JP2785425B2 - Variable compression ratio device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an internal combustion engine (hereinafter referred to as "engine"
) Variable compression ratio device.

<Prior Art> Conventionally, knocking has not been generated in a high load range or a high engine speed range that is larger than an engine middle load range, and a fuel efficiency has been improved by increasing thermal efficiency in an operation range below a medium load. For this purpose, various engines capable of changing the compression ratio have been proposed.

Such a variable compression ratio mechanism is disclosed, for example, in Japanese Patent Publication No. 63-32972. The compression ratio variable mechanism disclosed in this publication includes an eccentric bearing that eccentrically aligns a bearing hole of the connecting rod and a support shaft inserted through the bearing hole with one of the shaft support portions at both ends of the connecting rod of the engine,
The rotation from the eccentric bearing is provided by driving the lock pin that is movable in the bearing radial direction by providing a free rotation by the rotational force generated by eccentricity of the load from the piston and the reaction force from the support shaft. A hydraulically operated locking means for switching between free and fixed is provided, and the pressure of the working oil supplied to the locking means is controlled by a computer which receives signals from the piston position detecting means and the operating condition detecting means. According to the above signal, control is performed under the condition that the hydraulic pressure is always applied to the lock means during the lock and the hydraulic pressure is not applied to the lock means during the unlocking.

However, in such a conventional variable compression ratio mechanism of an internal combustion engine, the rotation of the eccentric bearing is switched between free and fixed by driving the lock pin in the bearing radial direction. Therefore, there is a possibility that the operation of the lock pin becomes uncertain due to the influence of the inertial force generated due to the reciprocating motion of the connecting rod and the like.

In addition, since the rotation of the eccentric bearing in the high rotation state is stopped only by the lock pin, a large impact may act on the lock pin at the time of the stop, which may cause an operation failure, resulting in poor durability. There was a problem. Further, it is difficult to control the stop drive of the eccentric bearing in the lock pin,
The device becomes complicated.

The present invention is intended to solve such a problem, and it is intended to prevent the locking and unlocking operations by the locking means from becoming uncertain due to the centrifugal force and the acceleration of the connecting rod reciprocating motion, and to improve the durability. To provide a variable compression ratio device for an internal combustion engine.

<Means for Solving the Problems> A variable compression ratio apparatus for an internal combustion engine according to the present invention for solving the above-mentioned problems is provided with one end pivotally supported by a piston reciprocating in a cylinder of the internal combustion engine, and A connecting rod whose end is pivotally supported by a crankshaft, and a bearing hole of the connecting rod at one end or the other end of the connecting rod, and a support shaft inserted through the bearing hole. A variable compression ratio device for an internal combustion engine, comprising: an eccentric sleeve that is eccentrically arranged between the bearing hole and the support shaft to switch between the high compression ratio position and the low compression ratio position. A stopper pin for positioning the eccentric sleeve at the high compression ratio position and the low compression ratio position by abutting; and a stopper pin for engaging the eccentric sleeve in the axial direction of the eccentric sleeve. And an eccentric sleeve locking means comprising a lock pin movably provided between the eccentric sleeve and a position not engaged with the eccentric sleeve, and a lock pin for fixing the rotation thereof when engaged with the eccentric sleeve. When the sleeve is at the high compression ratio position, a first abutment against the stopper pin is provided.
A first engaging portion is provided for engaging the contact portion and the lock pin. When the eccentric sleeve is at the low compression ratio position, a second contact portion that contacts the stopper pin and the lock pin are provided. A second engaging portion capable of engaging is provided.

<Operation> In the variable compression ratio device for an internal combustion engine of the present invention described above, when the eccentric sleeve rotates, the first contact portion contacts the stopper pin and the first engagement portion engages with the lock pin. The eccentric sleeve is fixed at the high compression ratio position while the second contact portion contacts the stopper pin and the second engagement portion engages with the lock pin, and the eccentric sleeve is fixed at the low compression ratio position. You.

<Embodiment> Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. 1 to 6 show a variable compression ratio device for an internal combustion engine according to a first embodiment of the present invention. FIG. 1 shows a connecting rod showing a state in a low compression ratio state. FIG. 3 shows a connecting rod showing a state in a high compression ratio state, FIG. 3 shows an overall configuration of a variable compression ratio apparatus showing a state in a low compression ratio state, and FIG. 4 shows a state of a low compression ratio state or a high compression ratio state. FIG. 5 shows an eccentric sleeve, and FIG. 6 shows a hydraulic circuit thereof.

As shown in FIGS. 1 to 5, the connecting rod 6 has a small end which has a piston pin 7 of a piston 8 which reciprocates in a cylinder of a gasoline engine (internal combustion engine).
And a large end thereof is pivotally supported by a crankpin 2 of a crankshaft 1.

An eccentric sleeve 5 for rotatably eccentrically connecting the bearing hole of the connecting rod 6 and the crankpin 2 as a support shaft passing through the bearing hole is rotatably provided at a pivot at the large end of the connecting rod 6. Have been. That is, the center of the inner circle and the center of the outer circle of the eccentric sleeve 5 are eccentric, and the minimum eccentric position can be taken when the outer periphery of the crankpin 2 is rotated by 180 ° from the maximum eccentric position.

A metal bearing 9 with an inner peripheral surface of the eccentric sleeve 5 is interposed between an inner peripheral surface of the eccentric sleeve 5 and an outer peripheral surface of the crankpin 2, and a connecting rod is connected to the outer peripheral surface of the eccentric sleeve 5. A metal bearing 10 having an inner peripheral surface of the bearing hole of the connecting rod 6 is interposed between the inner peripheral surface of the bearing hole 6 and the inner peripheral surface of the bearing hole 6. Thus, the sliding can be performed between the eccentric sleeve 5 and the crankpin 2 and between the eccentric sleeve 5 and the bearing hole of the connecting rod 6.

An eccentric sleeve locking means 30 is provided. The eccentric sleeve locking means 30 is provided with a lock pin that can move in the same direction as a stopper pin 31 along the axial direction of the eccentric sleeve 5, that is, the axial direction of the crankshaft 1. The stopper pin 31 is brought into contact with the rotating eccentric sleeve 5, and the lock pin 32 is operated by the hydraulic drive mechanism 11A as a piston type fluid pressure drive mechanism. 5 can be fixed at two positions (the above-described maximum eccentric position and minimum eccentric position).

Further, the eccentric sleeve locking means 30 will be described in detail. As shown in FIGS. 1 and 2, the stopper pin 31 is for preventing the rotation of the eccentric sleeve 5 by abutting on the eccentric sleeve 5.
Is embedded along the axial direction of the crankshaft 1 at one end, and one end protrudes outward and is located within the rotation locus of the eccentric sleeve 5.

As shown in FIG. 4, the lock pin 32 is provided with a piston portion 32a in the form of a flange at an intermediate portion thereof and is integrally provided with the piston portion 32a. The lock pin 32 with the piston portion 32a is provided at the large end of the connecting rod 6. Are fitted in the through holes formed in the holes. This through-hole penetrates the large end of the connecting rod in the axial direction of the crankshaft, and is configured as a three-step hole having three diameters. The small-diameter hole located at one end is the diameter of the lock pin 32. The middle diameter hole located at the intermediate portion is almost the same as the diameter of the piston portion 32a, and the large diameter hole located at the other end is set larger than the piston portion 32a.

Therefore, the lock pin 3 with the piston portion 32a is inserted into this through hole.
When 2 is inserted, the lock pin 32 is inserted through the small-diameter hole of the through hole in a liquid-tight manner, and the piston
32a is inserted in a liquid-tight manner. And return spring 1
5 and a cap with a through hole with the same diameter as the large diameter part of the through hole and a central hole with the same diameter as the lock pin 32
When the cap 16 is fixed to the connecting rod 6 with a bolt or the like, the lock pin 32 is inserted in a liquid-tight manner into the small diameter portion of the through hole at one end, and the other end is inserted into the through hole of the cap 16. The middle diameter portion of the through hole is divided into two chambers 13 and 14 by the piston portion 32a. The hydraulic passages 17 and 18 are connected to the chambers 13 and 14, respectively. Thus, these two chambers are configured as hydraulic chambers (liquid pressure chambers) 13, 14 formed on both sides of the piston portion 32a. The return spring 15 is loaded in the hydraulic chamber 13 to urge the lock pin 32 with the piston 32a toward the hydraulic chamber 14. The pressure receiving areas on both sides of the piston portion 32a are set equal.

As a result, the piston portion 32 attached to the lock pin 32
a, a piston-type hydraulic drive mechanism 11A capable of driving the lock pin 32 by moving the piston portion 32a connected to the lock pin 32 by the hydraulic chambers 13, 14, the return spring 15, the cap 16, and the like.

The stopper pin 31 and the lock pin 32 are installed with a phase of 180 °.

The eccentric sleeve 5 has a flange portion axially separated so as to sandwich the large end portion of the connecting rod 6, as shown in FIGS. 1, 2 and 5. A notch-shaped engaging portion 5a as a second engaging portion is formed in a portion of the flange portion facing the lock pin 32 where the eccentric sleeve 5 takes the minimum eccentric position, and the other flange portion has In the portion facing the lock pin 32 where the eccentric sleeve 5 takes the maximum eccentric position,
A notch-shaped engaging portion 5b as a first engaging portion is formed. In addition, at the portion of one flange portion of the eccentric sleeve 5 facing the stopper pin 31 where the eccentric sleeve 5 takes the minimum eccentric position, the above-described engaging portion 5b as a second contact portion is located. A notch-shaped engaging portion 5c as a first contact portion is formed in a portion of the other flange portion facing the stopper pin 31 where the eccentric sleeve 5 takes the maximum eccentric position.

Accordingly, when the lock pin 32 is moved rightward from the state shown in FIG. 1 to the first position as shown by the two-dot chain line in FIG. 4, the eccentric sleeve 5 is moved as shown in FIG. The lock pin 32 engages with the engaging portion 5b after the stopper pin 31 engages with the engaging portion 5c by rotating counterclockwise, and the eccentric sleeve 5 is fixed to the large end of the connecting rod 6 at the maximum eccentric position. Is done. On the other hand, when the lock pin 32 moves to the left from the state shown in FIG. 2 to the second position as shown in FIG.
As shown in the figure, after the eccentric sleeve 5 rotates clockwise and the stopper pin 31 engages with the engaging portion 5b, the engaging portion 5a engages, and the eccentric sleeve 5 is moved to the minimum eccentric position. It is designed to be fixed to the large end.

When the eccentric sleeve 5 is fixed to the large end of the connecting rod 6 at the maximum eccentric position, the connecting rod 6 becomes apparently the most extended state, and a high compression ratio state can be realized. When the connecting rod 6 is fixed to the large end of the connecting rod 6 at the minimum eccentric position, the connecting rod 6 is apparently contracted to achieve a low compression ratio state. Note that the compression ratio in this low compression ratio state is selected to a value that does not cause knocking of the engine, which is almost the same as the value set in a normal engine.
Therefore, the compression ratio in the high compression ratio state is set to a value higher than the value set in a normal engine.

Further, means for applying a required oil pressure (standard oil pressure) to the oil pressure chambers 13 and 14 through oil pressure passages 17 and 18 in advance, and a lock pin 32 with a piston portion 32a which is pressed against the urging force of the return spring 15 Means for applying a hydraulic pressure (standard hydraulic pressure + α) higher than the standard hydraulic pressure to the hydraulic chamber 14 is provided to move the hydraulic chamber 14 to the chamber 13 side.

In other words, as shown in FIG.
From the crank journal 3 of the crankshaft 1 through the portion of the crank arm 4 and from the crankpin 2 further through the metal bearing 9, the eccentric sleeve 5, the metal bearing 10 and the large end of the connecting rod 6, the hydraulic chambers 13, 14 are respectively provided.
Is connected to the

Since the sliding between the metal bearing 9 and the crankpin 2 and the sliding between the metal bearing 10 and the eccentric sleeve 5, the inner peripheral surfaces of the metal bearings 9 and 10 make one round of the inner peripheral surface, and the hydraulic pressure is respectively increased. Two endless grooves connected to the passages 17 and 18 are formed, and each groove formed in the metal bearing 9 is provided with an eccentric sleeve 5.
The hydraulic passages 17 and 18 formed in the large end of the co-working rod 6 are formed in the respective grooves formed in the metal bearing 10 while the through holes are formed in alignment with the hydraulic passages 17 and 18 formed in the metal bearing 10. A through-hole matching the part 18 is formed.

As shown in FIG. 6, the portion of the hydraulic passage 17 outside the crankshaft is connected to the main gallery 23 side, and the portion of the hydraulic passage 18 outside the crankshaft is connected to the sub oil pump 24 or the main gallery 23 side. I have.
That is, the oil (lubricating oil) from the oil tank or the oil pan 20 is supplied to the oil pump with the relief valve 21.
The main gallery 23 is provided with an oil filter 22 as an oil having a required hydraulic pressure (a hydraulic pressure for supplying a standard hydraulic pressure).
The standard gallery oil is supplied from the main gallery 23 through the hydraulic passage 17. Further, the oil from the main gallery 23 is supplied to the sub oil pump 24 and discharged as a higher oil pressure (standard oil pressure + α). The oil pressure from the sub oil pump 24 The hydraulic pressure from the main gallery 23 is supplied to the hydraulic passage 18 selectively. That is, when the switching valve 25 is set to the position a as shown in FIG. 6, the standard hydraulic pressure from the main gallery 23 is supplied to the hydraulic passage 18, and the switching valve 25
To the position b, the sub-oil pump 24
High hydraulic pressure (standard hydraulic pressure + α) is supplied.

Accordingly, when the switching valve 25 is set to the position b, a high oil pressure (standard oil pressure + α) is supplied from the sub oil pump 24 to the oil pressure passage 18, and this high oil pressure is supplied to the oil pressure chamber 14. At this time, since the standard hydraulic pressure from the main gallery 23 is supplied into the hydraulic chamber 13 through the hydraulic passage 17, the lock pin 32 with the piston portion 32 a is pressed against the urging force of the return spring 15, as shown in FIG. When moved to the right as shown by the two-dot chain line to take the first position, as shown in FIG. 2, the stopper pin 31, the engaging portion 5c, the lock pin 32
Is engaged with the engaging portion 5b, so that the eccentric sleeve 5 is fixed to the large end of the connecting rod 6 at the maximum eccentric position. As a result, the connecting rod 6 appears to be the most extended state, and a high compression ratio state can be realized.

When the switching valve 25 is set to the a position, the standard hydraulic pressure from the main gallery 23 is supplied to the hydraulic passage 18, and the standard hydraulic pressure is also supplied to the hydraulic chamber 14. At this time, since the standard hydraulic pressure from the main gallery 23 is supplied into the hydraulic chamber 13 via the hydraulic passage 17, the lock pin 3 with the piston portion 32 a is
2 moves to the left as shown by the solid line in FIG.
When the position is taken, as shown in FIG.
And the engaging portion 5b, the lock pin 32 and the engaging portion 5a are engaged, and the eccentric sleeve 5 is connected to the connecting rod 6 at the minimum eccentric position.
Is fixed to the large end of the. As a result, the connecting rod 6 is apparently contracted most, and a low compression ratio state can be realized.

The oil pump 19 and the sub oil pump 24 are both driven by an engine.

Reference numeral 26 in FIG. 6 denotes a relief valve for adjusting the pressure difference α between (standard oil pressure + α) and the standard oil pressure to be constant.

Further, 27 is an oil control valve for switching control of the switching valve 25. When the oil control valve 27 is set to the a position, the pilot oil pressure of the switching valve 25 is reduced, and the switching valve 25 can be set to the a position. When the oil control valve 27 is set to the position b, the pilot oil pressure of the switching valve 25 is increased, and the switching valve 25 can be set to the position b.

A switching control signal from a controller 40 is input to the oil control valve 27. The controller 40 receives a detection signal from an engine load sensor 41 or an engine speed sensor 42, When an engine high load range or engine high speed range that is larger than the medium load range is detected, the oil control valve
When a control signal is issued to set 27 to the a position and an area below the engine middle load is detected, the oil control valve
A control signal for setting 27 to the b position is issued.

According to the above-described configuration, when a region equal to or lower than the engine middle load is detected, a control signal is output to set the oil control valve 27 to the position b. Is supplied to the hydraulic chamber 14 with the high hydraulic pressure (standard hydraulic pressure + α). At this time, a hydraulic passage is
Since the standard oil pressure is supplied from the main gallery 23 via the high oil pressure (standard oil pressure +
α) and the standard oil pressure are applied to the piston 32a,
As a result, the differential pressure α moves the lock pin 32 with the piston portion 32a to the right as shown by a two-dot chain line in FIG. 4 against the urging force of the return spring 15. As a result, the lock pin 32 takes the first position, and as shown in FIG.
The eccentric sleeve 5 is fixed to the large end of the connecting rod 6 at the maximum eccentric position by engaging the stopper pin 31 with the engaging portion 5c and the lock pin 32 with the engaging portion 5b. As a result, the connecting rod 6 appears to be in the most extended state, and is in the high compression ratio state. With such a high compression ratio state, thermal efficiency is improved, and improvement in fuel efficiency and the like can be expected.

Further, when an engine high load region or an engine high rotation region that is larger than the engine middle load region is detected, a control signal is output to set the oil control valve 27 to the a position. The standard hydraulic pressure from the main gallery 23 is supplied to the passages 17 and 18, and the standard hydraulic pressure is supplied to the hydraulic chambers 13 and 14.
Thereby, by the repulsive force of the return spring 15,
When the lock pin 32 with the piston portion 32a moves to the left as shown by the solid line in FIG. 6 and assumes the second position, as shown in FIG. 1, the stopper pin 31 and the engagement portion 5b, Lock pin
The eccentric sleeve 5 is fixed to the large end of the connecting rod 6 at the minimum eccentric position by engaging the engagement portion 32 with the engaging portion 5a.
As a result, the connecting rod 6 is apparently contracted most, and is in a low compression ratio state. Knocking can be reliably avoided by setting the compression ratio to the low compression state.

As described above, in the first embodiment, since the control hydraulic pressure of the standard hydraulic pressure is applied to both the hydraulic chambers 13 and 14 as a base, the pressure difference between the two hydraulic chambers is changed due to the change in the engine speed and the crank angle. As a result, the operation of the lock pin 32 does not become uncertain due to the centrifugal force, the acceleration of the reciprocating motion of the connecting rod 6, and the like.

Further, since the lock pin 32 is configured to be movable in the axial direction of the crankshaft 1, it is possible to reliably operate the lock pin 32 even under the influence of inertia generated due to the reciprocating motion of the connecting rod. Can be.

Further, when the lock pin 32 takes the first position, the eccentric sleeve 5 can be fixed to the large end of the connecting rod 6 at the maximum eccentric position, and the lock pin 32 moves in the opposite direction to the second position. When the position is taken, the eccentric sleeve 5
Can be fixed to the large end of the connecting rod 6 at the minimum eccentric position, so that there is no need to consider the drive timing of the lock pin 32, thereby simplifying the control for changing the compression ratio. On the other hand, in the device disclosed in Japanese Patent Publication No. 63-32972, it is necessary to detect the piston position and control the lock pin protrusion timing, which complicates the control.

FIG. 7 shows an eccentric sleeve of a variable compression ratio device for an internal combustion engine according to a second embodiment of the present invention.

In the first embodiment described above, each of the engaging portions 5a, 5b, 5c of the eccentric sleeve 5 is formed by providing a notch in the outer peripheral portion. However, in the eccentric sleeve 51 of the present embodiment, a long portion is used instead of the notch. A hole is formed. As a result, each of the engaging portions 51a (second engaging portion), 51b (first engaging portion, second contact portion), and 51c (first contact portion) of the eccentric sleeve 51 are formed, so that the eccentric sleeve 51 is eccentric. The durability of the sleeve 51 is improved. Further, a concave portion having the same shape may be formed in place of the long hole, whereby the durability of the eccentric sleeve 51 is further improved.

FIG. 8 shows an eccentric sleeve of a variable compression ratio device for an internal combustion engine according to a third embodiment of the present invention.

In each of the above-described embodiments, the rotation area of the eccentric sleeve 5 is set to 180 °.
Is set to about 120 °. Therefore, the eccentric sleeve 61 is provided with a notch 62 for regulating the rotation angle over about 120 °, and the engaging portion 61 with which the stopper pin engages.
The engagement portions 61a (second engagement portion) and 61d (first engagement portion) with which the lock pin engages are formed with b (second contact portion) and 61c (first contact portion). . Thus, the rotation region of the eccentric sleeve is not limited.

<Effects of the Invention> As described above in detail with the embodiments, according to the variable compression ratio device for an internal combustion engine of the present invention, the variable compression ratio device is positioned at the high compression ratio position and the low compression ratio position by contacting the eccentric sleeve. An eccentric sleeve locking means comprising a stopper pin and a lock pin movably provided at a position engaging with the eccentric sleeve and a position not engaging with the eccentric sleeve and fixing the rotation thereof when engaged with the eccentric sleeve; In addition, when the eccentric sleeve is at the high compression ratio position, the first abutting portion abutting on the stopper pin and the first engageable portion of the lock pin can be engaged.
When the eccentric sleeve is at the low compression ratio position and the second contact portion that contacts the stopper pin and the second engaging portion that can engage with the lock pin are provided, the eccentric sleeve is provided with the stopper. After the rotation of the lock pin is restricted by the movement of the lock pin after the rotation of the lock pin is stopped after the contact with the pin and the rotation of the lock pin in one direction is stopped, the impact force acting on the lock pin when the eccentric sleeve is stopped is reduced. As a result, the locking and unlocking operation of the eccentric sleeve is ensured.
As a result, the reliability and durability of the locking operation of the eccentric sleeve can be improved.

[Brief description of the drawings]

1 is a front view of a connecting rod showing a state in a low compression ratio state, FIG. 2 is a front view of a connecting rod showing a state in a high compression ratio state, and FIG. 3 is a low compression ratio state. FIG. 4 is an overall configuration diagram of a variable compression ratio device showing a state in a state, FIG. 4 is a hydraulic drive mechanism diagram showing a state in a low compression ratio state or a high compression ratio state, and FIG. 5 is a perspective view of an eccentric sleeve. Fig. 6 is a hydraulic circuit diagram, Fig. 7
FIG. 8 is a perspective view of an eccentric sleeve of a variable compression ratio apparatus for an internal combustion engine according to a second embodiment of the present invention, and FIG. 8 is a perspective view of an eccentric sleeve of an internal combustion engine according to a third embodiment of the present invention. In the drawing, 1 is a crankshaft, 2 is a crankpin, 5 is an eccentric sleeve, 5a, 5b, 5c is an engagement portion, 6 is a connecting rod, 11A is a piston type hydraulic drive mechanism, 30 is an eccentric sleeve lock means, and 31 is an eccentric sleeve lock means. A stopper pin, 32 is a lock pin, 32a is a piston portion, 51 and 61 are eccentric sleeves, and 51a, 51b, 51c, 61a, 61b, 61c and 61d are engagement portions.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinzo Tatsumi 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (56) References JP-A-58-38343 (JP, A) 2-19620 (JP, A) JP-A 62-69041 (JP, U) JP-A 64-21233 (JP, U) JP-B 63-32972 (JP, B2) (58) Int.Cl. ⁶ , DB name) F02D 15/02 F16C 7/06

Claims (1)

(57) [Claims] 1. A connecting rod having one end pivotally supported by a piston reciprocating in a cylinder of an internal combustion engine and the other end pivotally supported by a crankshaft, and a connecting rod having one end or the other end of the connecting rod. One of the bearings is rotatably interposed between a bearing hole of the connecting rod and a spindle inserted through the bearing hole, and the bearing hole and the spindle are eccentric to each other so that a high compression ratio position and a low compression ratio are set. A variable compression ratio device for an internal combustion engine having an eccentric sleeve that switches to any one of the positions, wherein the stopper pin positions the eccentric sleeve at the high compression ratio position and the low compression ratio position by contacting the eccentric sleeve; In the axial direction of the eccentric sleeve, the eccentric sleeve is movably provided between a position engaging with the eccentric sleeve and a position not engaging with the eccentric sleeve. An eccentric sleeve lock means comprising a lock pin for fixing the rotation of the eccentric sleeve when the eccentric sleeve is in the high compression ratio position. A first engagement portion is provided for engaging the contact portion and the lock pin. When the eccentric sleeve is at the low compression ratio position, a second contact portion that contacts the stopper pin and the lock pin are engaged. A variable compression ratio device for an internal combustion engine, comprising a second engaging portion that can be engaged.