JP2011012589A - Valve timing adjusting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure/improve operation speed and stability in retention control by a device itself, in a valve timing adjusting device including an assist spring.SOLUTION: Since the number of advancing side oil pressure chambers effectively acting as working oil pressure chambers is kept smaller than the number of retarding side oil pressure chambers, and torque of an assist spring 27 biasing a rotor 4 to an advancing direction is set larger than the maximum value of cam average torque in a low rotation region, the drop of operation speed in a retarding direction by an advancing side assist spring installation is prevented and advancing side operation speed is improved by reducing oil quantity consumed at the time of advancing side operation.

Description

  The present invention relates to a valve timing adjusting device which is attached to an exhaust side camshaft of an internal combustion engine and controls the opening / closing timing of an exhaust valve by hydraulic pressure.

  Various valve timing adjusting devices for internal combustion engines for automobiles have been devised so far. Especially when applying to the exhaust side, the cam torque acting on the retard side differs from the reference position (most advanced angle position) at the start of the device, so an assist spring for urging the rotor in the advance direction is installed, Various torque settings have been devised. Patent document 1 is one of them.

JP-A-10-068306

  However, according to the technique described in Patent Document 1, the biasing torque of the assist spring is set to be larger than the maximum torque at the start. If such a large torque is applied in one direction, during normal operation, the valve timing adjusting device acts as a load when operating by hydraulic pressure, and the operability is significantly reduced, which adversely affects the performance of the internal combustion engine. Can be considered.

  The present invention has been made to solve the above-described problems, and provides a valve timing adjusting device that has an assist spring and ensures and improves the operation speed and stability in holding control by the device itself. Objective.

  The valve timing adjusting device according to the present invention provides an assist for energizing the rotor in the advance direction by setting the advance side hydraulic chamber number to n / 2 with respect to the retard angle side hydraulic chamber number n effectively acting as a working hydraulic chamber. The spring torque is set larger than the maximum value of the cam average torque in the low rotation range.

  According to the present invention, the load resistance due to the residual pressure in the advance hydraulic chamber during the retard operation is reduced by reducing the advance hydraulic chamber number n / 2 to the retard hydraulic chamber number n. can do. As a result, it is possible to prevent a decrease in the operation speed in the retard direction due to the installation of the advance side assist spring, and it is possible to improve the advance side operation speed by reducing the amount of oil consumed during the advance side operation. Also, by setting the assist spring torque larger than the cam average torque maximum value in the low rotation range, the hydraulic pressure in the device is reduced due to the small number of advance side hydraulic chambers during intermediate holding control of the valve timing adjustment device Can be prevented, and an increase in rotor deflection during holding control can be prevented.

FIG. 2 is a radial cross-sectional view of the valve timing adjusting device according to the first embodiment. FIG. 2 is a cross-sectional view in the axial direction of the valve timing adjusting device according to the first embodiment. It is explanatory drawing of an average torque and an alternating torque. It is a characteristic view which shows the relationship of the generation | occurrence | production torque with respect to the applied current of OCV (Oil Control Valve).

Hereinafter, in order to explain the present invention in more detail, modes for carrying out the present invention will be described with reference to the accompanying drawings.
Embodiment 1 FIG.
1 and 2 are sectional views in the radial and axial directions of the valve timing adjusting apparatus according to the first embodiment of the present invention. FIG. 1 is a transverse sectional view taken along line AA in FIG. 2 is a longitudinal sectional view taken along line BB in FIG. In the figure, the case 1 has a sprocket portion 2 for transmitting a driving force from a crank (not shown) on the outer periphery, and has shoes 3a to 3d for forming a hydraulic chamber on the inner periphery. In the first embodiment, four hydraulic chambers are formed.

  The rotor 4 divides the four hydraulic chambers formed by the shoes 3a to 3d of the case 1 into the advance side hydraulic chambers 5a to 5d and the retard side hydraulic chambers 6a to 6d, and also serves as a hydraulic pressure receiving portion. 7d is arranged outside at almost 90 ° intervals. The rotor 4 has a boss portion 9 in sliding contact with the inner sliding portion 8 of the case 1 with a predetermined clearance, and has an oil seal and a bearing function. Here, the tips of the shoes 3a to 3d of the case 1 are formed with edges having a circumferential corner of about R0.05. This prevents foreign matter from getting caught in the clearance that is the bearing portion.

  Further, a groove 70 is formed at the tip of the vanes 7a to 7d, and a seal member 10 for restricting the oil flow between the hydraulic chambers is disposed in the groove 70. The rotor 4 is inserted into a camshaft (not shown) inside the boss portion 9 and fastened and fixed with a bolt (not shown). Both ends of the case 1 and the rotor 4 are sealed with a cover 11 and a housing 12, and these are fastened with four bolts 13. Reference numeral 14 denotes a mating surface of the rotor 4 with the camshaft.

  Next, the oil passage formed in the rotor 4 will be described. The boss portion 9 of the rotor 4 has advance angle side passages 17a and 17b and retard angle side passages 18a to 18d that communicate with an oil passage (not shown) formed in the camshaft and are formed to penetrate in the radial direction. The hydraulic fluid is supplied to the hydraulic chambers in communication with the angular hydraulic chambers 5a and 5c and the retarded hydraulic chambers 6a to 6d.

  Here, on the retard side, there are four hydraulic chambers and four supply passages, and the hydraulic pressure is supplied to any of the retard side hydraulic chambers, that is, the number of retard side hydraulic chambers is four. On the other advance side, four hydraulic chambers 5a to 5d are formed, but there are only two supply passages 17a and 17b. That is, the hydraulic oil chambers that are effective because the hydraulic oil is supplied only to the advance side hydraulic chambers 5a and 5c are two. Thus, the number of advance side hydraulic chambers is smaller than the number of retard side hydraulic chambers.

  Further, hydraulic oil is not supplied to the remaining advance-side hydraulic chambers 5b and 5d, and these hydraulic chambers are always opened to the outside by through holes 19 formed in the outer peripheral side wall of the case 1. As a result, oil is not supplied to the bearing portion formed by the inner sliding portion 8 of the case and the boss portion 9 of the rotor adjacent to the advance side hydraulic chambers 5b and 5d that are always open to the outside. Such a problem is concerned. Therefore, an oil groove (not shown) for supplying oil from the advance side hydraulic chambers 5a and 5c to which the hydraulic pressure is supplied to the bearing portion is formed in the housing 12.

  The shoe 3a of the case 1 is formed with a hole 21 penetrating in the radial direction, and is fitted into the fitting hole 22 formed in the boss portion 9 of the rotor 4 so that the rotor 4 is at the starting reference position. A lock pin 23 for restricting at the most advanced position is movably accommodated. The lock pin 23 is urged in a fitting direction by a spring 24, and the spring 24 is held by a stopper 25. Further, the lock pin 23 is applied with a retard side oil pressure by a retard side oil passage 26 opened at the bottom of the fitting hole 22, and is retracted in the radially outward direction against the spring 24 by receiving the pressure at the distal end portion. The restriction of the rotor 4 can be released.

Next, the assist spring 27 for urging the rotor 4 in the advance direction will be described. Grooves 28 and 29 penetrating in the axial direction are formed in the vanes 7a to 7d of the rotor 4 and the shoes 3a to 3d of the case 1, respectively. Resin holders 30 and 31 are formed in the grooves 28 and 29, respectively. Has been inserted. The assist spring 27 is inserted into the bottomed holes 32 and 33 formed on the side surfaces of the holders 30 and 31.
In this way, the assist springs 27 are arranged in the advance side hydraulic chamber (in this embodiment, two in each hydraulic chamber, a total of eight are arranged).

  The torque generated by the assist spring 27 is the smallest advanced angle position, and the cam average torque maximum value in the low rotation range of about 1000 to 1500 rpm (the high-pressure fuel pump that differs depending on the torque of the camshaft, for example, the rotation speed and load). (The total value of the maximum values of the drive torque)). In the same low rotation region and at a high oil temperature of about 120 ° C., the slowest speed that becomes the largest so that it becomes smaller than the retarded-side device generated torque due to the hydraulic pressure when it becomes the smallest (about 50 to 100 kPa). The torque at the angular position is set.

  FIG. 3 shows the torque characteristics acting on the camshaft. The cam torque is mainly determined from the frictional force of the cam surface and the valve spring reaction force, and periodically varies between the retard side and the advance side. Shifting from the camshaft rotation direction to the retard side. This cam torque that varies sequentially is referred to as cam alternating torque, and the average is referred to as cam average torque.

  Next, the operation of the apparatus will be described. First, when the valve timing adjusting device is controlled to the most advanced angle position, which is the reference position, such as when the engine is started or idling, the oil control valve (not shown) is not energized and passes through an engine advance angle side passage (not shown). Oil pressure is supplied to the advance side hydraulic chambers 5a and 5c of the valve timing adjusting device, and the rotor 4 is fixed at the most advanced position. At this time, the lock pin 23 is fitted in the fitting hole 22.

  Next, when a command for retarding operation is issued to the valve timing adjusting device due to an increase in the rotational speed or the like, a predetermined current is applied to the oil control valve, an output port on the retarding side is opened, and an engine delay (not shown) First, oil is supplied to the retarded-side oil passage 26 of the valve timing adjusting device through the corner-side passage and is received by the distal end portion of the lock pin 23, so that the lock pin 23 resists the urging force of the spring 24. It moves to a direction, it escapes from the fitting hole 22, and the restriction | limiting of the rotor 4 is cancelled | released.

  Here, in a state where the lock pin 23 is fitted, the retard side passages 18a to 18d are closed by the shoe portion of the case 1, and no hydraulic pressure is supplied to the retard side hydraulic chambers 6a to 6d. When the lock pin 23 is released, the rotor 4 is shaken by the cam alternating torque, so that the closed retard side passages 18a to 18d are opened and oil is supplied to the retard side hydraulic chambers 6a to 6d. When oil is supplied to the retarded-side hydraulic chambers 6a to 6d, a rotational torque in the retarded direction is generated in the rotor 4 and works against the assist spring torque in the advanced angle direction together with the cam torque in the retarded direction. Begin.

  At this time, the oil filled in the advance side hydraulic chamber on the opposite side passes through the advance side passages 17a and 17b, the in-engine advance side passage, and the oil control valve, and is discharged to a space in the engine at almost atmospheric pressure. Is done. However, since the rotor 4 is operating at a predetermined speed (the oil flow has a predetermined flow velocity), and the oil to be discharged receives the resistance of the passage portion, the advance side on the discharge side Residual pressure remains in the hydraulic chamber (in a normal operation state, a residual pressure of about 30 to 40% of the original pressure is generated).

  Accordingly, during the retard side operation, it is necessary to operate using the advance side hydraulic torque generated by the residual pressure in the advance side hydraulic chamber as a load. Here, in the first embodiment, the number of advance side hydraulic chambers: 2 with respect to the number of retard side hydraulic chambers: 4, and the load resistance due to the residual pressure is also halved. Can be set widely (can be operated from a lower rotational speed region to a higher oil temperature range) and the operating speed can be improved.

  In addition, considering the opposite advance side operation, the residual pressure in the retard side hydraulic chamber is at a normal level, but the number of advance side hydraulic chambers is 2: consumption required for operation per unit angle Since the oil amount is halved, the operating speed can be improved. Although the hydraulic pressure generation torque is reduced because the number of advance side hydraulic chambers is halved, the decrease is compensated for by the assist spring 27 in the advance direction, and there is no influence on the performance.

  As an operation mode of the valve timing adjusting device, there is holding at a predetermined intermediate angle in addition to the above-mentioned retard side operation and advance side operation. This is by applying a predetermined current value calculated by the control unit to the oil control valve to finely adjust the supply flow rate from the oil control valve and optimizing the hydraulic torque on the advance side and retard side. The rotor 4 is held and controlled at a predetermined angle. That is, the cam angle in the retard direction, the assist spring torque in the advance angle, and the hydraulic torque in the advance / retard direction acting on the device are adjusted to be balanced. This state is quantitatively shown in FIG. 4 in relation to the applied current of the oil control valve and the torque generated by the valve timing adjusting device.

In FIG. 4, an intersection P between a curve indicating the retard side and a curve indicating the advance side indicates a point where the retard side hydraulic torque and the advance side hydraulic torque are balanced. In other words, the situation controlled by the current value Ip at the intersection point P is a state where the retard cam torque acting as an external force on the apparatus and the advance assist spring torque are balanced. Here, when cam torque: Tcam, spring torque: Tsp, advance hydraulic torque: Pad, and retard hydraulic torque: Pre, it can be expressed as the following equation (1).
Delay angle side (Tcam + Pre) = Advance angle side (Tsp + Pad) (1)

  The right side (high current side) from this intersection P shows the situation where assist spring torque> cam torque, and the left side (low current side) where assist spring torque <cam torque. In the region on the right side of the intersection point P, when a predetermined torque difference: ΔT is generated, the rotor can be held with a high torque on both the retard side and the advance side. The shake can be suppressed small.

  On the other hand, in the region on the left side of the intersection P, a case is considered where the same torque difference: ΔT (the direction is different from the previous ΔT) is generated. In this case, since the number of advance side hydraulic chambers is 2, the maximum torque on the advance side is ½ of that on the retard side, and both the retard side and the advance side are held with low torque. As a result, the rotor runout when receiving the cam fluctuation torque increases. Increased rotor run-out also affects the opening / closing timing of the exhaust valve, which may affect engine combustion and rotation. In particular, this phenomenon becomes a problem in a low rotation range (1000 to 1500 rpm) where the original pressure of the oil pump is reduced.

  Here, in the first embodiment, since the assist spring torque is set larger than the maximum cam average torque value in the low rotation range, the intermediate holding control is performed only on the right side of the intersection P in the low rotation range. . Therefore, the swing of the rotor can be suppressed by maintaining a high torque on both the advance side and the retard side. Further, although the minimum value of the assist spring torque is set as described above, the maximum value of the retarded-side hydraulic torque generated at the minimum hydraulic pressure (for example, 50 kPa) is ensured from the viewpoint of securing the retarded operation speed (for the normal device size). In this case, it is set smaller than 4 to 5 Nm). Therefore, it is possible to prevent an excessive decrease in the retarded angular velocity due to an excessive spring torque.

As described above, according to the first embodiment, since the number of advance side hydraulic chambers is smaller than the number of retard side hydraulic chambers, the load due to the residual pressure in the advance hydraulic chamber during the retard operation Reduces the resistance and prevents the retarded operating speed from dropping due to the installation of the advance side assist spring, and improves the advanced side operating speed by reducing the amount of oil consumed during the advanced side operation. Can do.
Further, since the assist spring torque is set to be larger than the cam average torque maximum value in the low rotation range, the valve timing adjusting device has an internal holding control during the intermediate holding control. It is possible to prevent a decrease in hydraulic pressure and to prevent an increase in rotor runout during holding control.

  In addition, the torque at the most retarded position of the assist spring is set to be smaller than the retard-side device generated torque due to the oil pressure in the low rotation range, and the device generated torque depends on the oil pressure in the low rotation range and at the high oil temperature. Since the spring torque on the advance side becomes excessive, it is impossible to operate to the retard side when the hydraulic pressure in the low rotation range is low, or the operating speed decreases extremely. Can be prevented. Moreover, the enlargement of the apparatus accompanying the increase in spring torque can be prevented.

  1 case, 2 sprocket, 3a to 3d shoe, 4 rotor, 5a to 5d advanced side hydraulic chamber, 6a to 6d retarded side hydraulic chamber, 7a to 7d vane, 8 inner sliding portion, 9 boss portion, 10 seal member 11 Cover, 12 Housing, 13 Bolt, 17a, 17b Advance side passage, 18a to 18d Delay side passage, 19 Through hole, 21 Through hole, 22 Fitting hole, 23 Lock pin, 24 Spring, 25 Stopper, 26 Delay side oil passage, 27 assist spring, 28, 29 groove, 30, 31 holder.

Claims (3)

A valve timing adjusting device that is attached to an exhaust side camshaft of an internal combustion engine and controls the opening / closing timing of an exhaust valve,
A case having a plurality of shoes forming a plurality of hydraulic chambers on the inner periphery;
A rotor having a vane that divides the plurality of hydraulic chambers into a plurality of advance side hydraulic chambers and a retard side hydraulic chamber;
An assist spring that is disposed between the vane and the shoe and biases the rotor in an advance direction;
The number of advance-side hydraulic chambers that effectively act as the working hydraulic chamber is less than the number of retard-side hydraulic chambers, and the torque of the assist spring is set to be larger than the maximum value of the cam average torque in the low rotation range. Valve timing adjustment device.   2. The valve timing adjusting device according to claim 1, wherein the torque at the most retarded angle position of the assist spring is set smaller than the torque generated by the hydraulic pressure in the low rotation range.   The valve timing adjusting device according to claim 2, wherein the torque generated by the device depends on a hydraulic pressure in a low rotation range and at a high oil temperature.

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