Cylinder head press-fitting method

Abstract

To provide a cylinder head press-in method capable of tilting, and accurately positioning and holding a holding part and a cylinder head held by the holding part for a long period.SOLUTION: When a press-in device which includes a holding part 4 capable of holding a cylinder head W, a motor 5 capable of tilting the holding part 4 holding the cylinder head W at a prescribed angle θ1(θ2), and receiving members 6, 7 for receiving a press-in force contacting the holding part 4 and operating the cylinder head W when a press-in member P1(P2) is pressed in the cylinder head W is used to press the press-in the member P1(P2) in the cylinder head W, rotary driving of the motor 5 is stopped while the cylinder head W is tilted by the motor 5 at the prescribed angle θ1(θ2), and then presses the press-in member P1(P2) in the cylinder head W.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for press-fitting a cylinder head, and more particularly to a method for press-fitting a press-fit member such as a valve seat or a valve guide into a cylinder head. [Background technology]

[0002] When performing this type of press-fitting, a press-fitting device has conventionally been used that includes a holding section that holds the cylinder head, which is the member to be pressed-fit, 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 regulation section that regulates tilting of the holding section beyond a predetermined angle (see, for example, Patent Document 1).

[0003] 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-regulating portion disposed 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. Thereafter, the corresponding press-fit member is lowered in the vertical direction 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-233813 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the press-fitting device having the above configuration, 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. Therefore, a hydraulic cylinder capable of obtaining a relatively large output and driving 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 therefore 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, which makes it difficult to position the cylinder head at an accurate tilt angle.

[0006] Therefore, instead of using a hydraulic cylinder, a motor could be used to rotate the holder around its longitudinal axis, thereby holding the holder at a predetermined tilt angle. A motor (particularly a servo motor) seems promising as an alternative because it can stop the holder at a predetermined tilt angle without mechanically restricting the tilt of the holder. However, in this type of press-fitting operation, a press-fit member such as a valve seat is press-fitted into the cylinder head with a press-fit force on the order of several tons. Therefore, if a motor is used to rotate the holder and hold it at a predetermined angle, the motor would need to withstand a huge press-fit load, but it is not realistic for a general-purpose motor to withstand a press-fit load on the order of several tons.

[0007] In view of the above circumstances, the technical problem to be solved in this specification is to provide a cylinder head press-fitting method that can tilt the holding portion and the cylinder head held by the holding portion to accurately position and hold them over a long period of time. [Means for solving the problem]

[0008] The above-mentioned problems are solved by a cylinder head press-fitting method according to the present invention, which is characterized in that, when press-fitting the press-fit member into the cylinder head using a press-fitting device including a holding part capable of holding the cylinder head, a motor capable of tilting the holding part while holding the cylinder head to a predetermined angle, and a receiving member that abuts against the holding part and receives the press-fit force acting on the cylinder head when the press-fit member is press-fitted into the cylinder head, the method stops the rotation of the motor while the cylinder head is tilted to the predetermined angle by the motor, and then presses the press-fit member into the cylinder head.

[0009] As described above, 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-fitting 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 rotation of the motor, the load acting on the motor is minimized, and most of the press-fitting force acting on the cylinder head during press-fitting can be borne by the receiving member. Furthermore, since the press-fitting force is borne from a state in which the motor has tilted the cylinder head to a predetermined angle, the retaining portion abuts against the receiving member, allowing the retaining portion and the receiving member to be borne at a very close distance during press-fitting. Therefore, the press-fitting force can be borne essentially as a static load. Therefore, even with continued use, damage to the motor and the receiving member is suppressed, and the cylinder head can be positioned and maintained with high precision over a long period of time. This makes it possible to perform the press-fitting operation on the cylinder head with high precision over a long period of time. In addition, by tilting the holding part with a motor, the holding part can be easily held in a horizontal position, for example, which makes it easier to teach when replacing a cylinder head using a robot arm, and also makes it possible to improve the efficiency of work other than press-fitting. [Effects of the Invention]

[0010] As described above, according to the present invention, the holding portion and the cylinder head held by the holding portion can be positioned and held at a predetermined angle with high precision for a long period of time, thereby making it possible to press-fit the cylinder head with high precision for a long period of time. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a front view of a main portion of a cylinder head press-fitting device according to an embodiment of the present invention. [Figure 2] 2 is a side view of a main part of the cylinder head press-fitting device shown in FIG. 1. FIG. [Figure 3] 2 is a flowchart showing an example of a cylinder head press-fitting method using the press-fitting device shown in FIG. [Figure 4] 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. [Figure 5] 4 is a side view of a main part showing a state in which a holding portion is tilted to a predetermined angle by a motor in the first positioning step S2 of the cylinder head shown in FIG. 3. FIG. [Figure 6] 4 is a side view of a main part showing a state of a holding part when a valve seat is press-fitted in the first press-fitting step S3 of the valve seat shown in FIG. 3. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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.

[0013] 1 is a front view of a main portion 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 includes a press-fit force generating section 2, a punch unit 3 provided with a plurality of 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 of the components will be described in detail below.

[0014] The press-fitting force generating unit 2 includes a plurality of press-fitting rams 22 arranged on a base 21 and a press-fitting force applying device 23 that applies a press-fitting force to the press-fitting rams 22. Here, the press-fitting force applying device 23 is configured to apply a vertical press-fitting force to each of the three press-fitting rams 22 arranged in parallel. Any drive source can be used as the press-fitting force applying device 23, including known drive sources such as hydraulic cylinders and press servo mechanisms. The press-fitting rams 22 and the press-fitting force applying device 23 are both integrally mounted on a support 24 and configured to be movable in the front-to-rear direction (left-to-right direction in FIG. 2 ) by guide rails 25 (LM guides, etc.) mounted on the base 21. Here, a drive device 26 is provided behind the support 24 (on the right side in FIG. 2 ), and the drive device 26 moves the plurality of press-fitting rams 22 and the press-fitting force applying device 23 that are integrally supported on the support 24. Of course, if the press-fitting rams 22 and press-fitting 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 the intake side punch 32 described below, the above-mentioned moving mechanism is not necessary.

[0015] As described above, the punch unit 3 integrally includes a plurality of punches 31, 32, which are configured to slide on a guide rail 34 by, for example, a single-axis servo mechanism 33. Each punch 31, 32 is formed separately from the press-fit ram 22 and is disposed at a position (height) where it can receive force from the press-fit ram 22 to press-fit the press-fit members (valve seats P1, P2) held at its lower end into the cylinder head W. Also, in FIG. 2, for example, an air cylinder 35 disposed between the punches 31, 32 adjacent in the left-right direction can apply a force to the punches 31, 32 that is separate from the press-fit force applied by the press-fit ram 22. Each of the punches 31, 32 is supported by a holder 36 provided in the punch unit 3 so as to be slidable in the vertical direction.

[0016] 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 is also provided with 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. Furthermore, as shown in FIG. 1 , a pair of bearings 43, 43 that can support rotation of the holding portion 4 about the longitudinal axis X1 are provided on both longitudinal ends of the holding portion 4. In this way, the holding portion 4, the plate 41, the pin 42, and the pair of bearings 43, 43 form a rotation holding mechanism for the cylinder head W.

[0017] A motor 5 is disposed on one longitudinal end side of the holding part 4, which can rotate (tilt) the holding part 4 around the longitudinal axis X1 of the holding part 4. The motor 5 is provided with a torque (for example, 10 1Any type of motor can be used as long as it can output a torque (on the order of 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 below on the motor 5, a motor without the brake function (in which the rotating shaft is free to rotate when the power is turned off) may also be used.

[0018] 5 or 6, which will be described later, the tilting angle θ1 (θ2) of the holding portion 4 caused by the motor 5 is set to a magnitude equal to the valve angle of the cylinder head W to be held. In other words, it is preferable to set the tilting 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. Note that the setting of the tilting angle θ1 (θ2) of the holding portion 4 may be performed by controlling the rotational drive of the motor 5 using a control unit 51 electrically connected to the motor 5.

[0019] A protruding portion 44 that protrudes downward is formed on the lower part of the holding portion 4, and a pair of receiving members 6, 7 that can abut against this protruding portion 44 is provided below the holding portion 4. Here, each receiving member 6, 7 has a plurality of receiving portions 61, 71 that protrude in a direction facing the protruding portion 44 (see FIG. 2). These receiving portions 61, 71 are formed, for example, by bolts. As will be described later, the positions of these plurality of receiving portions 61, 71 are adjusted so that the protruding portion 44 abuts against the receiving portions 61 when a press-fit member (here, valve seats P1, P2) is press-fit into the holding portion 4 that is positioned and held at a predetermined angle θ1 (θ2) by the motor 5. 5 and 6, with the holding portion 4 tilted by the motor 5 and positioned and held 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.

[0020] An example of a method for press-fitting a cylinder head using the cylinder head press-fitting device 1 having the above-described configuration will now be described.

[0021] The cylinder head press-fitting method according to this embodiment includes a cylinder head mounting step S1, a cylinder head first positioning step S2, a valve seat first press-fitting step S3, a cylinder head second positioning step S4, and a valve seat second press-fitting step S5, as shown in Fig. 3. Steps S1 to S3 will be mainly described in detail below.

[0022] (S1) Installation process First, the motor 5 is powered on and driven to rotate, thereby tilting the holder 4 and holding 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 the horizontal position, and the brake function of the motor 5 may be used to hold the holder 4 in the horizontal position while the cylinder head W is attached.

[0023] (S2) First positioning process 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 valve seat P1 can be press-fitted by the corresponding punch (here, the exhaust-side punch 31). 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.

[0024] (S3) First press-in process 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 and the press-fitting direction line X2 (see FIG. 1) of the exhaust-side punch 31 that presses in the corresponding valve seat P1 are aligned. 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-fitting force from the press-fitting ram 22, presses in the temporarily held valve seat P1, and fixes it to the cylinder head W.

[0025] Furthermore, due to this press-fitting operation, the holding portion 4 receives a press-fitting force from the exhaust-side punch 31. At this time, because the press-fitting direction line X2 of the exhaust-side punch 31 is offset from the tilting center Ot of the holding portion 4, the holding portion 4 receives torque in a predetermined direction—counterclockwise in the case shown in FIG. 6(a) . As a result, the protrusion 44 formed on the lower part of the holding 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 holding portion 4 from the exhaust-side punch 31 is received by the receiving member 6 (receiving portion 61) that abuts against the protrusion 44. Note that when positioning the cylinder head W using a motor 5 with a braking function, the press-fitting operation described above 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 that rotates due to inertia after the power is turned off. Therefore, even if 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 can be minimized and most of the press-fitting force can be received by the receiving member 6 (receiving portion 61).

[0026] (S4) Second positioning process Next, as shown in FIG. 5(b), the motor 5 is driven to rotate in the opposite direction from 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.

[0027] (S5) Second press-in process 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 in the cylinder head W is introduced. At this time, the valve seat P2 is temporarily held in place at the press-fit position. 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-fitting force from the press-fitting ram 22, presses in the temporarily held valve seat P2, and fixes it to the cylinder head W.

[0028] Furthermore, due to this press-fitting operation, the holding portion 4 receives a press-fitting force from the intake-side punch 32. At this time, because the press-fitting direction line X3 of the intake-side punch 32 is offset from the tilting center Ot of the holding portion 4, the holding portion 4 receives torque in a predetermined direction, that is, clockwise in the case shown in FIG. 6(b). As a result, the protrusion 44 formed on the lower part of the holding portion 4 abuts against the receiving portion 71 of the receiving member 7 that faces it across a predetermined distance d2. Therefore, most of the press-fitting force that the holding portion 4 receives from the intake-side punch 32 is received by the other receiving member 7 (receiving portion 71) that abuts 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.

[0029] 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-fitting force) acting on the cylinder head W during press-fitting is borne by the receiving member 6 (7) provided separately from the motor 5. According to this method, the motor 5 can 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, and most of the press-fitting force acting on the cylinder head W during press-fitting can be borne by the receiving member 6 (7). Furthermore, since the press-fitting force is borne from a state in which the motor 5 has tilted the cylinder head W to the predetermined angle θ1 or θ2, the holding portion 4 abuts against the receiving member 6 (7). Therefore, the holding portion 4 and the receiving member 6 (7) can be borne at a very close distance during press-fitting. Therefore, the press-fitting force can be borne substantially as a static load. Therefore, even after continuous use, damage to the motor 5 and the receiving members 6 (7) can be suppressed, and the cylinder head W can be accurately positioned and maintained for a long period of time. Therefore, it becomes possible to perform press-fitting work on the cylinder head W with high precision over a long period of time. In addition, by tilting the holding part 4 with the motor 5, it is possible to easily hold the holding part 4 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.

[0030] While one embodiment of the cylinder head press-fitting method according to the present invention has been described above, the present invention is not limited to this embodiment and can, of course, take any specific form within the scope of the invention.

[0031] For example, in the above embodiment, the motor 5 is connected to the holder 4 capable of holding the cylinder head W, and the holder 4 is tilted by the rotational drive of the motor 5, thereby tilting the cylinder head W held by the holder 4 as a unit. However, this is not limiting. For example, although not shown, a connecting shaft may be attached to the cylinder head W, and the rotating shaft of the motor 5 may be connected to this connecting shaft. After the cylinder head W with the connecting shaft attached is attached to the holder 4, the cylinder head W may be tilted by the rotational drive of the motor 5.

[0032] In the above embodiment, the case has been exemplified where 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 comprised of a plurality of bolts, during press-fitting, thereby receiving the press-fit force at each receiving portion 61, 71, but this is of course not limited to this. In other words, it is desirable to set the shape of the receiving portions 61, 71 constituting the receiving members 6, 7 appropriately depending on the abutment mode including the abutment position with the retaining portion 4.

[0033] Furthermore, for example, in the above embodiment, the case where the valve seats P1, P2 are press-fitted into the cylinder head W has been described, but the present invention is not limited to this particular part. It goes without saying that the cylinder head press-fitting method according to the present invention can be applied to any press-fit member that is press-fitted into the cylinder head, such as a valve guide. [Explanation of symbols]

[0034] 1 Cylinder head press-fitting device 2 Press-fit force generating section 3 punch unit 4 Holding part 5 motors 6,7 Receiving member 21 Mounting stand 22 Press-fit ram 23 Press-fitting device 26 Drive unit 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 Foundation d1, d2 Opposite distance Ot Tilt center (holding part) P1, P2 valve seats W cylinder head X1 Longitudinal axis X2 Press-fit direction line X3 Press-fit direction line θ1, θ2 Tilt angle

Claims

[Claim 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 state in which the tilting center of the holding portion is 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.

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