JP7747432B2 - Cylinder head press-fitting method - Google Patents

Description

The present invention relates to a cylinder head press-fitting method, and more particularly to a method for press-fitting press-fit components such as valve seats and valve guides into a cylinder head.

When performing this type of press-fitting, a press-fitting device has traditionally been used that includes a holding section that holds the cylinder head (the part to be pressed in) and is configured to be tiltable around its longitudinal axis, a cylinder section for tilting the holding section while holding the cylinder head, and a tilt restriction section that restricts tilting of the holding section beyond a predetermined angle (see, for example, Patent Document 1).

The operation of press-fitting a press-fit member (valve seat or valve guide) into a cylinder head using the press-fitting device configured as described above is performed, for example, as follows: First, the cylinder head is attached to the holding portion, and then the cylinder portion is driven to tilt the holding portion. At this time, the holding portion abuts against a tilt restriction portion located in a predetermined position, thereby holding the holding portion in a tilted state at a predetermined angle, and the posture of the cylinder head held by this holding portion is set to the predetermined angle. The corresponding press-fit member is then lowered vertically and press-fitted into the corresponding press-fit portion (press-fit hole) of the cylinder head, thereby press-fitting the press-fit member into the cylinder head.

Japanese Patent Application Laid-Open No. 2009-233813

With a press-fitting device configured as described above, the tilt angle of the holding part is set by the holding part abutting against the tilt restriction part, so the cylinder part does not require high positioning accuracy. For this reason, a hydraulic cylinder, which can generate relatively high output and drive speed, is used for the cylinder part. However, when positioning the holding part as described above, the holding part is tilted at high speed by the hydraulic cylinder and collides with the tilt restriction part each time a positioning operation is performed, and wear of the tilt restriction part becomes a problem with continued use of the press-fitting device. Wear of the tilt restriction part changes the position at which tilt of the holding part is restricted, making it difficult to position the cylinder head at an accurate tilt angle.

One possible solution is to use a motor, instead of a hydraulic cylinder, to rotate the holding part around its longitudinal axis, thereby holding the holding part at a predetermined tilt angle. A motor (particularly a servo motor) seems like a promising alternative, as it can stop the holding part at a predetermined tilt angle without mechanically restricting the tilt of the holding part. However, in this type of press-fitting operation, press-fit members such as valve seats are pressed into the cylinder head with a press-fit force on the order of several tons. Therefore, if a motor is used to rotate the holding part and hold it at a predetermined angle, the motor would need to withstand a huge press-fit load, and it is not realistic for a general-purpose motor to withstand a press-fit load on the order of several tons.

In light of the above, the technical problem to be solved in this specification is to provide a cylinder head press-fitting method that can tilt the retaining portion and the cylinder head held by the retaining portion to accurately position and hold them over a long period of time.

The above-mentioned problems are solved by the cylinder head press-fitting method of the present invention. Specifically, this press-fitting method uses a press-fitting device equipped with a holding portion capable of holding the cylinder head, a motor capable of tilting the holding portion to a predetermined angle while holding the cylinder head, and a receiving member that abuts against the holding portion and receives the press-fit force acting on the cylinder head when the press-fitting member is press-fitted into the cylinder head. When press-fitting the press-fitting member into the cylinder head, the motor's rotational drive is stopped while the cylinder head is tilted to a predetermined angle by the motor, and then the press-fitting member is press-fitted into the cylinder head.

In this way, in the cylinder head press-fitting method according to the present invention, the tilt angle of the cylinder head is set by the motor, while the load (press-in force) acting on the cylinder head during press-fitting is borne by a receiving member provided separately from the motor. This method allows the motor to accurately position the cylinder head at a predetermined angle. Meanwhile, by performing the press-fitting operation after stopping the motor's rotation, the load on the motor is minimized, allowing the receiving member to bear most of the press-in force acting on the cylinder head during press-fitting. Furthermore, since the press-in force is received from a state tilted to a predetermined angle by the motor, the retaining portion abuts against the receiving member, allowing the retaining portion and receiving member to be received at a very close distance during press-fitting. Therefore, the press-in force can be received essentially as a static load. Therefore, even with continued use, damage to the motor and receiving member is suppressed, and the cylinder head can be positioned and maintained with precision over an extended period of time. This makes it possible to perform press-fitting of the cylinder head with high precision over an extended period of time. Furthermore, by tilting the holding part with a motor, the holding part can be easily held in a horizontal position, which makes it easier to teach when replacing cylinder heads using a robot arm, for example, and can also improve the efficiency of tasks other than press-fitting.

As described above, according to the present invention, the holding portion and the cylinder head held by the holding portion can be accurately positioned and held at a predetermined angle for a long period of time, thereby enabling press-fitting into the cylinder head to be performed with high accuracy for a long period of time.

1 is a front view of a main portion of a cylinder head press-fitting device according to an embodiment of the present invention; FIG. 2 is a side view of a main part of the cylinder head press-fitting device shown in FIG. 1 . 2 is a flowchart showing an example of a cylinder head press-fitting method using the press-fitting device shown in FIG. 1 . 4 is a side view of a main part showing a state in which the cylinder head is attached to the holding part with the holding part in a horizontal position in the cylinder head attachment step S1 shown in FIG. 3. FIG. 4 is a side view of a main part showing a state in which the holding portion is tilted to a predetermined angle by the motor in the first positioning step S2 of the cylinder head shown in FIG. 3. FIG. 4 is a side view of a main part showing a state of a holding portion when a valve seat is press-fitted in the first press-fitting step S3 of the valve seat shown in FIG. 3. FIG.

A cylinder head press-fitting method according to one embodiment of the present invention will be described below with reference to the drawings. In this embodiment, the case of press-fitting a valve seat into a cylinder head will be described as an example.

Figure 1 is a front view of the main components of a cylinder head press-fitting device 1 according to the present invention. As shown in the figure, this cylinder head press-fitting device 1 comprises a press-fit force generating section 2, a punch unit 3 equipped with multiple punches 31, 32 for press-fitting valve seats P1, P2, which serve as press-fit members, into a cylinder head W, a holding section 4 that holds the cylinder head W and is configured to be tiltable about its longitudinal axis, a motor 5, and receiving members 6, 7. Each component will be described in detail below.

The press-fit force generating unit 2 includes multiple press-fit rams 22 mounted on a base 21 and a press-fit force applying device 23 that applies a press-fit force to the press-fit rams 22. Here, the press-fit force applying device 23 is configured to apply a vertical press-fit force to each of the three press-fit rams 22 arranged in parallel. Any drive source can be used as the press-fit force applying device 23, including known drive sources such as hydraulic cylinders and press servo mechanisms. Both the press-fit rams 22 and the press-fit force applying device 23 are integrally mounted on a support 24 and configured to be movable in the front-to-rear direction (left-to-right direction in Figure 2) by guide rails 25 (LM guides, etc.) mounted on the base 21. Here, a drive device 26 is mounted behind the support 24 (right side in Figure 2), and this drive device 26 moves the multiple press-fit rams 22 and the press-fit force applying device 23 that are integrally supported on the support 24. Of course, if the press-fit rams 22 and press-fit force applying devices 23 are arranged in two rows of three, for example, in accordance with the arrangement of the exhaust-side punch 31 and intake-side punch 32 described below, the movement mechanism is not necessary.

As described above, the punch unit 3 integrally comprises multiple punches 31, 32, which can slide on guide rails 34 using, for example, a single-axis servo mechanism 33. Each punch 31, 32 is formed separately from the press-fit ram 22 and is positioned (height) so that it can receive force from the press-fit ram 22 to press-fit the press-fit member (valve seats P1, P2) held at its lower end into the cylinder head W. Furthermore, in Figure 2, for example, an air cylinder 35 disposed between adjacent punches 31, 32 in the left-right direction can apply a force to the punches 31, 32 separate from the press-fit force applied by the press-fit ram 22. Each punch 31, 32 is supported by a holder 36 provided in the punch unit 3 so that it can slide vertically.

The holding portion 4 is provided with a plate 41 for clamping the cylinder head W placed on its upper surface. The holding portion 4 also has one or more pins 42 that can be inserted into the cylinder head W to position it. Therefore, by attaching the plate 41 with the cylinder head W inserted onto the positioning pins 42, the cylinder head W is positioned and held relative to the holding portion 4. Also, as shown in FIG. 1, a pair of bearings 43, 43 are provided at both longitudinal ends of the holding portion 4 to support rotation of the holding portion 4 about the longitudinal axis X1. In this way, the holding portion 4, plate 41, pin 42, and pair of bearings 43, 43 form a rotational holding mechanism for the cylinder head W.

A motor 5 capable of rotating (tilting) the holding portion 4 about the longitudinal axis X1 of the holding portion 4 is disposed at one longitudinal end of the holding portion 4. Any type of motor can be used as the motor 5 as long as it can tilt the holding portion 4 while holding the cylinder head W, in other words, as long as it can output a torque sufficient to tilt the holding portion 4 (e.g., on the order of ¹⁰¹ Nm or more). For example, from the viewpoint of positional accuracy, a servo motor is preferable. Similarly, from the viewpoint of positional accuracy, a motor having a brake function that mechanically brakes the rotating shaft when the power is turned off may be used. Of course, from the viewpoint of minimizing the effect of the press-fit load (described later) on the motor 5, a motor without the brake function (i.e., a motor whose rotating shaft is free to rotate when the power is turned off) may also be used.

As shown in Figures 5 and 6 (described below), the tilt angle θ1 (θ2) of the holding portion 4 driven by the motor 5 is set to a value equal to the valve angle of the cylinder head W being held. In other words, it is advisable to set the tilt angle θ1 (θ2) according to the type of cylinder head W to be press-fitted or the type of valve seats P1, P2 to be press-fitted. The tilt angle θ1 (θ2) of the holding portion 4 may also be set by controlling the rotation of the motor 5 using a control unit 51 electrically connected to the motor 5.

A downwardly projecting protrusion 44 is formed on the lower part of the retaining portion 4, and a pair of receiving members 6, 7 that can abut against this protrusion 44 are provided below the retaining portion 4. Each receiving member 6, 7 has multiple receiving portions 61, 71 that protrude in a direction opposite the protrusion 44 (see Figure 2). These receiving portions 61, 71 are formed, for example, by bolts. As described below, the positions of these multiple receiving portions 61, 71 are adjusted so that the protrusion 44 abuts against the receiving portions 61 when a press-fit member (here, valve seats P1, P2) is press-fit into the retaining portion 4, which is positioned and held at a predetermined angle θ1 (θ2) by the motor 5. Specifically, as shown in Figures 5 and 6, when the motor 5 tilts the holder 4 and positions and holds it at a predetermined angle θ1, the mounting positions of the receiving portions 61, 71 relative to the bases 62, 72 are adjusted so that slight gaps d1, d2 are formed between the protrusion 44 and the receiving portions 61, 71. As an example, the mounting positions of the receiving portions 61, 71 relative to the bases 62, 72 are adjusted so that the opposing distances d1, d2 are, for example, 0.005 mm or more and 0.1 mm or less, preferably 0.01 mm or more and 0.05 mm or less.

Below, an example of a cylinder head press-fitting method using the cylinder head press-fitting device 1 having the above configuration will be described.

As shown in Figure 3, the cylinder head press-fitting method according to this embodiment includes a cylinder head mounting step S1, a first cylinder head positioning step S2, a first valve seat press-fitting step S3, a second cylinder head positioning step S4, and a second valve seat press-fitting step S5. Below, steps S1 to S3 will be described in detail.

(S1) Mounting Step First, the motor 5 is powered on and rotated to tilt the holder 4 and hold it in a horizontal position (see FIG. 4). Thereafter, the cylinder head W to be press-fitted is carried from outside the press-fitting device 1 to a predetermined position on the holder 4 by a robot arm (not shown), and the cylinder head W is fixed to the holder 4 by a plate 41 and clamp pins 42, 42. If the motor 5 has a brake function, the motor 5 may be powered off once the holder 4 is in a horizontal position, and the brake function of the motor 5 may be used to hold the holder 4 in a horizontal position while the cylinder head W is being mounted.

(S2) First Positioning Step After the cylinder head W is attached to the holder 4 as described above, the cylinder head W is positioned. Specifically, as shown in FIG. 5( a), by rotating the motor 5 while the power to the motor 5 remains on, the holder 4 is rotated about the longitudinal axis X1 (see FIG. 1) passing through the tilting center Ot, and the cylinder head W is tilted to an angle θ1 at which the corresponding punch (here, the exhaust-side punch 31) can press-fit the valve seat P1. Of course, if the power to the motor 5 was turned off during attachment of the cylinder head W using the brake function of the motor 5, the above-described positioning of the cylinder head W is performed after the power to the motor 5 is turned on. At this time, the press-fitting ram 22 is moved to approximately the same alignment line of the exhaust-side punches 31 of the punch unit 3 so that a press-fitting force can be applied to the exhaust-side punches 31. When the cylinder head W is positioned, the protrusion 44 of the holding portion 4 and one of the receiving members 6 are in a non-contact state; specifically, each receiving portion 61 and the protrusion 44 are slightly spaced apart so that the opposing distance d1 between one of the receiving members 6 and the protrusion 44 is within the above-mentioned range.

(S3) First Press-Fitting Step After positioning the cylinder head W as described above, the exhaust-side punch 31, which already holds the corresponding valve seat P1 at its tip, is placed at a predetermined position above the cylinder head W. In this state, the axis Xe (see FIG. 1) of the exhaust valve of the cylinder head W coincides with the press-fitting direction line X2 (see FIG. 1) of the exhaust-side punch 31 that presses in the corresponding valve seat P1. Therefore, by driving the air cylinder 35 from this position, all of the exhaust-side punches 31 (three exhaust-side punches 31 in this embodiment) are lowered, and the corresponding valve seat P1 is introduced into the press-fit position within the cylinder head W. At this time, the valve seat P1 is positioned at the press-fit position and temporarily held in place. Then, from this state, the press-fitting force applying device 23 is driven to press the press-fitting ram 22, which is located above the exhaust-side punch 31, downward. As a result, as shown in FIG. 6( a ), the exhaust-side punch 31 receives a press-in force from the press-in ram 22 , and the valve seat P 1 in a provisionally held state is press-fitted and fixed to the cylinder head W.

This press-fitting operation also causes the retaining portion 4 to receive a press-fit force from the exhaust-side punch 31. Because the press-fit direction line X2 of the exhaust-side punch 31 is offset from the tilting center Ot of the retaining portion 4, the retaining portion 4 receives torque in a predetermined direction—counterclockwise in the case shown in Figure 6(a). As a result, the protrusion 44 formed on the lower part of the retaining portion 4 abuts against the receiving portion 61 of the receiving member 6, which faces the protrusion 44 at a predetermined distance d1. Therefore, most of the press-fitting force received by the retaining portion 4 from the exhaust-side punch 31 is received by the receiving member 6 (receiving portion 61) that abuts the protrusion 44. Note that when positioning the cylinder head W using a motor 5 with a braking function, the above-described press-fitting operation may be performed with the power to the motor 5 turned off. Typically, this type of brake only provides a braking force sufficient to brake the rotating shaft, which continues to rotate due to inertia after the power is turned off. Therefore, even when the rotating shaft of the motor 5 is fixed by the brake after the power is turned off, the load on the motor 5 side is minimized, and most of the press-fitting force can be borne by the receiving member 6 (receiving portion 61).

(S4) Second Positioning Step Next, as shown in FIG. 5(b), the motor 5 is driven to rotate in the opposite direction to that in the first positioning step S2, thereby rotating the holder 4 about the longitudinal axis X1 (see FIG. 1) passing through the tilting center Ot and tilting the cylinder head W to an angle at which the corresponding punch (here, the intake-side punch 32) can press-fit the valve seat P2. At this time, the press-fitting ram 22 is moved to approximately the same alignment line of the intake-side punches 32 of the punch unit 3 so that a press-fit force can be applied to the intake-side punch 32. With the cylinder head W positioned, the protrusion 44 of the holder 4 and the receiving members 6 and 7 are not in contact with each other. Specifically, the receiving portions 71 and the protrusions 44 are adjusted to be slightly spaced apart so that the opposing distance d2 between the other receiving member 7 and the protrusions 44 is a predetermined value.

(S5) Second Press-Fitting Step After positioning the cylinder head W as described above, the intake-side punch 32, which already holds the corresponding valve seat P2 at its tip, is placed at a predetermined position above the cylinder head W. In this state, the axis Xi (see FIG. 1) of the exhaust valve of the cylinder head W is aligned with the press-fitting direction line X3 (see FIG. 1) of the intake-side punch 32 that presses in the corresponding valve seat P2. Therefore, by driving the air cylinder 35 from this position to lower all of the intake-side punches 32, the valve seat P2 corresponding to the press-fit position within the cylinder head W is introduced. At this time, the valve seat P2 is positioned at the press-fit position and temporarily held in place. Then, from this state, the press-fitting force applying device 23 is driven to press the press-fitting ram 22, which is located above the intake-side punch 32, downward. As a result, as shown in FIG. 6(b), the intake-side punch 32 receives a press-fit force from the press-fitting ram 22, presses in the temporarily held valve seat P2, and fixes it to the cylinder head W.

Furthermore, due to this press-fitting operation, the retaining portion 4 receives a press-fit force from the intake-side punch 32. At this time, because the press-fit direction line X3 of the intake-side punch 32 is offset from the tilting center Ot of the retaining portion 4, the retaining portion 4 receives torque in a predetermined direction, i.e., clockwise in the case shown in Figure 6(b). As a result, the protrusion 44 formed on the lower part of the retaining portion 4 abuts against the receiving portion 71 of the opposing receiving member 7 across a predetermined distance d2. Therefore, most of the press-fit force that the retaining portion 4 receives from the intake-side punch 32 is received by the other receiving member 7 (receiving portion 71) abutting against the protrusion 44. Note that in this case as well, after positioning the cylinder head W using the motor 5, the above-described press-fitting operation may be performed with the power to the motor 5 turned off.

As described above, in the cylinder head press-fitting method according to this embodiment, the tilt angle of the cylinder head W is set by the motor 5, while the load (press-in force) acting on the cylinder head W during press-fitting is borne by a receiving member 6 (7) provided separately from the motor 5. This method allows the motor 5 to accurately position the cylinder head W at the predetermined angle θ1 (θ2). Meanwhile, by performing the press-fitting operation after stopping the rotation of the motor 5, the load acting on the motor 5 is minimized, allowing the receiving member 6 (7) to bear most of the press-in force acting on the cylinder head W during press-fitting. Furthermore, since the retaining portion 4 abuts against the receiving member 6 (7) when the press-in force is applied from a state tilted to the predetermined angles θ1 and θ2 by the motor 5, the retaining portion 4 and the receiving member 6 (7) can be received at a very close distance during press-fitting. Therefore, the press-in force can be borne essentially as a static load. Therefore, even after continuous use, damage to the motor 5 and the receiving members 6 and 7 is suppressed, and the cylinder head W can be accurately positioned and maintained for an extended period of time. This makes it possible to perform press-fitting work on the cylinder head W with high precision over a long period of time. Furthermore, by tilting the holding part 4 with the motor 5, the holding part 4 can be easily held in a horizontal position, for example, which makes it easier to teach when replacing the cylinder head W using a robot arm, and also makes it possible to improve the efficiency of work other than press-fitting work.

The above describes one embodiment of the cylinder head press-fitting method according to the present invention, but the present invention is not limited to this embodiment and can, of course, take any specific form within the scope of the invention.

For example, in the above embodiment, a motor 5 is connected to a holder 4 capable of holding a cylinder head W, and the holder 4 is tilted by rotating the motor 5, thereby tilting the cylinder head W held by the holder 4 as a unit. However, this is not necessarily limited to this. For example, although not shown in the figures, a connecting shaft may be attached to the cylinder head W, the rotating shaft of the motor 5 may be connected to this connecting shaft, and the cylinder head W with the connecting shaft attached may be attached to the holder 4, and then the cylinder head W may be tilted by rotating the motor 5.

In addition, in the above embodiment, the example was given of a case in which the protruding portion 44 protruding downward from the retaining portion 4 abuts against the receiving portions 61, 71, which are arranged below the retaining portion 4 and comprise multiple bolts, during press-fitting, thereby receiving the press-fit force at each receiving portion 61, 71. However, this is not necessarily limited to this. In other words, it is desirable to appropriately set the shape of the receiving portions 61, 71 that constitute the receiving members 6, 7 depending on the abutment mode, including the abutment position with the retaining portion 4.

In addition, for example, in the above embodiment, the case where valve seats P1, P2 are press-fitted into the cylinder head W has been described, but this is not a particular component. Naturally, the cylinder head press-fitting method of the present invention can be applied to any press-fit member that is press-fitted into the cylinder head, such as a valve guide.

REFERENCE SIGNS LIST 1 Cylinder head press-fitting device 2 Press-fit force generating section 3 Punch unit 4 Holding section 5 Motor 6, 7 Receiving member 21 Frame 22 Press-fitting ram 23 Press-fit force applying device 26 Drive device 31 Exhaust side punch 32 Intake side punch 35 Air cylinder 41 Plate 42 Pins 43, 43 Bearing section 44 Protrusion 51 Control section 61, 71 Receiving member 62, 72 Base d1, d2 Opposing distance Ot Tilt center (holding section)
P1, P2 Valve seat W Cylinder head X1 Longitudinal axis X2 Press-fit direction line X3 Press-fit direction lines θ1, θ2 Tilt angle

Claims (1)

a motor that can rotate the holding portion while holding the cylinder head to a first angle at which the first press-fit member can be press-fitted and a second angle at which the second press-fit member can be press-fitted by rotating the holding portion around its axis; and first and second receiving members that abut against the holding portion and receive the press-fit force acting on the cylinder head when the first and second press-fit members are press-fitted into the cylinder head,
a tilting center of the holding portion being disposed at a midpoint between a press-fitting direction line of the first press-fitting member and a press-fitting direction line of the second press-fitting member which are parallel to each other;
the cylinder head is tilted to the first angle by the motor to provide a first opposing gap between the holding portion and the first receiving member, and the rotational driving of the motor is stopped in this state; thereafter, a press-fitting force is applied, causing the holding portion to come into contact with the first receiving member, thereby press-fitting the first press-fit member into the cylinder head; and
a cylinder head press-fitting method in which, with the tilting center of the holding portion fixed, the cylinder head is tilted to the second angle by the motor to provide a second opposing distance between the holding portion and the second receiving member, and the rotational drive of the motor is stopped in a state where a press-fit force is then applied, causing the holding portion to abut against the second receiving member and press- fitting the second press-fit member into the cylinder head.