JPH058381Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a solenoid valve used in a hydraulic pressure control device for an automatic transmission, and particularly to a drive circuit for a solenoid valve that is continuously turned on and off by pulsed current.

BACKGROUND ART Conventionally, a hydraulic pressure control device for an automatic transmission has a method of opening and closing a hydraulic circuit to the drain side when performing hydraulic pressure control, as shown in Japanese Patent Laid-Open No. 58-46258, for example. Some vehicles are equipped with a solenoid valve that is continuously driven on and off by pulsed current to generate control hydraulic pressure downstream of the solenoid valve in accordance with vehicle running conditions.

Incidentally, in recent years, as a drive circuit for the solenoid valve, a first pulse current source 1 and a second pulse current source 3 having a current limiting resistor 2 are provided as shown in FIG. The pulse current waveform generated by the second pulse current source 3 (see FIG. 7A) and the pulse current waveform generated by the second pulse current source 3 (see FIG. 7A)
(see Figure B), a pulse current waveform having an overexcitation component M ₁ and a rated excitation component M ₂ as shown in Figure 7C is created, and this combined pulse current drives the solenoid 4 of the solenoid valve. It has been proposed to do so. That is, although not shown, the solenoid valve has a plunger operated by the solenoid 4, and this plunger is biased by a spring in a direction opposite to the direction of operation when the solenoid 4 is energized. ing. Therefore, when the solenoid 4 is energized, the plunger needs to move against the urging force of the spring, and the overexcitation of the pulse current is sufficient to suppress the pressing force against the spring when the plunger is initially activated. By compensating and increasing the responsiveness of the solenoid valve, precise hydraulic pressure control can be performed.

By the way, such a solenoid valve drive circuit includes a first pulse current source 1 and a first transistor.
T _r1 , a second transistor for the second pulse current source 3
By inputting _a pulse voltage supplied from a controller not shown as _{the base voltage of the first and second transistors T r2 and}
Pulse currents shown in Figures A and B are generated. Therefore, in order to detect a failure of the first and second transistors T _r1 and T _r2 , a monitor circuit 5 for detecting the terminal voltage of the solenoid 4 is provided. This monitor circuit 5 compares the terminal voltage of the solenoid 4 with a predetermined value and determines whether it is at H level or L level.
Outputs a level signal. Therefore, by comparing the on/off state of the control signal of each transistor T _r1 and T _r2 with the signal of the monitor circuit 5, a failure of the transistor T _r1 and T _r2 can be detected.

Problems to be Solved by the Invention However, in the conventional solenoid drive circuit, when both ends of the current limiting resistor 2 are shorted due to dielectric breakdown or the like, the second pulse current source 3
The function to limit the current value supplied from the device is lost. Then, the pulse current supplied to the solenoid 4 is transferred to the second pulse current source 3 as shown in FIG.
The current value of the rated excitation portion M ₂ created by the current value becomes high, and the solenoid 4 is always driven in an overexcited state. Therefore, the solenoid 4
The heat generation effect of the solenoid valve increases, reducing the durability of the solenoid valve, and sometimes causing the solenoid valve to burn out.

Also, even in the case where the monitor circuit 5 is provided, when both ends of the current limiting resistor 2 are shorted, the monitor circuit 5 outputs an H level,
Since the L level signal has a form that is no different from that in a normal state, the abnormality cannot be detected.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to prevent overcurrent from flowing when the current limiting resistor is shorted, and at the same time to enable a monitor circuit to detect the abnormality.

Means for Solving the Problems In order to achieve the above object, the present invention provides a first pulse current source using a transistor operated by a control signal, a first pulse current source using a transistor also operated by a control signal, and a current limiting source using a transistor operated by a control signal. a second pulsed current source having a resistance;
In a solenoid drive circuit of an automatic transmission hydraulic pressure control device that supplies a solenoid valve with a pulse current having an overexcitation component and a rated excitation component as the sum of each pulse current generated by the second pulse current source, the second pulse current source The current source is provided with a current-limiting overload protection circuit or a current-blocking overload protection circuit with negative characteristics that regulates the base current of the transistor when the current of the transistor increases, and the terminal voltage of the solenoid is compared with a predetermined value. The present invention is characterized in that a monitor circuit is provided to detect an abnormality in the current limiting resistor from the voltage drop.

Effect With the above configuration, in the present invention, when the current limiting resistor is shorted due to dielectric breakdown or the like, a current of a predetermined value or more is conducted to the transistor of the second pulse current source. Then, the overload protection circuit provided in the second pulse current source reduces the base current of the transistor according to its negative characteristic, and limits the current flowing through the transistor.
Alternatively, the base voltage is lowered to cut off the current flowing through the transistor. Therefore, the terminal voltage of the solenoid becomes low, and the output of the monitor circuit is always L.
level. This makes it possible to detect an abnormality due to shorting of the current limiting resistor.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 shows a solenoid valve 12 of an automatic transmission hydraulic control device 10 used in the drive circuit of the present invention.
shows. This solenoid valve 12 is used for regulating line pressure. The solenoid valve 12 is composed of a solenoid 12a, a plunger 12b and a spring 12c.
When the solenoid 2a is energized, the plunger 12b moves downward in the figure against the biasing force of the spring 12c to connect the hydraulic circuit 14 to the drain port 12d, and when the solenoid 12a is demagnetized, the plunger 12b
b is pressed by the spring 12c to close the drain port 12d. The solenoid valve 12 is driven via a solenoid drive circuit 20, which will be described later, according to vehicle running conditions, such as throttle opening.
A signal pressure as control hydraulic pressure is generated from the pilot pressure in the hydraulic pressure circuit 14 downstream of the orifice 14a. Then, the pressure modifier valve 16 is operated by this signal pressure, a modifier pressure is generated in the circuit 16a from the pilot pressure, and the pressure regulator valve 18 is operated by this modifier pressure. The line pressure of the circuit 18a is regulated.

FIG. 2 shows a solenoid drive circuit 20 for driving the solenoid valve 12, and this solenoid drive circuit 20 includes a first pulse current source 22
and a second pulse current source 24. The first pulse current source 22 has a first transistor T _r1 whose base voltage is a pulse voltage output from a controller (not shown), and when this first transistor T _r1 is turned on, the power supply voltage V ₁ increases It is designed to be supplied to the solenoid 12a of the solenoid valve 12. Therefore, the pulse current shown in FIG. 7A is supplied to the solenoid 12a in response to the pulse voltage input to the base of the first transistor T _r1 .

On the other hand, the second pulse current source 24 is a second transistor whose base voltage is the pulse voltage output from the controller, similar to the first pulse current source 22.
When this second transistor T _r2 is turned on, _the power supply voltage V ₂ (in this example,
V ₁ =V ₂ ) is supplied to the solenoid 12a via the current limiting resistor 26 as a pulse current shown in FIG. 7B.

Therefore, the pulse currents supplied from the first and second pulse current sources 22 and 24 are combined in the solenoid 12a, and as shown in FIG. 7C, a pulse current having an overexcitation component and a rated excitation component is generated. It is designed to be supplied to the solenoid 12a as the same.

28 is a comparator 2 that detects the terminal voltage of the solenoid 12a and compares it with a predetermined reference voltage.
8a, this monitor circuit 28
The output is set to be high (H) level when the terminal voltage input to is equal to or higher than the reference voltage, and is set to be low (L) level when it is equal to or lower than the reference voltage. Note that the resistor r _n connected to this monitor circuit 28 has a sufficiently large value.

Here, in this embodiment, a current limiting type overload protection circuit 30 having a substantially F-shaped negative characteristic as shown in _{FIG .} , 32 are provided, respectively. Both protection circuits 30 and 32 have substantially the same configuration, and include a resistor r _s that detects the magnitude of the current I _O flowing through the transistors T _r1 and T _r2 , and a predetermined current shown in FIG.
Transistor for limiting current in I _OM
T ₁ , a transistor T ₂ for reducing the current to the I _SO point shown in FIG. 3 when a larger current is about to flow, and these transistors T ₁ ,
It is configured to include resistors r ₁ to _{r 7} for appropriately operating T ₂ .

Therefore, in the configuration of the above embodiment, when the current limiting resistor 26 is shorted, a current of more than a predetermined value attempts to flow through the second transistor T _r2 of the second pulse current source 24, but the overload protection circuit The action of 32 reliably prevents overcurrent. Therefore, it is possible to prevent burnout of the second transistor T _r2 , burnout of the solenoid 12a, or decrease in durability.

Specifically, when the current limiting resistor 26 is shorted and an excessive current flows through the resistor _rs , the voltage at the point decreases and the transistor _T1 starts to turn on. Then, the potential at the point increases and the second transistor T _r2
Since the base-to-emitter voltage V _be decreases,
The current flowing through the second transistor T _r2 is limited. Therefore, the voltage is balanced at the limit voltage at which the transistor _T1 turns on. This determines the I _OM point in Figure 3. Furthermore, if the resistance value of the current limiting resistor 26 is extremely reduced, the potential at the point will be lower than the potential at the point. This potential difference causes the transistor
When the voltage between base and emitter V _be required for T ₂ to turn on becomes larger, the transistor T ₂ turns on.
Turn on. Then the potential at the point decreases further and the current flowing through the transistor T ₁ increases, resulting in
Voltage between base and emitter of second transistor T _r2
V _be further decreases. Therefore, the second transistor
The current flowing through T _r2 decreases and decreases towards a predetermined I _sp as shown in FIG.

Therefore, due to the current limiting action in accordance with the negative characteristics of the overload protection circuit 32, when the current limiting resistor 26 is shorted, the second transistor
At the same time that the current flowing through T _r2 is greatly limited,
The potential at the point decreases. Therefore, solenoid 1
The terminal voltage of 2a decreases, and the output of the monitor circuit 28 becomes L level. In other words, the output of the monitor circuit 28 remains at the L level continuously regardless of whether the pulse signal output from the controller (not shown) is on or off, and therefore, based on this, it can be determined that the current limiting resistor 26 is shorted. Incidentally, when an abnormality in the current limiting resistor 26 is detected in this way, by promptly replacing the current limiting resistor 26, it is possible to prevent burnout of the solenoid valve 12a and to maintain the original target. This makes it possible to perform signal pressure control as well as line pressure control, thereby reducing shift shock.

Note that the protection circuit 3 provided in the first pulse current source 22
0 also exerts a similar current limiting effect on the overcurrent of the first transistor T _r1 . In other words, solenoid 1
When transistor 2a is shot, the first and second transistors T _r1 and T _r1 are prevented from being burnt out.

FIG. 4 shows another example of the solenoid valve 42, in which the solenoid valve 42 according to the present invention is installed in the hydraulic control circuit 10a that operates the overrun clutch 40 as a frictional engagement element for engine braking that is engaged during engine braking. It was established.

That is, in the figure, 44 is a shuttle valve, and 46 is an overrun clutch control valve.The shuttle valve 44 is designed to be switched by the line pressure supplied from the circuit 44a, and when the line pressure is above a predetermined pressure, the spool is closed. 44b is in the right half position in the figure (hereinafter referred to as the right position), and the pilot pressure supplied via the circuit 44c is directly supplied from the circuit 46a to the overrun clutch control valve 46.
The spool 46b of No. 6 is set to the right position. On the other hand, when the line pressure is below a predetermined pressure, the spool 44b of the shuttle valve 44 is at the left half position in the figure (hereinafter referred to as the left position), and the circuit 4
4c and the solenoid valve 42.
The control pressure created using the pilot pressure as the source pressure is supplied to the overrun clutch control valve 46 via a circuit 44d and a circuit 46a. The solenoid valve 42 has a solenoid 42a, a plunger 42b, and a spring 4, similar to that shown in FIG.
2c and a drain port 42d, and the same solenoid drive circuit as in FIG. 2 is used, and the solenoid 42
The control pressure is created by continuous on/off driving of a.

Then, the overrun clutch control valve 46 is in the left position, so that the circuit 46c
line pressure is supplied to the overrun clutch 40, and the overrun clutch 40 is engaged to set the engine braking state. On the other hand, when the overrun clutch control valve 46 is in the right position, the circuit 46c
The overrun clutch 40 is communicated with the drain port 46d by blocking the overrun clutch 4.
0 is now released.

Therefore, this embodiment also exhibits the same functions as the embodiments shown in FIGS. 1 and 2, and can monitor abnormalities due to overexcitation of the solenoid valve 42.

In addition, in the embodiment described above, the first pulse current source 2
2 and the second pulse current source 24 are respectively provided with protection circuits 30 and 32 having negative characteristics.
Second transistor T _r1 , T _r2 and solenoid 1
2a and 42a, but the present invention is not limited to this, and it is sufficient to provide the protection circuit 32 at least on the second pulse current source 24 side.

Next, FIG. 5 shows an embodiment in which a current cut-off type overload protection circuit (current cut circuit) 50 is provided as an overload protection circuit for the second pulse current source 24, which cuts off the current when an overcurrent is detected. It shows. In this embodiment, when both ends of the current limiting resistor _R1 are shorted, the potential at point A increases, so this is detected by the comparator and the second transistor T _r2
The second transistor T r2 is turned off by increasing the potential on the base side of the second transistor T _r2 to cut off the current.

Furthermore, when the next pulse of the pulse signal (drive signal) output from the controller is input,
2nd transistor for a short time by monomulti 52
Every time T _r2 is turned on, the current limiting resistor _R1 is checked for abnormalities. When _R1 is normal, transistor T _r2 is
While T r2 is on, the transistor T _r2 is turned on due to a normal signal from the comparator. This makes it possible to deal with erroneous judgments of abnormality detection and cases where the shot state returns to normal.

Effects of the invention As is clear from the above explanation, in the solenoid drive circuit of the invention, when the current limiting resistor of the second pulse current source is shorted, the overload protection circuit prevents the second pulse current source from switching off. No overcurrent flows through the transistor or solenoid, preventing burnout of the transistor, burnout of the solenoid, or reduction in durability.

Utilizing the current limitation by the overload protection circuit, the monitor circuit can detect an abnormality, and a short circuit of the current limiting resistor can be immediately detected.

[Brief explanation of the drawing]

Fig. 1 is a main part configuration diagram showing an example of a hydraulic control circuit to which the present invention is applied, Fig. 2 is a circuit diagram showing an embodiment of the solenoid drive circuit of the present invention, and Fig. 3 is a circuit diagram showing an example of the solenoid drive circuit of the present invention. A characteristic diagram of the protection circuit used, FIG. 4 is a main part configuration diagram showing another example of the hydraulic pressure control circuit, FIG. 5 is a circuit diagram showing another example of the solenoid drive circuit of the present invention, and FIG. 6 is a configuration diagram of a conventional solenoid drive circuit, Figures 7A, B, and C are explanatory diagrams of each pulse current waveform obtained in the solenoid drive circuit, and Figure 8 is a pulse current output when a conventional current control resistor is abnormal. It is an explanatory diagram of a waveform. 10, 10a...hydraulic pressure control circuit, 12, 42...
... Solenoid valve, 12a, 42a... Solenoid, 20... Solenoid drive circuit, 22... First pulse current source, 24... Second pulse current source, 2
6... Current limiting resistor, 28... Monitor circuit, 3
0,32...Protection circuit.

Claims (1)

[Claims for Utility Model Registration] A first pulse current source using a transistor operated by a control signal, and a second pulse current source using a transistor also operated by a control signal and having a current limiting resistor. , a solenoid drive circuit of a hydraulic pressure control device for an automatic transmission that supplies a solenoid valve with a pulse current having an overexcitation component and a rated excitation component as the sum of each pulse current generated by the first and second pulse current sources. The second pulse current source is provided with a current-limiting overload protection circuit or a current-blocking overload protection circuit with a negative characteristic that regulates the base current of the transistor when the current of the transistor increases, and the terminal of the solenoid Compare the voltage with a predetermined value,
A solenoid drive circuit for a hydraulic pressure control device for an automatic transmission, characterized in that a monitor circuit is provided for detecting an abnormality in the current limiting resistor from the voltage drop.