Chain tensioner mechanism

Abstract

To provide a chain tensioner mechanism which can inhibit entry of air bubbles into a pressure chamber and inhibit deterioration of tension of a timing chain of an engine.SOLUTION: A chain tensioner mechanism includes: a hydraulic chain tensioner 8 which applies tensile force to a chain wound around a crank shaft of an engine; and a branch oil passage 28 which is branched from an oil passage 26 for supplying oil for lubrication or cooling to the engine to supply the oil to the chain tensioner 8. The chain tensioner 8 applies tensile force to the chain with the oil supplied from a hydraulic power source which generates a hydraulic oil pressure by operation of the engine. In the oil passage 26, a valve 29 which selectively opens or closes the oil passage 26 is provided at the downstream side of a spot branched into the branch oil passage 28. The valve 29 is closed when the engine is stopped.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a chain tensioner mechanism that applies tension to a chain such as an engine timing chain. [Background technology]

[0002] Patent Document 1 discloses a hydraulic chain tensioner device that aims to suppress the generation of abnormal noise between the lever that presses the chain due to the vibration of the chain when the engine is started in a chain tensioner equipped with a plunger for pressing the chain. The chain tensioner device of Patent Document 1 includes a tensioner body that extends vertically up and down, a cylinder chamber that is formed in the tensioner body and is closed at the top and open at the bottom, and a bottomed cylindrical plunger for pressing the chain that contacts the inner surface of the cylinder chamber to form a pressure chamber with the cylinder chamber and can move up and down. Patent Document 1 also discloses that an oil gallery is formed in the cylinder block to supply oil to each part of the engine from a hydraulic pump operated by the engine, and that oil is supplied to the pressure chamber through the oil gallery. An oil sump is formed between the oil gallery and the pressure chamber to store the oil supplied from the oil gallery.

[0003] Specifically, the oil sump in Patent Document 1 is provided vertically above the pressure chamber, and the upper part of the oil sump communicates with an oil gallery. The lower part of the oil sump communicates with a pressure oil supply passage formed in the tensioner body, and oil is supplied from the pressure oil supply passage to the pressure chamber via an oil supply passage provided in the cylinder chamber. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-159819 A Summary of the Invention [Problem to be solved by the invention]

[0005] As in the device described in Patent Document 1, by providing an oil reservoir between the chain tensioner device and the oil passage, oil is supplied from the oil reservoir to the pressure chamber according to the amount of oil discharged from the pressure chamber. Therefore, even if the hydraulic pump stops when the engine is stopped, the decrease in oil pressure in the pressure chamber can be suppressed. For example, when a vehicle runs with the engine stopped, particularly when the vehicle runs in an EV mode in which the engine is stopped and the vehicle runs only on the motor, such as a hybrid vehicle, a torque in the direction of rotating the engine in the reverse direction is generated by inertia force or the like. As a result, the force with which the chain pushes the plunger toward the pressure chamber changes, and the plunger may reciprocate. Even if the oil in the pressure chamber is discharged by such reciprocating motion of the plunger, an amount of oil according to the amount of the discharged oil can be supplied from the oil reservoir to the pressure chamber. Therefore, when the stopped engine is started, the generation of abnormal noise caused by the chain vibrating and contacting the head cover, and deterioration of the engine exhaust and fuel efficiency can be suppressed.

[0006] However, if the EV mode continues for a long time, the amount of oil remaining in the oil sump decreases, and air may enter the oil sump space from the oil passage. If air enters the oil sump, the air may turn into bubbles due to vibrations of the vehicle, and may enter the pressure chamber from the oil sump. If the engine is started in such a state, the hydraulic pressure in the pressure chamber may be insufficient, resulting in insufficient pressure on the chain. As a result, a relatively large vibration or pulsation may occur in the chain, which may cause abnormal noise due to the chain coming into contact with the head cover.

[0007] The present invention has been made in consideration of the above-mentioned technical problems, and aims to provide a chain tensioner mechanism that can prevent air bubbles from entering the pressure chamber and prevent a decrease in the tension of the engine's timing chain, even when the hydraulic pump is stopped. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the present invention provides a chain tensioner mechanism comprising a hydraulic chain tensioner that applies tension to a chain wound around the crankshaft of an engine which, together with a motor, constitutes a driving force source, and a branch oil passage that branches off from an oil passage that supplies oil for lubrication or cooling to the engine and supplies oil to the chain tensioner, wherein the chain tensioner applies tension to the chain with oil supplied from a hydraulic source that generates hydraulic pressure when the engine is operating, and wherein the oil passage is provided with a valve downstream of the point where it branches off to the branch oil passage, and the valve is closed when the engine is stopped. Effect of the Invention

[0009] In the chain tensioner mechanism according to the present invention, a branch oil passage is provided that branches off from an oil passage that supplies oil to the engine and supplies oil to the chain tensioner. A valve that closes the oil passage when the engine is stopped is provided downstream of the branch oil passage in the oil passage. Therefore, for example, when the engine is stopped and the vehicle is running only with the output of the motor, the oil passage is blocked by the valve, so that oil is prevented from flowing downstream of the valve in the oil passage. In other words, oil is retained in the oil passage upstream of the valve, including the branch oil passage from the hydraulic source. That is, since the oil passage upstream of the valve essentially functions as a reservoir, even if oil is discharged from the chain tensioner in a state where there is no oil supply from the hydraulic source, oil is supplied from the oil passage and the branch oil passage, so that it is possible to prevent a shortage of hydraulic pressure in the chain tensioner when the engine is started. In other words, since the chain tensioner can be quickly operated, it is possible to prevent the generation of noise caused by vibration and pulsation of the chain when the engine is started. In addition, because the oil passage is closed, it is possible to prevent air from entering the portion where the oil is stored, compared to a state in which the oil is stored only in a storage chamber formed by branching off from the oil passage. In other words, it is possible to prevent air from entering the chain tensioner. Furthermore, because there is no need to provide a space to store oil, it is possible to improve the degree of freedom in design. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an example of a chain drive mechanism to which the chain tensioner mechanism of the present invention is applied. [Diagram 2] FIG. 2 is a cross-sectional view showing an example of a tensioner. [Diagram 3] FIG. 2 is a schematic cross-sectional view for explaining the configuration of an oil passage in the chain tensioner mechanism of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is merely one example of the case where the present invention is implemented, and is not intended to limit the present invention.

[0012] A chain drive mechanism that opens and closes the valves in the engine is shown diagrammatically in Figure 1. The engine described here constitutes the driving force source for a hybrid vehicle, and therefore the hybrid vehicle has a motor (or motor-generator: not shown) as a driving force source in addition to the engine. The hybrid vehicle can be set to an engine mode in which it runs on engine torque, an EV mode in which it runs on motor torque, and an HV mode in which it runs on both engine and motor torque. In the EV mode, the engine is stopped to improve fuel efficiency (energy efficiency).

[0013] The chain drive mechanism shown in Fig. 1 is a mechanism for opening and closing exhaust valves and intake valves (not shown) in accordance with the rotation angle (crank angle) of crankshaft 1. A drive sprocket 2 rotated by crankshaft 1 is provided, as well as a first driven sprocket 3 for the exhaust valves and a second driven sprocket 4 for the intake valves. A timing chain (hereinafter sometimes simply referred to as chain) 5 is wound around these sprockets 2, 3, and 4. A roller chain made of cylindrical rollers connected by side links is used as chain 5, but other chains may also be used.

[0014] A chain tensioner slipper (hereinafter simply referred to as slipper) 6 is provided between the driving sprocket 2 and the first driven sprocket 3. The slipper 6 is intended to apply tension to the chain 5 by pressing a portion of the chain 5, which is generally circular, toward its inner circumference (in a direction intersecting the running direction). That is, as shown in FIG. 1, the slipper 6 is a guide piece that is curved in an arch shape so as to protrude toward the inner circumference of the chain 5, and has a guide groove into which the chain 5 fits. The slipper 6 is rotatably attached to the engine by a pin 7 at the lower portion in FIG. 1.

[0015] A chain tensioner (hereinafter, sometimes simply referred to as tensioner) 8 that presses the slipper 6 toward the chain 5 is disposed on the back side (opposite side to the chain 5) of the slipper 6. An example of the tensioner 8 is shown in a cross-sectional view in FIG. 2. The tensioner 8 is configured such that a plunger 11 is inserted axially movably into a cylinder portion 10 that is integrated with a flange portion 9 for fixing the tensioner 8, and the plunger 11 is protruded by hydraulic pressure supplied to the inside of the cylinder portion 10 to press the slipper 6. More specifically, the cylinder portion 10 is a cylindrical member with a bottom that opens toward the slipper 6, and the plunger 11 is an axial member inserted into the cylinder portion 10 so as to slide in almost intimate contact with the inner circumferential surface of the cylinder portion 10.

[0016] The space formed on the bottom side of the cylinder portion 10 by inserting the plunger 11 is the high-pressure oil chamber 12, which accommodates a spring 13. This spring 13 is a compression spring, and applies an elastic force to the plunger 11 in a direction pushing it out of the cylinder portion 10. Meanwhile, a low-pressure oil chamber 14 is formed inside the plunger 11. This low-pressure oil chamber 14 opens to the side of the high-pressure oil chamber 12, and a check valve 15 is provided at the opening.

[0017] This check valve 15 is a valve mechanism that allows hydraulic pressure to flow from the low-pressure oil chamber 14 toward the high-pressure oil chamber 12 and blocks hydraulic pressure to flow in the opposite direction. One example is the ball valve shown in Fig. 2, which has a structure in which a sphere 16 is disposed at the open end of the low-pressure oil chamber 14 facing the high-pressure oil chamber 12, and the sphere 16 is pressed against the open end of the low-pressure oil chamber 14 by a spring 18 held by a retainer 17. Therefore, when the hydraulic pressure of the high-pressure oil chamber 12 is higher than that of the low-pressure oil chamber 14, the check valve 15 remains closed, but conversely, when the hydraulic pressure of the high-pressure oil chamber 12 becomes lower than that of the low-pressure oil chamber 14 and the pressure difference exceeds the elastic force of the spring 18, the sphere 16 is pressed back in the direction of compressing the spring 18, opening the open end of the low-pressure oil chamber 14.

[0018] An intake and exhaust hole 19 that connects the low pressure oil chamber 14 to the outer circumferential surface of the plunger 11 is formed in the middle of the plunger 11 in the axial direction. This intake and exhaust hole 19 moves in the same manner as the plunger 11 when the plunger 11 moves in the axial direction due to a change in the tension of the chain 5. A header section 20, which is a small space, is provided between the outer circumferential surface of the plunger 11 and the inner circumferential surface of the cylinder section 10 so as to cover the range of movement of the intake and exhaust hole 19. This header section 20 is a section where the inner diameter of the cylinder section 10 is partially enlarged, or where the outer diameter of the plunger 11 is partially reduced. A supply hole 21 that connects to this header section 20 is formed in the cylinder section 10.

[0019] A hydraulic source 23 is connected to the supply hole 21 via a pipe 22. The hydraulic source 23 is for supplying hydraulic pressure to the tensioner 8, and is mainly composed of a hydraulic pump that is connected to the crankshaft 1 and driven by the engine. This hydraulic source 23 is, for example, a variable displacement pump that is used as the hydraulic pump, and is a mechanical oil pump that is configured so that the discharge pressure can be adjusted according to the operating state of the engine.

[0020] As shown in Figure 1, a fixed guide 24 is provided between the drive sprocket 2 and the second driven sprocket 4, which guides the chain 5 by curving it inward to increase the winding angle around the drive sprocket 2 and the second driven sprocket 4. The fixed guide 24 is a guide piece curved in an arch shape in the opposite direction to the slipper 6, and has a guide groove into which the chain 5 is inserted and guided. The fixed guide 24 is fixed to a predetermined location on the engine.

[0021] A head cover 25 is disposed above the chain 5 wound around each of the driven sprockets 3, 4 so as to cover them. This head cover 25 is made of a thin plate-like member made of metal or synthetic resin that covers the entire engine, and vibrates together with the engine when the engine is running or when the chain 5 is running.

[0022] An oil passage 26 for supplying hydraulic pressure generated from the hydraulic source 23 to the supply hole 21 is shown typically in Fig. 3. As shown in Fig. 3, the oil passage 26 is formed in a cylinder block 27 consisting of a crankcase that houses the cylinders and crankshaft of the engine, and has a branch oil passage 28 that is an oil supply passage for supplying hydraulic pressure to the tensioner side. The branch oil passage 28 is formed to have a smaller cross-sectional area than the oil passage 26, and is configured so that oil supplied from the hydraulic source flows in from the oil passage 26 and is supplied to the pipe 22 that communicates with the opposite side of the oil passage 26.

[0023] An electromagnetic valve 29 is provided downstream of the oil passage 26 by a predetermined distance from the point where the branch oil passage 28 is formed. The electromagnetic valve 29 is configured to open and close when power flows, and may have the same configuration as a conventionally known electromagnetic valve. That is, the plunger is operated when a current flows through a solenoid by an electric signal, and the valve is closed or opened according to the movement. This electromagnetic valve 29 is a so-called normally open type electromagnetic valve 29 in which the valve is maintained in an open state when no power is applied. The predetermined distance may be determined in advance based on experiments, simulations, etc., and may be set based on the amount of oil that remains in the oil passage 26 and the branch oil passage 28 when the electromagnetic valve 29 is closed.

[0024] The electromagnetic valve 29 is configured to open when the engine is operating and to close when the engine is stopped. That is, when the vehicle's driving mode is the engine mode or the HV mode, the electromagnetic valve 29 is not energized and the valve is maintained in an open state. On the other hand, when the vehicle's driving mode is the EV mode, the electromagnetic valve 29 is energized and the valve is maintained in a closed state. Therefore, while the engine is operating, oil is supplied from the hydraulic source 23 to the low-pressure oil chamber 14 of the tensioner 8 via the branch oil passage 28 and the pipe 22.

[0025] Conversely, when the engine is stopped, the supply of oil to the low-pressure oil chamber 14 and various parts of the engine is cut off. On the other hand, with the engine stopped, there is no need to apply tension to the chain 5 by the tensioner 8, and the pressing force acting from the chain 5 to the plunger 11 also becomes smaller. Then, the oil that was being supplied until just before the solenoid valve 29 was closed remains in the oil passage 26, the branch oil passage 28, the low-pressure oil chamber 14, etc. As described above, when the EV mode continues for a long time, the force with which the chain 5 presses the plunger 11 fluctuates depending on the torque input to the crankshaft.

[0026] The plunger 11 presses the chain 5 according to the hydraulic pressure of the high pressure oil chamber 12 and the pressing force of the spring 13. Therefore, when the tension decreases and the pressing force input from the chain 5 to the plunger 11 decreases, the plunger 11 moves toward the chain 5, and oil moves from the low pressure oil chamber 14 to the high pressure oil chamber 12 according to the amount of movement. Conversely, when the tension increases and the pressing force input from the chain 5 to the plunger 11 increases, the pressure in the high pressure oil chamber 12 increases. When the pressing force becomes greater than the hydraulic pressure of the high pressure oil chamber 12 and the pressing force of the spring 13, the oil in the high pressure oil chamber 12 is discharged to the outside through the gap between the cylinder portion 10 and the plunger 11, and the plunger 11 moves toward the spring 13 until the forces are balanced. In this way, when the tension of the chain 5 changes without the supply of hydraulic pressure from the hydraulic source, the plunger 11 reciprocates, and the oil remaining in the low pressure oil chamber 14 and the high pressure oil chamber 12 is gradually discharged.

[0027] In the above-mentioned configuration, in such a case, the solenoid valve 29 is closed, so that the oil remaining in the oil passage 26 and the branch oil passage 28 upstream of the solenoid valve 29 is supplied according to the amount of oil reduced in the low pressure oil chamber 14 and the high pressure oil chamber 12. That is, the branch oil passage 28 and the oil passage 26 essentially function as oil storage chambers, so that the low pressure oil chamber 14 and the high pressure oil chamber 12 can be filled with oil. Therefore, when the engine is started after stopping, the tensioner 8 can be quickly operated, so that the vibration and pulsation of the chain 5 can be suppressed. Therefore, it is possible to prevent or suppress the vibration or sound of the head cover 25 caused by the chain 5 colliding with the head cover 25. In addition, since the oil passage 26 and the branch oil passage 28 can be made to function as storage chambers that essentially store oil by closing the solenoid valve 29, the storage chamber can be omitted. Therefore, there is no need to provide a space for the storage chamber, and the degree of freedom in design can be improved.

[0028] Although the embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned examples, and may be modified as appropriate within the scope of achieving the object of the present invention. For example, a one-way valve (check valve) may be used instead of the electromagnetic valve 29 provided downstream a predetermined distance from the point where the branch oil passage 28 is provided in the oil passage 26. [Explanation of symbols]

[0029] 1 Crankshaft 2 Drive sprocket 3 1st driven sprocket 4 Second driven sprocket 5 Chain 6. Slippers 7-pin 8 Tensioner 9 Flange 10 Cylinder section 11 Plunger 12 High pressure oil chamber 13. Spring 14 Low pressure oil chamber 15 Check valve 16 Sphere 17 Retainer 18 Spring 19 Suction / exhaust hole 20 Header section 21 Supply hole 22 Conduit 23 Hydraulic source 24 Fixed guide 25 Head Cover 26 Oil road 27 Cylinder block 28 Branch oil passage 29 Solenoid valve

Claims

[Claim 1] a hydraulic chain tensioner that applies tension to a chain wound around a crankshaft of an engine that constitutes a driving force source together with the motor; a branch oil passage which branches off from an oil passage for supplying oil for lubrication or cooling to the engine and supplies oil to the chain tensioner, A chain tensioner mechanism configured such that the chain tensioner applies tension to the chain using oil supplied from a hydraulic source that generates hydraulic pressure when the engine is operated, A valve for selectively opening and closing the oil passage is provided downstream of a point where the oil passage branches into the branch oil passage, The valve is closed when the engine is stopped. A chain tensioner mechanism comprising:

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