Valve timing control device

Abstract

To provide a valve timing control device which can release the lock of a vane rotor.SOLUTION: A valve timing control device comprises: a housing having a hole; a vane rotor accommodated in the housing, and rotatable in the housing by hydraulic pressure; a lock pin provided at the vane rotor, opposing the hole, and movable by the hydraulic pressure; and a control part for controlling the hydraulic pressure by controlling an opening of a valve. A position of the vane rotor is locked by the engagement of the lock pin with the hole, the lock is released by the separation of the lock pin from the hole, and the control part controls a rising speed of a duty of the valve on the basis of a rotation number of an internal combustion engine.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a valve timing control device. [Background technology]

[0002] 2. Description of the Related Art A variable valve timing mechanism (VVT) that controls the valve timing of an internal combustion engine is known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-234716 A Summary of the Invention [Problem to be solved by the invention]

[0004] In VVT, the valve timing is changed by changing the position of the vane rotor using hydraulic pressure. The position of the vane rotor can be locked by engaging a lock pin with a hole. The lock can be released by pushing the lock pin out using hydraulic pressure. However, the lock pin may get caught between parts while engaged, making it difficult to release the lock. Therefore, the objective of this invention is to provide a valve timing control device that can unlock the vane rotor. [Means for solving the problem]

[0005] The above object can be achieved by a valve timing control device comprising a housing having a hole, a vane rotor accommodated in the housing and rotatable within the housing by hydraulic pressure, a lock pin provided on the vane rotor, facing the hole and movable by the hydraulic pressure, and a control unit that controls the hydraulic pressure by controlling a valve opening, wherein the position of the vane rotor is locked when the lock pin engages with the hole, and the lock is released when the lock pin disengages from the hole, and the control unit controls the rate at which the duty of the valve is increased based on the rotation speed of an internal combustion engine. Effect of the Invention

[0006] It is possible to provide a valve timing control device capable of unlocking the vane rotor. [Brief description of the drawings]

[0007] [Figure 1] 1(a) and 1(b) are diagrams illustrating a valve timing control device according to an embodiment. [Diagram 2] 2(a) and 2(b) are enlarged cross-sectional views of the lock pin. [Diagram 3] Fig. 3(a) is a diagram illustrating an example of torque, Fig. 3(b) is a diagram illustrating an example of an increase speed of the duty, and Fig. 3(c) is a diagram illustrating a phase change speed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the valve timing control device of the present embodiment will be described with reference to the drawings. However, in the drawings, the dimensions and ratios of each part may not be illustrated to be completely consistent with the actual ones. Also, in some drawings, some details may be omitted.

[0009] 1(a) and 1(b) are diagrams illustrating a valve timing control device 100 according to an embodiment. The valve timing control device 100 has an ECU (Electronic Control Unit, control section) 10, an oil pump 12, an oil control valve (OCV) 14, a cam housing 20, a vane rotor 22, oil passages 16, 30 and 32, and a lock pin 40. In Fig. 1(a) and 1(b), the oil passage 16 is indicated by a solid line, the oil passage 30 is indicated by a dashed line, and the oil passage 32 is indicated by a dotted line.

[0010] A sprocket 21 is provided on the outer peripheral surface of the cam housing 20, and a cavity is provided inside the cam housing 20. A vane rotor 22 is housed inside the cam housing 20. The vane rotor 22 has a plurality of vanes 23. The number of vanes 23 is, for example, three. The vanes 23 protrude outward from the vane rotor 22. The cam housing 20 and the vane rotor 22 can rotate around the same rotation axis. The Z axis represents the thickness direction of the cam housing 20 and the vane rotor 22, and is parallel to the rotation axis.

[0011] The valve timing is controlled by the position of the vane rotor 22. The position of the vane rotor 22 is controlled by hydraulic pressure. Hydraulic chambers 24 and 26 are formed inside the cam housing 20. Hydraulic chamber 24 is located on one side of each of the three vanes 23, and hydraulic chamber 26 is located on the other side. Hydraulic pressure is generated in hydraulic chamber 24 and hydraulic chamber 26. When vane 23 receives the hydraulic pressure of hydraulic chamber 24 and the hydraulic pressure of hydraulic chamber 26, vane rotor 22 rotates. The X1 direction in the figure is the direction of left rotation. The X2 direction is the direction of right rotation.

[0012] The oil pump 12, the OCV 14, and the oil passages form a hydraulic circuit. The oil pump 12 and the OCV 14 control the hydraulic pressure. One end of the oil passage 16 is connected to the oil pump 12, and the other end is connected to the OCV 14. The oil passages 30 and 32 are connected to the OCV 14. The oil passage 30 is connected to the three hydraulic chambers 24. The oil passage 32 is connected to the three hydraulic chambers 26.

[0013] The oil pump 12 pumps hydraulic oil (oil) from an oil pan (not shown). The oil flows through an oil passage 16 and is supplied to the OCV 14. The ECU 10 controls the oil pressure by sending a signal to the OCV 14 and changing the opening of the OCV 14. Depending on the duty of the signal, the OCV 14 switches the passage through which the oil is supplied. For example, switching between the oil passage 30 and the oil passage 32 is performed using a certain value of the duty as a threshold value.

[0014] When the OCV 14 selects the oil passage 30, the oil flows through the oil passage 30 and is supplied to the hydraulic chamber 24. The increase in the hydraulic pressure in the hydraulic chamber 24 causes the vane rotor 22 to rotate leftward (X1 direction). When the OCV 14 selects the oil passage 32, the oil flows through the oil passage 32 and is supplied to the hydraulic chamber 26. The increase in the hydraulic pressure in the hydraulic chamber 26 causes the vane rotor 22 to rotate rightward (X2 direction).

[0015] 2(a) and 2(b) are enlarged cross-sectional views of the lock pin 40. One vane 23 of the vane rotor 22 has a through hole. The through hole penetrates the vane 23 in the Z-axis direction. The lock pin 40 is provided in the through hole of the vane 23 and is arranged parallel to the Z-axis direction. The lock pin 40 is movable in the Z-axis direction. The lock pin 40 faces the hole 25 of the cam housing 20. A spring 42 is provided on the side of the lock pin 40 opposite the hole 25.

[0016] The oil passage 44 communicates with the hydraulic chamber 24 and the hole 25. When oil is supplied into the oil passage 44, hydraulic pressure is applied to the tip of the lock pin 40. The position of the lock pin 40 is determined by the biasing force of the spring 42 and the hydraulic pressure.

[0017] In Fig. 2(a), the biasing force of spring 42 is greater than the oil pressure in oil passage 44. Lock pin 40 is biased downward in the figure and inserted into hole 25. When lock pin 40 engages with hole 25, vane rotor 22 cannot rotate. The position of vane rotor 22 is locked.

[0018] 2(b), the hydraulic pressure is greater than the biasing force of the spring 42. The lock pin 40 is biased upward in the figure, and is released from engagement with the hole 25. The vane rotor 22 is able to rotate.

[0019] A lateral force acting on the lock pin 40 may cause the lock pin 40 to be pressed against the cam housing 20. For example, in the state shown in FIG. 2(a), a force in the X1 direction presses the X1 side surface of the lock pin 40 against the inner wall of the hole 25 of the cam housing 20. The lock pin 40 is sandwiched between the cam housing 20 and the vane rotor 22, making it difficult for the lock pin 40 to be removed. In other words, it is difficult to release the lock on the vane rotor 22.

[0020] In response to the rotation of cam housing 20, torque acts on vane rotor 22 and lock pin 40. Torque F1 acts in the X1 direction. Torque F2 acts in the X2 direction. When torque F2 acts in the X2 direction, lock pin 40 moves away from the inner wall of hole 25, making it easier to remove.

[0021] FIG. 3(a) is a diagram illustrating torque. The horizontal axis represents time, and the vertical axis represents torque. Torque values ​​higher than 0 (positive values) are torque in the X1 direction. Values ​​lower than 0 (negative values) are torque in the X2 direction. As shown in FIG. 3(a), the torque acting on the vane 23 changes periodically in response to the rotation of the cam housing 20. When torque in the X2 direction (negative torque) is applied to the vane 23, the lock pin 40 moves away from the cam housing 20 and is not pressed against it. This makes it easy for the lock pin 40 to come out.

[0022] The higher the engine speed, the higher the rotation speed of the cam housing 20, and the higher the frequency of the torque fluctuations shown in FIG. 3(a). In other words, the number of times the torque faces the X2 direction increases. This makes it easier for the lock pin 40 to come out. On the other hand, the lower the engine speed, the lower the rotation speed of the cam housing 20, and the lower the frequency of the torque fluctuations. The number of times the torque faces the X2 direction decreases. In this embodiment, the lock pin 40 is made easier to come out even when the rotation speed is low.

[0023] FIG. 3(b) is a diagram illustrating the duty increase speed. The horizontal axis represents the engine speed. The vertical axis represents the duty increase speed. The ECU 10 sets the duty increase speed as shown in FIG. 3(b) according to the engine speed. The higher the engine speed, the faster the duty increase speed. The faster the duty increase speed, the quicker the switching between the oil passage 30 and the oil passage 32. The lower the engine speed, the slower the duty increase speed. The slower the duty increase speed, the slower the switching. For example, when the engine speed is R1, the duty increase speed is D1. When the engine speed is R2, which is higher than R1, the duty increase speed is D2, which is higher than D1.

[0024] FIG. 3(c) is a diagram showing the phase change speed. The horizontal axis shows the duty of OCV 14 (OCV-duty). The vertical axis shows the VVT ​​phase change speed. The phase change speed changes according to the duty of OCV 14. A value higher than 0 is the phase change speed to the advance side. Vane 23 receives hydraulic pressure that moves it to the advance side. A value lower than 0 is the phase change speed to the retard side. Vane 23 receives hydraulic pressure that moves it to the retard side. The area where the phase change speed is near 0 is the dead zone. In the dead zone, the hydraulic pressure in hydraulic chamber 24 and the hydraulic pressure in hydraulic chamber 26 are about the same magnitude and are close to being balanced. This makes it difficult for vane 23 to rotate.

[0025] The dashed line in Fig. 3(c) is an example where the duty increase speed is D1. The solid line is an example where the duty increase speed is D2. Compared to the dashed line example, in the solid line example, the phase change speed changes slower and the time passing through the dead zone is longer. Since the vane 23 is difficult to rotate for a long time, the lock pin 40 is not pressed down either. The lock pin 40 becomes easier to come out.

[0026] According to this embodiment, the vane rotor 22 is provided with a lock pin 40. The vane rotor 22 is locked by the lock pin 40 engaging with the hole 25. The lock is released by the lock pin 40 being disengaged from the hole 25. The ECU 10 controls the increasing speed of the duty of the OCV 14 based on the rotation speed of the internal combustion engine. As shown in FIG. 3(b), the lower the rotation speed, the slower the increasing speed of the duty. As shown in FIG. 3(a), the slower the increasing speed of the duty, the longer the time it takes to pass through the dead zone. The lock pin 40 is not pressed against the cam housing 20, so it is easy to remove. It is possible to unlock the vane rotor 22.

[0027] As shown in FIG. 3(a), the torque changes periodically. When torque acts in the X2 direction, the lock pin 40 is more likely to come off. The higher the engine speed, the more times the torque turns to the X2 direction. Therefore, the lock pin 40 is more likely to come off. On the other hand, the lower the engine speed, the less times the torque turns to the X2 direction. According to the embodiment, when the speed is low, the duty increase speed is reduced and the time passing through the dead zone is lengthened. The lock pin 40 is more likely to come off. In other words, the lock pin 40 is more likely to come off regardless of the engine speed, so that the vane 23 can be unlocked.

[0028] 3B, the ECU 10 changes the increasing speed of the duty in a linear manner with respect to the rotation speed. The ECU 10 may change the increasing speed of the duty in a non-linear manner with respect to the rotation speed.

[0029] Although a preferred embodiment of the present invention has been described in detail above, the present invention is not limited to such a specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0030] 10 ECU, 12 oil pump, 14 OCV, 16, 30, 32, 44 oil passage, 20 cam housing, 21 sprocket, 22 vane rotor, 23 vane, 24, 26 hydraulic chamber, 25 hole, 40 lock pin, 42 spring, 100 valve timing control device

Claims

[Claim 1] a housing having a hole; a vane rotor accommodated in the housing and rotatable within the housing by hydraulic pressure; a lock pin provided in the vane rotor, facing the hole, and movable by the hydraulic pressure; A control unit that controls the hydraulic pressure by controlling an opening degree of a valve, The lock pin engages with the hole to lock the position of the vane rotor, When the lock pin is removed from the hole, the lock is released. The control unit controls the rate at which the duty of the valve increases based on the rotation speed of the internal combustion engine.

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