pivoting. An end portion of the L-shaped linkage 127 engages a groove provided in the circumferential surface of the cylindrical body 106 so that the L-shaped linkage 127 is pivoted as the cylindrical body 106 is shifted in the ring gear rotation axis direction. In FIG. 8, the reference numeral 102 denotes an electric motor that rotatively drives the output shaft 101, and 107 denotes a cylinder with which the cylindrical body 106 can be shifted in the ring gear rotation axis direction.
Also, the rotor 103 is supported rotatively with respect to a frame 111 via bearings 112. The rotor 103 and the cylindrical body 106 are free to move relative to one another in the ring gear rotation axis direction and are connected via a key so that they rotate as a single unit. The cylindrical body 106 is linked to the output shaft 101 so that the two rotate as a single unit.
In other words, in the first conventional example, the L-shaped linkage 127 is pivoted due to the cylinder 107 shifting the cylindrical body 106 in the ring gear rotation axis direction. And through this pivoting, the engaging member 130 is slidably shifted in the ring gear radial direction, switching between the engaged position and the released position.
Another conventional example of a rotational driving apparatus is disclosed in JP H02-13732A (hereinafter referred to as xe2x80x9csecond conventional examplexe2x80x9d). FIG. 9 shows the second conventional example. In FIG. 9, a ring gear 225 is mounted to a primary shaft (crank shaft) 213 of an internal combustion engine (not shown) in the testing position. This rotational driving apparatus is provided with a shaft-shaped rotor 228 that is rotatively driven about the rotation axis of the ring gear 225 (hereinafter, referred to as the xe2x80x9cring gear rotation axisxe2x80x9d). It is also provided with an engaging member 236 that is pivotably supported on the rotor 228 so that it can be shifted in the radial direction of the ring gear 225 (hereinafter referred to as the ring gear radial directionxe2x80x9d), and that can engage the ring gear 225 by shifting inward with respect to the radial direction. The rotational driving apparatus is also provided with a switching means 240 that shifts the engaging member 236 in the ring gear radial direction so that it is switched between an engaged position in which it engages the ring gear 225, and a released position in which it is disengaged. The ring gear 225 can be rotated by rotating the rotor 228 with the engaging member 236 engaged with the ring gear 225.
A base end of the engaging member 236 on the inward side with respect to the ring gear radial direction is pivotably supported on the rotor 228, and the front end of the engaging member 236 on the outward side with respect to the ring gear radial direction forms an L-shape that is bent towards the ring gear 225 direction along the ring gear rotation axis direction. An engaging portion 239 that engages the ring gear 225 is provided at the front end of the engaging member 236.
The switching means 240 is provided with a cylindrical body 232 that is fitted to the outside of the rotor 228 such that it can be shifted in the axial direction, that is, in the ring gear rotation axis direction, and a disk-shaped rotating member 234 that is rotatable relative to the cylindrical body 232 via bearings and that is mounted in an outside fitting state such that it is shiftable in the ring gear rotation axis direction. The fore end portion of the rotating member 234 is pivotably linked to an intermediate portion of the engaging member 236 via link pins 235. By shifting the cylindrical body 232 in the ring gear rotation axis direction, the engaging member 236 is switched between the engaged position and the released position.
In FIG. 9 the reference numeral 212 denotes an electric motor that rotatively drives the rotor 228, and 244 denotes a cylinder with which the cylindrical body 232 can be shifted in the ring gear rotation axis direction and that is operatively connected to the cylindrical body 232 via a pivot link 242, which pivots about a pivot shaft 241.
In other words, according to the second conventional example, the engaging member 236 is pivoted in the ring gear radial direction due to the cylinder 244 shifting the cylindrical body 232 in the ring gear rotation axis direction, switching the engaging member 236 between the engaged position and the released position.
Conventionally, an internal combustion engine was tested by running the internal combustion engine at low speeds of about 1200 rpms, for example. However, in order to achieve complete test results and increase the testing accuracy, for example, it is desirable to test the internal combustion engine also at high speeds, such as at 4000 rpms.
In the first conventional example mentioned above, when the internal combustion engine is run at high speeds, the large centrifugal force causes the engaging member, which is supported with respect to the rotor such that it can be slideably shifted in the ring gear radial direction, to shift outward with respect to ring gear radial direction. In order to counter this large centrifugal force and hold the engaging member in the engaged position, it is necessary to increase the control force of the cylinder so that there is a sufficiently large enough control force keeping the engaging member inward in the ring gear radial direction. However, increasing the control force for keeping the engaging member inward in the ring gear radial direction not only makes the structure of the apparatus complex but may also damage the ring gear due to the strong force at which the ring gear is pushed inward in the radial direction by the engaging member in a stopped state, in which the ring gear is not rotated, and in a low-speed rotation state, in which the ring gear is rotated at a low speed. Thus, the configuration of the first conventional example was not suited for running an internal combustion engine at high speeds.
Moreover, also in the second conventional example mentioned above, when the internal combustion engine is run at high speeds, the large centrifugal force causes the engaging member, which is supported with respect to the rotor such that it is pivotable in the ring gear radial direction, to move outward in ring gear radial direction. In order to counter this large centrifugal force and hold the engaging member in the engaged position, as in the first conventional example, it is necessary to increase the control force of the cylinder so that there is a sufficiently large enough control force to keep the engaging member inward in the ring gear radial direction. The result was that the configuration of the second conventional example, like the configuration of the first conventional example, was not suited for running an internal combustion engine at high speeds.
Consequently, there is a need for rotational driving apparatuses for testing internal combustion engines whose structure is suited for testing internal combustion engines at high speeds as well as at lower speeds.
The present invention was arrived at in light of the foregoing problems, and it is an object thereof to provide a rotational driving apparatus for testing an internal combustion engine with which the internal combustion engine can be rotated at high speeds as well as at lower speeds.
A rotational driving apparatus according to the present invention has a rotor that is rotatively driven about a rotation axis of the ring gear, and a pivot portion supported in a support position with respect to the rotor. The support position is located substantially away from a front end and a rear end of the pivot portion in the direction of the rotation axis of the ring gear. An engaging portion is provided at the front end region of the pivot portion with respect to the ring gear. Consequently, when the rotor is rotated, a torque in the direction in which the engaging portion is caused to engage the ring gear is generated by a portion between the support position and the rear end of the pivot portion. This torque cancels out at least a portion of a torque generated at a portion on the front end side of the pivot portion. Consequently, the control force that is required to displace the engaging portion is reduced, even if the rotor is rotated at high speeds.
In an embodiment of the present invention, a link that is operatively connected to the pivot portion directly or indirectly is employed so as to manipulate the engaging portion between an engaged position in which it engages the ring gear and a non-engaged position. This link is also joined to a reciprocating member that is shifted in the direction of the rotation axis by an actuator. The angle that is formed between the link and the rotation axis is preferably large. Thus, the horizontal component of the total torque generated by the centrifugal force that acts on the pivot portion is reduced before being transmitted to the reciprocating member, and thus the effects, when running at high speeds, of the centrifugal force on the control force for engaging the engaging portion with the ring gear can be further reduced.
The following description of the embodiments according to the present invention made with reference to the drawings is provided for illustration only, and not for the purpose of limiting the invention, which is defined by the claims.