JPH026501Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a tape running control device for a video tape recorder (VTR).

(B) Prior Art A general VTR is constructed so that a tape is wound around a cylinder having a rotating head and the tape is run, so that the rotating head can scan diagonal tracks of the tape. This cylinder has a tape guide surface molded into a mirror surface to ensure stable running of the tape, and is made of aluminum material to facilitate this molding. It is widely known that, depending on the environmental conditions in which the VTR is installed, dew condensation may occur on the tape running surface, thereby impeding the stability of tape running. To prevent this, a dew condensation sensor is installed inside the VTR to indirectly grasp the condensation state on the tape guide surface, and the tape running operation can be forcibly stopped when dew condensation occurs, or in addition to this stop, dew condensation can be detected. Measures such as attaching a heater to the cylinder are being taken to quickly release the problem. By the way, if this heater is not installed from the viewpoint of energy saving etc., due to differences in environmental conditions, the condensation sensor may output a signal indicating no condensation even though the condensation condition has not yet been resolved on the guide surface of the cylinder. There are cases where this happens. At this time, when the external controller is operated to command the tape to run, it is executed, but due to the unresolved dew condensation, the tape adheres to the cylinder and is forcibly pulled by the reel motor, causing damage. will receive. If abnormalities in tape running are detected separately and the reel motor drive is controlled, definitive damage to the tape can be prevented, but if the above command is repeated, inappropriate stress will accumulate on the tape and the smooth running of the tape will be prevented. Running performance cannot be guaranteed. on the other hand,
In order to avoid this problem, it is preferable for safety reasons to sufficiently delay the output of the dew condensation sensor to allow time for the tape running surface to dry, regardless of the environmental conditions. Despite the fact that it is available, there is no way to avoid the drawback of not being able to operate it.

(c) Purpose of the invention The present invention was devised in view of the above-mentioned drawbacks, and is an attempt to harmonize the stability of tape running with the operability of a VCR device.

(d) Structure of the invention The present invention uses a dew condensation sensor to indirectly grasp the dew condensation state on the tape guide surface of a cylinder used for tape travel guidance, and controls tape travel in accordance with the output of the dew condensation sensor circuit. Even after the dew condensation sensor circuit output outputs the dew condensation release output, if condensation remains on the running surface and an abnormality in tape running is detected, the command for tape running will no longer be issued. Even if the dew is turned on, it is configured to remain insensitive for a sufficient period of time until the condensation on the running surface is expected to be eliminated.
In other words, if a signal indicating a tape running abnormality is given within a certain period T ₁ after the dew condensation sensor circuit outputs a dew condensation cancellation signal, the tape running by the external controller will be stopped for a certain period T ₂ after that. It is intended to constitute a structure that would effectively prohibit the directives of

(E) Embodiment Figure 1 is a circuit diagram of one embodiment of the device of the present invention.
FIG. 2 is a waveform diagram for explaining the operation of the device.

The device of the present invention includes an external operator 1 that commands tape running, a dew condensation sensor circuit 2 that indirectly identifies the state of condensation on the tape guide surface of a cylinder that guides the tape run, and a A running monitoring circuit 3 that monitors the running state, a tape running controller 4, and a first means 5 that outputs a signal for a certain period of time _T1 after generation of the condensation sensor circuit output.
, a logic circuit 6, and a second means 7 for changing the state for a certain period of time _T2 after receiving the logic circuit output.
and a circuit 8 for applying the output of the second means to an input terminal receiving the output of the dew condensation sensor circuit of the tape running controller.

The external operator 1 is, for example, a play operation command button that is temporarily grounded, and a command signal is applied to the first input terminal 41 of the tape running controller 4 by pressing this operator. The dew condensation sensor circuit 2 includes a dew condensation sensor 21 whose resistance increases when dew condenses, a transistor 22 whose conduction state is controlled by the potential between the terminals of the dew condensation sensor, and a potential (comparison potential) on the output electrode side of this transistor. ) and a potential (reference potential) obtained by dividing the applied power supply voltage by the bleeder resistors 23 and 24 as two inputs, and the voltage comparator output is connected to the second input terminal of the tape running controller 4. 42 and a circuit 26 provided therein. The dew condensation sensor 21 is installed, for example, in a part other than the tape guide surface of a cylinder (not shown), and outputs a dew condensation detection signal (low level) under environmental conditions where dew condensation occurs on the tape scanning surface, and on the other hand, it outputs a dew condensation detection signal (low level) when the dew condensation is removed. A release signal (high level) is output (Q in Figure 2). Since this dew condensation sensor 21 indirectly recognizes the condensation state on the tape running surface, even if the dew condensation sensor 21 outputs a dew condensation release signal, the condensation on the tape running surface is not eliminated yet, and the dew condensation is not eliminated until the dew condensation is eliminated. Period as shown in Figure 2 P
It may be achieved with a delay of T ₀ .

The running monitoring circuit 3 receives a means 31 for detecting the rotational state of the take-up reel (this is well known and will not be described) and a rotation detection signal (the frequency increases as the speed increases) from the detection means, and detects the rotation state when the rotational state is higher than a predetermined frequency. a transistor 32 that becomes conductive, and a charging capacitor 3 that forms a discharge path by this transistor.
3, when the potential between the terminals of the capacitor falls below a predetermined value (during normal running), the capacitor becomes non-conductive,
It also includes a transistor 34 that becomes conductive when the value exceeds a predetermined value (during abnormal running), and a circuit 35 that applies the output of this transistor 34 to the third input terminal 43 of the tape running controller 4.

The tape running controller 4 includes an external operator 1, a condensation sensor circuit 2, a running monitoring circuit 3, and a second means 7.
It is provided with input terminals 41, 42, 43 which receive respective outputs, and when the command from the first input terminal 41 is not input to the second and third input terminals 42, 43 at a low level, the command is sent to the output terminal 44. It provides a signal for tape running. Therefore, this tape running controller 4 validates the command from the external operator 1 when the inputs from the second and third input terminals 42 and 43 are at a high level, and at least when the input from the second input terminal 42 is at a low level. Override the directive.

The first means 5 is a monostable monomultiplier triggered by the rise of the output of the dew condensation sensor circuit 2, and maintains the output terminal at a low level for a period _T1 after the input of the trigger (FIG. 2R). The logic circuit 6 is a NOR gate having two inputs: the output of the first means 5 and the output of the travel monitoring circuit 3, and within the above period _T1 , the external operator 1
When the command _S1 is given and a running abnormality is detected thereafter, an output is transmitted to the second means 7 in response to the fall of the abnormality signal (T in FIG. 2). Second means 7
is a monostable monomultiplier driven by this trigger, and maintains its output terminal at a low level for a period _T2 after the input of this trigger (FIG. 2 U).

The device of the present invention having the above configuration can be used only once within the period T ₁ during which there is a possibility that dew condensation remains on the tape running surface even after the output of the dew condensation sensor circuit 2 generates a signal indicating normality. Only external controller 1
However, at the second time, the command from the external inserter ₁ is ignored within a certain period T2 after the first tape running abnormality is detected. Within the above period _T1 , when the signals Q and T are at high level, the external controller 1
When the command S ₂ is given, the second input terminal 42 of the tape running controller 4 is maintained at a low level by the output of the second means 7 (see FIG. No signal for driving is provided. Note that the output of the second means 7 may be applied to a display means (not shown) to display that the command of the external operator is invalid.

(f) Effects of the invention The device of this invention is capable of operating the external controller for tape running during a certain period of time after the dew condensation sensor circuit detects the removal of condensation, that is, during a period when there is a possibility that dew condensation may remain on the tape guide surface of the cylinder. Since the system is configured so that a command is accepted only once, but not for a predetermined period from the second time onwards, repetition of running abnormalities due to condensation on the tape running surface of the cylinder can be prevented and the tape can be protected. can. In addition, since the dew condensation sensor circuit output is not uniformly delayed, when the condensation on the running surface has been removed, operations using external controls can be executed immediately, which may impair operability. There is no.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of one embodiment of the device of the present invention;
FIG. 2 is a waveform diagram for explaining the operation of the device. Explanation of main figure numbers, 1... External operator, 2... Condensation sensor circuit, 3... Running monitoring circuit, 4... Tape running controller, 5, 7... First and second means, 6... Logic circuit, 8...Giving circuit.

Claims (1)

[Scope of utility model registration request] An external operator that commands tape running, a dew condensation sensor circuit that indirectly identifies the state of condensation on the tape guide surface of a cylinder that guides the tape run, and a running sensor that monitors the running state of the tape that passes through the tape guide surface. A monitoring circuit receives each output of the external operator, the condensation sensor circuit, and the running monitoring circuit, and when the condensation sensor circuit output is not present, it accepts a command from the external operator, and when the condensation sensor circuit output is present. a tape running controller that prohibits commands from the external operator; and a first means that responds to a change in the state of the dew condensation sensor circuit output from presence to absence and changes the state for a certain period of time _T1 thereafter;
a logic circuit that receives the output of the first means and the output of the driving monitoring circuit and outputs an output when the output of the driving monitoring circuit exhibits an output indicating a driving abnormality during the certain period of time; A tape running state control device for a VTR, comprising a second means for changing the state of _T2 for a certain period of time, and a circuit for applying the output of the second means to an input end receiving the output of the dew condensation sensor circuit of the tape running controller. .