JPS638299B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a timer device for a fuel injection pump.

Generally, in fuel injection pumps for internal combustion engines,
Various timer devices are used to obtain the required injection advance angle, but in the conventional electronic fluid timer device that uses engine lubricating oil as the working fluid, the lubricating oil is used at the time of startup. Since pressure cannot be obtained, it has the disadvantage that a starting advance angle cannot be given. Therefore, as a timer that has improved this drawback, a hydraulic timer having a structure in which an eccentric cam is combined has been used (see, for example, Japanese Patent Application Laid-Open No. 55-5493, Japanese Patent Application Laid-Open No. 55-5494, etc.).

As shown in FIG. 1, this hydraulic timer includes a first eccentric cam 3 that is fitted with a driven side disc 2 that is integrally formed with a driven side shaft 1 or fixed to rotate together with the driven side shaft 1. , and a second eccentric cam 4 that is fitted with the first eccentric cam 3. The assembled state of the driven side disc 2 and these eccentric cams is shown in FIG. As can be seen from FIGS. 1 and 2, the second eccentric cam 4 is engaged with a pin 6 fixed to the drive-side disc 5, while the first eccentric cam 3 is engaged with a piston 7. A pin 8 fixed to is engaged. The piston 7 is housed in a cylinder 9 rotatably attached to the driven shaft 1, and is biased by a spring 10.
The driven shaft 1 is connected to a camshaft 11 of an injection pump (not shown), and pressurized lubricating oil is fed into the hollow part 12 of the driven shaft 1 from a hydraulic device 14 via a pipe 13. It is becoming more and more common. Hydraulic system 14
The lubricating oil 16 in the tank 15 is pressurized by a pump 17 and sent to the pipe 13 through a throttle 19, and the pipe 13 is communicated with the tank 15 through an oil passage 20 having a solenoid valve 18. Therefore,
By adjusting the opening degree of the solenoid valve 18, the pressure within the hollow portion 12 changes. Since the passage 21 that communicates the interior of the cylinder 9 with the hollow part 12 is formed in the driven shaft, the position of the piston can be controlled by controlling the opening degree of the solenoid valve 18. Moreover, when no oil pressure is applied, the position of the piston 7 changes depending on the rotational speed due to its own weight. The driven side disc 2 and the driving side disc 5 are connected via two eccentric cams and two pins as described above, so the movement of the piston 7 causes the pin 6 to move towards the driven side shaft 1. The rotational angle position of the drive-side disc can be controlled, that is, the advance angle can be controlled.

By the way, in this type of timer device, by appropriately adjusting the eccentric position of the eccentric cam,
The advance angle value θ set by this timer in response to a change in the piston stroke 1 of the piston 7 is changed as shown in FIG. 3, thereby providing a starting advance angle θ ₀ . Note that the state of l=0 corresponds to the state of the piston position shown in FIG. However, when the timer is used with the start angle characteristic shown in Fig. 3, there are two piston stroke values that give the same advance value, and the target advance value and the actual advance value are simply different. In conventional solenoid valve control by comparison, when the advance angle value is near zero, if the value of l becomes smaller than the piston stroke value _l1 that gives θ=0 due to torque fluctuation, etc., l=
It had the problem that it converged to 0.

That is, when using a feedback control circuit configured to make the difference between the target advance angle value and the actual advance angle value zero in the range l> _l1 ,
In the range <l ₁ , the slope of the characteristic curve that determines the characteristic between the value of the piston position l and the advance angle value θ is reversed. The range of increase in value is reversed. Therefore, in the above-described control system, if the value of l becomes smaller than l ₁ , a situation will eventually arise in which l=0 is fixed, although not immediately.

Therefore, an object of the present invention is to eliminate the drawbacks of the prior art described above, and to provide a hydraulic system that connects the driven side and the driving side by an eccentric cam assembly and operates with an advance angle characteristic with starting advance angle. It is an object of the present invention to provide a timer device for a fuel injection pump that can stably control a formula timer regardless of the piston stroke value and obtain desired starting advance angle characteristics.

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 4 shows a block diagram of a control system of a timer device according to the present invention. This control device 31
is used in combination with the hydraulic timer shown in FIG. 1, and controls the solenoid valve 18 of the hydraulic timer so as to obtain the advance angle characteristics with starting advance angle shown in FIG. . The control device 31 includes a rotation detector 32 that generates a rotation signal S ₁ related to the rotation speed N of an engine (not shown), and an actual advance angle signal S ₂ that indicates the actual injection advance angle θ _a of the fuel injection pump. The actual advance angle detector 33 outputs the actual advance angle. The rotation signal S ₁ is input to the target advance angle calculator 34, and a target advance angle signal S ₃ indicating the target advance angle θ _b according to the target advance angle characteristics shown in FIG.
is output. The actual advance angle signal S ₂ and the target advance angle signal S ₃ are input to a comparison circuit 35, and a detection signal S ₄ is output. The detection signal S ₄ is "1" when θ _a < θ _b
On the other hand, when θ _a ≧θ _b, the signal is a binary signal that becomes “0” level. The detection signal _S4 is input to the drive circuit 37 via a level conversion circuit 36, which will be described in detail later. The drive circuit 37 includes the solenoid valve 18
A pulse signal for exciting the excitation coil 18a of
This is a circuit that generates _S5 , and the level conversion circuit 36
The duty ratio of the pulse signal _S5 is controlled to change depending on the level of the output signal _{S6 from the pulse signal S6} . In the illustrated example, when the level of the output signal S ₆ is "1", the average opening degree of the solenoid valve 18 (see FIG. 1) is decreased and the value of l is increased. On the other hand, when the level of the output signal _S6 is "0", the value of l becomes small.

As can be seen from Fig. 3, in the timer device shown in Fig. 1, the slope of the characteristic curve is opposite depending on whether the piston stroke l is greater than or less than _l1 . required for,
The relationship between the detection result obtained by the comparator circuit 35 and the opening degree of the solenoid valve 18 is not uniquely determined, but is determined only with reference to the value of l. This control device 31
In order to detect in which part of the characteristic curve shown in FIG.
is equipped with a characteristic determination circuit 38. The characteristic determination circuit 38 is inputted with a memory 39 that stores the actual advance angle signal S ₂ sampled at predetermined time intervals, and the stored content from the memory 39 one sampling time ago and the actual advance angle signal S ₂ . and a comparator 40 for comparing. The comparator 40 always detects whether the actual lead angle value is sequentially increasing or decreasing due to control, and the first discrimination signal _S7 from the comparator 40 containing this detection result has a characteristic It is input to the discriminator 41. On the other hand, the detection signal S ₄ is sampled simultaneously with the sampling of the actual advance angle signal S ₂ , the sampling result is input to another memory 42 , and the stored contents of the memory 42 are read out in synchronization with the read timing in the memory 39 . The signal _S8 is input to the other input of the characteristic discriminator 41. The content read out from the memory 42 is the content of the detection signal S ₄ one sampling ago, and therefore the characteristic discriminator 41 determines which part of the slope of the characteristic curve in FIG. 3 has a positive or negative slope from the contents of the signals S ₇ and S ₈ . You can determine whether it is being used. That is, for example, when the detection signal _S4 is "1" (when the set advance angle is ahead of the actual advance angle), the set advance angle is ahead of the actual advance angle, and the piston stroke l is increased. solenoid valve 18 so that the actual advance angle matches the set advance angle.
It can be seen that l> _l1 if the actual lead angle value advances when the opening degree of is controlled, or if the lead angle value decreases when the detection signal _S4 is "0". Therefore, in this case, the output signal _S9 of the characteristic discrimination circuit 41, which is input as a control signal to the level conversion circuit 36, becomes "0", and the level conversion circuit 36 inverts the level of the detection signal _S4 . without detection signal
_S4 is output as is as output signal _S6 . on the other hand,
When the detection signal _S4 is "0" (when the actual advance angle is ahead of the set advance angle), the piston stroke l
When the opening degree of the solenoid valve 18 is controlled to delay the advance angle so that the actual advance angle coincides with the set advance angle by decreasing the actual advance angle value, if the actual advance angle value has increased, or the detection signal _S4 '' (when the set advance angle is ahead of the actual advance angle), and contrary to the above, if the actual advance value decreases when the piston stroke l is increased, then l < l ₁ . It turns out that there is something. Therefore,
In this case, the output signal S ₉ becomes "1", and the output signal S ₆ becomes "1" regardless of the level of the detection signal S ₄ .
becomes.

According to such a configuration, when the timer device controls the advance angle according to the characteristic curve portion having a positive slope in _FIG . The signal levels are the same. Therefore, when θ _a < θ _b , the level of the detection signal S ₄ and the output signal S ₆ becomes “1”, and the solenoid valve 18
The average opening degree becomes smaller, and the actual advance angle is further advanced and brought closer to the target advance angle value. When θ _a >θ _b , the advance angle becomes small and approaches the target advance angle value, and control is performed so that θ _a =θ _b .

On the other hand, if the timer device operates in a characteristic curve section with a negative slope (l<l ₁ ), then
Regardless of the detection signal, the output signal S ₆ becomes "1", the stroke l increases and finally reaches l=l ₁ , and θ=0. That is, the engine operates in the range 0≦l<l ₁ only after the start until the necessary oil pressure is obtained, and after the oil pressure is obtained, control is performed in the range l ₁ ≦l. Since the time it takes for the stroke to change from l=0 to _l1 after starting changes depending on the oil temperature, the period during which the advance angle is given at starting is automatically adjusted depending on the temperature state of the engine.

In this embodiment, only the rotation signal _S1 is shown as an input signal for obtaining the target advance angle characteristic, but other signals such as load, temperature, etc. can be used as the control signal.

According to the present invention, as described above, the advance angle characteristics of the hydraulic timer can be automatically determined.
Even in the case of having a quadratic advance angle characteristic, stable advance angle control can always be performed.

[Brief explanation of the drawing]

Fig. 1 is a partial cross-sectional schematic diagram of a conventional hydraulic timer device, Fig. 2 is a front view of the driven side disc portion of Fig. 1, and Fig. 3 is the device shown in Fig. 1. 4 is a block diagram of a timer control device according to the present invention, and FIG. 5 is a characteristic diagram showing target advance angle characteristics in the device shown in FIG. 4. 1... Driven side shaft, 2... Driven side disk, 3... First
Eccentric cam, 4... Second eccentric cam, 5... Drive side disc,
6, 8...Pin, 7...Piston, 9...Cylinder, 1
1...Camshaft, 14...Hydraulic device, 18...Solenoid valve, 1
8a... Excitation coil, 31... Control device, 32... Rotation detector, 33... Actual advance angle detector, 34... Target advance angle calculator, 35... Comparison circuit, 36... Level conversion circuit,
37...Drive circuit, 38...Characteristic discrimination circuit, _S1 ...Rotation signal, _S2 ...Actual advance angle signal, _S3 ...Target advance angle signal, _S4 ...
Detection signal, _S5 ...pulse signal, _S6 ...output signal.

Claims (1)

[Claims] 1. In a timer device for a fuel injection pump that has a hydraulic timer that connects the driven side and the drive side by an eccentric cam assembly and operates with an advance angle characteristic with starting advance angle, the actual advance angle and target a comparison means for detecting a difference between the advance angle and the advance angle; a characteristic determination means for determining whether the advance angle characteristic is positive or negative; and a comparison output from the comparison means is inverted in accordance with an output from the characteristic determination means. A timer device for a fuel injection pump, comprising a converting means and a driving means for adjusting the hydraulic pressure of the hydraulic timer so that the difference becomes zero based on the output from the converting means.