润涛阎回复评论:
1。 关于刹车产生热量而不能踩刹车:任何车,在上市前必须通过刹车试验,就是在100迈的速度直接刹到0,刹车系统不会因为过热而失效。否则,不能上市。现在,由于刹车皮是陶瓷的,130迈刹到停车,不会有问题。
2。有一位网友问及为何油门最大时,真空为零。在动力刹车系统里装上power brake vaccum reservior.就是把真空储藏起来的作用。这个储藏器是密封的,当早上你不打火,踩刹车,照样轻松踩下去,就是因为这个真空储藏器的真空可以利用。但你松开后再踩,就踩不下去了,因为真空用完了。
在高速路上,你即使把油门踩到最大,没有了真空,因为有真空储藏,你刹车没问题。因为油门和刹车是用同一只脚,当你离开油门去踩刹车,油门就减小了,真空立刻恢复。这样,即使你松开刹车,再踩,真空也没问题了。但对丰田有问题,因为油门在高处卡住回不来了,真空不能恢复,所以,踩刹车不能松开。一旦松开,刹车因为没有了真空,就真的失灵了。
下面是英文报道的详细油门踏板改装步骤。大家可以看看。
The CTS pedal has a friction arm that is designed to generate a certain degree of friction necessary for the proper functioning of the electronic gas pedal. In our earlier tear down and analysis, we pointed out that the CTS design is inferior to others, such as the Denso unit also used in Toyotas. The friction arm is subject to wear and contamination that increases friction to the point of creating a sticky gas pedal.
The friction arm is a pivoted fulcrum; the end with the “friction teeth” rides in two grooved channels in the pedal assembly. Both these parts are made from plastic. The other end of the friction arm is held in place by the return spring, which exerts the pressure necessary to generate the friction. As the friction teeth wear, the gap on the other end increases in relation to the housing. Toyota’s shim is inserted in this gap in order to reduce/limit the amount of friction, and to compensate for wear.
The gap is to be measured by a feeler gauge (photo above), which determines the thickness of shim that is then inserted in the gap. The shim then limits the travel of the fulctum on the spring end, thereby reducing the amount of friction on the teeth as they ride in the grooves.
The next step is to open the gap by inserting a narrow-shank screwdriver, so that the correctly-sized shim can be installed. The unit has been turned upside down to facilitate that.
The shim (gray steel) is now slid in, and positioned behind a lip that serves to retain it. The shim is kept in place by the pressure of the return spring on the fulcrum, but we wonder whether a strong jolt might not be able to dislodge it. If it did become dislodged, it could potentially cause serious problems. No one would ever design a unit like this with a loose metal shim that was held in place by spring pressure only.
The next picture shows the shim all the way in place behind the lip. It’s a good thing that lip exists, otherwise this fix would not be possible.
The photo above shows the inside of the unit, with the friction arm extending forward. The shim is clearly visible as the shiny gray rectangle. The pivot axles extending out on both sides of the fulcrum/friction arm are visible as two small white/gray pieces, just below and to both sides of the shim. The friction teeth are visible towards the front of the unit, riding (now higher) in their grooves.
This photo above was taken previously of the same pedal. It’s difficult to tell exactly from the slightly different angles whether the teeth are riding higher with the shim, but it does appear so. And a subjective impression was that the pedal had somewhat less friction. So the fix may well reduce the friction below a dangerous level, but for how long?
The only way we interpret the necessity of measuring the friction arm gap and choosing an appropriately sized shim is that the older units with more wear will have a smaller gap than the new(er) ones. The shim will compensate for that wear, but in a static, not dynamic way. As soon as the continued wear on the friction arm changes its size or other friction characteristics, the pedal is potentially back to the same sticky situation as before.
The shim’s effect on reducing the amount of friction will presumably slow down the wear process, but intrinsically, this is not a permanent fix to a very critical part, from a safety point of view. This is why the CTS-type pedal design is flawed, because it is subject to changes in the amount of friction it generates due to wear and other factors.
The only other explanation for the varying gap size and different shims is that the manufacturing tolerances are so great, that this is necessary to compensate for them. That’s that hard to imagine, for such a critical part. But if so, it raises other serious questions about this unit. Either way, it reinforces our position that Toyota needs to replace all the CTS pedals with Denso pedals or another proven pedal design, as soon as they are available. The shim fix is a Band Aid, and does not inspire the confidence that Toyota urgently needs to instill in its customers and the market place at this critical time.
Update: Given that Toyota has acknowledged that these pedal assemblies cost them $15, it would obviously be cheaper (and more reliable) to swap out the CTS units with the Denso unit rather than this fussier and riskier fix. The problem is time; it could take many months if not a year or more to change tooling and produce 2.3 million units. Meanwhile, making these shims was obviously something that a stamping manufacturer could do in days. |